Monthly Archives: May 2015

Necessity is the mother of tourniquet invention

A lot of wilderness medicine teaching is geared towards bringing the right tools for the circumstances, but sometimes you end up in a situation where you don’t have the best tool for the job. Thus,  quite a bit of preparing for austere environments is making improvised devices out of whatever is lying around.

This article discusses one of those macgyvered lifesaving tools. While there are many commercially available tourniquets out there, there are still times when you have to create one out of something else. As the article points out, you might simply run out of tourniquets at a mass casualty incident. When the situation arises that you have to create a tourniquet, what items should you use to make one?

The authors chose to test the band and windlass design. They mention that this was based on a paucity of non-military literature about various improvised tourniquets. The band was always cotton cloth folded into shape, and they tested 3 items common to the urban environment as windlasses. While pencils, chopsticks, and popsicle sticks might not exist in the wilderness, they’re a reasonable idea for testing. It’s not like you can ensure quality control with broken twigs.

Using a computerized above-the-knee amputation simulator, they then attempted to stop bleeding using the improvised tourniquet and one of the potential windlasses. If 1 pencil, popsicle stick, or chopstick was insufficient to stop bleeding (or broke), the test would be repeated with 2, 3, or 4 until 100% effectiveness was reached.

Granted, this study only looked at occluding arterial flow instead of venous, and had a very narrow scope of windlasses. In the end, the take-home message is as follows:

  • Popsicle sticks suck as windlasses, and you shouldn’t use them. They often broke on the first turn.
  • Pencils are better, but still pretty terrible.
  • Strangely enough, chopsticks work best of those tested.
  • 2, or better yet 3, is always better than 1 when it comes to windlasses
  • Maybe use something other than flimsy wood objects when you make an improvised windlass, such as plastic or metal
  • Use a commercial device if you can find one

Which Improvised Tourniquet Windlasses Work Well and Which Ones Won’t?
http://www.ncbi.nlm.nih.gov/pubmed/25771027

Want to repel mosquitoes?

Mosquitoes. Mozzies. Whatever name you want to use for them, they’re a nuisance to you when you’re outdoors. And even worse, if you are in certain areas, they can transmit a large number of serious diseases. So which repellent is best? While I covered botanical mosquito repellents previously, this review article examines the products most of us think of when someone mentions mozzie spray.

At 38 pages, this is no light read. It’s certainly more words on mosquitoes than I’ve ever read in one sitting. But it’s full of interesting information, both trivial and applicable. For instance, did you know that the US Army had the patent on DEET for a full 11 years before they allowed civilian use?

As detailed in the article, not only are there several species of mosquitoes, there are also several formulations of repellent, and even seemingly minor things such as local weather patterns that can affect how long any particular product will work. Something as simple as wearing dark clothing can attract biters as they are able to see you better. Carbon dioxide, lactic acid, carboxylic acids, and even sweat will also attract mosquitoes, as their olfactory receptors are keen on these smells.

Using specific search strings, the authors found 1417(!)articles between 2000 and 2012, and they further pared this down to 102 when they only included repellent efficacy on human skin. The main repellents studied were DEET, Insect Repellent 3535, Icaridin (Picaridin), and Citriodora. DEET, being the gold standard, is often what others are compared against.

So what should you use?

  • DEET 20-25%
  • IR3535 10-20%
  • Icaridin 10-20%
  • Citriodora 20-30% (cream)

If you want to repel mosquitoes, a high concentration DEET product (20-25%) has the greatest repellency against all species, and conveniently it lasts the longest. It is clearly the most effective at repelling Aedes spp. Of note, in their data, they found that going over 25% DEET doesn’t offer greater protection against Aedes spp., but it does have longer repellency against Anopheles spp. Of note, it also has the most side effects, up to and including neuro- and cardiotoxicity.

IR3535 at concentrations of 10-20% works against most mosquitoes, but puzzlingly loses some efficacy against Anopheles at higher concentrations. Icaridin is also effective at 10-20%. Using IR3535 or Icaridin is reasonable, especially if you want to wear anything that DEET can destroy, such as rayon, spandex, vinyl, plastic, or even leather. 

Citriodora (lemon scented eucalyptus extract) is useful when applied as a cream, but is ineffective when used as just the essential oil. Speaking of essential oils and other “natural repellents”, these authors actually looked at a fair amount of studies, and found that some really are effective. These include catmint oil and rosemary, among others. And to really mess with you, adding 5% vanillin to anything, synthetic or natural, makes it more effective. However, most are fairly volatile and short-lived. Sorry I couldn’t give you more ammo against certain Facebook users.

The authors also included tick (Ixodes) repellent efficacy in this article, but found the data wanting. DEET, IR3535, and Icaridin all seem effective, but it isn’t conclusive.

The efficacy of repellents against Aedes, Anopheles, Culex and Ixodes spp.-A literature review
http://www.ncbi.nlm.nih.gov/pubmed/24201040