Altitude Sickness

Educational Objectives

The goals of this program are to improve the diagnosis and management of extreme hyperthermia and high-altitude sickness. After listening to and assimilating this program, the clinician will be better able to:

1. Diagnose altitude-related illnesses based on patient presentation.

2. Recommend strategies for prevention and treatment of altitude-related illnesses.

Summary

Physiology at altitude: partial pressure of oxygen (PaO2) in alveoli — ≈100 mm Hg and ≈100% oxygen saturation at sea level; ≈60 mm Hg and 90% oxygen saturation at 10,000 ft above sea level; at PaO2 of 40 mm Hg, saturation still ≈75%; physiologic adaptations at high altitude — oxygen saturation curve shifts to left because hyperventilation causes blood to become alkalotic; capillaries release oxygen into bloodstream more readily; fraction of inspired oxygen (FiO2) — at sea level (atmospheric pressure 760 mm Hg), drops from 149 L/min at lips to 100 L/min in alveoli at sea level; at 18,000 ft (atmospheric pressure 380 mm Hg), drops from 70 L/min at lips to 40 L/min in alveoli; difference between FiO2 at lips vs alveoli smaller because hyperventilation occurs with ascent in altitude, which reduces carbon dioxide in alveoli and allows greater proportion of oxygen to reach alveoli

Altitude sickness: acute mountain sickness — may occur at altitudes ≥6000 ft in some individuals because of physiologic differences in, eg, hemoglobin (25% of people have insomnia at altitudes >8000 ft); characterized by headache, weakness, nausea, and vomiting; high-altitude cerebral edema (HACE) — vasogenic edema of brain, often preceded by acute mountain sickness; characterized by mood changes, confusion, drowsiness, obtundation, and coma; possibly life-threatening if swelling of brain extreme; use tandem walking test to assess presence of truncal ataxia; case report of HACE — 18-yr-old skier staying at base hotel located ≈9000 ft above sea level; skied on day 1 and experienced onset of fatigue and headache; skied on day 2, but ski patrol escorted him off mountain because they suspected inebriation; patient became progressively obtunded on day 3; vital signs obtained by emergency medical services — tachypnea; oxygen saturation 50%; diagnosed with high-altitude cerebral and pulmonary edema; high-altitude pulmonary edema (HAPE) — pulmonary edema caused by capillary leak in lungs; initial symptoms include cough and dyspnea; low oxygen saturation key indicator; incidence higher in children than in adults

Prevention of altitude illness: gradual ascent (eg, 1000-2000 ft per day), with inclusion of rest days to allow for adaptation to high altitude; acetazolamide (Dimox) — used to prevent altitude illness; diuretic, but mechanisms of action unclear (likely has effect on central nervous system); some individuals cannot tolerate drug (causes severe paresthesias in ≈5%); recommended dose 125 to 250 mg, although smaller doses may provide benefits

Field treatment for acute mountain sickness: mild cases — stop ascending, rest, and administer analgesics; severe cases — descend; administer oxygen and dexamethasone (4 mg 4 times/day to reduce swelling of brain); Gamow bag — pressure bag within which patient can be placed; inflated using hand pump; allows improvement in alertness of patient before descent and receipt of further treatment; flooding of lungs — descend; give inhaled albuterol through metered-dose inhaler; administer nifedipine or low-dose sildenafil (eg, Viagra, Revatio Injection)

Readings

Atha WF: Heat-related illness. Emerg Med Clin North Am. 2013 Nov;31(4):1097-108; Dixit D et al: Neuroleptic malignant syndrome associated with haloperidol use in critical care setting: should haloperidol still be considered the drug of choice for the management of delirium in the critical care setting? BMJ Case Rep. 2013 Jul 12;2013; Freeman K: Use of the Gamow Bag by EMT-basic park rangers for treatment of high-altitude pulmonary edema and high-altitude cerebral edema. Wilderness Environ Med. 2004 Fall;15(3):198-201; Kaufman KR et al: Neuroleptic malignant syndrome and serotonin syndrome in the critical care setting: case analysis. Ann Clin Psychiatry. 2006 Jul-Sep;18(3):201-4; Luks AM et al: Wilderness Medical Society practice guidelines for the prevention and treatment of acute altitude illness: 2014 update. Wilderness Environ Med. 2014 Dec;25(4 Suppl):S4-14; Moore PW et al: Physostigmine is the Antidote for Anticholinergic Syndrome. J Med Toxicol. 2015 Mar;11(1):159-60; Perry PJ and Wilborn CA: Serotonin syndrome vs neuroleptic malignant syndrome: a contrast of causes, diagnoses, and management. Ann Clin Psychiatry. 2012 May;24(2):155-62; Santelli J et al: Heat illness in the emergency department: keeping your cool. Emerg Med Pract. 2014 Aug;16(8):1-21; quiz 21-2; Seitz DP and Gill SS: Neuroleptic malignant syndrome complicating antipsychotic treatment of delirium or agitation in medical and surgical patients: case reports and a review of the literature. Psychosomatics. 2009 Jan-Feb;50(1):8-15; Wilson MH et al: Intracranial pressure at altitude. High Alt Med Biol. 2014 Jun;15(2):123-32; Zafren K: Prevention of high altitude illness. Travel Med Infect Dis. 2014 Jan-Feb;12(1):29-39.

Disclosures

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the planning committee to disclose relevant financial relationships within the past 12 months that might create any personal conflicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, members of the faculty and planning committee reported nothing to disclose. In his lecture, Dr. Derlet discusses the off-label or investigational use of a therapy, product, or device.

Acknowledgements

Dr. Derlet was recorded at the 37th Annual UC Davis Winter Conference: Emergency Medicine 2014, held February 24-28 2014, in Lake Tahoe, CA, and sponsored by the UC Davis Health System, Office of Continuing Medical Education and Division of Infectious Diseases, Department of Emergency Medicine. For information on future CME activities from this sponsor, please visit www.ucdmc.ucdavis.edu/cme/conferences. The Audio Digest Foundation thanks the speakers and sponsors for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

EM321102

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.