How should I treat a dog envenomated by a pit viper including antivenom indications and monitoring?

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Pit viper envenomation in dogs is managed with antivenom, IV fluid support, analgesia, and close monitoring for coagulopathy, cardiac arrhythmias, and acute kidney injury. Between 150,000 and 300,000 animals are bitten by pit vipers in the US annually, and overall mortality following crotalid envenomation ranges from 1% to 30%, with neurotoxic envenomation carrying mortality up to 17.6%.112 Antivenom is the cornerstone of treatment and should be administered as early as possible. Indications for antivenom include rapid progression of swelling, severe coagulopathy, defibrination, thrombocytopenia, neuromuscular dysfunction, and shock.1 Antivenom is most effective when given immediately after envenomation, but benefit can still be realized long after envenomation if circulating venom remains present.1 In mild cases or those with only localized tissue effects, antivenom may not be necessary.1 The average case requires approximately 2 vials of polyvalent crotalid antivenom, though doses ranging from 1 to 20 vials have been reported.3 Severe or persistent cases may require substantially more — up to 22 vials over 7 days has been documented.4 Antivenom infusion reactions are a recognized risk; preparation and administration should follow manufacturer instructions, including appropriate dilution in crystalloid fluid, use of a blood filter, and gradual rate escalation with continuous monitoring.9 High cumulative antivenom doses have been associated with both type I (anaphylaxis) and type III (serum sickness) hypersensitivity reactions.4 Supportive care should begin immediately and includes IV isotonic crystalloid fluids, analgesia, and antiemetics. One documented protocol used hydromorphone 0.05 mg/kg IV q6h, maropitant 1 mg/kg IV q24h, and carprofen 4.4 mg/kg SC once.1 Potassium supplementation should be added to fluids when hypokalemia is present.1 Blood products are indicated for anemia and persistent bleeding.2 Coagulopathy monitoring is essential throughout hospitaliza