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High Altitude Medicine

High Altitude Medicine. Scott McIntosh, MD, MPH Director, EMS/Wilderness Medicine Fellowship University of Utah. Connecticut. Why study?. Live in or travel to high areas. Why study?. Live in or travel to high areas Excellent physiology. Why study?. Live in or travel to high areas

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High Altitude Medicine

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  1. High Altitude Medicine Scott McIntosh, MD, MPH Director, EMS/Wilderness Medicine Fellowship University of Utah

  2. Connecticut

  3. Why study? • Live in or travel to high areas

  4. Why study? • Live in or travel to high areas • Excellent physiology

  5. Why study? • Live in or travel to high areas • Excellent physiology • Expedition medical director

  6. 14,000 ft Camp

  7. The Plan • Definitions • Acclimatization - by system • Specific problems: • Acute Mountain Sickness (AMS) • High Altitude Cerebral Edema (HACE) • High Altitude Pulmonary Edema (HAPE)

  8. How high is high? 29,000 Extreme 18,000 Very High 12,000 High 8,000 Medium 5,000 Low 0

  9. Acclimatization • Definition: series of adaptations the body undergoes when exposed to high altitude for extended periods • Fascinating and complex physiology

  10. Map of Everest

  11. Acclimatization physiology

  12. Acclimatization schedules Lowlander • Base Camp • To top ice fall then Base Camp • Rest (Base Camp) • Rest (Base Camp) • Base Camp to Camp I • Touch Camp II then back to Camp I • Camp I to Base Camp • Rest (Base Camp) • Rest (Base Camp) • Base Camp to Camp I • Camp I to Camp II • Rest (Camp II) • Part way up Lhotse face then to Camp II • Camp II to Base Camp • Rest (Base Camp) • Rest (Base Camp) • Rest (Base Camp) • Base Camp to Camp II • Rest (Camp II) • Camp II to Camp III • Yellow Band then to Camp II • Base Camp • Wait for weather window

  13. Acclimatization schedules Lowlander • Base Camp • To top ice fall then Base Camp • Rest (Base Camp) • Rest (Base Camp) • Base Camp to Camp I • Touch Camp II then back to Camp I • Camp I to Base Camp • Rest (Base Camp) • Rest (Base Camp) • Base Camp to Camp I • Camp I to Camp II • Rest (Camp II) • Part way up Lhotse face then to Camp II • Camp II to Base Camp • Rest (Base Camp) • Rest (Base Camp) • Rest (Base Camp) • Base Camp to Camp II • Rest (Camp II) • Camp II to Camp III • Yellow Band then to Camp II • Base Camp • Wait for weather window Sherpa • Base Camp • Base Camp • Base Camp • Base Camp • Base Camp • Base Camp to Camp II • Rest (Camp II) • Base Camp • Base Camp • Wait for weather window

  14. Respiratory • Hypoxic Ventilatory Response • Carotid bodies sense decreased pO2 • Central medullary receptors sense pH changes (CO2 diffuses across, dropping pH) • Response is genetically predetermined • South American vs. Himalayan natives

  15. Hypoxic Ventilatory Response Am J Phys 1949 157:445-62

  16. Acid-Base Changes • Result: mild resp alkalosis approx 7.48 (blowing off CO2) • After 1-2 days: Kidneys respond with H+ conservation and HCO3- excretion • pH restored close to (but not = to) 7.40 (occurs at approx 1 week)

  17. Circulatory System • Sympathetic Stimulation: • Increased HR, BP, inotropy • Selective vasoconstriction (muscles, skin, viscera) • SNS normalizes during acclimatization Am J Cardiol 1990 (Operation Everest II) 65:1475-80

  18. Hematological System • Hypoxia causes erythropoietin release • HCT usually 30% above sea level • HCT’s above 75% not uncommon

  19. Help Acclimatization • Graded Ascent • More difficult-easy to travel eg: Lukla • Fluids, high CHO diet • Younger • more susceptible • Physically fit • no protection

  20. Help Acclimatization

  21. Help Acclimatization • Vitamin C • Calcium Ascorbate • Siberian Ginseng extract • L-Tyrosine • Ginkgo Biloba extract • Schizandra extract • Ginger Root extract • Reishi Mushroom extract

  22. Help Acclimatization • Diamox • causes renal bicarb excretion leading to metabolic acidosis, increasing ventilation • diuretic action decreases edema • sulfa drug and side effects CO2 + H2O H2CO3 H+ + HCO2- Carbonic Anhydrase

  23. AMS • Headache plus at least one of the following: • GI upset, weakness/fatigue, difficulty sleeping, dizziness or light-headedness • Nausea, vomiting, anorexia common

  24. AMS • Symptoms develop within a few hours • Max intensity at 24-48 hours • Symptom free at day 3-4 Aviat Space Environ Med 1980;51:872-77

  25. General Treatment of HA Problems • Descent • Portable hyperbaric chamber • Oxygen • Specific medications

  26. Gamow Bag

  27. Characteristics Treatment

  28. High Altitude Cerebral Edema • Continuum of AMS • Brain swelling • Hallmark symptoms: • Ataxia, mental status changes, confusion, stupor, coma

  29. Cerebral Edema?

  30. HACE - Treatment • Early recognition required • Mandatory descent and evacuation • All general high altitude illness treatments • Dexamethasone 8 mg IM or IV then 4 mg every 6 hours • Prognosis good to deadly

  31. HACE Case

  32. HAPE • Most common cause of death in HA • Non-cardiogenic pulmonary edema • At 14K on Denali: • O2 sats in 56% • Avg pO2 = 28 J Appl Physiol 64:2605,1988

  33. HAPE Physiology • Normally hypoxia/ischemia produces vasodilation • In lungs, HYPOXIC VASOCONSTRICTION

  34. HAPE CXR • Patchy b/c of different areas of hypoxia and vasoconstriction, relocation of blood and therefore edema • Normal heart • No Kerley lines

  35. HAPE Susceptibility • People who have abnormally high PAP • Possibly congenital reduced NO synthetase

  36. HAPE Treatment • Oxygen and descent usually sufficient • If those not available, nifedipine • Decreases pulmonary hypertension • New drug?

  37. High Altitude Medical Kit • Meds: • Diamox – PO • Nifedipine – PO • Dexamethasone – IV • Ginko? • Oxygen? • Gamow bag?

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