Monthly Archives: April 2014

Bringing wilderness to the city

Most teaching faculty work at academic programs, which typically aren’t in areas considered “wilderness” by the average layperson. Thus, teaching wilderness and austere medicine in an urban environment is necessary for those of us who can’t get our departments to pay for that month in Costa Rica. Add to the fact that many smaller departments don’t have multiple faculty willing or able to teach wilderness, as they likely have their own niche (or two).

So how do you teach wilderness medicine without the wilderness, with finite group of teachers? A pair of doctors from Dundee devised a strategy and then gave a course, so maybe we can get some insight from them. Their’s was a 2 week course, but could likely be expanded for a 4 week course without much difficulty.

Like any good course, they broke it down to the theoretical and the practical. There was emphasis on leadership models, and the usual environmental topics. The students were also tasked with evaluating objects for expedition kits. As expected, there were simulated scenarios, but in a twist not many do, they used the students themselves as both the patients and the providers. Similar to many other rotations, they have the obligatory overnight camping trip. Of note, they point out that some of the scenarios aren’t the sexy “wilderness” topics, but instead the mundane but common complaints. Knowing how to treat chest pain in the woods is much more important than treating the sting of something that lives in a finite geographic range on the other side of the planet.

Students evaluated the rotation via questionnaire. They thought it was useful (at least, the ones who filled out the surveys did), but some requested more scenarios. Comparable to my own personal experience with a wilderness rotation, their students felt the camping was the best part of the rotation. Teacher assessment of students indicated that there was improvement in clinical decision-making by the students over the course of the rotation.

In the end, this shows that simulation continues to be the mainstay of most experiential education when scenarios cannot be experienced in real life. You can make things work when they might not be the “best” option, which is the heart and soul of wilderness medicine to begin with.

Teaching wilderness and outdoor medicine in a city.
http://www.ncbi.nlm.nih.gov/pubmed/24219524

Search and Rescue: the Science

Source: René Kieselmann rmk (Bergwacht Schwarzwald e.V., BWS)When someone is lost in the woods, it often becomes the responsibility of the search and rescue teams to find them. It’s not a simple as one may think, however. The grid lines they follow need to be designed to increase the ability to find the lost person by maximizing the area able to searched while still having a better than average chance of detecting said lost person.

The grid lines are also known as Sweep Width (W), and the distance between them is simple if you have a chart. While the US Navy and US Coast Guard have well-defined values for maritime and aeronautical environments based on multiple studies, on land there are many more environment types and not enough studies have been done to create a value for each one.

That’s where this paper comes in. They attempt to describe a quick and dirty method of determining for the innumerable situations where a search and rescue operation has to take place in an area without prior calculations. The method by which they do this is fairly ingenious.

They did a total of 10 experiments in different environments at different times of the year. Each time, they measured the distance to first detection (Rd), the distance at which a located object could no longer be located (Re). They also measured a value known as the Average Maximum Detection Range (AMDR) which is an average of Rd and Re from the 8 compass points. Measurements were performed using high, medium, and low visibility objects.

What they found was interesting indeed. First, the differences between AMDR and Rd were so small that they were effectively equal. This is useful, as Rd is much easier to measure as it does not require equipment. Second, Rd had a good correlation with the W. This was true for all types of objects, but if they broke it down by high, medium, and low visibility they still had positive correlation. However, correlation wasn’t as strong for medium and low, but this might be due to sample size.

In the end, what they found was simply taking the Rd for any given object in any given environment, you could multiply by the correction factor to find W. The values they obtained were 1.773 for high visibility, 1.556 for medium, and 1.135 for low. In practice this would mean for a medium visibility object detectable at, say 20 m, then the detection index would be 31.12 m, which would how far apart the grid lines would be. The authors feel so strongly about their calculations that they recommend SAR teams to start using them, and without any evidence to the contrary, I’m inclined to agree. Sure, I’d like more studies before wholeheartedly endorsing it, but when the alternatives are basically guessing, this is probably better.

Use of the Visual Range of Detection to Estimate Effective Sweep Width for Land Search and Rescue Based On 10 Detection Experiments in North America.
http://www.ncbi.nlm.nih.gov/pubmed/24462331

So do we call them extreme infections?

It’s no secret that the “extreme athlete” industry continues to steamroll mainstream athletics. This isn’t a new trend, as evidenced by the fact that this review article is from 2007. Sorry for making everyone feel old by reminding them that CrossFit® is now 14 years old.

Anyway, extreme athletics involves taking classic sports and making them longer distances, more difficult, in austere locations, or combining multiple events into one. You also are required by law to say “extreme” in a loud, guttural voice. Due to the terrains, climates, and exotic locales involved in these sports, the extreme athlete is exposed to infections the typical (normal?) athlete isn’t. These are broken down in the article into parasitic, aquatic, tick-borne, and zoonotic infections. It’s not an exhaustive list, but is fairly extensive and thus only the surface will be scratched here.

Parasitic infections are important because diarrheal illness obtained almost everywhere except Southeast Asia is more likely to be parasitic than bacterial. Malaria gets emphasized by the article and should certainly never be missed. Certainly, fever and eosiniphilia in any returning traveller needs to be investigated further for all parasites. Other causative agents described are amebae, nematodes, and cutaneous larvae.  The last one is interesting, as athletes are more likely to have broken skin and thus be susceptible to myiasis than typical tourists. An important point is that you must be aware of the endemic parasites where the athlete is intending to travel, and understand prevention, diagnosis, and treatment.

Ingested water can also be problematic, as Giardia, Cryptosporidium, and Schistosoma are common in the surface water of many areas. Since the incubation period can be as long as 40 days, good history taking is important. Schistosoma in particular can be nasty, with pulmonary, urologic, hepatic, and even neurologic manifestations, so one does not want to miss this infection. Again, treatment is organism specific.

Aquatic infections are common as well. These can come from any break in the skin that is exposed to water, including but not limited to bites, coral injuries, and stings. These must all be irrigated copiously, but empiric antibiotics should not be started. If a secondary infection does occur, due to atypical organisms, cultures should be obtained before giving antibiotics. They mention considering delayed wound closure, but this is falling out of favor in the years since the article and I wouldn’t recommend it unless there is serious contamination and no irrigation media available.

Tick-borne diseases, such as Lyme, Rocky Mountain Spotted Fever, babesiosis, and ehrlichiosis are yet another problem the extreme athlete has to consider. Using DEET is probably your best prevention, and whole body examination after potential exposure is a must. Infection usually takes 24-48 hours of attachment, so early detection is key. Just don’t do anything silly like use gasoline, KY, or fire to remove the tick. Use forceps, and get all of it. And as has been discussed, you should prophylax with 200 mg doxycycline if you remove a tick from someone in Lyme endemic areas.

The last grouping of infections is the zoonoses, but only 2 types are mentioned. The first, leptospirosis, can be found in many farm animals and rodents. As it is shed in their urine, it can be acquired from contaminated groundwater. They mention two specific outbreaks, one Illinois triathlon where 12% of the participants (98/834) contracted the disease, and an Eco-Challenge in Malaysia where a whopping 44% of athletes (69/158) had symptoms consistent with leptospirosis. Hantaviruses, usually associated with campers, are mentioned for what is presumably completeness sake. Treatment is supportive at best, although they mention ribavirin treatment based on only one reference.

They finish the article with sound advice on insect repellent, treating drinking water, and obtaining evacuation insurance. It seems as if the authors wanted to ride the “extreme” sports wave by merely discussing tropical and subtropical diseases, as none of these are unique to extreme sports. Sadly, they were trying to be too encompassing and became overly bloated at 15 pages with references. It’s not a bad review article for someone not familiar with travel medicine.

Infectious Disease and the Extreme Sport Athlete
http://www.ncbi.nlm.nih.gov/pubmed/17826196

Beware the catfish

In case the noodling post hasn’t already made you afraid of getting in the water, here is yet another thing to worry about with regards to catfish. Catfish have multiple spines, and if you weren’t aware of that already then you’ll definitely be surprised that you can also receive a clinically significant envenomation syndrome from a sting. In fact, references show that the majority of marine and freshwater envenomations are due to catfish. Symptoms include spreading pain, muscle spasms, sweating, and wound blanching. Even if you aren’t envenomated, it still hurts like crazy.

This paper from Brazil looked at 127 catfish injuries over 8 years. Ignoring the painfully obvious error in the abstract (poison≠venom), the authors did a good job of describing catfish injuries and envenomations. I consider the error to be due to nuances in translation.

Unsurprising for an injury caused by a spine, >90% were punctures. Also not surprising, 88% of the victims were fishing when they received the injuries. The rest were during swimming or walking on the beach.

As with other marine stings, such as those caused by stingrays and jellyfish, 45-50ºC water is the agent of choice for symptom control. Strangely enough, the most common treatment those studied received was “nothing”, followed by “bathing in urine”. Suffice it to say that neither of those are very effective. Hot water was given to slightly more than 20% and was effective when given (data not shown though).

The importance of identifying foreign bodies and secondary infections is stressed as well. I also think this is the only paper I’ve ever read that leaves out the life saving significance of the tetanus vaccine after an injury. It’s actually kind of refreshing. In all a decent article about something many are unaware of.

Frequency and gravity of human envenomations caused by marine catfish (suborder siluroidei): a clinical and epidemiological study
http://www.ncbi.nlm.nih.gov/pubmed/16713609