Poisonous snakebites
Poisonous snakebites: Excerpt from Professional Guide to Diseases (Eighth Edition)
Poisonous snakebites are medical emergencies. With prompt, correct treatment, they need not be fatal. The only poisonous snakes in the United States are pit vipers (Crotalidae) and coral snakes (Elapidae). Pit vipers, such as rattlesnakes, water moccasins (cottonmouths), and copperheads, 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. The fangs of coral snakes are short, but have teeth behind them. Coral snakes have distinctive red, black, and yellow bands (yellow bands always border red ones).
Causes and incidence
Of the approximately 45,000 snakebites that occur in the United States each year, 7,000 to 8,000 are from poisonous snakes, resulting in 5 to 6 deaths. Such bites are most common during summer afternoons in grassy or rocky habitats.
Pit vipers are nocturnal but active snakes that are responsible for 99% of venomous snake bites in the United States. Coral snakes are also nocturnal, but their placidity makes coral snake bites less common than pit viper bites. Coral snakes tend to bite with a chewing motion, and may leave multiple fang marks, small lacerations, and extensive tissue destruction.
Signs and symptoms
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, local elevation in skin temperature, fever, skin discoloration, petechiae, ecchymoses, blebs, blisters, bloody wound discharge, and local necrosis. (See After a snakebite.)
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:
❑ prolonged bleeding time and partial thromboplastin time
❑ decreased hemoglobin level and hematocrit
❑ sharply decreased platelet count (less than 200,000/mm">3)
❑ urinalysis disclosing hematuria
❑ increased white blood cell count in victims who develop an infection (a snake’s mouth typically contains gram-negative bacteria)
❑ pulmonary edema or emboli 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 older than age 40)
❑ possibly abnormal EEG findings in cases of severe envenomation.
Treatment
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. Remember that the goal of applying a tourniquet is to obstruct lymphatic drainage, not blood flow.
❑ When indicated, apply the tourniquet so that it’s slightly constrictive, obstructing only lymphatic and superficial venous blood flow. Apply the band about 4(10 cm) above the fang marks or just above the first joint proximal to the bite. The tourniquet should be loose enough to allow a finger between the band and the skin. After the tourniquet is in place, don’t remove it until a physician has examined the victim.
Alert Don’t apply a tourniquet if more than 30 minutes have elapsed since the bite. Keep in mind also that total tourniquet time shouldn’t exceed 2 hours and that the use of a tourniquet shouldn’t delay antivenin administration. Loss of a limb is possible if a tourniquet is too tight or if tourniquet time is too long.
❑ If the patient is more than a few hours away from a hospital, wash the skin over the fang marks. Within 5 to 15 minutes of a pit viper bite, make an incision through the fang marks about ½"(1.3 cm) long and ⅛"(3.2 mm) deep. Be especially careful if the bite is on the hand, where blood vessels and tendons are close to the skin surface.
Using a bulb syringe — or, if no other means is available, mouth suction — apply suction for up to 1 hour in the absence of antivenin administration.
Alert Remember, an incision and suction are effective only in pit viper bites and only within 1 hour of the bite. Suction is also indicated if transport time to an emergency facility would exceed 30 minutes. Mouth suction is contraindicated if the rescuer has oral ulcers, if the victim is close to a medical facility, or if antivenin can be given promptly.
Alert 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.
❑ Record the signs and symptoms of progressive envenomation and when they develop. Most snakebite victims are hospitalized for only 24 to 48 hours. Treatment usually consists of antivenin administration, but minor snakebites may not require antivenin. Other treatments include tetanus toxoid or tetanus immune globulin; various broad-spectrum antibiotics; and, depending on respiratory status, severity of pain, and the type of snakebite, acetaminophen, codeine, morphine, or meperidine. (Opioids are contraindicated for the treatment of coral snakebites.)
Necrotic snakebites usually need surgical debridement after 3 or 4 days. Intense, rapidly progressive edema requires fasciotomy within 2 or 3 hours of the bite; extreme envenomation may require amputation of the limb and subsequent reconstructive surgery, rehabilitation, and physical therapy.
Special considerations
When the patient arrives at the hospital, immobilize the extremity if this hasn’t already been done. If a tight tourniquet has been applied within the past hour, apply a loose tourniquet proximally and remove the first tourniquet. Release the second tourniquet gradually during antivenin administration as ordered. A sudden release of venom into the bloodstream can cause cardiorespiratory collapse, so keep emergency equipment handy.
❑ On a flow sheet, document vital signs, level of consciousness, skin color, swelling, respiratory status, a description of the bite and surrounding area, and symptoms. Monitor vital signs every 15 minutes and check for a pulse in the affected limb.
❑ Start an I.V. line with a large-bore needle for antivenin administration. Severe bites that result in coagulotoxic signs and symptoms may require two I.V. lines: one for antivenin and one for blood products.
❑ Before antivenin administration, obtain a patient history of allergies and other medical problems. Perform hypersensitivity tests as ordered and assist with desensitization as needed. During antivenin administration, keep epinephrine, oxygen, and vasopressors available to combat anaphylaxis from horse serum.
❑ Give packed red blood cells, I.V. fluids and, possibly, fresh frozen plasma or platelets, as ordered, to counteract coagulotoxicity and maintain blood pressure.
❑ If the patient develops respiratory distress and requires endotracheal intubation or a tracheotomy, provide good tracheostomy care.
❑ Give analgesics as needed. Don’t give opioids to coral snakebite victims. Clean the snakebite using sterile technique. Open, debride, and drain any blebs and blisters because they may contain venom. Change dressings daily.
❑ If the patient requires hospitalization for more than 48 hours, position him carefully to avoid contractures. Perform passive exercises until the fourth day after the bite; after that, perform active exercises and give whirlpool treatments as ordered.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
More About Campylobacter food poisoning
More Medical Textbooks Online about Campylobacter food poisoning
Review other book chapters online related to Campylobacter food poisoning:
Medical Books Excerpts
- Vomiting
- "In A Page: Pediatric Signs and Symptoms" (2007)
- [ read ]
- Vomiting
- "Handbook of Signs & Symptoms (Third Edition)" (2006)
- [ read ]
- Poisoning
- "Professional Guide to Diseases (Eighth Edition)" (2005)
- [ read ]
- Vomiting
- "Professional Guide to Signs & Symptoms (Fifth Edition)" (2006)
- [ read ]
- Nausea and Vomiting
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
- [ read ]
- Vomiting
- "Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series" (2007)
- [ read ]
- Vomiting
- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
- [ read ]
- Vomiting
- "Nursing: Interpreting Signs and Symptoms" (2007)
- [ read ]
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Poisoning (Professional Guide to Diseases (Eighth Edition))
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
