EFFECTS OF ENFLURANE AND ISOFLURANE ANESTHESIA ON THE PHARMACOKINETICS OF PANCURONIUM IN ADULT PATIENTS

Objective. To evaluate the effects of 1 MAC of enflurane or isoflurane anesthesia on the pharmacokinetics of pancuronium. Methods. Eighteen adult patients undergoing the elective plastic surgery were randomly d ivided equally into 3 groups, namely, Group 1 (control group), Group 2 (enflurane group) and Group 3 (isoflurane group). Anesthesia was main tained with thiopental and 67% N2O-O-2 in Group 1, 1 MAC enflurane in Group 2 and 1 MAC isoflurane in Group 3. After administration of a bol us of pancuronium 100 mu g / kg, an improved fluorimetric assay was us ed to determine the serum concentrations of pancuronium and the pharma cokinetic variables of pancuronium were calculated with a 3P(87) progr am. Results. The disposition of pancuronium may be well described math ematically by a two-compartment open model. The results showed that in comparison with the control group, patients in Group 2 and Group 3 ha d a longer T-1/2 beta and MRT. The patients in Group 2 had the slower K-10 and lower CL than those in the control group. There were no signi ficant differences among the three groups in T-1/2 alpha, V-1, V-2, V- dss, V-beta, K-21, K-12 and AUC. Conclusion. During enflurane and isof lur anesthesia, CL of pancuronium decreased, and T-1/2 beta and MRT of pancuronium were prolonged in our patients, so duration of the effect ive plasma concentrations of pacuronium was much longer. As a result, the effects of enflurane and isoflurane of the pharmacokinetics of pan curonium may be part of reason why two drugs extended the duration of neuromuscular depression produced by pancuronium.