Side-effects of postoperative epidural analgesia in children: a randomized study comparing morphine and clonidine

Morphine is widely used in association with local anaesthetics for postoperative epidural analgesia. There are no data on the prolonged use of clonidine for postoperative analgesia in children. The primary outcome of this randomized, double-blind trial was to compare the incidence of side-effects after epidural infusion of clonidine or morphine, in association with ropivacaine in children.

After institutional approval, 26 children, aged 3-12 years, who were scheduled for abdominal surgery, had an epidural catheter placed after induction of general anaesthesia. Patients were then randomized to two different groups. After an initial bolus of 2.5 mg x kg-1 0.25% ropivacaine with either 40 micro g x kg-1 morphine (group M, n = 14) or 1 micro g x kg-1 clonidine (group C, n = 12), an epidural infusion was started at a rate of 0.4 ml x kg-1 x h-1. The patients in the M group received an infusion of 0.08% ropivacaine with 10 micro g.ml-1 morphine, those in the group C an infusion of 0.08% ropivacaine with 0.6 micro g.ml-1 clonidine.

The two groups were similar with respect to age, sex and weight. One patient in the C group was excluded for misplacement of the epidural catheter. The incidence of vomiting and pruritus was significantly higher in the M group compared with the C group (64% and 85% versus 0%, respectively). The incidence of pain was significantly higher in the C group compared with the M group (73% versus 29%) as well as the need for rescue analgesia medications.

Epidural clonidine is followed by a significantly lower incidence of side-effects. However, its analgesic effects, at least at the doses used in this study, are less potent than those of epidural morphine.