Biocompatibility of three different membrane oxygenators: effects on complement, neutrophil and monocyte activation

The inflammatory reaction of extracorporeal circuits can be assessed by measuring complement activation and the release of activation markers of leucocytes. The purpose of this study was to compare three commercially available membrane oxygenators with respect to complement (C3a), granulocyte (lactoferrin) and monocyte (interleukin-6, IL-6) activation. Thirty patients undergoing cardiac surgery were randomly assigned to undergo cardiopulmonary bypass (CPB) with one of the following oxygenators: a polypropylene hollow-fibre membrane (group 1; 2.2 m2), a polypropylene flat-sheet membrane (group 2; 3.1 m2) or a silicone envelope membrane (group 3, 3.5 m2). In all patients, a significant increase in C3a in plasma occurred during CPB with peak levels after the administration of protamine sulphate. In blood samples taken before aortic crossclamp release, at the end of CPB, and 20 min after protamine administration C3a was significantly lower in group 1 than in the other two groups. Lactoferrin increased significantly during CPB in all patients without a significant difference between the groups. IL-6 did not increase during CPB, but raised significantly after 4 h in the intensive care unit in all groups. Moreover, IL-6 was significant lower in group 1 than group 3. The data suggest that the polypropylene hollow-fibre membrane oxygenator, i.e. the oxygenator with the smallest surface area, is more biocompatible than the other types, probably because of a smaller contact surface area.