Mojave Rattlesnake Envenomation Treatment & Management

Updated: Jun 15, 2018
  • Author: Sean P Bush, MD, FACEP; Chief Editor: Joe Alcock, MD, MS  more...
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Treatment

Prehospital Care

Do nothing to injure the patient or impede travel to the ED.

Provide general support of airway, breathing, and circulation per advanced cardiac life support (ACLS) protocol; use oxygen, monitors, 2 large-bore intravenous lines (but minimize sticks when possible), and fluid challenge. In addition, minimize activity (if possible), remove jewelry or tight-fitting clothes in anticipation of swelling, and transport the patient to the ED as quickly and as safely as possible. Mark and time the border of advancing tenderness and edema often enough to gauge progression. No benefit was demonstrated when a negative pressure venom extraction device (eg, The Extractor from Sawyer Products) was evaluated in recent studies. [14, 15] Incision across fang marks is not recommended. Mouth suction is contraindicated.

Maintain the extremity in a neutral position of comfort.

Lymphatic constriction bands and pressure immobilization techniques may inhibit the spread of venom, but whether they improve outcome is not clear. These techniques may actually be deleterious for pit viper envenomation if they increase local necrosis or compartment pressure. [16] Special consideration of these techniques may be warranted for confirmed Venom A Mojave rattlesnake bites because local tissue injury is usually less. However, this application has not specifically been studied. Furthermore, it may not be possible to distinguish Venom A from Venom B snakes just by looking at the snake. The use of tourniquets is not recommended.

First aid techniques that lack therapeutic value or are potentially more harmful than the snakebite include electric shock, alcohol, stimulants, aspirin, ice application, and various folk and herbal remedies. Cost and risk of acute adverse reactions generally preclude field use of antivenom.

Although identification of the snake in suspected Mojave rattlesnake bites may be helpful, attempts to capture or kill the snake are not recommended because of the risk of additional injury. [17] If the venomousness of a particular snake is uncertain, consider taking photographs of the snake from a safe distance of at least 6 feet away using a digital or Polaroid camera.

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Emergency Department Care

Adequate hydration with intravenous fluids is indicated. Patients with hypotension should be resuscitated first with 2 isotonic sodium chloride solution challenges (eg, 20 mL/kg). Treat persistent shock with colloids, followed by pressors as indicated.

Patients with Mojave rattlesnake envenomation may present with predominantly systemic and laboratory abnormalities, with only mild local and no hematological effects.

Administer antivenom for signs of envenomation progression or imminent risk of an acute complication of envenomation (see Complications).

Crotalidae Fab polyvalent immune FAB, ovine (CroFab) is a safe option and it is indicated even if the envenomation is minimal mild. [18]  An equine Crotalidae immune FAB (Anavip) was approved in the United States in 2015. An antivenin should be given as a preventative measure if there are any signs of envenomation at all. Do not wait for it to get worse—permanent injury could result. [19]

Grading envenomations is a dynamic process; administer additional antivenom as indicated by a worsening clinical course. When considering the use of antivenom, weigh the risk of adverse reaction to antivenom against the benefits of reducing venom toxicity.

Nonenvenomation, ie, dry bite (probably occurs in < 10% of rattlesnake bites), is characterized by the following:

  • Local effects - Puncture wounds only

  • Systemic effects - None

  • Coagulation abnormalities - No laboratory evidence of coagulation abnormalities and no clinical evidence of abnormal bleeding or clotting

Minimal or mild envenomation is characterized by the following:

  • Local effects - Swelling, pain, tenderness, and/or ecchymosis confined to the immediate bite area

  • Systemic effects - None

  • Coagulation abnormalities - No laboratory evidence of coagulation abnormalities and no clinical evidence of abnormal bleeding or clotting

Moderate envenomation is characterized by the following:

  • Local effects - Swelling, pain, tenderness, and/or ecchymosis extending beyond the immediate bite area but involving less than the entire part

  • Systemic effects - Present but not life threatening; may include nausea, vomiting, oral paresthesias or unusual tastes, fasciculations (myokymia), mild hypotension (systolic blood pressure < 90 mm Hg), mild tachycardia (heart rate < 150 bpm), and tachypnea

  • Coagulation abnormalities - Laboratory evidence of coagulation abnormalities may be present, but no clinical evidence of abnormal bleeding or clotting exists; rattlesnake venom–induced coagulopathies commonly include thrombocytopenia, decreased fibrinogen, and/or elevated PT

Severe envenomation is characterized by the following:

  • Local effects - Swelling, pain, tenderness, and/or ecchymosis extending beyond the entire extremity or threatening the airway

  • Systemic effects - May include severe hypotension or shock, severe tachycardia or tachypnea, respiratory insufficiency, and/or severe altered mental status

  • Coagulation abnormalities - Markedly abnormal with serious bleeding or severe threat of bleeding

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Further Care

Discharge instructions

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.

Admit

Strongly consider admission for all Mojave rattlesnake envenomations. Because patients with severe Mojave 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 Mojave rattlesnake envenomations is probably prudent and cost effective.

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

Transfer

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.

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Consultations

The American Association of Poison Control Centers may assist in the management of envenomations. For assistance in treating snakebitten patients with crotaline Fab antivenom (CroFab), contact the CroFab hotline at 87-SERPDRUG (877-377-3784).

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Complications

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. [20]

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 antivenom treatment.

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Prevention

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.

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