KEY POINTS

1. Functional residual capacity (FRC) begins to decrease in the second trimester of pregnancy and is decreased to 80% of the nonpregnant value at full term. This decrease in FRC causes maternal hypoxemia to develop very quickly after apnea associated with the induction of general anesthesia. Although general anesthesia is no longer routinely used for elective cesarean deliveries, it continues to have a place in current practice.
2. The presence of fetal heart rate (FHR) variability is predictive of fetal well-being and early neonatal health. FHR accelerations signal fetal well-being, whereas late decelerations are suggestive of fetal hypoxia.
3. Animal studies have suggested that vasopressors with predominantly α-adrenergic activity cause a reduction in uterine blood flow that can adversely affect the fetus. Studies in humans undergoing elective cesarean section have not confirmed these animal data and have suggested that small doses of phenylephrine may improve the mother's hemodynamics without adversely affecting the fetus.
4. No epidural test dose will exclude all instances of intravenous or intrathecal placement of catheters; however, aspiration of a multiorificed catheter will detect many of them. The combination of aspiration, test dose, and fractionation of doses increases the safety of epidural anesthesia.
5. If an accidental dural puncture occurs during placement of an epidural, threading the epidural catheter into the spinal space to provide continuous spinal anesthesia offers many advantages. If the

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   epidural is relocated to another interspace, however, the loss of resistance to air technique should not be used because of the risk of pneumocephalus and severe headache.
6. Many cases of failed intubation occur when a "difficult airway" is not recognized before induction of general anesthesia. Airways change during pregnancy and may worsen during labor, especially in a preeclamptic patient. Careful airway evaluation, though imperfect, must be performed before initiation of general anesthesia.
7. Uterine rupture is a rare, but potentially catastrophic event that can cause maternal and fetal mortality. Its incidence during vaginal birth after cesarean section is greater than previously thought. A sudden increase in baseline uterine tone or the sudden absence of uterine pressure coupled with evidence of acute fetal bradycardia may indicate uterine rupture.
8. Magnesium sulfate is the agent of choice for seizure control in preeclamptic patients and is a first-line tocolytic therapy for preterm labor. Treatment with magnesium can produce hypotension and may later potentiate the maternal hemodynamic response to pressors. Magnesium also potentiates the action of both depolarizing and non-depolarizing muscle relaxants.