The mechanisms of platelet dysfunction during extracorporeal membrane oxygenation in critically ill neonates

Objective: Although bleeding associated with thrombocytopenia often complicates extracorporeal membrane oxygenation (ECMO), the mechanisms of platelet dysfunction during ECMO remain poorly understood, We investigated the role of matrix metalloproteinase (MMP)-2, which recently has been shown to mediate a novel pathway of platelet aggregation, in the platelet dysfunction induced by ECMO, Design: Prospective longitudinal case study. Setting: Level III neonatal intensive care unit. Patients: Ten neonates treated with ECMO, Intervention: ECMO procedure. Measurements: Platelet counts and collagen-induced platelet aggregation ex vivo; plasma markers of platelet (soluble P-selectin) and endothelial (soluble E-selectin and total nitrite/nitrate) activation; plasma MMP-2 and MMP-9 activities; and concentrations of tissue inhibitors of MMPs, Main Results: During ECMO, time-dependent platelet activation, as evidenced by thrombocytopenia, decreased platelet aggregation, and increased plasma soluble P-selectin concentrations were found in the absence of endothelial activation, as shown by normal plasma concentrations of soluble E-selectin and nitric oxide metabolites (nitrite/nitrate). There was a time-dependent increase in plasma MMP-2 but not MMP-9 activity; tissue inhibitors of MMPs were not detected. Plasma soluble P-selectin concentrations significantly correlated with simultaneous plasma MMP-2 (r(2) = .37, p < .0001) but not with MMP-9 activities. Platelet dysfunction persisted despite repeated platelet transfusions to maintain platelet counts >100 x 10(9)/L. Conclusions: ECMO resulted in the activation of platelets but not endothelial cells. During ECMO, platelet dysfunction persisted despite platelet transfusions. MMP-2 may play a role in the development of platelet dysfunction caused by ECMO.