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Most snakebites that occur are due to nonvenomous snakes. However, about 7000–8000 individuals in the United States are bitten by venomous snakes each year, and of these, 5 will die (www.cdc.gov). In the developing countries with temperate and tropical climates, snakebites are a more serious problem because access to healthcare resources may be quite sparse, and it is estimated at 20,000–94,000 individuals die worldwide from snakebites yearly. Venomous snakes belong to the families Viperidae (pit vipers including rattlesnakes, copperheads, and cottonmouth water moccasins), Elapidae (including cobras and coral snakes), Lamprophiidae (asps), and Colubridae, which are largely nonvenomous but have a few toxic species. Most snakes have venom glands situated below and behind the eyes that are connected by ducts to hollow maxillary fangs. The fangs are retractable in most pit vipers and brought into an upright position for striking. It is notable when evaluating a snake bite to know that about 20% of pit viper bites and higher percentages of other snakebite bites contain no venom. Signifcant envenomation occurs in only about 50% of all snakebites. Snake venoms are complex mixtures of enzymes, glycoproteins, and low-molecular-weight polypeptides, among other constituents, that lead to tissue hemorrhage, vascular leak, and proteolysis with tissue necrolysis. Some snake venoms have myocardial depressant factors and neurotoxins as well. The time from the bite to symptom onset is variable and depends on the species of snake, amount of envenomation, and site of the bite. Progressive local pain, swelling, and ecchymosis are common with the development of hemorrhagic or serum-flled bullae. Systemic findings are quite variable and may include tachycardia or bradycardia, hypotension, weakness, coagulopathy, renal dysfunction, and neurologic dysfunction. If a patient has suffered a venomous snakebite, the most important aspect of prehospital care is supportive care with rapid transport to a medical facility where antivenom therapy is available. It is notable that most of the first-aid measures recommended in the past are of little benefit and may actually worsen local tissue damage. For supportive care, a splint may be applied to decrease pain and lessen bleeding. If possible, the injured limb should be elevated to the level of the heart. Attempting to capture the offending snake alive or dead is not recommended and could only lead to more injury in others. Digital photographs taken from a safe distance away will suffice to allow identification of the snake. There is no role for incising or applying suction to the wound. This will not allow the venom to be removed and may introduce additional bacterial contamination. Applying a tight tourniquet also does not limit the spread of venom and may endanger the affected limb by limiting blood flow. The only role for pressure-immobilization is in Elapid venoms (cobra), which are neurotoxic. This technique requires specific training to effectively apply to an entire limb and to a precise pressure. After application, the victim must be carried from the field and remain immobile in order to prevent the spread of the neurotoxin. Upon arrival at the hospital, victims of snakebites should be carefully monitored for signs of signifcant envenomation that would require antivenom therapy. The patient should be monitored on telemetry with frequent vital signs. The area of snakebite should be cleaned and clearly marked. Limb circumference should be measured every 15 minutes. The extremity should remain at the level of the heart. Volume resuscitation should ensue, and large-bore IV access should be maintained. Indications for the use of antivenom therapy include signifcant local progression including soft tissue swelling that crosses a joint or involves more than half of the bitten limb. In addition, any evidence of systemic involvement should prompt the use of antivenom therapy. Signs of systemic involvement could include hypotension, altered mental status, coagulopathy, renal dysfunction, rhabdomyolysis, hepatic dysfunction, or neurologic dysfunction. It is important to know the type of snake when administering antivenom therapy because it is specific to the type of snake. Prompt and serious allergic reactions can occur including anaphylaxis. The use of IV antihistamines is typical as a pretreatment. Posttreatment serum sickness reactions may occur.
