High Altitude illness

1. Acute mountain sickness
2. High altitude cerebral oedema
3. High altitude pulmonary oedema

Definition: symptoms occur within 4 days of ascending to > 2500 m.

C/F: headache, fatigue, anorexia, nausea and vomiting, insomnia and dizziness. 

Pathophysiology: hypoxia → vasodilation →increased capillary hydrostatic pressure →raised ICP

Management:

• Rest 
• Simple analgesia; 
• Medication 

1. Acetazolamide: 

• for prophylaxis: 125 mg twice daily 
• for treatment: 250 mg three times daily 

1. Dexamethasone: 8 mg

• Symptoms usually resolve after 1–3 days at a stable altitude

• if symptoms persist: need to descend → definitive treatment

Risk: 

• Progression to cerebral oedema (HACE). 

Clinical features: 

• a severe sequela of AMS
• ataxia, cognitive impairment in addition to the symptoms of AMS
• Untreated HACE can progress to coma within 24 hours. 

Management:

• Descent is essential 
• Dexamethasone (8 mg stat, followed by 4 mg four times daily). 
• If descent is not possible: portable hyperbaric chambers, such as a Gamow bag. 

• occurs within 4 days after ascent above 2500 m 
• leading cause of mortality from high altitude illness. 
• Vasoconstriction → pulmonary hypertension 

Clinical features:

• Initial: dry cough, exertional dyspnoea, extreme fatigue. 
• Later: productive cough with haemoptysis and orthopnoea; tachycardia, tachypnoea, crepitations, fever
• CXR: diffuse alveolar oedema. 
• HAPE may occur without the preceding signs of AMS, 

Management 

• immediate descent (by a minimum of 1000 m) 
• oxygen administration: saturations > 90%. 
• if descent is delayed: portable hyperbaric chamber 

Prophylaxis: 

• Nifedipine (60 mg modified release divided into 2–3 doses) 

• starting 1 day before attempting ascent above 2500 m 
• continued for a further 5 days at altitude or until descent below 2500 m. 
• not effective for treatment 

SAQ. A 42-year-old male presented with exertional dyspnoea and fatigue with dry cough. On a query,  he gave a history of ascent 3000 m in the last 2 days.

1. Enumerate 4 physical findings pointing to diagnosis.

• Most likely HAPE
• Signs

1. Tachycardia, Tachypnoea at rest, 
2. Bibasal crepitations, 
3. Temperature high, 
4. SpO2 low, 
5. Cyanosis 

1. Write down management principles.

• immediate descent (by a minimum of 1000 m) 
• oxygen administration: saturations > 90%. 
• if descent is delayed: portable hyperbaric chamber