Determination of the Dose-Response Relationship for Intrathecal Sufentanil in Laboring Patients

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Abstract
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 studies among drugs at equipotent doses cannot be performed. This study was performed to establish the dose-response relationship of intrathecal sufentanil analgesia in labor. Sixty parturients presenting in active labor 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) microg in a blind, randomized fashion. Patient 100-mm visual analog pain scale (VAS) scores, fetal heart rate (FHR), blood pressure, and heart rate were recorded at 0, 1, 5, 10, 15, 20, 25, and 30 min after administration of sufentanil and then again when the patient requested additional analgesia. Absolute VAS < or =25 mm was considered an analgesic success. Percent responders was used to construct a dose-response curve and calculate ED50 and ED95. The ED50 and ED95 for intrathecal sufentanil in laboring parturients were 2.6 (1.8-3.2, 95% confidence interval) and 8.9 (7.5-11.5) microg, respectively. There was a trend toward increasing analgesic duration with increasing sufentanil dose. The maternal side effect profile was not different among groups. FHR did not appreciably change for any group or individual studied. Assisted delivery and cesarean section rates were similar for all groups. Intrathecal sufentanil provides rapid onset of analgesia for labor. The ED50 and ED95 values established in this study should help to provide benchmarks both for the safe clinical use of intrathecal sufentanil for labor and for future comparison studies with other intrathecal analgesic techniques.