R.J. MARCUS, B.A. VICTORIA, S.C. RUSHMAN AND J.P. THOMPSON
University Department of Anaesthesia and Pain Management, Leicester Royal Infirmary, Leicester, United Kingdom
Br. J. Anaesth., 84: 739–742, 2000
Studies comparing ketamine and placebo showed better pain relief with the drug than with placebo, but no studies have yet compared ketamine with other analgesics in children. This double-blind, randomized study compared the effects of ketamine and morphine on postoperative pain after tonsillectomy in 80 children, aged 6 to 15 yr.
Children received either IM morphine, 0.1 to 0.15 mg/kg, or ketamine 0.5 to 0.6 mg/kg after anesthesia induction using a standard technique. Tonsillectomy was performed by dissection and diathermy. Pain was assessed using both a 5-point “faces” scale and the Children’s Hospital Eastern Ontario Pain Scale (CHEOPS) at 30, 60, 120, and 240 min after tracheal extubation. Respiratory rates and incidence of nausea and vomiting were also recorded at these times. The occurrence of any dreams or hallucinations was determined after 4 hr. The morning after the surgery parents completed a questionnaire.
The two groups (n = 40 each) were similar with respect to age, weight, and duration of surgery. Mean time to awaken was significantly longer in the ketamine group (20.1 min versus 14.2 min). The CHEOPS and “faces” pain scores were higher in the ketamine group 30 min after extubation, but were similar to the morphine group thereafter. One patient in each group required rescue morphine in recovery. The number of children requiring further postoperative analgesia and mean times to first analgesia were similar. The incidence of vomiting and dreaming during the first 4 hr after surgery was similar in the two groups. At 30 min after extubation, the mean respiratory rates were 20.5/min and 19.2/min in the ketamine and morphine groups, respectively, with no significant differences between the groups over the study period. No significant differences were recorded in sleep patterns or dreams between the groups during the first postoperative night. Based on the questionnaire, the numbers who felt pain relief to be good or excellent were similar. These results indicate that ketamine may be a suitable alternative analgesic for children undergoing tonsillectomy.
Tonsillectomy is a painful procedure. The optimal approach to postoperative pain relief in children after tonsillectomy remains to be seen. Ketamine is a drug that has been receiving increased attention recently for postoperative pain control. Not only is it analgesic at subanesthetic levels, but ketamine has been suggested to be effective in preemptive analgesia owing to its effect as an antagonist at the NMDA receptor. Intravenous ketamine has been shown previously to be better than placebo in tonsillectomy patients 1 (anyone surprised at that?). This study compared the effects of intramuscular ketamine with intramuscular morphine.
The authors conclude that ketamine may prove a useful alternative to morphine in children having a tonsillectomy. I’m a big fan of ketamine, and maybe it will, but let’s review their results:
Negative: Awakening time was longer in the ketamine group. Moreover, pain scores were higher in the ketamine group at 30 min postop.
Neutral: Pain scores were similar after 30 min. Postoperative analgesic requirements and the time to first analgesic were similar. There were no differences in vomiting or dreaming/hallucinations.
Summary: Ketamine may be an alternative, but to my reading of this paper offers no advantages. An abstract from my institution currently in press also suggests that ketamine alone in tonsillectomy has limited if any effect on preemptive analgesia.
Victor C. Baum M.D.
1. Murray WB, Yankelowitz SM, Le Roux M, Bester HF. Prevention of post-tonsillectomy pain with analgesic doses of ketamine. S Afr Med J 1987; 72:839–42.