Chapter 62. Anesthesia for Obstetric Care and Gynecologic Surgery

1. The use of epidural, spinal, combined spinal–epidural, and dural-puncture epidural techniques for obstetric care has increased dramatically because of the quality and safety of the analgesia and anesthesia produced, the ability to titrate the degree and duration of pain relief, and the expanding number of situations for which their use is appropriate.

2. Labor analgesia and obstetric anesthesia can have beneficial effects on the outcomes of external cephalic version, in utero fetal and placental surgery, and parturients with significant comorbid conditions.

3. Major fetal organogenesis occurs during weeks 3 to 10 of gestation. Teratogenicity is difficult to evaluate in prospective clinical trials because of the low incidence of occurrence and the number of confounding factors, but the list of proven human teratogens does not include the anesthetics commonly used in clinical practice.

4. Although important reductions in anesthesia-related maternal mortality have occurred in the past 5 decades, a greater risk (1.7 times) of maternal death is still witnessed with the use of general versus regional anesthesia. This finding can be partially explained by changes in the airway that occur over the course of pregnancy. Promotion of neuraxial techniques, skill with alternate airway devices, and review of difficult airway algorithms are strongly encouraged.

5. Antenatal and postpartum maternal hemorrhage can be masked until significant blood loss has occurred, but a cogent plan for diagnosis and response can significantly affect the outcome. Interventional radiologists may place occlusion balloons within the uterine or hypogastric arteries in high-risk parturients to allow timely control of bleeding.

6. Preeclampsia is a multisystem disease that raises numerous concerns for anesthesia care, but neuraxial techniques remain the preferred option unless contraindicated by coagulations disorders, severe hypovolemia, or patient preference.

7. Anesthetic care for gynecologic surgery requires an understanding of gender-related differences in physiology, including sensitivity to pain, and pharmacodynamics, including responses to anesthetic drugs; such differences ultimately may affect patient outcomes and satisfaction.

8. Both obstetric and gynecologic surgery involve positions, techniques, and organ systems that require special vigilance. The uterus and other female viscera are highly vascular. Blood loss can be sudden and profuse; air emboli can occur unexpectedly (especially in the Trendelenburg position); and in pregnancy-related procedures, amniotic fluid emboli can occur without provocation.

9. Hysteroscopic and laparoscopic procedures can result in significant adverse outcomes from absorption of carbon dioxide (CO2) or the distending medium. CO2 insufflation of the abdomen or pelvis may cause a number of disturbances in cardiac and respiratory physiology, which can be minimized if anticipated.

10. The Trendelenburg lithotomy position, which is commonly used for gynecologic procedures, may lead to a number of peripheral nerve injuries. Excessive hip flexion, abduction, and external rotation may cause femoral nerve, obturator, lateral femoral cutaneous, sciatic, and peroneal nerve injuries. Attention to positioning throughout the procedure, use of protective padding, and avoidance of contact with hard surfaces or supports are important elements of optimal care.

Just a few months separated the introduction of anesthetics for general surgical procedures and obstetric care. Ether, then believed to be the panacea to "cure all ills," was found to be efficacious but not optimal in both environments. Today, although the use of general volatile anesthetics remains popular, the advent of regional anesthetic techniques has greatly expanded the ability to provide analgesia and anesthesia for a wide spectrum of procedures and conditions. Selection of the optimal anesthetic technique for obstetric and gynecologic patients should consider the significant anatomic, hormonal, and physiologic adaptations that ultimately allow a female to conceive and carry a pregnancy. This chapter discusses the provision of analgesia and anesthesia for obstetric care and gynecologic surgery. Emphasis is placed on the three primary settings of care: provision of analgesia for labor and delivery, anesthesia for obstetric and nonobstetric surgery during pregnancy, and anesthesia for gynecologic surgery.

With the application of diethyl ether to aid in a vaginal delivery in 1847, James Young Simpson, an obstetrician, ushered in the use of anesthetics for obstetrics. The next half century was associated with increased acceptance and evolution of anesthetic drugs and techniques for labor and delivery. Regional anesthetic techniques, which deliver pain relief to a discrete region of the body, were introduced to obstetrics in 1900, when Oskar Kreis described the use of spinal anesthesia. Since that time, central neuraxial techniques have evolved from single, limited-duration injections into the intrathecal (subarachnoid) space to titratable, controlled infusions through flexible catheters most commonly placed into the epidural space. These techniques are often the optimal method for providing analgesia for labor, anesthesia for obstetric or nonobstetric surgery during pregnancy, and analgesia for postoperative care. Because these techniques are so fundamental to the practice of anesthesia for parturients, they are discussed initially and then the rationale and details for their use are expanded throughout the chapter.

Neuraxial Techniques

Regardless of which neuraxial technique is used for labor, delivery, or nonobstetric operations, a standardized approach is warranted. A preprocedure history and physical examination with notation of allergies; baseline vital signs; and assessment of the airway, body habitus, and hematologic system (eg, preeclampsia-induced thrombocytopenia; see Hypertensive Disorders of Pregnancy below and Chapter 21) are mandatory, even if the situation is urgent. An intravenous (IV) catheter and fluid administration should be started, especially because hypotension can abruptly follow neuraxial technique placement and affect both maternal and fetal welfare. Whether crystalloid or colloid solutions are administered to minimize hypotension is controversial. Colloids have been observed to minimize but not eliminate hypotension but can be associated with increased costs, risk of allergies, and coagulation disorders (when given in large doses eg, hetastarch in doses >20 mL/kg). IV fluids, regardless of the amount administered, do not reliably minimize hypotension. Thus, in urgent situations, waiting for an arbitrary amount of fluid to be infused before the neuraxial anesthesia or analgesia is not necessary. The seated position is often selected for the purportedly enhanced ability to palpate the vertebral spinous processes and identify the midline plane. However, these landmarks can also be achieved in the lateral recumbent position. In addition, in pregnant patients, the lateral recumbent position has the particular advantage of minimizing venous plexus engorgement, resulting in reductions in vessel trauma, vessel cannulation, and placement attempts.1 In certain emergent situations, such as umbilical cord prolapse or fetal head entrapment, the seated position is not a viable option. As such, a general anesthetic would be the only available method for delivering anesthesia if the anesthesiologist is not comfortable instrumenting the back in the lateral position.

Selection of the optimal neuraxial technique depends principally on the desired onset, reliability, and titratability of the resulting analgesia or anesthesia, with catheter-based techniques offering the greatest flexibility. The spinal technique offers confirmation of the space via cerebrospinal fluid (CSF) flow, fast onset, and very reliable sensory and motor blockade; however, the duration of blockade is time limited and may be associated with abrupt hemodynamic alterations. By contrast, the epidural technique has a slower onset; does not intentionally create a dural puncture; and when used with a catheter, offers an almost unlimited duration of blockade; however, the resulting block may be patchy or one sided, and a large dural puncture may occur inadvertently. The dose, onset, and duration of various local anesthetics for epidural labor analgesia and anesthesia are well characterized (Table 62-1). The epidural technique may enable a lesser incidence and extent of maternal hypotension because of the ability to administer the dose of local anesthetic in a fractionated manner and allow compensatory cardiovascular mechanisms to respond to the more slowly developing sympathetic blockade. The combined spinal–epidural (CSE) technique, which consists of epidural needle placement, administration of subarachnoid medications via a spinal needle placed through the shaft of the epidural needle, and placement of an epidural catheter (Fig. 62-1),2 appears to combine the best of both techniques with a blockade that is rapid in onset, is reliable, and can be prolonged. A variation of the CSE technique is the dural puncture epidural (DPE) technique, which includes all of the same steps except for the omission of direct medication dosing through the spinal needle. Instead, all medications are dosed into the epidural space, which allows transit through the dural puncture and provides faster onset and an improved sacral and bilateral blockade compared with a standard epidural technique.3 With the CSE and DPE techniques, the spinal needle emerges 10 to 15 mm beyond the tip of the epidural needle,2 the presence of CSF can confirm that the epidural needle is proximal to or in the epidural space. This information can be of value when multiple "losses of resistance" are encountered during epidural needle placement.

Intentional puncture of the dural ligament with an epidural needle and placement of a catheter into the subarachnoid space, called a "spinal catheter technique," is a viable option. Spinal catheter techniques have the benefit of CSF confirmation and the ability to provide a highly reliable and titratable blockade.4 Such techniques are often used in parturients who are morbidly obese, in those with significant cardiac disease, and after an unintentional dural puncture with an attempted epidural catheter placement. Because placement of a spinal catheter depends on use of epidural equipment (eg, 17-gauge Tuohy needle and 20-gauge catheter), a significant postdural puncture headache risk exists. Smaller needles and catheters for labor and delivery are currently being used or evaluated in Europe and the United States, respectively, with the hope of avoiding the cauda equina syndrome observed during the earlier microcatheter trials. This complication most likely resulted from pooling of excessive amounts of local anesthetics.5,6

Use of epidural, spinal, and CSE techniques has increased dramatically, particularly for obstetric indications (Fig. 62-2). This increase has been driven in large part by the quality and safety of the analgesia and anesthesia produced, the ability to dictate the intensity and duration of pain relief as required by the circumstances, and an expanding number of situations in which their use is appropriate. Use of neuraxial opioids results in improved analgesia compared with IV opioid administration, likely because of actions on both supraspinal and spinal opioid receptors (Table 62-2).7 Currently, in developed countries, central neuraxial techniques provide labor analgesia for 30% to 50% of all parturients and the anesthesia for the majority of instrumental and operative deliveries.8,9

Considerations on Maternally Administered Anesthetics

Although only a limited percentage of systemically or neuraxially administered anesthetics eventually reaches the fetus (see Chapter 21), an overlying concern during assisted reproductive technologies and pregnancy is the effect on fertilization and embryonic and fetal development. Teratogenicity, defined as any significant postnatal change in function or form in an offspring after prenatal treatment, is difficult to evaluate in prospective clinical trials given the low incidence of occurrence and the number of confounding factors; species susceptibility, genetic predisposition, and amount, timing, and duration of exposure all can affect reproductive outcome. The criteria for identifying an agent as a human teratogen require (1) proven exposure to the agent at the critical time of development; (2) consistent findings in two or more high-quality epidemiologic studies; (3) careful delineation of the clinical cases, ideally with identification of a specific defect or syndrome; and (4) an association that makes "biologic sense."10 Of note, the list of agents or factors proven to be human teratogens does not include anesthetic agents used routinely in clinical practice (Box 62-1); however, readers are encouraged to refer to package inserts provided by drug manufacturers and standard teratology reference sources for more specific information.10,11 The effect of anesthetics on early cellular division has been reviewed extensively.12

Early studies of neurotropic agents (eg, opioids, tricyclic antidepressants, phenothiazines, benzodiazepines, butyrophenones) demonstrated significant teratogenicity in rodents. Subsequent studies, however, questioned the relationship given the high doses of drugs administered and the resulting respiratory depression and impaired feeding. Using more elegant study designs at clinically relevant doses, often provided with chronically implanted osmotic minipumps, the absence of teratogenicity in the agents commonly used for induction (barbiturates, propofol, ketamine, benzodiazepines), analgesia (opioids), and muscle relaxation has been confirmed.10,13-15 With the exception of the association of chronic cocaine exposure with congenital defects and adverse reproductive outcomes, local anesthetics per se are devoid of teratogenic effects in clinically used doses.10,16 As described in section Considerations on Maternal Physiology, however, uncorrected maternal hypotension that may result from local anesthetics provided via neuraxial techniques may lead to decreased fetal perfusion, fetal acidosis, and fetal death. The effects of volatile agents demonstrate the importance of timing; exposure to nitrous oxide and halogenated agents during in vitro oocyte fertilization causes delays in division from the one- to two-cell stage and impaired spindle cell function during meiosis, respectively. In vivo, mice and rats exposed during pregnancy to 50% or 0.75 minimum alveolar concentration (MAC) halothane, isoflurane, or enflurane at various stages of pregnancy have resulted in increased fetal resorptions and altered body laterality with nitrous oxide but no teratogenic effects with the halogenated agents.17 The teratogenicity with nitrous oxide initially was believed to result from rapid inhibition of methionine synthase in both animals and humans. However, this likely is not the only route of activity for several reasons: Maximal methionine synthase inhibition occurs at concentrations much lower than those required to produced teratogenic effects, use of folinic acid to bypass methionine synthase partially prevents minor skeletal defects, coadministration of isoflurane or halothane prevents almost all teratogenic effects without affecting methionine synthase activity, and replacement of methionine prevents malformations except for situs inversus defects.18 As such, the weak teratogenic effects of nitrous oxide are multifactorial. Regardless, the threshold requirements for adverse effects with nitrous oxide (ie, >50% concentrations for 24 hours) are not likely to be encountered clinically.

The animal and human experience with all drugs suggests critical periods of susceptibility to teratogens. In general, exposure to known teratogens during the first 2 weeks of embryonic development is marked by either death or minor cellular damage and ongoing survival; highly sensitive periods for developmental effects are during fetal organogenesis when major morphologic changes are occurring. Of note, clinical estimates of gestational age originate from the first day of the last menstrual period; however, because fertilization does not occur until 2 weeks after this time, 14 days are added to actual fetal development to correct for the discrepancy. Thus, whereas the period of major fetal organogenesis is considered to occur between 5 and 55 days of gestation, within the clinically used schemas, this period occurs in weeks 3 to 10 of pregnancy. Overall, anesthetic agents have limited effects from their earliest applications in assisted reproduction throughout pregnancy. Despite their limited effects, it seems prudent to limit the dose of anesthetics by using drug combinations or regional techniques.

Considerations on Maternal Physiology

The maternal and fetal consequences of anesthesia and surgery may be altered by pregnancy or pregnancy-related comorbid conditions (see Chapter 21). Even transient hypoxia, hypercapnia, stress, hypotension, and abnormalities in temperature and metabolism may adversely affect maternal and fetal outcomes. Alterations such as engorgement of the respiratory mucosa, increased consumption of oxygen, and hemodynamic effects of the gravid uterus represent important sources of concern in the provision of anesthesia during pregnancy.

Anesthesia-related maternal mortality has been declining over the past few decades but still accounts for 3% to 12% of maternal deaths; the majority occur as a result of failed intubation, ventilation, and oxygenation, or pulmonary aspiration with general anesthesia. These statistics rank anesthesia as the sixth leading cause of peripartum maternal mortality in the United States, with a risk of maternal death 1.7 times greater with general versus regional anesthesia.19 A comparison of maternal deaths caused by anesthesia in the Confidential Enquiries data of 2000 to 2002 with the data from 1964 to 1966 yields a 30-fold improvement associated with a reduction in general anesthesia use.20 Maternal deaths associated with general anesthesia can be partially explained by the significant airway changes that occur over the course of pregnancy and even during labor.21 The ability to secure the airway emergently has been associated with even greater difficulty,22 often requiring the use of alternative airway devices and techniques.23 Moreover, data from the recent national maternal mortality database in the United Kingdom20 and an epidemiologic analysis of maternal deaths in Michigan24 reveal that issues with extubation and postoperative respiratory failure have emerged as leading critical sources of maternal morbidity and mortality, particularly in women of high body mass index (BMI). These maternal outcome data strongly support the use of neuraxial techniques in both elective and emergent delivery situations when no contraindications exist for their use (Box 62-2).

The gravid uterus leads to progressively increasing cardiac demand and compromise of venous return during gestation. The growing uterus ultimately receives 600 to 700 mL/min of blood flow, which is of major importance when uterine trauma, including surgery, occurs. Moreover, the association between hypotension and the supine position in pregnant women, particularly in the late gestational state, is well demonstrated.25 Upon assuming the supine position, acute hypotension, with increased pulse rate, increased femoral venous pressure, pallor, and sweating, can occur within minutes, so use of left lateral displacement, even as little as 15 degrees, can reduce the incidence of hypotension and ultimately improve uterine blood flow and fetal health, as evidenced by improved blood gas values. This syndrome most likely is a manifestation of hormonal as well as mechanical changes. Hormonally, pregnancy-related alterations in renin, angiotensin II, cardiac natriuretic peptide, prostaglandins, progesterone, estrogen, and endothelin cause a relaxation in vascular tone, reduction in stroke volume, decrease in left ventricular compliance, and overall reduction in cardiovascular reserve. These changes ultimately make the cardiovascular system less able to compensate for any mechanical reductions in venous return by the gravid uterus, particularly when the patient is in the supine position. This difficulty in compensation is also observed after spinal anesthesia-induced hypotension.

Additional concerns witnessed only during pregnancy stem from the presence of trophoblastic tissue (ie, outermost layer of cells of the developing embryo that attaches to the uterine wall) and amniotic fluid. Intravascular systemic distribution of amniotic fluid may accompany uterine rupture or placental separation, leading to sudden cardiovascular collapse accompanied by coagulation disorders. More commonly, however, trophoblastic tissue from the maternal–fetal interface is implicated in the complications associated with preeclampsia, an entity for which delivery of the fetus or fetal tissues remains the only definitive therapy. Hypertensive crises, potential for seizures, intravascular depletion, and thrombocytopenia witnessed with preeclampsia are concerns relevant to anesthetic care (see section Hypertensive Disorders of Pregnancy).26

Considerations for Specific Situations

Concerns regarding the provision of analgesia and anesthesia for obstetric patients begin before pregnancy and continue through pregnancy, delivery, and the postpartum period. Throughout, anesthesia providers have the responsibility to consider the effects of their interventions during a variety of procedures, including assisted reproductive technologies, cerclage placement and removal, external cephalic version (ECV) attempts, nonobstetric surgery during pregnancy, in utero fetal surgery, labor and vaginal delivery, cesarean delivery, and tubal ligation. Anesthesia care during dilatation and evacuation procedures, which are performed for pregnancy termination, pregnancy loss and retained products, and procedures involving ectopic pregnancies, are discussed in Considerations for Specific Situations.

Assisted Reproductive Technologies

Whereas most patients undergoing procedures related to assisted reproductive technologies are young and otherwise healthy, a growing percentage has significant comorbid states that are responsible for either infertility or the inability to carry a pregnancy. For these individuals, assisted reproduction represents a mechanism to preserve fertility or to obtain oocytes for later use or transfer to gestational carriers. Almost all interventions that require anesthesia are for the purposes of oocyte retrieval and gamete (ie, sperm or oocyte) or embryo transfer. Most of these procedures are performed transvaginally with ultrasound guidance; on occasion, a transabdominal approach is used.

The anesthetic options for these procedures include paracervical, conscious sedation, spinal, epidural, and general anesthetic techniques.12 Paracervical anesthesia, which blocks sensation from vaginal but not ovarian pain fibers, often requires additional analgesia (Fig. 62-3). Conscious sedation techniques are the most commonly used mode of analgesia for oocyte retrievals; however, loss of consciousness, patient movement at critical times, and prolonged recovery room stays may result.12 Total IV general anesthesia provided with IV propofol (titrated) and fentanyl (50-100 mcg) offers an optimal approach. Midazolam (1-2 mg) can be added if needed to allay patient anxiety. Most patients can be managed with spontaneous ventilation via a high-flow oxygen mask and continuous carbon dioxide (CO2) analysis to monitor the adequacy of ventilation. On rare occasion, as in individuals with multiple risk factors for aspiration or the need for laparoscopy, an endotracheal tube is placed. Inhalational anesthesia with enflurane and 70% nitrous oxide has been shown to produce significantly greater rates of nausea and emesis and more unplanned admissions compared with an IV technique of propofol and alfentanil combined with an inhaled air–O2 mixture.12

Neuraxial techniques provide excellent pain relief with minimal oocyte exposure to anesthetic agents. Compared with sedation with propofol and mask-assisted ventilation with nitrous oxide, neuraxial techniques have been associated with fewer complications, especially nausea and emesis. Spinal anesthesia may be preferable to epidural anesthesia because of the reduced failure rate, lower systemic and follicular levels of anesthesia, and faster recovery profile.27 Short-acting local anesthetics (1.5% concentrations of lidocaine or mepivacaine 45 mg) or low-dose longer acting agents (0.75% bupivacaine 3.75 mg) can be used intrathecally for these procedures with good results. Use of low-dose bupivacaine may appeal to anesthesia providers hoping to reduce the incidence of transient radicular irritation associated with lidocaine or mepivacaine; however, a longer time to urination is witnessed, and greater amounts of intrathecal opioids (25 mcg) must be added.27 The addition of small doses of intrathecal opioids (fentanyl 10 mcg) to local anesthetics for spinal anesthesia improves postoperative analgesia for oocyte retrieval for the first 24 hours, with no increase in time to urination, ambulation, or discharge compared with local anesthetic alone.28

Pronuclear stage tubal transfer, zygote intrafallopian transfer, tubal embryo transfer, and gamete intrafallopian transfer are procedures that involve the transfer of gametes (sperm and oocytes) or embryos into the fallopian tubes during laparoscopy and local, regional, or general anesthesia. A general anesthetic with propofol and succinylcholine induction, intubation, and maintenance with isoflurane–oxygen and a short-acting muscle relaxant (eg, atracurium or vecuronium) or a succinylcholine infusion can be used. A propofol with nitrous technique also can be used and has been observed to cause less postoperative sedation, lower pain scores, and less emesis compared with an isoflurane with nitrous technique.12 Most embryo transfers occur 3 to 5 days after oocyte retrieval through a transcervical catheter technique that does not require sedation, analgesia, or anesthesia.

Postoperatively, especially after laparoscopic techniques, patients experience abdominal pain, uterine cramping, shoulder pain, nausea, and emesis. Pain is best treated with small doses of fentanyl (50-100 mcg IV) because use of nonsteroidal anti-inflammatory drugs may affect the prostaglandin milieu associated with embryo implantation.12 Droperidol and metoclopramide for treatment of nausea and emesis should be avoided when possible because of the associated high prolactin levels and the potential for adverse fertility effects.29 As with other outpatient procedures, patients should be able to drink and retain oral liquids, ambulate, and void before being discharged from the ambulatory procedure facility.

Special Concerns

Based on the presence of preexisting disease states, preoperative evaluations for patients requiring assisted reproductive technologies may range from simple, immediate preprocedural discussions to more complex investigations that require time to collect consultant reports, laboratory studies, electrocardiograms (ECGs), chest radiographs, and other testing results. All patients should be required to remain nil per os (nothing by mouth [NPO]) from solid foods for 8 hours before the time of retrieval, and if they have risk factors for aspiration (eg, obesity, history of reflux), a nonparticulate antacid should be administered orally before the procedure. Use of IV metoclopramide, as a gastric prokinetic agent or as prophylaxis for nausea, should be used sparingly because of potentially adverse fertility effects.29 Occasionally, a patient may not adhere to NPO policies, and although delaying or cancelling the case is a viable option, the decision should consider the risks of not proceeding, particularly with an oocyte retrieval. If the window for maximal oocyte retrieval (34-36 hours after human chorionic gonadotropin [hCG] administration) is missed, spontaneous ovulation and loss of oocytes can occur, invalidating the considerable effort and expense leading to the retrieval procedure. More importantly, if follicle aspiration is not performed, the patient is at increased risk for ovarian hyperstimulation syndrome, with its potential for tension ascites, thromboembolic phenomena, renal and hepatic dysfunction, and mortality.30 By contrast, the reduction in aspiration risk produced by delay or cancellation of the procedure is difficult to quantify, and a spinal anesthetic, instead of a technique that impairs airway reflexes, has an exceptional safety profile. As with all ambulatory surgical procedures, the ideal anesthetic results in effective pain relief with minimal postoperative nausea, sedation, pain, and psychomotor impairment.

Cerclage

A cervical cerclage is a circumferential suture placed around the cervical os to prevent pregnancy loss because of an incompetent cervix. It can be placed transvaginally or transabdominally with a laparoscopic technique. The clinical management guidelines from the American College of Obstetricians and Gynecologists (ACOG) acknowledge the limited data available on the efficacy of cerclages, yet the ACOG suggests that an elective cerclage should be performed at weeks 13 to 16 of gestation in patients with a viable fetus and a history of three or more otherwise unexplained second-trimester pregnancy losses or preterm deliveries.31 Urgent, or therapeutic, cerclages are often recommended for women with ultrasonographic changes consistent with a short cervix or evidence of funneling (ie, internal cervical os dilation).31

When the cerclage procedure is performed transvaginally, a hyperbaric subarachnoid anesthetic with a local anesthetic that produces approximately 30 to 45 minutes of anesthesia is a good option to avoid maternal airway manipulation and minimize fetal anesthetic exposure. By contrast, if the cerclage is performed transabdominally, a general anesthetic with endotracheal intubation is recommended.

Special Concerns

Although cerclage procedures are performed before week 20 of gestation, when the uterus transitions from a pelvic to an abdominal organ, the implications of NPO status and aspiration prophylaxis should be considered. The risk of aspiration during pregnancy, particularly early pregnancy, is controversial (see Chapter 21). However, in most situations requiring a cerclage placement, time exists to allow for gastric clearance, administration of aspiration prophylaxis, or both.

External Cephalic Version

Use of external abdominal pressure to turn a fetus from a breech to cephalic presentation is called ECV. Although the procedure is often performed in obstetric clinics without anesthetic intervention, improved maternal comfort, fetal safety, ECV success, and favorable cost-to-benefit analyses have been observed with neuraxial techniques.32 Neuraxial techniques most likely improve ECV efficacy by relaxing the abdominal wall muscles, improving patient comfort during the attempt and allowing the obstetrician to make a more concerted effort.32 In the more difficult setting of a repeat ECV after a previously failed attempt, a high success rate (83%) was reported with a spinal technique using 45 mg of lidocaine with 10 mcg of fentanyl.33 A CSE technique with a short-acting local anesthetic (1.5% lidocaine 45 mg) is the optimal technique for an ECV attempt because it allows for timely discharge from the hospital in the event of a successful version without labor, and if a trial of labor or an operative delivery is warranted or precipitated, the epidural catheter can be used for additional analgesia or anesthesia.33

Special Concerns

External cephalic version attempts may lead to maternal and fetal complications, including fetal heart decelerations, placental abruption, preterm labor, uterine rupture, amniotic fluid embolism, nausea, emesis, and fetal demise. These adverse outcomes should encourage an ECV attempt in the operating room with maternal and fetal monitoring and with anesthesia providers readily available. Even if neuraxial techniques are not used for the ECV attempt, rapid administration of anesthesia may be necessary for maternal or fetal intolerance. Moreover, although tocolytics (terbutaline, ritodrine) are frequently used to relax the uterus before ECV attempts, IV nitroglycerin (50-mcg bolus; wait 45 seconds before reattempt) has been reported to provide additional uterine relaxation.33 Because nitroglycerin administration is often accompanied by hypotension, the anesthesia provider should encourage its use only with maternal and fetal monitoring and anesthesia provider presence.

In Utero Fetal and Placental Surgery

A growing number of interventions are being used to correct placental abnormalities and fetal defects in utero. Laser photocoagulation of placental vessels responsible for twin-to-twin transfusion syndrome, percutaneous catheter dilation of fetal cardiac valvular defects, and open hysterotomy with fetal repair of diaphragmatic hernias or resection of tumors are a few currently available procedures.34 Ex utero intrapartum therapy, most commonly performed for large fetal head and neck tumors or severe heart and lung disorders immediately before cesarean delivery, allows partial fetal surgical exposure while maintaining placental circulation until an airway or alternate circulatory arrangement, such as extracorporeal membrane oxygenation, is secured.

Minimally invasive approaches with laparoscopic or percutaneous catheter techniques can be performed under local field blocks or neuraxial techniques. By contrast, operations that involve partial fetal exteriorization are best performed under general anesthesia for uterine quiescence and fetal anesthesia.35 Fetal anesthesia and immobility can be augmented through intramuscular administration of opioids, muscular relaxants, and atropine to the fetus. Maternal postoperative analgesia can be improved with neuraxial preservative-free morphine (3 mg epidural, 0.2 mg subarachnoid) even if a general anesthetic is planned. Occasionally, more invasive monitoring, as with an arterial or central venous catheter, is warranted to allow for more immediate blood pressure and central venous pressure (CVP) monitoring and vascular access for laboratory studies during the perioperative and intraoperative periods.

Special Concerns

The ability and timing of sentience, the capacity to experience painful or unpleasant sensations, in fetuses is a subject of growing interest and controversy.36 Because structural and behavioral maturation ultimately determine the capacity to feel pain, the presence of reflex responses and cortical connections may not necessarily represent the ability to experience nociception. Although synapses to and from the cortex are present as early as 8.5 weeks of gestation, structures believed necessary for conscious pain perception, such as thalamic projections, intracortex connections, and synchronous electroencephalographic activity, have not been observed until 20 to 30 weeks.36 Fetal analgesia or anesthesia, however, should be considered to prevent hormonal stress responses that may be associated with poor neonatal surgical outcomes or long-term neurodevelopmental and behavioral responses to pain and to inhibit fetal movement during procedures.37 Fetal analgesia and anesthesia can be achieved by passive analgesic administration via maternal general anesthesia or by direct intramuscular injection into the fetus. Injection of opioids directly into the amniotic fluid, which results in greater fetal than maternal concentrations in animal models, is a modality that may have application in the future.38

Labor and Vaginal Delivery

The pain of labor and vaginal delivery evolves through the first and second stages of labor (see Fig. 62-3). The first stage of labor, defined as the onset of regular uterine contractions that result in progressive uterine cervical dilation, produces pain originating from both uterine and cervical stretching. Described as dull, aching, crampy, and poorly localized, the pain sensations are carried by visceral afferents entering the spinal cord at the T10 to L1 level. By contrast, the second stage of labor, defined as the time from complete cervical dilation to the delivery of the fetus, produces pain originating from vaginal and perineal stretching. More somatic in origin, the pain is sharp, is discrete in location, and is carried by the lower lumbar and sacral fibers. Of interest, the contemporary pattern and progress of labor appear slower than previously described a half a century earlier.39 Attributed to the greater maternal age and weight, increased fetal size, and significantly higher use of induction of labor, these factors may contribute to labor pain of longer duration.

A variety of techniques are used to provide analgesia during labor and delivery (see Box 62-3). Neuraxial techniques have been demonstrated to be the most effective form for labor analgesia,40 but there are some contraindications to their use (see Box 62-2). Moreover, other techniques have been found to be useful or comforting for parturients and may add to overall maternal satisfaction with the birth experience. Various techniques are often used sequentially as labor progresses; however, their simultaneous use may not offer advantages greater than an epidural technique. Transcutaneous nerve stimulation, for example, does not appear to augment either epidural or CSE techniques.41,42 Clear communication between the patient and all members of the health care team is essential for the proper timing of anesthetic care. In some cases, such as morbid obesity or preexisting back pathology, early placement of an epidural catheter with activation later during labor may be an optimal approach for maternal and fetal outcomes.43 The concern that neuraxial analgesia techniques could mask the pain of a uterine rupture in women with previous cesarean deliveries or uterine scars appears unfounded. Indeed, the presence of an epidural catheter in women undergoing vaginal birth after cesarean delivery may improve maternal and fetal outcomes by allowing for expedient cesarean delivery anesthesia if uterine rupture or fetal distress occurs. Overall, the use of epidural, spinal, CSE, and DPE techniques should be evaluated for each parturient because the duration of labor and the mode of delivery are not known a priori in most cases. If the patient desires or requires analgesia or anesthesia, a catheter-based technique allows for the most flexibility.

Epidural Analgesia

The epidural technique is the most common neuraxial technique used for labor analgesia because of relatively rapid sensory analgesia with minimal motor blockade, uterine effects, and maternal or fetal toxicity (see Fig. 62-2).9,40 Almost all local anesthetics can be used in low concentrations; however, the longer-acting agents allow for less variation in the quality of analgesia (see Table 62-1). Bupivacaine, which provides a high ratio of sensory to motor block, is the most commonly used agent for labor epidural analgesia worldwide. Ropivacaine and levobupivacaine are newer long-acting agents that, when given in equipotent concentrations to bupivacaine, may result in slightly less motor blockade and fewer cardiotoxic effects should intravascular absorption occur.44,45 Epidural opioids alone provide sufficient analgesia for the first stage of labor (see Table 62-2),46 but the combination of small doses of sufentanil (0.2-0.3 mcg/mL) or fentanyl (0.2 mcg/mL) with low doses of bupivacaine (0.0625-0.125%) is necessary for second-stage labor and vaginal delivery. An epidural bolus of 100 mcg of fentanyl with or without local anesthetic can improve maternal comfort during the second stage of labor when patchy analgesia or perineal sparing cannot be remedied with local anesthetics alone.47

After the initial sensory blockade has been established, epidural analgesia can be maintained by intermittent bolus injections, continuous infusion, or both techniques simultaneously. The development of inexpensive infusion pumps has offered perhaps the optimal method: continuous infusion coupled with patient-controlled intermittent bolus injections through the epidural catheter. This combined method reduces the total amount of medication used, decreases the amount of motor blockade, and increases patient satisfaction compared with continuous infusions or intermittent bolus methods alone.48

Is an instrumental or operative delivery, laceration repair, or postpartum tubal ligation occurs, labor epidural analgesia can be transitioned to anesthesia with a change in the concentration or type of local anesthetic used through the catheter (see Table 62-1). Vacuum or forceps deliveries often require denser perineal sensory anesthesia for placement of instruments than offered by contemporary labor analgesia infusion concentrations as noted earlier in this section. This can be accomplished using 6 to 7 mL of 1% lidocaine solution with 8.4% bicarbonate in a 10:1 ratio. Increasing the sensory level from the tenth to the seventh or eighth thoracic dermatome also allows for more rapid anesthetic extension to a fourth thoracic dermatome if the need for an emergent cesarean delivery develops.

Spinal Analgesia

The limited duration of action of a single injection and the increased risk of PDPH with multiple injections limit the utility of spinal anesthesia for the management of labor. Spinal techniques, however, can be used successfully in the immediate peripartum period, especially in the event of a precipitous vaginal delivery, use of outlet forceps or vacuum extractions, or repair of extensive perineal lacerations. Short-acting, low-level spinal anesthesia can be used for many of these procedures; however, the range of likely obstetric outcomes should be evaluated carefully. A delivery by "trial of forceps," for example, can quickly transition to an urgent cesarean delivery. Spinal techniques that offer more flexibility include the CSE technique and a spinal catheter technique.

Combined Spinal Epidural Analgesia

The CSE technique for labor analgesia has increased in popularity.9 When placed early in labor and compared with parenteral opioid or standard epidural techniques, a CSE technique with opioids alone or in combination with local anesthetics may have beneficial effects on motor ability and the progress of labor.49,50 Used later in labor, the CSE technique can provide quick onset of analgesia and the ability to extend the duration or level of the blockade in case delivery methods mandate such augmentation. The DPE technique is a variation of the CSE technique, in which a dural puncture is performed in the typical needle-through-needle method; however, medications are not directly dosed into the intrathecal space. Instead, all medications are administered into the epidural space and indirectly allowed to spread into the intrathecal space through the dural puncture. The technique provides faster onset, improved bilateral and sacral analgesia, and no alterations in motor or cephalad sensory spread compared with a conventional epidural technique.3 When dilute labor analgesic concentrations (eg, <0.25% bupivacaine) are used, the effect appears to be present when a 25-gauge spinal needle is used3 but not with a 27-gauge needle.51

Special Concerns: Progress of Labor

Whether central neuraxial analgesia affects the progress and outcome of labor remains a controversial topic. The myriad of maternal and fetal variables and the differences in anesthetic and obstetric practices are confounding factors in such studies. Moreover, methodologic problems, such as difficulties in randomization and blinding, make an association difficult to evaluate. Overall, however, the use of epidural analgesia appears to have little effect on the progress and outcome of labor. A meta-analysis of 10 trials comparing parturients of mixed parity randomized to epidural analgesia or parenteral opioids noted a prolongation of the first and second stages of labor by 42 and 14 minutes, respectively, in association with the use of epidurals.52 Despite the belief that an arbitrary threshold of 5 cm of cervical dilation should be achieved before epidural analgesia administration to prevent cesarean delivery,53 early (<4 cm) placement of CSE labor analgesia versus parenteral opioids49 or standard epidural techniques50 has resulted in shorter times to achieve full cervical dilation with no alterations in the cesarean delivery rate. Overall, the risk of cesarean delivery does not appear to be increased with the use of neuraxial labor analgesia.54

Anesthetic Complications

A number of complications may occur after neuraxial techniques (Table 62-3). Hypotension, defined as a 20% to 30% decrease in systolic blood pressure from baseline, can be observed in 20% to 100% of pregnant women as a result of the sympathetic vasomotor blockade associated with neuraxial analgesia and anesthesia.55 Left uncorrected, hypotension may result in decreased uteroplacental perfusion, fetal hypoxia, and acidosis.56 Preventive measures include maternal intravascular volume expansion with 500 mL of colloid (eg, hetastarch) or 1000 mL of crystalloid (eg, lactated Ringer solution) within 15 minutes of the neuraxial technique and positioning with a 15-degree left lateral tilt to avoid uterine aortocaval compression. Titrated doses of IV vasopressors, such as 5 to 10 mg of ephedrine or 40 to 100 mcg of phenylephrine, can be used prophylactically to minimize and treat hypotension. The nausea and vomiting after neuraxial techniques may be associated with reductions in sympathetic tone, blood pressure, and cerebral blood flow and can be reduced significantly with vasopressor use.57 PDPH occurs in approximately 1% to 3% of the obstetric population after dural puncture and is related to needle size and tip design, with larger, cutting (beveled) needles associated with a greater incidence.58 Typically, PDPH presents as a positional headache that worsens and improves in the upright and recumbent positions, respectively. The differential diagnosis should include other types of headaches, hypertensive disorders, infectious diseases, dural venous sinus thromboses, and other intracranial pathologies. If the diagnosis of PDPH is made, bed rest may aid in pain relief,59 and conservative measures of hydration and oral intake of caffeinated and analgesic products (including Fioricet or Fiorinal) can be used for 24 to 48 hours. An epidural blood patch, with 10 to 20 mL of autologous blood placed in the epidural space, has been associated with a greater than 80% incidence of success in most trials.58,60 Although significant complications (eg, cauda equina syndrome, transverse myelitis, arachnoiditis, spinal–epidural abscesses, and vascular trauma) after neuraxial analgesia and anesthesia in the obstetric population are extremely rare,60 when signs and symptoms are unclear or rapidly progressing, consultation with a neurologist may assist in diagnosis and treatment. Finally, an unexpected high level of anesthesia can result in hypotension, dyspnea, an inability to speak, and loss of consciousness. Ventilatory and circulatory support should always be readily available when these techniques are provided.

Relatively few complications are inherent to the CSE or DPE techniques per se. The risks of a dural puncture with an epidural needle may actually be reduced because CSF within the smaller spinal needle can be used to confirm proximity to the epidural space and prevent inadvertent dural puncture by the larger epidural needle. The likelihood of the epidural catheter passing through the spinal needle dural puncture site is low in laboratory and clinical studies.61 With the DPE technique, the timing and dose of the epidural bolus and the size of the dural puncture appear to be important. Labor analgesia medications placed in the epidural space after a 25-gauge dural puncture have salutary analgesic effects,3 however, appear to have limited passage through a 27-gauge dural puncture.51 The risk of a high spinal blockade as a result of a CSE or DPE technique appears negligible.3 The failure of an "untested" epidural catheter after the spinal portion of a CSE technique is a potential concern, but epidemiologic evidence suggests that CSE epidural catheters have a lower failure rate than does the epidural technique alone.62 In parturients with difficult airway access or those with a high probability of an instrumental or operative delivery, a standard epidural technique, which tests the function of the catheter at the time of placement, may be a safer alternative.

Cesarean Delivery

With the advent of fetal heart rate and tocodynamometric monitoring, a reduction in breech and forceps-assisted deliveries, and the changing social and medicolegal environment, cesarean deliveries now account for 25% to 30% (range 1.8%-40.5%) of deliveries nationally and internationally.63,64 Although anesthesia-related maternal mortality has been declining during the past few decades, it still accounts for 3% to 12% of maternal deaths, with the majority associated with general anesthesia secondary to failures in intubation, ventilation, and oxygenation.20,24 As such, the use of neuraxial techniques has been strongly preferred. However, the urgency of the procedure, the health and comorbidities of the mother and fetus, and the desires of the mother and health care providers must be considered when deciding on the optimal anesthetic technique.

Cesarean delivery is performed most commonly through a low transverse abdominal incision (Pfannenstiel) above the pubic crest, with dissection of the fascia and separation of the rectus muscles. After opening of the peritoneum, a transverse uterine incision (hysterotomy) typically is used for delivery of the fetus. Advantages of the transverse incision include better cosmetic results, less pain, and a low incidence of hernia formation. Disadvantages include limited access to the upper abdomen, a greater incidence of subfascial hematomas from small perforating vessels through the rectus muscle, and increased nerve injury resulting in overlying skin paresthesias. In the setting of a preterm cesarean delivery, especially before elongation of the lower uterine segment in week 34 of gestation, the hysterotomy is sometimes performed with a vertical incision for greater surgical exposure. Because a vertical uterine incision is more prone to dehiscence or rupture with uterine contractions, all subsequent pregnancies must undergo a cesarean delivery.

Regardless of the type of incision, uterine tone may be compromised in preterm deliveries and with prolonged exposure to oxytocin (eg, induction and augmentation of labor) because of low or downregulated numbers of oxytocin receptors, respectively.65 Uterine tone may be further limited in conditions that augment the size of the uterus, such as polyhydramnios, multiple gestation, and fibroids. Uterine atony accounts for 75% to 90% of postpartum hemorrhage and remains a leading cause of postpartum hysterectomy and blood transfusion. In an attempt to reduce the incidence of uterine atony and its sequelae, initial efforts at time of cesarean delivery include uterine massage and IV oxytocin, a uterotonic medication (Table 62-4). Only small doses of oxytocin (0.3 IU and 3 IU for parturients without and with prior exposure to oxytocin, respectively) appear necessary to produce adequate uterine tone after cesarean delivery.65-67 Oxytocin bolus doses should be administered slowly (no faster than 15 sec) and followed with a maintenance dose of 3 IU/h for 5 to 8 hours after delivery.65-67 Particularly when given as a rapid IV bolus, oxytocin has been associated with a high incidence of morbidity, including hypotension, nausea and vomiting, antidiuretic effects leading to fluid retention and pulmonary edema, and even death from cardiovascular collapse.68,69 If oxytocin fails to provide sufficient uterine tone, other more powerful uterotonic agents, including prostaglandins (15-methylprostaglandin 250 mcg) and ergot preparations (methylergotamine 200 mcg) should be administered intramuscularly or directly into the myometrium at intervals of 15 to 20 minutes up to a total dose of 1 mg. These agents, however, are associated with significant side effects, including nausea, bronchospasm (especially with prostaglandins), hypertension, pulmonary edema, and cerebral hemorrhage.70 If these medical therapies fail, uterine or hypogastric artery ligation, interventional arterial balloon catheterization, or hysterectomy may be necessary.

Spinal Anesthesia

A simple and reliable technique with rapid onset, spinal (subarachnoid) anesthesia provides an awake and comfortable patient with minimal risks for pulmonary aspiration of gastric contents. Despite the lower abdominal incision, a T4 sensory dermatome level is required to prevent referred pain from traction on the peritoneum and uterus. The type and dose of local anesthetic used to provide the spinal anesthetic must include consideration of the level of anesthesia desired, duration of surgery, postoperative analgesia plan, and preferences of the anesthesiologist. Spinal administration of hyperbaric 0.75% bupivacaine with fentanyl and preservative-free morphine may be the optimal combination (Box 62-4). Whereas the almost immediate onset of fentanyl reduces visceral discomfort and even nausea during the procedure, the delayed onset and 18- to 20-hour duration of morphine provides prolonged relief following the procedure. Although ropivacaine and levobupivacaine can be used in similar concentrations and doses, the potential for reduced toxicity if intravascular absorption occurs seems limited given the extremely small doses of agents used. Adjuvant spinal medications, including epinephrine, may augment the quality and duration of the anesthesia and analgesia.71,72

After administration of a subarachnoid technique, the patient may complain of dyspnea. This can occur because of several factors, including blunting of thoracic proprioception, partial blockade of abdominal and intercostal muscles, and increased pressure of the abdominal contents against the diaphragm in the recumbent position. Despite these changes, significant respiratory compromise is unlikely because the blockade rarely affects the cervical nerves that control the diaphragm. If the patient loses the ability to vocalize, give a strong hand grip, or demonstrate oxygen desaturation by pulse oximetry, a rapid sequence induction of general anesthesia, with cricoid pressure and placement of an endotracheal tube, can be performed to maintain ventilation and prevent pulmonary soiling with gastrointestinal contents.

The most common complications of spinal anesthesia have been described earlier under Anesthetic Complications and include hypotension, nausea and vomiting, and risk of PDPH.

Epidural Anesthesia

Use of epidural anesthesia for cesarean delivery has increased during the past 2 decades, primarily as a result of its use for labor analgesia. Although medications used in the spinal and epidural space are identical, epidural doses are 5 to 10 times greater and given in much larger volumes to encourage adequate blockade and spread of the drug. Overall, a greater sensitivity of nerves to local anesthetics during pregnancy has been observed clinically through decreased anesthetic requirements for epidural blockade,73,74 For cesarean delivery, the most commonly used agents are 2% lidocaine with epinephrine 1:200,000 or 3% 2-chloroprocaine. Chloroprocaine is the agent of choice for emergency cesarean deliveries because of its rapid onset and rapid maternal and fetal metabolism; fetal accumulation, especially when acidosis is present, is minimized.75 By contrast, chloroprocaine is avoided for routine nonurgent deliveries because the short duration requires multiple doses, and its use can adversely affect the efficacy of subsequent epidural opioid analgesia.76 In addition, chloroprocaine used in higher total volumes (>40 mL) can increase the incidence of back pain.77 Alkalinization with sodium bicarbonate hastens the onset time of local anesthetics significantly and is recommended for use in urgent cesarean deliveries with 1 mL of 8.4% bicarbonate for every 10 mL of lidocaine or chloroprocaine (Fig. 62-4).78 By contrast, 10 mL of bupivacaine, levobupivacaine, or ropivacaine precipitates out of solution with less than 0.5 mL of bicarbonate, leading to an inability to inject the local anesthetic through a needle or catheter; therefore, bicarbonate should not be added to these longer-acting local anesthetics.79

The complications of epidural anesthesia have been described previously under Anesthetic Complications and include hypotension, risk of PDPH, systemic toxic reactions, and (rarely) neurologic complications. Epidural techniques can provide patchy or inadequate blockade because of anatomic or technical reasons.80 Often, these failures can be identified a priori through observation of the quality of labor epidural analgesia or quickly after partial augmentation of the blockade. Alternative techniques, such as supplementation with IV or inhalational agents, spinal anesthesia, or general anesthesia, must always be considered as options when analgesia is clearly inadequate.

Combined Spinal–Epidural Anesthesia

The principal advantage of the CSE technique for cesarean delivery is the ability to augment the density or duration of the anesthesia administered via the epidural catheter. This is particularly useful in obstetrics when a trial of labor may be attempted before an operative delivery or the duration of the surgery may be prolonged (eg, possible placenta accreta, history of multiple abdominal surgeries, high index of suspicion for gravid hysterectomy).

Special Concerns during Cesarean Delivery

Although neuraxial anesthesia is used whenever possible to avoid the potential airway complications associated with general anesthesia, certain conditions or time constraints may contraindicate its use (see Box 62-2).81 Such comorbidities include localized infection or generalized sepsis, coagulation disorders, severe hypovolemia, and cardiac pathologies where hypotension may be especially detrimental. Severe obstetric hemorrhage in the antepartum period, including uterine rupture and acute and severe fetal distress, also may contraindicate the use of neuraxial anesthesia procedures because of the time necessary to establish a surgical anesthetic.

Patients with severe preeclampsia or hypertension may undergo rapid hemodynamic changes with neuraxial techniques; however, both epidural and spinal techniques have been used successfully in this setting with similar vasopressor requirements as nonpreeclamptic patients.82,83 In addition, gravid hysterectomies can be performed safely with neuraxial techniques.84 Overall, however, general anesthesia should be considered if questions exist regarding the ability of maternal compensatory mechanisms to react to the neuraxial anesthetic or surgery.

Hypotension presents the greatest risk to maternal and fetal comfort and health.56 Prevention and prompt treatment with IV fluids and administration of vasopressors have been beneficial but may not be completely successful.85,86 In terms of volume expansion, spinal anesthesia in the urgent setting should not be delayed until a fixed arbitrary volume has been infused. In addition, aggressive hydration with large fluid volumes (>20 mL/kg crystalloid) may increase the risk of edema with only limited reductions in hypotension.85 Colloid solutions appear to be more effective than crystalloids in preventing the hemodynamic consequences of spinal anesthesia.87 However, in most cases, the allergic, cost, and coagulation implications offset their benefit. Current investigations into the use of vasopressors for prevention and treatment of hypotension in this setting include use of phenylephrine, sometimes in combination with ephedrine, administered via bolus and infusion pump techniques.88,89 Although most animal studies indicate combined α- and β-adrenergic agonists (eg, ephedrine) are more effective than α-adrenergic agonists (eg, metaraminol, phenylephrine) in terms of restoration of maternal blood pressure and fetal acid–base status, clinical investigations appear to favor the use of α-adrenergic agonists.90 Because clinical and animal data do not support a single agent in all circumstances, a rational strategy is vigilance and a proactive response with both ephedrine and phenylephrine as guided by maternal blood pressure and heart rate.

Nausea and emesis during and after cesarean delivery can have a number of causes but are best prevented by controlling hypotension, optimizing the use of neuraxial and IV opioids, improving the quality of surgical blockade, minimizing surgical stimuli, and judiciously administering uterotonic agents.91

Although pruritus after neuraxial blockade is attributed to a number of postulated mechanisms and has several treatments,92 a narcotic antagonist or partial antagonist (eg, nalbuphine 4 mg IV) appears more effective than some other modalities. Postoperative shivering also may have several etiologies and treatments. Administration of 25 mg of IV meperidine, 150 mcg of clonidine, 100 mg of doxapram, 10 mg of ketanserin, and 250 mcg of alfentanil all have been used with success, although meperidine appears to be the most consistently effective.93

General Anesthesia

There are few, if any, absolute contraindications to general anesthesia. However, neuraxial anesthesia remains a preferred method to avoid the risks of airway management and allow the patient the ability to witness delivery of the fetus. General anesthesia, however, may offer advantages in cases in which uterine relaxation would be beneficial, such as extracting difficult breech presentations, removing retained placentas, restoring uterine inversions, and performing in utero fetal operations.

The importance of proper airway evaluation during the antenatal period or in early labor, if possible, cannot be overemphasized because failed intubation, failed ventilation and oxygenation, and pulmonary aspiration of gastric contents are the leading anesthetic causes of maternal death.94,95 If the airway evaluation suggests a difficult intubation or risk factors for a difficult neuraxial placement (eg, morbid obesity, scoliosis, dropping platelet count), the establishment of a continuous neuraxial technique early in labor should be strongly encouraged.43,96 If the parturient does not desire epidural analgesia during labor, the epidural catheter still can be placed, tested for a bilateral sensory distribution with 6 to 7 mL of 1% to 2% lidocaine with bicarbonate, and then allowed to wear off until such time that analgesia or anesthesia is desired.43 If a difficult airway is discovered during a rapid sequence intubation attempt, options include allowing the patient to awaken, using alternate techniques (eg, fiberoptic- or light-guided intubation) to place an endotracheal tube, or using alternative airway devices (for a detailed review of airway management, see Chapter 35). Although the laryngeal mask airway (LMA) cannot prevent pulmonary soiling with gastric contents, it can be a lifesaving measure in failed intubation situations.97 LMAs have been used without adverse sequelae with continuous cricoid pressure held for the duration of cesarean delivery.98 Emergency airway equipment should be readily available in all obstetric operating rooms.

Attempts should be made to minimize the risk of maternal aspiration even when the need for intubation is not anticipated. With an elective cesarean delivery, adherence to a food and clear liquid NPO policy for 8 and 4 hours, respectively, before surgery is advised. A nonparticulate antacid is believed to decrease damage to the respiratory epithelium if aspiration occurs,99 and H2 antagonists (cimetidine, ranitidine) and promotility agents (metoclopramide) can reduce gastric acid secretion and facilitate emptying, respectively.100,101

The patient should be placed supine with left uterine displacement and optimal airway positioning. After the placement of routine monitors, including ECG, pulse oximetry, blood pressure, and capnography, preoxygenation and denitrogenation with 100% oxygen should be performed to delay the onset of hypoxemia stemming from the parturient's decreased functional residual capacity and increased oxygen consumption. In urgent situations, four maximal (ie, approaching vital capacity) breaths of 100% oxygen will provide adequate preoxygenation.102 After the surgical drapes have been applied and the operating personnel are ready at the bedside, the surgeon should be instructed to delay the initial incision until the anesthesia provider confirms correct placement of the endotracheal tube and gives verbal confirmation to proceed with the operation. A rapid-sequence induction with full cricoid pressure after induction with 4 to 5 mg/kg of thiopental and 1 to 1.5 mg/kg of succinylcholine is performed. Ketamine 1 to 1.5 mg/kg should be substituted for thiopental if hemodynamic instability is present before induction. Cricoid pressure should be continued until correct positioning of the endotracheal tube is validated with auscultation and confirmation of carbon dioxide. A short-acting nondepolarizing agent or succinylcholine infusion can be used to maintain muscle relaxation.

In most instances, less than 50% fraction of inspired oxygen (FiO2) is sufficient, but 100% FiO2 oxygen should be used if fetal compromise exists. Some evidence suggests that greater than 60% FiO2 may result in detrimental fetal oxygen-free radical formation in the fetus.103 Maintenance of anesthesia can be provided with volatile anesthetics titrated as necessary; however, upon delivery, concentrations should be reduced to less than 1 to 1.5 MAC, the threshold above which relaxation of uterine tone cannot be attenuated with oxytocin. No advantage in minimizing uterine tone relaxation or fetal effects has been found with the selection of specific volatile anesthetic agents (isoflurane, sevoflurane, or desflurane). Overall, a 25% to 40% reduction in halogenated agent requirements is witnessed during pregnancy.104 Comparison of neonatal outcomes after general versus epidural anesthesia for cesarean delivery suggests small, transient differences.105 However, with both techniques, a uterine incision to delivery time longer than 180 seconds can result in lower Apgar scores and greater fetal acidosis (most likely reflecting the difficulty in delivering the baby rather than direct effects of the anesthetic agents).106 General anesthetic agents can redistribute from the fetal fat to the fetal circulation and result in secondary depression of neonatal ventilatory effort. Thus, the presence of a pediatrician in such cases is advisable until a normal ventilatory pattern is observed.

Maternal oxygenation and ventilation should be carefully observed after extubation in both the immediate and later postoperative periods. In contrast to earlier reports that identified failures during intubation as the cause of inadequate airway management and ventilation, the majority of recent maternal deaths related to anesthesia have occurred in the postoperative period after general anesthesia administration.20,24 Risk factors for maternal postoperative respiratory arrest include high BMI and the presence of highly pigmented skin (impairing the clinical observation of hypoxemia).24

Postoperative Pain Management

By directly activating spinal and supraspinal opioid receptors, epidural and spinal opioids blunt nociceptive input and produce analgesia of greater intensity than doses administered parenterally or intramuscularly (see Chapter 74).7 Morphine has emerged as the leading agent for post–cesarean delivery analgesia because of its long duration of action and low cost (see Table 62-2); optimal doses are 0.1 and 3.75 mg in the intrathecal and epidural spaces, respectively.71,107 Because of its low lipid solubility, the peak analgesic effects of morphine are delayed 60 to 90 minutes but persist to provide reliable analgesia for up to 24 hours.107 A sustained-release epidural morphine preparation that can provide up to 48 hours of post–cesarean delivery analgesia has been developed108; however, its use is limited by its immediate release when mixed with local anesthetics and the inability for its use in the intrathecal space. Thus, it is being used as a part of a CSE technique in which the local anesthetic is placed in the intrathecal space followed by administration of morphine in the epidural space.

The choice of local anesthetic for epidural anesthesia may influence the efficacy of epidural morphine. In parturients who received 2-chloroprocaine (a short-acting, rapid-onset local anesthetic used primarily for emergent cesarean deliveries) versus other local anesthetics, post–cesarean delivery analgesia was significantly reduced to less than 3 hours.109 The mechanism by which chloroprocaine affects the duration of opioids, as well as other local anesthetics, is unknown. These interactions, coupled with the potential for neurotoxicity, especially when preserved with metabisulfite, limit the use of chloroprocaine to emergent situations where rapid augmentation is desired.110 Patient-controlled epidural infusions of low-concentration local anesthetics with opioids (eg, bupivacaine 01.25% with 0.2 mg/mL of hydromorphone or 2 mcg/mL of fentanyl at 6 mL/h) may offer an analgesic option in patients in whom prolonged, nonsystemic analgesia is desired.111

Postoperative analgesia has been greatly improved through the use of central neuraxial techniques, most commonly provided through a single-dose administration of morphine. Given in the spinal and epidural compartments, opioids provide enhanced quality and duration, with a very acceptable side effect profile compared with oral and IV analgesics. Adequate management of postoperative cesarean delivery pain may decrease the low but notable occurrence of chronic pain.112

Considerations for High-Risk Parturients

Antenatal and Postpartum Hemorrhage

Vaginal bleeding occurs in up to 24% of clinically diagnosed pregnancies and most often is associated with minimal blood loss and limited pathology. However, major antepartum and postpartum bleeding may occur at any time and is a leading cause of maternal and perinatal morbidity and mortality. What constitutes "bleeding" versus "hemorrhage" is an issue of semantics. More important is recognizing that blood loss and physiologic deterioration can occur rapidly and that a cogent plan of investigation and response can significantly affect the outcome.

Divided by week 20 of gestation into early and late time periods, antepartum hemorrhage is associated with a number of etiologies. Early-pregnancy bleeding can result from implantation or miscarriage of the embryo, an ectopic pregnancy, gestational trophoblastic disease, dysfunctional uterine bleeding, and reproductive tract tumors. In first-trimester pregnancies complicated by bleeding, less than 50% will progress normally beyond 20 weeks of gestation, 10% to 15% will be an ectopic pregnancy, 0.2% will be a hydatidiform mole, and more than 30% will result in a miscarriage.113 Bleeding during late pregnancy complicates 2% to 5% of pregnancies, with the most common causes being placental abruption (31%) and placenta previa (22%; Table 62-5).

Although obstetric hemorrhage can be masked by physiologic adaptations in blood volume and cardiac output (see Chapter 21), ultimately, the 600 to 700 mL of blood flow through the placental intervillous spaces each minute can result in signs of shock (Table 62-6).113 Coagulopathy, initially dilutional from the ongoing loss of blood components and rapid volume replacement, may be accompanied by disseminated intravascular coagulation (DIC). Laboratory analysis of DIC includes a prolonged prothrombin time (PT), prolonged partial prothrombin time (PTT), hypofibrinogenemia, thrombocytopenia, and elevated fibrin degradation products.

Underestimation of blood loss and inadequate resuscitation are common problems in cases of antepartum hemorrhage resulting in maternal mortality. In a report on maternal deaths in the United Kingdom, substandard responses were noted to be a contributing factor in 79% of maternal deaths resulting from hemorrhage.114 Rapid volume replacement is more important for tissue perfusion and oxygenation than is the type of fluid given. Large-bore IV access with pressurized transfusion equipment is essential during severe hypovolemia. Intravascular expansion with colloids versus crystalloid preparations during pregnancy has been observed to be longer in duration and more effective in augmenting cardiac output. These qualities are helpful in cases of peripartum hemorrhage and may be an effective bridge until blood products are available.87 Although many institutions require a type and screen for parturients who are at high risk for hemorrhage and undergoing vaginal delivery or for all parturients undergoing cesarean delivery, a cross-match for 2 to 4 units of packed red blood cells (PRBCs) should be considered when the potential for significant blood loss appears eminent. Such cases often involve abnormalities with placentation, including low implantation (previa), partial abruption, adherence without a decidual layer, invasion into the myometrium, or penetration through the myometrium (placenta accreta, increta or percreta, respectively). Imaging tests, especially ultrasonography and magnetic resonance imaging, have dramatically altered the evaluation and outcome of these placental abnormalities. More recently, the use of interventional radiologic techniques for placement of prophylactic or treatment transcatheter occlusion balloons within the uterine or hypogastric arteries has allowed for timely control of bleeding.115 When uterine bleeding occurs postpartum, use of an inflated balloon catheter placed in the uterine cavity and filled with 70 to 300 mL of warm saline has been demonstrated to tamponade and potentially treat intrauterine sources of bleeding and allow time to correct coagulopathies.116

When the need for emergent blood transfusion precedes the availability of cross-matched blood, then uncross-matched, type O, Rh-negative blood should be used. Continued blood loss and hemodynamic instability despite transfusion of PRBCs often is an indication for an arterial line and more invasive monitoring. However, restoration of circulating volume takes precedence. Urine output, heart rate, and blood pressure assessments can assist in rapid assessment of volume resuscitation. After the delivery of the fetus, when uterine perfusion and oxygenation become less relevant, parturients usually are able to tolerate low hemoglobin, coagulation proteins, and platelets. Although obstetric transfusion protocols are beginning to consider defined transfusion ratios of PRBCs, plasma, and other component therapy in the presence of major hemorrhage, there is no consensus on an optimal protocol. The task force on blood component therapy of the American Society of Anesthesiologists has stated that transfusion of PRBCs, platelets, and fibrinogen component therapy is rarely indicated unless the hemoglobin concentration is less than 6 g/dL, platelet count is less than 50 × 109/L (unless platelet dysfunction and microvascular bleeding is present), and fibrinogen concentration is less than 80 to 100 mg/dL in the presence of microvascular bleeding (for details of transfusion therapy, see Chapter 85).117

Simultaneously with fluid resuscitation, a hemorrhaging parturient should be prepared for an operative delivery, if not already accomplished, and a possible hysterectomy. Complete replacement of blood loss before or during surgery is frequently an unrealistic goal because bleeding often continues until the offending pathology is corrected or removed. Although a neuraxial anesthetic approach can be continued if the bleeding is modest and controllable, the case of a briskly bleeding, hemodynamically unstable patient requires induction of general anesthesia, controlled ventilation, and aggressive fluid resuscitation.

Hypertensive Disorders of Pregnancy

Whether preexisting, gestational, or related to preeclampsia or eclampsia, hypertension is associated with a higher incidence of maternal, fetal, and neonatal mortality and morbidity. Preeclampsia, with its systemic vasoconstriction, intravascular volume and protein depletion, and simultaneous retention of extravascular sodium and water, is of particular concern to anesthesiologists. In addition to individual organ dysfunction, abnormalities in coagulation and edema of the brain, larynx, and lungs may occur. Medical management of blood pressure should be achieved before obstetric or anesthetic interventions if possible. Control of blood pressure with labetalol, hydralazine, or infusions of nitroglycerin or nitroprusside should be commenced with arterial and central venous monitoring in severe cases. Of note, use of magnesium for prevention of seizures and use of antihypertensive medications for control of severe hypertension (systolic pressure >160 mm Hg or diastolic pressure at least 110 mm Hg) may affect the duration of muscle relaxants and the response to induction medications, respectively.118 Overall, the suggested goal of antihypertensive therapy is systolic pressure between 140 and 155 mm Hg and diastolic pressure between 90 and 105 mm Hg.118

Fluid management guided by CVP in severe cases has been demonstrated to improve urine output, maintain mean arterial pressure, and decrease diastolic pressure.119 If oliguria persists after normalization of CVP (usually between 2 and 3 cm H2O) or the physiologic state is complicated by pulmonary edema or cardiovascular decompensation, a pulmonary arterial (PA) catheter may be helpful. Emerging minimally or noninvasive technologies to assess cardiac output may also provide information during pregnancy2; however, their use should focus on identifying trends in hemodynamic parameters until further validation of these methods during pregnancy occurs, particularly in the presence of comorbid states. A cardiology consultation and an assessment of cardiopulmonary function with a transthoracic echocardiogram may assist with the diagnosis and management. The course of preeclampsia can be complicated by mild to severe coagulopathy even in the presence of a normal platelet count.120 For the benefit of both obstetric and anesthetic management, if the initial platelet count is less than an arbitrary 70 to 75/L–9, the clinical history and the results of additional studies, such as PT or PTT or thromboelastography, should be reviewed. If the low (>70-75/L–9) platelet count has been stable or trending slowly downward for 2 to 3 weeks and the patient has no clinical history of bleeding gums, prolonged bleeding, or significant bruising with trauma, a neuraxial approach to analgesia or anesthesia appears reasonable. However, if the platelet count has rapidly fallen within the 2 to 3 weeks or the clinical signs noted are present, a few options exist. In patients who will undergo labor, the analgesia can be managed with a patient-controlled IV pump; 13 mcg of fentanyl every 6 minutes with a lockout of 300 mg per 4 hours has been used with some success. Of note, intramuscular administration of opioids, a common method of analgesia used for labor, is not recommended because of the possibility of hematoma formation. If an instrumented or operative delivery is planned, additional laboratory testing, such PT or PTT and thromboelastography, may provide information on the extent of coagulation dysfunction. If thrombocytopenia or prolonged PT or PTT indicates that pooled platelets or fresh-frozen plasma may reduce the risk of maternal hemorrhage with delivery, placement of neuraxial techniques should await the administration of these products.

During labor, epidural analgesia offers the advantage of limiting pain or stress, thus reducing catecholamine release, decreasing maternal blood pressure, and indirectly increasing placental perfusion.119 Epidural anesthesia can also be a preferred technique for cesarean delivery because the dose of medications can be slowly titrated, resulting in more gradual blood pressure changes. Spinal anesthesia should not be avoided, particularly in urgent or emergent cases where rapid onset of anesthesia is important. Limited studies suggest that the incidence of hypotension is not significantly different compared with epidural anesthesia for cesarean delivery.82,122 A CSE technique with a small initial spinal dose (7.5 mg of bupivacaine) followed by sequential epidural catheter dosing is another method that may produce rapid anesthetic onset with less profound hypotension; however, the value of this technique in limiting hypotension has not been validated in randomized controlled trials. Overall, neuraxial techniques represent an optimal approach to analgesia and anesthesia in the preeclamptic patient. This is particularly true when assessing awake, nonsedated patients during labor and delivery for the severity of disease and avoiding the risks of general anesthesia associated with airway narrowing that accompanies pregnancy, labor, and preeclampsia123 and the increases in systemic and intracranial pressures that can occur during intubation and extubation.

Intravascular hypovolemia associated with preeclampsia, use of antihypertensive medications, and administration of magnesium for seizure prophylaxis may augment the hypotension produced by neuraxial techniques. When responding pharmacologically to hypotension, restraint is advocated because patients with hypertensive disorders may have an exuberant response. Small doses of vasopressors (ie, 5 mg of ephedrine or 20-40 mcg of phenylephrine) should be given initially. Similarly, the response to hypertension associated with the disease or reactive hypertension from labor pain, intubation, or emergence from general anesthesia should be treated judiciously. Labetalol (5-10 mg IV) is a popular first-line agent that has a relatively wide margin of safety and can be doubled every 20 minutes until an effect is observed or 150 to 200 mg has been reached. At these thresholds, other agents such as hydralazine or calcium channel blockers can be used. Infusions of nitroglycerine, nitroprusside, and trimethaphan can be initiated, but arterial monitoring should be used to more carefully titrate the effect (see section Invasive Monitoring in the Parturient).

Invasive Monitoring in the Parturient

Whereas noninvasive measurement of blood pressure, heart rate, oxygen saturation, urinary output, and fetal cardiotocography is standard practice in most labor and delivery facilities, the use of invasive monitors is variable and controversial. Despite practice guidelines written by a number of professional organizations, including the joint task force of the American College of Physicians, the American College of Cardiology, and the American Heart Association,124 poor collection and incorrect interpretation of hemodynamic data from invasive monitors remain the key problems with their use.125,126

In addition to correctly interpreting the data produced, knowing when to use invasive monitoring is a vital clinical skill. The indications for invasive arterial blood pressure monitoring during pregnancy include the desire to more carefully manage blood pressure, lack of reliable noninvasive cuff measurements, need for vascular access for blood studies, and planned use of certain hemodynamic agents (particularly drugs given by infusion, such as nitroglycerin and nitroprusside). By contrast, the indications for invasive central monitoring are not as clear or uniformly accepted. A CVP catheter is often placed to yield an approximation of volume status (or to follow a trend in blood loss or replacement therapy) and to give a greater understanding of the mechanical phases of the cardiac cycle. Management of oliguria unresponsive to a fluid challenge, pulmonary edema, and refractory hypertension are clinical situations in which some clinicians desire CVP monitoring.

Although a PA catheter can assist in determining the etiology of pulmonary edema, oliguria with normal CVP, or cardiovascular failure, its use is the most controversial. Advocates of PA catheter use suggest that it can provide information on left and right ventricular function, systemic vascular resistance, and cardiac output. Detractors question the validity of the data, noting that in the setting of preeclampsia, for example, the correlation between CVP and pulmonary capillary wedge pressure is unreliable for CVP readings greater than 6 cm H2O.127 In deciding between a PA versus CVP catheter, the clinician should recognize that although the insertion-related complications are similar,128 the PA catheter is associated with more use-related complications, including balloon rupture, pulmonary infarction, valvular damage, and erosion of the PA. Thus, the benefits of PA catheter use should clearly outweigh its inherent risks before its use can be recommended. The 2007 practice guidelines of the American Society of Anesthesiologists Task Force on Obstetrical Anesthesia state that "the decision to perform invasive hemodynamic monitoring should be individualized and based on clinical indications that include the patient's medical history and cardiovascular risk factors."43 To date, although PA catheter use has been reported in parturients (primarily with cardiac pathology or pulmonary hypertension), their use has been questioned.129 No controlled trials are available that confirm the benefit of PA catheter monitoring on maternal or fetal outcome. PA pressures are observed with different etiologies of pulmonary edema and oliguria (Boxes 62-5 and 62-6).130,131 Renal and postrenal etiologies of oliguria, such as renal artery vasospasm, acute tubular necrosis, and postrenal obstruction, are less commonly encountered in the obstetric population. Future modalities for hemodynamic monitoring, such as Doppler ultrasonography and three- and even four-dimensional echocardiography, are able to provide detailed, dynamic information on cardiac structures and function and in the future may offer significant clinical advantages.132

Although many of the procedures in gynecologic surgery are approached using standard surgical techniques, the care and anesthetic management should be provided with an understanding of gender-related differences that ultimately may affect patient outcomes and satisfaction. In addition to the many alterations discussed in the obstetric section of this chapter, gender-related changes in the sensitivity to pain and anesthetic agents are relevant to each case. Full appreciation should be given to the highly vascular uterus and other visceral structures found in women, which can result in sudden and profound blood loss; air emboli; and in pregnancy-related procedures involving the pregnant or peripartum state, amniotic fluid emboli.

Preoperative Assessment and Evaluation

A few elements in taking a gynecologic history deserve emphasis, particularly because a few weeks may have lapsed between the gynecologic surgeon's assessment and the surgical date. The menstrual cycle can serve as a guide to other pathology and rule out the possibility of pregnancy. Abnormal or prolonged uterine bleeding can be produced by a variety of endocrine and metabolic disorders, including hypothyroidism, hyperprolactemia, coagulopathies, and insulin metabolism disorders, which in turn may impact anesthetic care. Because pregnancy has implications on surgical interventions and anesthetic care, testing should be used in individuals with absent or irregular menses, unreliable knowledge of menstrual cycle or contraceptive use, and noncompliance with hormonal birth control regimens or if the report is desired. Algorithms for the use of serum and urine beta hCG pregnancy tests are helpful if applied appropriately (Fig. 62-5). The serum test uses a radioimmunoassay that can detect a pregnancy within 24 to 72 hours after conception at levels as low as 1 to 3 mIU/L.133 By contrast, the urine test uses an antibody agglutination methodology that detects a level greater than 25 mIU/L, which is achieved only after 10 to 12 days.133 A positive serum hCG combined with a positive uterine ultrasound result (demonstrating decidual thickening of the uterus) can diagnose pregnancy with 100% clinical accuracy.

The psychologic impact of the surgical condition should be considered and managed with sensitivity. Fear, anxiety, embarrassment, and even guilt may be associated with some procedures. Infertility patients may exhibit a number of emotions as they undergo an escalating series of tests, medications and procedures, including tubograms, laparoscopies, laparotomies, tubal reconstructions, and in vitro fertilization. Patients who have spontaneous, missed, or therapeutic abortions may have feelings of guilt or mourning. Patients with chronic pelvic pain may have concerns regarding complicated, multimodal pain therapies; such individuals often benefit from preoperative pain and psychiatric consultations. Patients with urinary or fecal incontinence may be acutely embarrassed by their condition. Patients with malignant breast or pelvic masses may have anxiety or fear of disfigurement and concern over loss of sexual function and desirability.

Patients who present for surgical management of gynecologic malignancies require additional considerations. The tumor mass may create anatomic and physiologic alterations, including aortocaval compression, respiratory embarrassment, changes in renal or hepatic function, and the potential for adhesions and scarring. The additional comorbidity of prior surgeries, chemotherapy, and radiation therapy must be considered as well. Chemotherapy may be associated with disruptions in hematopoiesis; infection resistance; nausea and emesis; and myocardial, renal, and hepatic function (Table 62-7). Anemia, coagulation disorders, and platelet dysfunction also may be present. Alternatively, malignancies may result in hypercoagulable states, and the impact of various regimens for prophylaxis and treatment should be considered in the perioperative period.134,135

Intraoperative Considerations and Management

Gender Differences in Sensitivity to Pain

Gender differences in biologic, psychologic, and sociocultural factors are believed to be responsible for women reporting pain that is more severe, frequent, and of longer duration than that experienced by men.136 Although gender role expectations may be partially responsible for these observations, female gonadal hormones have been associated with pain sensitivity, albeit contradictory to most expectations. Female hormonal increases, as occur during pregnancy, have been associated with decreases in response to noxious stimuli. By contrast, hormonal decreases, such as those witnessed in menopause, have been associated with increases in pain sensitivity.137 Although progesterone previously was demonstrated in animal and human studies to be the female gonadal hormone most responsible for modulating pain,138 the demonstration of an inverse relationship between estrogen and β-endorphins and estrogen receptors in the noxious stimuli processing areas of the brain and spinal cord suggests a greater role for estrogen. Acute estradiol exposure decreases the number of opioid binding sites; reduces the antinociception effect produced by morphine in ovariectomized rats; and diminishes the plasma, pituitary, and hypothalamic levels of β-endorphin.138,139 In human clinical models, high estrogen levels alter noxious stimuli processing,140 a finding that may be relevant to therapies that involve estrogen replacement or manipulation.

Gender-related differences in pain from the surgical exploration of abdominal and pelvic organs also may stem from the more complex anatomy and function of the female reproductive organs. The relative contributions of somatic and visceral sensory fibers to pain originating from the pelvic, uterine, cervical, and perineal structures have not been completely characterized. Investigations into visceral afferent contributions to pain have been particularly abbreviated because of the lack of suitable experimental models and noninvasive neurophysiologic techniques. Recent and future work, however, promises to more fully elucidate the contribution of female reproductive organs to gender-related pain.141

Gender Differences in Sensitivity to Anesthetic Agents

Gender-related pharmacokinetic and pharmacodynamic alterations are produced by the greater percentage of body fat and the smaller body water content in females. In general, this results in a greater distribution per kilogram of body weight for lipophilic drugs, such as opioids and benzodiazepines, and a smaller distribution for water-soluble drugs, such as muscle relaxants.142 Because the volume of distribution is the most important pharmacokinetic factor responsible for initial drug concentrations, the response to induction and bolus administration agents may be altered. Drug clearance, which is dependent on metabolism and excretion and is related to steady-state concentrations, also is affected by gender. Hepatic metabolism, which accounts for a major route of elimination of most IV anesthetic drugs, has gender-related alterations within the cytochrome P450 (CYP) and uridine diphosphate–glucuronosyltransferase systems (Table 62-8). Glomerular filtration rate, the most important renal parameter for excretion of nonactively secreted or reabsorbed drugs, is lower in females, but the impact of this change is not well characterized.142

Hormonal alterations from the use of contraceptive pills, in vitro stimulation regimens, pregnancy, menstrual cycles, and menopause may modify CYP enzyme activity. Although clearance of drugs may be higher in the middle of the menstrual cycle,143 minimal to no menstrual phase variations have been noted with the disposition of certain anesthetic drugs, including alfentanil, alprazolam, and midazolam.144,145 Menopause has been associated with decreases in midazolam and alfentanil clearance; however, this phenomenon is not entirely hormonally mediated because hormonal replacement does not return clearance to premenopausal levels.146 Faster emergence from propofol anesthesia in women likely is related to a rapid decline in plasma levels147; whether this condition is attributable to elimination or intercompartmental distribution remains unclear. The analysis is further complicated by the greater sensitivity of women to given plasma concentrations of propofol.147 These changes demonstrate that the effect of gender on pharmacokinetics and pharmacodynamics is a multimodal issue for which more information is needed.

Anesthetic Selection and Care

Performing a history and physical examination; reviewing the chart, previous anesthetic records, and relevant testing; and discussing the overall plan with the surgeon are essential steps in selecting an appropriate anesthetic plan. This is particularly true given the variety of positioning requirements and surgical approaches for certain gynecologic procedures (eg, abdominal, laparoscopic, vaginal hysterectomy).

All patients, including those who received local anesthesia, should be monitored with ECG, blood pressure cuff, and pulse oximeter. Additional monitors include a capnography sampler, temperature probe, peripheral nerve stimulator, and Foley catheter as appropriate. Invasive monitors, such as an arterial catheter, central venous catheter, PA catheter, or transesophageal echocardiography probe, may be indicated in patients with serious medical problems or who are undergoing radical, prolonged procedures accompanied by extensive fluid shifts and volume replacement.

Monitored IV sedation, often used with a local anesthetic field block, is often appropriate for certain procedures, such as dilation and curettage (D&C), hymenotomy, and breast biopsy. IV sedative and analgesic medications may be beneficial before placement of the field block, particularly when the block is administered to the paracervical or perineal region. Because the cervix is highly vascular, field blocks in this region can result in high plasma local anesthetic concentrations, so vigilance should be given to signs of toxicity.

Neuraxial techniques are suitable for many operations, including conservative abdominal and pelvic procedures. However, the duration of the case, requirements for Trendelenburg position, and unanticipated need for extensive exploration may limit the use of spinal and epidural anesthesia. The selection of local anesthetics and the specific neuraxial technique depend on the magnitude and duration of the operation; however, a T4 to T6 level is advised for intra-abdominal surgery. Prophylactic antiemetic and supplementary opioid use may prevent the nausea and discomfort that result from peritoneal stimulation. Catheter-based techniques, as opposed to single-dose techniques, offer the most control and flexibility. When provided as part of a CSE technique, a short-acting spinal anesthetic can be given for procedures of potentially short but unknown duration. The catheter then can be used if the duration of the operative event is longer than anticipated or postoperatively for analgesia is appropriate. Whether these catheters should be placed intrathecally or epidurally is controversial. Microcatheters, which historically were passed through standard 25- to 32-gauge needles into the intrathecal space, were associated with cauda equina syndrome when used with 5% lidocaine in 7.5% dextrose. Speculation for this outcome has been placed on drug "pooling" by the nerve roots within the subarachnoid space. These outcomes were associated with clinical abandonment of these catheters in the United States but not in Europe. Since that time, slightly larger microcatheters, which pass through a 22- to 26-gauge spinal needle, have been evaluated. Microcatheters are believed to contribute to lesser risk for PDPH than standard macrocatheters (20-gauge) placed through a 17-gauge Tuohy or Weiss needle used in similar fashion. The combination of general anesthesia and an epidural catheter, whether used for intraoperative anesthesia or postoperative analgesia, can be advantageous for particularly large or painful procedures.

General anesthesia is best suited for procedures that require extensive abdominal dissection, steep Trendelenburg positioning, extended CO2 insufflation for laparoscopy and pelviscopy, or deep levels of anesthesia for a short period of time. Although mask and LMA devices are often used, endotracheal intubation remains the conduit of choice for ventilation and anesthesia when pulmonary soiling is a risk. These cases include patients with suspected gastric contents (a "full stomach"), obesity, severe anxiety, nausea, or vomiting; surgical cases that will result in an aggressive Trendelenburg position or massive fluid shifts; and cases in which emergent exploration is required. Overweight or obese patients are increasingly prevalent even within younger age groups. The National Health and Nutrition Examination Survey found that obesity is becoming more common at younger ages and more prevalent with age.148 Among nonpregnant women 20 to 39 years of age, the prevalence of obesity (BMI >30) is 34%.148 If instrumentation of the airway presents a concern, alternative anesthetic options and the difficult airway algorithm should be invoked. An elective, awake fiberoptic intubation in a controlled environment with adequate assistance is often the optimal approach.

Considerations for Specific Situations

In general, gynecologic surgery can be divided into four major categories: perineal, transvaginal, intra-abdominal, and transabdominal (Box 62-7). Anesthetic management for these procedures depends on a number of factors specific to the procedure, patient, and health care providers.

Perineal and Urologic Surgery

Anatomy

The vulva includes all of the structures visible externally from the pubis to the perineum, including the mons pubis, labia, clitoris, vestibule, urethra, and Skene and Bartholin glands. The primary blood supply to the vulva is via the internal pudendal artery, a branch of the internal iliac artery. The nerve supply is via the pudendal nerve that arises from the sacral nerve roots (S2, S3, and S4; Fig. 62-3). The pudendal nerve, artery, and accompanying veins pass from the pelvis via the lesser sciatic foramen and along the lateral wall of the ischiorectal fossa. The pudendal nerve can be readily blocked through a transperineal or transvaginal approach with local anesthetic placed posterior and medial to the ischial tuberosity;149 this block can be used in obstetrics to provide analgesia during a vaginal delivery or perineal repair. The lymphatic drainage of the vulva is principally through the superficial inguinal lymph nodes to the deep inguinal and pelvic nodal systems.

Specific Procedures

Although a number of minor vulvar procedures are routinely performed under local anesthesia, most procedures performed in the operating room require regional or general anesthesia. Such procedures include biopsies, hymenectomies, drainage of Bartholin glands, and laser fulguration of intraepithelial neoplasia.

Surgical interventions to treat stress urinary incontinence in women include procedures to reestablish the posterior urethrovesical angle and resuspend the urethra. Traditional approaches include retropubic (eg, Marshall-Marchetti-Krantz or Burch procedures) and transvaginal approaches (eg, Kelly plication or Pereyra and Stamey urethropexy). Most of these procedures involve suturing the vaginal epithelium to the rectus fascia above the pubis. During placement of the paraurethral suture, the patient must not cough or strain. Neuraxial anesthesia, usually in the form of a spinal technique, provides a quiescent surgical field and good postoperative conditions. Prophylactic use of antiemetics (10 mg IV of metoclopramide, 4 mg IV of ondansetron, and 8 mg IV of dexamethasone) is recommended.

Major vulvar procedures, including operations for trauma or invasive carcinomas, often require extensive dissection into the tissues of the inferior fascia of the urogenital diaphragm, pelvis, and abdomen. These procedures frequently result in major blood loss from the vestibular bulbs, pudendal artery, and retropubic space of Retzius. Preparation for these cases should include use of large-bore IV catheters, immediate availability of resuscitation equipment and fluids, and use of invasive monitoring and blood products where appropriate. Anesthetic management that includes epidural catheter-based techniques allows for minimization of intraoperative general anesthetic agents and provision of superior postoperative analgesia. Patients with significant cardiac or pulmonary comorbid conditions, obesity, a potentially difficult airway, or an expectation for significant blood loss may benefit from induction of general anesthesia at the beginning of the case when the intubation can be achieved in a controlled, stable environment.

Special Considerations

Use of operative lasers entails risks to the patient and the operating room staff through thermal and retinal injury from reflected light, ignition of operative drapes, and possible viral inoculation from inhalation of laser plume particulates. Human papilloma viral DNA has been found in laser plumes, but whether this represents an infectious risk is unclear.150 Regardless, the smoke contains bioaerosols that can cause lung irritation and other potentially adverse effects.150 Therefore, appropriate eye protection, occlusive laser masks, and properly functioning smoke evacuators are necessary. For patient safety, surgical site immobilization is of great importance. Dense regional anesthesia or general anesthesia with ventilation by mask, LMA, or endotracheal intubation are reasonable approaches.

Transvaginal Surgery

Anatomy

The vagina is an 8- to 10-cm compliant musculomembranous canal that extends from the external genitalia to the uterine cervix. Anteriorly and posteriorly related to the urethra and bladder, respectively, the vagina is in close proximity to the rectal ampulla, perineum, and cul-de-sac of Douglas. The primary blood supply to the vagina is derived from branches of the uterine and pudendal arteries. Whereas lymphatic drainage of the upper third of the vagina is predominately to the parametrial and pelvic lymph nodes, the lower two-thirds share the superficial inguinal lymph nodes with the vulva. The sensory nerve supply to the vagina arises from S2, S3, and S4 via the pudendal nerve. The sympathetic and parasympathetic nerve supplies originate from the hypogastric plexus (L1-L3) and sacral nerves, respectively (see Fig. 62-3).

The cervix enters the vagina at a variable angle through the anterosuperior wall and is composed of myometrial muscle and dense stroma. The blood supply is derived from the descending branch of the uterine artery, and lymphatic drainage is through the paracervical nodes. Innervated by the nerves arising in the hypogastric plexus, the exocervix is poorly supplied by sensory nerves and thus are relatively insensate. By contrast, the endocervix has an abundant nerve supply and is very sensitive to surgical manipulation.

Specific Procedures

Dilation and curettage requires dilating the cervix and mechanically scraping or suctioning the uterine walls to obtain tissue for evaluation, perform an abortion, or investigate abnormal uterine bleeding. Frequently performed in an office setting, D&C procedures should be performed in an operative setting in patients with significant comorbid conditions, distorted anatomy, or an inability to tolerate an office procedure. The major surgical risk of the procedure is uterine perforation and subsequent hemorrhage, particularly when the perforation occurs through the lateral wall and involves the uterine artery. Preexisting acute or chronic anemia may exacerbate the patient's condition. If a perforation is suspected, gentle probing to localize the defect, observation, and laparoscopy or laparotomy may be needed for surgical repair.

Dilation and evacuation (D&E) and dilation and extraction (D&X) are similar to D&C but usually are performed to interrupt pregnancy. From gestational week 16, fetal size and structure dictate the mechanical disruption and then evacuation of fetal tissue. Extraction involves evacuation of intracranial contents after delivery of the fetal body through the dilated cervix to minimize uterine or cervical injury. Because these procedures disrupt fetal and placental tissue, amniotic fluid emboli, DIC, and uterine atony accompanied by maternal hemorrhage can follow.151 Procedures being performed for an in utero fetal demise warrant coagulation studies, particularly if associated with an abruption or uterine dehiscence; however, a dead fetus per se does not result in coagulopathies for a period of days to weeks.152,153 Complication rates correlate with the gestational age of the fetus and the experience of the surgeon. D&E procedures are also performed in patients with hydatidiform moles or persistent gestational trophoblastic tissues, which are neoplastic conditions resulting from deranged placental growth. Such pregnancies are associated with vaginal bleeding, anemia, and the need for subsequent chemotherapy.154

D&C, D&E, and D&X procedures often are performed with a paracervical block with the assumption that a uterine perforation would be accompanied by sudden, acute report of abdominal pain, but this has not been validated. Spinal and general anesthesia are viable options with the notation that volatile halogenated anesthetics, including sevoflurane and desflurane, have a dose-dependent association with uterine atony in in vitro experiments.155 No clinical differences in blood loss with volatile agent administration in doses up to 1 MAC have been observed. Moreover, oxytocin appears to successfully diminish these volatile effects up to 1.5 MAC.155 A number of uterotonic agents, such as methylergonovine and prostaglandin F2α, also can be used to augment uterine tone (see Table 62-4).

Diagnosis and therapy for preinvasive or invasive cervical lesions is often achieved with a cone biopsy, which provides concentric excision of both exocervical and endocervical stroma. Because the cervix is well vascularized, bleeding is common, especially in pregnant patients. Hemostatic sutures can be placed laterally in the descending cervical branches of the uterine artery. Dilute solutions of vasopressin (20 units in 20 mL of normal saline) or epinephrine (1:200,000) can be injected locally into the cervix to induce vasospasm; both of these agents may induce hypertension. Resulting hypertension that is severe and sustained may require a direct-acting vasodilator such as hydralazine; β-adrenergic blocking agents are less effective. Most cone biopsies are performed as day surgery procedures under spinal or general anesthesia. A mask or LMA technique can also be used with spontaneous or assisted ventilation.

Rigid or flexible hysteroscopic procedures are performed to evaluate the endocervix or endometrial cavity. The scope is inserted through the cervix into the uterine cavity. CO2 or liquid then is used to distend the uterus for improved visibility and surgical access. Isoosmolar, nontoxic, nonconducting distending mediums, such as glycine, dextrose, sorbitol or mannitol, and saline, are used, and accurate accounting of the volume used and returned are essential to minimize water intoxication, hyponatremia, and ammonia toxicity. Diagnostic examinations for evaluation of unexplained fertility or abnormal uterine bleeding are performed with minimal cervical dilation using small-caliber devices that are placed under a paracervical block. By contrast, operative procedures, such as ablation or resection of intracavity uterine lesions, septae, or adhesions, are performed with larger-caliber devices capable of electrocautery, wire loop cutting, or lasering and necessitate a neuraxial or general anesthetic.

Vaginal hysterectomies are performed for benign conditions or early-stage malignancies of the uterus and cervix. They also are used in patients with loss of pelvic support associated with uterine prolapse. Excessive uterine size, prior abdominal surgery, and suspicion of intrapelvic malignancies all are contraindications to a vaginal approach. The procedure requires entry into the anterior and posterior culs-de-sac to expose the broad ligament containing the uterine artery and can be performed in association with cystocele or rectocele (bladder or rectal prolapse, respectively) repair or an urethropexy (see section Perineal and Urologic Surgery, Specific Procedures). The ovaries may be conserved or removed vaginally. These procedures can be performed under a hyperbaric spinal anesthetic at a T6 to T8 level to block the peritoneal sensation of uterine traction (see Fig. 62-3). If significant Trendelenburg positioning and laparoscopy-assisted techniques will be used, a general anesthetic with endotracheal intubation is recommended.156

Special Concerns

The majority of transvaginal procedures are performed in the lithotomy position. Excessive hip flexion, abduction, and external rotation may allow the inguinal ligament to apply continuous pressure on the femoral nerve157 or place the obturator and lateral femoral cutaneous nerves in a position where they are prone to stretch injury.158 Extensive rotation of the thighs at the hip or extension of the legs without knee flexion may result in sciatic and peroneal nerves injury.157 Compression of the lateral fibular head results in common peroneal nerve injury, which can result in foot drop and lateral lower extremity paresthesias.157 Protective padding, avoidance of contact with hard surfaces or supports, and attention to positioning are important elements of optimal care.159

The Trendelenburg position is often used in transvaginal procedures to assist with surgical visualization. This position is associated with potentially severe consequences, including venous air emboli, alterations in circulation and respiration, and upper extremity peripheral nerve injuries.156,159 When combined with laparoscopy, further hemodynamic and respiratory encroachment may occur.156

Use of distending mediums for hysteroscopy may result in absorption of large volumes of irrigating fluid, leading to hypervolemia, hyponatremia, and decreased osmolarity. Together, these alterations may produce hypertension, bradycardia, altered mental status, nausea, vomiting, headache, agitation, and lethargy. These symptoms are masked if general anesthesia is used. If the resulting "hypoosmolar hyponatremia" is not recognized, seizures, coma, and death may occur. Treatment includes halting or rapidly completing the surgery; sending blood for a complete blood count, electrolytes, and osmolality; and administering normal saline and furosemide. Although severe hyponatremia (<120 mEq/L) has a significant association with mortality, correction with hypertonic saline (3% NaCl) should occur no faster than 1 to 2 mEq/L/h with a goal of 125 to 130 mEq/L. Overly rapid correction can lead to central pontine myelinolysis, with paresis, mutism, pseudobulbar palsy, and other neurologic disorders.160,161

Intra-Abdominal Operations

Anatomy

Intra-abdominal operations relate mostly to the vagina, uterine cervix, uterus, fallopian tubes, and ovaries. On occasion, especially when associated with sepsis or tumor invasion, the rectum and bladder are involved through fistulous communications. The blood supply to the pelvis is largely derived from the internal iliac (hypogastric) artery, which in turn gives rise to the uterine arteries; the superior, middle, and inferior vesical arteries; the middle and inferior hemorrhoidal arteries; and the vaginal arteries. The extensive collateral circulation network to organs within the pelvic viscera alternatively allows extensive bleeding during pelvic dissection or obstetric hemorrhage as well as the possibility of ligating major arteries, including the internal iliac, with few untoward effects.

The pelvic organs are innervated by sympathetic fibers derived predominately from the first through fourth lumbar nerves (L1-L4) and enter the hypogastric or presacral plexus (see Fig. 62-3). The presacral sympathetic plexus serves the uterine fundus, cervix, vagina, and excretory organs, including the rectosigmoid region of the colon, anus, bladder, and urethra. Parasympathetic preganglionic fibers arise from the second through fourth sacral nerves (S2-S4). Sensory nerves from the pelvic viscera, including the uterus, arise from the T10 to L4 spinal cord segments. By contrast, the cervix is served by nerve fibers from the S2 to S4 spinal cord segments. Lymphatic drainage of the female reproductive organs is predominately through the pelvic and paraaortic lymph nodes in the retroperitoneum, although the superficial and deep inguinal lymph nodes may be involved as well.

Specific Procedures

Ovarian surgery is performed for a variety of conditions, including removal of cystic masses, endometrial lesions, and neoplastic tissues. Ovarian carcinomas are the most lethal of all gynecologic malignancies because of their ability to grow silently until the disease is advanced and widespread.162 With extensive ovarian cancer, subdiaphragmatic lymphatic obstruction often results in profound ascites that may impair diaphragmatic excursion, impede venous return, and delay gastric emptying. Cytoreductive procedures, which remove all visible tumor masses to improve the response to chemotherapy, can include extensive retroperitoneal dissections with bowel resections and bypasses.

Surgery of the fallopian tubes is performed most often for nonneoplastic processes; both benign and malignant neoplasias are rare. Salpingoscopies are becoming more common because of their association with infertility evaluations.163 Tubal ectopic pregnancies, which occur in approximately 1 of 100 pregnancies, are associated with pelvic inflammatory disease, intrauterine device use, diethylstilbestrol exposure, and prior tubal procedures or pathology.164 Ectopic pregnancies may be located throughout the fallopian tube, including the uterine anastomosis; the pregnancy is surrounded by myometrial uterine tissue at this site and may grow significantly before becoming symptomatic. Ectopic pregnancies may rupture without warning, leading to acute hemoperitoneum and massive exsanguination. Management should center on providing rapid fluid resuscitation, securing the airway, and preparing for massive blood transfusion and immediate surgery. Procedures for removing ectopic gestations are time consuming because hemostasis may be difficult to obtain. On occasion, particularly if the ectopic gestation is implanted near the uterus, a salpingectomy and hysterectomy may be required.

Tuboovarian abscesses are managed surgically when they are larger than 8 cm, nonresponsive to antibiotic therapy, or potentially ruptured. Ruptured tubo-ovarian abscesses may be accompanied by peritonitis, septic shock, respiratory distress, and coagulopathies. Surgical management of intact abscesses includes percutaneous or laparoscopic drainage. However, a laparotomy with a salpingo-oophorectomy and hysterectomy may be necessary, particularly when associated with a rupture or extensive pelvic inflammatory disease.

Uterine leiomyomas (fibroids) are the most common benign tumor in women and may be associated with menometrorrhagia; ureteral obstruction; pain; infertility; and, rarely, pregnancy loss. Usually well-circumscribed but nonencapsulated, fibroids occur in the submucosal, intramural, or subserosal layers (innermost to outermost layers, respectively) of the uterus. Patients often are placed preoperatively on leuprolide, a gonadotropin-releasing hormone agonist, in an attempt to reduce the size of the fibroids. Myomectomies can range from straightforward hysteroscopic procedures of pedunculated subserosal fibroids to prolonged dissections of intramural fibroids accompanied by extensive bleeding. Vasospastic solutions of vasopressin or epinephrine are sometimes injected directly into the myometrium to reduce blood loss. Myomectomies can be performed under regional or general anesthesia.

Uterine reconstructive surgeries are performed for congenital malformations of the uterus and include removal of uterine septa or reunification of duplicate uterine horns. Most are performed to enable fertility or gestation.

Abdominal hysterectomies, which include subtotal (supracervical), total, and radical types, are performed for a variety of benign and malignant diseases. Common indications include symptomatic uterine fibroids, pelvic pain, and endometriosis. Acute inflammatory disease, endometriosis, and malignancies may result in extensive adhesions, increased vascularity, and destruction of normal tissue planes. These alterations prolong surgery and increase blood loss. Because a steep Trendelenburg position is often required for these operations, general anesthesia with endotracheal intubation is used.

Special Considerations

Although vertical and transverse approaches can be used for intra-abdominal surgeries, the low transverse incision is selected when possible for its cosmetic acceptability and strength of repair. The Pfannenstiel incision, the most common approach for cesarean delivery, often is modified to include dissection of the rectus abdominis (Maylard or Cherney incisions) for improved access to the lateral margins of the pelvis. When access to the upper abdomen is required, vertical midline or paramedian incisions are used. Such incisions are avoided, when possible, because the intrinsic strength and structural integrity of the repair are less robust, and respiratory splinting may occur.

Blood loss in gynecologic surgery may be precipitous and unexpected, although such cases often can be anticipated. Additional vascular access; invasive monitoring; and blood conservation techniques, such as erythropoietin-induced red cell production, autologous donation, and acute normovolemic hemodilution, should be considered in advance.165,166 Because preoperative autologous donation is limited by the maximum life span of stored blood, collection must occur within 6 weeks of the planned operation, with an average unit collection interval of 3 to 7 days.166 Although the use of blood cell salvage technologies remains controversial, particularly in the presence of malignancies, recovery of 2 to 3 units of blood has been deemed to be cost effective.166 Moreover, the irradiation of blood cells retrieved intraoperatively has been demonstrated to eliminate cancer cells.167 Most recently, the placement of prophylactic balloon catheters in major vessels by interventional radiologists may allow for timely control or embolization of intraoperative bleeding, particularly from the uterus.

The extent of surgery for gynecologic malignancies often depends on the clinical staging of the disease, the presence or absence of lymph node metastases, and an examination of involved tissues by a surgical pathologist. The gynecologic surgeon and the anesthesia provider should discuss the likelihood of progression to a more radical surgery before and during an operation. Such discussions help guide decisions about placement of invasive monitoring catheters, use of large doses of opioids and neuromuscular blocking agents, and selection of an anesthetic technique that is inappropriate for the duration and surgical exposure necessary for the case. On occasion, if the malignancy is confined to the pelvis without fixation to the pelvic sidewall, a pelvic exenteration is performed. This massive procedure involves radical hysterectomy, cystectomy with urinary diversion, and proctocolectomy with a permanent colostomy. Major fluid and electrolyte shifts, blood and heat loss, and coagulopathies can occur. Low-flow or closed-circuit volatile agent techniques and use of passive humidifiers, heating blankets, and fluid warmers are encouraged. A combined epidural–general anesthetic technique offers the benefits of a sympathetic blockade during the surgery and optimal analgesia postoperatively. Epidural analgesia is a particularly effective technique for reducing pain after intra-abdominal procedures. With the exception of a herniotomy, use of incisional local anesthesia is not consistently effective for reducing postoperative pain.168

Transabdominal Surgery

In distinction to open surgical procedures, transabdominal surgery occurs through small incisions with rigid or flexible scopes and instrumentation; an increasing number of these procedures are performed with robot-assisted technologies. Advantages of these procedures include smaller incisional sites, lower risks of wound complications, reduced postoperative pain and complications, and improved recovery.169 Disadvantages include poor visualization, injury to viscera and blood vessels, and complications from CO2 insufflation. In some cases, such as hysterectomies, vaginal approaches may be superior to laparoscopic approaches; however, both have benefits over open laparotomy.170

Although initially developed as a means for diagnosis, laparoscopy and pelviscopy are used routinely for a variety of operative procedures, including tubal ligation and repair, endometriosis fulguration, ovarian cyst aspiration and resection, ectopic pregnancy removal, and fibroid excision. Laparoscopic-guided carcinoma staging and resection procedures have been demonstrated to result in improved short- and long-term outcomes compared with open laparotomies.171 Most recently, "hand-assisted laparoscopy," which uses laparoscopy combined with a small incision for insertion of a hand, has shown increased utility and benefit over open laparotomy.172

Laparoscopy and pelviscopies are performed, often after catheterization of the bladder, with the surgeon placing a needle with a stopcock periumbilically through the fascial layers into the peritoneum. CO2 is insufflated through this needle to a pressure of approximately 19 mm Hg.

If the pressure increases rapidly, the needle may be inappropriately located between the fascial planes of the muscle layers and will need to be replaced. In the proper location and with the appropriate degree of abdominal distension achieved, the hollow needle is replaced with a trochar with a self-sealing opening for the laparoscope. The laparoscope then is placed and connected to an insufflator that provides gas (CO2) flows at a rate of 200 mL/min to maintain pressure.

Special Considerations

Although CO2 is a biologically produced gas and is nonflammable and rapidly absorbed, a number of consequences and complications may result from CO2 insufflation. During the routine practice of laparoscopy and pelviscopy, distension of the abdomen may cause a number of disturbances that have implications for the anesthesiologist (Box 62-8). Pressure on the diaphragm, coupled with the use of anesthetic agents, tends to impede respiration. If patients are breathing spontaneously, minimal to moderate respiratory acidosis and oxygen desaturation may occur. Use of controlled ventilation with increased minute volumes can compensate for increased CO2, however, higher inspiratory pressures are frequently observed, particularly in obese patients in the Trendelenburg position. Because sustained high plateau pressures can lead to bronchoalveolar damage, several changes may be necessary, such as modification of ventilatory settings to lower tidal volumes, release of some gas from the abdomen by the surgeon, and reduction of the degree of Trendelenburg positioning. Tension pneumothorax related to excessive inspiratory pressures can occur and must be ruled out if a sudden increase in inspiratory pressure is accompanied by decreasing oxygen saturations.

A massive CO2 embolus, although rare, is rapidly fatal unless recognized and treated immediately. The usual sequence is the onset of sudden and severe hypotension, arterial desaturation, and cardiovascular collapse shortly after placement of the insufflation needle or laparoscope. A "mill wheel" murmur throughout the cardiac cycle from gas in the right heart and pulmonary outflow tract has been reported; however, this is an unreliable sign. Capnography most likely will reveal a sudden decrease in expired CO2 because an acute increase in "physiologic" dead space, and fulminant pulmonary edema may occur. Treatment is largely supportive, with immediate discontinuance of CO2 insufflation, intubation (if not already part of the anesthetic technique), provision of 100% oxygen, and cardiovascular support. Placing the patient in a left lateral head-down position to trap the gas in the apex of the right ventricle rather than the pulmonary outflow tract (ie, Durant maneuver) is controversial. Placement of a central venous catheter into the right atrium to remove gas or air acting as a mechanical obstruction is also controversial. Fortunately, CO2 is highly soluble and rapidly cleared, and more favorable outcomes have been observed than with massive air emboli. If pulmonary edema develops, 5 to 10 cm H2O of positive end-expiratory pressure and use of IV furosemide may be helpful. If significant CO2 sequelae occur, the procedure should be rapidly terminated and the patient brought to an intensive care environment for continued observation and therapy.

Postoperatively, laparoscopy and pelviscopy have been significantly associated with postoperative nausea and vomiting. Moreover, laparoscopy may be a risk factor for superficial thrombophlebitis, deep venous thrombosis, and pulmonary embolism.173

The care and management of women undergoing obstetric and gynecologic surgery involves an appreciation of the physiologic, pharmacologic, and anatomic differences related to their gender or gravid state. Anesthesiologists should guide their practice according to these differences for optimal patient safety, outcomes, and satisfaction.

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