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Snake Bites - Symptoms And Treatment of Snakebites

Causes of Snake Bites

The only poisonous snakes 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 1¼" (2 to 3 cm) long. Because fangs may break off or grow behind old ones, some snakes may have one, three, or four fangs.

Signs and symptoms of Snake Bites

Most snakebites happen on the arms and legs, below the elbow or knee. Bites to the head or trunk are most dangerous, but any bite into a blood vessel is dangerous, regardless of location.

Most pit viper bites that result in envenomation cause immediate and progressively severe pain and edema (the entire extremity may swell within a few hours), local elevation in skin temperature, fever, skin discoloration, petechiae, ecchymoses, blebs, blisters, bloody wound discharge, and local necrosis.

Because pit viper venom is neuro­toxic, pit viper bites may cause local and facial numbness and tingling, fasciculation and twitching of skeletal muscles, seizures (especially in children), extreme anxiety, difficulty speaking, fainting, weakness, dizziness, excessive sweating, occasional paralysis, mild to severe respiratory distress, headache, blurred vision, marked thirst and, in severe envenomation, coma and death. Pit viper venom may also impair coagulation and cause hematemesis, hematuria, melena, bleeding gums, and internal bleeding. Other symptoms of pit viper bites include tachycardia, lympha­denopathy, nausea, vomiting, diarrhea, hypotension, and shock.

The reaction to coral snakebite is usually delayed-sometimes up to several hours. These snakebites cause little or no local tissue reaction (local pain, swelling, or necrosis). However, because coral snake venom is neurotoxic, a reaction can progress swiftly, producing such effects as local paresthesia, drowsiness, nausea, vomiting, difficulty swallowing, marked salivation, dysphonia, ptosis, blurred vision, miosis, respiratory distress and possible respiratory failure, loss of muscle coordination and, possibly, shock with cardiovascular collapse and death.

Diagnosis

The patient's history and account of the injury, observation of fang marks, snake identification (when possible), and progressive symptoms of envenomation all point to poisonous snakebite. Laboratory test results help identify the extent of envenomation and provide guidelines for supportive treatment.

Abnormal test results in poisonous snakebites may include the following: . prolonged bleeding time and partial thromboplastin time

• decreased hemoglobin and hematocrit values
• sharply decreased platelet count (less than 200,000/ul)
• urinalysis disclosing hematuria
• increased white blood cell count in victims who develop an infection (the mouth of a snake typically contains gram-negative bacteria)
• pulmonary edema as shown on chest X-ray
• possibly tachycardia and ectopic heart­beats on the electrocardiogram (usually necessary only in cases of severe envenomation for a patient over age 40)
• possibly abnormal EEG findings in cases of severe envenomation.

Treatment of Snake Bites

Prompt, appropriate first aid can reduce venom absorption and prevent severe symptoms.

• If possible, identify the snake, but don't waste time trying to find it.
• Place the victim in the supine position to slow venom metabolism and absorption.
• Don't give the victim any food, beverage, or medication orally.
• Authorities disagree about what constitutes appropriate prehospital care.
• Some recommend against placing a constrictive tourniquet (band) on the affected limb unless the victim is far from a medical facility.
• Whether you apply a tourniquet or not, immediately immobilize the victim's affected limb below heart level, and instruct the victim to remain as quiet as possible.
• If a tourniquet is applied, the victim or the person applying the tourniquet should check the victim's distal pulses regularly and loosen the tourniquet slightly as needed to maintain circulation. CLINICAL TIP Remember that the goal of applying a tourniquet is to obstruct lymphatic drainage, not blood flow. The use of a tourniquet in pre­hospital care is controversial.
• Never give the victim alcoholic drinks or stimulants because they speed venom absorption. Never apply ice to a snakebite because it will increase tissue damage.
• There is often an urgent need for treatment with oxygen, attachment to a drip and possibly anti-shock treatment.

Special considerations and prevention

• Even though most snakes are not poisonous, avoid picking up or playing with any snake unless you have been properly trained.
• Rapidly apply antiseptic cleanser to the entire area and place cold compress as closely as possible without interfering with suction process.
• DO NOT cut into a snake bite with a knife or razor.
• Keep victim warm and immobilize as practical. Movement to proper treatment facility is more crucial than maintaining immobile status. Maintain above treatment functions throughout.
• DO NOT give the victim anything by mouth.