High Altitude Cerebral Edema (HACE) is the most perilous and advanced manifestation of altitude sickness. While its exact mechanism is not fully understood, it arises due to oxygen deprivation, leading to brain swelling and compression against the enclosing cranial bones. This pressure on brain tissue results in the development of life-threatening symptoms, ultimately culminating in the displacement of the brainstem – the region controlling vital life functions – and subsequent fatality.
HACE is frequently accompanied by its counterpart, High Altitude Pulmonary Edema (HAPE), making them the two most formidable adversaries at high elevations. Symptoms typically manifest around 24 hours after ascending to a new altitude. Some individuals, but not all, may experience acute mountain sickness symptoms beforehand, such as headaches, insomnia, loss of appetite, and nausea. Given this, venturing to higher altitudes should be strictly avoided in the presence of moderate to severe mountain sickness symptoms.
Individuals affected by HACE often exhibit intense headaches, appear agitated and irrational, experience increased body temperature, and may reassure others that they are fine. Rapid equilibrium disturbances occur as the brain region responsible for balance is among the earliest to be affected. Notably, a low blood pulse oximetry is characteristic.
How to recognize HACE?
Jak rozpoznać HACE?
If HACE is suspected in a fellow traveler, assessing their blood oxygen saturation and conducting three tests is essential:
- Walking in a straight line
- Standing upright with extended arms held in front and eyes first open, then closed
- Touching the nose with both index fingers alternately, first with eyes open, then closed
Failure to pass any of these tests (stumbling, inability to walk straight, failure to touch nose with a finger), coupled with low pulse oximetry, strongly indicates HACE.
Initial treatment of HACE
As all altitude-related illnesses stem from oxygen deprivation, addressing this cause is paramount. Administering oxygen is the first step – organized trips and Himalayan lodges should be equipped with emergency oxygen cylinders and delivery systems. Oxygen flow (L/min) should be adjusted to achieve saturation levels >95%.
Seek medical assistance and prepare the patient for evacuation, ensuring the descent of at least 500-1000 m or immediate transfer to hospital. Helicopter rescue is preferable but if it is not possible consider evacuation on foot, preferably in a lying position on improvised stretchers with the head slightly elevated. The patient must remain on oxygen during this time. Alternatively, if oxygen is unavailable, the patient can be placed in a hyperbaric bag (Gamow bag) that simulates conditions at a lower altitude. Constant monitoring, pulse oximetry tracking, and consistent inflation are essential.
While awaiting rescue, administer a medication to reduce intracranial pressure – the steroid Dexamethasone at a dose of 8 mg in tablet or in pre-prepared injection form. Repeat the dose every 6 hours (4mg, or 8mg if only the latter is available) to avoid the rebound effect. Immediately after diagnosing HACE, we should also administer Acetazolamide at a dose of 250 mg.
Algorithm for Suspected High Altitude Cerebral Edema (HACE):
- Suspect HACE if the climber appears agitated, confused, experiences headaches, shows balance issues, and has low pulse oximetry.
- If HACE is suspected, ask the climber to perform one of three tests (walking in a straight line, standing with arms extended, attempting to touch nose with his fingers). If he fails or refuses, and low pulse oximetry is present, diagnose HACE.
- Administer oxygen, adjusting the flow based on saturation, aiming for >90-95%.
- Seek help and consider helicopter evacuation to a hospital. If impossible, evacuate on foot in a lying position or as terrain allows.
- Administer the intracranial pressure-reducing steroid Dexamethasone (8mg) – repeat every 6 hours. Keep the patient on oxygen or in a hyperbaric bag while awaiting rescue. Administer Acetazolamide at a dose of 250 mg.
HACE demands immediate action, as it can rapidly lead to fatality. Evacuation to lower altitudes and oxygen therapy are the only effective treatments.
Note: This article is intended for informational purposes only and should not be considered a substitute for professional medical advice.
Base on:
Jensen JD, Vincent AL. High Altitude Cerebral Edema. [Updated 2022 Jul 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430916/
Luks, A.M., Ainslie, P.N., Lawley, J.S., Roach, R.C., & Simonson, T.S. (2021). Ward, Milledge and West’s High Altitude Medicine and Physiology (6th ed.). CRC Press. https://doi.org/10.1201/9780429444333