Wilderness and Rescue Medicine 8th Edition

Wilderness and Rescue Medicine 180

Antivenom can be either monovalent (effective against the toxin of only one species) or polyvalent (covering several species). In North America, pit viper antivenom is the same for all the members of that family of snakes. It is not necessary to know the difference between a rattlesnake, copperhead, or cottonmouth. The presence of fang marks is enough. Specific antivenom may be used for spe- cies in other parts of the world. Splinting the bitten extremity may help reduce pain and tissue damage, but it is an unproven treatment and should not delay evacuation. If ALS is easily available, IV hydration with isotonic saline should be initiated. Do not apply ice or arte- rial or venous tourniquets. Do not apply suction or incise the wound. Suction devices, even the more modern versions, have been shown to be ineffective and possibly harmful. In anticipation of swelling, remove constricting items such as rings, bracelets, and tight clothing to prevent ischemia. Closely monitor any splint. If you can, mark the progression of swelling up the extremity. Make a line and write the time on the skin with a pen. This information will be helpful in the decision to use antivenom, and in deciding how much will be necessary. Treatment: • Emergency evacuation to antivenom • Anticipate swelling • Splint extremity if it will not delay evacuation • NO tourniquets, ice, suction devices • IV hydration if available • BLS as needed 13 * The amount of venom injected varies with the size and condition of the snake. Symptoms can range from mild to severe. A small number of strikes are dry bites in which no venom is injected at all. This is worth remembering if emergency evacuation will be a high-risk operation. In these situations, evacuation to medical care can be less emergent if no symptoms (e.g., pain, bleeding, or swelling) develop within 3 hours. General Principles © 2018 WMA Pit Viper Envenomation

Snakebite Pit Vipers

The pit vipers (family Viperidae) in North America include rattlesnakes, copperheads, and cottonmouths. Viper venom is primarily a tissue toxin that causes local swelling and tissue dam- age. Systemic effects include problems with blood coagulation and shock caused by leakage of fluid from the circulatory system into the interstitial space (between the cells in body tissues). Some pit viper venom, notably the Mojave rattlesnake, also contains a systemic neurotoxin. The degree of systemic effect depends on the dose injected and the size and general health of the patient. Fatalities are extremely rare in North America but are more common in other parts of the world.

Pit Vipers ( Viperidae ) Rattlesnake/Copperhead/Cottonmouth: • Triangular head • Heat sensing “pits” • Inject venom through fangs • Mostly tissue toxic

General Principles

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© 2018 WMA

Treatment of Pit Viper Envenomation The ideal treatment for a poisonous snakebite is antivenom. Evacuation to medical care should be started without delay by the fastest means avail- able. Walking your patient out may be the quick- est way to go, and this is fine unless prevented by severe symptoms. If possible, alert the receiving facility to expect your patient so antivenom can be acquired and prepared. The use of antivenom is restricted to the hospital because it can cause life-threatening allergic reac- tions in rare cases. It is also extremely expensive and needs to be prepared carefully prior to use. It is most effective in the first 4 hours but can be given a day or more following the bite and still have some benefit.