High Altitude Illness

Richard Dionne MDEmergency Medicine – University of Ottawa

March 2013

High Altitude Illness

• Goals & Objectives

• Understand the principles of acclimatization

• Discuss the clinical presentation, prevention and interventions for Acute Mountain Sickness

• Discuss the clinical presentation, prevention and interventions for High Altitude Pulmonary Edema (HAPE)

• Discuss the clinical presentation, prevention and interventions for High Altitude Cerebral Edema (HACE)

Case

You are going on a skiing vacation at Vail, Colorado.

On day 2 you feel tired, lightheaded and a mild headache. You attribute it to accumulated stress and fatigue that is getting back at you.

Could it be all the partying ???

Acute Mountain Sickness« A.M.S.»

Rapid ascension & non-acclimatized Feels like «Hangover» & «viral illness» Close to 25% visitors to Colorado Better in 2 - 7 days Danger : « H.A.P.E. » / « H.A.C.E. » Altitude ...

Moderate > 8000 feet (> 2500 m)High > 10 000 feet (> 3000 m)Extrême > 18 000 feet (> 5500 m)

A.M.S. Physiology

Hypobaric Hypoxia

FiO2 = Oxygen tension …

160 mmHg … sea level

130 mmHg … 1500 m (commercial plane)

120 mmHg … 2500 m

80 mmHg … 5500 m

40 mmHg … Everest 8848 m

Video

Prevention of A.M.S.

Staged ascent

No alcohol & tobacco

Normal Hydration

High carbohydrate diet

Diamox prophylaxis

Staged Ascent Recommended > 8000 feet (2500 m)

Above 3000 m …

Do not sleep higher than 1000 feet (300 m) from previous night …

Suggest one day ( 2 nights ) extra of acclimatisation at every 3000 feet (1000 m) … thereafter

Diamox Anhydrase carbonate inhibitor

Induces HCO3 diuresis causing a metabolic acidosis

Reflex Ventilation & Oxygenation … simulates : HVR

« Hypoxic Ventilatory Response »

Case

You and 3 of your friends decide to ascend Mont Aconcagua in Argentina. Your altitude is now 14000 feet, (4200 m) on your 6th day.

For the last 2 days you ’ve started a dry cough, that is getting worse as the day progresses.

High Altitude Pulmonary Edema« H.A.P.E. »

1-2% when > 12 000 feet

Diagnosis …

cough / dyspnea / bronchospasm / performance / pulmonary edema …

usually day 2 …

Non-cardiogenic pulmonary edema: pulmonary artery pressure ( P.A.P.) but normal wedge & L.V.E.F.

«H.A.P.E.»

Patchy infiltrates ?

Uneven distribution of

pulmonary vasoconstriction

that causes overperfusion,

distention and leakage in

remaining vessels …

Membrane protein permeability

is secondary to inflammation ?

Treatment

Reheat victim « P.A.P.» Oxygen « SaO2 & P.A.P. » Descent : 1500-3000 feet / Hyperbaric ? C-Pap ? Medication …

Nifedipine (Adalat) 10 mg, then 30 mg SR Bid … « PAP 30-50%»

+/- Diamox Lasix & Morphine ? (non-cardiogenic)

Case

Having decided to go down, you are still in contact with your friends that are now at 16 000 feet, they plan to summit tomorrow am …

One of your teamates as been having an increasing headache and feels unsteady, he may not try to summit but wants to wait for their return ???

High Altitude Cerebral Edema« H.A.C.E »

Usually > 12 000 feet Usually takes 1-3 days Ataxia / headache / N° V° / seizures

Mecanism Vasogenic edema :

« capillary leak syndrome »

Cytotoxic edema : ( Secondary ) « sodium - potassium pump failure »

« H.A.C.E »

M.R.I.

Increase in white matter signal

showing edema. Consistant with

vasogenic edema hypothesis …

Increase T2 signal in the

white matter and the corpum

callosum...

« H.A.C.E. »Predisposing factors

1- Rapid ascent : acclimatisation

2- Hypoventilation

3- Gas exchange alterations

4- Fluid retention

5- Individual disposition

1- Acclimatisation

Hypobaric hypoxemia

Alveolar hypoxemia

Arterial hypoxemia

Directly related to speed of ascent...

2- Hypoventilation

Hypoxic Ventilatory Response «H.V.R.»

Initially … Ventilation / Oxygenation & PaO2

Counter balanced … renal excretion of HCO3 in response to hypocapnia & alcalosis

of hyperventilation

H.V.R.= acclimatisation determinant factor

3- Gas exchange alterations Blood adaptation…

erythropoietin / RBC ’s (4-5-days) 2,3-DPG = right shift oxyhemoglobin curveResp. alkalosis = left shift oxyhemoglobin curve

Interstitial Pulmonary edema... A-a gradient & hypoxemia

In consequence …Vital Capacity … diminishedDiffusion capacity … diminishedV/Q mismatch … elevatedPulm. Artery Press. … elevatedPulm. Vasc. Resistance … elevated

4- Fluid retention

Acclimatised « reset » of osmolar neurocenter … ADH suppression & Aldosterone …

25% diastolic volume circulating endogenous norepinephrine

Non-acclimatized antidiuresis with ADH & Aldosterone still elevated

fluid retention and cerebral edema ...

5- Individual predisposition

Cannot predict Controversial ...

hability to accomodate an brain volume & CSF within the cranial box & spinal canal...

Treatment

1- Hypoxemia / Oxygenation

2- Control Acclimatisation

3- Cerebral edema

« capillary leak syndrome »

4- Symptomatic relief

Treatment1- Hypoxemia & Oxygenation

Minimum descent 1500-3000 feet as much as needed

Oxygen 100%

Hyperbaric Chamber portable Gamow / Zertec / P-portable can generate pressures 200mmHg (7000 feet / 2000 m

descent)...

« Gamow Hyperbaric Chamber »

Treatment2- Controlled Acclimatisation

Acetazolamide ( Diamox)

125-250 mg q 12h (2,5mg/Kg) diuresis / CSFstimulated « H.V.R.» ( ventilation )

Start 1-2 days before ascent & continue for 48h …

Gives paresthesias ++ / sulpha allergy

Treatment3- Cerebral Edema

Dexamethasone4-8 mg stat, then 4 mg po / IM / IV q 6hno role in acclimatisation

DiureticsAcetazolamide (Diamox)Furosémide (Lasix)

Mannitol & Hyperventilation exceptionnaly if severe

Treatment4- Symptomatic relief

Analgesic acetaminophen / ASA / codeine ?

Anti-emetics prochlorperazine (Stemetil)

HVR ?

Ginko Biloba as prophylaxis ???

Take Home ... A.M.S. : can ressemble viral illness...

H.V.R. : determinant factor for acclimatisation ...

H.A.P.E. : non-cardiogenic pulmonary edema / treatment = descent & O2...

H.A.C.E. : subtil cerebellar ataxia … the cerebellum is very sensitive to hypoxia ...