High Altitude Medical Problems Tintinalli Chapter 207 Dave Piatt

Altitude Affects Physiology feet: Decreased exercise performance Increased alveolar ventilation Onset of acute mountain sickness feet: Decreased arterial O 2 sats Marked hypoxemia during sleep/exercise Most medical problems occur at this altitude due to overnight facilities at these heights

Altitude Affects Physiology feet: Uncommon in US Acclimation is needed feet: Severe hypoxemia and hypocapnea *Hypoxemia is maximal during sleep, so sleep altitude is the critical altitude to consider

Acclimation to High Altitude Ventilation Increased ventilation is initial adaptation to protect alveolar PO 2 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

Acclimation to High Altitude 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

Acclimation to High Altitude Fluid Balance Diuresis and hemoconcentration are normal responses Antidiuresis is a hallmark of acute mountain sickness

Acclimation to High Altitude Cardiovascular system Stroke volume decreases Heart rate increases Pulmonary pressure increases ICP increases

Limitations to Acclimation 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 Due to sudden, severe hypoxic insult Leads to arterial desaturation, pulmonary edema, carbon monoxide poisoning, and sleep apnea Symptoms include dizziness, light- headedness, dimmed vision, and can lead to loss of consciousness Treat with supplemental O 2 and rapid descent

Acute Mountain Sickness 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 Treatment 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: 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) Signs/symptoms Altered mental status, ataxia, stupor, confusion, retinal hemorrhages, and may progress to coma if untreated Treatment Same as AMS: O 2, 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 O 2, descent, steroids

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

HAPE Signs/symptoms 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

HAPE Treatment Early recognition is key Immediate descent with minimal exertion Supplemental O 2 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 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 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 g/dL Treatment is phlebotomy, descent, O 2, acetazolamide, and medroxyprogesterone

Ultraviolet Keratitis (Snowblindness) 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 Arteriosclerosis heart disease Healthy cardiac muscle can withstand PaO 2 <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 Modest increases in altitude may cause people with hemoglobin sickle cell and sickle thalassemia to have a vaso- occlusive crisis Exposure to high altitude requires supplemental O 2 Sickle cell trait is not at increased risk, although splenic infarction syndrome has been reported in these patients

Questions 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 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. F 2. B 3. B 4. E 5. D