high altitude illness
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High Altitude Illness. Richard Dionne MD Emergency 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 - PowerPoint PPT PresentationTRANSCRIPT
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High Altitude Illness
Richard Dionne MDEmergency Medicine – University of Ottawa
March 2013
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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)
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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 ???
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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)
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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
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Video
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Prevention of A.M.S.
Staged ascent
No alcohol & tobacco
Normal Hydration
High carbohydrate diet
Diamox prophylaxis
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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
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Diamox Anhydrase carbonate inhibitor
Induces HCO3 diuresis causing a metabolic acidosis
Reflex Ventilation & Oxygenation … simulates : HVR
« Hypoxic Ventilatory Response »
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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.
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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.
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«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 ?
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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)
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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 ???
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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 »
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« 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...
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« H.A.C.E. »Predisposing factors
1- Rapid ascent : acclimatisation
2- Hypoventilation
3- Gas exchange alterations
4- Fluid retention
5- Individual disposition
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1- Acclimatisation
Hypobaric hypoxemia
Alveolar hypoxemia
Arterial hypoxemia
Directly related to speed of ascent...
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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
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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
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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 ...
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5- Individual predisposition
Cannot predict Controversial ...
hability to accomodate an brain volume & CSF within the cranial box & spinal canal...
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Treatment
1- Hypoxemia / Oxygenation
2- Control Acclimatisation
3- Cerebral edema
« capillary leak syndrome »
4- Symptomatic relief
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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)...
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« Gamow Hyperbaric Chamber »
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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
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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
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Treatment4- Symptomatic relief
Analgesic acetaminophen / ASA / codeine ?
Anti-emetics prochlorperazine (Stemetil)
HVR ?
Ginko Biloba as prophylaxis ???
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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 ...