Rattlesnake Envenomation Treatment & Management

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

Give general support of airway, breathing and circulation per advanced cardiac life support (ACLS) protocol with oxygen, monitors, 2 large bore intravenous lines, and fluid challenge. 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. Use a pen to mark and time the border of advancing edema often enough to gauge progression.

In some studies, no benefit was demonstrated when a negative pressure venom extraction device (eg, The Extractor from Sawyer Products) was evaluated; additional injury can result. ^{[22, 23]} Incision across fang marks is not recommended. Mouth suction is contraindicated. See the image below.

Lymphatic constriction bands and pressure immobilization techniques may inhibit the spread of venom, but whether they improve outcome is not clear. ^{[24, 25]} Limiting venom spread actually may be deleterious for pit viper envenomation if it increases local necrosis or compartment pressure. Tourniquets are not recommended.

Maintain the extremity in a neutral position.

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

Attempts to capture or kill the snake cannot be recommended because of the risk of additional injury. If uncertainty exists about whether a particular snake is venomous, consider taking photographs of the snake from a safe distance of at least 6 feet away using a digital camera.

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

Administer antivenom for signs of envenomation progression or imminent risk of an acute complication of envenomation (see Complications). Crotalidae polyvalent immune FAB ovine (CroFab) is a safe option ^{[26, 27]} and it is indicated even if the envenomation is minimal or mild. ^{[28, 29]} An equine Crotalidae immune FAB antivenin was approved in the United States in 2015. An antivenin should be given as a preventative measure if any signs of envenomation exist. Do not wait for the envenomation to get worse—permanent injury could result.

It is emphasized that grading envenomations is a dynamic process and additional antivenom should be given as indicated by a worsening clinical course. ^[30] When considering the use of antivenom, the risk of adverse reaction to antivenom must be weighed against the benefits of reducing venom toxicity. ^[31] Alternatives (eg, a different type of antivenom, if available) should be considered as well.

It should be noted that a retrospective review of 21 cases of male patients with C horridus (timber rattlesnake) envenomation, patient age 19-71, found severe thrombocytopenia despite antivenom administration. While there were no deaths and no red blood cell transfusions required among this patient group, the mean time to platelet count recovery was 10 days after envenomation. ^[32]  

Nonenvenomation, ie, dry bite (probably occurs in < 10% of rattlesnake bites, although estimates as high as 50% exist), 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

Discharge instructions

Return immediately if swelling worsens or pain becomes severe.

Return immediately if any abnormal bleeding or bruising, petechiae, 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). ^[33]

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. If bitten on the foot or leg, crutches and crutch training should be provided. Elevate and mobilize affected extremity as tolerated.

Next day wound check should be performed at the physician's discretion on a case-by-case basis. The patient should return to the ED or follow up every 3 days for 2 weeks with repeat CBC, PT/INR, and fibrinogen. Laboratory results may need to be rechecked more or less frequently or for a longer or shorter duration on a case-by-case basis.

Further inpatient care

All patients with rattlesnake envenomation should be admitted to the hospital and remain there while undergoing treatment with antivenom. Close observation and frequent measurements of swelling (every 1-2 h) for approximately 24 hours after initial control is recommended.

Patients who are believed to have a dry bite in which no venom effects develop should be observed for at least 8 hours. A close follow-up and/or recheck examination is recommended.

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. ^[34]

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, the patient 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.

The American Association of Poison Control Centers may assist in the management of envenomations.

For assistance regarding use of CroFab for a patient bitten by a snake, contact the CroFab hotline at 1-87-SERPDRUG (1-877-377-3784).

Consider consulting a surgeon (eg, general, orthopedic, hand) if compartment syndrome is suspected.

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 in indigenous areas.

Keep the garage door closed to prevent rattlesnakes from seeking shelter in the garage.

Many cases of envenomation involve alcohol. Do not use alcohol and place oneself in an environment that may be shared with rattlesnakes or play with snakes while intoxicated.