Caesarean section in isobaric spinal anesthesia with and without direct preoperative hydration with crystalloids.

BACKGROUND: Because the direct preoperative hydration with crystalloids (20 ml/kg) does not adequately prevent spinal hypotension during cesarean section, the authors investigated whether a continuous intravenous infusion of ephedrine (50 mg/500 ml of Ringer solution) without preoperative hydration would prevent the spinal hypotension more effectively. METHODS: Forty parturients with ASA status I were randomized either to receive a preoperative hydration with 20 ml/kg of Ringer solution, or to receive continuous ephedrine infusion, simultaneously with spinal anesthesia. The infusion rate was adjusted according to systolic blood pressure. Significant hypotension was defined as a systolic blood pressure below 100 mmHg. Rescue boluses consisted of ephedrine 10 mg in parturients with prehydration and ephedrine 5 mg in parturients with ephedrine infusion. RESULTS: Significant hypotension occurred less frequently in the ephedrine group than in the volume group: 40% versus 60% (p < 0.05). Nausea and vomiting occurred less frequently in the ephedrine group than in the volume group: 40% and 30% versus 60% and 50%, respectively (p < 0.05). The mean quantity of infused Ringer solution was 370 ml +/- 31 in the ephedrine group, i.e. significantly lower than 1,640 ml +/- 192 in the volume group (p < 0.05). The mean quantity of ephedrine given in the ephedrine group was 30 mg +/- 4.1. The mean quantity of ephedrine given in the volume group was 25 mg +/- 2. The difference was not significant. Apgar scores were similarly good in both groups. CONCLUSION: The continuous infusion of ephedrine simultaneously with spinal anesthesia is superior to direct preoperative hydration with crystalloids in preventing the spinal hypotension and its clinical manifestations in parturients delivered with C-section (Tab. 3, Ref. 20).