As the weather is warming up and we start to spend more time outside, we also start spending more time being exposed to things that may bite us. On that long list are snakes. In the US alone there are 8000 venomous snake bites yearly, with most of them between April and October. Only 0.2% of venomous bites result in death, however 1 or 2 of those deaths occur in Texas yearly.
There are two kinds of poisonous snakes in Texas. The most common kind is the pit viper. It includes the copperhead, cottonmouth, and rattlesnake. They get their name from heat sensing pits in their head, along with their elliptical pupils and triangle head. They can be found in almost any habitat. The second type of poisonous snake is the coral snake. It is easily identified by the red, yellow, and black bands on its body. The snakes can be differentiated from the non-poisonous king snake by the mnemonic “red on yellow, kill a fellow; red on black, venom lack”. The coral snake has very short teeth and injects a very potent neurotoxin.
Pit vipers and coral snake venom are very different in the effects they produce. Venom in both is mostly water. The enzymes in the venom easily break down subcutaneous tissue, red blood cell membranes, and activate the coagulation cascade leading to a coagulopathy. This leads to leaky blood vessels and edema. Coral snake venom is typically more of a neurotoxin that can lead to severe muscle weakness and respiratory failure.
Snake bites can happen to anyone; however certain select groups seem to be more susceptible to being bitten by a snake. A typical snake envenomation is seen in 18-28 years old, males, and on the extremities. An envenomation from a pit viper often results in swelling, bruising, and blisters in the affected extremity. This swelling and bruising can progress rapidly. There may be systemic symptoms such as hypotension, parenthesis, epistaxis, and respiratory distress. Symptoms may be delayed if the bite is on the lower extremity. Symptoms are also more severe in children.
Treatment of a snake bite is separated into pre-hospital care and hospital care. Most snake bites are either non venomous snake bites or “dry” bites. Dry bites are 50% of coral snakes and 25% of pit vipers. Many techniques for removal of the venom are no longer used such as sucking out the wound, tourniquets, electrical shock or ice packs. Good prehospital care is limit movement of the affected extremity, follow the ABC’s, and quick transport to a facility that has antivenin.
Envenomation is graded as mild, moderate, or severe. Mild envenomation has local pain and swelling but no systemic signs or abnormal lab values. Moderate envenomation has severe pain and swelling of the affected area and systemic symptoms with abnormal lab values. Severe envenomation is severe lab abnormalities with clinical signs of shock. The grades may change significantly during the evaluation process. Coral snakes may show no initial signs of envenomation and are still graded as severe.
Antivenin is the treatment of choice in significant envenomation of pit vipers and coral snakes. CroFab (Crotalidae polyvalent immune Antibody) has replaced horse antivenin because of its effectiveness. Antivenin binds to the toxins in the venom to prevent local and systemic effects. Best results are achieved if given in the first 4-6 hours of an envenomation. Sometimes the swelling is so severe that the patients will need a fasciotomy (a procedure to cut open the fascia to allow blood flow to a certain area).
Antibiotics are also indicated as these wounds are also high risk for an infection. Tetanus should also be given in most snake bites.
Most snake bites need to be observed in the hospital. “Dry” pit viper bites should be observed for 8-10 hours. Coral snakes should be observed for 24 hours. Those that are envenomed need admission to the hospital with possible repeat doses of antivenin and lab testing. Fasciotomies are rarely needed anymore.
“As we emerge from spring into summer, remember that the best treatment of snake bites is prevention. When outdoors please be aware of your surroundings, do not venture into places with known snakes and do not try to approach/ handle a snake,” states Dr. Larry Dencklau, medical director of the emergency department at Lake Pointe Medical Center. “If a bite happens, bringing the patient to the emergency room is the best course of action.”
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