Monthly Archives: January 2014

So what is a wilderness fellowship?

It is a recurring story in medicine. A field of study attempts to chisel out a niche, but has trouble gaining acceptance as a discrete field. Everyone has a different answer when asked what the field is, even though people have done it for years. Almost every specialty and subspecialty has gone through the same story arc, just most of them happened in the early era of modern medicine.

Wilderness medicine is at the point in medical education where it is trying to define itself. Sure, people have practiced it for a long time, arguably since the advent of first aid. But when you try to pin down what the field encompasses, you have trouble doing just that. Sure, there are journals, and research articles specific to the field, but there is no formal accreditation body. There are wilderness fellowships, but they have historically had somewhat diverse curricula, and the oldest is only 11 years old.

This article fires a salvo towards fixing the lack of definition. The authors were a group of like-minded wilderness emergency physicians who were selected to be on a task force trying to standardize the core content for wilderness medicine fellowships. The task force itself reads like a who’s who of wilderness medicine.  They took 4 years to come up with a list of the topics and skills that would make up the minimum requirements. As a testimony to the breadth of wilderness medicine, the first draft of the list of topics was 27 pages long.

What they finally honed it down to was 4 areas that pertain to academic skills, i.e. teaching future learners, and 15 topics (with multiple subtopics each) on wilderness medicine skills and knowledge. Those topics, in general, run from mountaintops to undersea, and all flora and fauna in between. Survival, EMS, and search and rescue are also included, as they are a significant part of wilderness medicine.  Training duration has been defined as 12-24 months, and they place emphasis on experiential learning instead of classroom.

Now, this is the first step in a long journey towards ACGME accreditation. The authors acknowledge the need to for a certifying exam to be created, and getting the curriculum into ACGME format before it can be reviewed. This will likely take years, so don’t hold your breath on this happening in the near future.  It is an exciting time for anyone involved in wilderness medicine though, as now there is a an effort towards standardization of the subspecialty. There will be time to blaze your own trails after you’re done, but the minimum requirements to be a competent wilderness provider are now at least partly defined.

Core Content for Wilderness Medicine Fellowship Training of Emergency Medicine Graduates.
http://www.ncbi.nlm.nih.gov/pubmed/24438590

Stop skin testing

This post came from a question received in our simulation lab a couple of weeks ago. Mainly, there was a simulated patient with latrodectus envenomation, and there was a fair amount of discussion about skin testing prior to administration on antivenom. Now, when I say discussion, what really happened was some faculty said skin testing was recommended by the package insert and all of their prior readings, whereas the residents were simply asking “why?” Then both groups practiced their google-fu and were able to come up with abstracts to support their viewpoints.

So, yet again, it seems there might be a generational gap between evidence and practice, so I figured I would try to answer their question here. And yet, when I went to search, there haven’t been a large amount of RCTs for skin testing, which isn’t shocking for the toxicology literature.

However, there have been a few decent case series that do not show a benefit to skin testing, as well as a few case series that demonstrate the safety profile of latrodectus antivenom. Putting these together, one could logically make the case against skin testing for latrodectus antivenom. However, there have now been two case reports of deaths from latrodectus antivenom use, one in a young woman with a history of asthma who received an undiluted push dose of antivenom, and more recently a man, also with asthma, who received a diluted dose of antivenom but died after experiencing anaphylaxis. The authors feel his death was likely from PE, but it still happened secondary to antivenom.

This article from Thailand was a retrospective review of snake bites who received antivenom. Over a little more than nine years, there were a total of 254 cases, 211 of which received skin testing. Ten of these patients had positive skin tests, and received different treatment. Desensitization was used in 5, and “close observation” was used in the other 5, but they still received undiluted antivenom. There were no reactions in any of the 10 patients with positive skin tests. Conversely, 7 patients with negative skin tests had reactions to the antivenom, and two who did not receive skin testing also had reactions. So the sensitivity of skin testing in their paper is 0%, and the specificity was 96.4%. Not terribly helpful for making decisions in management.

The good news for the practicing physician is that the weight of the current evidence has led the WHO to recommend against skin testing (at least for snake antivenom) as it leads to delays in treatment and does not help in decision making.

Skin and conjunctival “hypersensitivity” tests will reveal IgE mediated Type I hypersensitivity to horse or sheep proteins. However, since the majority of early (anaphylactic) or late (serum sickness type) antivenom reactions result from direct complement activation rather than from IgE mediated hypersensitivity, these tests are not predictive. Since they may delay treatment and can in themselves be sensitising, these tests should not be used [level of evidence T].

They do have the caveat that they only recommend antivenom treatment in patients who the benefits of said treatment outweigh the risks of allergic reactions.

My personal practice is to not perform skin testing. There is a very small number of patients who I feel need antivenom that I would withhold treatment based on a positive skin test. And since preventive treatment has not been proven effective, again it would only serve to delay definitive care. If I had a patient with a known severe allergy history, I would probably pretreat them (or concurrently treat them), but I would also get epinephrine and advanced airway equipment to the bedside. The harms and costs of a single dose of steroids and antihistamines are exceedingly low, and you have less of a risk of some “expert” saying you were acting cavalier.

Low incidence of early reactions to horse-derived F(ab′)2 antivenom for snakebites in Thailand
http://www.ncbi.nlm.nih.gov/pubmed/17996842

Of note, skin testing doesn’t appear to work for drugs either, so maybe there’s no point in doing it for anything emergent. In this paper, the skin test for cephalosporins had a sensitivity of 0%, specificity of 97.5%, negative predictive value of 99.7%, and a positive predictive value of 0%. Nobody with positive skin tests reacted to the medication, and 4 people with negative tests did have immediate reactions.

Validation of the cephalosporin intradermal skin test for predicting immediate hypersensitivity: a prospective study with drug challenge.
http://www.ncbi.nlm.nih.gov/pubmed/23751142