Notes on Mountain Sickness
by Kenneth Lyen
I was horrified to read that Singaporean Amy Wong died of mountain sickness on 26 May 2017, while she was en route to the base camp of Mt Everest.
In 2012, one of my medical students was doing an elective in Nepal and decided to climb Mt Everest. She developed mountain sickness, became unconscious, and had to be helicopter flown down to a lower altitude. Luckily she survived.
In 2016, the Himalayan Times reported 17 climbers were evacuated, and 400 complained of altitude sickness during the annual Mt Everest climbing season.
In 2019, there were 11 deaths or persons missing while climbing Mt Everest.
This means that many mountain climbers may not be fully aware of the dangers of mountain sickness and did not take sufficient precautionary measures.
What is mountain sickness?
Mountain or altitude sickness is a condition caused by acute low oxygen atmospheric pressure on the brain and lungs that occurs when climbing high mountains, usually above 2,400 metres or 8,000 feet. The faster one climbs, the greater the risk of mountain sickness. This is a potentially fatal illness and needs urgent treatment.
Mild to moderate mountain sickness symptoms: (most common):
-
Headache
-
Dizziness or light-headedness
-
Irritability
-
Loss of appetite
-
Nausea with or without vomiting
-
Fatigue
-
Difficulty sleeping
-
Rapid pulse and heart rate
-
Shortness of breath with exertion
Severe acute mountain sickness symptoms:
-
Blue lips, blue skin color (cyanosis), this may be preceded by pale or gray skin complexion
-
Chest tightness
-
Shortness of breath even at rest
-
Cough, including coughing up blood
-
Decreased consciousness or withdrawal from social interaction
-
Inability to walk or walk in a straight line
-
Pins and needles
On Examination:
-
Swelling of hands, feet, or face
-
Rapid breathing
-
Rapid heart beat
-
Crackling sounds heard in the lungs using a stethoscope (crepitations)
-
Retinal hemorrhage (bleeding In the back of the eyes)
Investigations:
-
Chest Xray: pulmonary edema
-
Electrocardiogram
-
Arterial blood gas: this shows low oxygen saturation, low carbon dioxide, and alkalosis
-
Brain scan (CT): cerebral edema
Treatment:
Early diagnosis leads to early recovery and minimises complications.
-
Descend to a lower altitude rapidly
-
Give oxygen by mask
-
Admit to hospital
-
Acetazolamide (Diamox): this medicine may be taken 2 weeks before climbing high altitudes. Drink more fluids and avoid alcohol.
-
Nifedipine, a high blood pressure medicine prevents lung edema
-
Salmeterol, a beta agonist that comes as an inhaler, opens the airways, and helps breathing
-
Dexamethasone (Decadron) may help reduce cerebral edema or swelling of the brain.
-
Portable hyperbaric chambers that simulate lower altitude atmospheric pressures can be very helpful especially when bad weather precludes descent.
-
Mechanical ventilation in severe cases
Current data does not support the use of sildenafil, a phosphodiesterase inhibitor which increases blood flow to the lungs for pulmonary oxygenation.
Prognosis:
Most cases are mild. Symptoms improve quickly when you climb down the mountain to a lower altitude.
Severe cases may result in death due to lung problems or brain swelling, called cerebral edema.
In remote locations, emergency evacuation may not be possible, or treatment may be delayed. This can have a negative effect on your outcome.
The outlook depends on the rate of descent once symptoms begin. Some individuals are more prone to developing altitude-related sickness and may not respond as well.
Possible Complications:
-
Coma
-
Fluid in the lungs (pulmonary edema)
-
Swelling of the brain (cerebral edema), which can lead to seizures, mental changes, or permanent damage to the nervous system
-
Death
Prevention:
Mountain sickness can be prevented by the following measures.
-
Ascend the mountain more slowly to acclimatize to the lower atmospheric oxygen pressure. Stop for a day or two of rest for every 600 meters (2,000 feet) of climb above 2,400 meters (8,000 feet).
-
Take acetazolamide 2 weeks before climbing (but this works in only about 50% of cases)
-
Altitude tent: these tents have lower percentage of oxygen while maintaining normal air pressure
What is the cause (pathophysiology) of mountain sickness?
There are two major manifestations of mountain sickness: cerebral edema, and pulmonary edema.
The exact pathophysiology of the high altitude cerebral edema is unknown. The current hypothesis is that the oxygen in the blood causes the blood to flow faster and there is a release of some neurohumoral factors, both of which cause in leakage of plasma from the small blood vessels (capillaries). This leakage results in fluid in the brain substance (edema), which increase the pressure inside the brain and impairs the diffusion of oxygen from the blood to the nerve cells.
As for the lungs, the body’s response to the low oxygen pressure is the increase the breathing rate which is triggered by oxygen sensing cells in the carotid artery. This increased ventilation produces higher oxygen delivery to the air sacs and flushes out the carbon dioxide (CO2), thus lowering the CO2 in the blood. The lower CO2 makes the blood more alkali (alkalosis) which results in the respiratory center in the brain to reduce ventilation.
Taken from Wikipedia: The physiology of altitude sickness is based on the following equation:
Vgas=A/TDk(P1−P2)
Where Vgas is the diffusion rate, A is the area of the lung, T is the thickness of the lung membranes, Dk(P1−P2) is the difference in partial pressure of gases - but most importantly CO2 and O2-where in high altitudes the partial pressure differences for O2 are low and the differences in partial pressures for CO2 are high. Thus CO2 will have a high diffusion out and O2 will have a low diffusion through the alveolar membranes and into the blood.
The body's response to high altitude includes the following:
-
↑ Erythropoietin → ↑ hematocrit and hemoglobin
-
↑ 2,3-BPG (allows ↑ release of O2 and a right shift on the Hb-O2 disassociation curve)
-
↑ kidney excretion of bicarbonate (use of acetazolamide can augment for treatment)
-
Chronic hypoxic pulmonary vasoconstriction (can cause right ventricular hypertrophy)
Mt Everest New Rules
In 2019, there were at least 11 deaths or missing persons climbing Mt Everest. The government of Nepal has instituted new rules for anyone wanting to climb Mt Everest. To obtain a compulsory permit:
a) Applicants must already have climbed a Nepali peak of at least 6,500m (21,325ft).
b) They must provide a certificate of physical fitness and employ experienced guides.
c) It is proposed a fee of at least US$35,000 for those who want to climb Everest, and $20,000 for other Nepali mountains higher than 8,000m.
d) Climbers must take out an insurance policy of at least US$15,000.
References
High Altitude Illness: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3678789/
Acetazolamide: https://www.ncbi.nlm.nih.gov/pubmed/24146388
Nifedipine: https://www.ncbi.nlm.nih.gov/pubmed/2573760
Salmeterol: https://www.ncbi.nlm.nih.gov/pubmed/12023995
Dexamethasone: https://www.ncbi.nlm.nih.gov/pubmed/2920585
Sildenafil: https://www.ncbi.nlm.nih.gov/pubmed/21962063
Mt Everest new rules: https://www.bbc.com/news/world-asia-49348071
Written by Kenneth Lyen 17 December 2019, updated 20 June 2020
%20a.jpg)