Chapter 41: Obstetric Anesthesia

KEY CONCEPTS

• According to the U.S. Centers for Disease Control and Prevention, the leading causes of pregnancy-related death in the United States in 2017 were cardiovascular diseases (14%), infection/sepsis (13%), cardiomyopathy (12%), hemorrhage (11%), embolism (10%), stroke (8%), and hypertensive disorders of pregnancy (7%). Other pregnancy-related deaths were due to amniotic fluid embolism (6%), homicide (3%), unintentional injury (3%), and autoimmune disease (2%). Only 0.4% of maternal deaths were anesthesia related.

• Regardless of the time of last oral intake, all obstetric patients are considered to have a full stomach and be at risk for pulmonary aspiration.

• Nearly all parenteral opioid analgesics and sedatives readily cross the placenta and can affect the fetus. Regional anesthetic techniques are preferred for management of labor pain.

• Using a local anesthetic–opioid mixture for lumbar epidural analgesia during labor significantly reduces drug requirements when compared with using either agent alone.

• Analgesia during labor requires neural blockade at the T10–L1 sensory level in the first stage of labor and at the T10–S4 sensory level in the second stage.

• Continuous lumbar epidural analgesia is the most versatile and most commonly employed technique because it can be used for pain relief for the first stage of labor as well as analgesia/anesthesia for subsequent vaginal delivery or cesarean section.

• Epidural analgesia does not increase the rate of operative delivery and has little if any effect on labor progress when dilute mixtures of a local anesthetic and an opioid are used.

• Unintentional intravascular or intrathecal placement of an epidural needle or catheter is possible even when needle or catheter aspiration does not yield blood or cerebrospinal fluid.

• Hypotension is a common side effect of regional anesthetic techniques and can be treated with intravenous boluses of phenylephrine (40–120 mcg), supplemental oxygen, left uterine displacement, and an intravenous fluid bolus to prevent fetal compromise.

• Techniques using combined spinal–epidural (CSE) analgesia and anesthesia may especially benefit patients with severe pain early in labor and those who receive analgesia/anesthesia immediately prior to delivery.

• Spinal or epidural anesthesia is preferred to general anesthesia for cesarean section because regional anesthesia is associated with less hemodynamic fluctuation, more gradual resolution of analgesia during anesthetic recovery, and lower maternal mortality.

• Continuous epidural anesthesia allows better control over the sensory level than “single-shot” spinal anesthesia. Conversely, spinal anesthesia has a more rapid, predictable onset; may produce a more dense (more complete) block; and lacks the potential for serious systemic drug toxicity because of the smaller dose of local anesthetic employed.

• The risk of systemic local anesthetic toxicity during epidural analgesia and anesthesia is minimized by slowly administering dilute solutions for labor pain and by fractionating the total dose administered for cesarean section into 5-mL increments.

• Maternal hemorrhage is a common cause of maternal morbidity. Causes for antepartum hemorrhage include placenta previa, abruptio placentae, and uterine rupture. Common causes of postpartum hemorrhage include uterine atony, a retained placenta, obstetric lacerations, uterine inversion, and the use of tocolytic agents prior to delivery.

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