Treating and Preventing Venomous Snake Bites : Part 2

by US Department of Health and Human Services

(Page 2 of 2)

"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," according to Don Tankersley, former deputy director of the 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 horse-derived 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 through exposure to horse dander, and be unaware that they are sensitive. Others may be sensitive without any known or remembered contact with horses. So hospitals also perform a skin test that may quickly show any sensitivity. However, the test also can give a false-positive or false-negative skin reaction. Some hypersensitive patients may even have severe reactions to the small amount of antivenin used in the skin test. Hospitals usually treat patients with serious allergic reactions by administering epinephrine. Some victims with positive skin tests can be desensitized by gradually administering small amounts of antivenin.

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 Hall. "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 numbers 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.

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, although 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 tissue 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 reported in the February 2002 issue of the Journal of Evaluation in Clinical Practice indicate that a venom-derived product called ancrod could provide significant benefits in treating stroke. Earlier proposals using snake venom to treat neuromuscular disorders such as multiple sclerosis never reached the clinical trial stage.

How NOT to Treat a Snakebite

Though US 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.

About the Author

The Department of Health & Human Services is the United States government's principal agency for protecting the health of all Americans and providing essential human services, especially for those who are least able to help themselves. The department includes more than 300 programs, covering a wide spectrum of activities.