Influence of a defoaming agent upon the hematological complications of pump oxygenators.

Measurements of plasma hemoglobin values were made at many different sites of a Cross-Kay disk pump oxygenator during extracorporeal bypass in patients undergoing reparative valve surgery. Hemoglobin values were always higher in the line of the aspirator and defoaming chamber than in any other part of the system. Sampling immediately proximal and distal to the defoaming chamber revealed significant increases in plasma hemoglobin values as a result of the defoaming process. Studies of the hematological effects of the defoaming agent, polymethylsiloxane, which coats the disposable stainless steel sponge in the defoaming chamber, showed it greatly reduced the resistance of red cells to lysis by mechanical trauma. Similar studies of plasma showed the hemolytic effects of the defoaming agent are to some extent mediated by the plasma. It is concluded that the widely used defoaming agent, polymethylsiloxane, contributes to the hemolytic action of the bubbling, suctioning, and defoaming processes during open heart surgery. The addition of a water soluble surfactant material, that stabilizes emulsions (Pluronic F68), blocked or prevented the hemolytic process without interfering with the action of the antifoam material.