The respiratory effects of tramadol in children under halothane an anaesthesia.
In a randomised double-blind, placebo-controlled study, the respiratory effects of intravenous tramadol (1 mg or 2 mg.kg-1) were compared with intravenous pethidine 1 mg.kg-1 under halothane anaesthesia. Children, ASA 1-2 between 2 and 10 years, presenting for inguinal surgery were studied. Once a steady state for halothane was reached, baseline recordings of end-tidal carbon dioxide, oxygen saturation, respiratory rate, tidal volume, minute volume, blood pressure and pulse rate were recorded. Intravenous tramadol 1 mg.kg-1 (T1) or 2 mg.kg-1 (T2) or pethidine 1 mg.kg-1 (PE) or placebo (PL) was then given according to a computer-generated randomisation. Further sets of recordings were taken at 5-min intervals for 20 min prior to commencement of surgery. The rate of recovery was assessed according to Aldrete scoring and the time and need for further analgesia were noted. The postoperative pain intensity was scored by means of a five-point verbal rating scale hourly for 6 h. Eighty-eight children, 22 per group, were studied. The mean age, weight and height were similar in each group. There was a statistically significant difference between the maximum decrease in respiratory rate and increase in end-tidal carbon dioxide between group PE and groups T1/T2 (p < 0.001). Thirteen episodes of apnoea occurred in the PE group, 11 requiring naloxone. The mean respiratory rate was lowest 5 min after injection in all groups. There was a slow increase in respiratory rate until incision in groups T1 and T2. Respiratory rate remained almost unchanged in PL until incision. The decreases in respiratory rate were reflected by increases in end-tidal carbon dioxide, the highest being recorded in the PE group. A lower intensity of pain in the first 2 h was noted in the three opioid groups. During the first 6 h, the proportion of patients requiring a further dose of analgesia was highest in PL and lowest in T2. Tramadol appears safe for use in children.