Category Archives: snake

Venom extraction kits. Seriously, just don’t.

I learned from a speaker at this years Wilderness Medical Society conference that while we as clinicians mostly know about venom extractors and why they don’t work, this hasn’t trickled down to the lay public unfortunately. All you have to do is look at their ratings on  their respective Wal-Mart pages for the Sawyer and Coghlan devices. Even more frightening, there are still some wilderness providers out there that use and recommend these devices.

Seriously though, this is one of those things in medicine that got started because it’s a good idea, made logical sense, had plenty of anecdotal evidence, and one apocryphal article that showed some success. Due to this, it was recommended by many agencies. This success was short-lived, as future research showed that it didn’t actually remove much venom, and might actually cause harm.

Based on the plurality of case reports that were all over the map, Sean Bush (of Venom ER fame), decided to study this using pig models. His was the first RCT looking at outcomes for this device. Because actual snake venom varies by each bite, they used a simulated model by injecting a standardized amount (25mg) of venom. Of note, this was because 50mg resulted in mortality, and as the pigs were used as their own control, they needed a non-lethal dose.

They of course found no difference in local tissue swelling using the extractor, and did have two instances of necrosis in the extractor group. Thus, based on their paper, no benefit, possible harm, so don’t use them.

Effects of a negative pressure venom extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation in a porcine model
http://www.ncbi.nlm.nih.gov/pubmed/11055564

This wasn’t enough for many people, as people clearly report seeing fluid in the pump after using it. It had to be doing something, so later a group from UCSF led by Michael Alberts set out to determine what actually is sucked out using the extractor. Deciding that pigs weren’t suitable for this, they instead injected a proteinaceous fluid tagged with radioactive technetium, as they would be able to measure exactly what was removed, and what was left. This was injected using a curved needle into people’s legs.

They of course succeeded in obtaining serosanguinous fluid into the pump. Even with applying the extraction device a scant 3 minutes post injection, as recommended by the instructions, when they put the counter on that fluid, they found it contained a whopping ~0.04% of the total load. Counting what was left in the body found that, on average, most people had ~98% of their venom load still present, with the maximum of 7% in one. Comically, the radioactive counts of the fluid that spontaneously “oozed” from the fluid actually measured higher than that in the extractor, with an average of 0.7%.

Thus, what it removes isn’t venom, it’s interstitial fluid.

Suction for Venomous Snakebite: A Study of “Mock Venom” Extraction in a Human Model
http://www.ncbi.nlm.nih.gov/pubmed/14747805

So really, just don’t do it. Tell everyone you can to get rid of the kit. It doesn’t help, and probably hurts, and will likely delay what medical treatments actually would do anything.
Also, feel free to review any website that sells this device. Write the editors of websites that offer medical advice (see here) and tell them to correct their errors. We have a duty to protect the public, and preventing them from buying harmful devices is included in this.

Don’t believe what you read on the internet

snakebiteWhile my tongue is planted firmly in my cheek with regards to the title of this blog post, this is a topic that is sadly all too common. Many of us in the medical field are aware of patients coming to us with medical “facts” that they have obtained on the internet that are at best misleading, and at worst incredibly dangerous.

What’s this have to do with wilderness, you say? Since wilderness medicine is often Macgyvering treatments in austere settings, it is ripe for misinformation. I’ve personally had to dispel some myths about snakebites on an online Jeep forum, as I couldn’t let someone potentially get hurt because of reading a false statement. Apparently the authors of this paper had run into a similar issue, as they wrote an article discussing the accuracy of online recommendations.

I don’t think anybody is going to be surprised that more than half of what they found out there was terrible. Now, part of that may be because they simply typed “snake bite treatment” or “snake bite first aid” in both google and yahoo, and took the first 25 sites from each search. Due to duplications and irrelevant links, they ended up with only 48 distinct web pages. They also rated them using JAMA benchmarks and the presence of the Health on Net seal.

The majority of the errors were with regards to the use of suction. I don’t know if it is because the manufacturer of the commonly available suction devices keeps trying to reinforce this behavior, or if people really just want suction to work, but 14/48 sites promoted the use of it, including sites that had Health on Net seals. At the time of the research for the paper, medlineplus.gov, fda.gov (and they call snakes poisonous!), and umm.edu (University of Maryland Medical Center) all recommended suction.  As you can see if you follow the links, they still contain those errors. Other separate site errors included recommending the use of ice, incision, or the use of electrical shock.

For the record, when bitten by a snake in North America, you want to remove constrictive items (watches, rings, etc), provide basic life support, analgesia, and hydration as needed. In addition to the above list of things NOT to do, you also don’t want to use heat, alcohol (topically or imbibed), or any other topical chemicals or herbals. And clearly, consult a medical professional in any potentially life threatening situation, and not trusting various unvetted or even apparently vetted internet sites.

Accuracy of Internet Recommendations for Prehospital Care of Venomous Snake Bites
http://www.ncbi.nlm.nih.gov/pubmed/21168781