Altitude Illness Flashcards
At what elevation does abrupt ascent from altitude make it common to have high altitude illness?
Above 2500m/ 8202feet
What are the short term physiologic effects of acclimatization?
Hypoxic Ventilatory Response (HVR): Increased respiratory rate to add more O2
Respiratory Alkalosis: Increased pH due to breathing off more CO2 than normal slows down your HVR, acting as a feedback mechanism.
Bicarbonate Diuresis: Metabolic Acidosis from your kidneys peeing out extra Ammonia (NH4+) This is in response to the respiratory Alkalosis.
2,3 DPG: The body will create more of this molecule to allow the body to offload more oxygen at distal tissues.
What are the long term physiologic effects of acclimatization?
Hypoxia Inducible Factor (HIF): Modulates the long term genes and proteins allowing better acclimatization.
Increased Erythropoietin: leads to more RBCs over time.
What is the major contributor to acute mountain sickness (AMS) in terms of physiology?
25% increase in cerebral blood flow in rapid ascent to 12,000ft. This causes cerebral edema and AMS.
Note the major effects of altitude on Sleep, Breathing rate, muscle tissue, and your Cardiovascular system?
Sleep: Fragmented and frequent arousals.
Breathing rate: Periodic and cyclical (Cheyne-Stokes) in response to changing pH causing changes to central respiratory drive.
Muscle: Decreased size due to net energy deficit.
Cardiovascular: increased sympathetic response (^BP, ^HR, decrease stroke volume).
How does acetazolamide work in prophylaxis of AMS? Who would you give this to?
Acidification of the blood leads to more rapid version of the bicarbonate diuresis.
Give for:
Rapid ascent to >3000m, 10000ft
A rapid gain in sleeping altitude (>1500m)
A History of AMS or HAPE
Periodic breathing or poor sleep.
**Dose is 125-250mg BID. Do not give to G6PD deficient individuals or sulfa allergic!
What things put you at increased risk of AMS?
Rapid ascent Higher altitude Longer exposure Higher level of exertion (think ruck vs. sprint) Recent altitude exposure Genetic susceptibility
What are the major symptoms of AMS?
Headache with recent elevation above 2500m AND Nausea, vomiting, anorexia Insomnia Dizziness Fatigue
What are the rules of Field management of AMS?
- AMS symptoms are AMS until proven otherwise.
- Do not ascend with AMS.
- Descend if AMS is not improving.
- Never let someone with AMS descend alone.
- Providers can get AMS, too.
A marine flies from Camp Pendleton to Denver and goes skiing at Breckenridge the next day. While skiing (after drinking too much the night before), he has some difficulty skiing on the top of the peak and has to sit down. He is nauseated, dizzy, and very tired. When you talk to him, he is confused about where he is, and tells you he wants to go to sleep. What does he likely have?
HACE - High Altitude Cerebral Edema.
Note that they have ataxia (poor coordination), all of the AMS symptoms, confusion, drowsiness, altered mentation, and on rare occasions personality changes and hallucinations.
DESCEND IMMEDIATELY!!!
Consider Dexamethasone (steroid) treatment
If a patient with AMS symptoms begins to have symptoms of shortness of breath and cough, what do you need to worry about?
HAPE - High Altitude Pulmonary Edema.
Criteria are 2 of: Dyspnea, cough, decreased exercise capacity, chest tightness
AND
2 of: crackles/wheezing on auscultation, central cyanosis, tachypnea, tachycardia.
Individuals do not need to have AMS symptoms (only present 50% of the time).
DESCEND IMMEDIATELY!!!
Consider Nifedipine treatment
How can most of AMS be prevented?
Graded ascent. Spend 2 nights at 8000-10000ft before going higher, climb no more than 1500ft/day, spend an extra night for acclimatization for every 3000 meters.
Avoid alcohol and sedatives, maintain fluid uptake, take a high carbohydrate diet, and avoid overexertion.
