You receive a phone call from a 27 y/o male patient at the Sweetwater, TX rattlesnake roundup who says he's been bitten on the arm by a rattlesnake. He's searching for advice on first aid. He mentions things like a tourniquet, sucking the venom out, and putting ice on the bite.

What is your advice? Why? Taking the scenario to the next step, what, if anything, would you recommend to the emergency room or his physician?

SELECT  here for discussion

** THANKS to Dr Annabel Schumaker for her help with this Pearl **

HELPFUL first aid tips include getting to the nearest hospital, keeping the patient calm (increased HR hastens distribution of the venom), removal of constrictive clothing or jewelry, washing the bite site with soap and water, reducing movement of extremity (treat as broken, maybe keep in a loose sling), and position at the level of the heart, if possible.

HARMFUL (i.e. Hollywood or "cowboy") first aid includes such actions as incision into the bite site and sucking out the venom, using ice, applying a tourniquet, or delaying medical care. These things should be avoided and, if done, may actually make the situation worse. For example, applying a tourniquet can exacerbate ischemia, infarction, and necrosis in a limb that already has decreased perfusion due to envenomation.

Signs and symptoms of envenomation by rattlesnakes may include local symptoms such as pain, swelling, bruising, erythrema or petechiae. Systemic symptoms may include effects on the cardiovascular, hematologic, neurological, pulmonary, renal, and GI systems. Seventy five percent of envenomations lead to clinical symptoms.

Medical treatment of significant symptoms should include 2 large bore IVs (generally NS or LR), elevation of the extremity, tetanus booster (esp if no booster within the last 10 years), cleanse wound, and release tourniquet(s) slowly, if applied. Vital signs should be taken frequently, and labs drawn q 4 hours (at least for 12 hours) to include: CBC (PLTs will be consumed due to local hemorrhage; anemia due to extravasation of erythrocytes), pT/aPTT will be elevated (venom has anticoagulant properties), fibrinogen and fibrin split products may present a DIC-like picture, urinalysis (evaluate for hematuria, hemoglobinuria and/or myoglobinuria), CPK to evaluate for rhabdomyolysis, and ethanol [EtOH] (snake bites and alcohol use/abuse are often associated frequently - go figure).

There is an antivenom available. The 'old' polyvalent antivenom (equine) is no longer produced. The 'new' antivenom [CroFab®] is an ovine derived immune Fab fragment. It is indicated for mild to moderate (no studies on severe-but used for these) envenomations. Initial dose is 4-6 vials, best given within 6 hours of the bite. Since CroFab® has a shorter persistence in the blood than crotalid venom that can leak from depot sites over time, repeat dosing is often required.  Repeat the 4-6 vial dose until there is complete arrest of local manifestations (swelling), and return of coagulation tests and systemic signs to normal.  Once this is accomplished, the manufacturer recommends additional 2-vial doses given every 6 hours for 3 doses.  No test dose is required but a slow infusion rate for the first 10 minutes is advised to watch for allergic reactions. Preparation of the antivenom requires reconstitution with 10 ml sterile water and further dilution of the dose in 250ml of 0.9% sodium chloride (NS). Use diluted antivenom within 4 hours of preparation. Other supportive measures should be employed, if necessary. Adverse reactions to the antivenom infusion may include hypotension, urticaria, and bronchospasm. Treat accordingly with SQ
epinephrine, H1/H2 blockers, steroids and/or beta agonists. Slowing the rate of infusion should allow completion of the infusion.

Fasciotomy may be indicated but rarely and only if a compartment syndrome is verified.

Serum sickness may occur as a delayed reaction (3 days to 3 weeks) to the antivenom. The risk of this is increased with the amount of antivenom administered. The patient presents with flu-like symptoms (myalgia, arthralgia, fatigue, rash), which are best treated with NSAIDs, antihistamines (i.e. diphenhydramine), and steroids, if necessary.