In a double blind study we compared the effects of i.m. ketamine with morphine on postoperative analgesia in children undergoing tonsillectomy. Eighty children (aged 6-15 yr) were randomized to receive either i.m. morphine 0.1-0.15 mg kg-1 or ketamine 0.5-0.6 mg kg-1, after induction of a standard general anaesthetic. Pain scores 30 min after extubation were higher (P < 0.05) in the ketamine group, but were similar thereafter to the morphine group. Mean (SD) times to recovery from anaesthesia were 20.1 (SD 6.5) min in the ketamine group compared to 14.2 (5.6) min in the morphine group (P < 0.01). There were no differences in supplemental analgesia requirements, or the incidence of vomiting or dreaming between the groups. We conclude that ketamine 0.5 mg kg-1 i.m. may be an alternative analgesic for children undergoing tonsillectomy.

SummaryThere is little evidence that local anaesthetics produce pre-emptive analgesia and one reason may be the short duration of action of the drugs studied. We examined the pre-emptive analgesic effect of a bupivacaine field block on postoperative pain in 40 patients following herniorrhaphy in a doubleblind, randomised trial. Patients received the block either after induction but before surgery, or after surgery but before the end of anaesthesia. There was no difference in pain scores or analgesic consumption up to 7 days after surgery between the two groups. We have demonstrated that bupivacaine does not appear to provide significant pre-emptive analgesia following a field block for herniorrhaphy. This study does not support the hypothesis that pre-emptive analgesia with local anaesthetic depends upon the duration of action of the drug.

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