Snake Bite in North America

In the event of a snake bite, do not panic. There are about 4,000 to 7,000 snake bites reported yearly in North America. Most are not serious, and there are on average less than four fatalities per year. Many adult venomous snakes deliver "dry bites" containing no venom, since they prefer to warn larger animals away without wasting the venom they need for their next meal. Most snakes are not venomous, though any snake bite can be bloody and painful. In this country, more people die from being struck by lighting than from snake bite. Injuries and fatalities caused by dogs, cats and horses vastly outnumber problems caused by snakes. Diseases trasmitted by rats and mice (which are the primary food of snakes) kill many more people than snakes.

Human attacks snake! The most common cause of snake bite (from 60% to over 80% in Florida) is attempting to kill or inappropriately handle a snake. The most common profile of a bite victim is a young intoxicated male. A defensive bite is more likely to be a "dry" bite, unless the snake has already been injured and is in pain. A snake that is in pain or harassed for an extended time is more likely to deliver a fully envenomating bite. A feeding response bite from a hungry snake that mistakes a part of your body for a small food animal is also likely to be a fully envenomating bite. Feeding response bites usually happen in captive situations where the snake is accustomed to being fed by its keeper. They are quite rare in the wild. Defensive bites are more likely to be dry, or lacking venom.

You can walk away from a snake. It won't chase after you, unless you are between the snake and its favorite hiding place, in which case it probably wants to go past you. Snake bites happen because the human approached or attacked the snake, not vice versa. Venomous snakes are surprisingly weak and fragile, with brittle bones and very little muscle power. They were not designed to survive picking fights with bigger animals. They will defend themselves if they have to, but they would much rather run and hide.

According to snake bite researcher Steve Grenard, catching and identifying the native snake that caused the bite is not as important as rapid transport to the hospital. Identifying the snake is only important in the case of exotic (non native) venomous snake bite. He also cautions that you should not attempt any folk remedies such as cutting, sucking, tight tourniquets, ice, electricity, etc. None of them are helpful and most are harmful, with the possible exception of pressure immobilization.

Pressure immobilization (PI) means applying a wide, firmly wrapped Ace bandage (or several of them) to the bitten limb in the same way you would wrap a sprain. This is not a tight arterial tourniquet and should not occlude blood flow. The wrapped limb is then splinted and kept below the heart. Clinical toxicologist Dr. Julian White suggests that PI can effectively delay the onset of systemic symptoms for many hours. PI is recommended for most elapid bites and some viper bites which are known to cause life threatening systemic symptoms such as respiratory paralysis, especially when transport to the hospital may be delayed and/or when local damage is not a concern. Some species are not known to cause localized necrosis, only systemic symptoms which can be effectively delayed with PI during transport to a medical care facility.

The Antivenom Index, a Joint Project between the American Association of Zoos and Aquariums and the American Association of Poison Control Centers, recommends that PI be used if you are more than 1 to 2 hours away from help such as out in the wilderness. Before trekking out of the wilderness it is probably the best thing you can do to delay symptoms. Grenard also adds that while trapping the venom locally may cause increased tissue damage, the area of such damage is apt to be smaller than if the venom were allowed to permeate the entire limb. He says it is a trade-off worth considering depending on circumstances. The use of PI on bites that are capable of causing localized damage remains controversial. The best tools to use on a snake bite are a car and a telephone.

Antivenom

"The only sure cure for rattlesnake bite is treatment with the appropriate antivenom, which must be administered by medical professionals with access to the right equipment."
- Steve Grenard in Natural History, July/August 2000

There are only three choices for antivenom in the United States. One of them (Wyeth Anticrotalidae Polyvalent) was not manufactured for some time due to problems meeting FDA standards, though it now appears to be back in production. Wyeth is an equine derived serum largely based on Eastern diamondback venom, and it may still be the most effective treatment for Eastern diamondback bite. This antivenom is known to have serious side effects including anaphylactic (allergic) shock and serum sickness. Batches were known to vary up to 300% in potency. Wyeth Micrurus is an equine derived coral snake monovalent antivenom that is manufactured in limited quantities and rarely used because coral snakes typically do not bite unless handled very carelessly or severely provoked.

CroFab is a new ovine (sheep derived) serum that covers all of the North American pit vipers (rattlesnakes, cottonmouths and copperheads) and is not thought to cause serum sickness or significant allergic reactions. CroFab was developed by ProTherics and is now distributed by Savage Laboratories. Some difficulties with recurrent coagulapathy have been observed with CroFab if sufficient doses are not given over a longer period of time.

Some less serious snake bites can be conservatively managed without antivenom. A strongly conservative approach made good historical sense when Wyeth was the only available antivenom for North American pit viper bite, because equine serum is known to cause serious side effects. With the development of affinity purified CroFab, such conservative measures should probably be re-assessed.

Bites by exotic venomous snakes require specialized antivenom that is manufactured in the snakes' country of origin. In exotic snake bite cases, it is crucial to identify the snake that caused the bite and locate a supply of the proper antivenom. Call the Florida Poison Control Center 1-800-222-1222 and the Florida Antivenin Bank at (305) 596-8576, and look in the victim's refrigerator for antivenom. If the victim is conscious, ask them to identify the snake that caused the bite. If the victim is not conscious, get a local snake expert on the scene immediately.

Fasciotomy and compartment syndrome

The "old school" method of treating snake bite involved physical surgery. Modern researchers have since discovered more effective ways to medically manage envenomations without invasive physical trauma, but because snake bite is such a rare occurrence, the average doctor will not be up to date in this field, and the average hospital will still be working from treatment protocols that do not take these recent changes into account. True compartment syndrome is considered rare in a properly managed envenomation where sufficient antivenom is administered - but the effects of envenomation may be difficult to distinguish from compartment syndrome, leading the doctor to perform an inappropriate fasciotomy.

North American hospitals have a consistently poor track record for medically mismanaging snakebites, so if your officers are at risk of snakebite it is a good idea to contact a clinical toxicologist ahead of time who has experience treating snakebite. The victim or the family of the victim must make it clear to the attending physician that they want treatment decisions to be made in consultation with a clinical toxicologist who has experience successfully treating envenomations. Call the Poison Control Center (800) 282-3171 to find a toxicologist near you - before you need one.

Important: Most emergency room physicians have never treated or studied snake bite, and most of them will not be able to make the best decisions for your care unless they are willing to follow the instructions of an expert in this field. In some cases you may have to take legal steps to force a doctor to obtain and follow this advice. The average emergency room physician lacks the experience and special knowledge necessary to competently treat your snake bite. There have been many recent changes and advances in the medical management of snakebite that have not made it into the formal protocol in many hospitals.

Summary:
Don't panic. Snake bites are rarely fatal.
Most snake bites are caused when a human attacks a snake on purpose.
There is little need to identify the snake in a native bite case.
The only cure for a serious envenomation is antivenom.
In an exotic snake bite, it is critical to identify the snake.
Most doctors are not prepared to deal with snake bite, so you should be.

   Index