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[at-l] Treating and Preventing Venomous Bites

For Goodness Snakes!
Treating and Preventing Venomous Bites
by John Henkel
They fascinate. They repel.

Some pose a danger. Others are harmless.

And whether they are seen as slimy creatures or colorful curiosities, 
snakes play important environmental roles in the fragile ecosystems of 
the nation's wildlife areas.

People who frequent these wilderness spots, as well as those who camp, 
hike, picnic, or live in snake-inhabited areas, should be aware of 
potential dangers posed by venomous snakes. Every state but Maine, 
Alaska and Hawaii is home to at least one of 20 domestic poisonous snake 
species. A bite from one of these, in which the snake may inject varying 
degrees of toxic venom, should always be considered a medical emergency, 
says the American Red Cross.

About 8,000 people a year receive venomous bites in the United States; 
nine to 15 victims die. Some experts say that because victims can't 
always positively identify a snake, they should seek prompt care for any 
bite, though they may think the snake is nonpoisonous. Even a bite from 
a so-called "harmless" snake can cause an infection or allergic reaction 
in some people.

Medical professionals sometimes disagree about the best way to manage 
poisonous snakebites. Some physicians hold off on immediate treatment, 
opting for observation of the patient to gauge a bite's seriousness. 
Procedures such as fasciotomy, a surgical treatment of tissue around the 
bite, have some supporters. But most often, doctors turn to the antidote 
to snake venom--antivenin--as a reliable treatment for serious 
snakebites. 

Antivenin is derived from antibodies created in a horse's blood serum 
when the animal is injected with snake venom. In humans, antivenin is 
administered either through the veins or injected into muscle and works 
by neutralizing snake venom that has entered the body. Because antivenin 
is obtained from horses, snakebite victims sensitive to horse products 
must be carefully managed. The danger is that they could develop an 
adverse reaction or even a potentially fatal allergic condition called 
anaphylactic shock. 

The Food and Drug Administration regulates antivenins as part of its 
oversight of biological products. The agency requires certain criteria 
to be met before these materials are sold, including standards for 
purification, packaging and potency. FDA also regulates antivenin 
labeling, ensuring that data on potential side effects and other 
pertinent information are available. The agency also periodically 
inspects antivenin production facilities to ensure compliance with 
regulations. 

Types of Poisonous Snakes

Two families of venomous snakes are native to the United States. The 
vast majority are pit vipers, of the family Crotalidae, which include 
rattlesnakes, copperheads and cottonmouths (water moccasins). Pit vipers 
get their common name from a small "pit" between the eye and nostril 
that allows the snake to sense prey at night. They deliver venom through 
two fangs the snake can retract at rest but can spring into biting 
position rapidly. About 99 percent of the venomous bites in this country 
are from pit vipers. Some--Mojave rattlesnakes or canebrake 
rattlesnakes, for example--carry a neurotoxic venom that can affect the 
brain or spinal cord. Copperheads, on the other hand, have a milder and 
less dangerous venom that sometimes may not require antivenin treatment.

The other family of domestic poisonous snakes is Elapidae, which 
includes two species of coral snakes found chiefly in the Southern 
states. Related to the much more dangerous Asian cobras and kraits, 
coral snakes have small mouths and short teeth, which give them a less 
efficient venom delivery than pit vipers. People bitten by coral snakes 
lack the characteristic fang marks of pit vipers, sometimes making the 
bite hard to detect. 

Though coral snakebites are rare in the United States--only about 25 a 
year by some estimates--the snake's neurotoxic venom can be dangerous. A 
1987 study in the Journal of the American Medical Association examined 
39 victims of coral snakebites. There were no deaths, but several 
victims experienced respiratory paralysis, one of the hazards of 
neurotoxic venom.

Some nonpoisonous snakes, such as the scarlet king snake, mimic the 
bright red, yellow and black coloration of the coral snake. This 
potential for confusion underscores the importance of seeking care for 
any snakebite (unless positive identification of a nonpoisonous snake 
can be made).

The bites of both pit vipers and coral snakes can be effectively treated 
with antivenin. But other factors, such as time elapsed since being 
bitten and care taken before arriving at the hospital, also are critical 
(see accompanying article). 

First Aid for Snakebites

Over the years, snakebite victims have been exposed to all kinds of 
slicing, freezing and squeezing as stopgap measures before receiving 
medical care. Some of these approaches, like cutting into a bite and 
attempting to suck out the venom, have largely fallen out of favor. 

"In the past five or 10 years, there's been a backing off in first aid 
from really invasive things like making incisions," says Arizona 
physician David Hardy, M.D., who studies snakebite epidemiology. "This 
is because we now know these things can do harm and we don't know if 
they really change the outcome."

Many health-care professionals embrace just a few basic first-aid 
techniques. According to the American Red Cross, these steps should be 
taken:

•Wash the bite with soap and water. •Immobilize the bitten area and keep 
it lower than the heart. •Get medical help.
"The main thing is to get to a hospital and don't delay," says Hardy. 
"Most bites don't occur in real isolated situations, so it is feasible 
to get prompt [medical care]." He describes cases in Arizona where 
people have caught rattlesnakes for sport and gotten bitten. "They 
waited until they couldn't stand the pain anymore and finally went to 
the hospital after the venom had been in there a few hours. But by then, 
they'd lost an opportunity for [effective treatment]," which increased 
the odds of long-term complications. Some medical professionals, along 
with the American Red Cross, cautiously recommend two other measures: 
•If a victim is unable to reach medical care within 30 minutes, a 
bandage, wrapped two to four inches above the bite, may help slow venom. 
The bandage should not cut off blood flow from a vein or artery. A good 
rule of thumb is to make the band loose enough that a finger can slip 
under it. •A suction device may be placed over the bite to help draw 
venom out of the wound without making cuts. Suction instruments often 
are included in commercial snakebite kits. 
Treatment Drawbacks

Antivenins have been in use for decades and are the only effective 
treatment for some bites. "Antivenins have a fairly good safety record," 
says Don Tankersley, deputy director of FDA's division of hematology. 
"There are sometimes reactions to them, even life-threatening reactions, 
but then you're treating a life-threatening situation. It's clearly a 
case of weighing the risks versus the benefits."

People previously treated with antivenin for snakebites probably will 
develop a lifelong sensitivity to horse products. To identify these and 
other sensitive patients, hospitals typically obtain a record of the 
victim's experience with snakebites or horse products. But some people 
with no history of such exposures may have become sensitive through 
contact with horses, or possibly exposure to horse dander, and not know 
they are sensitive. Others may be sensitive without any known or 
remembered contact with horses. So hospitals also perform a skin test 
that quickly shows any sensitivity. Some hypersensitive patients may 
even react severely to the small amount of antivenin used in the skin 
test. Hospitals have procedures for reviving patients with serious 
reactions. Some victims with positive skin tests can be desensitized by 
gradually administering small amounts of antivenin.

Newer kinds of antivenins derived from sheep are under study now and 
show some promise, according to FDA officials. But progress has been 
slow due to low demand and the small number of venomous bites a year. 

Certain venomous snakebites may be treated without using antivenin. This 
is usually a judgment call the doctor makes based on the snake's size 
and other factors, which normally involves close monitoring of patients 
in a medical facility. 

"In some areas, such as desert areas, most rattlesnakes are small and 
don't have as potent a venom," says Edward L. Hall, M.D., a Thomasville, 
Ga., trauma surgeon who treats snakebites. "You might get by with those 
patients in not using antivenin." But with other snakes, Hall says, 
antivenin can be a lifesaver. For example, the Eastern diamondback 
rattlesnake--found in large quantities in the region of Georgia where 
Hall practices medicine and in other Southern states from the Carolinas 
to Louisiana--can reach six feet in length and deliver a potent payload 
of venom. "It's an enormously dangerous bite that requires very 
aggressive treatment [with antivenin] or the patient will die," Hall 
says.

Treatment Dilemmas

Because not all snakebites, including those from the same species, are 
equally dangerous, doctors sometimes face a dilemma over whether or not 
to administer antivenin. Venomous snakes, even dangerous ones like the 
Eastern diamondback, don't always release venom when they bite. Other 
snakes may release too small an amount to pose a hazard.

Hall says his experience in Georgia bears this out. "Some 20 to 30 
percent of patients we see who have been bitten by a snake, who actually 
have fang marks, have not received any venom at all." He says one reason 
for this may be poor timing by the snake. "Pit vipers have a very 
sophisticated mechanism that allows them to deliver venom at the exact 
instant the teeth are sunk into the flesh. So it has to be precise 
timing. But what we often see is that the [snake's timing is off and] 
venom is squirted on the pants leg or released prematurely."

Another complicating factor is the diverse potency of venom. "Venom can 
vary within species and even within litter mates--brothers and sisters," 
says Arizona physician Hardy. For example, he says, a common pit viper 
in the Southwest, the Mojave rattlesnake, may carry a powerful 
neurotoxic venom in some areas and a less toxic one in others.

Hall's work in Georgia and Florida shows that factors such as genetic 
differences among snakes, their age, nutritional status, and the time of 
year also can affect venom potency. All these variables make it nearly 
impossible for doctors to characterize a "typical" venomous snakebite. 
That's why there exists what Hall calls "so much controversy" about 
snakebite treatment. 

The solution, Hall says, lies with the patient. "Truly the only way to 
look at snakebites is on an individual basis and on the patient's actual 
reaction to the venom." Basic signs like pain, swelling and bleeding, 
along with more complicated reactions such as ecchymosis (purple 
discoloration), necrosis (tissue dies and turns black), low blood 
pressure, and tingling of lips and tongue give medical professionals 
clues to the seriousness of bites and what treatment route they should 
take. 

Some experts emphasize that though antivenin can effectively reverse the 
effects of venom and save life and limb, there is no guarantee that it 
can reverse damage already done, such as necrosis. Some patients may 
later require skin grafts or other treatment. Arizona physician Hardy 
says the potential for limiting complications is one compelling reason 
to seek medical treatment as soon as possible after a snakebite. 

Avoiding Snakebites

Some bites, such as those inflicted when snakes are accidentally stepped 
on or encountered in wilderness settings, are nearly impossible to 
prevent. But experts say a few precautions can lower the risk of being 
bitten:
•Leave snakes alone. Many people are bitten because they try to kill a 
snake or get a closer look at it. •Stay out of tall grass unless you 
wear thick leather boots, and remain on hiking paths as much as 
possible. •Keep hands and feet out of areas you can't see. Don't pick up 
rocks or firewood unless you are out of a snake's striking distance. (A 
snake can strike half its length, Hardy says.) •Be cautious and alert 
when climbing rocks.
What do you do if you encounter a snake when hiking or picnicking? Says 
Hardy: "Just walk around the snake, giving it a little berth--six feet 
is plenty. But leave it alone and don't try to catch it."

Though poisonous snakes can be dangerous, snake venom may have a 
positive side. Clinical trials are presently under way to test the 
therapeutic value of a venom-derived product called ancrod in treating 
stroke. Earlier proposals, using sntrials are presently under way to 
test the therapeutic value of a venom-derived product called ancrod in 
treat

John Henkel is a staff writer for FDA Consumer.


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How NOT to Treat a Snakebite
Though U.S. medical professionals may not agree on every aspect of what 
to do for snakebite first aid, they are nearly unanimous in their views 
of what not to do. Among their recommendations:
•No ice or any other type of cooling on the bite. Research has shown 
this to be potentially harmful. •No tourniquets. This cuts blood flow 
completely and may result in loss of the affected limb. •No electric 
shock. This method is under study and has yet to be proven effective. It 
could harm the victim. •No incisions in the wound. Such measures have 
not been proven useful and may cause further injury. 
Arizona physician David Hardy, M.D., says part of the problem when 
someone is bitten is the element of surprise. "People often aren't 
trained in what to do, and they are in a panic situation." He adds that 
preparation--which includes knowing in advance how to get to the nearest 
hospital--could greatly reduce anxiety and lead to more effective care. 
--J.H.


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FDA Consumer magazine (November 1995)
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