More on Treatment of Snake Bites
More on Treatment of Snake Bites
ABSTRACT & COMMENTARY
Synopsis: Most children bitten by snakes in the United States completely recover with only supportive care and can be treated safely and cost-effectively as outpatients if no signs of major envenomation are noted within eight hours of the bite.
Source: Lopoo JB, et al. Treating the snake bitten child in North America: A study of pit viper bites. J Pediatr Surg 1998;33:1593-1599.
Because proper management of venomous snake bites is still somewhat ill defined and controversial, Lopoo and associates from the Children’s Hospital of Oklahoma retrospectively reviewed the records of 37 snakebitten children, age 1-19 years, seen in their emergency department (ED) between 1987 and 1997. Oklahoma ranks in the top 10 states for the number of snake bites annually reported. Twenty-two of 37 patients (59%) were boys. All bites occurred between May and September, most frequently in May. All patients were bitten on the extremities, with 69% of bites on the feet or ankles. Copperhead snakes accounted for 18 bites, rattlesnakes for three, and the remaining bites (16) were by unidentified snakes. Fifty-four percent of the children were considered to have major envenomation, as indicated by systemic symptomatology, laboratory analyses, or need for surgery. All children made full recovery, with most (92%) receiving only supportive care. The average time between the bite and entering the ED was eight hours. It was possible by this time to correctly identify children with major envenomations as well as those who required specific interventions, such as the administration of clotting factors or surgery.
COMMENT BY SYDNEY Z. SPIESEL, PhD, MD, FAAP
Poisonous snakes in the United States inflict about 8000 bites each year. Almost all of U.S. snake bites are attributable to pit vipers: rattlesnakes (15 species) and their close relatives, copperheads and water moccasins. Some of these bites are of trivial consequence (a snake may bite but may not successfully envenomate the victim; some venoms are less toxic than others), while some may be gravely serious. Because both poisonous snakes and their victims are not uniformly distributed geographically, many physicians will never see a single snakebite while others will treat a great many. Snakebite is rarely an urban risk and there are no poisonous snakes in Alaska or Hawaii and relatively few in Canada. The risk of snakebite is especially great in parts of the Great Plains, in the lower Mississippi Valley and the Gulf Coast, in the southern Appalachians, and in parts of the Southwest. Snakebite is particularly a pediatric problem because the incidence is highest in children 5-15 years old and because a given venom dose will be more concentrated as it distributes in a smaller body.
This study comes from the major pediatric referral center in Oklahoma, a state rich enough in pit vipers to afford Lopoo et al ample opportunity to evaluate treatments and outcomes. Over a 10-year period, 37 pediatric snakebite victims were admitted and treated. Half of the offending snakes were identified as copperheads, one of the least dangerous poisonous snakes because it carries less venom than most other North American pit vipers and because the venom is markedly less toxic than any other snake venom in the United States. Of the remaining reported snakebites, a few were known to have been inflicted by rattlesnakes, but most of the time the snake was not identified. About half the victims were considered to have had "major" envenomations because of systemic symptoms or signs (nausea, coagulopathies) or compartment syndromes requiring fasciotomy (four patients). Most of the care was routine and supportive: fluid and antibiotics. The use of the one specific treatment—pit viper antivenin—was particularly problematic in this population. Antivenin should only be used for serious envenomations and patients must be screened for allergy to this equine product; in addition, enough must be given to be useful, and it must be given within eight hours—the earlier the better. Unfortunately, of the few candidates for whom this treatment might have been helpful, a surprisingly large number could not be given this drug because they were found to be already allergic to it, and the one child who received an appropriate treatment with antivenin developed anaphylactic shock. Since all the other patients in this study did well without antivenin, Lopoo et al urge that it be reserved for critically ill children thought to have received a large amount of venom. Although this drug is often overused (particularly in settings with little snakebite experience), I think it is probably a good idea to also administer antivenin early to nonallergic children who have clearly been envenomed by the more dangerous pit vipers: diamondback and Mohave rattlesnakes, for example.
Noting that in many of their patients, snakebite was a self-limiting problem without serious consequences, Lopoo et al urge that bitten children be observed for eight hours (and given local wound treatment) in an outpatient setting. They suggest that bitten children not be admitted to the hospital unless signs of systemic intoxication or compartment syndrome appear. These seem to be reasonable recommendations. In the early evaluation of the snakebitten child, it is probably worth noting that—except in the rarest circumstance, involving a greatly obese victim—if a bite by a poisonous North American snake is not painful, then envenomation has not occurred. (Dr. Spiesel is Assistant Clinical Professor of Pediatrics, Yale University School of Medicine, and a long-time student of snakebite and herpetology.)
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