Acute Altitude Illness in Wilderness and Prolonged-Field-Care Settings

Background. Acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) are the three acute syndromes of hypobaric hypoxia. AMS affects a majority of travelers ascending rapidly above 4000 m; the two severe syndromes are uncommon and are the leading preventable causes of death on high-altitude expeditions. Field clinicians manage all three without imaging, frequently without oxygen, and often without rapid evacuation. Objective. To provide a single protocol, each recommendation graded for strength and quality of evidence, for the prevention, recognition, field treatment, and evacuation of acute altitude illness in wilderness, expedition, and prolonged-field-care settings, and to correct statements in the field-reference edition that exceeded their cited source. Methods. The 2024 Wilderness Medical Society (WMS) guideline was the index document, and each recommendation was traced to the primary trials, reviews, and consensus statements underlying it. PubMed was searched from inception through September 5, 2026 for randomized trials, systematic reviews, consensus statements, and society guidelines in English, with trials at real elevation preferred over chamber studies. Recommendations are graded with the American College of Chest Physicians scheme used by the WMS panel; grades appearing in that guideline are transcribed from it, and statements the guideline does not make are identified as the author’s. Recommendations. Descent is the definitive treatment for all three syndromes (1A), and no drug or device substitutes for it. Graded ascent, with sleeping-elevation gains of no more than 500 m per day above 3000 m and a rest day every three to four days, is the principal preventive measure (1B), and acetazolamide 125 mg twice daily is the preferred prophylaxis, with no benefit from higher doses (1A). AMS is treated by halting ascent, analgesia, an antiemetic, and acetazolamide, with descent and dexamethasone for moderate to severe disease (1A, 1B). HACE requires immediate descent without waiting for daylight, dexamethasone 8 mg then 4 mg every 6 hours, and oxygen (1A, 1B). HAPE requires immediate descent with no patient exertion, oxygen titrated above 90%, warmth, and nifedipine extended-release only where oxygen and descent are unavailable (1A, 1C); nifedipine and phosphodiesterase-5 inhibitors are never combined. Portable chambers relieve symptoms but rebound after exit, so they enable descent rather than replace it (1B). Weight-banded pediatric dosing, pregnancy cautions, and evacuation criteria are given. Conclusion. A graded, primary-source-anchored protocol is feasible for field use. The principal limitations are the absence of trials in the circumstance that matters most, the party that cannot descend, and the extrapolation of adult dosing to children and pregnancy by consensus alone. Three statements from the field-reference edition have been corrected and one unsupported epidemiologic claim withdrawn.