Bites and envenomations account for 3% of phone calls to poison control centers.1 In North America, venomous animals vary by specific region and include varied terrestrial vertebrates and invertebrates. Venomous bites are of particular concern in the pediatric population, with the highest morbidity and mortality occurring in smaller patients. Diagnosis and management strategies for envenomation vary according to the type of animal, specific toxic properties of the venom, location of the bite, time elapsed since exposure, appearance of the wound, systemic symptoms, size of the child, and history and physical examination findings (Table 176-1). It is important to keep in mind that unwitnessed bites can occur in younger children. This chapter specifically addresses the presentation and management of common snake bites, as well as black widow and brown recluse spider bites.
TABLE 176-1Important Details to Elicit on History and Physical Examination |Favorite Table|Download (.pdf) TABLE 176-1 Important Details to Elicit on History and Physical Examination
|Description of animal (identification may not always be possible) |
|Time of exposure |
|Location of wound on the body |
|Changes in appearance of wounds before presentation |
|Local symptoms (paresthesia, weakness, swelling) |
|Systemic symptoms (dizziness, diaphoresis, respiratory compromise, seizures, muscle cramping, bleeding) |
|Physical Examination |
|Patient’s weight |
|Wound characteristics (erythema, edema, target lesion, bleeding, necrosis, hemorrhagic blebs) |
|Local compromise (airway compromise, perfusion, neurovascular status) |
|Systemic compromise (vital signs and end-organ perfusion) |
In North America, the most common venomous snakes belong to the Viperidae family (Crotalinae subfamily) and are commonly referred to as pit vipers.
Common features of their general appearance that differentiate them from nonpoisonous snakes include a triangular head, vertically positioned elliptical pupils, heat-sensing nostril pits, and a single row of scales at the tail. In North America, common crotaline snakes include (1) eastern and western diamondbacks and other multiple species of rattlesnakes, (2) copperheads, and (3) water moccasins (also called cottonmouths); envenomation by rattlesnakes is usually more severe. In addition to pit vipers, coral snakes (Elapidae family) can be found in the southeastern and southwestern United States. Coral snake envenomation is less common than pit viper bites but can cause serious neurologic dysfunction.
About 75% of snake bites, from venomous snakes, occur with envenomation. It is important to remember that a snake bite deposits the same amount of venom regardless of the size of the victim. Therefore a smaller patient will have a more significant venom load per kilogram and will be at higher risk for morbidity and mortality than larger children and adults. Crotaline venom contains a mixture of multiple enzymes and toxic substances. It is usually deposited subcutaneously, but rarely there can be subfascial or intravascular deposition. Local effects start approximately 15 to 30 minutes after the bite and include pain, paresthesias, numbness, edema, ecchymosis, necrosis, ...