HACE EVALUATION

HACE generally presents as a progression from AMS, although isolated HACE presentations have been reported. HACE is a clinical diagnosis and classically presents with headache, altered mental status and ataxia. The international criteria for HACE diagnosis are defined as the onset of ataxia OR altered mental status in the presence of acute mountain sickness; or the onset of ataxia AND altered mental status without the presence of acute mountain sickness. Symptoms are secondary to encephalopathy and can include behavioral changes, personality changes, apathy, drowsiness, confusion, social withdrawal, and stupor. Raised intracranial pressure can lead to cranial nerve three and six palsies. Other focal neurological deficits are rare and should prompt investigation towards other pathology. Differential diagnosis for HACE should include hypoglycemia, hyponatremia, hypothermia, hyperthermia, encephalitis/meningitis, postictal state, complex migraine, stroke, psychosis, intracranial hemorrhage, traumatic brain injury, shock, carbon monoxide poisoning, and toxidrome secondary to ingestion/exposure. An appropriate history, neurologic exam, and mental status exam are important for making this diagnosis.

HACE PREVENTION

Mission planning, pre-acclimatization strategy, nutrition, and hydration are discussed above and will mitigate the incidence and severity of HACE. The general approach to HACE prevention mirrors AMS prevention.

Acetazolamide: See AMS prevention recommendation.

Dexamethasone: See AMS prevention recommendation.

HACE TREATMENT

Descent: HACE leads to high mortality and morbidity. Descent to the lowest possible altitude in the most expeditious manner should be of the highest priority until symptoms fully resolve.4,17

Oxygen: If available, oxygen should be given continuously, titrating to an SpO2>90%. Rapid evacuation should not be delayed for oxygen therapy.

Portable hyperbaric chambers: Utilize a PHC to aggressively treat the patient in conjunction with oxygen if it does not delay evacuation or as a temporizing measure until evacuation becomes available. Compress chamber to the maximum pressure the chamber is designed to sustain. Continue to coordinate for emergent evacuation while the patient is in the hyperbaric chamber. Be aware that once a patient is in the chamber, there will be limited ability for repeat physical exams, additional treatments, and patient movement.3,17,36

Acetazolamide: In HACE, acetazolamide should be used as an adjunct to dexamethasone. Treat with acetazolamide at the same doses recommended for AMS therapy.17

Dexamethasone: Dexamethasone should be given to all individuals with HACE. Dosing for HACE treatment is 8mg IM/IV/orally followed by 4mg every 6 hours until asymptomatic. Given the high morbidity and mortality and lack of data on pediatric cases, dexamethasone is recommended for pediatric cases of HACE at a dose of 0.15mg/kg IM/IV/orally every 6 hours (max 4mg per dose).17,37