At Indiahikes, we have been trekking at high altitudes for over 15 years, taking over 20,000 trekkers every year. We have been lucky enough to observe a huge cross-section of trekkers, their medical well-being at high altitudes, and their physiological responses to altitude. 

Among the many issues we see is High Altitude Cerebral Edema, an advanced form of Acute Mountain Sickness. 

We have seen a few cases of High Altitude Cerebral Edema in our early years, but have cracked down on how to avoid it over several years of training and experience. 

So in this post, I am sharing what HACE is, what it looks like, its symptoms, treatment, and prevention.

What is high-altitude cerebral edema?

High-Altitude Cerebral Edema is an advanced form of Acute Mountain Sickness. When left untreated, Acute Mountain Sickness could lead to HACE.  

HACE occurs when the blood vessels in the brain dilate, resulting in the accumulation of fluids.

Cerebral: related to brain

Edema is the swelling caused by too much fluid trapped in a particular body tissue.
The danger: HACE can turn fatal if not given immediate attention & treatment.

Symptoms of HACE: What does HACE look like?

One of the main signs of HACE is an extreme headache. It is not a normal kind of headache. It feels different. (Again, please note: some people might not feel a headache). Another symptom is confusion.

In addition to this, you will see an altered nature of behaviour. So what does HACE look like?

• A person affected with HACE struggles with mind & body coordination. The phenomenon is called Ataxia. For example, in many cases, a HACE-affected patient struggles with their shoelaces, they won’t be able to walk in a straight line if you ask them to, or they might not be able to draw a circle.
• They might also be hallucinating.
• They may sound confused.
• They might have no idea that something is off with them. It sometimes requires another person to identify and treat the symptoms.

How to treat high-altitude cerebral edema?

If you suspect someone has HACE - immediately administer dexamethasone. It brings down the edema. If you have oxygen, administer it immediately. Once you give these two, descend.

The Rule of Thumb Says: Descend Descend Descend. 

You should start your descent as soon as you identify the symptoms of HACE. It is the most straightforward way to treat HACE. 

Certain medications help curb symptoms of HACE while you start your descent: Diamox and Dexamethasone. (This treatment is an addition to descent, and is not a standalone treatment.)

How should you take the medicine?

Start with a 500 mg dose of Diamox and around 8mg of Dexamethasone intravenously. This combination will reduce inflammation and stop your brain from swelling, giving you a window of a few hours to get yourself out of that altitude. 

Try to reach down to an altitude of around 8,000 ft in the next six hours. If you fail to do it, repeat the same dosage of Diamox & Dexamethasone.

Around 8000 ft. is a safe enough height. Lower the dosage only when the patient is showing some improvement.

If you notice symptoms fading away, lower your dosage of Dexamethasone to 4 mg (orally), followed by 2 mg (orally) every 6 hours. Dex needs to be weaned away and cannot be stopped immediately.

There is one very important thing, there should always be someone accompanying the HACE-affected trekker/traveller while they are climbing down. It is very risky leaving them alone.

If you are on a trek with Indiahikes, we take all the safety measures to bring you down to safety and provide you with the required professional medical attention as soon as you reach the base camp.

How to prevent high-altitude cerebral edema? What can you do? How can you prepare?

Our staunch belief while trekking at high altitudes is that prevention is better than cure. Here are a few preventive measures to avoid HACE: 

• Acclimatise well: Plan your itinerary well. Give your body enough time to acclimatise well to the altitude.
• Get on a preventive course of Diamox, especially if you’re climbing higher than 12,000 ft. Here’s a detailed article on how Diamox deals with AMS.
• Work on your fitness. Indeed, a fit trekker can also get affected by HACE but physical fitness aids better acclimatisation, which helps avoid AMS and HACE. (This small clip will help you get a better understanding of how it works.) 
• Hydrate yourself well and eat a good diet. 
• Do not consume alcohol. Keep your diet simple & balanced.

I am attaching a detailed article on preventing altitude sickness. Give it a thorough read.
Having said that, if you are trekking with Indiahikes, you are not likely to face an advanced form of AMS / HACE, since we go out of our way with preventive measures. We aim to identify the mildest symptoms of AMS and treat it so that we are not in a state of emergency deep inside the mountains.

When is the need for evacuation?

The moment you identify symptoms of HACE, you must start evacuation. It’s already too late. For as long as you’re at the same high altitude, your brain will continue to accumulate fluids. Even if you’re on medication to treat HACE, the medicines are a mere way of buying time for you to descend.  

If you are on a trek with Indiahikes, we take evacuation calls promptly. We have manpower, medical resources, and stretchers to bring you back to a safe altitude. While we ensure our own trekkers don’t reach situations where they need such emergency evacuations, our teams have led rescue operations for multiple other organisations in the mountains. 

We cannot repeat enough that safety is in prevention. The Indian Himalayas do not allow easy evacuations. Heli rescues are unheard of on most treks. It’s extremely resource-intensive to evacuate anyone from these regions and often the weather and terrain are not on your side.  

It’s important to identify symptoms of AMS at the earliest and treat them.

How safe are you on a trek with Indiahikes?

Between January 2017 and September 2024, we have seen just two cases of HACE on Indiahikes treks. This is not by chance. Our trek leaders take action promptly against AMS before it develops into HACE.

As mentioned earlier, we take all mandatory steps to ensure the safety of the trekkers. Multiple procedures go behind the curtains. It starts even before the trek starts.

• We check trekkers’ Blood pressure on the first day to ensure it is within an acceptable standard at high altitudes.
• We record oximeter recordings thrice every day and ensure it never gets down to our cut-off numbers.
• All the trek leaders carry with them life-saving drugs to treat AMS, HAPE, and HACE. They are trained on how to treat trekkers with these medications. 
• For an emergency HACE case, our trek leaders carry oxygen cylinders with them.
• All campsites are equipped with a bigger oxygen cylinder. We are also equipped with stretchers for severe case evacuation.
• The most important thing that matters is the observation. Our trek leaders observe trekkers throughout & assist them as per the situation demands.
• Our trek leaders, staff, and slope managers regularly undergo extensive training to manage any medical emergency cases.

Our belief in the mountains is simple: better safe than sorry. The mountains are always there for you to come back and trek. It cannot be at the cost of your health. 

Indiahikes Trek Leaders are casually called “doctors in the mountains” by many of our trekkers. They know high altitude issues and medications like the back of their hand. You can rest assured that you’re in safe hands with them. 

In conclusion: 

I hope this article helped you understand what High-altitude cerebral edema looks like in the mountains and how to deal with it. It is helpful for anyone going to higher altitudes & not just for trekkers. Make sure you bookmark it. 

If you have any questions, get in touch with me by dropping in your comments.

FREQUENTLY ASKED QUESTIONS

1) Why does high-altitude cause cerebral edema?

HACE occurs when blood vessels in the brain dilate resulting in the accumulation of fluids. It happens beause your body is unable to acclimatise well to the higher-altitude. It starts as AMS, & if left untreated, can turn to HACE. 

2) At what altitude does AMS occur?

Acute mountain sickness generally occurs above 8000ft. It happens because your body is unable to acclimatise to higher altitudes. Again, there’s no definite number. You can also feel the symptoms of AMS below 8000ft.

3) How to prevent high altitude cerebral edema?

To prevent high altitude cerebral edema, ensure adequate time to acclimatise to high altitude well. Most importantly, plan your itinerary well, ensure you’re fit and hydrated and be on a preventive course of Diamox if you’re climbing high quickly, especially on forced ascents like in the Himalayas.