Abstract

The authors previously reported that if a loading dose of 50 mg bupivacaine was followed by infusion of 0.0625% bupivacaine (12.5 mg/hr), supplemental doses to achieve satisfactory analgesia for labor and delivery were required in 50% of patients. The current study was done to determine whether increasing the dose from 12.5 to 25 mg/h would eliminate the need for supplemental injections. Twenty-three healthy parturients were randomly assigned to one of two groups—Group I: 0.125% bupivacaine at 20 ml/hr (25 mg/hr); or Group II: 0.25% bupivacaine at 10 ml/hr (25 mg/hr). Taking both groups together, the 50-mg bupivacaine loading dose followed by 25 mg/hr provided adequate analgesia for labor and delivery in 74% of the patients. Two parturients in Group I and three in Group II required supplemental boluses of 4 ml of 0.5% bupivacaine for delivery. Pharmacokinetic data were similar in both groups. Using a dose of 25 mg/hr resulted in 74% of the patients obtaining adequate analgesia for labor and delivery. This improvement over the 50% success rate in the previous study, was achieved without any evidence of toxicity.