Author Archives: Justin Hensley

Assistant Professor of Emergency Medicine at Texas A&M Health Science Center/Christus Spohn.

Acute mountain sickness is more than one syndrome

I know what you’re thinking, but I’m not just talking about HAPE and HACE here. But when acute mountain sickness affects up to half of those who ascend beyond 4500m, it’s something we really don’t know as much about as we would like. Currently the definition includes one or more of the following: headache, sleep disturbance, fatigue, and dizziness. This is all scored using the Lake Louise Scoring System. But like with GCS, you can have the same score with a completely different clinical picture. 

One major requirement for acute mountain sickness is headache though. It probably is due to vasogenic cerebral edema causing ICP elevation, as you can measure increases in optic nerve sheath diameter with increases in score.

Sleep disturbance doesn’t seem to be mediated by cerebral edema though. It appears hypoxia mediated, causing an increase in respiratory rate that then causes hypocapnia followed by a compensatory reduction in respiratory drive/rate. This periodic breathing interrupts deep sleep like obstructive sleep apnea does.

Back to the study though. They used 103 participants in the Bolivian Andes, and 189 participants climbing Mt. Kilimanjaro. They were given a survey that had 7 questions about their symptoms. After measuring the VAS by hand, it was plugged into a network analysis tool to find patterns in the data.

What they found were two different clinical syndromes that resulted in three groups of patients. The largest group was those with poor sleep and fatigue but no headache symptoms. The second smaller group had headaches, poor sleep, and fatigue. The smallest group had headache but no sleep disturbance. An interesting tidbit from the study was that there wasn’t a statistical difference between the groups in Bolivia who were randomized to placebo, antioxidants, or Viagra. None of those subjects took acetazolamide or NSAIDs.

Of note, 25 of the subjects in Bolivia were evacuated for severe AMS, but there was only one case of HAPE and no cases of HACE in the entire study. So while they all had symptoms, they perhaps weren’t as bad off as they could have been.

So what does this mean? First, almost everyone at altitude has some degree of fatigue. I like to think it is likely because they weren’t dropped off by a helicopter but instead had to climb to get there, but we have to take the data at face value. However, sleep problems and headaches were distinct from each other with only some overlap. So maybe we should either change the condition we consider AMS, or make different scoring systems for the different pathophysiologic issues. Otherwise you are possibly neglecting one disease process while treating the other. Just like with GCS, you don’t treat everyone with the same score exactly the same, but with the LLS, you might.

Network Analysis Reveals Distinct Clinical Syndromes Underlying Acute Mountain Sickness

Death by caterpillar or: Consider zebras, but don’t memorize them

I’ve given lectures on lepidoptera before.  There are between 200-3500 envenomations from lonomia spp reported every year in Brazil, but they’ve increased yearly since 2000. This is most likely from increased time in the rain forest by loggers and people recreating, but it was originally described in rubber tree tappers. The giant silkworm moth caterpillar is particularly noted, because they’re the only one reported to cause hemorrhagic syndromes and acute renal insufficiency. The envenomation syndrome is severe enough that fatalities were noted prior to creation of antivenom in Brazil.

Thankfully, this case report doesn’t involve a fatality. What it does involve is the basis of the article, namely delayed presentation. The patient was envenomated, and 24 hours later noticed bleeding from his gums and his other scratches. He waited another 3 days to present for medical treatment. Thankfully, as if it was a snake, the patient brought some caterpillars with him to be identified as Lonomia spp. Initial labs showed “blood incoagulability”, which meant that it was outside the range of normal values of prothrombin activity and clotting times. These values changed ever so slightly by day 6, and on day 8 the patient had a headache, so he was finally treated with antivenom. Thankfully the CT of his head did not show intracranial hemorrhaging. His clotting time returned to normal after antivenom, and he was discharged on day 12.

The venom appears to be a procoagulant that causes thrombin formation, leading to DIC via prothrombin and factor X activators. Due to the moth larval stage living in colonies, often the venom load in the patient is high as the injury is usually from either stepping on or puttting their hand on multiple individual caterpillars.

The antivenom is of equine origin, and is an F(ab)2 product. It’s only recommended for moderate and severe cases, such as the one mentioned in the case report. There’s not a significant amount of evidence for premedication, it is common in Brazil to give antihistamines and steroids.

Of note, while there is danger of misidentification of the condition in Brazil, where it is at least heard of if not common, the risk is even greater in the returning traveler. This is clear in this fatal case report from Canada in 2008. This doesn’t mean that lonomia envenomation should be at the top of your differential for every coagulopathy, but being aware of it may help with those future zebras that come up in travelers. And you should especially be knowledgeable about it if you practice in Brazil.

Severe Hemorrhagic Syndrome After Lonomia Caterpillar Envenomation in the Western Brazilian Amazon: How Many More Cases Are There?

Everything you know about snakebites is wrong

Well, maybe. The 6 T’s though? Testosterone, Tank, Teasing, Tequila, Tattooed, and Tanktop? Yeah, they’re not correct. The terms “legitimate” and “illegitimate” as pertaining to snakebites imply a perception of the patient that may cloud your judgement in treating.

White-lipped Pit Viper, Trimeresurus albolabris showing its fangs in Kaeng Krachan national park By: Tontan Travel

Of course, it’s only used in the pejorative for Americans generally, although maybe the Australians have a similar description for some of their snakebites. Which is interesting, because there are probably 8000 bites in the US, while there are between 1 and 5 million worldwide. Between underreporting and lack of seeking treatment these numbers are very hard to pin down. Death rates, while lower, are still nothing to ignore with between 90,000 and 125,000 deaths worldwide, but that number drops to single digits in the US. Snakebites are truly a neglected tropical disease.

These authors decided to take a nontraditional approach, namely searching Google News daily for two years,from Dec of 2011 until Dec 2013. . They had to retroactively search the rest of calendar year 2011.

National and local news outlets, as well as medical and outdoor activity websites were used, and short articles and blogs were not. Articles were assessed for date, state, victim sex, victim age, whether the bite occurred in a natural setting or in captivity, the activity of the victim at the time, whether the victim was aware of the snake before the bite, the location on the victim’s body, and whether the bite was fatal.

Unsurprisingly, the media didn’t report on a lot of them. There were only 332 victims. What does that have to do with the 6 T’s though? Namely that the breakdown differed from what would be expected. Males were more common, but only represented 67% of the bites. Tanks were only present 7.5%. Teasing? Illegitimate bites were recorded only 32 percent of the time.

Of particular curiosity is that the media reported more  total deaths than the National Poison Data System, and also had higher rates of children and adolescents and more rattlesnake bites. Of note, illegitimate bites (teasing) did result in more serious envenomations, with 8 of the ten deaths coming from that, and only 1 from stepping on a copperhead.

Sadly, the detailed analysis did not go into alcohol consumption, prevalence of tattoos (particularly ones with snakes depicted), or whether the victim was wearing a tanktop. And yes, if there are 8000 bites per year, and this article describes roughly 100 per year, perhaps the statistics do trend more towards the classic teaching. The media may portray more stories of women and children because their job is to sell newspapers and clicks, not just to report the data. But maybe we can tone down the stereotyping of snakebite victims.

An Analysis of Media-Reported Venomous Snakebites in the United States, 2011–2013