Vancomycin Sequestration During Cardiopulmonary Bypass Surgery

Abstract Objective : The present study was designed to analyze vancomycin disposition in adult patients undergoing coronary bypass grafting during and following cardiopulmonary bypass (CPB). Methods : Coronary bypass surgery was performed on 11 adults with a mean age (SD) of 62.9 (9.0) years old, who received a mean (SD) vancomycin prophylactic dose of 12.7 (1.0) mg/kg in a mean period of 41 (0.7) min. Using a two-compartment open model for pharmacokinetic analysis, the following parameters were obtained: α half-life, minutes ( t 1/2α ); β half-life, hours ( t 1/2β ); apparent volume of distribution, ( V d l/kg); volume of the central compartment, ( V c l/kg), constant between the "central to the peripheral" compartment, (k 12 ); constant between the "peripheral to the central" compartment, (k 21 ); total area under the concentration–time curve, (AUC mg/l×h) and a vancomycin clearance, (Cl van ml/min), respectively. Results : The mean (SD) calculated pharmacokinetic parameters were: t 1/2α 17.6 (6) min, t 1/2β 8.4 (3.8) h, V d 0.803 (0.259) l/kg, V c 0.270 (0.162) l/kg, k 12 0.03 (0.015), k 21 0.012 (0.012), total AUC 10377.2 (3687.6) mg/l×h. The mean (SD) vancomycin clearance by the CPB machine was 9.51 (2.66) l/h, and the mean (SD) total vancomycin sequestrated by CPB was 331.7 (84) mg. A significant difference (6.3%; p =0.001) was measured between the mean measured AUC during CPB (1088.1±253.9) and the same calculated parameter (1160.2±282). Five minutes after starting CPB, a decrease in vancomycin level was detected; this difference was found to be nearly 11% in absolute values. Conclusions : This confirmatory study demonstrated that the vancomycin blood concentrations obtained during the study allow recommending a safety prophylactic dose of 12mg/kg in adults who undergo open-heart surgery under CPB conditions. Sequestration of vancomycin by the oxygenator or/and tubing system of the CPB machine had occurred and had been measured in this study.