Altitude

Question 1

High Altitude Illness

Answer 1

-Collective term for the cerebral and pulmonary syndromes that can occur
-Includes Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE)
following ascent to a high altitude
-

Question 2

risk factors

Answer 2

• Past hx of HAI (strong predictor*)
• Rate of ascent (strong predictor*)
• Genetic susceptibility
• Height of altitude achieved
• Vigorous exertion prior to acclimatization
• Substances that interfere w/acclimatization
  (i. e.-alcohol, sedative meds)
• Comorbidities that interfere w/respiration or circulation (i.e.-neuromuscular disease, pulmonary HTN, COPD, CF, pneumonia) -Abnormalities of cardiopulmonary circulation (Pulmonary HTN, PFO, MS)

Question 3

Acute Mountain Sickness

Answer 3

“like a hangover”

• headache
• fatigue
• lightheadedness
• lack of appetite -nausea/vomiting
• interrupted sleep
• mild dyspnea w/exertion
• Sxs range from mild -> severe
• Generally occurs at altitudes above 2000-2500 m
• Can occur w/in 1 hr but typical onset is w/in 6-12 hrs
• Often most severe after the 1st night, improves w/in 24 hrs if you do NOT ascend
• Sxs can persist for wks w/o further ascent-(uncommon*)
• PE, lab values, vitals, and O2 sats typically normal
• Diagnosis is based on history*
• Administration of supplemental O2 may help to support diagnosis as sxs typically improve rapidly with O2 if AMS

Question 4

High Altitude Cerebral Edema (HACE)

Answer 4

• exhaustion
• drowsiness
• confusion
• irritability
• severe weakness
• acting “drunk-like”
• ataxic gait
• stupor
• Typically occurs w/in 1-3 days of traveling above 3000 m (9800 ft.)
• general neurological signs (ataxia, AMS)
• papilledema or retinal hemorrhages
• decreased O2 saturation
• Focal neurological findings (slurred speech, hemiparesis, discrete visual deficit etc.) should raise concern for alternative diagnosis
• Diagnosis is based on history/physical exam*
• CXR-may reveal pulmonary edema
• Brain CT-may reveal cerebral edema
• Brain MRI-may reveal swelling or microhemorrhages (black spots near corpus callosum), can be helpful to confirm diagnosis after recovery

Question 5

High Altitude Pulmonary Edema (HAPE)

Answer 5

-non-productive cough
-mild to moderate dyspnea
-difficulty walking uphill
-may also have sxs of AMS
-Typically begins w/in 2-4 days of traveling above 3000 m (9800 ft)
In later stages-may develop: -cough w/pink, frothy sputum, +/-blood -dyspnea at rest, severe w/exertion
-tachycardia
-tachypnea
-low-grade fever
-inspiratory crackles
-decreased O2 saturation
-Diagnosis is based on history/physical exam*
-CXR-reveals patchy alveolar infiltrates
-Chest CT-reveals similar sxs as CXR, (typically unnecessary)
-Echocardiogram-reveals increased PA pressure, +/- right heart dysfunction (recommended if HAPE develops at altitudes <3000 m or in patients w/suspected cardiopulmonary abnormalities)

Question 6

HACE prevention

Answer 6

1. Ascend SLOWLY*
2. Consider a preventative medication (drug of choice-Acetazalomide*, +/- Dexamethasone)
   * Dexamethasone only if rapid ascent is necessary (rescue) and acclimatization is not possible-fast acting

Question 7

HAPE prevention

Answer 7

1. Ascend SLOWLY*

2. Consider preventative medication but only recommended for high risk individuals (drug of choice-Nifedipine*)

Question 8

Acetazolamide (Diamox)

Answer 8

• Drug of choice for prevention of AMS/HACE*
• Helps to facilitate acclimatization
• Sulfa medication (use caution w/sulfa allergy)
• Start taking 1 day prior and continue for 48 hrs OR until reaching highest altitude of trip
• AE’s: increased urination, numbness/tingling in extremities, nausea, diarrhea, drowsiness, blurred vision, bad taste in mouth
• Avoid taking during pregnancy

Question 9

Nifedipine

Answer 9

• Drug of choice for prevention of HAPE* (but only used in high risk individuals)
• CCB that reduces PA pressure and BP
• Start taking 24 hrs prior to ascent and continue for 5 days at destination altitude
• Well tolerated by most individuals
• AE’s: HA, dizziness, drowsiness, nausea, GI upset, insomnia, chest pain
• Caution w/pregnancy

Question 10

HACE tx

Answer 10

MEDICAL EMERGENCY!

• Early recognition and treatment are critical
• Most importantlyDescend ASAP!
• Portable hyperbaric chamber (several hrs)
• Supplemental O2
• Dexamethasone
• Comatose patients-can attempt hyperbaric chamber, intubation to reduce ICP (intracranial pressure)
• If severe-emergent consultation w/Neurosurgery
• May reach an irreversible state->death inevitable

Question 11

Dexamethasone

Answer 11

• Critical medication to have available for all extended excursions above 3000 m
• Administered immediately upon first suspicion of HACE*
• Initial dose, then q 6 hrs until descent achieved
• Not a substitute for immediate descent*
• Unlike Acetazolamide does not facilitate acclimatization

Question 12

HAPE TX

Answer 12

MEDICAL EMERGENCY!

• Early recognition and treatment are critical
• Descend to lower altitude!
• Supplemental O2 (most effective tx*)
• Portable hyperbaric chamber (can consider as alternative to immediate descent)
• Consider Nifedipine (if O2 not available and descent not possible)
• Meds in trials-inhaled B agonists, pDE-5 inhibitors
• Avoid cold temperatures (elevates PA pressure)
• REST, strictly limit physical exertion