Platelet aggregation during and after cardiopulmonary bypass: effect of two different cardiotomy filters

Patients undergoing cardiopulmonary bypass with a membrane oxygenator were studied to determine the effects of two cardiotomy filters on platelet number and function. A Dacron wool filter removed significantly more microemboli than a 40 mu X 40 mu pore-mesh filter. Postoperatively, there were fewer platelets and a lower total volume of platelets in patients who had a Dacron wool filter in the extracorporeal circuit. However, the volume of adenosine diphosphate-induced aggregates was nearly identical in the two patient groups (p greater than 0.1). The study documents an increased number of circulating platelets after pore-mesh filtration, and suggests that the microaggregates reinfused during pore-mesh filtration represent aggregated platelets that dissociate and subsequently circulate in the patient but do not function.