DETERMINATION OF THE DOSE-RESPONSE RELATIONSHIP FOR INTRATHECAL SUFENTANIL IN LABORING PATIENTS

Multiple studies have investigated the efficacy of intrathecal opioids , particularly sufentanil, in laboring parturients. However, until the important pharmacological indices of the 50% and 95% effective doses (ED50 and ED95, respectively) are defined, reliable comparative studie s among drugs at equipotent doses cannot be performed. This study was performed to establish the dose-response relationship of intrathecal s ufentanil analgesia in labor. Sixty parturients presenting in active l abor received intrathecal sufentanil 2.5 (n = 10), 5.0 (n = 10), 7.5 ( n = 10), 10.0 (n = 10), 12.5 (n = 10), or 15.0 (n = 10) mu g in a blin d, randomized fashion. Patient 100-mm visual analog pain scale (VAS) s cores, fetal heart rate (FHR), blood pressure, and heart rate were rec orded at 0, 1, 5, 10, 15, 20, 25, and 30 min after administration of s ufentanil and then again when the patient requested additional analges ia. Absolute VAS less than or equal to 25 mm was considered an analges ic success. Percent responders was used to construct a dose-response c urve and calculate ED50 and ED95. The ED50 and ED95 for intrathecal su fentanil in laboring parturients were 2.6 (1.8-3.2, 95% confidence int erval) and 8.9 (7.5-11.5) mu g, respectively. There was a trend toward increasing analgesic duration with increasing sufentanil dose. The ma ternal side effect profile was not different among groups. FHR did not appreciably change for any group or individual studied. Assisted deli very and cesarean section rates were similar for all groups. Intrathec al sufentanil provides rapid onset of analgesia for labor. The ED50 an d ED95 values established in this study should help to provide benchma rks both for the safe clinical use of intrathecal sufentanil for labor and for future comparison studies with other intrathecal analgesic te chniques.