After his father-in-law arrived in the mountains, Thomas noticed later that night he seemed intoxicated despite not seeing him drink alcohol. Thomas woke up the next morning to see him reading the paper in nothing but black socks and a black tie. Thomas knew right away he wasn’t drunk, he had high altitude cerebral edema (HACE). HACE is a complication of acute mountain sickness (AMS). HACE can occur from increased pressure in the blood vessels in the brain, leading to fluid leakage and swelling (edema). This increased vessel pressure can result from the lower atmospheric pressure at high altitude1. Breathing in lower atmospheric pressure gives you less oxygen molecules per breath. Thomas estimates that EMS in Summit County see one case of HACE a year. EMS look for two hallmark signs of HACE, altered mentation and ataxia. When EMS arrive to a patient with altered mentation, they have the patient walk heel-to-toe to evaluate for ataxia. If ataxia is present, immediate descent is necessary. Rapid descent is necessary because HACE can progress rapidly. Years ago, Thomas had a patient walk into the emergency department and die within 10 minutes after arrival. Unlike high altitude pulmonary edema (HAPE), descent is the only cure for HACE.
HAPE is a more common complication of AMS. Similar to HACE, edema occurs from the high pressure inside pulmonary blood vessels pushing fluid into the lungs. The high pressure is caused by a rapid vasoconstriction response to hypoxia or low oxygen partial pressures. Luckily, HAPE has a simple treatment, oxygen. Therefore, visitors with HAPE do not need to descend to lower altitude as with HACE. HAPE is much harder to recognize than HACE and EMS is well trained in how to recognize it. Often, headache is the only symptom2. Thomas explains the HAPE protocol for EMS: In the first 20 seconds of arriving, an oxygen saturation is obtained; they obtain vitals in the next two minutes and then start high flow oxygen if the saturation is below 89%; they then listen to the lungs for signs of fluid. EMS does not treat HACE or HAPE with any medications since descent and oxygen are the effective treatments.
So, who is prone to AMS?
Unfortunately, better physical fitness does not protect you from AMS. Thomas reports that athletes with resting heart rates of 40 or below have a difficult time acclimating. Younger age also doesn’t mean easier acclimation. According to Thomas, the best age for acclimation is late 30s/early 40s. Surprisingly, previous hypoxia can help acclimation to high altitude. For example, Thomas reports that smokers have an easier time acclimating because their body is used to having the vasoconstriction response to hypoxia and breathing faster and deeper to get adequate oxygen intake.
But don’t worry, your conditioning wasn’t for nothing. A healthy diet and regular exercise prevents heart disease. Thomas estimates there are about 12 acute MI’s on the ski hill each year. These patients usually have to be transported to Denver for a stent to be placed. Exacerbation of coronary artery disease (CAD) is so common that EMS refers to altitude travel as the “altitude stress test.” This mimics a cardiac stress test in those with CAD, producing chest pain that wasn’t present at lower altitude.
Those with sickle cell disease are at risk of developing sickle cell crisis when traveling to high altitude. The lower atmospheric pressure allows the normal red blood cells to lose their integrity and become sickle. Thomas reports that EMS encounters this every couple months in patients (usually of Mediterranean descent) that present with diffuse abdominal pain with no obvious cause. This pain results from the sickle cells aggregating together and causing an occlusion. The occlusion leads to tissue hypoxia and ischemia3. These patients are transported to the hospital for treatment.
How can mountain tourists avoid AMS?
Thomas’s first recommendation is to take a staggered stop for one night at an elevation of 5,000-6,000ft, like Denver. When arriving to altitude, take it easy the first 3 days: don’t drink alcohol and do light activity. Save the long hike for the end of the trip. Also avoid substances that blunt the respiratory system like alcohol, opioids, benzodiazepines, etc. Prepare by hydrating the week before and keep drinking plenty of water while on the trip. If you have had a previous episode of AMS, you can speak to your medical provider about prophylactic medication to take before arriving at high altitude.
References
1. Hackett PH, Dietz TE. Travel Medicine. Fourth ed. Edinburgh: Elsevier; 2019. https://www-clinicalkey-com.ezproxy2.library.drexel.edu/#!/content/book/3-s2.0-B9780323546966000422?scrollTo=%23hl0000521. Accessed November 22, 2021.
2. Schafermeyer, R. W. DynaMed. Acute Altitude Illnesses. EBSCO Information Services. https://www.dynamed.com/condition/acute-altitude-illnesses. Accessed November 19, 2021.
3. Sheehan VA, Gordeuk VR, Kutlar A. Disorders of Hemoglobin Structure: Sickle Cell Anemia and Related Abnormalities. In: Kaushansky K, Prchal JT, Burns LJ, Lichtman MA, Levi M, Linch DC. eds. Williams Hematology, 10e. McGraw Hill; 2021. Accessed November 23, 2021. https://accessmedicine-mhmedical-com.ezproxy2.library.drexel.edu/content.aspx?bookid=2962§ionid=252529206
Samantha Fredrickson is currently a student in Drexel University’s Physician Assistant program.
