Effect site concentrations of propofol producing hypnosis in children and adults:: comparison using the bispectral index

Background: No study has determined the concentration of propofol producing a degree of hypnosis compatible with anaesthesia in children. As a result, concentrations determined in adults are recommended for children. As this can result in an inadequate depth of anaesthesia, we determined the predicted effect site concentration (C-e) of propofol necessary to obtain a bispectral index (BIS) of 50 in 50% (ECe50) of children and adults. Methods: Twenty adults (aged 33-44 years) and 20 children (aged 3-11 years) undergoing surgery under general anaesthesia were studied. All were monitored with a BIS monitor, and a target controlled infusion of propofol aiming for a constant C-e value was started. After 10 min, patients were evaluated using a sedation scale, and the last 5 min was used to determine the mean BIS for this C-e value. The C-e value of propofol was defined using the up-and-down method of Dixon and Massey. The first patient in each group received C-e = 6 mu g/ml; thereafter, it was modified in 0.5 mu g/ml decrements/increments with positive or negative responses, respectively. A positive response was BIS < 50 and a negative response was BIS >= 50. The ECe50 value was compared using unpaired Student's t-test. The prediction probability (P-K) was used to study the association between BIS and the sedation score. Results: The mean ECe50 (95% confidence interval) values were 3.75 mu g/ml (2.97-4.75 mu g/ml) in adults and 3.65 mu g/ml (3.36-3.96 mu g/ml) in children (not significant). All patients with BIS < 50 were unarousable with tactile stimulation. The P-K value was 0.99 in both groups. Conclusion: The predicted C-e value of propofol resulting in BIS = 50 was similar in adults and children aged 3-11 years. The predicted C-e value of propofol producing hypnosis in adults also seems to be useful in this paediatric population.