Haemostatic effects in vivo after snakebite by the red-necked keelback (Rhabdophis subminiatus)

We describe a patient who developed a severe coagulopathy after being bitten by a red-necked keelback snake (Rhabdophis subminiatus), a species which is generally considered non-venomous. The patient's blood was incoagulable due to complete depletion of fibrinogen. Comprehensive coagulation studies were performed to identify the mechanism(s) by which the snake toxin caused the coagulopathy. It was found to contain a potent prothrombin activator, probably an activator of protein C and possibly also a factor X activating enzyme. The fibrinolysis was secondary to intravascular fibrin formation; there were no indications for a direct fibrinogenolytic activity in the snake toxin. Remarkably, there was virtually no consumption of antithrombin III, despite extensive thrombin formation; this feature appears to be not uncommon after snake bites, but is still unexplained.