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

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.

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.

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.

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).