Category Archives: Altitude

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/

A novel prevention for acute mountain sickness

Every now and then someone thinks outside the box and causes a change in medical care. This is one of those things. I was alerted to this letter to the editor by the always excellent R&R in the Fast Lane, and when I went to the original source, I was astounded. Not many people would consider inducing pneumoperitoneum as a treatment for anything.

The letter is published almost like an abstract, and does a good job of explaining the problems that people run into when they have to go to high altitudes on short notice, such as rescuers of natural disaster victims like the one recently experienced in Nepal. And while I agree with them that there may not be time for people to go through any of the the classically used acclimation methods, I’m not sure that we should extrapolate the data that says injecting 20mL/kg of oxygen under skin can reduce the symptoms of AMS. Notwithstanding the fact that I cannot get that article to even see what they were talking about, this letter at least mentions that subcutaneous injection wouldn’t be able to hold enough oxygen. How does it hold 20mL/kg to begin with?

So of course the next logical step for a viable container is the peritoneum. They even go to great steps to mention how to create said pneumoperitoneum, and how to make sure that you don’t create too much pressure in the abdominal cavity. What they don’t explain is how there’s a place that is too remote to have oxygen tanks, but is able to use trocars to inject oxygen into the peritoneum AND be able to measure the pressure of said abdominal cavity. So, while this may in theory work, there are easier, much less invasive methods of carrying extra oxygen up the mountain. Why take it out of the bottle to begin with?

There’s a fair amount of theory about the benefits of this, including increased airway resistance, and decrease in free radicals. I don’t buy it, because you get more free radicals with hyperoxemia, which is what they’re advocating to begin with. And I’m not sure increased airway resistance would be all the beneficial either. Not to mention the obvious problem you have with expansion of gas as you decrease atmospheric pressure. I’m sure people would love the feeling of their abdomen doubling in size. So while they end with:

In summary, artificial pneumoperitoneum should be considered for AMS prevention in persons who must ascend to high altitude and begin work without rest and acclimation.

I say we shouldn’t consider this.

An artificial pneumoperitoneum created by injection of oxygen may prevent acute mountain sickness.
http://www.ncbi.nlm.nih.gov/pubmed/25910671