Altitude Illness - Cerebral Syndromes Treatment & Management

  • Author: N Stuart Harris, MD, MFA, FACEP; Chief Editor: Rick Kulkarni, MD   more...
 
Updated: Apr 30, 2010
 

Prehospital Care

Management of AMS follows 3 axioms: (1) no further ascent until symptoms resolve, (2) descend to a lower altitude if no improvement occurs with medical therapy, and (3) at the first sign of HACE, descend immediately. Predicting the eventual severity from the initial clinical presentation is not possible, and patients must be watched closely for progression of illness. A small percentage (< 10%) of persons with AMS will go on to develop HACE, especially with continued ascent in the presence of AMS symptoms.

Descent to an altitude below that where symptoms started is always effective treatment but may not be practical or possible given the topography, weather, the patient's ultimate trekking or climbing goals, or group resources. Accordingly, a descent of 500-1000 m is usually sufficient.

Acetazolamide accelerates acclimatization and thus quickens resolution of the illness, but this may still require 12-24 hours; it is of limited value in HACE because of its relatively slow action. Acetazolamide can be taken episodically without fear of rebound symptoms when it is discontinued. Dexamethasone swiftly reverses symptoms (2-4 h) but does not improve acclimatization. It is the drug of choice for treating HACE and should be given early. Both agents may be used to treat AMS if the victim does not descend. Oxygen is extremely effective, but availability is often limited.

Portable hyperbaric chambers made of coated fabric (eg, Gamow bag, CERTEC, PAC) are now widely available among adventure travel groups on expeditions and in high-altitude clinics. These are all lightweight, coated fabric bags about 2 m long and 0.7 m in diameter. The patient is placed completely within the bag, which is sealed shut and inflated with a manually operated pump, pressurizing the inside to 105-220 mm Hg above ambient atmospheric pressure. Depending on the elevation of use, a physiologic (simulated) descent of up to 2000 m may be achieved within minutes. Continuous pumping is necessary to flush CO2 out of the system, unless a chemical scrubber system is used. Patients are typically treated in 1-hour increments and then are reevaluated.

Importantly, in HACE cases, these chambers should only be used as a means of acute/temporizing care (eg, to improve a patient's ability to more safely participate in their evacuation in technical terrain). They should never be considered as a replacement for actual descent.

Coca leaf tea is widely recommended in South America, on the Internet, and in the popular press as a cure for altitude illness; however, no studies support this claim. Coca leaf tea may act as a mild stimulant and improve well-being at altitude, which may be its primary effect. Garlic likewise has been advocated for prophylaxis and treatment of altitude illness. Animal studies show efficacy in preventing hypoxic pulmonary hypertension, but studies in humans are lacking and its use cannot be recommended at this time. Additional medications not shown to have any benefit include calcium channel blockers, naproxen, phenytoin, and antacids. Alcohol and other respiratory depressants should be avoided in someone with AMS due to the risk of exaggerated hypoxemia.

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Emergency Department Care

All of the symptoms of AMS improve dramatically with descent, and, by the time a patient reaches the emergency department, further treatment is rarely indicated.

Oxygen 4 L/min or to keep SaO2 above 90% should be used in patients who continue to be acutely ill with either severe AMS or HACE after descent.

Dexamethasone should be continued in symptomatic patients with HACE.

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Consultations

Ataxia due to HACE commonly persists for days to weeks after descent, but persistent mental status changes or the presence of focal neurologic deficits should prompt a complete neurologic evaluation. Brain tumors that suddenly become symptomatic at altitude, Guillain-Barré syndrome, herpes encephalitis, and cortical blindness have all been misdiagnosed as HACE.

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Contributor Information and Disclosures
Author

N Stuart Harris, MD, MFA, FACEP  Chief, Division of Wilderness Medicine, Massachusetts General Hospital (MGH) Fellowship Director, MGH Wilderness Medicine Fellowship. Attending Physician, MGH Assistant Professor in Surgery, Harvard Medical School

N Stuart Harris, MD, MFA, FACEP is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, International Society for Mountain Medicine, and Massachusetts Medical Society

Disclosure: Nothing to disclose.

Coauthor(s)

Sara W Nelson, MD  Staff Physician, Harvard Affiliated Emergency Medicine Residency, Brigham and Women's Hospital and Massachusetts General Hospital

Sara W Nelson, MD is a member of the following medical societies: American College of Emergency Physicians, Emergency Medicine Residents Association, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Specialty Editor Board

Dan Danzl, MD  Chair, Professor, Department of Emergency Medicine, University of Louisville Hospital

Dan Danzl, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, Kentucky Medical Association, Society for Academic Emergency Medicine, and Wilderness Medical Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Eddy S Lang, MDCM, CCFP(EM), CSPQ  Associate Professor, Senior Researcher, Division of Emergency Medicine, Department of Family Medicine, University of Calgary Faculty of Medicine; Assistant Professor, Department of Family Medicine, McGill University Faculty of Medicine, Canada

Eddy S Lang, MDCM, CCFP(EM), CSPQ is a member of the following medical societies: American College of Emergency Physicians, Canadian Association of Emergency Physicians, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

John D Halamka, MD, MS  Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center

John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Rick Kulkarni, MD  Attending Physician, Department of Emergency Medicine, Cambridge Health Alliance, Division of Emergency Medicine, Harvard Medical School

Rick Kulkarni, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: WebMD Salary Employment

Additional Contributors

The authors and editors of eMedicine gratefully acknowledge the contributions of previous author, Thomas E Dietz, MD, to the development and writing of this article.

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High-altitude cerebral edema (HACE). Image courtesy of Dr Peter Hackett.
A very ataxic man with high-altitude cerebral edema (HACE) at 4250 m being assisted toward the Gamow bag.
Ultrasonography - Optic nerve sheath diameter measurement. Top of field is cornea, bottom of field reveals retina, then optic nerve in lowest field. Images courtesy of Dr Peter Fagenholz et al.
Horse evacuation of nonambulatory altitude illness. Patient in the Khumbu, Nepal. Image courtesy of Dr Peter Fagenholz.
 
 
 
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