Comparison of fentanyl and sufentanil as adjuncts to bupivacaine for labor epidural analgesia

STUDY OBJECTIVE: To compare the clinical efficacy of theoretically equipotent doses of fentanyl and sufentanil, each in combination with bupivacaine, for patient-controlled epidural analgesia (PCEA) for labor. DESIGN: Single-blinded, randomized study. SETTING: University hospital. PATIENTS: 48 ASA physical status I and II term parturients in active labor, with cervical dilatation equal to or less than 5 cm, and requesting epidural analgesia. INTERVENTIONS: Patients received a loading dose of 10 mL of 0.125% bupivacaine with either 30 microg of fentanyl or 5 microg of sufentanil. PCEA was maintained with 0.0625% bupivacaine with either fentanyl two microg/mL or sufentanil 0.35 microg/mL. The PCEA settings were: bolus 5 mL, lockout 10 minutes, infusion 10 mL/hr, and maximum dose 40 mL/hr. Standardized rescue doses of bupivacaine were administered as necessary. MEASUREMENTS: The bupivacaine requirement in mg/hr was calculated from the time of initiation of the epidural until the patient had had 4 to 6 hours of PCEA. The hourly pain score, sensory and motor block, and side effects were documented. Overall patient satisfaction was assessed at the end of the study. MAIN RESULTS: The mean (standard deviation) bupivacaine requirement was 12.4 mg/hr (3.2) and 11.0 mg/hr (2.4) for the fentanyl and sufentanil groups, respectively (P = 0.08). There was evidence of higher maternal satisfaction (P = 0.01), and weak evidence of lower pain scores (P = 0.10) in the sufentanil group. The side effects were similar in both groups. CONCLUSIONS: At the assumed equipotent sufentanil to fentanyl ratio of 6:1, there is some evidence that sufentanil is clinically superior to fentanyl as an adjunct to bupivacaine in labor epidurals, although the advantages are subtle.