Coating of extracorporeal circuit with heparin does not prevent sequestration of propofol in vitro

Abstract

Propofol is sequestered in extracorporeal circuits, but the factors responsible for the phenomenon are mostly unknown. We have compared two extracorporeal circuits (oxygenators, reservoirs and tubings) coated with heparin with two corresponding uncoated circuits for their capacity to sequester propofol in vitro. Three experiments were conducted with each circuit. The circuit was primed with a mixture of Ringer's acetate solution and whole blood, and the study conditions (pump flow, temperature, pH) were standardized. Propofol was added to the solution to achieve a concentration of 2 μg ml-1. These studies were followed with concentrations of 10- and 100-fold to assess possible saturation of propofol binding. Serial samples were obtained from the circulating solution for measurement of propofol concentration. Propofol concentrations decreased to 22-32% of the initial predicted concentration of 2 μg ml-1 in the circuits (no significant difference between circuits). With greater concentrations, the circuits did not become saturated with propofol, even with the highest predicted concentration of 200 μg ml-1. We conclude that propofol was sequestered in extracorporeal circuits in vitro, irrespective of coating the circuit with heparin.