PREDICTIVE ACCURACY OF MIDAZOLAM IN ADULT PATIENTS SCHEDULED FOR CORONARY SURGERY

Study Objective: To evaluate the predictive accuracy of midazolam during cardiac anesthesia so as to orient the selection of the most appropiate pharmacokinetic model for use in a computer-assisted continuous-infusion system. Design: Retrospective analysis. Setting: Operating room at a university hospital. Patients: 66 consecutive middle-aged and elderly coronary patients scheduled for coronary artery bypass graft (CABG) surgery. Interventions: Patients were anesthetized using a variable-rate infusion of alfentanil combined with midazolam in an attempt to achieve and maintain target concentrations of 100 ng/ml or 500 ng/ml. Measurements and Main Results: A total of 323 arterial blood samples were taken, and serum midazolam concentrations were measured by high performance liquid chromatography. Predicted midazolam concentrations were calculated using 3 selected data sets. Their bias, inaccuracy, and dispersion were assessed by determining the median performance error, the median absolute performance error (MDAPE), and the 10th and 90th percentiles. Two of the selected data sets of midazolam, with a clearance lower than 5 ml/kg/min, were very accurate (MDAPE less than 20%) in predicting low or high prebypass concentrations of midazolam in adult patients with good left ventricular function. Conclusions: Two of the 3 pharmacokinetic data sets of midazolam studied may be selected when using a computer-assisted infusion system in adult coronary patients.