High Altitude Medical Problems
Jeffrey H. Gertsch, MDAssistant Professor of Neurosciences
UCSD School of Medicine
Wilderness Basics Course 2-2015
ISMM Definitions
http://www.ismmed.org/np_altitude_tutorial.htm#goldenrules
Definition/Site Altitude in
Meters
Altitude in Feet
High Altitude 1,500 - 3,500 5,000 - 11,500
Very High Altitude 3,500 - 5,500 11,500 - 18,000
Extreme Altitude >5,500 >18,000
Laguna Mountains 2,000s 6,200s
Top of most ski lifts
(aka moderate alt)
2,500-3,500 8,000-11,500
Mt. Whitney Summit 4,421 14,505
Mt. Everest Base
Camp
5,380 17,700
Mt. Everest Summit 8,848 29,029
Why Is Altitude Illness Important ?
• >30 million in US & 100 million
worldwide recreate above 2000m
annually
– Skiing/snowboarding
– Hiking/Climbing
• Military (2 conflicts/decade from 40s)
• Medicine/physiology
• Aerospace/aviation/space flight
• Geology/astronomy
Why Is Altitude Restrictive?• Low Pressure:
– O2 a consistent 20.93% of
atmosphere
– atmospheric pressure
decreases w/ altitude
• Environmental extremes:
– coldest climes
– Radical terrain
– highest winds
– solar radiation (UV)
• Decreased resources (cal)
Blood Oxygen At Altitude
JB West. Respiratory System Under Stress. In Respiratory Physiology; The Essentials. 6th Edition, Lippincott Williams and Wilkins, Philadelphia, 1999, p 119.
What happens with half the available oxygen?
• Normal sea level blood oxygen:
95-100%
• Normal SaO2 on Mt. Whitney:
85-92%
• Strategy: increase efficiency of
delivering oxygen to the tissues =
acclimatization
• What tissues at highest risk of
malfunction, w/highest metabolic
demand/least reserve?
Acute General Acclimatization
• 2-5 minutes: Stress HR/BP increase
• 10-15 minutes: Hyperventilation (HVR)
• Hours:
1. Pulmonary/cerebral blood flow increase
2. Blood chemistry changes Increased urination
3. Increased urine prod Polycythemia (thicker blood)
Chronic General Acclimatization
• Day 1: Renal Epoetin release Increase red blood cell production
• Week 1: Changes in respiratory/blood factors equal contribution to acclimatization
• Week 6-8: New blood vessels in musculature endurance/resilience
• End week 6: Climb 8000m peaks!
Conceptualizing Altitude Sickness
• Acclimatization vs. Illness: When balance fails,
illness results
• Good acclimatization = hyperventilate/urinate
Health
• Poor acclimatization = hypoventilate & decreased
urination (fluid retention) vascular injury/
’waterlogged tissue’ Illness
– Neurological syndromes most common forms of
illness by far
– Severe forms include swelling of brain/lung
Acclimatization
Incomplete at high altitude and does not occur
at extreme altitude.
Over 18,000 ft, gradual decrease in physical
conditioning and a progressive mental
deterioration.
Brain Acclimatization
• Nervous tissue the most sensitive to low oxygen.
• Minutes: Oxygen-starved brain swells w/blood.
– Cerebral blood flow increases >50%, tense vessels.
• All mechanisms must improve efficiency of
oxygen delivery to brain over time.
• Cerebral dysfunction what mainly limits
aggressive ascent profiles.
The Spectrum of Altitude-associated
Neurological Disease (SAAND)
By far the most common form of altitude
illness (100% incidence above 8000m)
High Altitude Headache (HAH)
Acute Mountain Sickness (AMS)
High Altitude Cerebral Edema (HACE)
Don’t forget High Altitude Pulmonary Edema!
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Risk Factors for Altitude Sickness
• Genetic susceptibility
– ELGN/HIF-1
– EPAS1/HIF-2
– PPAR
• Altitude of residence
(<3000 ft)
• Hydration status
• Activity level/exertion
• Illness: Colds, heart/
lung/blood/brain Dz
Risk Factors for Altitude Sickness
• Rate of ascent: #1 cause of
altitude sickness.
– Above 10K ft sleep no higher
than 1000 ft above previous
camp
• Maximum altitude achieved.
– 100% with altitude sickness at
8000 m
• Sleeping altitude.
– Climb high, sleep low
– Olympic training
High Altitude Headache
• Among most common complaints at altitude, & most
common neurological Symptoms.
• Often a benign isolated syndrome.
• Sentinel symptom of acute mountain sickness
(SAAND).
Acute Mountain Sickness
• Requires Headache in
unacclimatized person
recently arrived at >8K ft
and one or more of:
– Fatigue/excessive exhaustion
– Dizziness/lightheaded
– Anorexia nausea vomiting
– Insomnia (not periodic breathing)
• Pearls:
– Think hangover
– Note rarely headache absent1991 Lake Louise AMS Consensus Guideline
AMS and HAH Are Very Common
• How common is HAH?
• HAH: 8-10K ft, 47-62% incidence,
EBC >90%.
• How about AMS?
– 15-30% Colorado resort skiers.
– 50% Mt. McKinley climbers.
– 70% Mt. Rainier climbers.
– 35-50+% Everest BC trekkers.
• Who gets AMS and HAH?
– Young, fit males.
– Think fast ascent rate to high altitude.
– Individual susceptibility widely varied.
– Vigorous exercise.
High Altitude Cerebral Edema (HACE)
• Think end-stage SAAND.
• Components:
– Severe headache (bad AMS)
– Confusion/disorientation
– Walking difficulties/clumsiness
(widened gait)
– Unusual behavior
• Coma and death common if
untreated!
HACE Is Rare
• Most common cause of death from altitude, 50% mortality rate.
• 0.5-1.5% incidence.
• Tips:
– Very rare below 12K ft.
– Often 12-36 hrs after onset of AMS.
– ALL have preceding AMS.
– Patient looks ‘drunk.’
– Frequently occurs with HAPE (up to 80%).
Hackett et al. JAMA 1998
T2 weighted MR on arrival T2 weighted MR 11 months later
Sea level to 5200m in 6 days confusion/ataxia
High Altitude Pulmonary Edema (HAPE)
• Early HAPE:
– Exercise intolerance
usually with a dry cough
– Continued shortness of
breath at rest (low oxygen
saturation)
– Rapid breathing and pulse
• Late-stage HAPE:
– Fluid in lungs (gurgling)
– Cyanosis (blue/dusky lips)
– Unconsciousness & death
HAPE Is Less Common
• Most common cause
of dangerous altitude
sickness.
• Affects 0.6-4%
persons who rapidly
ascend to greater than
12K ft and remain.
• Begins 24-72 hrs
after arrival.
• Prior history (20-60%
risk).
Misc. Neurologic Problems at Altitude
• Retinal micro hemorrhages.
– approach 100% at 8000m.
• Decreased night vision.
• Periodic breathing (Cheyne-Stokes).
• Sleep disordered breathing.
• Behavioral changes.
– depression/anxiety.
• High altitude flatulence expulsion (HAFE).
– Gasses expand at altitude, neuroenteric dysfunction.
Best Prevention is A Staged Ascent
• Tested method by
mountaineers on
expeditions.
• Climb high – sleep low.
• Above 10,000’, sleep no
higher than 1000’ above
the previous camp.
• Additionally, spend 2
nights at the same altitude
every 3 nights.
Other Preventive Measures
• Avoid substances that depress
respiration:
– Alcohol
– Narcotics
– Sleeping pills
• Hi carb diet (over 70%).
• Take it easy (talk & walk).
• Drink lots of fluids (2 L adult).
• Get older (brain shrinkage).
• Weak/no evidence:
– Gingko biloba
– Vitamin C/antioxidants
– Milk thistle, glutamine (?)
Treatment of Mild to Moderate AMS
• Rest and stop ascent.
• Treatment of
Symptoms.
– Ibuprofen for
headache.
– Acetazolamide/
Diamox: 250 mg
2-3/day (prescription)
– Compazine for nausea
(prescription)
• Hydrate.
• Hi carb bland diet
may help.
Role of acetazolamide (Diamox)
• Speeds up acclimatization by ~50%, fairly fast – treat AMS as well.
• Preventive for rapid ascents (rescue, etc).
• Preventive for those w/ past AMS.
• Likely prevents HACE (HAPE?).
• Prevention: 125-250 mg 2x/day – begin 1 day prior to ascent and take till your high point achieved.
• Treatment for moderate AMS: 250 mg 3x/day for 2-3 days.
• Not for those allergic to sulfa.
• Many side effects:– Paresthesias
– Dysgeusia (taste disturbance)
– Polyuria
• Trial dose prior to a big trip advisable.
Treatment Of Severe AMS, HACE, & HAPE
• Early recognition is key.
• Mandatory and immediate
descent (2K ft or more if
possible).
• Oxygen and/or Gamow bag.
• Dexamethasone/Decadron
(steroid) if available.
• If nonambulatory, helicopter
evacuation likely necessary.
• Viagra?? (worsens
headaches).
RAPID DESCENT!
The Gamow bag: a portable
hyperbaric chamber
• Pump up around
affected person.
• 15 lb, yield a 6000’
“drop in elevation”
with 2 psi.
• Observation windows.
• Now use portable
oxygen concentrators.
www.sleeprestfully.com
Conclusion: 5 Golden Rules
of Going to Altitude
1. It is ok to get altitude illness. It is
Not ok to die from it.
2. Any illness at altitude is altitude illness
until proven otherwise.
3. Never ascend with symptoms of AMS.
4. If you are getting worse, go down at once.
5. Never leave someone with AMS Alone.
Honorary
Golden Rules:
Be Prepared,
and know when
to back down
Thank you and
climb safely…