Different preloading protocols with constant ephedrine infusion in the prevention of hypotension for elective cesarean section under spinal anesthesia

Ninety ASA I or II parturients were randomly allocated to three groups: group 10RL, 15RL and 20RL to receive 10, 15 and 20 mL/kg of Ringer's lactate (RL) respectively within 15 minutes (min) before the spinal block. Spinal anesthesia was performed with hyperbaric bupivacaine 12 mg, morphine 100 microg and fentanyl 10 microg. The operating table was tilted to the left and an IV infusion of ephedrine of 3 mg/min was immediately started and continued until umbilical cord clamping in all groups. Hypotension was defined as a drop in mean arterial pressure (MAP) of more than 20% from baseline : this was treated with 10 mg ephedrine IV. The incidence of hypotension was 60%, 36.7% and 13.4% in group 10RL, 15RL and 20RL, respectively (p<0.05). Additional ephedrine dose was the lowest in group 20RL compared to the other groups (p<0.05). The total amount of ephedrine was 49.9 +/- 13.5, 46.4 +/- 13.4 and 38.4 +/- 8.5 mg in group 10RL, 15RL and 20RL, respectively (p <0.05). The incidence of nausea and vomiting in group 20RL was significantly less than in group 10RL (p = 0.02). It was concluded that preloading with 20 mL/kg of RL prior to spinal anesthesia followed by constant ephedrine infusion 3 mg/min after spinal block reduced the incidence of hypotension and of nausea and vomiting and decreased the total amount of ephedrine.