Regional anesthesia

Regional anesthesia is the method of choice for Cesarean deliveries for the following reasons:

(1) lower maternal mortality as compared to general anesthesia (Hawkins et al., 1997);

(2) better hemodynamic control;

(3) blunting of neuroendocrine stress response (Ramanathan et al., 1991);

(4) mother is awake and is able to interact with her infant; and

(5) prevention of transient neonatal depression associated with general anesthesia.

Epidural anesthesia is the regional anesthesia technique most commonly used for preeclamptic patients. Hodgkinson et al. (1980) studied systemic and pulmonary artery pressures in severely pre-eclamptic patients undergoing Cesarean section. These investigators demonstrated a stable hemodynamic status with epidural anesthesia versus marked exacerbations in MAP and PCWP during induction, intubation and extubation with general anesthesia (Hodgkinson et al., 1980).

The use of spinal anesthesia in patients with severe pre-eclampsia undergoing Cesarean section is controversial. In severely pre-eclamptic patients with decreased intravascular volume, some anesthesiologists argue that spinal anesthesia should be avoided because of the risk of severe hypotension following the sudden onset of sympathetic blockade. Recent evidence indicates that spinal anesthesia can be used in severely pre-eclamptic patients undergoing Cesarean section without any adverse maternal or fetal sequelae (Hood and Curry, 1999) and that the hemody-namic effects of spinal and epidural anesthesia are similar (Karinen et al., 1996; Wallace et al., 1995). A recent cohort prospective study compared the incidence and severity of spinal-associated hypotension in severely pre-eclamptic patients versus healthy normal parturients undergoing Cesarean section. This study demonstrated a lower incidence of hypotension, as defined by a 30% decrease in MAP in patients with severe pre-eclampsia undergoing Cesarean section under spinal anesthesia than in the healthy normal patients (Figure 30.7) (Aya et al., 2003).

The use of the combined-spinal technique may also be considered in severe pre-eclampsia. Recent evidence indicates that hyperbaric bupivacaine in doses as low as 7.5 mg with 20 mg fentanyl provides adequate anesthesia for Cesarean section. Further, the presence of the epidural

Figure 30.7 Changes in mean blood pressure (BP) after spinal anesthesia in pre-eclamptic and healthy parturients. The top panel shows raw data, whereas percentage changes are shown in the bottom panel. "Time point from which mean BP decreased significantly compared with the corresponding baseline value (P<0.05). In both groups, mean BP decreased significantly from 8min of the spinal injection until the end of the study period. (From Aya et al., 2003, with permission.)

Figure 30.7 Changes in mean blood pressure (BP) after spinal anesthesia in pre-eclamptic and healthy parturients. The top panel shows raw data, whereas percentage changes are shown in the bottom panel. "Time point from which mean BP decreased significantly compared with the corresponding baseline value (P<0.05). In both groups, mean BP decreased significantly from 8min of the spinal injection until the end of the study period. (From Aya et al., 2003, with permission.)

catheter provides the flexibility to extend the level and duration of the block (Ramanathan et al., 2001).

Ideally, in pre-eclamptic patients undergoing urgent Cesarean section, a functioning epidural block should already be in place. The pre-existing block can be augmented with either 3% 2-chloroprocaine or pH-adjusted 2% lidocaine to rapidly provide surgical anesthesia. The fetal heart rate should be monitored in the operating room up until immediately prior to the preparation and initiation of surgery.

Published studies of spinal anesthesia in pre-eclamptics have largely excluded women with non-reassuring FHR (Wallace et al., 1995). Until large randomized trials can determine the safety of spinal anesthesia in severely pre-eclamptic patients undergoing urgent Cesarean section for non-reassuring FHR, the use of a pre-established epidural block will continue to remain the preferred technique.

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