Thomas DeLoughery



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Thomas DeLoughery

delought@ohsu.edu
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
DISEASES OF HIGH ALTITUDE
ACUTE MOUNTAIN SICKNESS

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.


THERAPY:

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.


HIGH ALTITUDE CEREBRAL EDEMA

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


THERAPY:

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 PULMONARY EDEMA

 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


THERAPY

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

Prevention:

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
Etiology

 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

Prevention:

1) Aspirin ineffective

2) Elastic Stockings

3) Prophylactic LMWH for high risk patients


Lake Louis Score


Self Reported


Parameter

Finding

Points

Headache

none at all

0

 

a mild headache

1

 

moderate headache

2

 

severe headache incapacitating

3

Gastrointestinal Symptoms

good appetite

0

 

poor appetite or nausea

1

 

moderate nausea or vomiting

2

 

severe incapacitating nausea and vomiting

3

Fatigue And/or Weakness

not tired or weak

0

 

mild fatigue/weakness

1

 

moderate fatigue/weakness

2

 

severe incapacitating nausea and vomiting

3

Dizziness/lightheadedness

none

0

 

mild

1

 

moderate

2

 

severe incapacitating

3

Difficulty Sleeping

slept as well as usual

0

 

did not sleep as well as usual

1

 

woke many times poor night's sleep

2

 

could not sleep at all

3

Physical Examination



Parameter

Finding

Points

Change in Mental Status

none

0

 

lethargy lassitude

1

 

disoriented confused

2

 

stupor semiconscious

3

 

coma

4

Ataxia in Heel to Toe Walking

none

0

 

balancing maneuvers

1

 

steps off line

2

 

falls down

3

 

can't stand

4

Peripheral Edema

none

0

 

1 location

1

 

2 or more locations

2


KEY REFERENCES

Hackett PH, Roach RC. High‑altitude illness. N Engl J Med 2001 Jul 12;345(2):107‑14

Hornbein TF (Editor), Schoene RB (Editor). High Altitude: An Exploration of Human Adaptation (Lung Biology in Health and Disease, 161). Marcel Dekker; 2001

Luks AM, McIntosh SE, Grissom CK, Auerbach PS, Rodway GW, Schoene RB, Zafren K, Hackett PH; Wilderness Medical Society. Wilderness Medical Society consensus guidelines for the prevention and treatment of acute altitude illness. Wilderness Environ Med. 2010 Jun;21(2):146-55.

Milledge JS, West JB, Ward MP. High Altitude Medicine and Physiology. Edward Arnold. 2000.

REFERENCES

Arya R, Barnes JA, Hossain U, Patel RK, Cohen AT. Long‑haul flights and deep vein thrombosis: a significant risk only when additional factors are also present. Br J Haematol 2002 Mar;116(3):653‑4.

Bartsch P, Grunig E, Hohenhaus E, Dehnert C. Assessment of high altitude tolerance in healthy individuals. High Alt Med Biol 2001 Summer;2(2):287‑96.

Bartsch P, Swenson ER, Maggiorini M. Update: High altitude pulmonary edema. Adv Exp Med Biol 2001;502:89‑106

Bartsch P, Mairbaurl H, Maggiorini M, Swenson ER Physiological aspects of high-altitude pulmonary edema. J Appl Physiol. 2005 Mar;98(3):1101-10. Review.

Basnyat B, Gertsch JH, Holck PS, Johnson EW, Luks AM, Donham BP, Fleischman RJ, Gowder DW, Hawksworth JS, Jensen BT, Kleiman RJ, Loveridge AH, Lundeen EB, Newman SL, Noboa JA, Miegs DP, O'Beirne KA, Philpot KB, Schultz MN, Valente MC, Wiebers MR, Swenson ER. Acetazolamide 125 mg BD is not significantly different from 375 mg BD in the prevention of acute mountain sickness: the prophylactic acetazolamide dosage comparison for efficacy (PACE) trial.High Alt Med Biol. 2006 Spring;7(1):17-27.

Belcaro G, Geroulakos G, Nicolaides AN, Myers KA, Winford M. Venous thromboembolism from air travel: the LONFLIT study.. Angiology 2001 Jun;52(6):369‑74.

Boes DA, Omura AK, Hennessy MJ. Effect of high‑altitude exposure on myopic laser in situ keratomileusis. J Cataract Refract Surg 2001 Dec;27(12):1937‑41.

Cesarone MR, Belcaro G, Nicolaides AN, De S, Geroulakos G, Lennox A, Myers KA, Moia M, Ippolito E, Winford M,Venous thrombosis from air travel: the LONFLIT3 study‑‑prevention with aspirin vs low‑molecular‑weight heparin (LMWH) in high‑risk subjects: a randomized trial. Angiology 2002 Jan‑Feb;53(1):1‑6.

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Dehnert C, Berger MM, Mairbaurl H, Bartsch P. High altitude pulmonary edema: A pressure-induced leak. Respir Physiol Neurobiol. 2007 Sep 30;158(2-3):266-73.

Gallagher SA, Hackett PH. High-altitude illness. Emerg Med Clin North Am. 2004 May;22(2):329-55

Gertsch JH, Seto TB, Mor J, Onopa J.G inkgo biloba for the prevention of severe acute mountain sickness (AMS) starting one day before rapid ascent. High Alt Med Biol 2002 Spring;3(1):29‑37

Hackett P, Rennie D. High‑altitude pulmonary edema. JAMA. 2002 May 1;287(17):2275‑8.

Hackett PH, Yarnell PR, Hill R, Reynard K, Heit J, McCormick J.High‑altitude cerebral edema evaluated with magnetic resonance imaging: clinical correlation and pathophysiology. JAMA 1998 Dec 9;280(22):1920‑5

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Hornbein TF. Everest: The West Ridge. Mountaineers Books; Reprint edition 1998.

Hornbein TF. The high‑altitude brain. J Exp Biol 2001 Sep;204(Pt 18):3129‑32

Houston CS, Bates RH. K2 the Savage Mountain The Lyons Press; 2000.

Karakucuk S, Mirza GE. Ophthalmological effects of high altitude. Ophthalmic Res 2000 Jan‑Feb;32(1):30‑40.

Lapostolle F, Surget V, Borron SW, Desmaizieres M, Sordelet D, Lapandry C, Cupa M, Adnet F. Severe pulmonary embolism associated with air travel. N Engl J Med 2001 Sep 13;345(11):779‑83.

Maggiorini M, Brunner-La Rocca HP, Peth S, Fischler M, Bohm T, Bernheim A, Kiencke S, Bloch KE, Dehnert C, Naeije R, Lehmann T, Bartsch P, Mairbaurl H. Both tadalafil and dexamethasone may reduce the incidence of high-altitude pulmonary edema: a randomized trial.

Ann Intern Med. 2006 Oct 3;145(7):497-506.

Maggiorini M, Melot C, Pierre S, Pfeiffer F, Greve I, Sartori C, Lepori M, Hauser M, Scherrer U, Naeije R. High‑Altitude Pulmonary Edema Is Initially Caused by an Increase in Capillary Pressure.Circulation 2001 Apr 24;103(16):2078‑2083

Maggiorini M, Brunner-La Rocca HP, Peth S, Fischler M, Bohm T, Bernheim A, Kiencke S, Bloch KE, Dehnert C, Naeije R, Lehmann T, Bartsch P, Mairbaurl H Both tadalafil and dexamethasone may reduce the incidence of high-altitude pulmonary edema: a randomized trial.

Ann Intern Med. 2006 Oct 3;145(7):497-506.

Murdoch DR. Prevention and Treatment of High-altitude Illness in Travelers.

Curr Infect Dis Rep. 2004 Feb;6(1):43-49.

Roach RC, Hackett PH. Frontiers of hypoxia research: acute mountain sickness. J Exp Biol 2001 Sep;204(Pt 18):3161‑70

Roncin JP, Schwartz F, D'Arbigny P. EGb 761 in control of acute mountain sickness and vascular reactivity to cold exposure. Aviat Space Environ Med 1996 May;67(5):445‑52

Schoene RB. Limits of human lung function at high altitude. J Exp Biol 2001 Sep;204(Pt 18):3121‑7

Swenson ER, Maggiorini M, Mongovin S, Gibbs JS, Greve I, Mairbaurl H, Bartsch P. Pathogenesis of high‑altitude pulmonary edema: inflammation is not an etiologic factor. JAMA 2002 May 1;287(17):2228‑35

Unsworth W. Everest : A Mountaineering History. Mountaineers Books. 3rd edition. 2000.



West JB, Weiner IB. High Life: A History of High‑Altitude Physiology and Medicine. Oxford University Press. 1998.


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