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Altitude - Related Illnesses. Jim Holliman, M.D., F.A.C.E.P. Professor of Military and Emergency Medicine Uniformed Services University of the Health Sciences Clinical Professor of Emergency Medicine George Washington University Bethesda, Maryland, U.S.A. Altitude - Related Illnesses.

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Altitude - Related Illnesses


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slide1

Altitude - Related Illnesses

Jim Holliman, M.D., F.A.C.E.P.

Professor of Military and Emergency Medicine

Uniformed Services University of the Health Sciences

Clinical Professor of Emergency Medicine

George Washington University

Bethesda, Maryland, U.S.A.

slide2

Altitude - Related Illnesses

  • Acute Mountain Sickness (AMS)
  • High Altitude Pulmonary Edema (HAPE)
  • High Altitude Cerebral Edema (HACE)
  • High Altitude Retinopathy
  • High Altitude Peripheral Edema
slide3

Acute Mountain Sickness :

Incidence

  • Sudden ascent > 10,000 feet (3000 meters) : 30 %
  • Sudden ascent > 14,000 feet : 75 %
  • Report from Colorado ski resort : 12 %
  • Can occur in those with no prior problems with altitude exposure
  • Can recur (no consistent tolerance or "immunity")
slide4

Acute Mountain Sickness :

Etiology

  • Typically occurs at altitude > 8000 feet
  • Rarely occurs at altitude 6000 to 8000 feet
  • No predeliction based on gender
  • More likely if :
    • Rapid ascent
    • Lack of acclimatization
slide5

Situations Predisposing to Possible Acute Mountain Sickness

  • Prolonged non-pressurized aircraft or balloon flight
  • Colorado or Utah ski resorts
    • Base altitude for most is about 8000 feet
  • Yellowstone National Park
    • base altitude 7000 to 7500 feet
  • Medellin and Bogota, Colombia
    • base altitude > 9000 feet
slide7

Relationships of the Different Forms of Altitude Illness

Altitude illness may be an interrelated spectrum :

AMS HAPE

HACE

slide8

Acute Mountain Sickness :

Pathophysiology

  • Much individual variation in susceptibility
  • Basically due to hypobaric hypoxia of altitude
  • Also involves tendency for fluid retention (effect of antidiuretic hormone)
slide10

Arterial Blood Gas Values in Normal Adults at Different Altitudes

Altitude

PaO2

O2 Saturation

(per cent)

PaCO2

Sea Level

90 to 95

96

40

5000 feet

75 to 81

95

32 to 33

7500 feet

69 to 74

92 to 93

31 to 33

15,000 feet

48 to 53

86

25

20,000 feet

37 to 45

76

20

25,000 feet

32 to 39

68

13

29,029 feet *

26 to 33

58

9.5 to 13

* (the top of Mt. Everest)

slide11

Relative hypoventilation

Sleep disordered breathing

s

slide12

Acute Mountain Sickness :

Exacerbating Factors

  • Sudden ascent
  • Exertion soon after arrival
  • Alcohol intake
  • Sedatives (sleeping pills)
  • Narcotics

Note : youth and / or prior conditioning are NOT uniformly protective

slide13

Acute Mountain Sickness :

Symptoms

  • Headache
  • Nausea
  • Anorexia
  • Lassitude
  • "Like a hangover"
  • Insomnia
  • Decreased urination
  • Onset typically 8 to 24 hours after ascent
slide14

Acute Mountain Sickness :

Differential Diagnosis

  • Dehydration
  • Hypothermia
  • Exhaustion
  • Respiratory infection
  • Hyperventilation syndrome
  • Psychiatric disorders
  • Drug intoxication
  • Carbon monoxide poisoning (as from tent heaters or stoves)
slide15

Acute Mountain Sickness :

Prophylaxis

  • Acclimatization
    • Staging of ascent
    • Delaying exertion
  • Medication choices :
    • Acetazolamide (Diamox) 250 mg PO bid or tid
    • Dexamethasone (Decadron) 4 mg PO tid or qid
    • Should start either med 24 hours prior to ascent
slide18

Acute Mountain Sickness :

Treatment of the Established Syndrome

  • Usually resolves in 1 to 3 days even without Rx or descent
  • Sx will improve however with descent
  • If severe Sx, start acetazolamide 250 mg PO bid or tid, or dexamethasone 4 mg PO tid to qid
  • Resting is the most important treatment
slide19

Progression of Acute Mountain Sickness

  • If ascent is continued or accelerated by a patient with untreated AMS, HAPE or HACE may occur and death may result
slide20

High Altitude Pulmonary Edema

(HAPE)

  • Is a non-cardiogenic pulmonary edema related to altitudinal hypoxia
  • Can be fatal if patient is unable to descend
  • Occurs in 1 to 2 % of patients quickly ascending to > 12,000 feet
  • Can occur even in well fit and acclimatized individuals
slide21

High Altitude Pulmonary Edema :

Onset

  • Usually begins 24 to 72 hours after arrival at altitude
  • Can occur, but uncommon, at altitude 8000 to 12,000 feet
  • Onset usually at night
slide22

High Altitude Pulmonary Edema in Long-term Mountain Residents

  • H.A.P.E. has been reported in patients acclimatized to high altitude who went to low altitude for > 10 days, & then returned to high altitude
  • Termed "reentry pulmonary edema"
slide24

High Altitude Pulmonary Edema :

Symptoms

  • Usual sequence :
    • Cough dyspnea at rest achy chest pain progressive cough progressive rales frothy sputum hemoptysis frank respiratory failure
  • Chest X-ray appearance is variable :
    • Patchy infiltrates (often right > left)
    • If severe, may be bilateral "whiteout"
slide25

High Altitude Pulmonary Edema :

Treatment

  • Most important : Rapid descent : at least 2000 feet
  • High flow O2 ; CPAP mask if available
  • Have patient avoid exertion on descent (other people should carry him / her)
  • Can give acetazolamide or dexamethasone but these do not help much or obviate the need for descent
  • Can try bag pressure chamber if available but still need descent
slide26

High Altitude Cerebral Edema (HACE)

  • Less common than HAPE
  • Possibly a malignant form of AMS
  • Can be fatal or result in permanent neurologic disability (stroke-like syndromes)
  • Onset is gradual : usually over 2 to 3 days
slide27

High Altitude Cerebral Edema :

Symptoms

  • Severe headache
  • Confusion
  • Agitation / irritability
  • Nausea / emesis
  • Ataxia
  • Hallucinations
  • Seizures
  • Coma
slide28

High Altitude Cerebral Edema :

Field Treatment

  • ONLY effective treatment is descent : at least 3000 feet
  • Rx adjuncts :
    • High flow O2 / hyperventilation
    • Dexamethasone / acetazolamide
    • Furosemide / mannitol
    • Benzodiazepines / diphenylhydantoin if seizures occur
    • Avoid exertion during descent
    • Hyperbaric bag if available
slide29

In-Hospital Treatment of Suspected HAPE or HACE

  • Airway / breathing / circulation
  • High flow oxygen +/- intubation & hyperventilation
  • Chest X-ray
  • IV dexamethasone & acetazolamide
  • Check ABG & carboxyhemoglobin
  • Consider tox & drug screen
  • Head CT if abnormal mental status
  • Admit to ICU
  • Consider hyperbaric O2 Rx(call nearest chamber)
slide30

High Altitude Retinal Hemorrhage

  • Incidence is 20 to 40 % above 14,000 feet
  • Usually does not affect vision (unless macular bleed)
  • Usually asymptomatic
  • Diabetics at higher risk
  • Usually no Rx or descent needed
slide33

High Altitude Peripheral Edema

  • Shows as edema of :
    • Face
    • Eyelids
    • Hands
    • Feet
    • Lower legs
  • No Rx usually needed (can use diuretic effect of acetazolamide if patient uncomfortable)
slide34

Miscellaneous Altitude Related Medical Problems

  • Tendency to venous thrombosis & pulmonary emboli (partly due to polycythemia of altitude exposure)
  • Immune suppression
    • probably related to tissue hypoxia
    • wounds slower to heal & more likely to get infected
    • wound infections can show antibiotic resistance
  • High Altitude Flatus Expulsion (HAFE)
    • Reference : Auerbach & Geehr, 1989, pg. 25
    • No serious sequelae noted to date
  • "Snow Blindness" (ultraviolet light exposure)
slide35

Preexisting Illnesses Aggravated by High Altitude

  • C.O.P.D.
  • Coronary artery disease
  • Peripheral vascular disease
  • Hypertension
    • Variable worsening in some patients
  • Sickle cell disease
  • Pregnancy
    • Preeclampsia, but not other complications of pregnancy, is more common at altitude
slide36

Skin Problems Related to High Altitude Exposure

  • Shorter time for sunburn to occur to exposed skin
  • Tendency to drying ; thereby more risk of chilblains or pernio
  • Slower wound healing & higher wound infection rate ; prevention of even minor skin injuries (especially friction blisters) is therefore important
slide37

Altitude Illnesses :

Summary

  • Best treatment is prevention :
    • Acclimatization / staging ascent
    • Avoiding alcohol & sedatives
    • Medication prophylaxis
  • If symptoms suggest HAPE or HACE :
    • start oxygen
    • arrange immediate assisted descent
    • definitive followup care in a medical facility after descent, even if symptoms abate
slide38

Ultraviolet Light Keratitis

("Snow Blindness")

  • UV radiation increases 4 % for every 300 meters increase in altitude
  • Cornea absorbs UVB (below 300 nm)
  • Lens cataracts can result from chronic exposure to UV radiation > 300 nm
  • High exposure levels can cause corneal burn in < 1 hour
  • Symptoms usually take 6 to 12 hours to develop (same as for "welders' arc keratitis")
slide39

Snow Blindness Symptoms & Signs

  • Eye pain
  • Gritty sensation of eyes
  • Light sensitivity
  • Tearing
  • Conjunctival injection
  • Chemosis
  • Eyelid swelling
slide40

Snow Blindness :

Treatment

  • Remove contact lenses
  • Topical anesthetic : single dose only
    • Tetracaine or proparacaine
    • Repetitive use may damage cornea
  • Ophthalmic antibiotic ointment
    • Erythromycin, gentamicin, or sulfacetamide
  • Eye patch for 12 to 24 hours
  • Most should heal in < 24 hours
  • May need oral narcotics for pain
slide41

Snow Blindness :

Prevention

  • Should choose sunglass lenses that are rated to transmit < 10 % of UVB
  • Side shields or full goggles needed to prevent exposure from side bounce
  • Sunglasses should always be secured with a neck loop when mountain climbing
  • If sunglasses are lost, makeshift protective shields can be made by cutting thin slits in pieces of cardboard
slide42

Snow Avalanches :

Medical Relevance

  • About 100,000 release annually in U.S.
  • About 100 of these cause injury, death, or major property damage
  • About 140 people in U.S. are caught each year
  • Reported average of 12 major injuries & 17 deaths annually
  • Persons at risk include skiers, snowmobilers, highway plow operators, and forest rangers & game wardens
slide44

Physical Characteristics of Avalanches

  • Typical velocities are 50 to 100 miles per hour
  • Can be as fast as 200 miles per hour
  • Can generate impact pressures > 150 lbs/square inch (can destroy even concrete structures)
  • Occur with greatest frequency on slopes of 30 to 45 degrees
slide45

Causes of Death from Avalanches

  • Direct impact trauma of snow blocks or ice
  • Indirect trauma of hitting against objects such as trees or rocks
  • Hypoxia from encasement in snow
  • Hypothermia
  • Restrictive chest compression
slide46

Prevention of Death or Injury from Avalanches

  • Have group spread out when approaching or crossing avalanche terrain
  • Have rescue poles, colored cords, & avalanche rescue beacons or transceivers ready
  • Always try to escape an avalanche to the side (not downhill away from the avalanche)
  • If caught & tumbled, keep your hands up near your face