See: [Cameron - Altitude illness](x-devonthink-item://10DC3BB1-027C-40D6-BDB3-4AF0C6B160E6?page=799) [Dunn - High Altitude illness](x-devonthink-item://685E9AB2-6BDC-446A-BA6A-AED4CF66BF29) see also: > [!Key Points] > - the high altitude syndromes are a clinical diagnosis > - acute mountain sickness and high altitude cerebral oedema represent stages along a continuum owing to cerebral vasodilation and cerebral oedema, while high altitue pulm oedema minifests in the lungs > - **descent** is the single best tx for all > - *dexamethasone* for AMS/HACE, *nifedipine* for HAPE > - ppx with low dose acetazolamide > - [mnemonic::] PPx: *Acetazolamide* 125mg BD commenced 24 hours prior to ascent and discontinued after acclimitisation occurs - decreases proximal tubular reabsorption of bicarbonate leading to a loss of bicarbonate. This results in a towards metabolic acidosis which then helps further increase ventilation (and hence increases PaO2) - also helps with periodic breathing - avoid EtOH and consume high carb diet - increases resp quotient , ↑ alveolar pO2, may decrease risk of AMS by 30% > - All altitude sickness episodes need descent and oxygen as primary treatments. > - Hyperbaric treatment for those when descent is not possible. > - Acute mountain sickness – Acetazolamie 250mg PO twice daily. > - High-Altitude cerebral edema - Dexamethasone 8mg PO followed by 4mg four times a day. > - High-Altitude Pulmonary edema - Nifedipine SR 10mg initially then followed by 20-30mg twice a day. # Acute mountain sickness - **headache** is the primary symptom - fatigue out of proportion to recent activity level - insomnia - nausea - dysponea no examination findings ; signs only develop if someone gets high altitude cerebral oedema *Tx*: - hydration, rest, analgesia, symptoms usually pass in 2-3 days as acclimitisation occurs - **Descent** is best tx for all altitude illness, ↓ by 300m ASAP - oxygen 1-2L/min until sx resolve , but O2 doesn't fix everything - hyperbaric therapy eg Gamow portable pressure bag can also be used) - can try acetazolamide 250mg BD if not already used for PPx # High altitude cerebral oedema - progression of neurological signs and sx in setting of acute mountain sickness - marked truncal ataxia - lethargy, ALOC, coma - usually progresses over 1-3 days Tx: - **dexamethasone** 8mg stat then 4mg QID - immediate descent >1000m or evacuation - O2 maintain sats >90% # High altitude pulm oedema - non-cardiogenic pulmonary oedema - hydrostatic pulm oedema - possibly due to impaired sodium driven clearance of alveolar fluid - high pulm art pressure - causes the most deaths from altitude Sx: - dysponea at rest is a warning sign - tachycardia - cyanosis - crepetations, especially R middle llobe - Tx: - descent >500-1000 m or evacuate with minimal exertion - O2 aim sats >90% - **nifedipine** 10 mg sublingually stat then 20mg-30mg SR TDS if oxygen or descent not available --- # Other altitude illness ## Retinal haemorrhages - usually altitudes >5000m - fairly common - do not affect vision - rarel affect macula - no tx known to be effective - clear spontaneiously in 1-2 weeks ## Snow blindness - ultraviolet keratitis - - UV radiation ↑ 5% per 300m increase in altitude - healing within 24 hours