All information regarding the care and treatment of suspected North American venomous snakebites was written and edited by
C. Castleman, S. Greene (MD), B. Abo (DO, Paramedic), and K. Wyatt (MS); in partnership with the National Snakebite Support group.

Western Diamondback Rattlesnake

The danger of venomous snakes in North America is (typically) nothing more than a severe case of human exaggeration and paranoia. Deaths due to snakebites are all things considered, very rare (only an average of 5 to 7 per year in the US). This irrational fear of snakes has led to many innocent and often non-venomous snakes being killed on sight. In general, snakes only attack if you disturb and startle them. North American snake bites are seldom fatal but can be extremely painful.

There are two main types of venom: neurotoxins and hemotoxins. Neurotoxins paralyze your muscles. These are very dangerous as they can paralyze your heart and respiratory muscles. Hemotoxins are used by Snakes to soften up the prey and make it easier to digest. This venom can cause serious tissue damage. Some Snakes have venom that combines both effects.

Venomous Snakebites: Signs + Symptoms

After getting to a safe location after being bitten by a suspected venomous snake, always closely examine the bite — especially if you don’t know what kind of snake it was. If there are just one or two distinct fang marks (like a vampire), there is a good chance that the snake could have been venomous. Non-venomous snakes don’t have fangs and tend to leave multiple teeth marks in the shape of a semi-circle.

First and foremost, please note that roughly 20% of all North American venomous snakebites are what are considered to be ‘dry bites’ meaning that no venom was injected. This does however mean, that roughly 80% of all suspected venomous snakebites result in envenomation. Below is a short list of signs and symptoms that one might expect to see with an envenomation.

  • Puncture marks at the bite site
  • Redness, swelling, bruising, bleeding, or blistering around the bite
  • Severe pain and tenderness at the site of the bite
  • Nausea, vomiting, or diarrhea
  • Labored breathing (in extreme cases, breathing may stop altogether)
  • Rapid heart rate, weak pulse, low blood pressure
  • Visual disturbances
  • Metallic, mint or rubber taste in the mouth
  • Increased salivation and sweating
  • Numbness or tingling around your face and/or limbs
  • Muscle twitching

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Venomous Snakebites: Field Treatment

The following treatment protocols are recommended by Dr. Spencer Greene, one of the leading toxicologists and emergency physicians in the country, as well as the National Snakebite Support group.

 

  1. Arrange to get to the hospital as quickly as possible. That may mean calling a friend or 911. Definitely call 911 for any serious symptoms. Do NOT drive yourself.
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  2. Do remove any constrictive clothing and jewelry.
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  3. Elevate the affected extremity (please see the article explaining why we elevate). Absolutely DO NOT place the affected extremity *below* heart level.
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  4. Take a picture of the snake ONLY if you can do so QUICKLY and SAFELY. It may be helpful, but is not necessary. DO NOT bring the snake to the hospital — whether dead or alive!
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  5. Do NOT do any of the following:
    •     • Don’t keep the injured extremity *below* the heart
    •     • Don’t use a tourniquet, lymphatic bandage or pressure immobilization
    •     • Don’t attempt to cut and suck venom out
    •     • Don’t use an extraction device or electrical stimulation
    •     • Don’t pack the extremity in ice or use a cold pack

     

[SOURCE]

 

 

National Snakebite Support group

Remain Calm

Easier said than done; most people get hysterical when they are bitten by snake, as they expect to die at any moment. While the truth is in fact that roughly 80–90% of all bites from venomous snakes result in an envenomation, only about 20% of all venomous snakebites in North America are dry bites where the snake bites, but does not inject any venom.

Presuming that you were in fact envenomated, getting excited will only cause the venom to spread through your body more rapidly. If you are hyperventilating, use a bag or cup your hands in front of your mouth to bring carbon dioxide levels back to normal. Settle down, you are not dead yet!

Try to identify the snake or at least note down the snake’s characteristics. This information will help medical personnel in your treatment. You do not have to kill the snake and bring it with you. This would just increase the chance of more bites. But if you already killed the snake in your panic reaction, then you might as well bring it with you.

 

Rinse the Bitten Area with Water

Closely examine the bite and check if it has actually caused venom to enter your body. The fangs of a snake leave bigger and deeper marks than its other teeth.

 

Additional Recommendations

If you have a venom suction device, there is honestly NO reason to use it, as they have been shown to be nearly 100% ineffective. Even the “best” device out there, the Sawyer Extractor, has only been scientifically proven to remove 1/1000 of the venom! If you do not have a suction device, do NOT suck out the poison with your mouth! You’re not John Wayne! Do NOT apply a tourniquet. Do NOT cut around the wound.

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Elevating a Suspected Venomous Snakebite

Why Elevate a Suspected Venomous Snakebite?

By: Dr. Spencer Greene, MD

 

Western Diamondback Rattlesnake FangsWe recommend elevation for several reasons: First, the volume of venom is so minuscule, elevation is going to have a negligible effect on systemic absorption. But, for a moment, let’s say it did increase systemic absorption.

When we give antivenin, we want to maximize the interaction between the antivenin and the venom. Therefore, we kind of want to increase systemic absorption, to make the treatment more effective. But it’s all academic, because elevation really doesn’t affect venom absorption.

What it does accomplish, however, is allow for absorption of the fluids that have accumulated around the bite site.

We know that tissue damage is seen in greater than 95% of crotalid envenomations, and for most snakebite victims, the local damage is the only manifestation of toxicity, so we really like to prevent/treat that as effectively as possible. Elevation reduces the hydrostatic pressures that contribute to tissue injury. I often see significant improvement then one hour of appropriately elevating the limb.

Elevation is so important, it’s mentioned in the very first box of the Unified Treatment Algorithm (for suspected venomous snakebites). Death following snakebite is fortunately highly unlikely. Tissue damage is going to happen, so we do what we can to minimize it as much as possible. That’s why we elevate.

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Rattlesnake Venom 101

The venom of rattlesnakes is a mixture of hemotoxins and neurotoxins, but are mostly hemotoxins. Hemotoxins target tissues and blood, causing hemorrhaging and necrosis. Their venom is really a cocktail of chemical elements.

Neurotoxins target the nervous system, some of which can cause paralysis. While each species of venomous snake has its own particular cocktail of proteins and enzymes compared to other species, there is some evidence to suggest that the relative concentration of neurotoxins to hemotoxins may vary regionally even within a given species of snake.

For instance, a significant percentage of the timber rattlesnakes south of Interstate 10 (I-10) in Florida are believed by some researchers to have a higher concentration of neurotoxic venom than do timber rattlers north of this corridor. The various proteins and enzymes in rattlesnake venom have a synergistic effect that has evolved to trigger total cardiovascular collapse of the snake’s intended prey. When a rattlesnake bites in defense, the effects are watered down due to the large size of a person compared to their prey (typically a rodent).

Some recent works by scientists have found that some forms of hemotoxic venoms are not immunogenic, meaning that they do not trigger an immune response by the victim. They slip by the immune system of the envenomated animal so no antibodies are produced to fight the toxins. This is troubling since antivenins are produced by injecting venom into a large animal, typically a horse, and later harvesting the antibodies created by the horse that can be later used to treat bite victims.

Hemotoxin venoms such as those of rattlesnakes begin to disassemble the structural components of blood vessels and tissues as soon as they are injected.  This is done by metalloproteases, which are proteases enzymes that use a metal as a catalyst in the hydrolysis of peptide bonds. Because these enzymes break down even the proteins responsible for keeping the cell walls of blood vessels intact, localized hemorrhaging results, sending blood into surrounding tissues.

The same metalloproteases also act to break down skeletal muscles. Another component of rattler toxin, phospholipases cause the death of muscle tissue by attacking their cellular membranes. Some of these phospholipases have enzymes that create holes in the muscle cell walls by breaking apart the phospholipids that hold the membranes together. Other phospholipases use as‑yet‑unidentified means of destroying muscle cells.

Polyvalent Antivenin for North American Pit Viper Bites (CroFab)
North American Coral Snake Antivenin (Wyeth® Antivenin)

There are still other enzymes contained within rattlesnake venom that cause destruction. These include hyaluronidases and serine proteases, each having its own type of destructive mechanism. Some chemical compounds from the venom travel far from the site of the bite and wreak havoc on blood vessels and skeletal muscles elsewhere in the body.

In addition to the destructive actions of the venom components themselves, some proteins trick our own immune system to fight against our own cells.  Specifically, the actions of metalloproteases and phospholipases trigger an immune response at the site of the wound. Immune cells such as leukocytes signal an increased immune response by releasing messengers such as interleukin-6.

Since the venom components are not a cohesive force, and with no bacteria to attack, the immune system instead launches an attack that adds to the destruction of our own tissues. The damage done by our own immune system is doubly troubling considering that antivenin does not help to mitigate its effects.

Studies have found that, when the immune system is shut down, necrotic effects of snake venom are greatly reduced.

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The Truth About Juvenile Snakebites

Juvenile Copperhead SnakeContrary to popular belief, the bite of a juvenile pit-viper is almost always far less serious than the bite of a larger adult rattlesnake. The notion that juvenile snakes cannot control the quantity of venom injected (referred to in the field of Herpetology as “venom metering”) is a myth that has been disproven multiple times through well-designed studies.

In any snakebite, the severity is determined by a combination of different factors: those related to the snake that just bit you, and those related to your unique biology, your medical history, and the circumstances surrounding the bite.

The outcome of a bite is determined by the aforementioned factors in addition to the speed of the treatment sought by the patient and the appropriateness of the treatment given by the medical team.

Cottonmouth (Water Moccasin) SnakeThe takeaway is that while adult pit-vipers are more likely to cause worse envenomations, a bite from a baby rattlesnake for example, is no joke and can still be life-threatening if you don’t get proper medical treatment. This is especially true in cases involving children due to their smaller masses.

Treat all snakes with respect, give them a wide berth, and appreciate them for doing an excellent job of keeping rodent populations under control. Snakes have no interest in biting humans and we are fortunate to have species of venomous snakes that give us fair warning before striking (obviously less so with Copperheads), so respect them and appreciate them from a distance.

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Curriculum Updates for Venomous Snakebites
JULY 2020

(North American) Venomous Snakebites 101

These curricula recommendations have been created with direction from Miami-Dade County Fire Rescue Venom Response Task Force protocols, and have been edited to conform to the standards set by Center for Wilderness Safety and Wilderness Medical Society in accordance with the WMS National Practice Guidelines.

Aside from the coral snake, most of the venomous snakes in North America are pit vipers (rattlesnakes, copperheads, water moccasins, etc.). The good news is that most of these use a common synthetic antivenin to treat all of them. Especially in a wilderness or remote setting (and sadly, even in many urban settings), the biggest problem is inappropriate field treatment.

For pit vipers, which have a cellular toxin, it is NOT recommended to apply a tourniquet of any kind to the area above the wound. Otherwise, the toxin will pool in the area around the wound and cause additional cellular damage.

The first priority in prehospital care is scene safety. It is essential to prevent creating additional victims. There is no need to capture or transport the snake to the hospital. Even a recently killed snake can envenomate because bite reflexes may persist for several hours.

Severe envenomation and death have resulted from bites from decapitated snakes. It is reasonable to obtain a photograph of the snake, but only if it can be done so safely and does not delay transport. Identifying the species of snake can be helpful if it expedites treatment, facilitates antivenin selection where relevant, or enables experts to tailor therapy.

Proper positioning of the affected extremity in the prehospital setting is controversial. Previously, experts recommended keeping the injured extremity below heart level to minimize the spread of the venom. However, this could exacerbate local swelling, which is almost always present in crotalid envenomation. Elevating the extremity ABOVE heart level can actually aide in reducing the swelling, and patients often report significant pain relief with elevation.

Analgesia should be provided; however, non-steroidal anti-inflammatory drugs (NSAIDs) are NOT recommended because of their potential hematologic effects, which could compound with venom-induced coagulopathies.

Juvenile Copperhead Snake
Cottonmouth (Water Moccasin) Snake
Coral Snake Rhyme (courtesy, Dr. Ben Abo)
Abnormal Colored Copperhead Snake

Some people fear that elevation can accelerate systemic absorption of the venom; however, there is no evidence demonstrating this occurs. In areas where bites are unlikely to cause significant systemic toxicity, elevation is recommended. If systemic illness is a major concern, it is reasonable to keep the affected extremity at heart level. Once the patient arrives in the hospital, however, elevation is recommended for all pit viper envenomations. Coral snake envenomations do not result in tissue damage. Place the affected extremity in whatever position the patient finds most comfortable.

Most of the interventions that had once been proposed to treat snakebites in the prehospital environment (tourniquets, ice packs, “cutting and sucking” and even electrical shock) have failed to show benefit, and have actually proven to be harmful.

Additionally, various commercially available suction devices which promise to remove venom if applied shortly after the envenomation, are NOT advised. The amount of venom they actually remove is negligible. In a number of studies, these devices removed less than 2% of the envenomation load.

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