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acute mountain sickness

Etiology: acute ascent of lowlanders to > 7000 feet Physiology: 1) PiO2 decreased by 4-5 mm Hg for every 1000 feet in elevation 2) high-altitude induced hypoxia increases minute ventilation & decreased pCO2 3) hemoglobin concentration increases secondary to diuresis 4) transient increase in erythropoietin levels History: 1) travel to above 1900 meters, 6300 feet 2) history of previous acute mountain sickness Clinical manifestations: 1) symptoms occur 6-90 hours after ascent 2) fatigue, lethargy 3) insomnia or other sleep disorder - high-altitude periodic breathing is common [2] 4) headache 5) ataxia 6) nausea/vomiting 7) anorexia 8) dyspnea 9) high-altitude pulmonary edema 10) cerebral edema in severe cases 11) high-altitude retinopathy - retinal vessel leakage [6] Management: 1) return to lower elevation 2) prophylaxis a) acetazolamide 125 to 250 mg BID-TID prophylactically 1] start 1 day before ascent 2] continue for 2 days after reaching destination [3] 3] higher dose more effective, but with more risk of adverse effect [5] b) ibuprofen as effective as acetazolamide [4] 1] 600 mg every 6 hours beginning 6 hours before ascent 2] number needed to treat = 4 3) rest, hydration, oxygen 4) urgent descent to lower elevation, supplemental oxygen & a) dexamethasone for cerebral edema (also descent to lower elevation) [2] b) nifedipine, sildenafil or tadalafil for pulmonary edema 5) patient education: a) advise cardiac & elderly patients to take extra precautions; patients who are stable at sea level maynot be at high altitudes b) advise against exercise above 5000 feet until acclimation for patients with: 1] unstable angina 2] uncontrolled arrhythmias 3] poorly controlled heart failure c) advise staying < 8000 feet for patients with 1] severe heart failure 2] angina pectoris 3] valvular heart disease [3] 6) atrial fibrillation can be exacerbated at high altitudes due to hypoxia & tachycardia - consider increasing rate-control med if patients are rapidly ascending over 5000 feet [3]

General

altitude sickness

References

  1. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 764
  2. Medical Knowledge Self Assessment Program (MKSAP) 14, 16, 17, 18, 19. American College of Physicians, Philadelphia 2006, 2012, 2015, 2018, 2022.
  3. Prescriber's Letter 17(2): 2010 Moving On Up: Altitude and Your Cardiac Patients Detail-Document#: 260204 (subscription needed) http://www.prescribersletter.com
  4. Lipman GS et al. Ibuprofen prevents altitude illness: A randomized controlled trial for prevention of altitude illness with nonsteroidal anti-inflammatories. Ann Emerg Med 2012 Jun; 59:484. PMID: 22440488
  5. Low EV et al. Identifying the lowest effective dose of acetazolamide for the prophylaxis of acute mountain sickness: Systematic review and meta-analysis. BMJ 2012 Oct 18; 345:e6779 PMID: 23081689
  6. Willmann G et al Retinal Vessel Leakage at High Altitude. JAMA. 2013;309(21):2210-2212 PMID: 23736726 http://jama.jamanetwork.com/article.aspx?articleid=1693883
  7. Bartsch P, Swenson ER Clinical practice: Acute high-altitude illnesses. N Engl J Med. 2013 Jun 13;368(24):2294-302. PMID: 23758234
  8. Meier D, Collet TH, Locatelli I et al Does This Patient Have Acute Mountain Sickness? The Rational Clinical Examination Systematic Review. JAMA. 2017; 318(18):1810-1819 PMID: 29136449 https://jamanetwork.com/journals/jama/article-abstract/2662895