Accuracy of target-controlled infusion of propofol for cardiac valve replacement performed under cardioplmonary bypass

Objective To investigate the performance of target-controlled infusion(TCI)of propofol for cardiac valve replacement performed under cardiopulmonary bypass(CPB).Methods Twenty ASA Ⅱ or Ⅲ patients aged 25-64 yr weighing 50-70 kg undergoing cardiac valve replacement under CPB were enrolled in this study.Anesthesia Was induced with intravenous midazolam,fentanyl and recuronium and maintained with intravenous midazolam infusion(0.05-0.1 mg·kg-1·h-1),TCI of propofol(target plasma concentration War set at 1 μ/ml),intermittent iv boluses of fentanyl and iv recuronium infusion(0.05-0.1 mg·kg-1·h-1).Propofol Was administered with a specific TCI system incorporating the Tackley pharmacokinetic parameters.Blood samples were obtained from radial artery before CPB(T1,baseline),at 1,5,10,20,40,60 min of CPB(T2-7)and 5,10 min after CPB(T8,9)for measurement of propofol plasma concentration by HPLC.Median prediction performance error (MDPE),median absolute performance error(MDAPE),wobble and divergence of propofol TCI system were calculated.Results The measured plasma concentrations of propofol were significantly higher at T1 than the target plasma concentration(Cp)but there were no significant differences between the measured plasma concentrations and Cp of propofol at T2-4.The measured plasma concentrations of pmpefol were significantly higher than Cp at T5-9.The MDPE,MDAPE,wobble and divergence of propofol TCI system were 21%.29%,21%and-0.06%/h respectively.Conclusion The accuracy of the TCI system incorporecting the Tackley pharmacoki-netic parameters exceeds the clinically acceptable scopein patients undergoing cardiac valve replacement under CPB. Key words: Cardiopulmonary bypass; Drug delivery systems; Propofol; Plasma concentration; Pharmacokinetica