| | Limit ambulation (carry victim, if possible) Splint affected limb below heart level Except for Gila monster, copperhead, water moccasin, or pygmy rattle-snake envenomations, consider pressure and immobilization if substantial delay in treatment or neurotoxic features are expected Remove all constrictive clothing and jewelry from extremities Give fluids as tolerated (not orally, if possible) and acetaminophen; withhold other medications until after medical evaluation, if possible Arrange urgent transport to medical facility; if possible, notify facility before arrival Contraindicated: cryotherapy, ice, NSAIDs (may cause bleeding), constricting ligatures, incision and/or suction, illicit drugs, alcohol
| Local pain Fang marks may be present, but are often undetectable Edema (may be rapidly progressive) Ecchymoses (may become massive without treatment) Hemorrhagic blisters or blebs Compartment syndrome (uncommon) Systemic effects (e.g., lymphadenopathy, lymphangitis, nausea, vomiting, perioral paresthesia, metallic taste, hypotension, hypertension [particularly in Gila monster envenomation], diarrhea, vertigo, shock, hyperreactive airway, loss of consciousness) Paralytic features (e.g., weakness, ptosis, respiratory distress, bulbospinal paresis) Occasionally, dark urine (e.g., myoglobinuria/rhabdomyolysis)
| |
| Treatment |
| Large-gauge IV access for fluids; provide fluid bolus and repeat as indicated |
| Anaphylaxis protocol |
| Intubation and ventilation may be necessary in envenomations with paralytic features (e.g., from Mojave rattlesnake [Crotalus scutulatus scutulatus]) |
| Wound care and supportive management (e.g., fluid resuscitation, nonsedating analgesia, monitoring of patients with comorbidities) are essential for Gila monster envenomations |
| General treatment considerations: |
| Compartment syndrome requiring surgical intervention is a relatively uncommon complication of pit viper envenomation that may be confused with direct venom-induced muscle necrosis. Wick catheter or other intracompartmental pressure measurement > 30 mm Hg is required for diagnosis. If compartment syndrome is present, urgent surgical consultation is required. |
| Additional treatments may include nonsedating analgesia, coagulation factor and platelet replacement (controversial; currently under investigation), dialysis for established renal failure, urine alkalinization for myoglobinuria (uncertain value), and respiratory support as indicated. |
| After administration of antivenom, a short, nontapered course of prednisone (40 to 60 mg daily for five days) should be given to decrease the incidence of type III immune complex disease. Wound care and tetanus prophylaxis should be provided as indicated. Antibiotics are indicated only if evidence of infection is present. |
| Antivenom indications:‡ |
| A grading system may be used to approximate the degree of envenomation, but should be balanced with individual presentation and comorbidities:§ |
| 0 = nonenvenomation (“dry” bite). Fang marks may or may not be visible; no local or systemic effects. Antivenom is not indicated. |
| 1 = minimal envenomation. Local effects (pain, edema) are limited to the bite site; no systemic effects or laboratory abnormalities. Antivenom is not usually needed, but may be given if clinical progression occurs. |
| 2 = moderate envenomation. Extension of local effects, but the entire bitten extremity is not involved; systemic signs (e.g., nausea, vomiting, metallic taste); some laboratory abnormalities (e.g., thrombocytopenia, prolonged INR, elevated CPK level). Antivenom is required. |
| 3 = severe envenomation. Rapidly progressing edema; blistering and ecchymoses; shock; altered sensorium; multiple laboratory abnormalities (e.g., markedly prolonged INR, severe thrombocytopenia [platelet count < 20,000 mm3]); fibrin degradation products; renal insufficiency or failure. Antivenom is required with a high initial dose. Large subsequent doses are often required. |
| Antivenom dosing and administration: ‖ |
| Give Crotalidae polyvalent immune Fab (ovine): 4 to 6 vials, each reconstituted (10 mL saline) and diluted in 250 mL saline, IV administration. |
| Initial infusion of 20 to 60 mL per minute; increase to 250 mL per hour if no adverse reactions occur. |
| Give additional 4 to 6 vials, followed by 2 vials every six hours for 18 hours (14 to 18 vials total) as indicated; higher doses may be required for severe envenomations. |
| Presynaptic envenomation by species such as Mojave rattlesnakes may require higher doses and may be ineffective in late presentations, requiring intubation and ventilation. |
| Delayed absorption of sequestered venom is possible; because of the variably short half-life of the antivenom (12 to 23 hours), serial assessment of INR is essential (e.g., reversal of prolonged INR is sufficient to withhold further antivenom, but INR must be monitored for 24 to 48 hours [sometimes longer]). |
| All patients with serious envenomation must be counseled about the risk of antivenom anaphylaxis, immune complex disease, and possible loss of function, regardless of treatment effectiveness. |
|
| | | Local pain (variable, usually mild) Fang marks often undetectable Weakness Ptosis Respiratory distress (respiratory support may be indicated) Bulbospinal paresis
| |
| General treatment considerations (as with pit vipers and Gila monster) |
| Antivenom indications: ¶ |
| Any evidence of paralytic signs is an indication for antivenom; use of a grading system is strongly discouraged. |
| Antivenom dosing and administration: |
| Initial dosage is dependent on the product; give additional vials as needed. |
| Consultation with a toxinologist is strongly advised, as is review of the Antivenom Index (http://www.pharmacy.arizona.edu/avi/index#top [subscription required]). |
| All patients with serious envenomation must be counseled about the risk of antivenom anaphylaxis, immune complex disease, and possible loss of function, regardless of treatment effectiveness. |