A 38-year-old woman, gravida 2 para 0, currently at 35 weeks’ gestation, presents for induction of labor due to worsening preeclampsia, marked by persistent headache and worsening laboratory indices of hepatic and renal function.
A review of her medical history reveals that the patient has been living with morbid obesity, essential hypertension, and obstructive sleep apnea. The weight gain has accelerated during pregnancy.
Several years earlier, she underwent diagnostic laparoscopy complicated by deep vein thrombosis. The anesthetic record is not available; however, the patient recalls having a “sore throat” for several days after the procedure.
On admission to labor and delivery, her blood pressure is 156/98, heart rate is regular at 92 beats per minute, and her oxygen saturation is 95% on room air. The airway examination shows a prominent dorsocervical fat pad and large neck. Examination of the airway identifies Mallampati Class IV oropharynx, 3 cm mouth opening, 1 cm thyromental distance, minimal mandibular protrusion, and restricted range of motion in the cervical spine. Her BMI is 50.8 kg·m–2 (133 kg). The current medications are antihypertensives, intravenous magnesium sulfate, and dalteparin, 5000 U every 8 hours (last given 2 hours prior to induction of labor). Her platelet count is 70,000 × 109/L.
The patient makes rapid progress and is offered intravenous patient-controlled analgesia. After 8 hours of labor and 2.5 hours of unsuccessful expulsive efforts, the patient is tired and the fetal heart trace is class 2. As fetal position is not amenable to assisted vaginal delivery, a decision is made to proceed with cesarean section.
What Is the Impact of Anatomic and Physiologic Changes of Pregnancy on Airway Management?
Pregnancy has profound effects on the respiratory, cardiovascular, and gastrointestinal systems.1–3 The incidence of complicated airway instrumentation in pregnancy is around 10 times higher than in the general population.4 A number of physiologic and anatomic changes compound the risks of intubation.
Pregnant patients can exhibit rapid desaturation and decreased apneic oxygenation time upon induction of anesthesia. A recent multicenter cohort study found that up to 20% of parturients who had general anesthesia suffered hypoxemia (10% had severe hypoxemia).5 This is thought to be due to a combination of increased metabolic oxygen requirement, decreased functional residual capacity, and a higher lung closing volume.
During face-mask ventilation (FMV), higher positive pressure may be required to achieve adequate tidal volume. This is due to increased intra-abdominal pressure and decreased chest wall compliance from breast tissue hypertrophy.
Breast enlargement can hinder laryngoscope insertion.
Increased mucosal vascularity and edema can compromise airway patency and increase friability of mucosal surfaces. Snoring and nose bleeds are common in pregnancy as is new or worsening obstructive sleep apnea.
The risk of passive regurgitation of gastric contents during airway management is increased....