Clinical study of blood trauma during perfusion with membrane and bubble oxygenators

This clinical study was designed to show differences in hemostasis after perfusion with membrane (MO) or bubble (BO) oxygenators in cardiopulmonary bypass. These differences, however, may be obscured by other damaging factors, such as cardiotomy suction, various perfusion durations, or different types of operations. Therefore, only patients undergoing coronary artery bypass grafting were studied. During such operations, rather equal perfusion durations can be expected and mainly apex vent suction is used. Data on postoperative blood loss and transfusions were collected from two groups: one comprising 49 patients perfused with the Travenol TMO membrane oxygenator (MO group) and the other composed of 25 patients with the Polystan VT 5000 bubble oxygenator (BO group). In 10 patients of each group, blood samples were taken at frequent intervals for blood cell counts, for the determination of platelet function, hematocrit, hemoglobin, and plasma hemoglobin, for several coagulation tests, and for the assessment of kidney and liver function. Significant differences between the two groups were found for postoperative blood loss and transfusions, both higher in the BO group. Platelet function was better maintained in the MO group until the moment of releasing the aortic cross-clamp, after which it decreased concurrently with a doubling of the amount of suction. After protamine administration, an additional drop of platelet function occurred and there was virtually no platelet function left in either groups; however, it recovered 90 minutes after bypass, mainly in the MO group. This study shows that hemostasis is better preserved with MO perfusion. Still further improvements may be achieved by preventing the damage of suction and by a correct protamine dose.