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
Innervation of the female reproductive organs.
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.
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.
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.
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
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.
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.
Box 62-3 ||Download (.pdf)
Analgesic Techniques During Labor and Delivery
- Psychologic preparation
- Emotional support
- Touch and massage
- Therapeutic heat and cold applications
- Vertical or alternative positioning
- Transcutaneous electrical nerve stimulation
- Acupuncture and acupressure
- Parenteral agents
- Opioids, opioids antagonist, and agonists
- Nonsteroidal antiinflammatory drugs
- Inhalation agents
- Nitrous oxide
- Volatile halogenated agents
- Neuraxial agents
- Local anesthetics
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.
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
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.
Table 62-3 Major Complications of Neuraxial Analgesia and Anesthesia ||Download (.pdf)
Table 62-3 Major Complications of Neuraxial Analgesia and Anesthesia
Transient Neurologic Syndrome
Cauda Equina Syndrome
Anterior Spinal Artery Syndrome
Signs and symptoms
Pain in lower back, buttocks, or both
Pain in low back with variable motor and sensory deficits
Pain in low back with motor weakness and sensory alterations
Painless loss of motor and sensory function
Pain in low back with variable motor and sensory deficits
Pain or pressure in low back with progressive motor or sensory blockade
Pain in low back that is tender on palpitation and accompanied by sensory or motor deficits and fever; may progress
With or without unilateral or bilateral radicular pain described as aching, burning, or cramping
Unilateral or bilateral radicular pain, sensory loss, particularly in the saddle region
Allodynia (heightened sensitivity to touch)
Preservation of vibration and joint position
Unilateral or bilateral pain that increases with activity
Unilateral or bilateral radicular pain
Unilateral or bilateral radicular pain
Bladder and bowel dysfunction
Bladder and bowel dysfunction
Bladder and bowel dysfunction
Bladder and bowel dysfunction
All contemporary local anesthetics
Ischemic compression by hematoma or abscess, or direct neurotoxicity, possibly caused by prolonged nerve exposure to high doses or concentrations of local anesthetics
Exact cause unknown; however, infections, abnormal immune reactions (eg, lupus), ischemia, and multifocal neurologic disease (eg, multiple sclerosis), and neuraxial techniques have been suggested
Hypotension, disruption of blood supply, vasoconstrictors or vasospasm
Disinfectants, local anesthetics, contrast media, blood, infections, vasoconstrictors, hemorrhage, multiple spinal surgeries
May occur spontaneously, after trauma, or after instrumentation; higher risk if abnormal coagulation status at time of instrumentation or catheter removal
Bacterial, immunocompromised patients are at higher risk; nonsterile techniques involving neuraxial technique
MRI or myelography
MRI and angiography
MRI or myelography
Neurologist or neurosurgeon
Neurologist or neurosurgeon
Neurologist and/or neurosurgeon
12-24 h after surgery
Acutely (hours to days) or subacutely (1-2 wk)
After insult whether surgical or traumatic
May occur years after the precipitating cause
Spontaneously, or 0–2 d after insult
2–7 d after instrumentation
Corticosteroids (limited data)
Corticosteroids (no clinical data), pain management, physiotherapy, exercise, psychotherapy
Correction of any existing hypotension, correction of vasospasm, physiotherapy, exercise
Pain management, physiotherapy, exercise, psychotherapy
Steroid injections and electrical stimulation may be helpful
Surgical decompression usually is indicated within 6–12 h of symptom onset
Intravenous antibiotics, percutaneous drainage, laminotomy with washout of epidural space, laminectomy
Limited clinical data
Within 2-12 wk of symptom onset and continue for up to 2 y; if no improvement within 3-6 mo, significant recovery unlikely
Variable, may have full, partial, or no recovery
No significant improvement with treatment; usually a chronic pain disorder that is not progressive
Variable and dependent on extent of neurologic involvement and treatment
Variable, dependent on extent of neurologic involvement and treatment
Symptoms last for 6 h to 7 d
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.
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.
Table 62-4 Medications Used to Augment Uterine Tone in Obstetric and Gynecologic Surgery ||Download (.pdf)
Table 62-4 Medications Used to Augment Uterine Tone in Obstetric and Gynecologic Surgery
|Medication||Uses||Route of Administration||Risks|
|Oxytocin||Induces labor, increases uterine tone||IV infusion; initial and additional doses of 0.3 IU (3 IU if prior oxytocin exposure) administered over 15 sec||Uterine hyperactivity; hypotension; reflex tachycardia; ADH-like response if given in high doses with risk of water intoxication; should be given in electrolyte-containing solutions, not dextrose in water|
|Methylergonovine||Increases uterine tone||IM 0.2 mg||Acute hypertension, seizures, cerebrovascular accidents, retinal detachment if given IV; use with caution in patients with coronary artery disease, essential hypertension, preeclampsia, atherosclerotic disease; nausea and vomiting may reflect direct CNS effect|
|Prostaglandin E2||Increases uterine tone||Oral, rectal, or vaginal; dose depends on desired effect||Nausea, vomiting, diarrhea, fever, tetanic uterine contractions, hypotension; hypertension|
|Prostaglandin F2α||Increases uterine tone||IM 0.25 mg||Nausea, vomiting, bronchospasm; tetanic uterine contractions; hypotension; hypertension|
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
Box 62-4 ||Download (.pdf)
Recommended Neuraxial Medication Combinations for Cesarean Delivery
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.
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
Extension of labor epidural analgesia for cesarean delivery. Onset (in minutes) for extension of T10 labor analgesia to T4 cesarean anesthesia. Note the values for chloroprocaine and bicarbonate (bicarb). [Based on data from Gaiser RR, Cheek TG, Adams HK, et al. Epidural lidocaine for cesarean delivery of the distressed fetus. Int J Obstet Anesth. 1998;7:27-31; Lam DT, Ngan Kee WD, Khaw KS. Extension of epidural blockade in labour for emergency caesarean section using 2% lidocaine with epinephrine and fentanyl, with or without alkalinisation. Anaesthesia. 2001;56:790-794.]
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
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).
Table 62-5 Characteristics of Early and Late Antepartum Hemorrhage Diagnoses ||Download (.pdf)
Table 62-5 Characteristics of Early and Late Antepartum Hemorrhage Diagnoses
Vaginal bleeding (+/– pain) >8 wk after last menstrual period
Slight tenderness to uterine examination
No adnexal mass
May not have vaginal bleeding
Pain <8 wk after last menstrual period
May present as shock with normal-sized uterus
Painless vaginal bleeding (although 10% may have coexisting, painful abruption)
Malpresentation of fetus (35%)
Difficulty palpating presenting part
Painful vaginal bleeding
Uterine irritability or tetany
Fetal distress or death
Vaginal bleeding (+/– pain)
Cessation of labor
Painless vaginal bleeding
Presence of fetal hemoglobin in shed blood
Painless vaginal bleeding
Mild bleeding that often resolves spontaneously
Often >37 wk of gestation
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.
Table 62-6 Assessment of Obstetric Hemorrhage ||Download (.pdf)
Table 62-6 Assessment of Obstetric Hemorrhage
|Severity of Shock||Findings||Blood Loss (%)|
|Mild||Tachycardia (<100 beats/min)||20-25|
|Moderate||Tachycardia (100-120 beats/min)||25-35|
|Hypotension (SBP 80-100 mm Hg)|
|Severe||Tachycardia (>120 beats/min)||>35|
|Hypotension (SBP <60 mm Hg)|
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
Box 62-5 ||Download (.pdf)
Diagnosis of Pulmonary Edema by Pulmonary Arterial Wedge Pressure
|Etiology||Pulmonary Arterial Wedge||Stroke Work Index|
|Left ventricular dysfunction||Increased||Decreased|
|Altered capillary permeability||Normal||Normal or increased|
|Low hydrostatic or oncotic pressure||Increased||Normal|
Box 62-6 ||Download (.pdf)
Diagnosis of Prerenal Oliguria by Pulmonary Arterial Wedge Pressures
|Etiology||Pulmonary Arterial Wedge Pressure||Left Ventricular Function||Systemic Vascular Resistance||Treatment|
|Sepsis||Low||Increased||Decreased||IV fluids, vasopressors, inotropes|
|Congestive heart failure||Increased||Decreased||Increased||Fluid restriction, diuretics, inotropes|