High-altitude illnessMANAGEMENT

ENVIRONMENTAL AND EXPOSURE PRESENTATIONS · 12 SECTIONS

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458 items

☷ Legend

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Cardiovascular Presentations66▾

Respiratory Presentations47▾

Neurological Presentations77▾

Gastrointestinal Presentations63▾

Genitourinary and Reproductive Presentations44▾

Infectious Disease Presentations146▾

Trauma Presentations88▾

Toxicologic Presentations67▾

Psychiatric Presentations25▾

Musculoskeletal and Rheumatologic Presentations89▾

Dermatology Presentations21▾

Environmental and Exposure Presentations26▾

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 White Phosphorus Burn

Hematologic and Oncologic Presentations30▾

Pediatric-Specific Presentations13▾

Endocrine and Metabolic Presentations42▾

ENT and Maxillofacial Presentations21▾

Ophthalmologic Presentations15▾

Obstetric Presentations17▾

Systemic and Miscellaneous Presentations15▾

01Approach to the Critical Patient/attcp58

Immediate priorities

›Stabilization priorities

›Airway protection triggers

›Inability to protect airway

›Persistent vomiting with altered mental status

›Breathing targets

›Pulse oximetry continuous

›Supplemental oxygen to SpO2 90% or higher

›Circulation targets

›Systolic blood pressure 90 mmHg or higher

›Large bore IV access if severe illness

›Temperature control

›Hypothermia prevention during evacuation

›Hyperthermia control during exertion

›Glucose rapid check

›Point of care glucose for altered mental status

Syndrome recognition

›High altitude syndromes

›Acute mountain sickness

›Headache after recent ascent

›Gastrointestinal upset

›Fatigue or weakness

›Dizziness or lightheadedness

›Sleep disturbance

›High altitude cerebral edema

›Ataxia

›Altered mental status

›Severe headache

›Focal neurologic deficits possible

›High altitude pulmonary edema

›Dyspnea at rest

›Cough

›Reduced exercise tolerance

›Tachycardia

›Hypoxemia out of proportion to altitude

Time critical actions

›Immediate escalation triggers

›If suspected high altitude cerebral edema, immediate descent

›Oxygen if available

›Dexamethasone initiation

›If suspected high altitude pulmonary edema, immediate descent

›Oxygen if available

›Nifedipine initiation if oxygen limited

›If severe symptoms and descent delayed, portable hyperbaric chamber

›Repeat sessions until evacuation feasible

Monitoring

›Monitoring bundle

›Neurologic trend

›Mental status trend

›Gait assessment trend

›Respiratory trend

›SpO2 trend with exertion and rest

›Work of breathing trend

›Fluid status trend

›Oral intake

›Urine output

Consultation and activation

›Support activation

›Mountain rescue activation for HACE or HAPE

›Weather and terrain constraints

›Helicopter eligibility

›ICU capable destination for HACE or HAPE

›Transfer planning early

02History/hx51

Altitude exposure

›Altitude timeline

›Current altitude

›Sleeping altitude

›Highest altitude reached

›Rate of ascent

›Sleeping altitude gain per day

›Recent rapid ascent or air travel to altitude

›Acclimatization status

›Days at intermediate altitude

›Prior altitude in last 2 months

Symptom profile

›Symptom inventory

›Headache characteristics

›Onset relative to ascent

›Severity progression

›Gastrointestinal symptoms

›Anorexia

›Nausea

›Vomiting

›Neurologic symptoms

›Ataxia

›Confusion

›Irritability

›Somnolence

›Respiratory symptoms

›Dyspnea at rest

›Orthopnea

›Cough

›Pink frothy sputum possible

Risk factors

›Predisposition

›Prior AMS or HACE or HAPE

›Altitude threshold in past episodes

›Medication response in past episodes

›Cardiopulmonary disease

›Pulmonary hypertension

›Congenital heart disease

›COPD or asthma baseline control

›Exertion and cold exposure

›High exertion early after arrival

›Cold stress

Medication and substance

›Exposures

›Sedatives and alcohol

›Recent use

›Contribution to hypoventilation and sleep disturbance

›Prophylaxis used

›Acetazolamide

›Dexamethasone

›Nifedipine

Functional status

›Performance change

›Exercise tolerance compared with baseline at altitude

›Inability to keep pace

›Inability to perform simple tasks

03Physical Exam/exam45

General and vitals

›Physiologic severity markers

›Pulse oximetry

›Resting SpO2

›SpO2 drop with minimal exertion

›Respiratory rate

›Tachypnea

›Periodic breathing during sleep history correlation

›Heart rate

›Tachycardia disproportionate to activity

›Temperature

›Fever suggests infection rather than isolated altitude illness

Neurologic

›Cerebral edema screen

›Gait and coordination

›Tandem gait inability

›Truncal ataxia

›Mental status

›Disorientation

›Inattention

›Somnolence

›Cranial nerve and focal deficits

›Papilledema possible

›Focal deficit suggests alternative diagnosis

Respiratory

›Pulmonary edema screen

›Work of breathing

›Accessory muscle use

›Inability to speak full sentences

›Lung auscultation

›Crackles often basilar then diffuse

›Wheeze possible

›Perfusion

›Cyanosis

›Cool extremities

Cardiovascular

›Strain markers

›Jugular venous pressure elevation uncommon in isolated HAPE

›Right heart strain signs possible

›Murmur history for congenital lesions

PITFALLS

›Diagnostic pitfalls

›Headache at altitude is not always AMS

›Migraine

›Dehydration

›Carbon monoxide exposure in shelters

›Dyspnea at altitude is not always HAPE

›Pneumonia

›Asthma exacerbation

›Pulmonary embolism

04Differential Diagnosis/ddx18

Life threatening alternatives

›Neurologic emergencies

›Stroke ICD-10 I63

›Intracranial hemorrhage ICD-10 I61

›CNS infection ICD-10 G00

›Hypoglycemia ICD-10 E16.2

›Respiratory and cardiovascular emergencies

›Pulmonary embolism ICD-10 I26

›Pneumonia ICD-10 J18

›Acute coronary syndrome ICD-10 I21

›Heart failure pulmonary edema ICD-10 I50

Mimics and comorbidities

›Common mimics

›Dehydration or volume depletion ICD-10 E86

›Heat illness ICD-10 T67

›Hypothermia ICD-10 T68

›Acute gastroenteritis ICD-10 A09

Altitude related other

›Other altitude syndromes

›High altitude retinal hemorrhage SNOMED CT concept

›Subacute mountain sickness chronic hypoxia related polycythemia

05Laboratory Tests/lt19

Core labs when severe or atypical

›Hospital evaluation labs

›Basic metabolic panel

›Sodium mmol/L for vomiting related hyponatremia

›Creatinine for dehydration and acetazolamide safety

›Complete blood count

›Leukocytosis interpretation caution with stress

›Anemia contribution to hypoxemia

›Venous blood gas

›pH assessment

›PCO2 mmHg for hypoventilation or fatigue

›Lactate mmol/L

›Shock marker

›Sepsis consideration

Infectious evaluation when indicated

›Infection workup

›Blood cultures if febrile and toxic appearance

›Respiratory viral testing based on local prevalence

Pitfalls and limitations

›Interpretation limits

›Normal labs do not exclude HACE or HAPE

›Mild leukocytosis can be physiologic at altitude

06Diagnostic Tests/dt41

Scoring Systems

›Symptom based scoring

›Lake Louise criteria for acute mountain sickness

›Headache required after recent ascent

›One or more additional symptoms

›Gastrointestinal symptoms

›Fatigue or weakness

›Dizziness or lightheadedness

›Sleep disturbance

›Functional impairment grading

›Mild reduced activity

›Moderate stopped ascent

›Severe incapacitated

›Clinical severity heuristics

›Ataxia at altitude treated as HACE until proven otherwise

›Dyspnea at rest at altitude treated as HAPE until proven otherwise

MRI

›Neuroimaging role

›MRI brain for atypical course or nonresponse

›Vasogenic edema patterns possible

›Corpus callosum splenium lesions possible

›MRI limitations at altitude

›Access constraints

›Imaging not required prior to descent in suspected HACE

›Imaging for complications and mimics

›CT head for focal deficit or severe altered mental status

›Hemorrhage exclusion

›Mass lesion exclusion

›Chest imaging for pulmonary syndrome

›Chest radiograph for suspected HAPE

›Patchy bilateral infiltrates often perihilar

›Cardiomegaly typically absent

›CT pulmonary angiography for PE concern

Ultrasound (or US)

›Point of care applications

›Lung ultrasound

›Diffuse B lines consistent with interstitial edema

›Pleural effusions uncommon in isolated HAPE

›Cardiac ultrasound

›Right ventricular strain assessment for alternative diagnosis

›Left ventricular function assessment for cardiogenic edema

›IVC ultrasound

›Volume status adjunct

›Dehydration not primary driver of AMS

07Disposition/dispo28

Level of care

›Admission criteria

›High altitude cerebral edema

›ICU level care

›Continuous neurologic monitoring

›High altitude pulmonary edema

›ICU or monitored setting

›Oxygen requirement beyond minimal

›Severe acute mountain sickness

›Intractable vomiting

›Inability to ambulate

›Inability to maintain hydration

Discharge criteria

›Safe discharge after improvement

›Symptom resolution at rest

›Headache resolved or minimal

›No ataxia

›Stable oxygenation

›SpO2 acceptable for altitude and baseline

›No progression on observation

›Reassuring neurologic trend

›Reassuring respiratory trend

Transfer and evacuation

›Evacuation triggers

›Any suspected HACE

›Immediate descent and definitive medical evaluation

›HAPE with persistent hypoxemia

›Descent and oxygen during transport

›Descent not feasible

›Portable hyperbaric therapy bridge

›Rescue activation

08Treatment/t103

Core principles

›Definitive therapy

›Descent

›Minimum 300 m to 1000 m decrease in sleeping altitude

›Continued descent until sustained improvement

›Oxygen therapy

›Target SpO2 90% or higher

›Nasal cannula or mask based on availability

›Rest

›Stop ascent for all symptomatic patients

›Avoid exertion until symptoms resolve

Acute mountain sickness

›Symptomatic management

›Analgesia

›Ibuprofen PO 400 mg to 600 mg every 6 to 8 hours as needed

›Acetaminophen PO 650 mg to 1000 mg every 6 to 8 hours as needed

›Antiemetic

›Ondansetron ODT or PO 4 mg to 8 mg every 8 hours as needed

›Hydration

›Oral fluids guided by thirst

›Avoid overhydration and hyponatremia risk

›Acetazolamide treatment

›Acetazolamide PO 250 mg every 12 hours

›Onset of benefit within 12 to 24 hours

›Sulfonamide nonantibiotic cross reactivity low but caution

›Dexamethasone for moderate to severe AMS

›Initiate dexamethasone if severe symptoms or inability to descend

›Dexamethasone PO or IM or IV 4 mg every 6 hours

›Rebound symptoms possible after stopping without acclimatization

High altitude cerebral edema

›Immediate therapy bundle

›If suspected HACE, initiate descent immediately

›Assisted descent if ataxic

›Litter evacuation if unable to walk

›Oxygen

›High flow if available

›Target SpO2 90% or higher

›Dexamethasone

›Initiate dexamethasone immediately

›Dexamethasone IV or IM or PO 8 mg once

›Then dexamethasone 4 mg every 6 hours

›Continue until symptom resolution and at least 24 hours at lower altitude

›Portable hyperbaric chamber if descent delayed

›Treatment cycles

›Typical session 60 minutes to 90 minutes

›Repeat if symptoms recur before evacuation

›Adjuncts and cautions

›Acetazolamide role limited in established HACE

›Primary reliance on descent and dexamethasone

›Avoid sedatives

›Hypoventilation risk

›Mental status masking

High altitude pulmonary edema

›Immediate therapy bundle

›If suspected HAPE, initiate descent immediately

›Minimal exertion strategy

›Assisted transport if possible

›Oxygen

›Highest available flow

›Target SpO2 90% or higher

›Nifedipine when oxygen limited or severe cases

›Initiate nifedipine extended release PO 30 mg every 12 hours

›Monitor for hypotension

›Avoid immediate release high dose hypotension risk

›Portable hyperbaric chamber if descent delayed

›Repeat sessions as bridge to evacuation

›Other pulmonary vasodilators in selected cases

›PDE5 inhibitor prophylaxis or adjunct

›Tadalafil PO 10 mg every 12 hours for HAPE prone individuals

›Sildenafil PO 50 mg every 8 hours alternative

›Inhaled beta agonist prophylaxis selected

›Salmeterol inhaled 125 micrograms every 12 hours adjunct when other options limited

›Diuretics and antibiotics caveats

›Diuretics generally avoided

›Intravascular depletion risk

›HAPE is noncardiogenic

›Antibiotics only if infection suspicion

›Fever and purulent sputum

›Focal consolidation on imaging

Prevention and acclimatization

›Ascent strategy

›Sleeping altitude gain limits

›Gradual ascent

›Rest day every 3 to 4 days at higher altitude

›High risk patient strategy

›Lower initial sleeping altitude

›Conservative itinerary

›Acetazolamide prophylaxis

›Initiate 24 hours before ascent if possible

›Acetazolamide PO 125 mg every 12 hours

›Continue for 48 hours after highest sleeping altitude reached

›Dexamethasone prophylaxis when acetazolamide not tolerated

›Dexamethasone PO 2 mg every 6 hours

›Dexamethasone PO 4 mg every 12 hours alternative

›HAPE recurrence prophylaxis

›Nifedipine extended release PO 30 mg every 12 hours during ascent for known HAPE susceptibility

›Tadalafil PO 10 mg every 12 hours alternative

Evidence levels and guideline framing

›Evidence statement mapping

›Descent is first line for HACE and HAPE

›Class I recommendation based on expert consensus

›ACEP Level C style consensus grading when applied

›Oxygen is first line adjunct for HACE and HAPE

›Class I recommendation based on expert consensus

›ACEP Level C style consensus grading when applied

›Dexamethasone for HACE

›Class I recommendation based on guideline consensus

›Nifedipine for HAPE when oxygen limited

›Class IIa recommendation based on guideline consensus

09Special Populations/sp32

Pregnancy

›Pregnancy considerations

›Maternal fetal risk

›Hypoxemia risk for fetus

›Lower threshold for descent

›Medication considerations

›Acetazolamide risk benefit discussion

›Dexamethasone use for maternal indication when severe illness

›Disposition bias

›Hospital evaluation for moderate to severe symptoms

›Obstetric consultation when viable gestation

Geriatric

›Older adult considerations

›Comorbidity burden

›Cardiac disease mimic risk

›Pulmonary disease baseline limitation

›Medication adverse effects

›Nifedipine hypotension risk higher

›Polypharmacy interactions

›Disposition bias

›Lower threshold for admission

›Early imaging for alternative diagnoses

Pediatrics

›Pediatric considerations

›Presentation differences

›Irritability as mental status change

›Poor feeding

›Weight based dosing

›Acetazolamide prophylaxis 2.5 mg/kg per dose every 12 hours

›Maximum acetazolamide 125 mg per dose for prophylaxis common practice

›Dexamethasone dosing

›Dexamethasone 0.15 mg/kg per dose every 6 hours for severe illness

›Maximum dexamethasone 4 mg per dose typical

›Safety

›Early assisted descent for any ataxia or lethargy

10Background/b35

Epidemiology

›Frequency and patterns

›Acute mountain sickness common above 2500 m

›Incidence increases with rapid ascent and higher sleeping altitude

›High altitude cerebral edema uncommon

›Usually progression from severe AMS

›High altitude pulmonary edema uncommon

›Higher risk with prior HAPE history

Pathophysiology

›Mechanisms

›Hypobaric hypoxia

›Lower inspired oxygen partial pressure

›Hyperventilation and respiratory alkalosis

›AMS and HACE pathway

›Neurohormonal and inflammatory responses

›Vasogenic edema contribution

›HAPE pathway

›Hypoxic pulmonary vasoconstriction

›Uneven pulmonary vascular response

›High pulmonary artery pressures

›Capillary leak noncardiogenic edema

Therapeutic Considerations

›Treatment rationale

›Descent increases inspired oxygen pressure

›Rapid physiologic reversal

›Addresses root hypoxia driver

›Oxygen increases alveolar oxygen pressure

›Decreases hypoxic pulmonary vasoconstriction

›Reduces cerebral hypoxia burden

›Acetazolamide enhances acclimatization

›Carbonic anhydrase inhibition

›Metabolic acidosis stimulus for ventilation

›Dexamethasone reduces symptoms and edema risk

›Anti inflammatory effects

›Symptom improvement bridge to descent

›Nifedipine reduces pulmonary artery pressure

›Pulmonary vasodilation

›Improves oxygenation in HAPE

11Patient Discharge Instructions/pdi21

copy discharge instructions

›Discharge guidance

›Activity and altitude

›No further ascent until symptoms fully resolved

›Rest day at same altitude after resolution

›Medications

›Acetazolamide continuation plan if started

›Dexamethasone stop plan with caution for rebound

›Hydration and sleep

›Drink to thirst

›Avoid alcohol and sedatives

›Return to urgent care or emergency

›Worsening headache despite rest and medication

›New vomiting or inability to keep fluids down

›Any ataxia or difficulty walking straight

›Confusion or unusual sleepiness

›Shortness of breath at rest

›Chest tightness or cough worsening

›Blue lips or severe weakness

›Follow up

›Travel medicine or primary care review before next high altitude trip

›HAPE or HACE history flagged for future prophylaxis planning

12References/r7

Clinical guidelines and consensus

›Key guideline sources

›Wilderness Medical Society clinical practice guidelines for prevention and treatment of acute altitude illness

›UIAA and ISMM consensus statements on altitude illness recognition and management

Evidence based sources

›Foundational evidence and reviews

›High altitude cerebral edema and pulmonary edema clinical reviews in peer reviewed emergency and wilderness medicine literature

›Acetazolamide randomized trials for AMS prevention

›Nifedipine studies for HAPE treatment and prophylaxis

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed June 16, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.