High Altitude Illness Richard Dionne MD Emergency Medicine

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. » Y Rapid ascension & non-acclimatized Y Feels like «Hangover» & «viral illness» Y Close to 25% visitors to Colorado Y Better in 2 - 7 days Y Danger : « H. A. P. E. » / « H. A. C. E. » Y Altitude. . . ý Moderate > 8000 feet ý High > 10 000 feet ý Extrême > 18 000 feet (> 2500 m) (> 3000 m) (> 5500 m)

A. M. S. Physiology Y Hypobaric Hypoxia Y Fi. O 2 = Oxygen tension … ý 160 mm. Hg … sea level ý 130 mm. Hg … 1500 m (commercial plane) ý 120 mm. Hg … 2500 m ý 80 mm. Hg … 5500 m ý 40 mm. Hg … Everest 8848 m

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Prevention of A. M. S. Y Staged ascent Y No alcohol & tobacco Y Normal Hydration Y High carbohydrate diet Y Diamox prophylaxis

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

Diamox Y Anhydrase carbonate inhibitor Y Induces HCO 3 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 14000 feet, (4200 m) on your 6 th 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. » Y 1 -2% when > 12 000 feet Y Diagnosis … ý cough / dyspnea / bronchospasm / performance / pulmonary edema … ý usually day 2 … ý Non-cardiogenic pulmonary edema: Y pulmonary artery pressure ( P. A. P. ) but Y normal wedge & L. V. E. F.

«H. A. P. E. » Y Patchy infiltrates ? ý Uneven distribution of pulmonary vasoconstriction that causes overperfusion, distention and leakage in remaining vessels … ý Membrane protein permeability is secondary to inflammation ?

Treatment Y Reheat victim « P. A. P. » Y Oxygen « Sa. O 2 & P. A. P. » Y Descent : 1500 -3000 feet / Hyperbaric ? Y C-Pap ? Y Medication … ý Nifedipine (Adalat) Y 10 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 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 » Y Usually > 12 000 feet Y Usually takes 1 -3 days Y Ataxia / headache / N° V° / seizures Y Mecanism Y Vasogenic edema : « capillary leak syndrome » Y Cytotoxic edema : ( Secondary ) « sodium - potassium pump failure »

« H. A. C. E » M. R. I. ý Increase in white matter signal showing edema. Consistant with vasogenic edema hypothesis … ý Increase T 2 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 Y Directly related to speed of ascent. . .

2 - Hypoventilation Y Hypoxic Ventilatory Response «H. V. R. » Y Initially … Y Ventilation / Oxygenation & Pa. O 2 Y Counter balanced … Y renal excretion of HCO 3 in response to hypocapnia & alcalosis of hyperventilation Y H. V. R. = acclimatisation determinant factor

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

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

5 - Individual predisposition Y Cannot predict Y Controversial. . . 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 Y Minimum descent 1500 -3000 feet ý as much as needed Y Oxygen 100% Y Hyperbaric Chamber ý portable Gamow / Zertec / P-portable ý can generate pressures 200 mm. Hg (7000 feet / 2000 m descent). . .

« Gamow Hyperbaric Chamber »

Treatment 2 - Controlled Acclimatisation Y Acetazolamide ( Diamox) ý 125 -250 mg q 12 h (2, 5 mg/Kg) ý diuresis / CSF ýstimulated « H. V. R. » ( ventilation ) Y Start 1 -2 days before ascent & continue for 48 h … Y Gives paresthesias ++ / sulpha allergy

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

Treatment 4 - Symptomatic relief Y Analgesic ý acetaminophen / ASA / codeine ? Y Anti-emetics ý prochlorperazine (Stemetil) Y HVR ? Y Ginko Biloba as prophylaxis ? ? ?

Take Home. . . Y A. M. S. : can ressemble viral illness. . . Y H. V. R. : determinant factor for acclimatisation. . . Y H. A. P. E. : non-cardiogenic pulmonary edema / treatment = descent & O 2. . . Y H. A. C. E. : subtil cerebellar ataxia … ý the cerebellum is very sensitive to hypoxia. . .