PODCAST: Thin Air, High Stakes: Altitude Medicine

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Dr. Jonathan Thompson dives into the fascinating world of high-altitude medicine, explaining how hypoxia affects the body and lead to conditions like acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). He highlights how hypoxia is a universal concept relevant to emergency and critical care medicine, and that understanding altitude illness can improve care for patients, whether you practice on a mountain or not!

Bio: Dr. Jonathan Thompson is a former Green Beret in the U.S. Army Special Forces and former U.S. Army Special Operations Mountaineering Instructor that taught in Colorado, Alaska, and Wyoming. He completed a Masters in Physiology at the University of Michigan with a thesis on nitrate supplementation in the prevention and treatment of acute high-altitude illnesses. He is an annual, returning guest lecturer (2020-present) at the University of Michigan’s Department of Physiology instructing undergraduate and graduate students on high-altitude physiology, pathophysiology of acute altitude illnesses, and relevant treatments.

Guest: Jonathan Thompson, MD, MS; Host: Kim Bambach, MD; Audio editor: Nick Roesel

Key Learning Points:

1. The unifying concept: hypoxia
   • Decreased oxygen delivery impairs cellular metabolism and underlies all altitude illness.
2. Risk of altitude illnesses begins around 5,000 feet
   • Risk increases with rapid ascent and poor acclimatization. The classic setup is flying in and ascending quickly.
3. Physiologic response to altitude
   • Hypoxia triggers the hypoxic ventilatory response → ↑ respiratory rate and tidal volume
   • ↑ sympathetic activity → ↑ heart rate and blood pressure
   • Respiratory alkalosis from hyperventilation → renal compensation → bicarbonate excretion → diuresis
   • Over weeks, erythropoietin → ↑ red blood cell mass
4. Altitude Illness Spectrum
   • Acute Mountain Sickness (AMS): Symptoms include headache, nausea, fatigue, and insomnia. This is usually mild but a warning sign.
   • High Altitude Cerebral Edema (HACE): Characterized by neurologic dysfunction, such as ataxia and altered mental status. HACE can be life-threatening.
   • High Altitude Pulmonary Edema (HAPE): A form of non-cardiogenic pulmonary edema. Symptoms include dyspnea at rest, cough, pink frothy sputum. HAPE is the leading cause of death.
5. Treatment
   • Descent is the definitive treatment. Give oxygen if available (but it’s usually not in austere environments).
   • Give Acetazolamide for AMS and HACE (both prevention and treatment)
   • Give Dexamethasone for HACE (remember “HACE is AMS on steroids!”).
   • Give Nifedipine for HAPE.

The Bottom Line:

The best treatment is descent, and everything else is a bridge. When you’re out adventuring, don’t forget to go slow to acclimatize!