Acute Mountain SicknessMANAGEMENT

ENVIRONMENTAL AND EXPOSURE PRESENTATIONS · 12 SECTIONS

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576 items

☷ Legend

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Cardiovascular Presentations71▾

Respiratory Presentations52▾

Neurological Presentations83▾

Gastrointestinal Presentations74▾

Genitourinary and Reproductive Presentations48▾

Infectious Disease Presentations148▾

Trauma Presentations89▾

Toxicologic Presentations80▾

Psychiatric Presentations26▾

Musculoskeletal and Rheumatologic Presentations96▾

Dermatology Presentations23▾

Environmental and Exposure Presentations27▾

Acute Mountain Sickness Arterial Gas Embolism Bee-Wasp Sting (Anaphylaxis)Chilblains Ciguatera Fish Poisoning Coral Cut Decompression Sickness Electrical Burn Injury Envenomation (snake, spider, insect)High Altitude Cerebral Edema (HACE)High Altitude Pulmonary Edema (HAPE)High-altitude illness Hypothermia Hypothermia (Mild)Hypothermia (Severe)Immersion Foot Lightning Strike Injury Scombroid Fish Poisoning Scorpion Envenomation Sea Urchin Injury Shark Bite Snake Envenomation Spider Bite (Black Widow)Spider Bite (Brown Recluse)Stingray Spine Injury Tick paralysis White Phosphorus Burn

Hematologic and Oncologic Presentations36▾

Pediatric-Specific Presentations19▾

Endocrine and Metabolic Presentations45▾

ENT and Maxillofacial Presentations27▾

Ophthalmologic Presentations19▾

Obstetric Presentations23▾

Systemic and Miscellaneous Presentations17▾

01Approach to the Critical Patient/attcp62

Immediate priorities

›Distinguish benign AMS from life threats

›High altitude cerebral edema concern

›Ataxia on heel-to-toe walking

›Altered mental status or drowsiness

›Coma may ensue within 12 to 24 hours of ataxia onset if untreated

›High altitude pulmonary edema concern

›Dyspnea at rest

›Cough with pink frothy sputum

›Cyanosis

›If any HACE or HAPE sign, immediate descent and oxygen

›Descent is definitive treatment

›Do not delay for imaging or labs

›Time-critical airway and breathing

›Oxygenation failure at altitude

›SpO2 lower than expected for altitude

›Target SpO2 above 90% with supplemental oxygen

›Mental status threat to airway

›Obtunded patient from HACE

›Aspiration risk with vomiting

›If unable to protect airway, definitive airway control

›Rapid sequence intubation preparation

›Continue descent and oxygen during transfer

›Early branching decision

›Uncomplicated AMS pattern

›Headache plus nausea, fatigue, or dizziness with normal neuro exam

›Self-limited course over 12 to 48 hours without further ascent

›Complicated altitude illness pattern

02History/hx65

Presentation pattern

›Cardinal symptom

›Headache

›Dull bifrontal or temporal quality

›Worsened by movement or Valsalva

›Required associated symptom

›Nausea or anorexia

›Fatigue or lassitude

›Dizziness or lightheadedness

›Sleep disturbance

›Insomnia with frequent awakenings

›Central sleep apnea common at altitude

›Ascent and exposure context

›Altitude reached and sleeping elevation

›Prevalence rises about 13% per 1000 m above 2500 m

›Onset usually 2 to 12 hours after arrival

›Rate of ascent

›Gain above 400 m per day in sleeping elevation increases risk

›Lack of preacclimatization in prior 1 to 2 months

›Timing relative to arrival

›Symptoms starting beyond 3 days without further ascent argue against AMS

›Symptom onset relative to peak exertion

Risk factors

›Strong predictors

›Prior AMS history

›Strongest individual risk factor

›Recurrence odds ratio up to 12

›Rapid ascent rate

03Physical Exam/exam48

Vitals and general

›Altitude-adjusted vitals

›Tachycardia

›Expected physiologic response at altitude

›Palpitations usually benign

›Mild tachypnea

›Hypoxic ventilatory response

›Rest dyspnea is abnormal and suggests HAPE

›Oxygen saturation

›Lower than sea level and varies by altitude

›Notably low SpO2 for altitude suggests severe illness

›General appearance

›Hydration status

›Dry mucosa from respiratory water loss

›Reduced thirst drive

›Pallor or cyanosis

›Cyanosis suggests HAPE

›Functional impairment marker

Neurologic exam

›HACE screening

›Heel-to-toe walk test

›Earliest sign is gait ataxia

›Inability indicates HACE

›Mental status

›Must be normal in AMS

›Confusion or drowsiness indicates HACE

›Funduscopic exam

›Papilledema confirms cerebral edema

04Differential Diagnosis/ddx40

Life threats and altitude spectrum

›Altitude illness spectrum

›Acute mountain sickness

›ICD-10 T70.20XA effects of high altitude

›Headache plus one associated symptom

›High altitude cerebral edema

›Ataxia and encephalopathy

›End stage of AMS continuum

›High altitude pulmonary edema

›Rest dyspnea and cough

›Patchy infiltrates on imaging

›Immediate non-altitude threats

›Carbon monoxide poisoning

›Enclosed shelters or tents with stoves

›Elevated carboxyhemoglobin

›Ischemic stroke or mass lesion

›Focal neurologic deficits

›Seizure activity

›Hyponatremia

›Excessive water intake during exertion

›Altered mentation and headache

Common mimics

›Constitutional and toxic mimics

›Alcohol hangover

›Symptoms closely mimic AMS

›Recent heavy intake history

›Dehydration and exhaustion

›Common at altitude

05Laboratory Tests/lt35

Diagnostic role

›Diagnosis is clinical

›No lab establishes AMS

›Lake Louise scoring drives diagnosis

›Labs reserved for excluding mimics

›Pulse oximetry adjunct

›Monitors acclimatization

›High SpO2 for altitude protective

Rule-out studies

›Metabolic panel

›Basic metabolic panel

›Hyponatremia from water intoxication

›Renal function assessment

›Point-of-care glucose

›Hypoglycemia if altered mentation

›Rapid bedside result

›Targeted studies

›Complete blood count

›If infection suspected

›Leukocytosis supports alternative diagnosis

›Carboxyhemoglobin

›If CO exposure in enclosed shelter

›Co-oximetry required, standard SpO2 misleading

Gas exchange and severity markers

›Oxygenation assessment

›SpO2 trend

›Disproportionately low value suggests HAPE

›Useful for gauging acclimatization

06Diagnostic Tests/dt73

Scoring Systems

›Lake Louise AMS Score 2018 revision

›Scored domains

›Headache on 0 to 3 scale

›Gastrointestinal symptoms on 0 to 3 scale

›Fatigue on 0 to 3 scale

›Dizziness on 0 to 3 scale

›Interpretation

›Score 3 or more with headache defines AMS

›Mild AMS score 3 to 5

›Moderate to severe AMS score 6 to 12

›Revision note

›Sleep disturbance removed in 2018 revision

›Used in clinical and research settings

›Clinical Functional Score

›Single question on activity impact

›Scored 0 to 3

›Simplest bedside tool

›Performance

›Score 2 or more positive LR 3.2 for severe AMS

›Complements Lake Louise Score

›AMS-Cerebral score

›Research-oriented measure

›Threshold 0.70 or more indicates AMS

›Used primarily in studies

›Limitations

›Not practical for rapid bedside use

›Clinical trajectory supersedes score

07Disposition/dispo38

Level of care selection

›May remain at altitude

›Mild AMS improving on treatment

›Normal neuro exam

›Functional and tolerating oral intake

›Close observation conditions

›Companion monitoring available

›No further ascent until symptoms resolve

›Descent indicated

›Moderate to severe AMS not improving

›No improvement after 1 to 3 days of treatment

›Descend 300 to 1000 m

›Any HACE sign

›Ataxia or altered mental status

›Immediate descent is definitive

›Any HAPE sign

›Rest dyspnea or cyanosis

›Productive cough

›Admission or higher-level care

›HACE or HAPE

›Require monitoring and supplemental oxygen

›Pharmacotherapy and possible critical care

›Instability

›Altered mental status

›Hemodynamic instability

Resuming ascent and follow up

›Reascent criteria

›Complete symptom resolution required

08Treatment/t84

Initial stabilization

›Stop further ascent

›Rest at current elevation

›Do not ascend until symptoms resolve

›Reassess for HACE and HAPE features

›Supportive measures

›Maintain hydration

›Avoid alcohol and sedative-hypnotics

›Oxygen and descent thresholds

›Supplemental oxygen

›1 to 2 L/min for symptomatic relief

›Target SpO2 above 90% in severe illness

›If symptoms worsen, descend

›Descent 300 to 1000 m

›Descent of even 300 m is therapeutic

Mild AMS

›Symptomatic therapy

›Analgesia

›Ibuprofen 600 mg PO every 8 hours

›Acetaminophen 500 mg PO every 8 hours alternative

›Antiemetic

›Ondansetron 4 mg orally disintegrating tablet as needed

›Avoid sedating antiemetics where possible

›Acclimatization aid

›Acetazolamide 250 mg PO every 12 hours to speed acclimatization

›Remain at current altitude until resolution

›Avoidances

›Opioid analgesics

›Respiratory depression risk at altitude

›Use non-opioid analgesia

›Sedative-hypnotics

›Avoid unless combined with acetazolamide

›Risk of nocturnal hypoventilation

Moderate to severe AMS

›Corticosteroid therapy

›Dexamethasone

›4 mg PO, IV, or IM every 6 hours for 24 hours

›More reliable than acetazolamide for treatment

›Rebound caution

›Does not facilitate acclimatization

›Rebound symptoms if stopped at altitude before acclimatizing

›Adjuncts and descent

›Acetazolamide adjunct

›250 mg PO every 12 hours

›Aids underlying acclimatization

›Oxygen and descent

›Supplemental oxygen 1 to 2 L/min if available

›Descend 300 to 1000 m if symptoms persist

HACE and HAPE management

›HACE treatment

›Immediate descent

›Definitive treatment

›Do not delay for testing

›Dexamethasone

›8 mg loading dose PO, IV, or IM

›Then 4 mg every 6 hours

›Oxygen and chamber

›Supplemental oxygen to SpO2 above 90%

›Portable hyperbaric chamber simulates about 2000 m descent at 2 psi

›HAPE treatment

›Descent and oxygen

›Descent plus supplemental oxygen

›Minimize exertion during descent

›Pulmonary vasodilator

›Nifedipine SR 30 mg PO every 12 hours if oxygen unavailable and descent not feasible

›Monitor for hypotension

›Avoid diuretics

›No role in HAPE

›Risk of hypovolemia

Prevention and evidence

›Pharmacologic prophylaxis

›Acetazolamide

›125 mg PO every 12 hours starting day before ascent

›Continue 2 to 4 days at target altitude

›Contraindicated with anaphylaxis or Stevens-Johnson to sulfonamides

›Dexamethasone

›2 mg PO every 6 hours or 4 mg every 12 hours

›Alternative if acetazolamide intolerant

›Does not aid acclimatization

›Ibuprofen

›600 mg PO every 8 hours

›Alternative when other agents contraindicated

›Guideline basis

›Wilderness Medical Society 2024 update

›Severity stratification and treatment recommendations

›Acetazolamide for prevention and acclimatization

›Nonpharmacologic prevention

›Gradual ascent below 500 m per day in sleeping elevation above 3000 m

›Rest days every 3 to 4 days

09Special Populations/sp39

Pregnancy

›Pregnancy considerations

›Travel counseling

›Limited data on high-altitude exposure

›Avoid sleeping above 3000 m where feasible

›Medication safety

›Acetazolamide generally avoided in pregnancy

›Dexamethasone reserved for severe illness only

›Management priorities

›Descent and oxygen are mainstays

›Maintain maternal SpO2 above 95% when feasible

›Monitoring

›Fetal assessment when viable gestation

›Low threshold for descent

Geriatric

›Older adult features

›Susceptibility nuance

›Age above 50 years not protective against severe outcomes

›Comorbidities increase risk

›Comorbidity interactions

›Chronic lung disease raises HAPE risk

›Cardiac disease affects travel tolerance

›Medication caution

›Renal dosing of acetazolamide

›Polypharmacy and sedation burden review

›Disposition bias

›Lower threshold for descent

›Closer monitoring

10Background/b57

Epidemiology

›Incidence and burden

›Prevalence among ascenders

›Affects 25% to 43% of travelers above 2500 m

›Most common form of altitude illness

›Altitude dependence

›Prevalence rises about 13% per 1000 m above 2500 m

›Higher sleeping elevation increases risk

›Progression and recurrence

›Progression to HACE in under 1% of AMS cases

›Recurrence up to 60% with similar ascent profiles

›Natural history

›Self-limited course

›Resolves in 12 to 48 hours without further ascent

›Rapid improvement with descent

›Severity distribution

›Most cases mild

›Moderate to severe minority

Pathophysiology

›Hypoxia-driven mechanism

›Hypobaric hypoxia

›Reduced inspired oxygen partial pressure

›Triggers hypoxic ventilatory response

›Cerebral mechanisms

›Cerebral vasodilation and increased blood flow

›Vasogenic edema in HACE

›Pulmonary mechanisms

›Hypoxic pulmonary vasoconstriction

11Patient Discharge Instructions/pdi20

copy discharge instructions

›Altitude illness home care

›Do not go any higher to sleep until you feel completely better

›Rest at your current elevation

›Drink plenty of fluids and avoid alcohol

›Take medicines exactly as prescribed

›Medication guidance

›Use acetaminophen or ibuprofen for headache

›Take acetazolamide as directed to help you adjust

›Do not use sleeping pills or strong pain medicines

›Return to ER or descend immediately if

›Trouble walking straight or feeling clumsy

›Confusion, severe drowsiness, or trouble waking

›Shortness of breath at rest

›Cough with pink or frothy spit

›Blue lips or fingertips

›Vomiting that prevents keeping fluids or medicines down

›Future trip advice

›Climb slowly and allow rest days

›Ask your clinician about preventive medicine if this has happened before

›Prior altitude sickness does not mean you cannot travel high again

12References/r15

Guidelines and key sources

›Society guidelines

›Wilderness Medical Society Clinical Practice Guidelines 2024 update

›CDC Yellow Book High-Altitude Travel and Altitude Illness 2025

›AAFP summary of Wilderness Medical Society altitude guidelines 2020

›Landmark reviews

›Luks and Hackett Medical Conditions and High-Altitude Travel NEJM 2022

›Bartsch and Swenson Acute High-Altitude Illnesses NEJM 2013

›Gatterer et al Altitude Illnesses Nature Reviews Disease Primers 2024

›Scoring and decision tools

›Roach et al 2018 Lake Louise Acute Mountain Sickness Score

›Does This Patient Have Acute Mountain Sickness JAMA 2017 Rational Clinical Examination

›Clinical Functional Score for bedside severity assessment

›Coding standards

›ICD-10 T70.20XA effects of high altitude unspecified

›SNOMED CT acute mountain sickness disorder concept

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Reviewed by SymptomDx Medical Team · Last reviewed August 18, 2026

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