AMS AMS is defined as having a headache in the setting of at least one of four other symptoms: nausea/vomiting, fatigue, difficulty sleeping, and dizziness Vasogenic edema is believed to explain the pathophysiology underlying AMS, with clinical progression to encephalopathy occurring as cerebral edema, or HACE, worsens HAPE is the most common cause of death when exposed to high altitudes; younger individuals may be more susceptible to HAPE because of immature control of breathing and frequent respiratory illnesses Pulmonary vascular leak leads to elevated pulmonary artery pressures Pediatric patients with HAPE should undergo evaluation for cardiopulmonary abnormalities such as structural heart disease and pulmonary hypertension Triage and Initial Assessment The recognition of altitude illness depends mainly on a compatible history of exposure to high altitude Children may be at risk for high-altitude illness when traveling from low altitude to high altitude (sporting events, family vacations, school activities), returning to high altitude after traveling to low altitude, or when having a respiratory illness at high altitude without changes in elevation Intermediate altitude is defined as 1,520 to 2,440 m (5,000 to 8,000 ft), high altitude as 2,440 to 4,270 m (8,000 to 14,000 ft), very high altitude as 4,270 to 5,490 m (14,000 to 18,000 ft) and extreme altitude as greater than 5,490 m (18,000 ft) Initial Assessment The diagnosis of altitude illness in children can be challenging, especially in the preverbal age group Factors that affect whether an individual gets sick include the altitude itself, rate of ascent, the altitude where sleeping occurs routinely, and the individual’s physiology Information regarding any potential genetic basis of high-altitude illness is limited However, from an anatomical perspective, those who are able to tolerate brain swelling (i.e., the elderly whose brain size diminishes with age, or infants with their immature sutures and open fontanelles) are less susceptible to altitude illnesses Management and Diagnostic Studies Treatment for HAH and mild AMS includes stopping the ascent and acclimatizing at the current altitude; acetazolamide given early will hasten this process and remains the best choice for prevention of AMS Analgesics, hydration, and antiemetics are also given for supportive care Phosphodiesterase inhibitors such as sildenafil have shown promise in prevention of HAPE in patients with AMS