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

Treatment

Prompt administration of specific antivenom, when available and indicated, and supportive care of airway, breathing, circulation, and neurologic function are the foundation of ED care for these envonomations and stings. Tetanus prophylaxis should be offered if there is no clear history of tetanus immunization within five years and encouraged if it has been more than ten years. Critical care services including mechanical ventilation, pressor and inotrope administration, intravenous hydration and nutrition, and prolonged sedation are sometimes required in severe envenomations. No credible evidence supports the use of prophylactic antibiotics or steroids in scorpion, coral snake, or non-native venomous snake envenomations. Consideration of special needs for individual cases is discussed later in this article.

Adverse effects of antivenom administration, often anaphylaxis, occur in the majority of patients who receive antivenom derived from animal serum. Universal preparation to treat these reactions is required for all patients receiving antivenom. Two prospective case series, one from Australia and one from South Africa, found over a 70% occurrence of immediate hypersensitivity reactions, with about half of these anaphylaxis, after administration of (non-Fab derived) snake antivenom.58-59 In a study of 181 patients who received Antivenom Crotalid

Polyvalent (ACP), 56% experienced a rash 3 to 21 days after antivenom with several experiencing subjective fever, itching, and arthralgias as well. These findings appeared dose related with nearly all patients receiving 30 or more vials of antivenom experiencing a rash. Serum sickness, discussed previously, is much more common with the horse serum derived antivenoms used for coral snake, exotic snake, and scorpion envenomations than with CroFab™.4 In a prospective observation study of 116 patients receiving scorpion (Centruroides) antivenom for severe envenomations, four patients had immediate reactions: Three cases of rash and one case of anaphylaxis. Follow-up of the 99 patients was conducted at one year; 61% experienced delayed hypersensitivity reaction and serum sickness, which responded to steroids and antihistamines.60 A prednisone taper, beginning at 60mg per day over seven to ten days, along with oral antihistamines, is the most common treatments for serum sickness.61 One randomized, controlled trial and a systematic review of that trial concluded that the administration of 0.25mg of 1:1000 epinephrine sub- cutaneously in the forearm immediately before antivenom infusion is started markedly reduced the incidence of immediate hypersensitivity reactions; absolute risk reduction 30%, number-needed-to-treat was 3.3, with no significant adverse effects attributable to epinephrine.62-63

Coral Snakes

Place coral snake specific antivenom at the bedside of all patients with a suspected coral snake bite. Observe and treat at the first sign of envenomation, however minor. The antivenom is derived from horse serum and may result in an immediate or delayed hypersensitivity reaction. The incidence data for adverse reactions is not available.

Non-native Venomous Snakes

Early and sufficient antivenom administration is the key to treatment of non-native venomous snakebites. Again, positive identification of the snake is essential so that specific antivenom can be obtained. Local zoos are required to store antivenom, when available, for every venomous species in their collection. Call your local zoo for availability of antivenom or call the American Zoo and Aquarium Association (301-562-0777) for access to their antivenom index. Collectors of venomous snakes are not bound by these same regulations, so a search for antivenom must be conducted, after identification of the snake, through local poison control centers or the American Association of Poison Control Centers (800-222-1222).

Scorpions

Supportive care is the cornerstone of treatment. Scorpion antivenom for Centruroides sculpturatus (aka exilicauda), the only scorpion species in the US dangerous to humans, was previously available only in Arizona, but production stopped in 2001. Stocks became outdated in 2004, and are not FDA approved for the treatment of scorpion envenomations. In addition, there are contradictory findings from studies of the effectiveness of antivenom in treating scorpion stings. Complicating this, is the fact that most studies have been done on non-North American scorpion envenomations. For example, one randomized, placebo-controlled trial in Tunisia and a systematic review including the randomized trial and three cohort studies concluded that there was no benefit to administering antivenom.9-10 More relevant to US practice, but weaker evidence, a case series and a natural before-after analysis of cohorts before and after depletion of stocks of antivenom, suggest that use of antivenom in children may prevent some hospital and intensive-care unit admissions. 64-65

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Last Modified: 08/17/2017
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