Poisonous Snakebites

Each year, poisonous snakes bite about 8,000 people in the United States. Snakebites occur most during summer afternoons in grassy or rocky habitats. A poisonous snakebite is a medical emergency. With prompt, correct treatment, it need not be fatal. However, antivenin against an exotic venomous snake isn't always readily available.

Causes

The only poisonous snakes found in nature in the United States are pit vipers (Crotalidae) and coral snakes (Elapidae). Pit vipers include rattlesnakes, water moccasins (cottonmouths), and copperheads. They have a pitted depression between their eyes and nostrils, and two fangs ¾" to 1 ¼" (1.9 to 3.2 cm) long. Because a snake's fangs may break off or grow behind old ones, a pit viper can have anywhere from one to four fangs.

Because coral snakes are nocturnal and placid, their bites are less common than pit viper bites; pit vipers are also nocturnal but are more active. Coral snake fangs are short but have teeth behind them. Coral snakes have distinctive red, black, and yellow bands (yellow bands always border red ones), tend to bite with a chewing motion, and may leave multiple fang marks, small lacerations, and extensive tissue destruction.

Many snakebites are associated with activities involving amateur snake keeping and handling and commonly result from carelessness or daring on the part of the snake handler. Handling snakes that appear to be dead can lead to a venomous snakebite secondary to postmortem reflex action of the snake's head. Snakebite can occur even by inadvertently striking a finger against a fang of a preserved snake.

Signs and Symptoms

The majority of snake bites are harmless. Still, medical treatment is necessary. If you are allergic to snakes, or are attacked by a poisonous snake, the following symptoms may occur.

• Blurred vision
• Bloody discharge Swelling
• Numbness
• Fever

Diagnostic tests

Laboratory test values can help to identify the extent of envenomation and to provide guidelines for supportive treatment. Abnormal test results may include prolonged bleeding time and partial thromboplastin time, decreased hemoglobin and hematocrit levels, sharply decreased platelet count (less than 200,000/mm3), urinalysis showing hematuria and, in infection (snake mouths contain gram­negative bacteria), increased white blood cell count.

Chest X-rays may show pulmonary edema or emboli; an electrocardiogram may show tachycardia and ectopic beats; and severe envenomation may produce abnormal findings on an electroencephalogram.

Treatment

• Prompt, appropriate first aid can reduce venom absorption and prevent severe symptoms. Antivenin administration and other treatments should follow.
• If possible, identify the snake, but don't waste time trying to find it.
• Apply a bandage, wrapped two to four inches above the bite, to help slow the venom. This should not cut off the flow of blood from a vein or artery - the band should be loose enough to slip a finger under it.
• Immediately immobilize the patient's limb below heart level in a horizontal position, and instruct the victim to remain as quiet as possible.
• Wash the skin over the fang marks.
• Transport the victim as quickly as possible, keeping him warm and quiet. Record the signs and symptoms of progressive envenomation and when they develop.
• Antivenin administration is required in life­threatening circumstances. Prepare and administer the antivenin according to the manufacturer's directions. Watch the patient closely for signs of sensitivity and anaphylaxis. Keep emergency epinephrine on hand in case the patient develops such problems.

Prevention

• Even though most snakes are not poisonous, avoid picking up or playing with any snake unless you have been properly trained.
• Many serious snakebites occur when someone deliberately provokes a snake.
• If your encounter a snake, do not run or move. Snakes generally attack moving objects.
• Wear long pants or boots when hiking or working in tall grassy areas.
• Teach your child to be cautious and alert when climbing rocks.

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