Effects of the addition of subarachnoid clonidine to the anesthetic solution of sufentanil and hyperbaric or hypobaric bupivacaine for labor analgesia.

BACKGROUND AND OBJECTIVES

The addition of subarachnoid clonidine (alpha-agonist) prolongs the analgesia produced by the combination of sufentanil and isobaric bupivacaine in combined labor analgesia(1). The objective of this study was to compare the quality of analgesia and the prevalence of side effects after the addition of subarachnoid clonidine to the anesthetic solution in labor analgesia.

METHODS

After approval by the Ethics Commission, 22 pregnant women in labor were randomly assigned to the subarachnoid administration of either 2.5 mg of 0.5% hyperbaric bupivacaine (CLON/HYPER Group; n = 11) or 2.5 mg of 0.5% isobaric bupivacaine (CLON/ISO Group; n = 11) associated with 2.5 microg of sufentanil and 30 microg of clonidine. Pain, evaluated by the Visual Analogue Scale, heart rate, and mean arterial pressure were assessed every 5 minutes during the first 15 minutes, and then every 15 minutes afterwards until delivery. The prevalence of side effects (nausea, vomiting, pruritus, and sedation) was evaluated. The study was terminated whenever the patient needed supplemental epidural analgesia (pain > 3) or upon delivery of the fetus. The Student t test, Chi-square test, Fisher exact test, and two-way ANOVA for repeated measurements were used in the statistical analysis and a p < 0.05 was considered significant.

RESULTS

Anthropometric data, duration of analgesia (70.9 +/- 32.9 vs. 85.4 +/- 39.5), heart rate, and the incidence of pruritus, sedation, nausea, and vomiting were similar in both groups. Mean arterial pressure was significantly lower in the CLON/ISO Group than in the CLON/HYPER Group at 15, 30, and 45 minutes (p < 0.05).

CONCLUSIONS

Under the conditions of the present study, the association of a small dose of clonidine (30 microg) with sufentanil caused a higher incidence of hypotension when the isobaric solution of the local anesthetic was used. For all other side effects, both hyperbaric and isobaric solutions showed similar behavior.