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

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Presentation on theme: "High Altitude Medicine Scott McIntosh, MD, MPH Director, EMS/Wilderness Medicine Fellowship University of Utah."— Presentation transcript:

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

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4 Connecticut

5 Why study? 1.Live in or travel to high areas

6 Why study? 1.Live in or travel to high areas 2.Excellent physiology

7 Why study? 1.Live in or travel to high areas 2.Excellent physiology 3.Expedition medical director

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9 14,000 ft Camp

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

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

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

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18 Lowlander 1.Base Camp 2.To top ice fall then Base Camp 3.Rest (Base Camp) 4.Rest (Base Camp) 5.Base Camp to Camp I 6.Touch Camp II then back to Camp I 7.Camp I to Base Camp 8.Rest (Base Camp) 9.Rest (Base Camp) 10.Base Camp to Camp I 11.Camp I to Camp II 12.Rest (Camp II) 13.Part way up Lhotse face then to Camp II 14.Camp II to Base Camp 15.Rest (Base Camp) 16.Rest (Base Camp) 17.Rest (Base Camp) 18.Base Camp to Camp II 19.Rest (Camp II) 20.Camp II to Camp III 21.Yellow Band then to Camp II 22.Base Camp 23.Wait for weather window

19 Lowlander 1.Base Camp 2.To top ice fall then Base Camp 3.Rest (Base Camp) 4.Rest (Base Camp) 5.Base Camp to Camp I 6.Touch Camp II then back to Camp I 7.Camp I to Base Camp 8.Rest (Base Camp) 9.Rest (Base Camp) 10.Base Camp to Camp I 11.Camp I to Camp II 12.Rest (Camp II) 13.Part way up Lhotse face then to Camp II 14.Camp II to Base Camp 15.Rest (Base Camp) 16.Rest (Base Camp) 17.Rest (Base Camp) 18.Base Camp to Camp II 19.Rest (Camp II) 20.Camp II to Camp III 21.Yellow Band then to Camp II 22.Base Camp 23.Wait for weather window Sherpa 1.Base Camp 2.Base Camp 3.Base Camp 4.Base Camp 5.Base Camp 6.Base Camp to Camp II 7.Rest (Camp II) 8.Base Camp 9.Base Camp 10.Wait for weather window

20 Respiratory Hypoxic Ventilatory Response 1.Carotid bodies sense decreased pO 2 2.Central medullary receptors sense pH changes (CO 2 diffuses across, dropping pH) Response is genetically predetermined South American vs. Himalayan natives

21 Hypoxic Ventilatory Response Am J Phys : Altitude (ft) Resp RateMin Vent (L/min) , , ,

22 Acid-Base Changes 1.Result: mild resp alkalosis approx 7.48 (blowing off CO 2 ) 2.After 1-2 days: Kidneys respond with H + conservation and HCO 3 - excretion 3.pH restored close to (but not = to) 7.40 (occurs at approx 1 week)

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25 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:

26 Hematological System Hypoxia causes erythropoietin release HCT usually 30% above sea level HCTs above 75% not uncommon

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

28 Help Acclimatization

29 Vitamin C Calcium Ascorbate Siberian Ginseng extract L-Tyrosine Ginkgo Biloba extract Schizandra extract Ginger Root extract Reishi Mushroom extract

30 Help Acclimatization Diamox –causes renal bicarb excretion leading to metabolic acidosis, increasing ventilation –diuretic action decreases edema –sulfa drug and side effects CO 2 + H 2 O H 2 CO 3 H + + HCO 2 - Carbonic Anhydrase

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

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

33 General Treatment of HA Problems Descent Portable hyperbaric chamber Oxygen Specific medications

34 Gamow Bag

35 MildModerateSevere All symptoms mild Not alarming Symptoms more intense Disrupting trip Alarming Worsening of s/ss of AMS Possibly altered mental status Other HA illness may be present Stay at current altitude Resume when improved Tylenol for headache Compazine for N/V Consider descent but not mandatory Diamox Resume when improved Mandatory descent or Gamow bag if cannot walk Diamox Consider terminating trip

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

37 Cerebral Edema?

38 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

39 HACE Case

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41 HAPE Most common cause of death in HA Non-cardiogenic pulmonary edema At 14K on Denali: –O 2 sats in 56% –Avg pO 2 = 28 J Appl Physiol 64:2605,1988

42 HAPE Physiology Normally hypoxia/ischemia produces vasodilation In lungs, HYPOXIC VASOCONSTRICTION

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

44 HAPE Susceptibility People who have abnormally high PAP Possibly congenital reduced NO synthetase

45 HAPE Treatment Oxygen and descent usually sufficient If those not available, nifedipine –Decreases pulmonary hypertension –New drug?

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


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