PF4 and Sepsis: Therefore, heparin increases the risk of hemorrhages and can also cause heparin-induced thrombocytopenia (HIT), which is induced by antibodies that target complexes of platelet factor 4 (PF4) and heparin and is manifested by thrombotic events.3 The diagnosis of HIT, detected in ~1–3% of heparin-treated children,3 can be masked by other causes of thrombocytopenia and thrombosis, including the activation and destruction of platelets in the extracorporeal circuit, the peripheral consumption of platelets during sepsis and MOD, and other illnesses that induce AKI and thrombocytopenia (e.