Pathophysiology
Clinical meaning
Venomous snake bites in North America primarily involve pit vipers (rattlesnakes, copperheads, cottonmouths) and coral snakes. Pit viper venom contains a complex mixture of proteolytic enzymes, phospholipases, metalloproteinases, and hemotoxins that cause local tissue destruction, coagulopathy, and systemic toxicity. Local effects include progressive edema, ecchymosis, and tissue necrosis. Hematologic effects include thrombocytopenia, hypofibrinogenemia, and prolonged PT/INR from consumption coagulopathy. Coral snake venom is primarily neurotoxic, causing descending paralysis starting with cranial nerve dysfunction (ptosis, dysphagia) progressing to respiratory paralysis. Approximately 20-25% of pit viper bites are 'dry bites' with no envenomation. CroFab (crotalidae polyvalent immune Fab) antivenom neutralizes pit viper venom when significant envenomation is present. Time to antivenom administration directly affects outcomes.