The three major families of venomous snakes are:
- Elapidae (cobra, king cobra, krait, and coral snake): These snakes have heads that are of about the same width as their necks, round pupils and short, fixed fangs. They cannot bite through clothes and usually deliver only a sublethal dose of venom.
- Viperidae (vipers): Triangular wide head, elliptical pupils, long needle like mobile fangs.
- Crotalinae (pit vipers) like Rattlesnakes have a “pit” organ on the head to detect their warm-blooded prey
- Viper bites mainly affect the vascular system. Rapidly swelling, necrosis, dry gangrene. Systemic absorption is slow; via lymphatics. Hemorrhage and increased capillary permeability leads to shock and pulmonary edema. Kidney failure is common in the sickest.
- Hydrophidae (sea snake): Coastal. Small head and a flattened tail. They seldom bite.
Snakebite severity can be gauged by evaluating the following parameters in the field:
- Pulmonary – degree of shortness of breath
- Cardiovascular – elevation in heart rate, decrease in blood pressure
- Gut – abdominal pain, nausea, vomiting and diarrhea
- Heme – bleeding more easily than normal (i.e. oozing from the bite site), degree of local and systemic bleeding and bruising
- Central Nervous System – apprehension, difficulty breathing, confusion, coma
- Wound – amount of swelling and/or bleeding/bruising at or near the bite site
Estimated yearly number of Snake Bite Envenomations
In North America, the need for preformed antibody to snake venom is determined by the severity of the envenomation. About 25% of pit viper bites are “dry” without significant envenomation. Mild bites -those with no systemic symptoms, no spread of bruising/swelling beyond the bite site- can be observed. However, because envenomation may progress over time, re-evaluation is critical.
Delayed extraction of the bite victim may allow envenomation to progress in the field.
Plan of Action for Suspected Venomous Snakebite
In general, the best plan of action for a suspected venomous snakebite in the field is immobilization and evacuation. Get the victim in proximity to anti-venom, surgical capabilities and life support.
Identifying the snake may be of benefit – photos are ideal. Avoid the snake to avoid a second victim. Leave the area.
Tourniquets have had limited to no success. Compression wraps, as recommended for Australian snakebites, may be of use in that situation. In the US there is no proven benefit.
Prevent excessive blood flow: keep the person still and as flat as is reasonable.
Reassure: the vast majority of snakebites are non-fatal. No alcohol consumption, which is a vasodilator.
Mark the area of the bite and sequentially mark and time the spread of bleeding and/or swelling.
Remove potentially constricting items from the affected area (usually a limb)
Periodically reexamine – specifically for the parameters mentioned above.
Do not attempt wound care/incision/suction or indeed anything other than evacuation.
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Syed Moied Ahmed, et al. Emergency treatment of a snake bite: Pearls from literature. J Emerg Trauma Shock. 2008 Jul-Dec; 1(2): 97–105
AWLS: Introduction to Wilderness Medicine. (2010). Richard Ingebretsen, ed.