Acute high altitude Sickness (High Altitude Sickness) is the umbrella term for 3 different conditions that can happen when a person ascents to altitudes ≥2500 m.
Acute Mountain Sickness (AMS)
High-Altitude Pulmonary Edema (HAPE)
High-Altitude Cerebral Edema (HACE)
“At any point 1–5 days following ascent to altitudes ≥2500 m, individuals are at risk of developing one of 3 forms of acute altitude illness:
–acute mountain sickness, a syndrome of nonspecific symptoms including a headache, lassitude, dizziness, and nausea;
–high-altitude cerebral edema, a potentially fatal illness characterized by ataxia, decreased consciousness and characteristic changes on MRI; and
-high-altitude pulmonary edema, a noncardiogenic form of pulmonary edema resulting from excessive hypoxic pulmonary vasoconstriction which can be fatal if not recognized and treated promptly. “ERR 2017
Symptoms, signs, and DDx of High Altitude Sickness (NEJM 2013)
| Variable | AMS | HACE | HAPE |
| Symptoms | Headache is the major symptom of acute mountain sickness. Headache plus one or more of the following symptoms: Nausea, vomiting, dizziness, fatigue, and insomnia. Mild to moderate illness: A few symptoms of mild-moderate intensity with 6-12 hr after exposure to altitudes ≥ 2500 m. Severe illness: Many of the symptoms of severe intensity, usually evolving from mild-to-moderate illness. |
Moderate-to-severe symptoms of AMS. | Initial illness: Inappropriate dyspnea during exercise, reduced exercise performance, mild fever, advanced illness, orthopnea, pink frothy sputum, drowsiness. |
| Signs | None | Lassitude, truncal ataxia, altered mental status such as drowsiness or loss of consciousness, often mild fever. | Tachypnea, arterial oxygen saturation considerably below the average value for other persons in the climbing group, mild fever, signs of HACE with advanced stages. |
| DDx | Exhaustion, dehydration, hangover, migraine | TIA or Stroke, acute psychosis, intoxication (from carbon monoxide, alcohol, drugs) | PE, hyperventilation syndrome, mucus plugging. |
Treatment of High Altitude Sickness (ERR 2017)
Medications for treating High Altitude Sickness.
Descent to a lower elevation is the best treatment for all forms of acute altitude illness.
The optimal approach varies based on the type of illness, its severity, and patient factors.
AMS
Stop the ascent.
Conservative Treatment:
NSAIDs, Acetaminophen, or Aspirin for Headaches.
-Antiemetics as needed for nausea.
-Rehydrate if dehydrated. Doesn’t treat AMS per se.
Acetazolamide and dexamethasone for severe AMS symptoms or pts who don’t respond to conservative treatment.
Descent 500–1000 m or until symptoms resolve – If symptoms continue for several days despite treatment.
HACE
–Immediate descent.
–Supplemental oxygen. If descent is not feasible (due to weather, terrain, etc) place patient on supplemental oxygen via either an oxygen tank or oxygen concentrator or placed in a portable hyperbaric chamber.
–Dexamethasone by mouth, IM or IV at a dose of 8 mg initially followed by 4 mg every 6 h until the person has descended or symptoms have fully resolved.
*Acetazolamide is not recommended for HACE.
HAPE
-Option #1: No descend: Supplemental oxygen alone and close observation if health facilities available.
-Option #2: Descend: Descend to a lower elevation. If descent is not feasible, treat with supplemental oxygen or a portable hyperbaric chamber as well as a pulmonary vasodilator.
Sustained-release nifedipine is 1st-line. Phosphodiesterase-5 inhibitors are an alternative.
Many patients with HAPE are volume depleted. Avoid diuretics like Acetazolamide in HAPE.
Some studies have used Beta-agonist and CPAP.
Related articles:
Other conditions also encounter are:
High-altitude retinal hemorrhages (HARHs)
Further Reading / References
European Respiratory Review Mar 2017, 26 (143) 160096. Acute high-altitude sickness
N Engl J Med 2013;368(24):2294-2302. Acute high-altitude illnesses.