If you go on a mutli-day hike or trek at high elevation (or even just visit a city at higher elevation), you might get altitude sickness. When I did the Salkantay Trek to Machu Picchu, I had to be prepared to combat altitude sickness because the highest point we hiked up to was 15,000 ft (4,570 m). Typically, altitude sickness symptoms begin around 9,000 ft (2,700 m). There are a couple of things you can do to prevent altitude sickness, and ways to treat it if you do indeed end up getting symptoms.
Before I get into the medicine, I want to clearly state that I am a medical student, and not a doctor yet. This post is meant to be informative, but make sure you take medical advice from your doctor, who will be able to treat and educate you on an individual basis.
What is Altitude Sickness (aka Acute Mountain Sickness)?
So what exactly is it, and what causes it? Altitude sickness usually manifests as headache, nausea and vomiting, or shortness of breath due to ascending to a higher altitude in a relatively short amount of time.
The Science Behind It
At a higher altitude, the partial pressure of oxygen is lower. This means that with every breath you take, you don’t breathe in as much oxygen as you normally would. The lower amount of oxygen induces a hypoxic (or low oxygen) state in your cells. Your body responds to this hypoxic state by increasing your breathing rate, or hyperventilating. As you breathe faster, you end up blowing off more CO2 than you normally would. As you rid your body of CO2, you create a respiratory alkalodic state (more basic in pH as opposed to neutral or acidic). The respiratory alkalosis, along with the compensatory changes that your body induces to increase oxygen delivery, are what causes the symptoms you have. For example, cerebral blood flow increases to increase the amount of oxygen delivery to your brain. This rapid increase in blood flow manifests as a headache.
Your body will compensate long term in a couple of different ways. First, your kidneys will excrete more bicarbonate (an alkaline/basic molecule) to bring your pH back to normal (this process can be sped up by the drug acetazolamide, but more on that later). Even more long term, you will start to produce more erythropoietin, the precursor to red blood cells. This means that you will produce more red blood cells, which makes your body more efficient at delivering oxygen. Side note: Erythropoietin is also the drug that athletes take illegally to give them a competitive edge. However, you can naturally get this same effect by training at higher altitudes, and some athletes do indeed do this!
HOW COOL IS ALL OF THAT?! (Just one of many reasons I am interested in emergency medicine and wilderness medicine.)
How to Prevent Altitude Sickness
Slowly acclimatize yourself instead of rapidly ascending to a high elevation. For example, we stayed a few days in Cusco, a city that is at around 11,000 ft (3,350 m) before starting on our hike. Ideally it would have been nice to gradually ascend to the 11,000 ft, but that is not always an option. Staying hydrated is also very important in preventing altitude sickness, so make sure to drink a lot of water before, during, (and after) the trek. Unfortunately, I got food poisoning the day before I started my trek, so staying hydrated was pretty difficult. Taking your time and pacing yourself as you hike can also help prevent it.
If you are worried about getting altitude sickness you can take acetazolamide prophylactically. I did this, and I am really glad that I did, because the dehydration from food poisoning would have made my symptoms really bad. Acetazolamide (Diamox) is a prescription drug you can get from your doctor to prevent or treat altitude sickness. It is a carbonic anhydrase inhibitor that works in the proximal tubule of the kidney (thanks to SketchyPharm, I will remember that forever). There is a whole lot of renal physiology that I am sure you don’t want to hear, but basically preventing this reaction causes bicarb to be excreted in the urine which balances out the pH in your body.
Some people are really prone to getting altitude sickness, while some people never get it at all. We don’t really know why this is or how to determine who will get altitude sickness.
How to Treat Altitude Sickness
Most of the time, altitude sickness will just go away on its own without intervention. However, you can certainly take acetazolamide to get rid of your symptoms faster. Many people bring little oxygen tanks and will take oxygen when they start to feel symptoms too.
A natural remedy that is really popular in Peru is to drink coca tea or chew on coca leaves. Coca leaves are the basic ingredient for cocaine, but they aren’t nearly potent enough (in a cup of tea) to make you high, similarly to poppy seeds with heroin. I am still unsure if it was the placebo effect or not, but I found that it did help with the headaches.
(Rare) Complications of Altitude Sickness
HAPE (High Altitude Pulmonary Edema) or HACE (High Altitude Cerebral Edema) are serious side effects of altitude sickness, but they typically only occur at extremely high altitudes (18,000+ ft) or in people who already have compromised medical states. I wouldn’t worry about this too much, but I think that it is good to be aware just in case your symptoms get worse. If you start to lose consciousness, have an extreme headache that won’t go away, or get retinal hemorrhages (bleeding inside the eye) seek help immediately.
Other than that, stay hydrated and enjoy your hike!
Comment down below to let me know what you think!