Intrathecal sufentanil for labor analgesia: do sensory changes predict better analgesia and greater hypotension?

Abstract

Sensory changes and hypotension occur after intrathecal sufentanil (ITS) is given during labor. The goal of this study was to determine whether sensory changes are predictive of hemodynamic changes or duration of pain relief. We also examined whether sensory and hemodynamic changes relate to the concentration of ITS administered. Forty-five ASA physical status I and II women in active labor were randomly assigned to receive 10 micrograms ITS diluted in either 1, 2, or 3 mL of normal saline (15 in each group). An observer blinded to treatment recorded verbal pain scores, blood pressure, and sensory changes to light touch, pinprick, and cold at frequent intervals. Excellent analgesia was obtained in 42 of 45 patients. There were no differences among the groups with respect to the number of patients with sensory changes, the duration of analgesia or sensory changes, the quality of analgesia, or the severity of hypotension. The groups were therefore combined for further analyses. Among this combined group, the duration of analgesia was 99 +/- 7 min (mean +/- SE). Cold, pinprick, and light touch sensation were decreased in 66%, 50%, and 33% of patients, respectively. Motor block was absent in all patients. The duration and quality of analgesia were similar in subjects with and without sensory changes. Systolic blood pressure decreased 23 +/- 2 mm Hg (P < 0.05) during the first 30 min after ITS, and six patients were given ephedrine. The magnitude of blood pressure change was not affected by the diluent volume or the presence of sensory changes. Because sensory changes were not predictive of the duration or quality of analgesia or the degree of hemodynamic change, we conclude that analgesia with ITS is predominantly mediated via spinal cord opioid receptors rather than by a local anesthetic-type conduction blockade.