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…