Altitude Headache

Altitude headache (high altitude headache) is a headache that develops within 24 hours of ascent to 2500 metres or higher. It is the cardinal symptom of acute mountain sickness and results from hypobaric hypoxia, cerebral vasodilatation, raised intracranial pressure, and fluid shifts.

• Acute mountain sickness is diagnosed by headache plus at least one of: gastrointestinal upset (anorexia, nausea or vomiting), fatigue or weakness, dizziness or light headedness, and sleep disturbance, after arriving at altitude; severity is graded using the Lake Louise score (3 or more with headache = acute mountain sickness).
• Incidence: about 25 percent at 2500 to 3000 metres, rising to 50 to 75 percent above 4500 metres with rapid ascent; relevant to climbers of Mount Kenya and Kilimanjaro, who ascend rapidly.
• Risk factors: rapid ascent (sleeping elevation gain over 500 metres a day above 3000 metres), starting altitude low, prior altitude illness, migraine history, exertion, dehydration, alcohol, sleeping pills, and cold; fitness and age do not protect.
• Severe forms: high altitude cerebral oedema (ataxia, altered consciousness) and high altitude pulmonary oedema (dyspnoea, cough, cyanosis), which are life threatening.

• Bilateral frontal or generalised throbbing headache starting 6 to 12 hours after ascent, worse at night and on waking, with exertion, coughing, straining and bending; improved by rest and analgesics in mild cases.
• Associated: loss of appetite, nausea, vomiting, fatigue, light headedness, poor sleep, peripheral oedema of face or hands, reduced urine output.
• Severity: mild (Lake Louise score 3 to 5), moderate (6 to 9), severe (10 to 15).
• High altitude cerebral oedema: headache not responding to analgesia, ataxia (inability to walk heel to toe), confusion, drowsiness, hallucinations, and coma; retinal haemorrhages may be seen.
• High altitude pulmonary oedema: breathlessness at rest, cough with frothy or pink sputum, crackles, reduced exercise tolerance, oxygen saturation markedly low for the altitude.
• Red flags: ataxia, altered mental state, severe breathlessness at rest, chest tightness, focal neurological deficit, seizure, and persistent vomiting.

• Clinical, based on recent ascent, symptoms, and Lake Louise score.
• Assess ataxia (heel to toe walking), consciousness, oxygen saturation (expected 85 to 90 percent at 3500 to 4500 metres; lower values with symptoms suggest oedema), respiratory rate, pulse, and lung examination.
• Capillary glucose to exclude hypoglycaemia; consider dehydration, hyponatraemia, carbon monoxide poisoning (from indoor stoves), and hypothermia.
• Differentials: dehydration headache, migraine, tension type headache, caffeine withdrawal, exhaustion, hangover, carbon monoxide poisoning, meningitis, stroke or intracranial haemorrhage, cerebral venous thrombosis, hypothermia, hyponatraemia, and infection (viral illness, pneumonia).

Mild acute mountain sickness (headache with minor symptoms)

• Stop ascending; rest at the same altitude until symptoms resolve (usually 24 to 48 hours); do not go higher with symptoms.
• Hydrate adequately (about 3 to 4 litres a day), light carbohydrate diet, avoid alcohol and sleeping pills.
• Analgesia: ibuprofen 400 to 600 mg orally every 8 hours with food, or paracetamol 1 g orally every 6 hours (maximum 4 g daily), or aspirin 650 to 900 mg; avoid opioids.
• Antiemetic: ondansetron 4 mg orally disintegrating tablet every 8 hours, or prochlorperazine 5 to 10 mg every 8 hours.
• Acetazolamide 125 to 250 mg orally twice daily speeds acclimatisation and treatment; reduces symptoms in 12 to 24 hours.

Moderate to severe acute mountain sickness

• Descend by at least 300 to 1000 metres (descent is the definitive treatment), accompanied; the patient should not descend alone.
• Dexamethasone 4 mg orally, intramuscularly or intravenously every 6 hours (8 mg first dose for severe symptoms) until symptoms resolve and for 24 hours after descent, then stop; can be used in combination with acetazolamide; do not use dexamethasone to continue ascending.
• Supplemental oxygen 1 to 2 L/min through nasal cannula, to saturation of over 90 percent; portable hyperbaric chamber (simulated descent of 1500 to 2000 metres for 2 to 4 hours) when descent is not possible.

High altitude cerebral oedema

• Immediate descent (at least 1000 metres or until symptoms improve), oxygen to saturation over 90 percent, dexamethasone 8 mg orally, intramuscularly or intravenously, then 4 mg every 6 hours; portable hyperbaric chamber if descent is delayed; evacuation to hospital.

High altitude pulmonary oedema

• Descend immediately (minimal exertion), oxygen 4 to 6 L/min then titrate, nifedipine modified release 30 mg orally twice daily (or 20 mg every 8 hours), portable hyperbaric chamber; consider tadalafil 10 mg twice daily or sildenafil 50 mg every 8 hours if nifedipine is not available; avoid diuretics and morphine.

Prevention

• Gradual ascent: above 3000 metres, increase sleeping altitude by no more than 300 to 500 metres a day, with a rest day (no ascent) every 3 to 4 days; climb high, sleep low; avoid direct flights or drives to over 3000 metres.
• Acetazolamide 125 mg orally twice daily starting the day before ascent and continuing for 2 days at the highest altitude (or until descent begins); for rapid ascent or prior severe illness, 250 mg twice daily. Side effects: paraesthesia of fingers and lips, polyuria, taste alteration of fizzy drinks, rarely kidney stones and metabolic acidosis; avoid in sulfonamide allergy, severe renal or liver disease, and the first trimester of pregnancy.
• Alternatives: dexamethasone 2 mg every 6 hours or 4 mg every 12 hours (for short term use, for people intolerant of acetazolamide or for emergency rapid ascent); ibuprofen 600 mg three times daily reduces the incidence.
• Hydrate, eat carbohydrate, avoid alcohol, sedatives and overexertion.
• Prior history of high altitude pulmonary oedema: nifedipine modified release 30 mg twice daily during ascent.

Follow up

• Reassess every few hours; do not ascend until symptom free for at least 24 hours (and off dexamethasone); seek medical review after severe illness.

Special groups

• Children: acetazolamide 2.5 mg/kg orally twice daily (maximum 125 mg a dose) for prevention or treatment; dexamethasone 0.15 mg/kg every 6 hours (maximum 4 mg a dose); avoid aspirin; children cannot reliably report symptoms, so watch for irritability, poor feeding and vomiting.
• Pregnancy: limit sleeping altitude to below about 3000 metres; avoid acetazolamide in the first trimester and weigh risks later; descend for any symptoms.