What is Evaluation and Treatment of Snake Envenomations?
Snake bites can cause severe illness or even death, especially in countries with few resources. There are over 600 types of venomous snakes across the globe, with most of them falling into the Viperidae and Elapidae families. Common names for Viperidae family members are vipers, pit vipers, and adders. You can identify them by their long, movable fangs, triangle-shaped heads, oval pupils, and small scales on their tails. Pit vipers also have a heat-sensing pit near their nostrils, which helps them detect motion and hunt prey. Cobras, coral snakes, mambas, and copperheads belong to the Elapid family. Elapids are different from Viperids because they have short fangs that can’t move, less triangle-like heads, circular pupils, and larger scales on their tails. The rest of the venomous snake species come from the Atractaspididae, Colubridae, and Hydrophidae families.
What Causes Evaluation and Treatment of Snake Envenomations?
Snake bites usually happen to people who work outdoors, like farmers and hunters, or those who are spending time outside, like tourists. When a person is bitten by a snake, the first harm is caused at the spot where the bite took place. This harm can spread and affect the whole body depending on the type of snake.
Snakes mainly use their venom to catch their food, but also to defend themselves. Some types of snakes can choose when to release their venom. This leads to “dry bites,” where the snake bites but doesn’t release any venom.
If a snake does release venom during a bite, how harmful it is depends on two things: the amount of venom released and the “median lethal dose” (or LD50) of the venom. The LD50 is the amount of venom required to kill half of the population of a certain species (in this case humans) when tested, so it’s a measure of how dangerous the venom is.
Risk Factors and Frequency for Evaluation and Treatment of Snake Envenomations
Snake bites affect an estimated 1.2 to 5.5 million people across the globe every year, resulting in up to 94,000 deaths. However, there’s a wide variation regionally. For instance, in the United States, snakebite-related deaths are rare with just 5 recorded per year. In contrast, India sees many more snake bites each year, with around 50,000 leading to death. There are two main reasons for this difference. First, areas with a high population density, poor living conditions, and a greater presence of venomous snakes have more incidents. Second, healthcare access in these regions is often limited, causing delays in reaching treatment centers and a scarce availability of antivenom, a critical medication used to treat venomous bites. Within the US, most snake bites occur in the southwest, principally from the Viperidae family of snakes. While children account for 28% of these bites, men are more likely to be bitten, making up 59% of victims.
Signs and Symptoms of Evaluation and Treatment of Snake Envenomations
When a patient is suspected of being bitten by a snake, it’s crucial to gather detailed information in order to decide the best treatment approach. This information should include when and where the bite occurred, any symptoms the patient has experienced, and any first aid that was provided at the scene. The patient’s medical history, current medications, especially blood thinners, and any allergies that may prevent them from taking anti-venom (for example, an allergy to horses) should also be noted. If possible, try to identify the type of snake involved, comparing with venomous snake data on the WHO website to check for a local antivenom.
The severity of the snakebite can be affected by several factors:
- Size of the patient (bigger patients tend to fare better)
- The body part that was bitten
- Exertion after the bite
- Depth of the bite
- Species of snake
- How soon the patient arrived at the hospital
- Whether first aid was administered at the scene
During the physical examination, there may be visible fang marks at the bite site, as well as signs of local tissue damage such as bruising, blistering, or tissue death. The patient may also show signs of muscle weakness, drooping eyelids, and paralysis of the eye muscles due to neurotoxic effects. This could escalate to facial muscle paralysis and even respiratory failure due to blockage or paralysis of the diaphragm. Significant bleeding, nosebleeds, or other spontaneous bleeding could indicate a hemotoxic effect. In some patients, there may be signs of shock due to the venom causing blood vessels to widen, low blood volume, or an allergic reaction.
The type of snake may be deduced from the physical symptoms. Bites from the Elapidae snake family tend to cause minimal local damage but provoke a neurotoxic syndrome with systemic toxicity. On the other hand, bites from the Viperid family can result in severe local damage and a hemotoxic syndrome with systemic toxicity. Systemic effects can include nausea, vomiting, abdominal pain, lethargy, muscle weakness, muscle twitching, and severe headache, and it’s crucial to recognize these symptoms promptly to start giving antivenom.
Testing for Evaluation and Treatment of Snake Envenomations
If your doctor suspects that you have been bitten or stung by a venomous creature, they will need to conduct tests to determine exactly what type of venom is affecting your body. In some situations, you might not know what kind of creature bit or stung you, but your symptoms are alarming enough for the doctor to do a comprehensive initial test. They will typically run blood tests, examine your clotting time, check your protein levels, and test your kidney function. These tests can help determine if you were bitten or stung by a creature with hemotoxin, a type of venom that can affect your blood and organs.
For suspected neurotoxin exposure, another type of venom that affects the nervous system, they will monitor your carbon dioxide levels and may even repeatedly test your arterial blood gases in order to check for respiratory issues. They will also check your neurological responses regularly to see if the venom is causing further harm.
In some specialized centers (mostly in Australia), they have developed rapid venom tests. But these tests can only confirm which type of creature bit you – a negative result doesn’t mean a creature didn’t sting or bite you. It just means that the venom from the creature suspected didn’t cause the bite or sting.
Lastly, if you have a wound from a bite or sting, your doctor will closely monitor it for swelling, blistering, and any signs of compartment syndrome. Compartment syndrome happens when pressure within a muscle compartment – a section of your body like a leg or arm – increases to dangerous levels. This can severely injure your muscles and nerves. If it’s suspected, they will measure the pressure within the muscle compartment. A reading of more than 30 mmHg suggests the early stages of compartment syndrome.
Treatment Options for Evaluation and Treatment of Snake Envenomations
Initial first aid for a snakebite should be kept to a minimum with the main aim being to get the patient to the nearest medical center as quickly as possible. If it won’t delay transport, the injured limb may be put in a splint and kept level with the heart, though opinions vary on this. It is important to remove any jewelry or tight clothing on the affected limb due to possible swelling and blood flow problems. The patient should be kept calm and advised not to make any unnecessary movements as this could accelerate venom spreading throughout their body. The application of a pressure bandage can be beneficial or harmful depending on whether the venom causes nerve damage or tissue damage.
Using a tourniquet (a tight band applied above the area of a bleeding wound to control blood flow) has been found to be more harmful than useful, so it is usually discouraged. Similarly, using venom extractors (devices designed to suck venom out of the wound) has been proven ineffective. And generally, doctors don’t recommend trying to clean the wound yourself.
A crucial part of snakebite treatment is tracking the progression of swelling. This involves marking the edge of the swelling on the skin, and monitoring the swelling’s progress at regular intervals. This is done to determine whether treatment with antivenom is necessary. Antivenom is usually administered if the swelling continues to expand beyond the bite site. The type of antivenom used depends on the species of snake that caused the bite.
In the United States, two types of antivenoms have been approved for treating bites from the Crotalidae family of venomous snakes. The first type is “Crotalidae polyvalent immune Fab,” which works against four species of Crotalids (pit vipers). The second type is “Crotalidae immune F(ab)2 Equine.” It is derived from snake venoms from both North and South America and has a longer duration of action than the first type. Pediatric patients receive the same dose as adults.
In countries like India and Australia, where there is a wider variety of venomous snakes, there are multiple types of targeted antivenoms. In places where snakebites are common, these antivenoms are stored centrally to facilitate efficient storage and distribution. It’s best to administer antivenom within four hours of the snakebite for optimal effect, and it’s given through an intravenous (IV) line. Injecting it just under the skin (subcutaneously) does not seem to improve treatment outcomes. If symptoms reappear after initial treatment, the patient may need another dose of antivenom.
Apart from antivenom, treatment also involves vital supportive care such as intubation (inserting a tube through the mouth and into the airway) for patients struggling to breathe, and IV fluids for those going into shock. Some patients may require medications to counteract the blood pressure-lowering effects of the venom. Blood transfusions may be necessary if bleeding is severe. Certain medicines can also help counteract the venom’s effects on the nervous system.
What else can Evaluation and Treatment of Snake Envenomations be?
If someone hasn’t been noticeably bitten by a snake but they’re showing signs of poison in their body, doctors need to think about other creatures that might be responsible. Depending on where the patient lives, it might be a scorpion, tick or spider bite.
Medical professionals would also have to consider Guillain-Barre (a condition affecting nerves in the body) as a possibility if the patient has weakness or numbed feeling. Tick bites can also cause these symptoms.
In cases of abnormal blood clotting, an investigation would be needed to figure out if it’s due to a genetic problem or a disease they’ve picked up. The two main conditions doctors would consider are disseminated intravascular coagulation (a condition that affects the blood’s ability to clot) or idiopathic thrombocytopenic purpura (a disorder that can lead to easy or excessive bruising and bleeding).
If there’s damage to a certain area of tissue, it might be because of an injury or it could be an infection. This could include skin infections like cellulitis or more serious ones like abscesses (collections of pus) or necrotizing fasciitis (a severe infection that destroys skin, fat, and the tissue covering the muscles).
What to expect with Evaluation and Treatment of Snake Envenomations
Most of the harm and death from snake bites come from the poison that the snake injects with the bite. People who get medical help within the first 6 hours after the bite usually have a significantly lower risk of serious health issues or death. Patients who are closely watched and given supportive care during this time generally do not experience any long-term side effects.
However, individuals who suffer from severe wounds at the bite location because of the snake’s venom could experience lasting tingling or numbness sensations, muscle damage, or in serious cases, might even need an amputation.
Possible Complications When Diagnosed with Evaluation and Treatment of Snake Envenomations
The main problems after a snakebite stem from the direct effect of the venom. The venom can cause severe local tissue damage that in some cases could need the removal of dead tissue, or in serious instances, the amputation of a limb. Similarly, there can be issues with blood clotting which result in extreme blood loss. However, this situation typically resolves within 48 hours of the bite. The venom can also interfere with nerve and muscle function, which could lead to problems with breathing if the diaphragm (the muscle that helps you breathe) is affected. Symptoms such as these usually clear up within 72 hours of the bite.
While treatments for snakebite, like antivenom (the medicine that counteracts the venom), are largely helpful, they require careful monitoring for any adverse reactions. For instance, an individual might have an extreme allergic reaction known as anaphylaxis within the first few minutes up to 2 hours of antivenom administration. When this happens, the antivenom infusion should be halted, and medicines like epinephrine and an antihistamine should be given. Additionally, patients can have a hypersensitivity reaction resulting in itchy skin, hives, nausea, and a slight decrease in blood pressure. This reaction can occur at any point during the antivenom administration and will subside after the infusion is done. Lastly, there are documented cases of serum sickness, a condition that may occur up to 2 weeks after the antivenom administration. Often compared to flu symptoms, this condition presents with a rash and possibly tiny amounts of blood in urine. An over-the-counter antihistamine and a short course of oral steroids usually help manage these symptoms pretty well.
Common issues include:
- Severe tissue damage
- Blood clotting issues leading to blood loss
- Nerve and muscle damage leading to breathing problems
- Extreme allergic reaction to antivenom treatment
- Mild allergic reaction to antivenom treatment
- Serum sickness after antivenom treatment
Preventing Evaluation and Treatment of Snake Envenomations
If you think you’ve been bitten by a snake, it’s important to get to the closest emergency center right away for a quick check-up. You should not try to explore or clean the wound yourself, and you also shouldn’t use a tourniquet (a tight band used to stop bleeding).
Try to keep calm after the snake bite and don’t move the body part that was bitten. Most snake bites, even those from venomous snakes, don’t usually cause serious body-wide illness. However, when they do, it can be very serious and even life-threatening. The emergency doctors will keep a close eye on the snake bite and any signs of worsening illness.
The decision to use an antivenom (a treatment to counteract the snake’s venom) depends on whether there are signs of severe illness because the antivenom can have side effects of its own. You may need to stay in the hospital for up to 2 days so the doctors can watch for any worsening symptoms. However, people who don’t show signs of serious illness during this time usually don’t have any long-term effects from the snake venom.
The doctors may talk to a poison control center or a medical toxicologist (a doctor who specializes in treating poisoning) to help decide whether to use antivenom, which type to use, and whether it needs to be given more than once.
