Analgesic and hemodynamic effects of intrathecal clonidine as the sole analgesic agent during first stage of labor: a dose-response study.

BACKGROUND: Intrathecal clonidine produces dose-dependent postoperative analgesia and enhances labor analgesia from intrathecal sufentanil. The authors evaluated the dose-response potency of intrathecally administered clonidine by itself during first stage of labor with respect to analgesia and maternal and fetal side effects.

METHODS: Thirty-six parturients requesting labor analgesia were included in this prospective, randomized, double-blind study. Parturients with < 6 cm cervical dilatation received either 50, 100, or 200 microg intrathecal clonidine. The authors recorded visual analog pain score (VAPS), maternal blood pressure and heart rate, ephedrine requirements, and sedation at regular intervals and fetal heart rate tracings continuously. Duration of analgesia was defined as time from intrathecal clonidine administration until request for additional analgesia.

RESULTS: Clonidine produced a reduction in VAPS with all three doses. The duration of analgesia was significantly longer in patients receiving 200 microg (median, 143; range, 75-210 min) and 100 microg (median, 118; range, 60-180 min) than 50 microg (median, 45; range, 25-150 min), and VAPS was lower in the 200-microg than in the 50-microg group. In the 200-microg group, hypotension required significantly more often treatment with ephedrine than in the other groups. No adverse events or fetal heart rate abnormalities occurred.

CONCLUSIONS: Fifty to 200 microg intrathecal clonidine produces dose-dependent analgesia during first stage of labor. Although duration and quality of analgesia were more pronounced with 100 and 200 microg than with 50 microg, the high incidence of hypotension requires caution with the use of 200 microg for labor analgesia.