Category Archives: mountain

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
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3898916/

Are you using the heel hook? Should you?

As climbing has progressed from simple vertical faces to more complex topography of the rock wall, largely brought on by recreational bouldering, so too have the techniques. One of these is the heel hook. It’s as if the first climber said to him or herself, “hey, that’s like an extra pair of hands down there. Let’s use those!”

And so began at least the documented use of the heel hook, specifically using the back of the heel to put pressure on a hold using your hamstrings. When climbers tell you that you should be using your legs more, they generally didn’t mean this. At least not with gusto, because this paper is a case series of 17 injuries from using this technique.

Heel hook in action

Now, I know what you’re saying. Lower extremity injuries are a small subset of climbing injuries (~5 to ~13%), and most of those are from falls instead of from using the heel as a climbing implement. But this should be looked at more closely, as the authors of this paper state that nearly 2/3rds of their patients were coming for a second opinion due to initial misdiagnosis.

So what injuries do you get from this? All of the climbers in the case series state that while using the heel hook, they had sudden dorsal pain in the knee, thigh, or pelvis. Seven reported a snapping sound as if a ligament had torn. All had a noticeable limp immediately, and point tenderness on exam. With US and MRI, the authors discovered 8 strains, and 9 torn muscles or ligaments. Of note, only 2 required surgery, and the rest were treated conservatively.

Interesting enough is that 6 of the tears were in the pelvis (5 in the biceps femoris alone) in a pattern more common with soccer (football) players,. The 2 knee injuries were similar to those of martial arts injuries from a similar but different heel hook. The velocity there leads to more ACL injuries however.

Prevention is obtained (in the words of the authors) by thorough stretching and flexibility exercises, and a good warmup routine. They also note that people should not use the heel hook ambitiously, as knowing their own limits will prevent injury. They also feel that MRI is not necessarily overkill for pelvic injuries and professional climbers.

The “Heel Hook”—A Climbing-Specific Technique to Injure the Leg
http://www.wemjournal.org/article/S1080-6032(15)00467-6/pdf