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

4. Connecticut

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

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

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

8. This was no ordinary Everest expedition
This was no ordinary Everest expedition. Normal expedition is a group of americans or whatever with Sherpas as support team. History of supersherpa expedition 8

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
Do not acclimatize – deteriorate..not even natives acclimatize above…

12. O2 still 21% but partial pressure drops

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

15. Map of Everest 15

17. Acclimatization physiology
Simplify this slide…One third of the partial pressure of oxygen of Everest vs sea level. If any of us were transported to the top of Everest, we would fall unconscious in 2 minutes and die in 6 minutes. But, Lowlanders have climbed to summit without Everest.

18. Acclimatization schedules
Lowlander
Base Camp
To top ice fall then Base Camp
Rest (Base Camp)
Base Camp to Camp I
Touch Camp II then back to Camp I
Camp I to Base Camp
Camp I to Camp II
Rest (Camp II)
Part way up Lhotse face then to Camp II
Camp II to Base Camp
Base Camp to Camp II
Camp II to Camp III
Yellow Band then to Camp II
Wait for weather window
Drink whiskey at BC. 18

19. Acclimatization schedules
Lowlander
Base Camp
To top ice fall then Base Camp
Rest (Base Camp)
Base Camp to Camp I
Touch Camp II then back to Camp I
Camp I to Base Camp
Camp I to Camp II
Rest (Camp II)
Part way up Lhotse face then to Camp II
Camp II to Base Camp
Base Camp to Camp II
Camp II to Camp III
Yellow Band then to Camp II
Wait for weather window
Sherpa
Base Camp
Base Camp to Camp II
Rest (Camp II)
Wait for weather window
Drink whiskey at BC. 19

20. 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
Might think-I’ll just breathe faster – NOT! Esp when asleep
Not as prominent in SA (vs Himalaya) and therefore more ch mtn sickness (lived at HA for yrs vs millions of years)

21. Hypoxic Ventilatory Response
Am J Phys :445-62
Altitude (ft)
Resp Rate
Min Vent (L/min) 12 8
12,000 14 10
18,000 15 11
24,000 27 23
HVR-not as prominent in SA (vs Himalaya) and therefore more ch mtn sickness (lived at HA for yrs vs millions of years)

22. 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)

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
HCT’s above 75% not uncommon
Good up to a point, then hyperviscous and dvt

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

28. Help Acclimatization Many ask me if they should use diamox…
Side effects

29. Help Acclimatization Vitamin C Calcium Ascorbate
Siberian Ginseng extract
L-Tyrosine
Ginkgo Biloba extract
Schizandra extract
Ginger Root extract
Reishi Mushroom extract
Ginkgo
Four positive studies
Three negative, however

30. Help Acclimatization Diamox CO2 + H2O H2CO3 H+ + HCO2-
causes renal bicarb excretion leading to metabolic acidosis, increasing ventilation
diuretic action decreases edema
sulfa drug and side effects
CO2 + H2O H2CO H+ + HCO2-
Carbonic Anhydrase
Many ask me if they should use diamox…
Side effects

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 24-48 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. Mild Moderate Severe All symptoms mild Not alarming
Symptoms more intense
Disrupting trip
Alarming
Worsening of s/s’s 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
Mandatory descent or Gamow bag if cannot walk
Consider terminating trip
Characteristics
Guy in nepal-wouldn’t come down, hace in end
Treatment

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

41. 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

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?