High Altitude Illnesses

TLO

• Given a simulated casualty, treat altitude illnesses in accordance with the references.

ELO

• Choose from a given list the correct definition of acute mountain sickness.

• Choose the most common and prominent symptom of acute mountain sickness.

ELO

• Select from a given list the field management of Acute Mountain Sickness.

• Select from a given list five of the seven high altitude health preventive measures.

• Choose the correct definition of high altitude cerebral edema.

• Choose from a given list five of the symptoms of high altitude cerebral edema.

ELO• Choose the field management of high altitude

cerebral edema.• Choose the correct definition of high altitude

pulmonary edema.• Choose from a list three of the nine symptoms of

high altitude pulmonary edema.• Choose the field management of high altitude

pulmonary edema from a given list.• Choose from a list the most important treatment of

HACE and HAPE.

Physiology of Acclimatization

• “This malady only attacks strangers; the people of Tibet know nothing of it, nor do their doctors know why it attacks strangers.”- 14th Century Mongol Chieftain

Acclimatization

• April 15, 1875, the Zenith, a hot air balloon manned by three scientists attempted to go over 28,000 ft……..

Acclimatization

• “I wanted to cry out ‘We are at 8000m’ but my tongue was paralyzed. Suddenly I closed my eyes and fell inert, entirely losing consciousness.”

Acclimatization• “my two companions

were crouched in the basket, their heads covered….Sivel’s face was black, his eyes dull, his mouth open and full of blood. Croce’s eyes were half shut and his mouth bloody”

Acclimatization

• One hundred years later in 1978, Reinhold Messner and Peter Habeler climbed Mt Everest (29,035 ft) without the aid of oxygen

Acclimatization

• Two expeditions- two vastly different outcomes-

• What is the major factor which determined the ultimate outcome?

Factors in Acclimatization

• Altitude• Depends on rate of ascent.• Individual Variation

Acclimatization

• Hypoxia due to decreased barometric pressure

• Sea level: 760mmHg• 8,000 ft: 559mmHg• 14,000ft: 445mmHg• 18,000ft: 370mmHg• 29,000ft: 253mmHg

Acclimatization

• Starts at 5000 ft

Hypoxic Ventilatory Response

• Hypoxia triggers carotid body.• Central respiratory center stimulated.• Ventilation increases.

Respiratory Changes

• Increased respiratory rate will cause oxygen levels to rise and carbon dioxide levels to fall

• Any consequences?

Price to be Paid

• Carbon dioxide is the principle and most effective mediator of blood acidity therefore when the levels drop – the pH rises above acceptable levels.

• This respiratory alkalosis causes a brake to be placed on further ventilation.

Renal• Responds to alkalosis

with bicarbonate diuresis

• pH levels can now be maintained

• Brake on increased respiration is relaxed

• RR can increase once again

Pulmonary

• Unlike other areas of the body- the pulmonary vasculature is under local control rather than messages from the central nervous system

Pulmonary

• Whenever the oxygen pressure in alveoli are low then the pulmonary artery pressure rises

• Average PAP at 12,000 ft is 22 torr (5-10 torr at sea level)

Cardiac

• Increased heart rate to compensate for hypoxia– With moderate

altitudes – will return to baseline levels with acclimatization

• Little effect on blood pressure

Cerebral Circulation• Hypoxia causes

vasodilation• Hypocapnea causes

vasoconstriction• Vasodilation

outweighs vasoconstriction

• Increase of cerebral blood flow by 20-40%

Hemopoietic Response

• Erythropoeitin levels increase within two hours of ascent

• New RBC’s seen within 4-5 days

• 80% at 2 weeks• 95% at 6 weeks

Dehydration Risk Factors

• Increased respiratory losses• Bicarbonate Diuresis• Cold Diuresis• Difficulty in procuring water• Decreased Intake

Sleep Patterns

• Stage 1 increased, stage 2 unaffected. • Stages 3, 4 and REM decreased.• Due to nocturnal periodic breathing

– ^respiration– ^pH– Apnea– O2 sat declines, CO2 rises– Ventilatory rate rises

Acute Mountain Sickness

• “travellers have to climb over Mount Greater Headache, Mount Lesser Headache, and the Fever Hills”- warning from Chinese general to his emperor

AfterAction Report from Afghanistan

Acute Mountain Sickness (AMS)

• Definition: AMS is a self limiting illness which results when an unacclimatized individual ascends rapidly to high altitude

Pathophysiology

• Poor HVR• Mild AMS: Cerebral vasodilation• Severe AMS/HACE: Blood brain barrier

compromised; cerebral edema

Signs and Symptoms

• Prominent Symptoms:– Headache– Nausea– Vomiting

Signs and Symptoms

• Secondary Symptoms– Dizziness– Anorexia– Malaise– Insomnia– Weakness

AMS Lake Louise Consensus Criteria

• Headache PLUS• One of the following signs or symptoms:

– Nausea– Vomiting– Dizziness– Anorexia– Malaise– Insomnia– Weakness

AMS Headache

• Throbbing• Bitemporal or occipital• Worse at night/early morning• Worse with Valsalva

AMS

• “At 13,000 ft, my partner begged to descend before the alien clawing at the inside of his skull found its way out”

- AMS sufferer on Mt Ranier

Similar Syndromes

• Dehydration• Hangover• Viral Syndrome• Exhaustion• Medication• Carbon Monoxide

Poisoning

Field Management of AMS

• Stop further ascent

Field Management of AMS

• Symptomatic Treatment:– Headache

• Motrin• Aspirin

– Nausea• Compazine• Phenergan

– AMS Medications

Field Management of AMS

• Evacuation and Descent

Field Management of AMS

• AMS Medications:– Diamox (Acetazolamide)– Decadron (Dexamethasone)

Diamox• Carbonic Anhydrase

Inhibitor- causing bicarbonate diuresis- decreasing pH

• Stimulates Respiration• Decreases CSF Production• Maintains oxygenation

during sleep• Dose is 125-250mg

Diamox• Contraindicated in

sulfa allergy and G6PD deficiency

• May cause peripheral paresthesias and altered taste of carbonated beverages

• May cause bone marrow suppression, blurred vision, nausea

Diamox

• WARNINGS:– Dehydration– Will prevent altitude

illnesses but will not increase physical endurance

Dexamethasone

• Mechanism of Action: Unknown- reduce brain-blood volume, prevents blood-brain barrier leaks

• Effects evident in 2-8 hrs• Prevention: 2 mg q6h or 4mg q12h PO• Tx AMS: 4 mg q6h PO• Side Effects: Psychosis, hyperglycemia,

dyspepsia, rebound on withdrawal

AMS Medications

• Diamox preferred over Decadron– Lower side effect profile– Aids acclimatization

• Use Decadron with Sulfa Allergy and G6PD

• Combination is superior to single treatment

AMS Treatment

• All patients must be evaluated for HAPE and HACE

Incidence

• 6765 ft – <1% (MWTC)

• 7000-9000ft- 22%• 10000ft – 42%

(Colorado ski resorts)

AMS- Risk Factors

• Prior ascents without AMS is no guarantee against AMS in the future.

• Those with prior AMS are at increased risk of reoccurrence.

Prevention

• Conservative Ascent Profile:– Begin operations at

7,000ft or below– 3000ft/day below 14K– 1000ft/day above 14K– Extra day of

acclimatization for every 4,000 ft gain

Prevention

• Increase fluid intake – will only prevent dehydration not AMS

Prevention

• Work high• Sleep low

Prevention

• Avoid overexertion

Prevention

• Avoid alcohol and sedatives (at the very least the first two nights)

• Affects the ventilatory response

Prevention

• Diet – High in carbohydrates

– 70% or greater

Prevention

• Prophylaxis– Diamox– Decadron

Prophylaxis

• In setting of forced ascent• Previous history of altitude related illness• Diamox 125 mg PO BID, 24 hours prior to

ascent and 48 hours afterwards; also 500mg QD

High Altitude Cerebral EdemaHACE

• High altitude illness characterized by swelling of the brain

Pathophysiology of HACE

• Poor HVR• Increased vascular permeability (not well

understood)• Fluid moves from intravascular to

extravascular space (white matter edema)• Resulting increased intracranial pressure• Same process occurs in AMS to a lesser

extent

Signs and Symptoms

• Hallmarks of HACE: ataxia and altered mental status.

Signs and Symptoms

• Altered Mental Status– Personality Changes– Poor decision making– Irritability– Hallucinations– Difficulty with concentration– Decreasing level of alertness– Unconscious– Coma

Signs and Symptoms

• Ataxia– Tandem gait: most reliable test for both medical

and practical reasons

Treatment

• DESCENT– Only definitive

treatment– Patients are unstable

and can die shortly after the onset

Treatment

• Decadron (dexamethasone)

• Effects evident in 2-8 hours

• TX: HACE: 8-10mg IV/IM/PO followed by 4mg q6h

Treatment

• Oxygen

Treatment• Reduce brain edema• Renal Diuretics

– Lasix– Diamox

• Osmotic Diuretics– Glycerol– Mannitol

• Hyperventilation– With care as patient is

already alkalotic

Treatment• Gamow Bag

– “Portable hyperbaric chamber”

– Can descend 2psi/105mmHg

– At 14,000 ft will take pt down to 7,000’

– Weight 14 lbs– Recommendations:

• HAPE 2-4 hrs• HACE 4-6 hrs

Incidence

• 12K-14K is the dividing line for the increase in risk

• Incidence at less than 10K is very rare.

Risk Factors

• Same as for AMS

Prevention

• Same preventive measures as AMS

High Altitude Pulmonary Edema

• “….they suddenly encountered a cold wind which made them shiver and unable to speak. Hwuy-Ring could not go any farther. A white froth came from his mouth and he said “I cannot live any longer. Do you immediately go away, that we do not all die here”; and with these words he died” – Buddhist missionary 330AD

High Altitude Pulmonary Edema (HAPE)

• A high altitude illness which is characterized by filling of the lungs with fluid.

Pathophysiology

• Maladaptive Hypoxic Pulmonary Vasoconstrictor Response (HPVR)– beneficial in certain situations at low altitude

i.e. pneumonia.• Increased pulmonary artery pressure.• Edema secondary to leakage from increased

hydrostatic pressure.• Impaired oxygenation.

Symptoms of HAPE

• Weakness/Decreased Exercise Performance

• Cough• Chest Tightness• Dyspnea at rest

Signs of HAPE

• Crackles/Wheezing in at least one lung field

• Increased RR• Increased HR• Central Cyanosis (Note: Reset baselines

for RR and HR)

Other Signs of HAPE

• Orthopnea• Cough productive of

pink frothy sputum is a late sign

• Pulse Oximetry– Denali 14K- 80-87%

HAPE < 75% - Reset baselines

Lake Louise Criteria

• Symptoms: Any two of the following:• Dyspnea at rest• Cough• Weakness/Decreased Exercise Performance• Chest tightness PLUS:

Lake Louise Criteria

• Signs: Any two of the following:• Crackles/Wheezing in at least one lung field• Increased RR• Increased HR• Central cyanosis

HAPE Treatment• DESCENT- Definitive treatment• High flow O2.

– Triage Tool- Place patient on high flow oxygen. Should see improvement in five minutes. Decrease PAP 30-50%

• Gamow Bag as a temporizing measure• Elevate head• Rest/Warmth• Medications

HAPE Treatment

• Rest and warmth– Decrease blood flow to pulmonary arteries and

therefore decreases pulmonary artery pressure– Incidences of sudden death with exertion in

cases of HAPE– Cold increases pulmonary artery pressure

therefore keep patients warm

HAPE Treatment

• Nifedipine 10/20 mg PO followed by:

• Procardia 30 mg q24h or Adalat 20mg q6h

• Pulmonary Artery Vasodilator – decrease PAP by 30%

                    

HAPE Treatment

• Albuterol• Unknown mechanism-

Na-ATPase Pump vs Pulmonary Vasodilator

Treatment Consideration

• HACE and HAPE often run together• Root Cause: Poor HVR• Unconscious patient with HAPE?

– Treat both HACE and HAPE

Incidence

• Incidence at lower than 10K is rare

Risk Factors

• Cold• URI• Otherwise same risk

factors as for AMS

HAPE Prevention

• If HAPE suceptible:– Salmeterol– Nifedipine

• Otherwise employ same preventative measures as for AMS

Experimental Treatments

• Nitric Oxide• Inhaled Iloprost

(prostacyclin)• Viagra• Garlic• Intermittent Hypoxia• Ginko• Diamox/Decadron

Sickle Cell Trait

• Splenic Syndrome- severe left upper quadrant pain upon exertion

• Prevention• Identification• Hydration

Miscellaneous High Altitude Illnesses

Visual

• RK – Effects starting at 10K

• PRK- Safe• LASIK- Nearsighted

at 14-20K

High Altitude Deterioration

• Weight loss• Lethargy, Weakness• Poor sleep• Headache• Polycythemia

Systemic Edema

• Edema of the hands, face, ankles• Screen for other high altitude illnesses• Can treat with Lasix or Diamox

High Altitude Pharyngitis/Bronchitis

• Sore throat, chronic cough, dry nasal passages

• Treatment- hydration, lozenges, antitussive agent (codeine), steam inhalation, nasal saline spray, topical nasal ointment (vaseline)

Insomnia

• Periodic breathing-• Treatments:

– Diamox 62.5 mg qhs

GI Distress

• Difficulty with digestion at high altitudes (fats)

• Treat with– Antacids– H2 Blockers– Small frequent meals (carbs)

Miscellaneous• High Altitude Retinal Hemorrhages• Hypertension• Coronary Artery Disease• Asthma• Immune Suppression• Impaired Wound Healing• Thrombosis/Focal Neurological Findings• Subacute Mountain Sickness• Chronic Mountain Sickness

Questions ???