The use of propofol infusions in paediatric anaesthesia: a practical guide.

Children require higher infusion rates of propofol than adults to maintain clinical anaesthesia. We aimed to produce a manual infusion regimen capable of maintaining a steady-state blood concentration of 3 microg ml(-1) in children aged 3-11 years. Pharmacokinetic parameter estimates were taken from published studies of infusion data in children and used in a pharmacokinetic simulation programme to predict likely propofol blood concentrations during infusions. A variability of 5% was allowed about the target concentration of 3 microg ml(-1). A loading dose of 2.5 mg x kg(-1) followed by an infusion rate of 15 mg x kg(-1) x h(-1) for the first 15 min, 13 mg x kg(-1) x h(-1) from 15 to 30 min, 11 mg x kg(-1) x h(-1) from 30 to 60 min, 10 mg x kg(-1) x h(-1) from 1 to 2 h and 9 mg x kg(-1) x h(-1) from 2 to 4 h resulted in a pseudo-steady state target concentration of 3 microg x ml(-1) in children 3-11 years. We were unable to predict similar rates by applying size models to adult data. The context sensitive half-time in children was longer than in adults, rising from 10.4 min at 1 h to 19.6 min at 4 h compared to adult estimates of 6.7 min and 9.5 min, respectively. Children require higher infusion rates than adults to maintain steady state concentrations of 3 microg x ml(-1) and have longer context sensitive half-times than adults. These differences can be attributed to altered pharmacokinetics in this age group.