Category Archives: gear

Is there anything a SAM splint can’t do?

Deciding what to carry in your medical kit on an expedition is hard. You don’t want to leave anything out, but you can’t carry an entire hospital on your back. I mean, the wheels on the slit lamp really suck at crossing rough terrain. So you have to decide what goes and what doesn’t. Thus the reason for much of the improvisation inherent in wilderness medicine. An item that only does one job had better be the only item that can do that job, or it is extra weight.

C collars are one of those items. Now, ignoring the fact that many of them aren’t good at their job to begin with, they really aren’t good for much else. Sure, you could maybe improvise a pressure dressing out of it, but what else are you going to do? And while some of them do lay flat, they’re still pretty long and take up space that could be used for something else.

Enter the SAM splint®*. Waterproof, moldable, and able to be cut to size, it can be used pretty much anywhere on the body. And everyone has seen the picture of one being used to immobilize the cervical spine. But does it work well in that role?

Improvised C Collar in Auckland

These authors put it to the test against a Philadelphia collar using 13 EM resident “volunteers”. I’m sure they were paid well for their time. Using a goniometer they measured maximal extension, rotation, and lateral flexion. They found that no statistically significant difference in any one measurement, but looking at the results the SAM does appear to allow slightly more rotation and extension, while doing a better job of limiting lateral flexion. This likely is due to the bulkiness of the SAM laterally.

While the method of measuring falls short of a radiographic gold standards, and the number of subjects is low (but powered to an 11° difference per the authors), it looks like the SAM splint, in fact, is just as good as a Philly collar at immobilizing the C spine. I am OK with it in an awake patient, but would add more reinforcement to an unconscious patient.

Comparison of a SAM Splint-Molded Cervical Collar with a Philadelphia Cervical Collar
http://www.ncbi.nlm.nih.gov/pubmed/19594206

*I’m using SAM splint to cover all the moldable splints out there, similar to how Xerox is used to cover all photocopiers. I do not receive any money from SAM Medical Products® for using their name here. You are welcome to use other splints, but this article only used the SAM.

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.