Mohave Rattle Snake Envenomation Follow-up

Admit

Strongly consider admission for all Mohave rattlesnake envenomations. Because patients with severe Mohave envenomation may present with only minimal local tissue effects, underestimation of a significant injury can easily occur. Because of the relative infrequency of the injury, admitting all patients with suspected Mohave rattlesnake envenomations is probably prudent and cost effective.

Effects of Mohave rattlesnake envenomation may be prolonged and have been shown to improve with late administration of antivenom.

• Anaphylaxis

Discharge instructions should include the following:

• Return immediately if swelling worsens or pain becomes severe.
• Return immediately if any abnormal bleeding or bruising, dark tarry stools, or severe headache occur.
• Return for signs of wound infection, such as swelling, excessive tenderness, redness or streaks, heat, or drainage (pus).
• 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.
• Wound check at the physician's discretion on a case-by-case basis. Return to the ED or follow up every 3 days for 2 weeks with repeat CBC, PT/INR, and fibrinogen. Laboratory studies may need to be rechecked more or less frequently or for a longer or shorter duration on a case-by-case basis.

• Administer antihistamines and steroids if serum sickness develops.

• All hospitals should have enough antivenom to treat at least one patient. However, antidote stocking varies and shortages do occur. Therefore, if antivenom is not available at the presenting hospital, patients should be transferred to a facility where antivenom may be administered. However, if it is available, antivenom may be necessary to optimize stabilization of a patient prior to transfer.

• Never handle a rattlesnake, even if it is believed to be dead. Serious, even fatal, envenomations have been documented to occur after handling the decapitated head of a rattlesnake up to 90 minutes after it was severed.
• 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.
• Keep garage doors closed to prevent rattlesnakes from seeking shelter in garages.

• Rhabdomyolysis
• Infection
• Respiratory difficulty
• Death (rare)

Antivenom-associated complications

Anaphylaxis is a type I (immediate) hypersensitivity reaction that may be life threatening. It is characterized by urticaria, wheezing laryngeal edema, and shock. Some degree of anaphylaxis may occur in as many as 25% of patients given Antivenin (Crotalidae) Polyvalent. Risk factors include previous exposure to horse serum or antivenom or a history of reactive airways. Anaphylaxis is treated with epinephrine, antihistamines, steroids, and ventilatory/circulatory support. Although experience is limited, immediate hypersensitivity is less common after treatment with CroFab.^{[7, 8]}

Serum sickness is a type III (delayed) hypersensitivity reaction. It is characterized by fever, urticaria, lymphadenopathy, and arthritis and may occur 5 days to 3 weeks after Antivenin (Crotalidae) Polyvalent administration in as many as 50% of patients. Serum sickness is dose related and almost always occurs when more than 8 vials of antivenin (Crotalidae) polyvalent are administered. Although serum sickness can be an uncomfortable experience, it is usually benign and self-limited and is treated with steroids and antihistamines. Delayed hypersensitivity is much less common after treatment with CroFab, although experience with this relatively new medication is limited.

• Full recovery is usually anticipated.
• Before antivenom, estimates of mortality rates ranged from 5-25%.
• Because of the development of antivenom, rapid EMS transport, and emergency/intensive care, mortality rates have improved to 0.28% (or better) when antivenom is administered and to 2.6% when antivenom is not administered.

• Call professionals, such as animal control, to move snakes (if it is necessary to move the snake).
• Never attempt to handle, possess, or kill venomous reptiles.
• For patient education resources, visit eMedicine's Bites and Stings Center. Also, see eMedicine's patient education article Snakebite.