Snakebite (Snake Bite)

Poisonous snakes inject venom using modified salivary glands.

• Snakes are remarkable animals, successful on land, in the sea, in forests, in grasslands, in lakes, and deserts. Despite their sinister reputation, snakes are almost always more scared of you than you are of them. Most snakes do not act aggressively toward humans without provocation.
• Snakes are meat eaters and they catch prey that includes insects, birds, small mammals, and other reptiles, sometimes including other snakes. Only about 400 of 3,000 snake species worldwide are venomous. About 25 species of venomous snakes are found in North America.
• Many snakes kill their prey by constriction. In constriction, a snake suffocates its prey by tightening its hold around the chest, preventing breathing or causing direct cardiac arrest. Snakes do not kill by crushing prey. Some snakes grab prey with their teeth and then swallow it whole.
• Snakes are cold-blooded. Thus, they are unable to increase their body temperature and stay active when it is cold outside. They are most active at 25-32 C (77-90 F).

The Bite

• Poisonous snakes inject venom using modified salivary glands.
• During envenomation (the bite that injects venom or poison), the venom passes from the venom gland through a duct into the snake's fangs, and finally into its prey.
• Not all bites lead to envenomation. Snakes can regulate whether to release venom and how much to release. "Dry Bites" (a bite where no venom is injected) occur in between 25%-50% of snake bites.
• This variation is species-specific with approximately 25% of pit-viper bites and up to 50% of coral snake bites being "dry." Snake venom is a combination of numerous substances with varying effects.
• In simple terms, these proteins can be divided into 4 categories:
  1. Cytotoxins cause local tissue damage.
  2. Hemotoxins cause internal bleeding.
  3. Neurotoxins affect the nervous system.
  4. Cardiotoxins acts directly on the heart.
• The number of bites and fatalities varies markedly by geographic region. Reporting of snakebites is not mandatory in many areas of the world, making it difficult to determine the number of bites. Many articles are based on population models with multiple assumptions leading to a wide range of statistical reporting.
• Snakebites are more common in tropical regions and primarily agricultural areas. In these areas, large numbers of people coexist with numerous snakes. Very few deaths occur per year from snakebites in the United States.
• People provoke bites by handling or even attacking snakes in a significant number of cases in the United States.

Bites by venomous snakes result in a wide range of effects. They range from simple puncture wounds to life-threatening illnesses and death. The findings following a venomous snakebite can be misleading. A victim can have no initial significant symptoms, and then suddenly develop breathing difficulty and go into shock.

Signs and symptoms of snakebites can be broken into a few major categories:

• Local effects: These are the effects on the local skin and tissue surrounding the bite area. Bites by vipers and some cobras (Naja and other genera) are painful and tender. They can be severely swollen and can bleed and blister. Some cobra venoms can also kill the tissue around the site of the bite.
• Bleeding: Bites by vipers and some Australian elapids can cause changes in the victim's hematologic system causing bleeding. this bleeding can be localized or diffuse. Internal organs can be involved. A victim may bleed from the bite site or bleed spontaneously from the mouth or old wounds. Unchecked bleeding can cause shock or even death.
• Nervous system effects: The effect on the nervous system can be experienced locally close to the bite area or affect the nervous system directly. Venom from elapids and sea snakes can affect the nervous system directly. Cobra (Naja and other genera) and mamba (Dendroaspis) venom can act particularly quickly by stopping the breathing muscles, resulting in death without treatment. Initially, victims may have vision problems, speaking and breathing trouble, and numbness close to or distant to the bite site.
• Muscle death: Venom from Russell's vipers (Daboia russellii), sea snakes, and some Australian elapids can directly cause muscle death in multiple areas of the body. There can be a local effect of muscle death (necrosis), or distant muscle involvement (rhabdomyolysis). The debris from dead muscle cells can clog the kidneys, which try to filter out the proteins. This can lead to kidney failure.
• Eyes: Spitting cobras and ringhals (cobralike snakes from Africa) can actually eject their venom quite accurately into the eyes of their victims, resulting in direct eye pain and damage.

Spitting cobra bite. Many elapid bites result in little local swelling, but the spitting cobras are known for the amount of swelling and tissue damage they can cause.

Western diamondback rattlesnake (Crotalus atrox) bite. Rattlesnake bites can cause severe swelling, pain, and permanent tissue damage.

Copperhead (Agkistrodon contortrix) bite. These bites usually result in local pain and swelling but usually have less tissue loss than rattlesnake bites.

Timber rattlesnake (Crotalus horridus) bite. Pit viper bites can cause a leakage of blood cells out of the blood vessels, even on parts of the body away from the bite site. Note the significant bruising of the upper forearm and arm.

Two major families of snakes account for most venomous snakes dangerous to humans.

1. The elapid family includes:

• the cobras (Naja and other genera) of Asia and Africa;
• the mambas (Dendroaspis) of Africa; the kraits (Bungarus) of Asia;
• the coral snakes (Micrurus) of the Americas; and the Australian elapids, which include the coastal taipan (Oxyuranus scutellatus),
• tiger snakes (Notechis), king brown snake (Pseudechis australis), and
• death adders (Acanthophis).
• Highly venomous sea snakes are closely related to the Australian elapids.

Snakes from the elapid family

King cobra (Ophiophagus hannah), a dangerous Asian elapid and the longest of the venomous snakes at around 4 m (13 ft).

Black mamba (Dendraspis polylepis), an extremely fast, large, and dangerous African elapid.

Coral snake (Micrurus fulvius), a shy American elapid that accounts for only about 1% of venomous snakebites in the United States. Recognize it by this catchphrase: "Red on yellow, kill a fellow."

Milk snake (Lampropeltis triangulum), a harmless mimic of the coral snake. "Red on black, venom lack," although this old saying becomes unreliable south of the United States.

2. The viper family includes:

• the rattlesnakes (Crotalus) (Western diamondback rattlesnake and timber rattlesnake), moccasins (Agkistrodon), and lance-headed vipers (Bothrops) of the Americas;
• the saw-scaled vipers (Echis) of Asia and Africa;
• the Russell's viper (Daboia russellii) of Asia; and
• the puff adder (Bitis arietans) and Gaboon viper (Bitis gabonica) of Africa.

Snakes from the viper family

Western diamondback rattlesnake (Crotalus atrox), an American pit viper, with rattle vibrating. This is one of the most dangerous snakes of North America.

Timber rattlesnake (Crotalus horridus), American pit viper, might get caught yawning after a big meal.

Cottonmouth or water moccasin (Agkistrodon piscivorous), American pit viper usually found in or near water.

Northern copperhead (Agkistrodon contortrix), an American pit viper. Bites by this species tend to be less severe than rattlesnake or water moccasin bites but still require urgent medical attention.

Most species of the most widely distributed and diverse snake family, the Colubrids, lack venom that is dangerous to humans. Some species, however, including the boomslang (Dispholidus typus), twig snakes (Thelotornis), the Japanese garter snake (Rhabdophis tigrinus), and brown tree snake (Boiga irregularis), can be dangerous. Other members of this family, including American garter snakes, kingsnakes, rat snakes, and racers, are harmless to humans.

Diagnosis of snakebite is made based on the history of the event. Identification or description of the snake can be helpful in developing a treatment plan, as not all snakes are venomous, and different kinds of antivenom exist for different species of snakes that are venomous. The doctor also looks for evidence of fang marks or local trauma in the area of the bite. Pain and swelling accompany many snakebites, venomous or not.

• The doctor treats breathing problems, shock, and/or immediately life-threatening injuries even before a full workup is complete.
• The wound will be examined and cleaned.
• If a patient has symptoms, the doctor will likely send blood and urine samples to the laboratory to look for evidence of bleeding, problems in the blood clotting system, kidney problems, or muscle death. These problems may not be initially apparent but can have dire consequences if missed.
• The patient is monitored to look for worsening symptoms at the wound site, or worsening systemic symptoms in the breathing or cardiovascular systems.
• A rare complication in very swollen limbs is compartment syndrome. Limbs are divided into compartments of muscles, blood vessels, and nerves. Severe swelling can cut off the blood circulation to a compartment. When the circulation is cut off, the patient usually has severe pain and numbness. Later, the limb may get white and cold. If not treated in time, the limb may need to be amputated.

Any snakebite victim should go to a hospital emergency department. Identification of the snake as venomous or nonvenomous should not be used as criteria whether to seek medical care. If someone can identify the type of snake, a call to the emergency department will help the staff prepare for quick treatment with antivenin, if needed.

• A bite from a nonvenomous snake requires proper wound care. The patient needs a tetanus booster if he or she has not had one within 5 years.
• Wash the wound with large amounts of soap and water. Inspect the wound for broken teeth or dirt.
• Prevent a second bite or a second victim. Do not try to catch the snake as this can lead to additional victims or bites. Snakes can continue to bite and inject venom with successive bites until they run out of venom.
• Identify or be able to describe the snake, but only if it can be done without significant risk for a second bite or a second victim.
• Safely and rapidly transport the victim to an emergency medical facility.
• Individuals should provide emergency medical care within the limits of their training.
  • Remove constricting items on the victim, such as rings or other jewelry, which could cut off blood flow if the bite area swells.
  • If a person has been bitten by a dangerous elapid (for example, sea krait [a type of sea snake], or black and yellow sea snake) and has no major local wound effects, apply a pressure immobilizer. This technique is mainly used for Australian elapids or sea snakes. Wrap a bandage at the bite site and up the extremity with a pressure at which you would wrap a sprained ankle. Then immobilize the extremity with a splint, with the same precautions concerning limiting blood flow. This technique may help prevent life-threatening systemic effects of venom, but may also worsen local damage at the wound site if significant symptoms are present there.
  • While applying mechanical suction (such as with a Sawyer Extractor) has been recommended by many authorities in the past, it is highly unlikely that it will remove any significant amount of venom, and it is possible that suction could actually increase local tissue damage. This technique is, in general, no longer recommended but is still listed as a treatment technique in many medical publications. If you decide to try this technique, follow the instructions carefully.
• The two guiding principles for care often conflict during evacuation from remote areas.
  • First, the victim should get to an emergency care facility as quickly as possible, because antivenin (medicine to counteract the poisonous effects of the snake's venom) could be life-saving.
  • Second, the affected limb should be used as little as possible to delay absorption and circulation of the venom.

A number of old first aid techniques have fallen out of favor. Medical research supports the following warnings:

• Do NOT cut and suck. Cutting into the bite site can damage underlying organs, increase the risk of infection, and sucking on the bite site does not result in venom removal.
• Do NOT use ice. Ice does not deactivate the venom and can cause frostbite.
• Do NOT use electric shocks. The shocks are not effective and could cause burns or electrical problems to the heart.
• Do NOT use alcohol. Alcohol may deaden the pain, but it also makes the local blood vessels bigger, which can increase venom absorption.
• Do NOT use tourniquets or constriction bands. These have not been proven effective, may cause increased tissue damage, and could cost the victim a limb.

The doctor treats life-threatening conditions first. A victim with difficulty breathing may need a tube placed in his or her throat and a ventilator machine used to help with breathing. People who are in shock may require intravenous fluids and possibly other medicines to maintain blood flow to vital organs.

• If indicated and available for the specific type of snake, the doctor will consider giving antivenin to victims with significant symptoms. This therapy can be life-saving or limb saving. Giving an antivenin is a difficult decision as the antivenin can have significant side effects including causing allergic reactions or even anaphylactic shock, a life-threatening type of shock requiring immediate medical treatment with epinephrine and other medications. However, antivenin treatment is still the treatment of choice, but the doctor and patient should be aware of the risks.
• Antivenin can also cause serum sickness within 5 to 10 days of therapy. Serum sickness causes fevers, joint aches, itching, swollen lymph nodes, and fatigue, but it is not life-threatening.
• Even victims without significant symptoms need to be monitored for several hours, and some people need to be admitted to the hospital for overnight observation.
• The doctor cleans the wound and looks for broken fangs or dirt. A tetanus shot is required if the patient has not had one within 5 years. Some wounds may require antibiotics to prevent infection.
• The emergency medicine doctor may need to consult a surgeon if there is evidence of compartment syndrome. Regardless, most clinicians suggest an early consult of a surgeon to help monitor the patient in case compartment syndrome develops. If treatment with limb elevation and medicines fails, the surgeon may need to cut through the skin into the affected compartment, a procedure called a fasciotomy. This procedure can relieve the increased limb swelling and pressure, potentially saving the arm or leg.

A snakebite victim who has been released from the hospital should return to medical care immediately if he or she develops any worsening symptoms, especially trouble breathing, change in mental status, evidence of bleeding, worsening pain, or worsening swelling.

Someone who has received antivenin treatment for snakebite should return to medical care if any signs of serum sickness develop (fever, muscle or joint aches or swelling, hives). This complication usually occurs within 5 to 10 days after administration of antivenin.

For the first few weeks, a snakebite victim (particularly a rattlesnake bite) should warn his or her physician of the incident before any routine or emergency surgery. Some snake venoms can cause difficulty in blood clotting for a week or more after the bite.

Although the vast majority of victims bitten by venomous snakes in the United States do very well, predicting the prognosis in any individual case can be difficult. Despite the fact that as many as 8000 bites by venomous snakes may occur, very few deaths (in the United States) result from them, and most of these fatal cases do not seek care for one reason or another. It is rare for someone to die before they are able to reach medical care in the United States. The majority of snakes are not poisonous if they bite. If a person is bitten by a nonvenomous snake, they will recover. The possible complications of a nonvenomous bite include a retained tooth in the puncture wounds or wound infection (including tetanus). Snakes do not carry or transmit rabies.

A victim who is very young, old, or has other diseases may not tolerate the same amount of venom as well as a healthy adult. The availability of emergency medical care and, most importantly, antivenin can affect how well the victim recovers.

Serious venom effects can be delayed for hours. A victim who initially appears well could still become quite sick. All victims possibly bitten by a venomous snake should seek medical care without delay. The faster the patient is treated appropriately for a poisonous snakebite, the better the prognosis.

The snake is almost always more scared of the human than the human is of the snake, it is assumed because allowing the snake to escape prevents most bites. However, most snakes will try to bite if cornered or frightened.

• Do not attempt to handle, capture, or tease venomous snakes or snakes of unknown identity. In the U.S., a large percentage of snakebites occur when the victim tries to capture a snake or handles a snake carelessly.
• Snakebites are often associated with alcohol use. Alcohol intake can weaken a person's inhibitions, making it more likely that they might attempt to pick up a snake. Alcohol also decreases coordination, increasing the probability of a mishap.
• Individuals can help prevent significant bites by wearing boots while hiking or working where snakes may live. Long pants can reduce the severity of a bite. When in snake country (for example, when gathering firewood or collecting berries), be cautious where you place your hands and feet, and never walk barefooted.
• If your occupation or hobby exposes you to dangerous snakes regularly, preplanning before a potential bite may prove life-saving. Since not every doctor is familiar with snakebites and not every hospital has or knows how to obtain antivenin, providing information regarding the type of snake, type of venom, and the procurement and use of antivenom can help the medical staff treat the victim.
• Local poison control centers will usually have a listing of the local facilities with antivenins. The contact number for the National Poison Control Center (1-800-222-1222) can help direct anyone in the U.S. to local facilities with appropriate antivenin stock.