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

Propofol is sequestered in extracorporeal circuits, but the factors respons ible for the phenomenon are mostly unknown. We have compared two extracorpo real circuits (oxygenators, reservoirs and tubings) coated with heparin wit h two corresponding uncoated circuits for their capacity to sequester propo fol in vitro. Three experiments were conducted with each circuit. The circu it was primed with a mixture of Ringer's acetate solution and whole blood, and the study conditions (pump flow, temperature, pH) were standardized. Pr opofol was added to the solution to achieve a concentration of 2 mu g ml(-1 ). These studies were followed with concentrations of 10- and 100-fold to a ssess possible saturation of propofol binding. Serial samples were obtained from the circulating solution far measurement of propofol concentration. P ropofol concentrations decreased to 22-32% of the initial predicted concent ration of 2 mu g ml(-1) in the circuits (no significant difference between circuits). With greater concentrations, the circuits did not become saturat ed with propofol, even with the highest predicted concentration of 200 mu g ml(-1). We conclude that propofol was sequestered in extracorporeal circui ts in vitro, irrespective of coating the circuit with heparin.