High Altitude Mountaineering Seminar 2013 - 10.16.13 High Altitude Medicine
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Transcript of High Altitude Mountaineering Seminar 2013 - 10.16.13 High Altitude Medicine
High Altitude MedicineScott R Valent MD
High Altitude Medicine● University of Vermont College of Medicine● Multiple high altitude treks in Nepal,
Pakistan, Tibet● Travels in Peru, Ecuador, Argentina, Bolivia● Aconcagua● Cardiologist
Highest cities in the world
● Lhasa, Tibet 12,000 ft● La Paz, Bolivia 11,910 ft● Cuzco, Peru 11,152 ft● Sucre, Bolivia 9,331 ft● Quito, Ecuador 9,249 ft.● Toluca, Mexico 8,793 ft.● Bogota, Columbia 8,675 ft.● Addis Ababa, Ethiopia 7,900 ft.● Asmara, Ethiopia 7,789 ft.
Altitude Facts
● The percentage of oxygen at altitude is the same as sea level, approximately 21%
● Atmospheric and partial pressure decrease with altitude, allowing less oxygen availability
● Barometric pressure 760mmHg sea level● Barometric pressure 253mmHg Mt Everest● Pressure 222mmHg at 67 degrees N lat.
Altitude sickness
Anyone traveling to high altitude may be at risk for developing altitude sickness
● AMS● HAPE● HACE
Physiology at altitude●
Physiologic effects of altitude
High altitude 5,000-11,500 ft. (1,500-3,500m)● AMS common with rapid ascent● Decreased exercise capacity● Pulse oximetry pOx>90%
Physiologic effects of altitudeVery High Altitude 11,500-18,045 ft (3500-5500m)● Most common range for severe high
altitude illness● Abrupt ascent dangerous● Pulse Oximetry 75-85%● Extreme hypoxia may occur during
sleep, exercise and high-altitude illness
Physiologic effects of altitudeExtreme altitude 18,000-29,035 (5500-8850m)● Progressive deterioration outstrips
acclimatization● Humans cannot permanently live at these
altitudes● High likelihood of severe high-altitude illness
with rapid ascent● Pulse oximetry 58-75%
Acclimatization
● Immediate: Rapid breathing and HR● Increased catecholamines● Dehydration● Pulmonary artery pressure increases● Increase in hematocrit within 4 days● Increase in 2,3-DPG
Cheyne-Stokes Breathing
● “Hey, my tentmate stopped breathing”
● The respiratory drive, particularly while sleeping is primarily driven by CO2
● At altitude CO2 levels are typically lower and breathing may be initiated by decreased O2.
● This leads to erractic breating, with long, frightening pauses.
Risk categories for acute mountain sicknessRisk category Description Prophylaxis
recommendation
LOW People with no prior history of altitude illness and ascending to <9,000ft.People taking >2 days to arrive at 8,000-9,000feet with subsequent increases in sleeping elevation <1,600 feet/dy, and an extra day for acclimatization every 3,200 feet
Acetazolamide prophylaxis is generally not indicated
MODERATE People with prior history of AMS and ascending 8,000-9,000 feet in one dayNo history of AMS and ascending to >9,000 feet in 1 dayAll people ascending >1,600 ft per day at altitudes above 9,000 ft., but with an extra day for acclimatization every 3,200 feet
Acetazolamide prophylaxis would be beneficial and should be considered
HIGH
Hackett, P.H. Altitude illness, 2014 yellow book
History of AMS and ascending to >9,000 feet in 1 dayAll people with a prior history of HACE or HAPEAll people ascending to >11,400 feet in one dayAll people ascending to >1,600 feet per day above 9,000 feet, without extra days for acclimatizationVery rapid ascents (such as <7 day ascents of Mount Kilimanjaro
Acetazolamide prophylaxis strongly recommended
Acute Mountain Sickness(AMS)
● Very common○ 15-30% of colorado resort skiers○ 50% of Mt. McKinley climbers○ 70% of Mt. Ranier climbers
Lake Louise CriteriaAcute Mountain sickness
● Headache plus at least one of the following:
○ fatigue or weakness○ nausea,vomiting, anorexia○ dizziness, lightheadedness, insomnia
HAPEDefinition: Accumulation of fluid in the lungs leading to hypoxiaUnrelated to AMS
● Incidence: 0.1-5%● Often manifests at night, frequently
the second night● Can progress rapidly● May lead to HACE
Lake Louise CriteriaHAPE
● At least two of the following symptoms:
○ Dyspnea at rest○ Cough○ weakness or decreased exercise
performance○ Chest tightness or congestion
Lake Louise CriteriaHAPE
● At least two of the following signs:
○ Central cyanosis○ rales or wheezing○ Tachypnea○ Tachycardia
HAPERisk Factors● Young, fit males● Exertion● Cold
HAPE-Treatment● Treatment of choice is descent
(2,000 feet)● Oxygen● Nifedipine, Sildenafil● Gamow Bag● Mortality rate for untreated HAPE
may be up to 44%
HACE
● Treatment● Immediate descent● Oxygen● Steroids-Decadron● Gamow bag
Treatment
Gamow bag
Gamow bag
Golden rules of high altitude medicine
● If you are sick at high altitude, it is altitude sickness until proven otherwise
● Never ascend with symptoms of AMS● If you are deteriorating or have signs
or symptoms of HAPE or HACE, descend immediately
Medications/DosagesAcetazolamide/Diamox
Indication
AMS, HACE prevention
AMS treatment
Hackett, P.H. Altitude illness, 2014 yellow book
Route
oral
Oral
Dose
125mg twice a day250mg twice a day if over 100KG
250mg twice a day
Medications/DosagesDexamethasone
Indication
AMS, HACE prevention
AMS, HACE treatment
Hackett, P.H. Altitude illness, 2014 yellow book
Route
oral
oral, iv, im
Dose
2mg every 6 hours, or 4mg every 12 hrs
AMS: 4mg every 6 hrs.HACE: 8mg once, then 4mg every 6 hrs.
Medications/DosagesNifedepine
Indication
HAPE prevention
HAPE treatment
Hackett, P.H. Altitude illness, 2014 yellow book
Route
oral
oral
Dose
30mg SR (slow release) every 12 hrs or 20mg SR every 8hrs
30mg SR every 12 hrs. or 20mgSR every 8 hrs.
Medications/DosagesSildenafil (Viagra)
Indication
HAPE prevention
Hackett, P.H. Altitude illness, 2014 yellow book
Route
oral
Dose
50mg every 8 hrs.
Prevention● One night at an altitude slightly below 10,000 feet● At altitudes above 10,000 feet, increase sleeping
altitude by only 1,000-1,500 feet per night● Spend a second night at the same altitude for every
increase of 3,000 ft.● Example : Aconcagua:with a generous 1,500 foot
per night increase, plus several rest and weather days, expect 9-10 days prior to summit night at 20,000+ feet
PreventionAcetazolamide● Diuretic used to help hasten acclimatization● 250-1,000 mg daily● Mechanism: During initial time at altitude
rapid breathing decreases CO2 and decreases acidity of blood
● Acetazolamide helps acidify blood● Improves symptom scores for AMS● may improve sleep● Does not protect against AMS with ascent
Other hazards at altitude
Bronchitis/chronic cough
● Cool extremely dry air-hyperventilation, mouth breathing
● Cough● Broken ribs● Can mimic HAPE
Sunburn
● UV intensity increases 4% per 1,000 feet● at 18,000 feet 72% more sun exposure, not
including snow reflection
Ultraviolet Keratitis● Snow blindness● Corneal damage from UV light● Damage can occur in one hour● Symptoms may not develop for
6-12 hours● PREVENTION
Frostbite
Summary● Prevention is critical● Golden rules● Early diagnosis and descent● As one travels higher the
margin for error decreases significantly
Questions?
Recommended websites
● Altitude.org● BasecampMD.com● http://www.high-altitude-medicine.com/● CDC chapter by Peter Hackett: http://wwwnc.
cdc.gov/travel/yellowbook/2014/chapter-2-the-pre-travel-consultation/altitude-illnesshttp://wwwnc.
cdc.gov/travel/yellowbook/2014/chapter-2-the-pre-travel-consultation/altitude-illness