Acute mountain sickness or altitude sickness is a disease caused by physiological reactions of the human body resulting from exposure to low oxygen pressure.

SO WHAT HAPPENS WITH THE OXYGEN IN ALTITUDE?

The surrounding air in the atmosphere is composed of only 21% oxygen at sea level with an atmospheric pressure of 760 mmHg, while at high altitude the pressure is only 150 mmHg.

The air is heated and humidified creating an intrapulmonary partial pressure of 100 mmHg, this pressure is what saturates oxyhaemoglobin to between 96 and 98% normally.

At 5000 mts the atmospheric pressure is 350 mmHg which creates an oxygen pressure of only 50 mmHg which is half of what it is at sea level, however, respiratory mechanics saturates oxyhaemoglobin up to 84 %.

WHAT IS HYPOXIA?

Hypoxia is deficiency in the amount of oxygen reaching the tissues

 

WHAT HAPPENS ONCE I AM AT ALTITUDE?

Hypoxia will produce an energy and functional deficit in our body.

The physiological response of the body to adapt is the increased ventilatory and heart rate.

The result of this process is dehydration as the body is using everything it has to compensate for hypoxia, even at rest.

During the early stages of acclimatisation, alkalosis is combated by renal suppression of carbonic anhydrase and excretion of dilute alkaline urine and this tends to bring the blood pH to a normal value, then you will urinate more often

If the ascent is faster than the body’s adaptive response to the stress of hypobaric hypoxaemia, altitude-related pathological conditions occur, being one of the first sympotoms the headache.

Ions such as sodium and potassium are key to the transmission of nerve impulses, but they also play a role in the exchange of the intra- and extra-cellular environment, which is why they can polarise and depolarise the cells, you may experience this as feeling that your mind is not as sharp as it normally is.

However, in extreme conditions such as hypoxia we have a deficit of both, which in the case of sodium (Na) produces accumulation of liquid in the intercellular space which can be a catalyst for edema, while potassium (K) deficiency will cause diarrhoea, increased diuresis (more urine is passed), vomiting, dehydration, which leads to further loss of electrolytes from the organism.

AMS CAN LEAD TO TWO VERY DANGEROUS CONDITIONS:

– Altitude Pulmonary Edema (HAPE)

– High altitude cerebral oedema (HACE)

SYMPTOMS OF AMS

– Headache, which is an intense and persistent headache accompanied by a sensation of heaviness.

– Nausea, vomiting

– Fatigue, weakness (asthenia)

– vertigo – dizziness

– Sleep disturbances

Each of these symptoms will be referred by the patient at some point during the trip, either directly or indirectly, which is why the  acclimatization is fundamental.

Everything from headaches, hyperventilation, tiredness and appetite are indicators  for us to take preventive actions.

WHAT IS HIGH-ALTITUDE PULMONARY OEDEMA?  (HAPE)

Is the accumulation of liquid in the alveolar space due to exaggerated hypoxic pulmonary hypertension and altered elimination.

It is an inflammatory process with alveolar vasoconstriction reaction.

 

SYMPTOMS

– Cyanosis

– Dry cough

– Expulsion of reddish foam accompanied by coughing

– Reduced thoracic expansion in the respiratory movement

– Dyspnoea – Tachypnoea

– Continuous sweating

– Feeling of death – drowning

– Peripheral oedema – ankles and feet mainly

– Snoring and wheezing on all respiratory efforts

– Upright or tripod posture

WHAT IS ALTITUDE CEREBRAL OEDEMA? (HACE)

Cerebral vasodilatation due to hypoxia, also increased cerebral blood output leading to endocranial hypertension.

(HACE) SYMPTOMATOLOGY

– Headache

– Ataxia

– Decreased consciousness

– Disorientation.

 

 

HOW HIGH SHOULD MY OXYGEN SATURATION BE AT ALTITUDE?     

                  OXYGEN SATURATION

HEIGHT (metres)                      Oxygen saturation %

0             ………………………………..            98

2500      ……………………………….              93

3300      ………………………………                87

5000      ………………………………                84

6000      ……………………………….               72

6600      ……………………………….               66

7300      ……………………………….               60

 

HOW CAN I PREVENT THIS?

Abundant isotonic hydration is very important, an adequate respiratory technique, pharmacological prophylaxis with acetazolamide, and of course a balanced diet, especially in the groups we have seen such as proteins, carbohydrates, lipids and vitamins.

 

TREATMENT

MILD AMS:

– Stopping the ascent

– Can be treated with symptomatic medication

MODERATE AMS:

– Descend until symptoms stop

– Medication and rest before ascending again

SEVERE AMS:

– GO DOWN !

– Medication

Consider that medication is by no means a solution to the main problem of altitude.

 

HAPE SPECIFIC TREATMENT

GET DOWN ASAP!

– Rest the victim with the chest at 45° in a semi-sitting position.

– Supplemental oxygen

– Nifedipine 20 mg c/12 hrs

 

HACE TREATMENT

– Descent – evacuation

– Specific medications

– Oxygen at low flow for a long time

– Non-steroidal anti-inflammatory drugs

-Diclofenac (delayed release) is the No. 1 option

– Ibuprofen (600 mg c/8 hrs, max dose 2400mg x day)

– Aspirin

– Paracetamol (1000mg every 8 to 6 hours)

HACE TREATMENT

Acetazolamide (Diamox) – diuretic that also helps to eliminate bicarbonate (1 tablet -250 mg – every 8 hrs.

CONTRAINDICATED WHEN:

– allergy to sulphonamide

– history of renal colic

– narrow-angle glaucoma

– renal hepatic insufficiency

– adrenal insufficiency

Acetazolamide promotes the elimination of bicarbonate in the urine and thus eliminates the possibility of decompensating sodium saturation in the body by eliminating its main transporter.

PHARMACOLOGICAL TREATMENT

 

Acetazolamide

Indication:   AMS

Via:                Oral

Prevention:  125 – 250 mg c / 12 hrs

Treatment:   250mg c / 12 hrs

 

Dexamethasone

Indication:      AMS / HACE / HAPE

Via:                  Oral, IM or IV

Prevention:

Treatment:     4 mg w/hours 8 mg attack dose then 4 mg every 6 hours

 

Nifedipine

Indication:     HAPE

Via: Oral

Prevention:    20 to 30 mg c/ 12 hours

Treatment:     20 to 30 mg c/12 hours

 

Administer oxygen to maintain saturation above 90%.

CORTICOIDS

Dexamethasone (anti-inflammatory)

– initial dose: 8 mg V.O. or I.M.

– maintenance dose: 4 to 8 mg every 6 hrs. V.O. or I.M.

As you were able to read acclimatization is very important to enjoy the mountain, at least 4 days from the time you arrive at the airport, the altitude at La Paz airport is 4000mts (13 400ft).