Studies of the effect of Pall leucocyte filters LG6 and AV6 in an in vitro simulated extracorporeal circulatory system

Neutrophil activation is thought to play a major role in the inflammatory response seen in reperfusion injury and similar clinical situations, i.e. extracorporeal circulation. lmpairment of neutrophil function or reduction of total numbers of neutrophils using a leucocyte filter may be beneficial in reducing the adverse clinical effects. In this study we have investigated the effect of the Pall LG6 and control AV6 filters during simulated in vitro cardiopulmonary bypass (CPB). Various parameters were evaluated including neutrophils, total leucocytes, monocytes, lymphocytes and platelets, expression of antigens on neutrophils using a panel of leucocyte-associated monoclonal antibodies CD13, 14, 15, 45Ro, 67,11a, 11 b and L selectin. The effects of leucocyte stimulation with phorbol myristate acetate (PMA) and a leucocyte bolus from a patient with chronic myeloid leukaemia (CML) were also investigated. We have demonstrated that the LG6 significantly reduces leucocytes, in particular neutrophils, with a modest reduction of lymphocytes, platelets and haematocrit, whereas the AV6 had no effect on leukocytes or neutrophils in the test system. In addition the LG6 was associated with a reduction in expression of all leucocyte antigens by approximately 20%; however there was no appreciable alteration of any of the antigens with AV6. Leucocyte stimulation with PMA resulted in a dramatic decrease of all cellular elements and an extra leucocyte load (using CML leucocytes) was not effectively filtered by the LG6 filter. These studies identify the capacity of the LG6 as compared with the AV6 to deplete activated neutrophils in an in vitro simulated cardiopulmonary bypass circuit.