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<< Diagnosis And Management Of North American Snake And Scorpion Envenomations

Critical Appraisal Of The Literature

Unfortunately, evidence from well-conducted clinical research is in short supply to guide the management of envenomations. The literature supporting the ED evaluation and treatment of envenomations is generally weak, with few randomized trials or meta-analyses, and many review articles rehashing the same weak literature. Even the epidemiology of snakebites and scorpion stings is unclear, supported by large, but not population-based studies. The American Association of Poison Control Centers (AAPCC) compiles data from their Toxic Exposure Surveillance System (TESS) and publishes a comprehensive annual analysis of all toxic exposures, including envenomations, reported to all of the US Poison Control Centers. These reports include information on exposures, ED use, and clinical outcomes including death.1-2 In spite of this centralized clearinghouse/ reporting system, the consensus among experts in the field is that relying on self-reported data in the cases of envenomations that do not require ED visits results in a true incidence on envenomation that is as high as three to four times the number reported by TESS.3-5

The body of current literature on North American snake envenomations can generally be divided into two categories; pre-CroFabTM and post- CroFabTM. The Crotalidae Polyvalent Immune Fab Ovine (CroFabTM) was approved by the US Food and Drug Administration in October of 2000 essentially replacing the older Antivenom Crotalidae Polyvalent (ACP) available since 1954. Indications and administration of CroFabTM will be discussed in detail later in this article. Dozens of articles have been published on the topic of snake envenomations since the approval of CroFabTM, but the vast majority are review articles by a small pool of authors. Very little original research has been done since the CroFabTM research in 1999. The research that has been done has typically been in small populations and does not include a single randomized, blinded clinical trial of any medication, device, or technique for snakebite management.

The most recent comprehensive review identified was "North American snake envenomation: diagnosis, treatment and management" by Gold, Barish, and Dart in the Emergency Medicine Clinics of North America.4 This group of authors has written extensively in the emergency medicine and wilderness medicine literature on the topic of snake envenomations. In addition to the review article above, they participated in a four article symposium in the Annals of Emergency Medicine6 (presenting the data from the October 1999, North American Congress of Clinical Toxicology's, "Advances in the Management of Snakebite" Symposium), and a full review of venomous snakebites in the New England Journal of Medicine.5 Most of the recent research-based literature has focused on the limited areas of field management changes, trials of venom extraction devices, surgical management, and the expansion of the use of CroFabTM to non-Crotalidae envenomations; all of which will be discussed in this article.

Coral snake envenomations are not treated with CroFabTM and thus will be reviewed separately. It is fairly rare and human treatment studies include only case series.7 Additionally, one well-designed animal model study explored a technique for first aid of coral snake envenomations.8 Similarly, the evaluation and management of scorpion envenomations is supported by only one randomized, placebo controlled trial from Tunisia that enrolled a group with few severely affected people, and a systematic review including a randomized trial and three cohort studies.9,10

Non-native venomous snakes represent a heterogeneous group of animals kept by collectors and zoos. These snakes cause some dangerous envenomations each year in the United States, but the majority of the literature on evaluation and treatment of these snakes is published in the countries where the snakes are native. Most of these reports are low quality, but a few randomized, controlled trials support practice and are available through online databases by searching the specific species of snake responsible for the envenomation. Clinical guidelines are of virtually no help in guiding the assessment and treatment of envenomations.A search of the National Guidelines

Clearinghouse using various key words, including snakebite, envenomation, rattle snake, coral snake, scorpion, cobra, krait, venom, etc. yielded only one relevant guideline, entitled, "First aid: 2005 International Consensus Conference on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations," published in Circulation.11 The two suggestions for the first aid of snakebites are:

1) First aid providers should not apply suction to snakebite envenomation sites; this recommendation is supported by a few Class II and III studies.

2) Properly performed pressure immobilization is recommended for first aid treatment of Elapid snakebites. The first aid provider creates this pressure by applying a snug bandage that allows a finger to slip under the bandage; this recommendation is supported by a single Class III study in a porcine model of a coral snake envenomation.

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Last Modified: 08/17/2017
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