Venomous Snakebite Management

As medical science advances, and treatment practices catch up, it is necessary sometimes to revisit old material. In 2009, BFE Labs ran an article on management of poisonous snake bite. Now, in 2011, it is time to revisit that material and update it according to current standards and recent training.
Eventually, if you spend enough time in the back country, you will meet a snake. Odds are you’ll probably meet quite a few over the years. Hopefully, those meetings will remain distanced and both you and the snake will go on your separate ways, no worse for wear. However, the risk of being bitten does exist. This article will talk about both mitigating that risk, and managing the injury in the case of a bite (specifically, in the case of envenomation by a poisonous snake)

Growing up and continuing to live, work and play in the hinterlands of New Mexico, I’ve had more than a few run ins with snakes. As a kid I encouraged “run ins” with non-venomous snakes such as bullsnakes and various racers, catching them and keeping them in a terrarium for a week or two before returning them to the wilds. However, there have also been the run ins I did nothing but discourage, those with venomous snakes, particularly rattlesnakes.
Over the years I have stepped on, kicked, almost sat or put my hand down on, been crawled over and been struck (in the boots thankfully, both times) by both Western Diamondback and Prairie Rattlers. I’ve had close calls of a less dramatic nature with most other species of rattler in the Southwest, to include Mojave and Rock rattlers. It would be easy to say that so many encounters are the product of foolish and uncautious behavior, but in this part of the world, in an outdoors/rural lifestyle, thats simply the luck that many folks have. Those who are foolish about snakes, have less fortune. For all my close encounters, I have avoided serious injury by being cautious and not acting the fool. You can do exactly the same, even in a snake rich environment.

Snakebite Prevention
The first step in surviving a snake bite is to avoid it. Don’t get bitten, and you have nothing to worry about. Avoiding snakes, and avoiding behaviors when encountering snakes that increase the likelyhood of a bite, are absolutely key.
These steps are redundant; If you are dumb and let one slip, or are forced to let one go, but you are still doing the others, you retain a better chance of not getting fucked up. A momentary lapse almost earned me an envenomation from a Diamondback that had moved onto my front porch in the night, but the leather of a high-topped boot prevented his success (Incidentally, 12 gauge #6 birdshot makes a hell of a gouge in flagstone floor).
Wearing high-top boots, ideally of thick leather, or snake-bite resistant gaiters is an excellent step in preventing envenomation, but only become truly necessary when first line precautions haven’t been taken or are impossible due to environment or situational needs. Similarly, wearing long pants, denim or similar materials, may help reduce the amount of venom delivered during a successful strike (“Denim clothing reduces venom expenditure by rattlesnakes striking defensively at model human limbs”, Herbert and Hayes, Annals of Emergency Medicine, 2009 December; 54(6): 830-6).
Of primary importance is that you use care and caution about where you are moving, where your feet are going and where your stride takes you. Particularly when moving across areas that would be likely to harbor and conceal snakes. Brush, tall grass, loose rocks, boulders, deadfall, and human debris/garbage are all prime spots for snakes. Watch for snakes across varying elevations, as they can be above, beside, or below, and don’t forget to check in water for them as well. Look ahead of yourself, and over logs, bushes and ledges before you step over them. Sometimes you won’t see a snake until you are very near, or right above, it. Use a stick to probe, or light to look into, places you cannot see before reaching within.

Do You See the Diamondback?

Be aware of potential snake-rich areas, and approach them with caution. In many areas it is simply impossible to see under or into every possible snake hide. Use tools to locate snakes, so that you can avoid them. Use a trekking pole, or long stick, to probe materials you need to walk or reach through or under. Throw rocks into brush, or rock slides or under ledges. And always, always, look and be prepared to get out of the snakes way.
When dealing with rattlesnakes you have a distinct advantage in usually receiving a warning buzz from them, often before they are seen. However, some do not buzz or will not, and some are simply difficult to hear, so it’s never safe to assume there is no snake because there is no buzz. With rattlers, it is merely an added advantage to knowing where they are and avoiding them. This can also be a problem coming from an environment where 99% of the concern is toward rattlers – It’s easy to be spoiled by having an auditory warning, and forget that many venomous snakes have no such capability. Similarly, people inexperienced with rattlers are often confused by the noise, failing to recognize it as a danger sign, or making stupid moves attempting to identify or locate the source. It is important when going into unfamiliar environments to take note of the snakes of the area and their habits as part of your environmental safety evaluations.

Can You See the Snake Now?
This rattler never buzzed or moved; Had he been disturbed by an errant foot, however, he would’ve reacted far differently.

Most people who get bitten by snakes are bitten because they did something stupid. They were unaware, failed to recognize warnings, or failed to act in an appropriate manner. It’s not hard to not be stupid with snakes. If you encounter a snake, don’t fuck with it. Leave it be, give it a wide berth, and keep on trucking. Most snakes are not aggressive, and simply want to be left alone. A snake that’s been interfered with and frightened or pissed off, however, will act aggressively. Similarly snakes in other forms of distress will behave aggressively. Do your part to not contribute to their foul mood, and you won’t have much to worry about.
Some snakes, water moccasins in particular, are aggressive and territorial. I’ve personally encountered that behavior with Mojave rattlers as well, but that’s not conclusive. Use caution, stay out of their way, and avoid contact with potentially aggressive snakes as much as possible (just like any other snake). If you, for some reason, cannot get away from an aggressive snake, kill it. Most snakes will leave you alone, but when necessary, don’t hesitate to kill one quickly (The head is your target; Shotguns work especially well. A .22 through the top of the head will work just fine, but .22 “snake shot” is snake oil, use a bullet. Cutting the head off works well too, but I prefer a long handled tool like a shovel. Use caution with dead snakes and severed heads as they can still envenomate).

Snakebite First Aid
Snakebite as used here refers to a bite and envenomation from a venomous snake. Plain, simple, non-venomous snake bite should be treated like any other simple puncture wound from a nasty, germ/bacteria riddled, object.
Treatment of vemomous snakebite in the field, absent a well supplied doctor hidden in your backpack, is largely a fallacy. Most of what can be done in the field is support and transport. In the absence of certainty, the bite should be treated as venomous and the bitten transported to the nearest medical facility, or intercept with emergency medical services.
There are various tools on the market, sold as “Snakebite Kits”, which are of no actual value. Most feature a mechanical negative-pressure device designed to “suck” the venom out of the wound. Many also feature a tourniquet, and a scalpel blade, supposedly to constrain the venom to the injured limb, and to open up the bite site for easier suction of the venom. These ideas have been widely discredited in the medical community as wastes of time at best, if not outright dangerous.
I pretty commonly hear the tourniquet and cutting methods discredited by laypeople, but there are a great many people still carrying various types of suction devices. Primary among these is the Sawyer Extractor, but others exist and are still commonly carried and, worse yet, recommended by the people carrying them. There is strong evidence that these types of tools both fail to extract a significant amount of venom (if any at all), and that they may in fact cause further damage to the tissue and vessels surrounding the bite leading to increased necrosis.
In a study reported in the February 2004 edition of Annals of Emergency Medicine (Suction for venomous snakebite: A study of “mock venom” extraction in a human model, by Alberts, et al), 8 patients were injected with simulated fangs and a mock venom marked with radioactive particles. At 3-minutes a Sawyer Extractor was then applied to the “envenomation” sites, and after fifteen minutes of suction the blood collected and analyzed for venom content. The removed fluid was found to contain less than 1% of the injected venom. The study’s authors concluded that this “suggests that suction is unlikely to be an effective treatment for reducing the total body venom burden after a venomous snakebite.”
In the same, February 2004, edition of Annals of Emergency Medicine, an editorial by Dr. Sean Bush, MD, FACEP, titled “Snakebite Suction Devices Don’t Remove Venom: They Just Suck, compared the study and its findings to previous dismissals of tourniquets and incisions across the bites. In the editorial Bush notes that, in a study he authored, increased tissue damage was associated with use of the Sawyer extractor, “The conclusion of the study was that the Extractor did not reduce swelling, but resulted in further injury in some subjects. Specifically, circular lesions identical in size and shape to the Extractor suction cups developed where the devices had been applied. These lesions subsequently necrosed, sloughed, and resulted in tissue loss that prolonged healing by weeks. Similar injuries after Extractor use have been noted in human patients.”
In short, these types of gadgets are, at best, a piss in the wind rather than panacea.

Snakebite Suction Devices and Tourniquets/Constrictor Bands are Dangerous Antiques Just as Much as Hand Forged Blood-Letting Scalpels; Most laypeople are too reliant on hearsay, word-of-mouth and memory to know this, however.

In absence of effective gadgetry, the best medicine for snake bites remains rapid patient support, and transportation to definitive care. Aside from fundamental Advanced Cardiac Life Support (ACLS) type support for the patient, and transport, there is very little that can be done in the field for snakebites. Very little, however, does not mean nothing at all.

Pressure Immobilization Technique:
There is a management method, initially thought only applicable to Elapidae family of snakes common in Australia/Asia (vs. Crotalids, pit vipers, the predominant type of poisonous snake in North America), but now considered applicable for all snake bite. Pressure Immobilization Technique (PIT), also known as the Australian Method, is the standard for field care of snakebites in Australia and Asia. The method involves wrapping the bitten extremity in compressing bandages from the bite site, to the trunk, and back again, then splinting to ensure immobility (Australian Wilderness Medical Institute guidelines for Elapid Envenomation). This prevents or at least reduces systemic spread of the venom until the bands are removed (in a clinical setting with immediately available antivenin). For elapidae, this method works exceedingly well, but has only recently seen acceptance for crotalid envenomations.
Elapidae are primarily neurotoxic in their venoms, where-as crotalids are hemotoxic. PIT, when applied to crotalid envenomations, traps the tissue damaging venom and greatly increases intracompartmental pressures, greatly increasing the tissue damage done by crotalid venom. A 2004 study by Dr. Sean Bush et al (Pressure Immobilization Delays Mortality and Increases Intracompartmental Pressure After Artificial Intramuscular Rattlesnake Envenomation in a Porcine Model, Annals of Emergency Medicine, 2004 December; 44(6): 599-604) showed that when used on Western Diamondback envenomation, PIT delayed mortality by 23%, but increased intracompartmental pressure by 179%. In discussion, the authors reference other studies showing improved mortality rates when PIT is used, but increased possibility for tissue damage. Based on their results the authors concluded, “On the basis of our findings, we cannot recommend pressure immobilization widely for viper envenomation, although specific scenarios may warrant its use. Individuals who chose to consider pressure immobilization will still have to assess risks versus benefits versus alternatives on a case-by-case basis. An informed decision should take into consideration factors such as the size and species of snake, the patient’s size, duration and location of fang contact, previous exposures to snake venom, and time and accessibility to medical care and antivenom.”
Despite this expressed reticence, use of pressure immobilization is seeing acceptance in the United States as a taught method and protocol for many emergency medical systems. The 2010 American Heart Association First Aid Guidelines state “Applying a pressure immobilization bandage with a pressure between 40 and 70mmHgi n the upper extremity and between 55 and 70mmHg in the lower extremity around the entire length of the bitten extremity is an effective and safe way to slow the dissemination of venom by slowing lymph flow […] For practical purposes pressure is sufficient if the bandage is comfortably tight and snug but allows a finger to be slipped under it. Initially it was theorized that slowing lymphatic flow by external pressure would only benefit victims bitten by snakes producing neurotoxic venom, but the effectiveness of pressure immobilization has also been demonstrated for bites by non-neurotoxic American snakes.”
The use of PIT for Crotalid envenomations is further supported by “Pilot studies of pressure-immobilization bandages for rattlesnake envenomations” by Meggs et al, Clinical Toxicology, 2010 January; 48(1): 61-3, wherein the authors state “Pigs with pressure-immobilization bandages survived for 24 h, whereas untreated pigs died at 13.68 +/- 3.42 h (p = 0.014). Surviving pigs walked on the extremity at 7 days. Potassium rose from 4.033 +/- 0.252 at baseline to 17.767 +/- 5.218 mEq/L (p < 0.0001) at time of death in untreated pigs but was normal at 24 h in treated subjects. Widespread tissue necrosis was seen in the untreated group but only local necrosis in the treatment group.”

There has been concern expressed regarding the ability of both medical professionals and laypersons to successfully apply Pressure Immobilization, even after training (Physicians and lay people are unable to apply pressure immobilization properly in a simulated snakebite scenario, Norris et al, Wilderness and Environmental Medicine 2005 Spring;16(1): 16-21). Long term retention of ability to perform PIT within the narrow range of ideal pressures was found by researchers to be low.
A 2009 Australian study on pressure immobilization training and materials (“Investigating pressure bandaging for snakebite in a simulated setting: Bandage type, training and the effect of transport” by Canale et al, Emergency Medicine Australasia, 2009; 21: 184-190), noted that performance, while still not perfect, increased when participants were given proper training, “Following training, the median pressure for the 36 participants was 65mHg (IQR 56–71 mmHg), closer to the optimal range than initial attempts. On initial bandaging, 5/36 (14%) participants achieved optimal pressure range with elasticized bandages, compared with 18/36 (50%) after training (p~0.OO2).” The study also noted that “crepe”/gauze bandages did not maintain adequate pressures over the duration of an ambulance ride, “Bandage pressures were measured during a 30 min ambulance trip and demonstrated that all crepe bandages (with or without splinting) did not maintain pressure after an initial bandage was applied at the correct tension.”
Part of such critical work invariably focuses on the performance of untrained persons applying pressure immobilization, and the lackluster performance of these untrained persons is cited as stacking up against PIT. However, many other skills suffer from extremely poor performance when undertaken by the untrained (no one would say that poor performance of CPR by someone who just read an instruction sheet was reason to disregard CPR entirely). The takeaway from these studies should be the need for training, frequent practice and re-training at regular intervals, and ensuring use of the right equipment, rather than a complete disregard for PIT.

Whether pressure immobilization is used or not, patients need to be supported in accordance with standard ACLS guidelines for Airway, Breathing and Circulation. If available, Oxygen and fluids via large bore IV’s are commonly recommended (Snake Envenomation; Mohave Rattle, Bush SP, Medscape eMedicine 2008. Snakebite, Daley and Alexander, Medscape eMedicine 2010). In absence of IV availability, the patient can be allowed to drink clear fluids, in small amounts, so long as they are not experiencing nausea or vomiting (Venomous Snakebite in Mountainous Terrain: Prevention and Management, Boyd et al, Wilderness and Environmental Medicine 2007; 18: 190-202).
Minimizing activity, and removal of jewelry and clothing potentially involved in the expected swelling of the bitten extremity is recommended when applicable. If it’s necessary to walk the victim out of a remote area, these measures may need to be delayed until a vehicle, or EMS intercept point, is reached. Whenever possible litter carry of the patient should be considered, but may not always be possible such as in self rescue.
When possible the bitten limb should be immobilized to prevent movement, and reduce pain and swelling (regardless of use of pressure immobilization technique).
The patient should be encouraged to remain calm and aided in relaxation (your behavior, as rescuer is thus extremely important), to keep their heart rate low and decrease spread of venom.
Patient and injury history will be very important to record, so that it may be provided once the patient has been delivered to medical care. Note the type and size of the snake, the time of the bite, and the patients condition as it evolves between bite and delivery to care. Continue monitoring patient vitals and mark the increase in affected tissue every fifteen minutes or so. Take note of time from bite to onset of symptoms, and of pain level at time of bite and as symptoms progress. Make note of any medications (prescription as well as over-the-counter) the patient is on or substances they may have ingested, while they remain conscious and lucid enough to recount these details. When delivering the patient to EMS or the hospital, these details will be important.

Going step by step, from the information and sources previously referenced, we can establish a suggested protocol for management of envenomation in the field as follows:

  • Contact Emergency Medical Services.
  • Identify (if possible) the snake but otherwise leave it alone.
  • Encourage calm and minimize physical movement/exertion of victim.
  • Expose the bite, removing potentially constricting clothing from the area (cut away, rather than forcing the patient to make the excess movement required to disrobe).
  • Use Pressure Immobilization when appropriate.
  • Splint the bitten extremity (even without PI).
  • Give oxygen and intravenous fluids if available.
  • Mark the extent of envenomation (visible via swelling), and continue to re-mark every 15 minutes to track progress.
  • Continue to monitor patient condition and vitals. Intubate if available and necessary to combat airway occlusion from swelling.
  • Avoid administering any therapies that lack value, or may increase risks, such as administration of aspirin or anti-inflammatory pain medications that may worsen bleeding, use of ice or electrical shock, tourniquet application, ingestion of alcohol, and home remedies. Use energy and time for medically sound patient support, and rapid transport to advanced care.

This is not comprehensive, and is not intended to replace professional medical guidance for management of snakebites, but is rather an aggregation of some of the current findings and practices on snakebite care in the field. There is a lot more reading that can, and should, be done (certainly if you are a provider), but this should give you a start and a working beginning for your needs in the field.
Be safe, and tread easy!

 

We now have Pressure Immobilization Technique kits available in our store: http://shop.bfelabs.net/product/snake-bit-pressure-immobilization-technique-kit
To our knowledge, the only kit of their kind on the US market. All the tools you need to perform PIT, and none of the dangerous bullshit!

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11 responses to “Venomous Snakebite Management”

  1. […] This post was mentioned on Twitter by Ruli Harahap, BFE Labs. BFE Labs said: Taking a look at current thinking and practices for snakebite management: http://bfelabs.com/2011/01/30/venomous-snakebite-management/ […]

  2. Caliphate from TPI says:

    Great article man! Thanks for the good links too. It’s great to see the PIT technique endorsed by the AHA.

  3. Effective Snakebite Management says:

    The PIT is not recommended for species that cause local necrosis and has been shown to be ineffective even when applied correctly. Research in India showed that even when trained, individuals could not retain the technique beyond 2 hours. Its ridiculous to recommend it for the US. Canale’s study showed that even when tied correctly it became ineffective during the ambulance ride on GOOD roads. You need to check the original research by Sutherland, it is completely flawed.

    • BFE Labs says:

      Thanks for your feedback, but I’m gonna have to bust your nuts here.
      First of all, who are you and whats your background? Let’s step away from anonymous comments, or at least commentary that doesn’t somehow reference credentials or experience. (This is the standard we try to hold for all substantial comments here, so please don’t think you’re being picked on).
      I currently hold an EMT-B certificate in a state which teaches Pressure Immobilization for all snakebites, and requires an AHA First Aid certification for medical/clinical personnel, which also teaches PIT. I make these points, to say that while I am not exactly a layman, I am speaking from the bottom of a long chain, at the top of which are people smarter and more experienced than I, who have done the work, verified the science, and made the decision that PIT is valuable. All I seek to do here is relate their work, and the recommendations made by those works and in the training I’ve had; So if PIT is ridiculous for use in the US, I’d suggest you take that up with those people. If you are an MD or other advanced practitioner, and have a significant contribution of original work to make to this field, BFE Labs would be honored for you to talk about it here.
      So, who are you? Why say you what you say? Where is the evidence that PIT is, in fact, “ridiculous”?

      Also, the Canale study referenced does not (let me repeat, does not) say that PIT loosens over time on good roads as an absolute. What is said is that PIT performed with crepe bandages (roller gauze) loosens. The correct bandaging is elastic bandages, which that study notes as being the ideal for that very reason; They do not loosen over the duration of an ambulance. I quote: “Crepe bandages initially correctly applied did not maintain desired pressure during ambulance transport on urban roads over 30 min. Elasticized bandages maintained pressure.” Note the last sentence.
      If you are referencing another study, not cited above, please provide a link to at least the summary.
      If you are referencing the study cited above, then please take the time to read what the thing says before you tell others what it says in an authoritative manner. Thank you.

  4. Rob72 says:

    I’ve long kept this as a “personal use application” living in the Midwest/Southwest. As noted (though not, perhaps, sufficiently explicitly stated) there is a very real life-saving trade-off decision.

    Dual tourniquet(or compression) application (immediately above site of envenomation and a few inches above that) will almost certainly result in gross necrosis and amputation, but equally will improve short term M&M. Long term results are anecdotal, but, lacking numerically significant populations, offer sufficient power for me on a personal level. Being diabetic, I would be unlikely to survive serious(systemic) envenomation with >2-3 hour TTT. Not a pleasant thought, but I could with a high degree of surety select how much limb I would lose, vs all-or-nothing.

    ESM’s essential argument is that it is better to choose all-or-nothing, relying on TTT and antivenin. In context of establishing a Standard of Care, I can to a limited degree understand that, but the argument is rather short sighted in denying that loss of limb (while a legal liability) has higher probability of survival than ESM’s expressed preference.

    -RAC
    ex-EMT(before we had B)
    RN

  5. Ian Wendt says:

    Rob, there’s a pretty big difference in the level of pressure used by a tourniquet or a constrictor band and the equally distributed pressure of an Aussie Wrap. Think about it more like how you’d wrap a bad ankle with an ace bandage, with the pressure being even a little bit less. This is meant to slow down lymphatic flow only, not so much the venous return and not at all arterial flow. Does it have the potential to increase necrosis? Yeah, of course. But that doesn’t mean you’re guaranteed to lose the limb. Now, with a diabetic patient, one that already has some level of circulatory compromise, the potential for gross tissue necrosis and eventual necessary amputation does become significantly greater, but that increased risk is just as prevalent as it would be without the PIT treatment.
    And I don’t even want to think about what a Sawyer extractor might do to a diabetics tissues!

    • Rob72 says:

      Understood, and you’re absolutely correct, Ian. At this time (after 38 blessed years w/o deficit) I do not have any significat problem- hair on toes still present. ( ; But, personally, my concern is the exaggerated stress on the circulatory system for someone in my shoes. With prolonged compression _and a predisposition to microvessel insufficiency_ decreased lyphatic return may result in a larger area of permanent loss _for me_.

      TTT is a huge issue, with many variables, but I’m not nearly so disposed to wandering in the far reaches as I once was.

      I probably stated my case poorly- I think PIT is the most promising pre-hosp intervention I’ve read about in quite sometime. It does need a wider popualtion, but it looks good.

      It is far less entertaining than the stun-gun, tho’…LOL!

  6. Ian Wendt says:

    Now that I can agree with!

  7. Matt McLeod says:

    Hi there,
    Just started following your blog today…yeah I’m a bit slow.

    I am a trained “first aider” (not an paramedic) here in Australia (required for my job on a coal mine) and had my annual refresher last week. I have to concur with your post, the training given Down Under is for pressure immobilisation as first response for snake bites.

    And lets be realistic….this is “first aid/first response” to prevent loss of life. You are going to need “proper” medical aid to treat a snake bite, but at least with pressure immobilisation you will give the victim a chance.

    Plenty of stuff published online via Mr Google to support your contention, good one here:
    http://www.avru.org/compendium/biogs/A000065b.htm

    Nice (and long!) post.

    Cheers from Australia
    Matt.

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