Evaluation of 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

ABSTRACT

Intrathecal clonidine produces dose-dependent postoperative analgesia and enhances labor analgesia from intrathecal sufentanil. We 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. Forty-five parturients requesting labor analgesia were studied. In a combined spinal-epidural technique, patients with <5 cm cervical dilatation were assigned to receive one of the following intrathecal solutions either 75 micro g clonidine [n = 15]; 150 micro g clonidine [n = 15]; and 250 micro g clonidine [n = 15]. Visual analog scores for pain, blood pressure, heart rate, ephedrine requirements, sensory levels, incidence of nausea, pruritus and sedation, fetal heart rate tracings continuously, and maternal and cord blood concentrations of clonidine were recorded. Duration of analgesia was defined as time from intrathecal clonidine administration until request for additional analgesia. We found that clonidine produced a reduction in VAPS with all three doses. The duration of analgesia was significantly longer in patients receiving 250 micro g [median, 150; range, 85-220 min] and 150 micro g [median, 120; range; 65-190 min] than 75 micro g [median 50; range, 30 - 160 min], and VAPS was lower in the 250 micro g than in the 75 micro g group. As regards the sensory levels, no patient in any group had sensory changes above T[3]. In the 250 micro g group, hypotension required significantly more often treatment with ephedrine than in the other groups. Also, bradycardia and sedation were more in 250 micro g group than the other two groups. No adverse events or fetal heart rate abnormalities occurred. Clonidine levels were undetectable in maternal and cord serums. In conclusion, the current study showed that 75 micro g to 250 micro g intrathecal clonidine produces dose-dependent analgesia during first stage of labor. Although duration and quality of analgesia were more pronounced with 150 and 250 micro g than with 75 micro g, the high incidence of hypotension, bradycardia and sedation requires caution with the use of 250 micro g for labor analgesia