Snakebite Doesn't Cause Disseminated Intravascular Coagulation: Coagulopathy and Thrombotic Microangiopathy in Snake Envenoming

The most common coagulopathy associated with snake envenoming worldwide is venom-induced consumption coagulopathy (VICC), which results from activation of the coagulation pathway by snake toxins including thrombin-like enzymes, prothrombin activators, and factor X activators. VICC has often been likened to disseminated intravascular coagulation (DIC) because of the elevated D-dimer, prolonged prothrombin time, and low fibrinogen. However, VICC is not characterized by other important features of DIC, such as evidence of systemic microthrombi and end-organ failure. In addition, the time course of VICC differs with rapid onset and resolution, and the mechanism of initiation of coagulation activation differs because thrombin generation in DIC is mediated by the tissue factor/factor VIIa pathway. In a proportion of patients with VICC, a clinical syndrome consistent with thrombotic microangiopathy has been reported and is characterized by acute renal failure, thrombocytopenia, and microangiopathic hemolytic anemia. This thrombotic microangiopathy appears to only occur in conjunction with VICC but in several different snakes worldwide including vipers and elapids. Consistent with thrombotic microangiopathy, it progresses despite the resolution of the coagulopathy, suggesting a distinct but related process. The existence of the overlapping clinical syndromes of VICC and thrombotic microangiopathy in snake envenoming is the likely reason for the mistaken idea that snakebite causes DIC.