Moccasin Envenomation Follow-up

Patients believed to have dry bites, in which no venom effects develop, should be observed for at least 8 hours. Close follow-up and/or recheck examination is recommended.

Patients who have minimal snake envenomation may be admitted for overnight observation, or they may be discharged if signs of envenomation do not progress for at least 8 hours.

Patients whose envenomation is severe enough to require antivenom should be admitted.

Several reports in the literature have documented instances in which patients who were initially discharged with a mild envenomation returned in several hours with significant injury and required antivenom and admission. However, because the denominator (patients who go home with no progression) is not known, it is unclear whether the strategy of admitting all patients with mild envenomation is cost-effective.

Regardless of the period of observations, patients who are discharged should be instructed to return to the hospital if pain or swelling increase or if new symptoms develop. Because patients at home rarely elevate their envenomated limbs consistently, some increase in swelling is expected during the first 1-3 days after the patient goes home. If not accompanied by increasing pain or other signs/symptoms, this is not a concern.

Discharge instructions should include the following:

• Keep the envenomated extremity elevated.
• Return immediately if swelling worsens or pain becomes severe.
• Return immediately if any abnormal bleeding or bruising, dark tarry stools, or severe headache occurs.
• Return for signs of wound infection, such as fever, worsening redness, or swelling immediately adjacent to the bite site, or drainage of pus. Because tenderness at the bite site, more generalized swelling, and lymphangitic streaking are common manifestations of the envenomation itself, these are less useful as signs of infection.
• Return or follow up if a fever, itchy rash, joint pain, or swollen lymph nodes occur any time during the next few weeks.
• Do not take nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen (Motrin, Advil), or naproxen (Naprosyn, Aleve) for 2 weeks after the snakebite. Acetaminophen (Tylenol) or a prescribed pain medication can be taken.
• Do not participate in contact sports, undergo elective surgery, or have dental work for 2 weeks after the snakebite.
• Drink plenty of liquids. Return if urine decreases in amount or becomes cola colored.
• Referral to a physical therapist or surgeon may be indicated.
• Patients who developed severe coagulopathy or thrombocytopenia should have these studies rechecked in 3 days, and as needed for signs of coagulation problems (eg, bleeding gums, easy bruising).

Administer antihistamines and steroids if serum sickness to antivenom develops.

Short courses of opioid pain medications are often required.

If indicated, patients may require transfer after stabilization to a facility where antivenom can be administered.

Never handle a venomous snake, even if it is believed to be dead.

Do not reach or step into places outdoors that are not visible.

At home, remove debris in which snakes might hide (eg, log piles). Remove items, such as bird feeders, that might attract snakes—seeds that fall from bird feeders attract rodents, which attract snakes.

Heavy clothing (such as hiking boots) may retard some strikes.

Young children should be closely supervised, and older children should be educated to avoid snakes.^[6]

Complications of envenomation may include the following:

• Bleeding
• Compartment syndrome
• Skin and soft tissue necrosis
• Rhabdomyolysis
• Infection
• Death

Antivenom-associated complications may include the following:^[19]

Immediate hypersensitivity reactions

Anaphylaxis is a type I (immediate) hypersensitivity reaction, which may be life threatening.

Anaphylactoid reactions are histamine release stimulated by rapid infusion of medications, such as antivenom, that do not involve immune system sensitization.

Both anaphylactic and anaphylactoid reactions may be characterized by urticaria, airway swelling, wheezing, and shock. Anaphylactoid reactions are related to the rate of infusion; anaphylactic reactions are not related to rate or dose.

Urticaria occurs in approximately 8% of patients treated with crotaline Fab antivenom; more severe reactions such as wheezing and hypotension occur in approximately 2%.

Immediate hypersensitivity is treated by halting the infusion and administering antihistamines, steroids, and epinephrine as needed. If continued antivenom therapy is necessary, it is often possible to complete the antivenom infusion, after appropriate therapy, at a slower rate.

Delayed hypersensitivity reactions

Urticaria has been reported in approximately 8% of patients treated with crotaline Fab antivenom; wheezing is reported in 2%, and serum sickness in less than 10%.

Serum sickness is a type III (delayed) hypersensitivity reaction.

Serum sickness is characterized by fever, urticaria or petechial rash, lymphadenopathy, and arthritis, that may occur 5 days to 3 weeks after antivenom administration. Although serum sickness is uncomfortable, it is usually benign and self-limited.

Nearly all patients fully recover after moccasin envenomation.

Some patients have long-term problems with limb pain and/or swelling, particularly after physical exertion. The proportion of patients that develop these sequelae and the impact of antivenom therapy on this incidence are not known.

Call professionals, such as animal control, to move snakes.

Never attempt to handle, possess, or kill venomous reptiles.

For excellent patient education resources, visit eMedicine's Bites and Stings Center. Also, see eMedicine's patient education article Snakebite.