CURRENT Essentials of Critical Care.pdf

Chapter 17 Environmental Injuries 255■■■SnakebiteEssentials of Diagnosis• 95% of poisonous bites from Crotalidae or pit vipers, includingrattlesnakes, cottonmouths, copperheads; 5% from Elapidae(coral snakes)• Crotalid envenomations: swelling, erythema, ecchymosis, perioralparesthesias, coagulopathy, hypotension, tachypnea, andrespiratory compromise; bites characterized by two fang marks• Elapidae envenomations: delayed 1–12 hours, include paralysis,respiratory compromise• Severity of envenomation estimated by rate of progression ofsigns, symptoms, coagulopathy; mild with only local effects;moderate with non-severe systemic effects, minimal coagulopathy;severe with life-threatening hypotension, altered sensorium,severe coagulopathy and thrombocytopeniaDifferential Diagnosis• Sepsis • Insect or spider bites• Toxin or chemical ingestion or inhalationTreatment• Maintain airway in bites of head and neck, or when respiratorycompromise present• Fluid resuscitation for hypotension• Two crotalid antivenoms available: Antivenom (Crotalidae)Polyvalent (ACP) and newer Crotalidae Polyvalent Immune FabOvine (FabAV); antivenom recommended for crotalid envenomationswith severe signs and symptoms or with progression,particularly coagulopathy or hemolysis• Give ACP slowly: 2–4 vials for minimal envenomation, 5–9vials for moderate, 10–15 for severe; perform skin test with ACPbefore administration to predict allergic reaction; 15–20% withmoderate to severe antivenom reactions (treat with diphenhydramineand antihistamines)• Reactions infrequent with FabAV; administer 3–12 vials initially,followed by 2 vials at 6, 12, and 18 hours• Watch extremities for evidence of compartment syndrome■ PearlTo distinguish between bites of the poisonous coral snake and nonpoisonousking snake, use this mnemonic: “red on yellow (coral), killsa fellow; red on black (king), venom lack.”ReferenceGold BS et al: Bites of venomous snakes. N Engl J Med 2002;347:347. [PMID:12151473]