Intrathecal epinephrine in combined spinal-epidural analgesia for labor: dose-response relationship for epinephrine added to a local anesthetic-opioid combination

Background: The purpose was to investigate the dose-response relationship for intrathecally administered epinephrine added to a local anesthetic-opioid combination in combined spinal-epidural analgesia for labor, in order to evaluate analgesia and side-effects. Patients and methods: The subjects were 100 consecutive ASA I or II parturients at > 37weeks' gestation, who received combined spinal-epidural analgesia during labor. Each woman was randomly assigned to one of five groups that received 2-mL volumes of different spinal solutions. The control group received an intrathecal injection of bupivacaine 2.5 mg and fentanyl 25 mu g only. The others received epinephrine 12.5, 25, 50 or 100 mu g added to this intrathecal regimen. Maternal arterial pressure, heart rate and pain scores were recorded before and 5, 10, 15 and 30 min after intrathecal injection. Level of sensory blockade, motor blockade score, duration of intrathecal analgesia, side effects, fetal heart rate, and 1- and 5-min Apgar scores were also assessed. Results: Compared to the control group, all four epinephrine groups had significantly longer duration of intrathecal analgesia, but the durations were similar. The frequencies of side effects were similar in all five groups. Conclusion: The results suggest that adding epinephrine to a combination of standard intrathecal doses of bupivacaine and fentanyl in combined spinal-epidural analgesia for labor significantly prolongs spinal analgesia. Of the four epinephrine doses tested, the lowest one (12.5 mu g) was optimal for this clinical setting