Acute mountain sickness: Difference between revisions
 
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== Background ==
==Background==
#Usually only occurs with altitude >7000-8000ft
*Also referred to as AMS
##May occur at lower altitudes in pts who are particularly susceptible (COPD, CHF)  
*Usually only occurs with altitude >7,000-8,000ft (2,000 m)
#Associated w/ rate of ascent, sleeping altitude, strength of hypoxic vent response  
**May occur at lower altitudes in patients who are particularly susceptible (COPD, CHF, obesity, history of AMS)  
##NOT associated with physical fitness, age, sex  
*Development of symptoms based on: rate of ascent, sleeping altitude, strength of hypoxic ventilatory response, alcohol intake, obesity
#Pts tend to have recurrence of symptoms whenever they return to the symptomatic altitude
**NOT based on physical fitness, age, sex, smoking, previous high-altitude experience
*Tend to have recurrence of symptoms whenever they return to the symptomatic altitude
*Low partial pressure of O2 leads to decreased diffusion of O2 across alveolar spaces -> hypoxemia results in tachypnea and cerebral vasodilation (↓ CO2) -> increased ICP


== Clinical Features ==
==Clinical Features==
#Onset
 
##Symptoms usually develop 1-6hr after arrival at elevation  
 
###May be delayed for 1-2d
*Lake Louise Consensus Definition <ref>Maggiorini M, Müller A, Hofstetter D, Bärtsch P, Oelz O. Assessment of acute mountain sickness by different score protocols in the Swiss Alps. Aviat Space Environ Med. 1998;69(12):1186-1192.</ref>
##Especially common after the 1st or 2nd night's sleep  
**An Individual is at or above 2500 m (~8000 ft) above sea level ''and''
#Duration
**A [[headache]] is present ''and'':
##Average duration of symptoms at 10,000ft = 15hr  
**An Individual has any one of the following:
##At higher elevations symptoms may last weeks / more likely to progress to HACE
***GI Symptoms ([[nausea]], [[vomiting]], anorexia)
#Diagnosis
***Sleep symptoms ([[insomnia]], difficulty sleeping)
##Requires HA + 1 or more of the following:
***[[Dizziness]] and/or lightheadedness
###Nausea, vomiting, or anorexia
*[[Ataxia]] and [[confusion]] heralds onset of [[headache]]
###Fatigue or weakness
 
###Dizzy or lightheadedness
===Onset===
###Difficulty sleeping
*Symptoms usually develop 1-6hr after arrival at elevation  
#Ataxia and confusion heralds onset of HACE
**May be delayed for 1-2d
*Especially common after the 1st or 2nd night's sleep  
 
===Duration===
*Average duration of symptoms at 10,000ft = 15hr  
*At higher elevations symptoms may last weeks / more likely to progress to headache


==Differential Diagnosis==
==Differential Diagnosis==
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**Body hydration does not influence susceptibility to AMS  
**Body hydration does not influence susceptibility to AMS  
*Exhaustion
*Exhaustion
*Alcohol hangover
*[[Viral syndrome]]
*[[Alcohol]] hangover
*Substance abuse
*[[Caffeine withdrawal]]
*[[Hypothermia]]  
*[[Hypothermia]]  
*[[CO poisoning]]
*[[CO poisoning]]
*CNS infection  
*CNS infection: [[Meningitis]], [[Encephalitis]]
*[[Cerebral venous sinus thrombosis]]
*[[Migraine]]  
*[[Migraine]]  
**Whereas supplemental O2 helps HA due to AMS in 10-15min, O2 has no effect on migraines
**Whereas supplemental [[O2]] helps headache due to AMS in 10-15min, O2 has no effect on migraines
*[[TIA]]
*[[TIA]]
*[[Hypoglycemia]]


{{High altitude DDX}}
{{High altitude DDX}}


== Treatment ==
==Evaluation==
#Mild AMS
*Clinical diagnosis
##Terminate ascent  
*Mental status, cerebellar exam - rule out [[HACE]]
###Descend to lower altitude (by 1000-3000ft) OR acclimatize for 12-36hr at same altitude  
*Lung exam - rule out [[HAPE]]
##Acetazolamide  
*Lake Louise Scoring System: Sum of symptoms 0-3 (none, mild, moderate, severe/incapacitating). Mild corresponds to score 3-4, Moderate-severe corresponds to score ≥5
###Mechanism: speeds acclimatization by promoting bicarb diuresis  
**Headache
###Indications:  
**Gastrointestinal symptoms
####History of altitude illness  
**Fatigue/weakness
####Abrupt ascent to >9800ft  
**Lightheadedness
####AMS requiring treatment  
**Difficulty Sleeping
####Bothersome periodic breathing during sleep  
 
###125-250mg PO BID until symptoms resolve  
{{Expected SpO2 at altitude}}
###Side-effects  
 
####Allergic reaction (if pt allergic to sulfa), paresthesias, polyuria  
==Management==
##Symptomatic treatment as necessary w/ analgesics and antiemetics  
[[File:Altitude flow sheet.png|thumb|High altitude management algorithm.]]
##Sleep-agents  
===Mild===
###Benzos are only safe if given in conjunction with acetazolamide  
*Terminate ascent and/or descend <ref> Luks A, McIntosh S, Grissom C, Auerbach P, Rodway G, Schoene R, Zafren K, Hackett P. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2014 Update. Wilderness Environ Med. 2014; S4-S14.</ref>
###Nonbenzos are safe (zolpidem, diphenhydramine)  
**Descend to lower altitude of 300-500m (1000-3000ft) '''OR''' acclimatize for 12-36hr at same altitude  
#Moderate-Severe AMS
*[[Acetazolamide]]
##Immediate descent for worsening symptoms  
**Mechanism: speeds acclimatization by promoting bicarb diuresis -> metabolic acidosis -> ↑ ventilation
##Low-flow 0.5-1 L/min O2 if available (esp nocturnal administration)  
**Indications:  
##Acetazolamide 250mg PO BID  
***History of altitude illness  
##Dexamethasone 4mg PO q6hr  
**Abrupt ascent to >9800ft  
###Symptom-improvement only; unlike acetazolamide does not aid acclimatization  
***AMS requiring treatment  
##Hyperbaric therapy
***Bothersome periodic breathing during sleep  
**125-250mg PO BID until symptoms resolve  
**Side-effects  
***[[Allergic reaction]] (if patient allergic to sulfa), paresthesias, polyuria, carbonated beverages taste bitter
***Can also worsen dehydration by promoting bicarb diuresis
*Symptomatic treatment as necessary with analgesics (NSAIDs) and antiemetics (ondansetron)
*Sleep-agents  
**[[Benzos]] are only safe if given in conjunction with acetazolamide  
**Nonbenzodiazepines are safe ([[zolpidem]], [[diphenhydramine]])
 
===Moderate-Severe===
*Immediate descent of 500 m (~ 1500 ft) for worsening symptoms
*Low-flow 0.5-1 L/min [[O2]] if available (especially nocturnal administration)  
*[[Acetazolamide]] 250mg PO BID  
*[[Dexamethasone]] 4mg PO q6hr  
**Symptom-improvement only; unlike acetazolamide does not aid acclimatization  
*Hyperbaric therapy
 
==Prevention==
*Graded ascent with adequate time for acclimatization is the best prevention
*[[Acetazolamide]] prophylaxis
**Indicated for patients with history of altitude illness or forced rapid ascent to altitude
**Start 125 mg PO BID 24hr before ascent and continue for the first 48hrs at peak altitude
**Can be restarted if illness develops
**Reduces symptoms of AMS by 75% in patients ascending rapidly to altitudes >8200ft
*[[Dexamethasone]]<ref>Luks AM, McIntosh SE, Grissom CK, et al. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2014 Update. Wilderness & Environmental Medicine. 2014(25): S4–S14)</ref>
**Start day of ascent and continue for first 2 days at altitude
**4mg PO q12hr
**Prevents and treats cerebral edema
*Combination [[acetazolamide]] and [[dexamethasone]]
**Small study showed combination of both (500mg SR daily of [[acetazolamide]] and 4 mg BID [[dexamethasone]]) was more effective at preventing AMS than [[acetazolamide]] alone for rapid ascent <ref>Bernhard WN, Schalick LM, Delaney PA, Bernhard TM, Barnas GM. Acetazolamide plus low-dose dexamethasone is better than acetazolamide alone to ameliorate symptoms of acute mountain sickness. Aviat Space Environ Med. 1998;69(9):883-886.</ref>
*Ginkgo biloba
**Controversial if effective; safe
*[[Ibuprofen]]
**Prevention - less effective than acetazolamide, better than placebo
**Treatment of headache (however, important to consider that taking ibuprofen may mask symptoms)


== Prevention ==
==Disposition==
#Graded ascent w/ adequate time for acclimatization is the best prevention
*Most patients are treated symptomatically and managed as outpatients
#Acetazolamide prophylaxis
*If other high altitude illnesses are considered, consider further work-up and/or observation
##Indicated for pts w/ history of altitude illness or forced rapid ascent to altitude
##Start 24hr before ascent and continue for the first 2d at altitude
##Can be restarted if illness develops
##Reduces symptoms of AMS by 75% in pts ascending rapidly to altitudes &gt;8200ft
#Dexamethasone
##Start day of ascent and continue for first 2d at altitude  
##4mg PO q12hr
##Prevents and treats cerebral edema
#Ginkgo biloba
##Controversial if effective; safe


==See Also==
==See Also==
[[High Altitude Medicine]]
*[[High Altitude Medicine]]


==Source==
==References==
Tintinalli
<References/>


[[Category:Environ]]
[[Category:Environmental]]

Latest revision as of 21:38, 30 May 2022

Background

  • Also referred to as AMS
  • Usually only occurs with altitude >7,000-8,000ft (2,000 m)
    • May occur at lower altitudes in patients who are particularly susceptible (COPD, CHF, obesity, history of AMS)
  • Development of symptoms based on: rate of ascent, sleeping altitude, strength of hypoxic ventilatory response, alcohol intake, obesity
    • NOT based on physical fitness, age, sex, smoking, previous high-altitude experience
  • Tend to have recurrence of symptoms whenever they return to the symptomatic altitude
  • Low partial pressure of O2 leads to decreased diffusion of O2 across alveolar spaces -> hypoxemia results in tachypnea and cerebral vasodilation (↓ CO2) -> increased ICP

Clinical Features

  • Lake Louise Consensus Definition [1]
    • An Individual is at or above 2500 m (~8000 ft) above sea level and
    • A headache is present and:
    • An Individual has any one of the following:
  • Ataxia and confusion heralds onset of headache

Onset

  • Symptoms usually develop 1-6hr after arrival at elevation
    • May be delayed for 1-2d
  • Especially common after the 1st or 2nd night's sleep

Duration

  • Average duration of symptoms at 10,000ft = 15hr
  • At higher elevations symptoms may last weeks / more likely to progress to headache

Differential Diagnosis

High Altitude Illnesses

Evaluation

  • Clinical diagnosis
  • Mental status, cerebellar exam - rule out HACE
  • Lung exam - rule out HAPE
  • Lake Louise Scoring System: Sum of symptoms 0-3 (none, mild, moderate, severe/incapacitating). Mild corresponds to score 3-4, Moderate-severe corresponds to score ≥5
    • Headache
    • Gastrointestinal symptoms
    • Fatigue/weakness
    • Lightheadedness
    • Difficulty Sleeping

Expected SpO2 and PaO2 levels at altitude[2]

Altitude SpO2 PaO2 (mm Hg)
1,500 to 3,500 m (4,900 to 11,500 ft) about 90% 55-75
3,500 to 5,500 m (11,500 to 18,000 ft) 75-85% 40-60
5,500 to 8,850 m (18,000 to 29,000 ft) 58-75% 28-40

Management

High altitude management algorithm.

Mild

  • Terminate ascent and/or descend [3]
    • Descend to lower altitude of 300-500m (1000-3000ft) OR acclimatize for 12-36hr at same altitude
  • Acetazolamide
    • Mechanism: speeds acclimatization by promoting bicarb diuresis -> metabolic acidosis -> ↑ ventilation
    • Indications:
      • History of altitude illness
    • Abrupt ascent to >9800ft
      • AMS requiring treatment
      • Bothersome periodic breathing during sleep
    • 125-250mg PO BID until symptoms resolve
    • Side-effects
      • Allergic reaction (if patient allergic to sulfa), paresthesias, polyuria, carbonated beverages taste bitter
      • Can also worsen dehydration by promoting bicarb diuresis
  • Symptomatic treatment as necessary with analgesics (NSAIDs) and antiemetics (ondansetron)
  • Sleep-agents

Moderate-Severe

  • Immediate descent of 500 m (~ 1500 ft) for worsening symptoms
  • Low-flow 0.5-1 L/min O2 if available (especially nocturnal administration)
  • Acetazolamide 250mg PO BID
  • Dexamethasone 4mg PO q6hr
    • Symptom-improvement only; unlike acetazolamide does not aid acclimatization
  • Hyperbaric therapy

Prevention

  • Graded ascent with adequate time for acclimatization is the best prevention
  • Acetazolamide prophylaxis
    • Indicated for patients with history of altitude illness or forced rapid ascent to altitude
    • Start 125 mg PO BID 24hr before ascent and continue for the first 48hrs at peak altitude
    • Can be restarted if illness develops
    • Reduces symptoms of AMS by 75% in patients ascending rapidly to altitudes >8200ft
  • Dexamethasone[4]
    • Start day of ascent and continue for first 2 days at altitude
    • 4mg PO q12hr
    • Prevents and treats cerebral edema
  • Combination acetazolamide and dexamethasone
  • Ginkgo biloba
    • Controversial if effective; safe
  • Ibuprofen
    • Prevention - less effective than acetazolamide, better than placebo
    • Treatment of headache (however, important to consider that taking ibuprofen may mask symptoms)

Disposition

  • Most patients are treated symptomatically and managed as outpatients
  • If other high altitude illnesses are considered, consider further work-up and/or observation

See Also

References

  1. ↑ Maggiorini M, Müller A, Hofstetter D, Bärtsch P, Oelz O. Assessment of acute mountain sickness by different score protocols in the Swiss Alps. Aviat Space Environ Med. 1998;69(12):1186-1192.
  2. ↑ Gallagher, MD, Scott A.; Hackett, MD, Peter (August 28, 2018). "High altitude pulmonary edema". UpToDate. Retrieved May 2, 2019.
  3. ↑ Luks A, McIntosh S, Grissom C, Auerbach P, Rodway G, Schoene R, Zafren K, Hackett P. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2014 Update. Wilderness Environ Med. 2014; S4-S14.
  4. ↑ Luks AM, McIntosh SE, Grissom CK, et al. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2014 Update. Wilderness & Environmental Medicine. 2014(25): S4–S14)
  5. ↑ Bernhard WN, Schalick LM, Delaney PA, Bernhard TM, Barnas GM. Acetazolamide plus low-dose dexamethasone is better than acetazolamide alone to ameliorate symptoms of acute mountain sickness. Aviat Space Environ Med. 1998;69(9):883-886.
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