Addition of epinephrine to epidural ropivacaine during labour--effects on onset and duration of action, efficacy, and systemic absorption of ropivacaine.

Abstract

Addition of epinephrine to epidural anaesthetic solutions may enhance efficacy and duration of analgesia. We postulated that addition of epinephrine 5 microg.mL(-1) to epidural ropivacaine would improve efficacy, decrease systemic absorption and reduce neonatal effects. Twenty-one multiparous women were studied. An initial dose of ropivacaine 30 mg followed by an infusion of ropivacaine 10 mg.h(-1) was given via a lumbar epidural catheter. According to random allocation, epinephrine 5 microg.mL(-1) was added to ropivacaine. Ropivacaine concentrations were measured in maternal venous plasma after one hour of infusion and in both umbilical venous and maternal plasma at delivery. Neonatal neurologic and adaptive capacity score (NACS) tests were performed at 2 and 24 h postpartum. All women delivered vaginally. The groups had similar ropivacaine dose requirements, epidural-delivery intervals and satisfaction scores. Bromage scores for motor block were greater in the epinephrine group (2; range: 1-3) than controls (1; range: 0-2). Mean plasma ropivacaine concentrations (+/-SD) were less in the epinephrine group (0.17 +/- 0.05 mg.L(-1), n = 10) than controls (0.31 +/- 0.14 mg.L(-1), n = 11; P < 0.05) after one h of infusion but not at delivery. UV ropivacaine concentrations and NACS scores were similar in the two groups. The addition of epinephrine to ropivacaine decreases maternal plasma concentrations after one h of epidural infusion but also increases motor block.