[Acute high-altitude illnesses - Definition, Prophylaxis, Therapy].

Acute altitude illnesses are significant can occur in unacclimatized individuals at altitudes above 2,500 meters. They essentially comprise three clinical pictures: Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE), which can manifest alone or in combination. All are triggered by hypobaric hypoxia, with individual predisposition, pre-existing medical comorbidities and in particular ascent rate and destination altitude influencing risk. AMS is the most common, presenting with headache, nausea, dizziness, and fatigue. Prevention includes slow ascent, pre-acclimatization, and eventually acetazolamide or dexamethasone. In severe cases, descent, oxygen therapy, and dexamethasone are key. HACE is considered a life-threatening complication of AMS with ataxia, altered consciousness, and neurological deficits. Pathophysiologically, vasogenic edema, hypoxic cell injury, and disturbed cerebrospinal fluid dynamics play a role. Treatment also includes descent, oxygen therapy, and dexamethasone. HAPE is a non-cardiogenic pulmonary edema due to an excessive hypoxic pulmonary vasoconstriction with consecutive elevation of pulmonary artery pressure and increased capillary pressure. Symptoms include dyspnea and cough; clinically, cyanosis and crackles are evident. Treatment requires descent, oxygen therapy, and possibly nifedipine or PDE-5-inhibitors. If untreated, HACE and HAPE progress rapidly and can be fatal. Prevention, early recognition and immediate treatment are crucial.