INTRATHECAL SUFENTANIL DOSE-RESPONSE IN NULLIPAROUS PATIENTS

Background: Intrathecal sufentanil provides effective analgesia during the first stage of labor. A range of doses has been reported to provi de adequate pain relief. This study determined the dose of intrathecal sufentanil that produced acceptable pain relief in 50% of nulliparous patients (ED50) who requested labor analgesia. Methods: With institut ional review board approval, 50 nulliparous patients requesting spinal opioid labor analgesia were enrolled into this prospective, randomize d, double-blinded study. Each patient was in spontaneous labor at <5 c m cervical dilation. Patients received one of the following doses of i ntrathecal sufentanil: 1, 2, 3, 5, or 10 mu g in 3 ml preservative-fre e saline (n = 10 for each dose). Pain, pain relief hemodynamic, respir atory, and side effect data were collected at times 0, 2, 5, 10, 15, 2 0, 25, and 30 min. Probit analysis of the number of patients in each g roup who requested additional pain medicine at 30 min n;as used to det ermine the ED50. Results: The groups were demographically similar. The ED50 of intrathecal sufentanil was 1.8 mu g (SE, 0.6 mu g; 95% CI, 2. 96 to 0.54 mu g). The incidence of side effects tvas similar among the groups. Conclusions This is the first study to determine the ED50 of intrathecal sufentanil in spontaneously laboring nulliparous patients. As dose-response curves are determined for other labor analgesics, fu ture studies can compare equianalgesic doses or dose combinations.