SNAKE BITES

In this column we will look at snake bites focusing on field management. Approximately 8000 people are bitten by poisonous snakes each year and 10-20 people die from envenomation. In the United States there are 2 different groups of venomous snakes. Pit vipers include rattlesnakes, copperheads, and water moccasins. These snakes account for the vast majority of bites in this country. Coral snakes are the other class of venomous snakes but account for far fewer bites. In fact, less than 1 % of snake bites are caused by coral snakes which is good news because these bites are highly toxic and often rapidly fatal.

	Rattlesnake
	Coral Snake
	Water Moccasin
	Copperhead

 

Poisonous snakes are found in every state except Maine, Alaska and Hawaii but the total number of snakes and snake bites increases as one heads south into warmer climates. Snakes are cold blooded and their activity level is strongly controlled by temperature. Warmer temperatures increase your risk of contact with snakes. This explains why even though Colorado has a lot of rattlesnakes they are not much of a problem on a late September elk hunt. On the other hand, you should carefully inspect your antelope pit blind in August before climbing in.

A common theme in wilderness medicine is prevention. In no other aspect of wilderness medicine is prevention more important than with snake bite. Envenomation can be fatal and typical first aid measures are not that helpful. A bite in a wilderness setting with a long transport time to a hospital can be a disaster. Luckily, simple measures such as high top leather boots, looking before sitting or placing your hands anywhere, and giving visible snakes a wide berth will prevent almost all bites. Greater than 90% of snake bites occur on the legs and snakes can not bite through heavy leather. Strong leather boots are a sensible precaution when hunting in snake country. Most bites to the hands and arms occur when someone is handling the snake. This is easily avoided! A snake skin backing for your self bow is best acquired by professionals.

Identification of snakes can be helpful in the field and there are some basic rules that help determine if the snake is poisonous. It should be noted that avoidance of all snakes is the safest policy and more than one person has been bitten after trying to get a closer look. Usually you will be trying to differentiate between pit vipers which are poisonous and non venomous snakes. Coral snakes have a red/yellow/black coloration that should aid in identification. Pit vipers have triangular heads, oval shaped pupils, visible fangs and usually have rattles. They also have facial pits as their name indicates. Nonvenomous snakes have more rounded heads, round pupils, no fangs and do not have rattles. Facial pits are absent. If someone is bitten you should not attempt to kill the snake as it just wastes time and increases the risk of a second bite. A word of caution; snakes are capable of envenomating you even after they are dead. Handling the head or mouth of a dead rattlesnake is very dangerous and is a good way to get bitten. A simple description of the snake using the characteristics outlined above will be invaluable to the physician. At the hospital a serious bite will usually be obvious and bringing the dead snake will not help treatment but will make the nurses avoid you!

Snake venom is a mixture of proteins which can have a variety of effects on its victim. Most rattlesnake bites are composed of toxins which destroy the clotting mechanisms in your blood and cause your blood vessels to become leaky. Essentially you bleed to death internally. Your body can also develop a severe allergic type reaction to the venom which further lowers your blood pressure. Coral snake venom is neurotoxic meaning it leads to rapid paralysis. You will quickly stop breathing and suffocate.

Early transport to an Emergency Department is the most important aspect of field management. For a serious envenomation the only effective treatment is antivenin which is only available in hospitals. Any measure which delays transport should be avoided. This includes finding or killing the snake, or other snake bite measures which are commonly recommended.

At this time we should probably talk about other treatments which you have all heard about. These methods are typically used in an effort to limit the amount of venom which enters your body or neutralize it. The most common and potentially dangerous method is the "cut and suck" technique. Proponents of this method recommend that you immediately cut an X at the bite site and use some form of suction to attempt to remove some of the venom. No well controlled study has ever shown this to be effective and it markedly increases the risk of a wound infection. It is also possible to severe nerves or blood vessels which can only make a bad situation worse. Applying suction without cutting is OK but does not replace early hospital transport. A suction device such as the "Extractor" is probably a reasonable thing to have in your first aid kit in snake country and may recover a small amount of venom after a bite. Basically this is a plunger type device that is applied over the bite site and by retracting the plunger strong negative pressure is applied to the site in an attempt to remove some of the venom. These are available in most camping stores and medical supply stores. Another commonly recommended therapy is to use a "stun gun" at the bite site. The theory is that a stun gun delivers a strong electric shock to it's victim. In a snake bite you are hoping that the electrical current will destroy the protein toxins in the venom, making the bite harmless. The problem is that the venom quickly spreads from the bite site and there is no evidence to suggest that this therapy has any useful effect and is very painful. Cold, heat and topical treatments will have no effect on a serious bite.

What can be recommend is immobilization of the bitten extremity at the level of the heart and possibly the use of constriction bands above the site of the bite. These bands are applied tight enough to prevent the movement of the venom throughout your body but should not function as a tourniquet. You should still be able to feel the victims pulse below to the band. Once the band is applied it should not be removed until the patient is at the hospital as a large amount of venom could suddenly be released into the victims body causing sudden shock. Remember, these bands are not intended to restrict blood flow and having them too tight is worse than not applying them at all.

Once you arrive at the hospital the doctors will quickly assess the severity of the bite and treat appropriately. Bites vary in their severity depending on the size and health of the victim and the amount of venom injected. Different species of pit vipers vary in the toxicity of their venom. For example, water moccasins often cause localized reactions at the bite site but it is unusual for them to cause life threatening reactions. Surprisingly about 25% of bites are dry meaning no venom is injected. Another 20% are severe requiring aggressive antivenin therapy. The remainder fall in the middle and are treated based on clinical judgment. Early symptoms such as pain, swelling, bleeding at the site of the bite, and localized skin discoloration help determine the severity of the bite. It should be stressed that you should not waste time in the woods waiting to see if you develop symptoms. Get to a hospital as quickly as possible so that if antivenin is deemed necessary you can receive it as early as possible.

Snake bites are a topic that many hunters and outdoorspeople are concerned about. Fortunately bites are relatively rare and can often be prevented. In the event of a bite, immobilization and early hospital transport will maximize survival and limit disability. An "Extractor" and constriction bands are a reasonable addition to a first aid kit in snake country but do not replace sound judgment.

Photos are courtesy of Brazos River Rattlesnake Snake Ranch (www.wfnet/~snake/brrrhq) and MD challenger.

Next month: Heat exhaustion