By Steven Shotz
With the arrival of warm weather, snakes end their hibernation and become more active. Virtually all bites in temperate climates occur between April and October. Poisonous snakes are found throughout the U.S., except in Hawaii, Alaska, and Maine.
Of 115 species of snake, only 19 are poisonous. In the U.S., six to eight thousand of the roughly 45,000 snakebites annually are from poisonous species. Although deaths from snakebite are very rare (about 12-15 per year, or less than 1%), the resultant tissue death (necrosis) puts victims in danger of losing fingers or toes. Pit vipers (rattlesnakes, cottonmouths, and copperheads - in order of decreasing toxicity) account for about 99% of poisonous snake bites. Coral snakes, whose bite characteristics and venom are different from most pit vipers, account for about 1% of bites.
1) Recognizing Bites
Ideally, one can identify rattlesnake bites by two puncture wounds, but sometimes only one fang actually hits the target or the snake may bite several times. Rattlesnakes can open their jaws very wide and have a pair of large fangs that act like hypodermic needles. Coral snakes, on the other hand, have very small fangs and inject their venom by chewing. Therefore, they tend to bite small body parts. They may leave multiple marks or no visible marks. You cannot tell if a bite was from a poisonous snake by the marks left on the victim.
2) Who Gets Bitten?
The most likely bite victims are white males between the ages of 18-28 who try to handle the snake. Commonly, they have been drinking, which raises issues related to assessment and rescuer safety. While there have been reported cases of people bitten on the face while trying to kiss a snake, the most likely strike zones (95%) are on the arms, then legs, respectively. About one-fifth of pit viper bites contain no venom, so-called "dry bites." The venom is sterile and is unlikely to cause infection. Snakes are able to bite more than once and may inject venom several times.
3) Signs and Symptoms
Pit Vipers: The venom produced by these snakes contains enzymes that destroy bodily tissues and cause bleeding (cytotoxic and hemotoxic). This mechanism is designed to kill prey and start digestion. The amount and toxicity of the venom varies greatly with the type, size, and age of the snake, and the effect on the victim depends on the site of the wound, the victim's size, age and health. Some snakes carry a small amount of highly toxic venom and others carry much larger amounts of less powerful venom. Bites from pit vipers result in severe damage to the tissues near the bite, and the destruction progresses proximally (upstream toward the heart). Within minutes there is pain and severe swelling locally (at the wound site). Within hours, the victim will display severe bruising, blood filled blisters, and significant tissue death.
Because the poison spreads through the lymph system, tender lymph nodes are a reliable sign that the victim was injected with venom. As tissue continues to be destroyed, the poison moves into the circulatory system, spreading throughout the body and demonstrating systemic (generalized) signs/symptoms. If the snake bite hit a vein, the poison will spread rapidly throughout the body and may not initially show the severe local tissue damage indicated above. Systemic signs/symptoms may include sweating, weakness, nausea and vomiting, headache, diarrhea, rapid heart rate, low blood pressure, and a metallic taste. Systemic signs indicate a more serious problem.
Pit viper envenomation (injection of poison) can also result in excessive blood clotting or bleeding and damage to kidneys as muscle protein leaks out of cells. The effects of envenomation can follow a start-stop-start pattern and may not reveal the full picture for several days. If no signs/symptoms show up within 12 hours the bite did not contain venom.
Coral Snakes: Their venom is different from most rattlesnakes (except the Mojave rattlesnake). Rather than being cytotoxic/hemotoxic, it is neurotoxic (poisonous to nerves) and has different effects. It does not cause significant local tissue damage, but does affect bodily functions regulated by the nervous system. Look for paralysis, weakness or poor muscle coordination, droopy eyelids, drooling, difficulty swallowing, double vision, sweating, slowed reflexes, difficulty breathing. The coral snake's venom may take 12 hours to develop these neurological signs/symptoms, which may then appear suddenly.
Victims may need to be intubated and provided with mechanical respiration in order to continue breathing. Fortunately, only about 40% of coral snake bites involve actual envenomation.
4) Assessing Snake Bites
As always, scene safety is the first priority. Unless you are sure there are no more snakes nearby, this is one time when you will move the victim immediately to a safe area. Most snakes remain within 20 feet of the incident. Do not try to kill the snake. If someone has already done so, be aware that a recently killed snake and even its severed head can still envenomate. Never transport the head; bury or dispose of it to ensure that people and animals will not contact it. A segment of snake body may safely be brought in for identification or take a digital picture. Establish the time the victim was bitten.
Be aware that if the patient is intoxicated he may be uncooperative, hostile or inaccurate in his report, or the symptoms of intoxication may blur the signs/symptoms of the bite. Airway, breathing, and circulation (ABC's) are always the starting point. Airway and breathing may be compromised because of allergic reaction (anaphylaxis), neurotoxicity, or direct bite to the neck or face (which should be considered an immediate threat due to imminent swelling). Open bleeding from snake bites is usually not significant. Get your SAMPLE history (signs/symptoms, allergies, medicine/drug use, pertinent medical history, last oral intake, and events leading up to the bite) to pass on to paramedics. Some authorities recommend marking the edge of the swelling most proximal (closest to the victim's torso) with a pen and noting the time to keep track of its progression. The greater the swelling, the more pain you should expect your patient to feel. Check for shock.
5) Treating Bites
There is not much in the way of effective first aid intervention for poisonous snake bites. Patients need antivenin. After treating any problems with the ABC's, your priority is rapid extrication from the scene and transport to a hospital that carries antivenin. Most patients do well if medically treated within several hours. All victims should be examined at a hospital.
- Try to calm the patient
- Immediately remove any jewelry or clothing that may constrict circulation.
- Without delaying transport, clean and dress the wound with sterile gauze (wear gloves)
- If the bite is on an extremity, splint the arm or leg in a straight, fully extended position; do not bend the limb at the joint because this will increase tissue damage. Elevate the immobilized limb above the heart
- Minimize activity of the patient when possible to slow the spread of the venom
- Treat for shock if present
- Take frequent vital signs
- Notify paramedics immediately
There are a number of myths about treatment that have now been shown to be ineffective and/or to worsen the patient's condition.
10 Things You Should NOT Do For a Bite Victim
- Apply a tourniquet
- Cut or slit the wound between or at the puncture marks
- Use you mouth to create suction of the wound
- Apply an Australian pressure wrap
- Use suction devices (which have not been shown to help and can waste time)
- Apply electric shock from car batteries or other sources
- Aggressively cool or heat the wound
- Give the patient anything to eat or drink
- Splint a bitten extremity in a bent position
- Try to catch or kill the snake
- Learn what varieties of poisonous snakes live in your area and how to recognize them.
- Learn which hospitals carry antivenin.
- Be alert in snake county to avoid sneaking up on snakes, which have poor eyesight and are easily startled. Check in between rocks and logs and places where snakes hide before sitting or placing a hand or foot there.
Steve Shotz (sjshotz [at] sbcglobal [dot] net) is an Emergency Medical Technician and an Outdoor Emergency Care instructor for the National Ski Patrol. He welcomes your questions on first aid practices.