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 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.» YRapid ascension & non-acclimatized YFeels like «Hangover» & «viral illness» YClose to 25% visitors to Colorado YBetter in days YDanger : « H.A.P.E. » / « H.A.C.E. » YAltitude... ýModerate> 8000 feet(> 2500 m) ýHigh> feet(> 3000 m) ýExtrême> feet(> 5500 m)

A.M.S. Physiology YHypobaric Hypoxia YFiO2 = Oxygen tension … ý160 mmHg … sea level ý130 mmHg … 1500 m (commercial plane) ý120 mmHg … 2500 m ý 80 mmHg … 5500 m ý 40 mmHg … Everest 8848 m

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Prevention of A.M.S. YStaged ascent YNo alcohol & tobacco YNormal Hydration YHigh carbohydrate diet YDiamox prophylaxis

Staged Ascent YRecommended > 8000 feet (2500 m) Above 3000 m … YDo not sleep higher than 1000 feet (300 m) from previous night … YSuggest one day ( 2 nights ) extra of acclimatisation at every 3000 feet (1000 m) … thereafter

Diamox YAnhydrase carbonate inhibitor YInduces HCO3 diuresis causing a metabolic acidosis Y  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 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. » Y1-2% when > feet YDiagnosis … ýcough / dyspnea / bronchospasm /  performance / pulmonary edema … ýusually day 2 … ýNon-cardiogenic pulmonary edema: Y  pulmonary artery pressure ( P.A.P.) but Y normal wedge & L.V.E.F.

«H.A.P.E.» YPatchy infiltrates ? ýUneven distribution of pulmonary vasoconstriction that causes overperfusion, distention and leakage in remaining vessels … ýMembrane protein permeability is  secondary to inflammation ?

Treatment YReheat victim «  P.A.P.» YOxygen «  SaO2 &  P.A.P. » YDescent : feet / Hyperbaric ? YC-Pap ? YMedication … ý Nifedipine (Adalat) Y10 mg, then 30 mg SR Bid … «  PAP 30-50%» ý +/- Diamox ý Lasix & Morphine ? (non-cardiogenic)

Case Having decided to go down, you are still in contact with your friends that are now at 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 » YUsually > feet YUsually takes 1-3 days YAtaxia / headache / N° V° / seizures YMecanism Y Vasogenic edema : « capillary leak syndrome » Y Cytotoxic edema : ( Secondary ) « sodium - potassium pump failure »

« H.A.C.E » M.R.I. ýIncrease in white matter signal showing edema. Consistant with vasogenic edema hypothesis … ýIncrease 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 YDirectly related to speed of ascent...

2- Hypoventilation YHypoxic Ventilatory Response «H.V.R.» YInitially … Y  Ventilation /  Oxygenation &  PaO2 YCounter balanced … Yrenal excretion of HCO3 in response to hypocapnia & alcalosis of hyperventilation YH.V.R.= acclimatisation determinant factor

3- Gas exchange alterations YBlood adaptation… ý  erythropoietin /  RBC ’s (4-5-days) ý  2,3-DPG = right shift oxyhemoglobin curve ýResp. alkalosis = left shift oxyhemoglobin curve YInterstitial Pulmonary edema... ý  A-a gradient & hypoxemia YIn consequence … ýVital Capacity… diminished ýDiffusion capacity… diminished ýV/Q mismatch… elevated ýPulm. Artery Press. … elevated ýPulm. Vasc. Resistance… elevated

4- Fluid retention YAcclimatised ý « reset » of osmolar neurocenter … ý ADH suppression & Aldosterone … Y 25%  diastolic volume Y  circulating endogenous norepinephrine YNon-acclimatized ý antidiuresis with ADH & Aldosterone still elevated Y fluid retention and cerebral edema...

5- Individual predisposition YCannot predict YControversial... ý hability to accomodate an  brain volume & CSF within the cranial box & spinal canal...

Treatment 1-  Hypoxemia /  Oxygenation 2- Control Acclimatisation 3-  Cerebral edema ý « capillary leak syndrome » 4- Symptomatic relief

Treatment 1-  Hypoxemia &  Oxygenation YMinimum descent feet ý as much as needed YOxygen 100% YHyperbaric Chamber ý portable Gamow / Zertec / P-portable ý can generate pressures 200mmHg (7000 feet / 2000 m descent)...

« Gamow Hyperbaric Chamber »

Treatment 2- Controlled Acclimatisation YAcetazolamide ( Diamox) ý mg q 12h (2,5mg/Kg) ý  diuresis /  CSF ýstimulated « H.V.R.» (  ventilation ) YStart 1-2 days before ascent & continue for 48h … YGives paresthesias ++ / sulpha allergy

Treatment 3-  Cerebral Edema Y Dexamethasone ý4-8 mg stat, then 4 mg po / IM / IV q 6h ýno role in acclimatisation Y Diuretics ýAcetazolamide (Diamox) ýFurosémide (Lasix) Y Mannitol & Hyperventilation ý exceptionnaly if severe

Treatment 4- Symptomatic relief YAnalgesic ý acetaminophen / ASA / codeine ? YAnti-emetics ý prochlorperazine (Stemetil) Y  HVR ? YGinko Biloba as prophylaxis ???

Take Home... YA.M.S. : can ressemble viral illness... YH.V.R. : determinant factor for acclimatisation... YH.A.P.E. : non-cardiogenic pulmonary edema / treatment = descent & O2... YH.A.C.E. : subtil cerebellar ataxia … ý the cerebellum is very sensitive to hypoxia...