Prophylactic intravenous bolus ephedrine for elective Caesarean section under spinal anaesthesia

To evaluate the efficacy and optimal dose of prophylactic intravenous ephedrine for the prevention of maternal hypotension associated with spinal anaesthesia for Caesarean section.

After patients had received an intravenous preload of 0.5 L of lactated Ringer's solution, spinal anaesthesia was administered in the sitting position with hyperbaric bupivacaine 2.5 mL 0.5% combined with 25 microg fentanyl. A total of 68 patients were randomized to receive a simultaneous 2 mL bolus intravenously of either 0.9% saline (Group C, n = 20), ephedrine 6 mg (Group E-6, n = 24), or ephedrine 12 mg (Group E-12, n = 22). Further rescue boluses of ephedrine 6 mg were given if systolic arterial pressure fell to below 90 mmHg, greater than 30% below baseline, or if symptoms suggestive of hypotension were reported.

There was a significantly higher incidence of hypotension in Group C (60% patients) compared to Group E-12 (27%), but not in Group E-6 (50%). The 95% Confidence Interval for the difference in proportions between Groups C and E-12 was 6-60%, P < 0.05. Fewer rescue boluses of ephedrine were required in Group E-12 compared with Group C (1.8 +/- 1.2 vs. 3.3 +/- 2.1, P < 0.05). There were no significant differences in the incidence of maternal nausea or vomiting, or of neonatal acidaemia between groups.

A prophylactic bolus of ephedrine 12 mg intravenously given at the time of intrathecal block, plus rescue boluses, leads to a lower incidence of hypotension following spinal anaesthesia for elective Caesarean section compared to intravenous rescue boluses alone.