Abstract
Snakebite is a significant and under-resourced global public health issue. Snake venoms cause a variety of potentially fatal clinical toxin syndromes, including venom-induced consumption coagulopathy (VICC) which is associated with major haemorrhage. A subset of patients with VICC develop a thrombotic microangiopathy (TMA). This article reviews recent evidence regarding snakebite-associated TMA and its epidemiology, diagnosis, outcomes, and effectiveness of interventions including antivenom and therapeutic plasma-exchange. Snakebite-associated TMA presents with microangiopathic haemolytic anaemia (evidenced by schistocytes on the blood film), thrombocytopenia in almost all cases, and a spectrum of acute kidney injury (AKI). A proportion of patients require dialysis, most survive and achieve dialysis free survival. There is no evidence that antivenom prevents TMA specifically, but early antivenom remains the mainstay of treatment for snake envenoming. There is no evidence for therapeutic plasma-exchange being effective. We propose diagnostic criteria for snakebite-associated TMA as anaemia with >1.0% schistocytes on blood film examination, together with absolute thrombocytopenia (<150 × 109/L) or a relative decrease in platelet count of >25% from baseline. Patients are at risk of long-term chronic kidney disease and long term follow up is recommended.
Highlights
Snakebite is a significant global public health issue
Scoring systems such as those used for the diagnosis of disseminated intravascular coagulation (DIC) [98], and the PLASMIC score used for predicting ADAMTS-13 < 10% in suspected thrombocytopenic purpura (TTP) [99], should not be applied in snakebite envenoming cases; 3
Snakebite should be considered as a condition associated with secondary thrombotic microangiopathy (TMA), but distinct from both TTP and haemolytic uraemic syndrome (HUS)
Summary
Snakebite is a significant global public health issue. Globally there are an estimated 2.7 million cases of snake envenoming, with an estimated 81,000–138,000 deaths per year attributed to snakebite [1]. Snakebite-associated TMA has been described in a variety of snake species known to cause VICC across all inhabited continents of the world [10,11,12,13,14]. Snakebite-associated TMA appears to be associated with predominant acute kidney injury (AKI) [10,15,16,17,18], in contrast to the major complication of VICC, i.e., bleeding [7]. Some studies have reported the AKI of snakebite associated TMA as self-limiting [17,20], whilst other small studies have claimed effectiveness of intervention with therapeutic plasma exchange (TPE) [12,21,22,23]. Better elucidating the features of snakebite associated TMA and best practice with respect to treatment is of global importance [3]. We review the epidemiology, presenting clinical and laboratory features, outcomes, and role of interventions including antivenom and TPE, and provide clinical practice recommendations based on latest evidence
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