Transcript High Altitude Medical Problems

High Altitude Medical Problems
Tintinalli
Chapter 207
Dave Piatt
Altitude Affects Physiology
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5000-8000 feet:
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Decreased exercise performance
Increased alveolar ventilation
Onset of acute mountain sickness
8000-14000 feet:
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Decreased arterial O2 sats
Marked hypoxemia during sleep/exercise
Most medical problems occur at this altitude
due to overnight facilities at these heights
Altitude Affects Physiology
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14000-18000 feet:
Uncommon in US
 Acclimation is needed
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18000+ feet:
Severe hypoxemia and hypocapnea
 *Hypoxemia is maximal during sleep,
so sleep altitude is the critical altitude
to consider
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Acclimation to High Altitude
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Ventilation
Increased ventilation is initial
adaptation to protect alveolar PO2
 Attenuated quickly by respiratory
alkalosis
 Renal excretion of bicarb compensates,
pH returns to normal, and ventilation
increases again
 This process culminates in 4-7 days
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Acclimation to High Altitude
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Blood
Within 2 hours of ascent to altitude,
erythropoietin is increased in plasma
 Over days to weeks, this results in
increased RBC mass and chronic
polycythemia
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Acclimation to High Altitude
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Fluid Balance
Diuresis and hemoconcentration are
normal responses
 Antidiuresis is a hallmark of acute
mountain sickness
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Acclimation to High Altitude
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Cardiovascular system
Stroke volume decreases
 Heart rate increases
 Pulmonary pressure increases
 ICP increases
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Limitations to Acclimation
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Prolonged high altitude exposure
can lead to loss of fat and lean body
mass, lethargy, poor sleep,
weakness, headaches, right
ventricular strain, polycythemia, and
prolonged cerebral hypoxia
Acute Hypoxia
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Due to sudden, severe hypoxic insult
Leads to arterial desaturation, pulmonary
edema, carbon monoxide poisoning, and
sleep apnea
Symptoms include dizziness, lightheadedness, dimmed vision, and can lead
to loss of consciousness
Treat with supplemental O2 and rapid
descent
Acute Mountain Sickness
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Onset in a few hours
Symptoms are bifrontal headache that
increases with bending over and Valsalva
and is worse at night; anorexia,
nausea/vomiting, and sleep difficulties
In severe form, may see ataxia, altered
LOC, and coma within 12 hours
Fluid retention is a hallmark of AMS, so
you may see peripheral and facial edema
and hear rales
Acute Mountain Sickness
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Treatment
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Hold ascent
Descend if symptoms worsen or do not abate
Immediate descent if altered LOC, ataxia, or
pulmonary edema is present
Descent is definitive treatment for all forms of
altitude illness: 500-1000 feet is effective
Supplemental O2
Acetazolamide speeds acclimation and treats
AMS. Contraindicated if sulfa allergy
Dexamethasone is reserved for moderate to
severe cases due to side effects
High Altitude Cerebral
Edema (HACE)
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Signs/symptoms
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Altered mental status, ataxia, stupor,
confusion, retinal hemorrhages, and may
progress to coma if untreated
Treatment
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Same as AMS: O2, descend, steroids
Loop diuretics (Lasix, Bumex) will reduce
brain overhydration, but hypoperfusion and
ischemia is a significant risk
Cerebrovascular Syndromes
of Altitude
Strokes (hemorrhagic and infarcts)
may occur in healthy young people
at altitude, as well as TIA, cortical
blindness, focal neurologic signs,
hemiparesis, or hemiplegia
 Treatment with O2, descent, steroids
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High Altitude Pulmonary
Edema (HAPE)
Most lethal of altitude illnesses, but
is easily reversible
 Cause of death is lack of early
recognition, misdiagnosis, or
inability to descend
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HAPE
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Signs/symptoms
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Onset is 1-4 days after ascent
Dry cough, decreased exercise performance,
dyspnea on exertion, localized rales
Later, tachycardia, tachypnea, dyspnea at
rest, weakness, productive cough, cyanosis,
generalized rales, decreased consciousness,
then coma and death
Low-grade fever is common
HAPE
HAPE is noncardiogenic, hydrostatic
edema with normal LV function
 Pulmonary hypertension is essential
component
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HAPE
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Treatment
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Early recognition is key
Immediate descent with minimal exertion
Supplemental O2
Keep patient warm
Nifedipine reduces pulmonary arterial
pressure by 30-50%
Salmeterol BID decreases HAPE by 50% in
patients with previous HAPE episode
High Altitude
Pharyngitis/Bronchitis
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Over 2500 meters, may develop dry
hacking cough, which becomes purulent
over time
Painful pharyngitis becomes nearly
universal with prolonged exposure over
2500 meters
Pharyngeal membranes become dry,
cracked, and painful due to dehydration
and high ventilation
Treat with breathing of steam, lozenges,
and forced hydration
Chronic Mountain
Polycythemia
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Characterized by excessive polycythemia
for a given altitude
Signs/symptoms include headache,
muddled thinking, difficulty sleeping,
impaired peripheral circulation,
drowsiness, and chest congestion
Hemoglobin usually around 20-22 g/dL
Treatment is phlebotomy, descent, O2,
acetazolamide, and medroxyprogesterone
Ultraviolet Keratitis
(Snowblindness)
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UVB is absorbed by the cornea and can
cause corneal burns in 1 hour
Symptoms appear at 6-12 hours
Symptoms include severe pain, foreign
body/gritty sensation, photophobia, tearing,
conjunctival erythema, and eyelid swelling
Is self-limited and heals within 24 hours
Treat with systemic analgesics and eye patch
Prevention with sunglasses that transmit
<10% of UVB rays with side shield
Chronic Illnesses Exacerbated
by High Altitude
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Arteriosclerosis heart disease
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Healthy cardiac muscle can withstand PaO2
<30 mmHg without ST changes or ischemia
Epidemilogic data shows people with ASHD
are not at increased risk of AMI, but may have
earlier onset of angina
Ascent to altitude causes an increase in BP
due to increased sympathetic tone, but
hypertension is not a contraindication to
altitude exposure
Sickle Cell Disease
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Modest increases in altitude may cause
people with hemoglobin sickle cell and
sickle thalassemia to have a vasoocclusive crisis
Exposure to high altitude requires
supplemental O2
Sickle cell trait is not at increased risk,
although splenic infarction syndrome has
been reported in these patients
Questions
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1. T or F? HAPE is cardiogenic in origin.
2. Which is the most lethal of altitude illnesses?
 A. HACE
 B. HAPE
 C. Acute mountain sickness
 D. Chronic mountain polycythemia
3. Which is false?
 A. Hypoxemia is maximal during sleep.
 B. Diuresis is the hallmark of acute mountain
sickness
 C. Prolonged high altitude exposure can lead to loss
of body mass
 D. Low-grade fever is common in HAPE
Questions
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4. Which of the following is indicated in the treatment
of severe acute mountain sickness?
 A. Supplemental O2
 B. Descent
 C. Acetazolamide
 D. Dexamethasone
 E. All of above
5. Nifedipine is used to treat:
 A. HACE
 B. Ultraviolet keratitis
 C. Chronic mountain polycythemia
 D. HAPE
 E. Acute mountain sickness
Answers
1.
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F
B
B
E
D