Premedication with low dose oral clonidine does not enhance postoperative analgesia of intrathecal morphine.

Abstract

A number of studies have demonstrated that perioperative intravenous, intrathecal, and epidural clonidine enhance postoperative analgesia. The results of previous studies on the usefulness of oral clonidine on enhancing postoperative analgesia have been mixed. The effect of a single preoperative dose of oral clonidine on postoperative analgesia was assessed in this study. Forty-three male patients undergoing radical prostectomy were randomized to receive either 3 microg x kg(-1) clonidine or placebo po 90 min prior to surgery. All patients received isobaric 15 mg bupivacaine and intrathecal 5 microg x kg morphine, followed by a standardized general anesthetic, consisting of thiopental, sufentanil, rocuronium, isoflurane, oxygen and air. Postoperatively, PCA morphine use and visual analogue pain scores were recorded for the first 48 hr. The incidence and severity of side effects such as sedation, nausea, and pruritus were assessed, as well as patient satisfaction. Usage of PCA morphine was compared. There was no difference in total morphine requirements between the placebo and oral clonidine groups, nor in six hourly morphine usage (P = 0.96). Second, there was no difference in visual analogue pain scores, or the incidence of side effects. Patient satisfaction was high in both groups and again, no differences between groups was noted. Oral clonidine 3 microg x kg(-1) as a premedication does not prolong the effect of intrathecal morphine: there was no difference in PCA morphine requirements (P = 0.96). Clonidine did not effect the incidence or severity of nausea or pruritus.