Snakebite in EMS: Pit Vipers and Coral Snake Bites

The United States has two families of venomous snakes, and they hurt people in different ways. Pit vipers, which include rattlesnakes, copperheads and cottonmouths, cause most venomous bites, and their venom mainly destroys tissue around the bite and interferes with blood clotting. Coral snakes cause far fewer bites, and their venom attacks the nerves, sometimes many hours after a bite that looked harmless. Field care for both is mostly about what to do quickly and what not to do at all, and the definitive treatment is in a hospital.

The two families

Pit viper envenomation

A pit viper bite that injects venom usually announces itself. Pain begins at the bite, and swelling spreads up the limb over the following hours. Bruising, discoloration and blood-filled blisters can follow. The venom can also cause a coagulopathy: platelets and clotting factors fall, and the patient may bleed from the gums, from the bite or from old wounds, or bleed internally.

• Systemic signs can include nausea, vomiting, sweating, weakness, a metallic or rubbery taste, tingling around the mouth, muscle twitching and low blood pressure.
• Some rattlesnakes, the Mojave rattlesnake being the best-known example, can also cause neurotoxic effects with less local swelling than you might expect.
• Not every bite injects venom. A dry bite causes no envenomation, but you cannot tell one in the field, and a bite that looks minor at first can progress.

Coral snake envenomation

Coral snake venom is neurotoxic. The bite itself may show little more than small puncture marks, with mild pain and little or no swelling, so a coral snake bite can look like nothing at all. When symptoms come, they can include drooping eyelids, double vision, slurred speech, difficulty swallowing, drooling, numbness, weakness and, at worst, failure of the muscles of breathing.

Why you should not rely on identifying the snake

Many people learn a rhyme about the order of the colored bands, built on whether the red bands touch the yellow ones, as a way to tell a coral snake from a harmless look-alike. It is widely quoted, and it is not a field decision tool.

• Color patterns vary within species, and individual snakes can be unusual.
• Several harmless snakes mimic coral snakes, and the difference is easy to misjudge in poor light or a moment of panic.
• The rhyme describes some North American species only. It does not hold for coral snakes in other parts of the world, which matters with exotic and captive snakes.
• Pit viper features such as the head shape, the pupils and the heat-sensing pits are equally unreliable at a distance, and checking them up close is how people get bitten.
• Getting close enough to identify a snake, photograph it or kill it puts the crew and bystanders at risk.

Treat the patient, not the snake. A description, where the snake was, and a photograph taken from a safe distance by somebody who was already there can help the hospital. None of them is worth a second bite, and the patient's signs and course matter more than the identification.

Field care

1. Scene safety first. Move the patient and everybody else away from the snake. Do not try to catch, kill or move it.
2. Never handle the snake, including a dead one. A dead snake, and even a severed head, can still bite by reflex. Do not transport a snake in the ambulance.
3. Keep the patient calm and as still as possible. Walking and exertion are best avoided.
4. Remove rings, watches, bracelets, shoes and tight clothing from the bitten limb before swelling makes it impossible.
5. Immobilize the limb with a splint as you would a fracture, and keep it at about heart level, or positioned as your protocol directs.
6. Mark the leading edge of swelling and tenderness on the skin with a pen and write the time beside it. Repeat at intervals. The progression is one of the things the hospital uses to judge severity.
7. Assess and support the airway, breathing and circulation. Watch for signs of bleeding, shock and, after a coral snake bite, any neurologic change.
8. Note the time of the bite, what the snake looked like if known, what first aid was done before you arrived, and the patient's medical history and medications, especially anything that affects clotting.
9. Transport to definitive care. Antivenom is the treatment for significant envenomation, and not every hospital stocks it. Your protocol and medical direction decide the destination, and an early call to the receiving facility helps it prepare.

Pain management and any other medication follow your protocol. Some guidance advises avoiding medications that affect platelets or clotting after a pit viper bite, because of the coagulopathy. The national Poison Help line, 1-800-222-1222, reaches the regional poison center, which receiving hospitals commonly consult on snakebite.

Hand over the time of the bite and the swelling progression clearly

What not to do

Folk and outdated first aid for snakebite does harm. The 2011 unified treatment algorithm for pit viper bites in the United States, the CDC's workplace safety institute (NIOSH) guidance on venomous snakes and the Wilderness Medical Society's guidelines all advise against the following.

• No tourniquet and no constricting band. Trapping venom in a limb concentrates the tissue damage and can cost the limb. If a bystander has already applied one, whether and how it comes off is a decision for your protocol and medical direction, and the receiving facility needs to know it was there.
• No cutting. Incising the bite adds a wound, bleeding and infection, and removes no meaningful venom.
• No suction, by mouth or with a commercial extractor device. It does not remove meaningful venom and can worsen local injury.
• No ice or cold packs. Cold worsens tissue injury.
• No electric shock. It has no benefit and causes burns.
• No alcohol, for the patient to drink or applied to the wound.
• Do not wait to see whether symptoms develop before transporting, and do not delay transport for any of the above.

Pressure immobilization

Pressure immobilization, wrapping the whole limb with a firm bandage and splinting it, is used for some elapid bites in other parts of the world. In North America it is generally not recommended for pit viper bites, because keeping the venom in the limb may worsen local tissue injury, and its role after a coral snake bite is debated. Whether you use it is your protocol's decision.

Antivenom

Antivenom exists for both pit viper and coral snake envenomation in the United States, and it is the definitive treatment for a significant envenomation. Whether a patient receives it, which product and how much are hospital decisions, made by the treating physician usually with the poison center or a toxicologist, based on the patient's signs, the progression of swelling and laboratory tests. The field contribution is getting the patient there with a clear record of the time of the bite and how the signs have changed since.

Track mental status over a long transport

The short version

• Pit vipers (rattlesnakes, copperheads, cottonmouths) cause local tissue injury and coagulopathy. Coral snakes cause neurotoxicity.
• A coral snake bite with no early symptoms is not reassurance. Symptoms can be delayed for many hours and can end in respiratory failure.
• Do not rely on the color-band rhyme or any other field identification. Treat the patient, not the snake.
• Never handle the snake, even a dead one.
• Remove rings and tight items early, immobilize the limb, keep it at about heart level or as protocol directs, and mark the swelling with the time.
• No tourniquet, no cutting, no suction, no ice, no electric shock, no alcohol.
• Pressure immobilization is debated in North America. Your protocol decides.
• Antivenom exists for both families and is a hospital decision. Get the patient to definitive care.