Acute mountain sickness: Difference between revisions
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==Background== | ==Background== | ||
*Also referred to as AMS | *Also referred to as AMS | ||
*Usually only occurs with altitude | *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) | **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 | *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 | **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 | *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== | ||
* | |||
**[[ | |||
** | *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> | ||
** | **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: | |||
***GI Symptoms ([[nausea]], [[vomiting]], anorexia) | |||
***Sleep symptoms ([[insomnia]], difficulty sleeping) | |||
***[[Dizziness]] and/or lightheadedness | |||
*[[Ataxia]] and [[confusion]] heralds onset of [[headache]] | |||
===Onset=== | ===Onset=== | ||
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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 headache 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]] | *[[Hypoglycemia]] | ||
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==Evaluation== | ==Evaluation== | ||
*Clinical diagnosis | *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 at altitude}} | |||
==Management== | ==Management== | ||
[[File:Altitude flow sheet.png|thumb|High altitude management algorithm.]] | |||
===Mild=== | ===Mild=== | ||
*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> | *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> | ||
**Descend to lower altitude ( | **Descend to lower altitude of 300-500m (1000-3000ft) '''OR''' acclimatize for 12-36hr at same altitude | ||
*[[Acetazolamide]] | *[[Acetazolamide]] | ||
**Mechanism: speeds acclimatization by promoting bicarb diuresis | **Mechanism: speeds acclimatization by promoting bicarb diuresis -> metabolic acidosis -> ↑ ventilation | ||
**Indications: | **Indications: | ||
***History of altitude illness | ***History of altitude illness | ||
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**125-250mg PO BID until symptoms resolve | **125-250mg PO BID until symptoms resolve | ||
**Side-effects | **Side-effects | ||
***Allergic reaction (if patient allergic to sulfa), paresthesias, polyuria, carbonated beverages taste bitter | ***[[Allergic reaction]] (if patient allergic to sulfa), paresthesias, polyuria, carbonated beverages taste bitter | ||
*Symptomatic treatment as necessary with analgesics and antiemetics | ***Can also worsen dehydration by promoting bicarb diuresis | ||
*Symptomatic treatment as necessary with analgesics (NSAIDs) and antiemetics (ondansetron) | |||
*Sleep-agents | *Sleep-agents | ||
**Benzos are only safe if given in conjunction with acetazolamide | **[[Benzos]] are only safe if given in conjunction with acetazolamide | ||
**Nonbenzodiazepines are safe (zolpidem, [[diphenhydramine]]) | **Nonbenzodiazepines are safe ([[zolpidem]], [[diphenhydramine]]) | ||
===Moderate-Severe=== | ===Moderate-Severe=== | ||
*Immediate descent for worsening symptoms | *Immediate descent of 500 m (~ 1500 ft) for worsening symptoms | ||
*Low-flow 0.5-1 L/min O2 if available ( | *Low-flow 0.5-1 L/min [[O2]] if available (especially nocturnal administration) | ||
*[[Acetazolamide]] 250mg PO BID | *[[Acetazolamide]] 250mg PO BID | ||
*[[Dexamethasone]] 4mg PO q6hr | *[[Dexamethasone]] 4mg PO q6hr | ||
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*[[Acetazolamide]] prophylaxis | *[[Acetazolamide]] prophylaxis | ||
**Indicated for patients with history of altitude illness or forced rapid ascent to altitude | **Indicated for patients with history of altitude illness or forced rapid ascent to altitude | ||
**Start 24hr before ascent and continue for the first | **Start 125 mg PO BID 24hr before ascent and continue for the first 48hrs at peak altitude | ||
**Can be restarted if illness develops | **Can be restarted if illness develops | ||
**Reduces symptoms of AMS by 75% in patients ascending rapidly to altitudes >8200ft | **Reduces symptoms of AMS by 75% in patients ascending rapidly to altitudes >8200ft | ||
*[[Dexamethasone]] | *[[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 | **Start day of ascent and continue for first 2 days at altitude | ||
**4mg PO q12hr | **4mg PO q12hr | ||
**Prevents and treats cerebral edema | **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 | *Ginkgo biloba | ||
**Controversial if effective; safe | **Controversial if effective; safe | ||
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==Disposition== | ==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== | ==See Also== | ||
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
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
- Dehydration
- AMS is not improved by fluid administration alone
- Body hydration does not influence susceptibility to AMS
- Exhaustion
- Viral syndrome
- Alcohol hangover
- Substance abuse
- Caffeine withdrawal
- Hypothermia
- CO poisoning
- CNS infection: Meningitis, Encephalitis
- Cerebral venous sinus thrombosis
- Migraine
- Whereas supplemental O2 helps headache due to AMS in 10-15min, O2 has no effect on migraines
- TIA
- Hypoglycemia
High Altitude Illnesses
- Acute mountain sickness
- Chronic mountain sickness
- High altitude cerebral edema
- High altitude pulmonary edema
- High altitude peripheral edema
- High altitude retinopathy
- High altitude pharyngitis and bronchitis
- Ultraviolet keratitis
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
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
- 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[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
- 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 [5]
- 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
- ↑ 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.
- ↑ Gallagher, MD, Scott A.; Hackett, MD, Peter (August 28, 2018). "High altitude pulmonary edema". UpToDate. Retrieved May 2, 2019.
- ↑ 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.
- ↑ 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)
- ↑ 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.