AN EVALUATION OF THE ACCURACY OF PHARMACOKINETIC DATA FOR THE COMPUTER ASSISTED INFUSION OF ALFENTANIL

The accuracy of using average alfentanil pharmacokinetic datain a computer assisted infusion pump (TIAC) to predict alfentanilplasma concentrations was tested in 35 patients {divided intothree groups) receiving alfentanil and nitrous oxide in oxygenanaesthesia for lower and upper abdominal surgery. By frequentlymeasuring the arterial plasma concentration, it was possibleto determine the average prediction error for individual patientsand for groups of patients. For the groups, there were no significantsystematic over- or underpredictions of the alfentanil plasmaconcentrations (bias). However, there existed a moderate degreeof variability (imprecision) within the groups, caused by deviationsof measured and predicted plasma concentrations in the individualpatients within each group. As a result, prediction errors of22.2-32.5% can be expected with the average pharmacokineticdata used in this study to drive TIAC. It was concluded that,as a result of the moderate degree of imprecision, it is unwiseto rely totally on the absolute values of alfentanil plasmaconcentrations predicted by a computer-regulated infusion pumpsuch as TIAC. However, such devices can be used to attain rapidlya relatively stable plasma concentration that can be adjusted(titrated) to the requirements of an individual patient duringanaesthesia. Overhovenerstr. 12, 6131 B2 Sittard, The Netherlands^*Department of Anesthesia and Medicine (Clinical Pharmacology),Stanford University Medical Center, Stanford, California 94305,U.S.A.Department of Anesthesiology and Pharmacology, Emory UniversitySchool of Medicine, Atlanta, Georgia 30322, U.S.A.