A COMPARISON OF 3 INDUCTION-AGENTS IN PEDIATRIC ANESTHESIA - CARDIOVASCULAR EFFECTS AND RECOVERY

We studied 30 children undergoing circumcision randomly allocated to r eceive either thiopentone 4 mg.kg-1, propofol 2.5 mg.kg-1 or midazolam 0.5 mg.kg-1 (n = 10) IV over 30 seconds at induction of anaesthesia. Blood pressure and pulse rate during the first 15 minutes of induction were recorded by a Finapres 2300e and a Cardiocap CM-104, and changes from preinduction baseline compared between the three induction agent s and the two recording instruments. Postoperatively, blood levels of the induction agents were measured and recovery from anaesthesia was a ssessed by clinical criteria, mood and sedation scores and psychomotor performance. The Cardiocap data revealed no statistically significant haemodynamic differences between the three induction agents. Finapres data demonstrated that propofol caused a greater decrease in mean art erial pressure when compared to thiopentone at one minute (P = 0.01) a nd the MAP remained significantly lower than midazolam at five minutes (P = 0.02), illustrating an advantage of continuous over intermittent non-invasive blood pressure monitoring. The midazolam group took long er to identify themselves compared to both the propofol (P = 0.005) an d the thiopentone groups (P = 0.02), but there was no difference in th e groups in time to eye-opening. Psychomotor performance on awakening was significantly worse in the midazolam group compared to the propofo l (P < 0.03) and thiopentone groups (P < 0.02). Most children had reco vered to 80% of their best, practised, unmedicated, preoperative perfo rmance four hours after awakening, irrespective of the induction agent administered. Drug blood levels correlated weakly with both methods o f psychomotor assessment (r greater-than-or-equal-to 0.6). Of the thre e induction agents, thiopentone caused the least haemodynamic perturba tion on induction, and anaesthesia induced with midazolam caused the g reatest psychomotor impairment on awakening. Within one hour patients in all drug groups were equally awake, co-operative and co-ordinated.