Platelet function during cardiac operation: comparison of membrane and bubble oxygenators

The effects of cardiopulmonary bypass with bubble and membrane oxygenator systems on platelet function were studied in 26 patients who had elective coronary arterial bypass grafts. Fourteen patients were perfused with spiral coil membrane oxygenator systems, 12 with bubble oxygenator systems. During and after bypass, platelet counts decreased in both groups; however, when corrected for dilution, platelet counts did not change significantly in patients perfused with membrane oxygenators and increased slightly but significantly in those perfused with membrane oxygenators and increased slightly but significantly in those perfused with bubble oxygenator systems. During and 1 hour after bypass, the concentration of adenosine diphosphate (ADP) required to cause complete aggregation increased in both groups. Plasma low affinity platelet factor 4 (LA-PF4) increased significantly during and after bypass in both groups. However, the concentration of platelet adenine nucleotides and LA-PF4, measured only in patients perfused with membrane oxygenator systems, did not change. Bleeding times increased postoperatively in both groups and 18 hour blood losses were similar. Cardiopulmonary bypass with membrane and bubble oxygenator systems causes qualitatively similar losses in sensitivity to ADP and similar increases in bleeding times. The mechanism by which platelets are altered during cardiopulmonary bypass in obscure but is not due to partial depletion of granule contents in patients perfused with membrane oxygenators.