Thomas DeLoughery

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Thomas DeLoughery
High Altitude Medicine Synopsis

Adjustment to Altitude
 Major problem is low oxygen!

 Major goal of altitude adaptation is to improve "chain of oxygen"

 Ventilation: increase respiratory rate, increase CO2 sensitivity

 Pulmonary artery pressure: increases

 Cardiac: HR increases, CO decreases due to lowered stroke volume

 Hematologic: Initial increase hematocrit due to hemoconcentration then increase in EPO secretion

 Changes in oxygen disassociation curve

 Modest elevation (0-10,000 ft): lowered O2 affinity to increase tissue delivery

 Increased elevation (10-20,000 ft): shift back to normal O2 affinity

 Extreme elevation (>20,000 ft) increased O2 affinity to increase O2 uptake from air

 Fluid balance: Early diuresis upon arriving at altitude

Nutrition: increase metabolism, anorexia and possible fat malabsorption

High Altitude Training

 Considerable controversy on role of hypoxia and altitude for improving performance

 Most data for "Train-low Sleep-High" programs with best results for athletes spending over 18 hours at altitude

 Response correlated with increase in hematocrit and EPO

 Only 60% of athletes respond - unknown genetic factors

Incidence varies - rate increases with altitude and rate of ascent with less than 5% with rapid travel to 5,000 ft, 40-60% at 10,000ft, and almost 100% at 15,000ft.

 Little AMS seen with rate of ascent less than 1000ft/day

 AMS occurs 6- 24 hour at altitude

 Cardinal symptom is headache - victims may also c/o of fatigue, nausea and decreased urine output

 Score by Lake Louise Score (see table) AMS if self-reported >4 or total score greater than 5.


1) No further ascent!

2) Acetazolamide 250 mg BID- increases oxygenation and aids diuresis

3) Descending by 150-3000 ft, especially is symptoms are moderate or severe.

4) Dexamethasone 4 mg q 6hr - improves symptoms but does not aid acclimatization. Used with acetazolamide for severe cases

Options for Prevention of AMS

1) Slow ascents: Classic recommendation not to ascend more than 1000ft/day above 10,000ft with a rest day (2 nights at the same altitude) every 2-3 days.

2) Acetazolamide 125 mg BID to start 1 day before and continue for 2-3 days at altitude.

3) Ginkgo Biloba 60-120 mg BID to start 5 day before and continued at altitude. Most useful for modest altitude – variation with type of preparation.


Severe AMS with altered mental status, ataxia, and other neurological manifestations such as seizures.

Rare: 1-3%

Can be fatal - fatality rate 60% once patient is comatose


1) Descent as soon as possible

2) Dexamethasone 8 mg load then 4 mg q6 hours

3) O2 at 2-4 l/hour

4) If descent not possible consider oxygen and portable hyperbaric chamber.
Etiology of AMS/HACE

 Predisposing factors: hypoxia, lowered hypoxic ventilatory response, fluid retention

 Past occurrence of AMS/HACE strongest risk factor for recurrence

 Current theories center on role of brain swelling at altitude and raised ICP


 High altitude disease that kill most people

 Incidence: severe cases 1-5% but increase lung water seen in 75% of climbers

 Early signs are weakness and shortness of breath that evolves in tachypnea, tachycardia, and severe hypoxia


1) Rapid Descent

2) Oxygen 4-6/l

3) Nifedepine 10 mg po then 30mgSR q12-24 hours

4) Portable hyperbaric chamber if descent not possible

5) Sildenafil (Viagra) 50 TID: Lowers pulmonary artery pressures and improves oxygenation without systemic hypotension

6) Increasing data that acetazolimide may also help HAPE


Patients who have suffered from HAPE are prone to recurrence

1) Slower ascent

2) Nifedipine 20-30 mg q12 hours

3) Increasing evidence that steroids may prevent HAPE

 Patients prone to HAPE have exaggerated pulmonary artery pressure to hypoxia

 Uneven blood flow to parts of the lung may lead to stress breakdown of endothelium and fluid leak
Sleep Problems at Altitude

 Poor sleep common at altitude - increase incidence of Cheyne-stokes breathing

 Therapy: acetazolamide 125 mg or zolpidem 10 mg qHS
High Altitude Retinopathy and Refractive Surgery

 Incidence of hemorrhage 36-56% at altitudes 15,000ft

 Rarely causes permanent damage

 Patients with both RF can have dramatic vision changes with ascending to over 12,000ft. Vision returns to normal when descending to sea level. Increasing data to suggest LASIK does not cause significant vision changes at altitude.

High Altitude and Travel's Thrombosis

 Multiple case reports of DVT, PE, and stroke at altitude

 Hypoxia not associated with increase in coagulation

 Most cases due to classic risk factors such as dehydration, immobilization, and genetic factors

 Risk of thrombosis with air-travel increase 3-4 fold

 Most patients with DVT have other risk factors


1) Aspirin ineffective

2) Elastic Stockings

3) Prophylactic LMWH for high risk patients

Lake Louis Score

Self Reported





none at all



a mild headache



moderate headache



severe headache incapacitating


Gastrointestinal Symptoms

good appetite



poor appetite or nausea



moderate nausea or vomiting



severe incapacitating nausea and vomiting


Fatigue And/or Weakness

not tired or weak



mild fatigue/weakness



moderate fatigue/weakness



severe incapacitating nausea and vomiting












severe incapacitating


Difficulty Sleeping

slept as well as usual



did not sleep as well as usual



woke many times poor night's sleep



could not sleep at all


Physical Examination




Change in Mental Status




lethargy lassitude



disoriented confused



stupor semiconscious





Ataxia in Heel to Toe Walking




balancing maneuvers



steps off line



falls down



can't stand


Peripheral Edema




1 location



2 or more locations



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