Rattlesnake Bite — Tourniquet or Not?
May 1, 1999
Rattlesnake Bite—Tourniquet or Not?
Abstract & Commentary
Synopsis: Tourniquets are not beneficial and should not be used in the initial management of rattlesnake bites.
Source: Amaral CF, et al. Tourniquet ineffectiveness to reduce the severity of envenoming after Crotalus durissus snake bite in Belo Horizonte, Minas Gerais, Brazil. Toxicon 1998;36:805-806.
The effect of tourniquet placement on the clinical outcome after a rattlesnake bite on the extremities was assessed by Amaral and associates in 97 patients who had been bitten by the neotropical rattlesnake, Crotalus durissus, whose venom has both neurotoxic as well as local tissue effects. In 45 of these patients, a proximal tourniquet was applied as part of acute management; 52 patients did not have tourniquets. Both groups were similar with regard to age, sex, time since bite, and early neurologic findings. On follow-up, there were no differences in the rate of coagulopathy, rhabdomyolysis, and fatality between the tourniquet and nontourniquet groups.
Comment by Robert Hoffman, MD
Despite common perception, fatalities following bites with envenomation by North American pit vipers (rattlesnakes, cottonmouths, and copperhead snakes) are rare. This probably results from several factors, including the predominant local tissue toxicity of the venom of these snakes, the availability of medical care, and the proven benefits of antivenom. Although fatalities are rare, life-threatening systemic symptoms such as coagulopathies and shock can occur. The snake-bitten person and immediate attendants have no way of knowing whether these symptoms may develop prior to obtaining definitive medical care. Thus, the search for simple, safe, and effective immediate first-aid management continues.
Arterial or venous tourniquets or lymphatic constrictors seem reasonable, in that the venom will remain concentrated in that extremity, preventing systemic distribution and systemic toxicity. In fact, when dealing with primarily neurotoxic snakes such as cobras, constricting bandages and tourniquets have been shown to reduce weakness and respiratory arrest.1 However, when ultimately released, systemic toxicity may often develop rapidly.
When envenomation is a result of a bite from a snake such as the rattlesnake, whose toxicity is predominantly local, a clinical dilemma may arise as to the risk of damaging a limb or exacerbating the local toxicity vs. the risk of systemic toxicity. In these circumstances, the ischemic damage produced by a tourniquet may be worse than that expected from the original snake bite.2
In this study of a large number of snakebites, there may be selection bias (why some patients had tourniquets applied and others did not) and this prevents any firm conclusions. However, the findings appear to indicate that tourniquets offer little advantage concerning clinical outcome. For the present time, and especially with North American rattlesnakes and other pit vipers, it seems unlikely that application of a tourniquet will significantly improve outcome and may potentially exacerbate local toxicity. If traveling abroad or if bitten a great distance from definitive health care, a loose-fitting lymphatic constriction bandage may be reasonable. Venous and arterial occlusion are not advisable. If you receive a patient who has had a tourniquet applied, it is essential to have antivenom and resuscitation equipment ready prior to release of the tourniquet. (Dr. Hoffman is Associate Director of the New York City Poison Control Center, Bellevue and New York University Medical Centers, NY.)
References
1. Watt G, et al. Tourniquet application after cobra bite: Delay in the onset of neurotoxicity and the dangers of sudden release. Am J Trop Med Hyg 1988;38:618-622.
2. Trevett AJ, et al. Tourniquet injury in a Papuan snakebite victim. Trop Geogr Med 1993;45:305-307.
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