What is Crotalidae Envenomation (Pit Viper Bite)?
Pit vipers, officially known as Crotalidae, are venomous snakes found across the United States and Canada. Although pit viper bites are not common, they can cause serious health problems and even, though rarely, death. The snake’s venom contains various harmful substances that can damage cells, muscle, blood, and occasionally nerves. The severity of symptoms from a pit viper bite can vary and the full extent might not be immediately clear. It’s important that victims of pit viper bites receive a thorough health check and regular monitoring to prevent severe health complications.
What Causes Crotalidae Envenomation (Pit Viper Bite)?
In the United States, there are three types of Crotalidae snakes: the copperhead (Agkistrodon contortrix), the cottonmouth (Agkistrodon piscivorus), and various species of rattlesnakes (Crotalus and Sistrurus sp.). These types of snakes can be found all over the US, although not in Hawaii or Alaska.
These snakes can be identified by their triangular heads, eyes that are shaped like ellipses, and pits between their eyes and nostrils that they use to seek heat. Bear in mind, the types of snakes can vary from state to state and region to region. So, understanding the local geographic spread can aid in properly identifying these snakes.
Risk Factors and Frequency for Crotalidae Envenomation (Pit Viper Bite)
Every year, it is estimated that anywhere between 5,000 and 9,000 people are bitten by snakes. Men tend to be bitten more often than women, and it’s mostly people who identify as Caucasian who are affected. The group most at risk are young adults, between the ages of 20 and 40. There is also a smaller high-risk group that includes children under the age of 12.
Snakebites typically occur on the ends of our arms and legs. Bite wounds on the lower extremities are usually accidental. On the other hand, bites on the upper extremities generally result from deliberate contact with snakes. Most snakebites happen in the late spring to early fall when pit vipers are the most active. There’s also an increased likelihood of snakebites at dawn and dusk, which are peak hunting times for these reptiles.
- The majority of snakebites are from rattlesnakes and copperheads, accounting for 50 to 55% and 30 to 45% of cases, respectively.
- Bites from cottonmouth snakes are less common, contributing to only 5 to 10% of cases.
- Bites from larger snakes are usually more serious due to their larger stores of venom.
Signs and Symptoms of Crotalidae Envenomation (Pit Viper Bite)
When treating a person potentially bitten by a snake, immediate attention must be given to check if their airway is open, they can breathe, and their heart is circulating blood. Any failures in these key life-supporting functions requires urgent intervention. Bites to the head and neck area, although rare, can cause intense swelling and disrupt breathing. Any indication of breathing distress may necessitate a procedure to open the airway. Certain kinds of venom can provoke a severe allergic response or lead to serious blood loss which can destabilize vital life functions. Some types of venom can even interfere with breathing by acting on the nerves.
Assuming the patient’s critical functions are stable, other crucial information includes when the snakebite happened and where on the body it occurred. This information helps healthcare professionals track the progression of symptoms. While knowing the type of snake involved can be useful for treatment, attempting to kill or catch the snake is risky and discouraged. Instead, a picture of the snake snapped from a safe distance is often sufficient. It’s crucial to prioritize prevention of additional snakebites over identifying the snake species. Despite advice to the contrary, it’s not uncommon for victims to bring a dead snake. Worth noting is that a dead snake can still release venom and pose a risk.
- Check the patient’s airway, breathing, and circulation
- If signs of breathing distress are present, prepare for a procedure to open the airway
- Ascertain when and where the snakebite occurred
- Try to identify the snake from a safe picture or description but do not attempt to kill or capture it
The next step is to examine the patient thoroughly, starting with their heart and lungs to ensure these are functioning properly. The snakebite typically leaves two puncture scars a few centimeters apart. The practitioner should mark the outer edge of any redness or swelling around the bite to observe any potential expansion. The pulse, sensation, and mobility in the area of the snakebite also require checking. The practitioner should remove any tight jewelry or clothing that might interfere with lymph flow. Any unusual bleeding could indicate complications from the venom. A comprehensive physical examination could uncover other impacts of the venom on the body.
The majority of people bitten by pit vipers (a type of venomous snake) experience pain, swelling, bruising, and redness at the site of the bite. In some cases, the venom can damage tissues. Around 15% of snakebite victims experience whole-body symptoms, which could include vomiting, bleeding from the gums or nose, or neurological symptoms like muscle twitching, weakness or numbness, or even full-scale respiratory paralysis. Swelling of the airways and low blood pressure are rare but require immediate medical management. Doctors should also check for other symptoms like chest pain, abdominal pain, and headaches as these could indicate that the venom has triggered internal bleeding or blood clotting, or they could signify a separate health problem.
- Inspect the snakebite area
- Mark the boundaries of any redness or swelling
- Check for normal pulse, sensation, and movement near the snakebite
- Examine the entire body for other signs of venom effect
- Monitor the patient for whole-body symptoms like vomiting or unusual bleeding
While rattlesnakes are generally considered to deliver more potent venom, the severity of snakebites can’t be determined from the snake species alone. The best approach combines the patient’s history, physical examination, and lab results to guide treatment.
Testing for Crotalidae Envenomation (Pit Viper Bite)
If you’ve been bitten by a pit viper, your doctor will likely order several tests to check your blood and the functioning of your body. These include a complete blood count (CBC), tests to measure how quickly your blood clots (PTT, PT, INR), and a test to check your fibrinogen level, which also relates to your blood’s clotting ability. They particularly look for any signs of low platelet or red blood cell counts due to the bite.
In cases where a fibrinogen test is not available, a D-dimer test is a good alternative. The fibrinogen test is more specific for clotting disorders, but the D-dimer test is more sensitive and can also provide valuable information.
It’s important to mention that fibrin splint products, which are sometimes used to help with clotting, are not helpful in assessing the effect of pit viper bites.
More tests may be carried out to check for any complications arising from the snake bite. For instance, a comprehensive metabolic profile test may be done, which looks at the health of your liver and kidneys. Other tests like a urinalysis and a total creatine kinase test can help to check for muscle damage potentially caused by pit viper venom.
If you have specific symptoms like chest pain after being bitten, your doctor will order suitable tests, such as an EKG and a troponin test, to check your heart’s health.
Treatment Options for Crotalidae Envenomation (Pit Viper Bite)
Patients bitten by a pit viper should have their Tetanus updated and their wound washed with soap and water. To manage pain, opioids are recommended over NSAIDs because they may worsen blood clotting issues and platelet clustering. Getting advice from a regional poison control center can be beneficial.
Not all viper bites inject venom – about 20-25% are ‘dry’. These patients are largely symptom-free, with only slight swelling or redness, and their blood remains normal on lab tests. Mild cases of venom injection, which occur in around 35-40% of bites, also result in localized redness and swelling but no blood clotting issues. Approximately 15-20% of venomous bites lead to significant redness and swelling, potentially affecting an entire limb. Systemic symptoms like fever, chills or aches may be present but bleeding issues are usually insignificant.
The most dangerous, yet least common group (5-10%), have life-threatening blood clotting issues alongside severe localized symptoms. They may experience dangerously low blood pressure, swollen blood vessels, or neurotoxic symptoms. These severe symptoms call for immediate medical attention.
Patients with dry bites or mild venom injection should be observed for 6-8 hours and have their white blood cell count, clotting, and fibrinogen levels tested before discharge. They should be advised to return if they notice any bleeding, swelling, or a worsening of symptoms. Patients suffering more than a mild venom injection should be given anti-venom.
There are two approved anti-venoms: Crotalidae Polyvalent Immune Fab and Crotalidae Immune F(ab)2. The former, derived from four snake species and sheep immunoglobins, typically requires multiple doses. The latter, derived from two snake species and horse immunoglobins, is less immune-triggering and generally does not require multiple doses.
Patients needing anti-venom should be admitted for ongoing treatment and monitoring. Complications like severe bleeding, despite receiving the appropriate anti-venom, may need blood plasma, platelets, or packed red blood cells.
Aggressive surgical intervention is not recommended nor is providing pain relief with NSAIDs. Wound excision, the application of ice, electricity, antibiotics, tourniquets, and steroids are all discouraged as they can either cause more harm or have no proven benefits. They can be dispensed only in particular circumstances, such as a suspected allergy to the venom or anti-venom.
What else can Crotalidae Envenomation (Pit Viper Bite) be?
When someone is bitten by a venomous snake, also known as a crotalid, they usually come to the doctor because they know they’ve been bitten. But sometimes, people might suspect they’ve been bitten by a snake, even if they can’t explain why. The crucial decision doctors have to make when treating a snakebite is figuring out how much venom is in the person’s system because that will direct their treatment plan.
Bites from non-venomous snakes can also happen, but these bites don’t show any harmful signs because there is no venom involved. Other types of bites, like those from a type of insect called Hymenoptera, can cause severe pain, redness, and swelling, which can be mistaken for a snakebite if the person didn’t see what bit them. However, unlike snakebites, these types of bites usually result in a single puncture wound as opposed to snakebites that usually have two. They also cause only limited swelling and redness.
Some people with infections in their skin and soft tissues may worry that they’ve been bitten by a snake. Infections can cause redness and swelling that might be mistaken for a snakebite. But if symptoms appear several hours or a few days after an injury, it’s more likely an infection than a snakebite. Generally, it’s pretty rare for someone to be bitten by a snake without actually seeing the snake.
What to expect with Crotalidae Envenomation (Pit Viper Bite)
Between the years 2000 to 2007, rattlesnake bites resulted in zero to four deaths per every 1,000-1,300 instances annually. Copperhead snake bites cause death even less frequently, with one study reporting just one death in a five-year period. Most people who seek immediate medical attention after a snake bite are expected to survive.
Once treated, patients bitten by pit vipers can continue to experience symptoms for several weeks. The length of time these symptoms persist can vary depending on the individual and the severity of the snake bite. On average, patients may experience symptoms for two to three weeks, with possible discomfort, reduced function of the affected body part, ongoing swelling, and time away from work extending to two to four weeks. Some people may experience recurring swelling and pain for one to two months following the snake bite.
Around 5% of patients treated for snake bites return to the hospital after being discharged, due to worsening symptoms like increased swelling, redness, or signs of abnormal blood clotting. A small fraction of victims, less than 1%, experience recurrent abnormal blood clotting with bleeding. Even fewer, about 0.5%, end up with serious delayed bleeding. These cases are most commonly seen among victims of rattlesnake bites.
Possible Complications When Diagnosed with Crotalidae Envenomation (Pit Viper Bite)
Myonecrosis or rhabdomyolysis is a condition that can develop after a venom-induced muscle damage. It is especially important to monitor the patient’s kidney function and creatine kinase levels if this condition is suspected. The treatment approach for rhabdomyolysis caused by venom is the same as that for any other cause of the condition.
Compartment syndrome, though rare, can also occur as a severe consequence of pit viper bites. If a patient is suspected of having compartment syndrome, they should be given antivenom before any surgery like fasciotomy or digital dermatomy. The pressure in the affected compartments can be measured over time to assess whether the condition is getting better or worse.
Bleeding is also a possible problem, even though it is often not severe. Venom can affect both coagulation pathways and platelet aggregation, potentially causing bleeding both near the bite site and in distant areas of the body. Symptoms of distal bleeding often include gum bleeding, nosebleeds, and small, flat, red spots due to bleeding under the skin. In rare instances, bleeding can also cause a headache or abdominal pain if there is internal bleeding in the brain or in the abdominal/retroperitoneal area.
Anemia and thrombocytopenia can be treated with antivenom as the primary option. Transfusions should only be considered after antivenom administration.
Hypersensitivity reactions such as angioedema and hives are also rare. However, if these do occur, treatment should include steroids, epinephrine, and antihistamines, in addition to antivenom. If the angioedema is significant, managing the patient’s airway could be necessary.
Preventing Crotalidae Envenomation (Pit Viper Bite)
Here are some important points to remember and share about encountering pit vipers:
1. Do not try to handle or provoke pit vipers. Many snakebite cases can be prevented if people respect the space of these animals and allow them to retreat.
2. Be alert and aware in areas where pit vipers are present. These snakes can be found in many regions across the US, usually opting for less populated areas. If you’re planning to visit these places, it’s wise to research the local wildlife and plants that could be harmful.
3. Should you suffer a snakebite, seek medical help immediately. Evaluations should be made by healthcare professionals. Don’t assume a bite without immediate symptoms is harmless; serious health issues may only appear after several hours.
4. Do not try to kill or capture the snake if you are bitten. A photograph of the snake is typically enough for identification if it can be done safely.
It’s crucial to note that there are many misguided treatments for snakebites used by the general public. Despite evidence proving they are ineffective and even harmful, practices such as cutting the bite area, using a suction device, applying electricity, ice, or tourniquets continue. Therefore, it’s important to educate against such actions.
