Most pit viper bites are painful within five minutes and soon display local swelling. Symptoms of hemotoxic envenomation are listed in Table 2.

Significant hypofibrinogenemia and thrombocytopenia lasting up to two weeks may occur after envenomation by North American pit vipers. Systemic reactions include a syndrome similar to disseminated intravascular coagulation, acute renal failure, hypovolemic shock, and death.

Renal failure is a common cause of delayed mortality from untreated snakebites in developing parts of the world. Immediately life-threatening conditions such as hypotension or shock occur in only about 7 percent of envenomations.

The venoms of coral snakes, exotic elapids and some Mojave rattlesnakes are neurotoxic and usually cause local numbness instead of pain and swelling, with the risk of cranial nerve palsies, respiratory paralysis, and death. Symptoms of neurotoxic envenomations are listed in Table 2.

Systemic reactions are difficult to reverse once they develop. In recent years, first aid measures for snakebites have been radically revised to exclude methods that were found to worsen a patient's condition, such as tight arterial tourniquets, aggressive wound incisions, and ice.

Initial treatment measures should include avoiding excessive activity, immobilizing the bitten extremity, and quickly transporting the victim to the nearest hospital. A wide, flat constriction band may be applied proximal to the bite to block only superficial venous and lymphatic flow typically, with about 20 mm Hg pressure and should be left in place until antivenin therapy, if indicated, is begun.

One or two fingers should easily slide beneath this band, since any impairment of arterial blood flow could increase tissue death. Upper extremities should be splinted as close to a gravity-neutral position as possible, preferably at heart level. No study has shown any benefit in survival or outcome from incision and suction.

An attempt should be made to identify the type of snake from a safe distance; however, no attempt should be made to capture or kill the snake.

Even if the snake is dead, it should not be picked up with the hands because envenomation by reflex biting after death of the snake has been reported. Equine-derived antivenin to snake venom is not recommended for the formularies of standard emergency medical services because of the potential for life-threatening allergic reactions from the antivenin and the length of time required for reconstitution up to 60 minutes.

Patients with snakebite must be admitted to an emergency department, where a poison control center should be contacted immediately. Wounds should be cleaned, and administration of tetanus toxoid or tetanus immune globulin should be considered for under-immunized or nonimmunized patients.

Patients should be given intravenous fluid, and blood should be drawn from an unaffected extremity. Complete recommendations for laboratory evaluations of snakebite are summarized in Table 3.

At least 25 percent of snakebites do not result in envenomation. Patients with asymptomatic pit viper bites should be observed for at least 12 hours before discharge. The patient should be given strict instructions to return to the hospital immediately if any of the following occurs: increase in pain or onset of redness or swelling; fever; epistaxis; bloody or dark urine; nausea or vomiting; faintness; shortness of breath; diaphoresis; or other symptoms except mild pain at the bite site.

Patients with bites from snakes with neurotoxic venom should be observed for at least 24 hours. A patient with suspected envenomation by the eastern coral snake needs immediate treatment with an appropriate antivenin, and necessary resuscitation measures should be implemented.

Equine-derived antivenin to snake venom has been the mainstay of hospital treatment for venomous snakebite for 35 years. For rattlesnake, cottonmouth, and copperhead bites, Antivenin Crotalidae Polyvalent ACP has been the standard available treatment; however, ACP is known to be highly allergenic because of its equine origin and may pose a greater risk to the patient than the snakebite.

The ovine sheep-derived antivenin, CroFab, received approval by the U. Food and Drug Administration for treatment of snakebites in October ; its use is still limited because of availability and expense, but it is likely to soon replace the equine crotalid antivenin.

A prospective trial using CroFab reports only a Eastern coral snakebites require Antivenin Micrurus fulvius. The specific antivenin for exotic snakebites may be acquired from the Arizona Poison and Drug Information Center An antivenin index is available from the American Zoo and Aquarium Association and the American Association of Poison Control Centers antivenin, and a permit is needed to import antivenin not held domestically.

Ideally, antivenin is administered within four hours of the snakebite, but it is effective for at least the first 24 hours.

Physicians should be present for antivenin administration, and epinephrine and antihistamines both histamine H 1 and H 2 receptor blockers should be at the bedside. Performing a skin test with horse serum is a matter of controversy because it delays therapy, has itself caused anaphylaxis and serum sickness, 24 , 25 and has been demonstrated to have a 10 to 36 percent false-negative rate 21 , 26 and a 33 percent false-positive rate.

In the event of a significant skin-test reaction, antivenin would be reserved for use in only the most severe cases and should only be given with careful monitoring, hydration, and premedication with antihistamines.

An alternative to skin testing is to premedicate all patients who will receive equine antivenin. The unpredictable nature of snakebites often makes assessment and management difficult.

Progressive local injury swelling, ecchymosis , a clinically evident coagulation abnormality, or systemic effects hypotension, altered mental status are strong indications for antivenin treatment. Withholding antivenin is recommended in patients with milder envenomations. Both ACP and CroFab are provided as dry powders and require reconstitution before administration.

Reconstitution can take up to 60 minutes and should be initiated immediately when the patient arrives in the emergency department. ACP can be reconstituted by injecting 10 mL of supplied sterile water diluent into each vial and swirling not shaking to mix, or by diluting 10 vials of antivenin in 1 L of normal saline.

The reconstituted antivenin amount will vary, depending on amount required is then diluted in mL of normal saline or 5 percent dextrose in water, and a trial dose of 5 to 10 mL is administered intravenously over five minutes. If no reaction occurs, the rate should be adjusted to give up to 10 vials in the first hour.

Additional infusions should be given every two hours until signs and symptoms are resolving. In contrast, the safer CroFab is given as a large initial dose to control the envenomation, and smaller subsequent doses are given as needed.

In one study, 20 a total of three to 12 vials of CroFab were given for initial control, and additional two-vial doses were given at six, 12, and 18 hours. For any eastern coral snake bite with possible envenomation, three to five vials of Antivenin Micrurus fulvius should be administered immediately.

If systemic manifestations are present, at least six to 10 vials should be administered. One exception is the Arizona coral snake Micruroides , which is not associated with human fatality and for which no antivenin exists. Immediate hypersensitivity reactions to any antivenin should be managed with epinephrine, antihistamines and supportive care to protect the respiratory and cardiovascular systems.

Serum sickness, which commonly occurs one to four weeks after administration of antivenin, presents with pruritus, urticaria, fever, and arthralgias.

Serum sickness can be successfully treated with systemic steroids. A popular scale for grading the severity of pit viper bites and estimating the antivenin dose is presented in Table 4.

It is important to remember that a patient must have serial evaluations, because an envenomation that appears to be mild on presentation can soon exhibit the hallmarks of a severe envenomation.

Doses of antivenin must not be reduced for children or small persons, since the amount of venom that needs to be neutralized is the same. Although once popular, surgical intervention with fasciotomy for venomous snakebite is now reserved for selected rare cases and should never be performed prophylactically.

The local and systemic effects of crotaline venom closely resemble the signs and symptoms of compartment syndrome 15 and cannot be reliably diagnosed in an envenomated patient without directly measuring the compartment pressure.

Fasciotomy should only be performed in patients with clinical signs and symptoms of compartment syndrome i. These criteria should be present despite elevation of the affected limb and administration of 20 vials of antivenin.

In a series of 1, cases of extremity bites, only two fasciotomies were necessary. Physicians should educate their patients on ways to prevent snakebites, as prevention is far preferable to treatment.

Many bites can be easily prevented by using common sense. For some precautions against snakebites, see the accompanying patient information handout on page Snyder CC, Knowles RP. Guidelines for practical management. Postgrad Med. Parrish HM. Incidence of treated snakebites in the United States.

Public Health Rep. Consroe P, Egen NB, Russell FE, Gerrish K, Smith DC, Sidki A, et al. Comparison of a new ovine antigen binding fragment Fab antivenin for United States Crotalidae with the commercial antivenin for protection against venom-induced lethality in mice.

Am J Trop Med Hyg. Juckett G. In: Rakel RE, ed. Saunders Manual of medical practice. New York: Saunders, —8. Litovitz TL, Klein-Schwartz W, Dyer KS, Shannon M, Lee S, Powers M.

Am J Emerg Med. Parrish H, Goldner J, Silberg S. Comparison between snakebites in children and adults.

Boyer LV, Seifert SA, Clark RF, McNally JT, Williams SR, Nordt SP, et al. Recurrent and per sistent coagulopathy following pit viper envenomation. Arch Intern Med. Wingert WA, Chan L.

Rattlesnake bites in southern California and rationale for recommended treatment. West J Med. Hall EL. Role of surgical intervention in the management of crotaline snake envenomation.

Ann Emerg Med. Stewart ME, Greenland S, Hoffman JR. First-aid treatment of poisonous snakebite: are currently recommended procedures justified?. Dart RC, Gustafson RA. Failure of electric shock treatment for rattlesnake envenomation. Suchard JR, LoVecchio F.

Envenomations by rattlesnakes thought to be dead. N Engl J Med. McKinney PE. Español Other Languages. How to Prevent or Respond to a Snake Bite. Minus Related Pages. Highlights If you see a snake in your home, immediately call the animal control agency in your county.

Be aware of snakes that may be swimming in the water or hiding under debris or other objects. If you or someone you know are bitten, try to see and remember the color and shape of the snake.

Do not pick up a snake or try to trap it. Last Reviewed: October 12, Source: National Center for Environmental Health NCEH , Agency for Toxic Substances and Disease Registry ATSDR , National Center for Injury Prevention and Control NCIPC.

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