Chapter 41. Obstetric Anesthesia

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  The most common morbidities encountered in obstetrics are severe hemorrhage and severe preeclampsia.
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  Regardless of the time of last oral intake, all obstetric patients are considered to have a full stomach and to be at risk for pulmonary aspiration.
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  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.
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  Using a local anesthetic-opioid mixture for lumbar epidural analgesia during labor significantly reduces drug requirements, compared with using either agent alone.
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  Pain relief during labor requires neural blockade at the T10-L1 sensory level in the first stage of labor and at T10-S4 in the second stage.
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  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, if necessary.
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  When dilute mixtures of a local anesthetic and an opioid are used, epidural analgesia has little if any effect on the progress of labor.
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  Even when aspiration does not yield blood or cerebrospinal fluid, unintentional intravascular or intrathecal placement of an epidural needle or catheter is possible.
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  Hypotension is a common side effect of regional anesthetic techniques and must be treated aggressively with phenylephrine or ephedrine, supplemental oxygen, left uterine displacement, and intravenous fluid boluses to prevent fetal compromise.
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  Techniques using combined spinal-epidural analgesia and anesthesia may particularly benefit patients with severe pain early in labor and those who receive analgesia/anesthesia just prior to delivery.
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  Spinal or epidural anesthesia is preferred to general anesthesia for cesarean section because regional anesthesia is associated with lower maternal mortality.
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  Continuous epidural anesthesia allows better control over the sensory level than “single-shot” techniques. Conversely, spinal anesthesia has a more rapid, predictable onset; may produce a more dense (complete) block; and lacks the potential for serious systemic drug toxicity because of the smaller dose of local anesthetic employed.
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  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.
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  Maternal hemorrhage is one of the most common severe morbidities complicating obstetric anesthesia. Causes include placenta previa, abruptio placentae, and uterine rupture.
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  Common causes of postpartum hemorrhage include uterine atony, a retained placenta, obstetric lacerations, uterine inversion, and use of tocolytic agents prior to delivery.
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  Intrauterine asphyxia during labor is the most common cause of neonatal depression. Fetal monitoring throughout labor is helpful in identifying which babies may be at risk, detecting fetal distress, and evaluating the effect of acute interventions.

This chapter focuses on the practice of obstetric anesthesia. Techniques for analgesia and anesthesia during labor, vaginal delivery, and cesarean section are presented. The chapter ends with a review of neonatal resuscitation.

Anesthetic Risk in Obstetric Patients

Although the majority of women of childbearing age are healthy ...