A 20-year-old female, G1P0 at 17 weeks’ gestation, presents to the emergency department (ED) complaining of right sided abdominal pain. The pain began 10 hours ago accompanied by nausea and two episodes of vomiting. The patient is afebrile and has a blood pressure of 130/72 mm Hg. Her 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. After ultrasonography by an obstetrician, the cause of pain is felt not to be related to pregnancy. The general surgery service is consulted, and it is their opinion that the patient has appendicitis and will require a laparoscopic appendectomy.

The parturient has had an unremarkable pregnancy thus far and has no medical comorbidities or allergies. She is a nonsmoker and does not consume alcohol. She takes prenatal vitamins, but no prescription medications. She has had no prior anesthetics and has no family history of anesthesia-related problems. Physical examination of her heart and lungs is unremarkable. There are no physical abnormalities of her spine. Her airway examination reveals a Mallampati Class IV airway with limited mouth opening. She has a normal range of motion of her cervical spine, full dentition, and minimal mandibular protrusion. The thyromental distance is 5 cm and the hyomental distance is 3 cm.

What Is the Incidence of Appendicitis in Pregnancy?

Appendicitis has an incidence of approximately 1 in 500 to 1 in 635 pregnancies per year, with appendectomy being the most common non-obstetric surgical procedure during pregnancy.¹ The relative incidence is estimated to be 30% in the first trimester, 45% in the second trimester, and 25% in the third trimester.² Fetal loss in the first trimester usually occurs in 3% to 15% of women with complicated appendectomy during the first trimester.¹ The risk of premature delivery occurs at a rate of 15% to 45%, and parturients are at increased risk of spontaneous abortion, premature labor, and perinatal morbidity and mortality.¹ The risk of perforation increases with advanced gestation and delay in diagnosis.^3,4 The estimated risk of fetal loss with appendiceal perforation is 36%.⁵ The risk of maternal mortality is minimal, which can be attributed to the use of advanced antibiotics, close perioperative monitoring, multidisciplinary case involvement, and improved perioperative management.¹

How Is Appendicitis Diagnosed During Pregnancy?

Anatomic and physiologic changes accompanying pregnancy make the 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. It typically relocates from McBurney’s point upward from the iliac crest to near the gallbladder.¹ However, according to studies, 84% of pregnant patients present with right lower quadrant pain.^2,4 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.³ Diagnostic imaging using helical CT scanning has been reported to have a sensitivity and specificity of 92% to 98% and 99% to 100% respectively.^6,7 Fetal radiation exposure with the helical CT scan approximates 0.3 rad which is well below the five rad considered the maximal safe level of fetal exposure.⁸

What Are the Surgical Options for Appendectomy in Pregnancy?

There are two surgical options for removing the appendix. Appendectomy can be performed via an exploratory laparotomy (open technique) or laparoscopic technique. The cited advantages of the open technique include better direct visualization, decreased operating room costs, and reduced fetal exposure to carbon dioxide. In addition, an open appendectomy is an established and safe operation, with acceptable morbidity and low mortality rates.¹ The advantages of the laparoscopic technique include fewer wound infections, reduced postoperative pain and opioid use, reduced uterine handling, early return of gastrointestinal 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.^8–10 In addition, there are reports of an increased risk of intra-abdominal abscess, particularly in perforated appendicitis, with the laparoscopic technique.¹ Laparoscopic appendectomy is considered to be safe during any trimester, however pregnant patients should receive venous thromboembolism prophylaxis due to a risk of venous stasis secondary to carbon dioxide pneumoperitoneum.⁸ A systematic review by Walsh et al.¹¹ that included 28 observational studies, suggested that the laparoscopic procedure was associated with a higher rate of fetal loss, but a similar or lower rate of preterm delivery, compared with open appendectomy. Similarly, a recent systematic review and meta-analysis of the safety of laparoscopic versus open appendectomy for suspected appendicitis in pregnancy suggests that the laparoscopic technique results in an almost twofold significantly higher risk of fetal loss, compared with open appendectomy.¹ However, there were no differences observed between groups regarding preterm delivery, birth weight, Apgar score, wound infection after surgery, or duration of operation.³ Similarly, a retrospective cohort study of all women undergoing appendectomy during pregnancy in a tertiary referral medical center from 2000 to 2009 was completed by Peled et al.¹² A laparoscopic appendectomy was completed in 31% of patients while 69% had an open appendectomy. No significant difference was found in the general, obstetrical, and neonatal outcome characteristics, however, postoperative complications such as fever and uterine contractions were higher in the open appendectomy group.¹² The authors concluded that laparoscopic appendectomy appears to be a safe procedure for presumed acute appendicitis during pregnancy, with less postoperative complications.¹²

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.¹³ Under normal circumstances, the creation of the pneumoperitoneum will impact cardiovascular and respiratory physiology. Carbon dioxide insufflation of the peritoneal cavity will initially increase venous return as intravascular blood volume is augmented by compression of the splanchnic vasculature. The result is an increase in cardiac output and arterial blood pressure. Sympathetic nervous system activation due to carbon dioxide absorption causes an increase in systemic vascular resistance.¹⁴ As intra-abdominal pressure increases beyond 15 mm Hg, venous return will then 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.⁸ Insufflation may also result in bradyarrythmias 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. The pneumoperitoneum decreases pulmonary and thoracic compliance and increases peak inspiratory pressures. Elevation of the diaphragm further reduces 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.¹⁵

What Are the Anesthetic Options for Laparoscopic Appendectomy?

Traditionally, acute appendicitis has been treated with surgical appendectomy combined with intravenous antibiotics.¹⁶ Recently, a role for conservative management with antibiotics was suggested in nonpregnant patients.^17,18 A meta-analysis suggested that antibiotics are both effective and safe as primary treatment for patients with uncomplicated acute appendicitis.¹⁸ While this noninterventional option has not been fully addressed in the pregnant patient, there is at least one case report describing a successful outcome of acute uncomplicated appendicitis in pregnancy managed successfully with conservative antibiotic treatment.¹⁶ In select cases, such as contraindications or patient refusal of surgery, conservative treatment may be the best anesthetic management.

The majority of parturients will continue to be managed with a surgical approach. General and regional anesthesia are both anesthetic options for laparoscopic procedures in the non-parturient patient.¹⁴ Regional anesthesia, such as epidural or spinal techniques however, are not recommended in pregnancy. The pneumoperitoneum may increase intra-abdominal pressures causing the gravid uterus to compromise spontaneous ventilation leading to hypercarbia and hypoxemia, and increase the risk of regurgitation and aspiration.⁹ In addition, diaphragmatic irritation due to carbon dioxide insufflation can produce shoulder tip pain, necessitating supplementation with sedatives and analgesics. Therefore, general anesthesia with endotracheal intubation may be a better choice to provide a secure airway. In addition, general anesthesia permits controlled ventilation to avoid hypercarbia and hypoxemia, and allows the use of muscle relaxants to facilitate surgery.

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

Cohen-Kerem et al.¹⁹ conducted an extensive systematic review (n =12,452) to evaluate the effects of non-obstetric surgical procedures (under both regional and general anesthesia) on maternal and fetal outcome. 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.

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) has published the classification of drugs for teratogenic risk in 1994.²⁰ 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, opioids, benzodiazepines, and muscle relaxants are likely to be safe to use.²¹

Should Fetal Monitoring be Used During the Procedure for This Patient?

Fetal monitoring practices will vary based on institutional protocols, but are usually performed intraoperatively, provided that it does not interfere with surgical access or impact case management. This is particularly true in cases where the fetus is considered to be viable. According to the 2009 American Society of Anesthesiologists and American College of Obstetricians and Gynecologists joint statement on non-obstetric surgery during pregnancy, physicians should “obtain obstetric consultation before performing non-obstetric surgery and some invasive procedures (e.g., cardiac catheterization, colonoscopy), because obstetricians are uniquely qualified to discuss aspects of maternal physiology and anatomy that may affect intraoperative maternal-fetal well-being.” Moreover, “if the fetus is considered previable, it is generally sufficient to ascertain the fetal heart rate by Doppler before and after the procedure.”²²

The definition of fetal viability is problematic. However, the majority of consensus statements, as well as clinical practice, consider 24 weeks gestational age to be the standard limit.^23,24 In this case, 17 weeks is considered previable and it would be sufficient to check fetal heart rates before and after the surgical procedure.

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 (EGDs), performance of direct laryngoscopy and endotracheal intubation, and ease of achievement of a surgical airway.

The mnemonic MOANS (see section “Difficult BMV: MOANS” in Chapter 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 EGD identified by the mnemonic RODS (see section “Difficult Use of an EGD: RODS” in Chapter 1), this patient has two predictors of difficulty. She has restricted mouth opening and decreased thoracic compliance due to her obesity and the gravid uterus.

The mnemonics LEMON and CRANE (see sections “Difficult DL Intubation: LEMON” and “Difficult VL Intubation: CRANE” in Chapter 1) are used to identify features which would make direct and indirect 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.