Chapter 53. Appendicitis in Pregnancy

A 20-year-old woman, G1P0 at 17 weeks' gestation, presented to the emergency department (ED) 10 hours ago complaining of right-sided abdominal pain accompanied by nausea and two episodes of vomiting. She is afebrile at present, blood pressure is 130/72 mm Hg, heart rate is 86 beats per minute (bpm), and respiratory rate is 20 breaths per minute. She weighs 198 lb (90 kg) and is 5 ft 7 in (169 cm) in height, with a body mass index (BMI) of 31 kg·m−2. She admits to right-sided tenderness to palpation localized to the inguinal region. She underwent an ultrasound evaluation by an obstetrician who did not find any cause for the pain related to her pregnancy. The general surgery service was consulted, and it is their opinion that the patient has appendicitis and will require a laparoscopic appendectomy.

Her pregnancy has been unremarkable up to this point and is otherwise healthy. She has had no previous anesthetics and no family history of anesthesia-related problems. She takes prenatal vitamins, denies any allergies, does not smoke or drink alcohol, and takes no drugs. Physical examination of her heart and lungs is normal. Her airway examination reveals a Mallampati Class IV airway with limited mouth opening, normal range of motion of head and neck, full dentition, and minimal mandibular protrusion. The thyromental distance is 5 cm and the hyomental distance is 3 cm. There are no other abnormalities in her history or physical examination.

53.2.1 What Is the Incidence of Appendicitis in Pregnancy?

Appendicitis has an incidence of approximately 1 in 1500 pregnancies, with appendectomy being the most common non-obstetric surgical procedure during pregnancy.1,2 The relative incidence is estimated to be 30% in the first trimester, 45% in the second trimester, and 25% in the third trimester3; and the most common predictor of fetal-maternal mortality is appendiceal perforation, with an estimated risk of 43%, and the risk of perforation increases with increasing gestation and delay in diagnosis.4,5 The estimated risk of fetal loss with appendiceal perforation is 36%.6

53.2.2 How Is Appendicitis Diagnosed during Pregnancy?

Anatomic and physiologic changes accompanying pregnancy make diagnosis of appendicitis challenging, therefore a careful history and physical examination, combined with a high index of suspicion, is required. The appendix is pushed superiorly and laterally with advancing gestation. However, according to studies, 84% of pregnant patients present with right lower quadrant pain.3,5 The usual clinical signs and diagnostic tests may be confounded by the physiologic and anatomic changes accompanying pregnancy. Ultrasound examination may be useful to identify a normal appendix and rule out other causes of abdominal pain in this patient population. However, due to the size of the uterus, it may be difficult to localize the appendix during the third trimester.4 Diagnostic imaging using helical CT scanning has been reported to have a sensitivity and specificity of 92% to 98% and 99% to 100%, respectively.7,8 Fetal radiation exposure with the helical CT scan approximates 300 milliradian (mrad) which is well below the 5 rad considered the maximal safe level of fetal exposure.9

53.2.3 What Are the Surgical Options for Appendectomy in Pregnancy?

There are two surgical options for performing an appendectomy. Appendectomy can be performed via either an exploratory laparotomy (open technique) or laparoscopic technique. The advantages of the open technique are thought to include possibly better direct visualization, decreased operating room costs, and reduced fetal exposure to carbon dioxide. The advantages of the laparoscopic technique include fewer wound infections, reduced postoperative pain and opioid use, reduced uterine handling, early return of GI function, reduced risk of ileus, earlier ambulation, and shorter hospital stay. The disadvantages of laparoscopic technique include potential uterine or fetal injury, reduced cardiac output and uterine blood flow, preterm labor, and fetal acidosis.9-11 Laparoscopic appendectomy is considered to be safe during any trimester.9 but pregnant patients should receive venous thromboembolism prophylaxis due to a risk of venous stasis secondary to carbon dioxide pneumoperitoneum.9

53.2.4 How Does Laparoscopy Impact Physiology in the Pregnant Patient?

The physiologic changes accompanying the pregnant state are reviewed in detail in standard obstetric anesthesia texts.12 Under normal circumstances, the creation of the pneumoperitoneum will impact cardiovascular and respiratory physiology. Carbon dioxide insufflation of the peritoneal cavity will initially result in an increase in venous return as intravascular blood volume is augmented by compression of the splanchnic vasculature. This results in an increase in cardiac output and arterial blood pressure. Sympathetic nervous system activation due to carbon dioxide absorption results in an increase in systemic vascular resistance.13 As intra-abdominal pressure increases beyond 15 mm Hg, venous return will decrease due to compression of the vena cava leading to a reduction in cardiac output and hypotension. Intra-abdominal pressures should be limited to 10 to 15 mm Hg.9 Insufflation may also result in bradyarrhythmias due to vagal effects from peritoneal stretching, or tachyarrhythmia due to sympathetic activation and hypercarbia. Aortocaval compression secondary to pregnancy may be exacerbated by the elevated intra-abdominal pressure and may compromise uterine and placental perfusion. Patients should be positioned with left uterine displacement to maximize uterine perfusion. Respiratory system changes due to the pneumoperitoneum will decrease pulmonary and thoracic compliance and increase peak inspiratory pressures. Elevation of the diaphragm will further reduce the functional residual capacity, possibly leading to hypoxemia. Carbon dioxide absorption may produce respiratory acidosis. These changes may lead to fetal compromise as a result of hypotension, hypoxemia, and fetal acidosis. Other sources of respiratory complications include subcutaneous emphysema, pneumothorax, endobronchial intubation, and gas embolism.14

53.3.1 What Are the Anesthetic Options for Laparoscopic Appendectomy?

Laparoscopic procedures can and have been carried out under general anesthesia and regional anesthesia.13 While regional anesthesia, such as epidural or spinal techniques, may be used for the laparoscopic procedure, they are not recommended in the pregnant patient, as the pneumoperitoneum, increased intra-abdominal pressures, and gravid uterus will compromise spontaneous ventilation causing hypercarbia and hypoxemia.10 In addition, diaphragmatic irritation due to carbon dioxide insufflation will produce shoulder tip pain, necessitating supplementation with sedatives and analgesics. Increased intra-abdominal pressure will also increase the risk of regurgitation and aspiration. Therefore, general anesthesia with endotracheal intubation may be a better choice to provide a secure airway. In addition, general anesthesia also permits controlled ventilation to avoid hypercarbia and hypoxemia and allows the use of muscle relaxants.

53.3.2 What Are Your Concerns in Giving a General Anesthetic to a 17-Week Pregnant Patient?

Cohen-Kerem et al conducted an extensive systematic review (with a patient population of 12,452) to evaluate the effects of non-obstetric surgical procedures (under both regional and general anesthesia) on maternal and fetal outcome.15 The rate of premature labor induced by non-obstetric surgical intervention was 3.5%. Sub-analysis of studies reporting on appendectomy during pregnancy revealed a high rate or premature labor (4.6%). Fetal loss associated with appendectomy was 2.6%, and this rate was quadrupled (10.9%) when peritonitis was present. These findings suggest that acute appendicitis has significantly more adverse effects on the maternal and fetal outcome, particularly if peritonitis develops when compared to other acute surgical conditions during pregnancy.

In other words, apart from the anesthetic care of this patient, special considerations must be given to the well-being and the safety of the fetus. The anesthetic agents and other drugs administered perioperatively may be potentially harmful to the fetus. To address the concern of drugs administered to females during pregnancy, the US Federal Drug Administration (FDA) published the classification of drugs for teratogenic risk in 199416 (see Section 52.3.4). In general, anesthetic drugs and muscle relaxants fall into the category C group, in which risks cannot be ruled out. However, in the clinical doses that are commonly administered, most anesthetic agents, including the volatile agents, nitrous oxide, propofol, thiopental, opioids, benzodiazepines, and muscle relaxants, are not considered teratogenic and are likely to be safe to use.17

53.3.3 Should Fetal Monitoring Be Used during the Procedure for This Patient?

Fetal monitoring practices will vary based on institutional protocols but is usually performed intraoperatively provided it does not interfere with surgical access for the procedure and does not impact the management of the case. This is particularly true in cases where the fetus is considered to be previable. According to the 2009 American Society of Anesthesiologists and the American College of Obstetricians and Gynecologists Joint Statement on Nonobstetric Surgery During Pregnancy, physicians should "obtain obstetric consultation before performing non-obstetric surgery and some invasive procedures (eg, cardiac catheterization, colonoscopy) because obstetricians are uniquely qualified to discuss aspects of maternal physiology and anatomy that may affect intraoperative maternal-fetal well-being" and "if the fetus is considered previable, it is generally sufficient to ascertain the fetal heart rate by Doppler before and after the procedure."18 The definition of fetal viability is problematic. However, the majority of consensus statements on the topic as well as clinical practice consider 24 weeks' gestational age to be the standard limit.19,20 In this case, 17 weeks is considered previable and it would be sufficient to check fetal heart rates before and after the surgical procedure.

53.4.1 How Do You Assess the Airway of This Patient?

Airway evaluation should focus on identifying patient characteristics predictive of difficulty in bag-mask-ventilation, use of extraglottic devices, performance of direct laryngoscopy and endotracheal intubation, and ease of achievement of a surgical airway.

The mnemonic MOANS (see Section 1.6.1) is used to identify predictors of ease of ventilation. This patient has at least two predictors of difficulty in ventilation. She is obese and she has a Mallampati Class IV airway.

Of the four predictors of difficulty in use of an extraglottic device identified by the mnemonic RODS (see Section 1.6.3), this patient has two predictors of difficulties. She has restricted mouth opening and decreased thoracic compliance due to her obesity and the gravid uterus.

The mnemonic LEMON (see Section 1.6.2) is used to identify features which would make direct laryngoscopy and intubation difficult. This patient demonstrates a limited mouth opening and a Mallampati Class IV airway. Restricted mouth opening may also limit the ability to utilize rigid and semirigid fiberoptic devices and video laryngoscopy for tracheal intubation.

The mnemonic SHORT (see Section 1.6.4) describes features that might make a surgical airway a challenge. Apart from obesity, this patient has no other features suggesting difficulty with a surgical airway if needed.

53.4.2 What Preparations Should Be Made Prior to Surgery?

The operating room should be prepared and anesthesia equipment checked. In light of the patient's obesity, limited mouth opening and a Mallampati Class IV airway, a difficult airway situation should be anticipated. Furthermore, the patient is at risk for gastrointestinal stasis, reflux, and aspiration. A difficult airway cart should be brought into the room and appropriately trained assistance should be available.

Prior to proceeding to the operating room, a thorough history and physical examination of the patient must be completed. Specific information regarding previous anesthesia experiences and airway management-related issues should be elicited and previous anesthesia records procured. In this case, the patient has limited mouth opening. The inter-incisor distance should be assessed to determine the potential utility of various devices and techniques available to the anesthesia practitioner.

The patient should be maintained NPO and have intravenous access established. She should receive acid aspiration prophylaxis in the form of metoclopramide 10 mg IV, ranitidine 50 mg IV, and 30 mL of 0.3 N sodium citrate by mouth.

The operating table should be prepared with a ramp to position the patient in anticipation of a difficult airway (see Figure 49-2). In addition, care should be taken to ensure that the patient is positioned appropriately on the operating table with left uterine displacement.

53.4.3 How Should the Airway of This Patient Be Managed?

The specific technique and devices used for airway management under any circumstances should be predicated on the results of the patient's airway assessment and the anesthesia practitioner's skill, proficiency, and confidence with various devices and techniques to secure the airway.

In light of this patient's airway assessment, a rapid-sequence induction followed by direct laryngoscopy would likely be a poor choice. The patient's airway should be secured prior to induction of general anesthesia. The patient should be treated with an antisialogogue in preparation for awake airway management. The patient's airway will need to be anesthetized with topical anesthetics. Specific details regarding the technique of topicalization of the airway may be found in Chapter 3.

While flexible bronchoscopic intubation will be the usual technique of choice for this patient, there are numerous alternative techniques and devices which may be used to secure the airway awake in this patient. The decision will be based on availability of equipment and the inter-incisor distance. For example, the patient can undergo a retrograde intubation with mild sedation. This technique has been used numerous times in patients with very limited mouth opening.14,21 In this patient however, it may be difficult to adequately locate the landmarks for a cricothyroid membrane puncture as a result of her obesity. However, with meticulous technique and adequate experience with the technique, it is possible to secure the airway. This technique has been thoroughly reviewed recently (see Section 11.6).22,23

There are a number of fiberoptic intubating stylets available (see Chapter 10). Shikani performed five awake intubations using the Shikani Optical Scope® during his initial report.24 The Bonfils retromolar fiberscope was used by Corbanese et al25 to successfully carry out awake intubation in 29 or 30 patients with difficult airway. These can be used with either direct laryngoscopy or with a jaw thrust to improve visualization. Most of these devices vary in diameter between 5 mm and 6 mm and can accommodate 5.5 mm ID and larger endotracheal tubes. A number of them have been used successfully to carry out awake intubations in patients with difficult airways or small mouth opening.26-29

Rigid fiberoptic laryngoscopes and video laryngoscopes, such as the Bullard laryngoscope, UpsherScope®, WuScope® and GlideScope®, may be useful in this patient. Cohn30 performed awake intubations using the Bullard laryngoscope in eight patients at risk for neurological injury and requiring awake intubation. However, none of the patients were specifically reported to have limited mouth opening. The Bullard has a spatula-like blade which may be useful in patients with limited mouth opening. Due to its profile, it may be possible to carry out laryngoscopy with an inter-incisor distance of as little as 6 mm. However, it may prove to be difficult to insert or manipulate an endotracheal tube of 6 mm ID or larger size. The WuScope®, due to its design, requires an inter-incisor distance of at least 20 mm to adequately accommodate the scope and endotracheal tube combination.31 The use of the GlideScope® for difficult airway management has increased in recent years. It has been used for awake intubation in patients with a difficult airway,32 and as an adjunct for awake bronchoscopic intubation.33 The GlideScope® provides an improved view of the laryngeal inlet and has been shown to have a high rate of intubation success. The newer model has a 14.5 mm blade flange profile which may be useful in this patient. It must be remembered that all of the optical stylets and video laryngoscopes share the disadvantage of fogging and require some antifogging maneuver prior to their use. In addition, as any blood or secretions in the airway will obscure the view, it is highly recommended that the oropharynx be suctioned prior to the insertion of these devices.

While numerous options to secure the airway of patients with an anticipated difficult laryngoscopic intubation have been discussed, the use of these devices in obstetrical patients is limited. However, it is the author's preference to perform an awake bronchoscopic intubation in this patient. Successful awake intubation will depend upon satisfactory topical anesthesia of pharyngeal and laryngeal structures. Airway edema which accompanies the pregnant state may pose a challenge to topicalization and considerable patience may be required.

Specific details of the techniques of topicalization and bronchoscopic intubation are discussed in Chapters 3 and 9.

53.4.4 What Is the Plan for Extubation of This Patient Following Appendectomy?

No difficult airway management plan is considered complete without a predefined strategy for the safe and successful extubation of the patient following the completion of the procedure. In this case, one must assure that all muscle relaxants have been reversed and the patient is fully awake, following commands, and able to protect her airway prior to extubation. All equipment required for reintubation should be ready and available at the time of extubation. The patient should be extubated in the operating room where access to equipment and medications is assured.

Although the use of general anesthesia in obstetric patients has been declining, it may still be required in specific situations. Patients presenting for non-obstetric surgery may have potential difficult airways. Airway management plans must be designed and formulated based upon a thorough airway examination and familiarity, and skill with various airway devices and techniques. Familiarity with devices and techniques is gained through regular review and practice, and anesthesia practitioners must become facile with a number of options for airway management. Patients with limited mouth opening present numerous challenges and there are various options for securing the airway. The final management plan should depend on the airway evaluation of the patient, the available resources, and the skill set of the anesthesia practitioner.