A Comparison of Three Induction Agents in Paediatric Anaesthesia—Cardiovascular Effects and Recovery

Abstract

We studied 30 children undergoing circumcision randomly allocated to receive either thiopentone 4 mg.kg-I , propofol2.5 mg.kg-I or midazolam 0.5 mg.kg-I (n=JO) 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-J04, and changes from preinduction baseline compared between the three induction agents and the two recording instruments. Postoperatively, blood levels of the induction agents were measured and recovery from anaesthesia was assessed 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 arterial pressure when compared to thiopentone at one minute (P=0.01) and 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 longer to identify themselves compared to both the propofol (P= 0.005) and the thiopentone groups (P=0.02), but there was no difference in the groups in time to eye-opening. Psychomotor performance on awakening was significantly worse in the midazolam group compared to the propofol (P< 0.03) and thiopentone groups (P< 0.02). Most children had recovered to 80% of their best, practised, unmedicated, preoperative performance four hours after awakening, irrespective of the induction agent administered. Drug blood levels correlated weakly with both methods of psychomotor assessment (r ~ 0.6). Of the three induction agents, thiopentone caused the least haemodynamic perturbation on induction, and anaesthesia induced with midazolam caused the greatest psychomotor impairment on awakening. Within one hour patients in all drug groups were equally awake, co-operative and co-ordinated.

A randomised placebo‐controlled trial of the effects of midazolam premedication on children's postoperative cognition

“…The present study extends the latter results by showing that buccal premedication with 0.2 mg.kg )1 midazolam is associated with significant further slowing of reaction time and impairment of fine motor control at the time of discharge. The results are broadly consistent with those of Jones et al [9] in their study of induction with 0.5 mg.kg )1 midazolam, propofol or thiopental, and maintenance with nitrous oxide and halothane in children aged 4-12 years, all of whom received intravenous Table 2 The number of children correctly recalling and recognising pictoral stimuli postoperatively prior to discharge (recall only), and 48 h later at home, as a function of premedication with midazolam or placebo. Children having placebo correctly recalled significantly more postoperatively (p = 0.014) and at 48 h (p = 0.012), and correctly recognised more stimuli at 48 h (p < 0.001), than those having midazolam.…”

Dosage scheme for propofol in children under 3 years of age

“…In the adapted scheme, the dosage in the youngest age group is relatively the highest and is lower for older age groups. This was based on the model of partition of propofol, which is a 3‐compartment model (3– 6,11– 16).…”

“…We found that relatively more propofol was needed, especially in the youngest age groups, to fill the central compartments, but with a longer duration the dosage had to be reduced relative to older patients because of slower metabolism of the drug and other properties of the compartments in children of these age groups (11– 13,16– 18,21).…”

“…In cases where bradycardia was more then 15% of the initial frequency, we gave atropine 0.01 mg·kg −1 with a good response. The younger the child, the more often we saw bradycardias over 15%, but they always responded well to atropine (1,5,7,8,11,16,22,24,25).…”

“…The falls in blood pressure could be caused by anaesthesia or from surgical blood loss. In these cases, we gave extra intravenous fluids as Ringers lactate, NaCl 0.9%, haemaccel or HES 6% 20 ml·kg −1 with good results (11,12,16,18,22,24,25).…”