High Altitude Sickness
What are the common symptoms of AMS?
"like a hangover" • headache • fatigue • lightheadedness • lack of appetite • nausea/vomiting • interrupted sleep • mild dyspnea w/exertion Sxs range from mildsevere Generally occurs at altitudes above 2000-2500 m (8000ft) 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
How would you make the HACE 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 (Often these things are not available where the pt is having sx (aka up on a moutain!)
What is acclimatization and what does it depend upon?
-Begins w/in minutes of ascent but requires weeks to complete -Involves multiple organ systems -Depends on several factors: -Rate of ascent -Height of altitude -Individual ability to compensate -Alcohol -Medications-sedatives -Temperature changes
What are signs of HAPE on exam?
-Tachycardia -Tachypnea -Low-grade fever -Inspiratory crackles -Decreased O2 saturation
What are the 2 major things a pt could do for AMS prevention? (Actually HACE is the same so think of these things for this too!)
1. Ascend SLOWLY (w/adequate time for acclimatization) 2. Consider a preventative medication
What are the preventative measures for HAPE?
1. Ascend SLOWLY* 2. Consider preventative medication but only recommended for high risk individuals (drug of choice-Nifedipine* - well tolerated. Calcium channel blocker.)
What is the treatment for HAPE?
AGAIN the top two are... • DESCEND to lower altitude! • Supplemental O2 (most effective tx*)• Early recognition and treatment are critical Early recognition and tx are crucial • Portable hyperbaric chamber • Consider Nifedipine (if O2 not available and descent not possible) • Additional meds currently in trials • Avoid cold temperatures (elevates PA pressure) • REST, strictly limit physical exertion
What is the MOST COMMON (and most mild) HAS?
Acute Mountain Sickness (AMS) - nonspecific sxs (i.e.-malaise, anorexia etc.) AMS-->HACE represent different points of severity along the same pathophysiologic process in the brain
Who does this often occur in?
Annually 100 million tourists from lowland areas visit destinations in US/abroad at high elevations Tourists, skiers, climbers, trekkers, military personnel, rescue workers, clinicians etc.
What is high altitude sickness and what are the 3 forms?
Collective term for the cerebral and pulmonary syndromes that can occur following ascent to a high altitude. Includes Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE)
What is the FIRST MANDATORY treatment of sx of HACE and HAPE?
DESCENT
How would you make a diagnosis of HAPE?
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, (recommended if HAPE develops at altitudes <3000 m or in patients w/suspected cardiopulmonary abnormalities)
With increases elevation, when should you see... No sx Mild sx Mild/moderate sx Severe sx
Generally no sxs if < 1500 m (5000 ft) Mild sxs (if at all) from 1500-2500 m (5000-8200 ft) Mild to moderate sxs of AMS common at 2500 m Severe sxs are more common and risk of HACE and HAPE increases substantially above 3000-4000 m (9800-13,100 ft)
What about for HTN, asthmatic, and DM patients and HAI?
HTN • Continue taking antihypertensives • Check BP regularly Asthma • Carry meds-including oral steroids (exacerbation) • Severe asthmatics should avoid high ascent (no evidence that altitude exacerbates asthma but should be cautious!) DM • May require lower doses of insulin on trekking days • Should use fast acting insulin, quick access to sweets • Check glucose regularly
What is the LEAST COMMON and rapidly fatal HAS?
High Altitude Cerebral Edema (HACE) - cerebral edema!
What is the MOST COMMON cause of death in HAI?
High Altitude Pulmonary Edema (HAPE) - it is also uncommon and rapidly fatal - affecting the lungs
What are sx of HAPE?
INITALLY • 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) LATER STAGES • cough w/pink, frothy sputum, +/-blood dyspnea at rest, severe w/exertion
What is the first and most important step for the body in acclimatization?
Increase ventilation in response to tissue hypoxia! Ventilation reaches a maximum after 4-7 days at the same altitude
What else does acclimation do to the body?
Increased sympathetic activity increases cardiac output (to maintain O2 delivery to tissues), BP, HR Increased hemoglobin concentration increases the O2 carrying capacity of the blood At the tissue level vascular endothelial growth factor stimulates greater blood flow and O2 delivery
What are the AE of Acetazolamide?
Increased urination, numbness/tingling in extremities, nausea, diarrhea, drowsiness, blurred vision, bad taste in mouth Avoid taking during pregnancy
What is the treatment for HACE?
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 stated - death inevitable
What does this mean??
PIO2 is directly affected by barometric pressure (Pb) (Pb goes down with altitude, PIO2 goes down with altitude) Pb diminishes significantly w/increasing altitude As PIO2 decreases with ascent the normal driving pressure of PO2 diminishes = TISSUE HYPOXIA The body then responds by trying to compensate (Acclimatization) Acclimatization reduces the gradient b/w PIO2 and PO2 optimizing delivery and utilization of O2 at cellular level
PIO2 and FIO2 = ?
PIO2 is the partial pressure of oxygen of inspired air FIO2 is the amount of air comprised of oxygen (remains constant)
What are the TOP TWO predictors of HAS?
Past hx of HAI (strong predictor*) Rate of ascent (strong predictor*) OTHER FACTORS - 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)
What is AMS treatment?
TOP TWO • Descend (immediate if sxs worsening) • SUPPLEMENTAL O2 • Can consider medications • Consider hyperbaric chamber (moderate AMS) • Headache-->ASA, Acetaminophen, Ibuprofen • Nausea/vomiting-->Promethazine (Phenergan), Odansetron (Zofran) • Consider Acetazolamide (moderate AMS) • Consider Dexamethasone (moderate AMS)
Pb = ?
barometric pressure (changes) - ex. higher at sea level than at high altitudes -Barometric pressure-pressure at any location on Earth, caused by the weight of the air above it 47 mmHg is vapor pressure of H2O at 37 deg C (remains constant) PIO2=FIO2 x (Pb -47 mmHg)
What would be considered ascending slowly and what would be the preventative med for AMS?HACE?
o Do not ascend > 1600 ft/day o Take a day of rest every 3200 ft o Climb high and sleep low o Avoid alcohol, sedatives (depress respiratory function and interfere w/physiologic responses) o Avoid over-exertion during the first few days o Abrupt caffeine withdrawal should be avoided (HA complicates things) Drug of choice-Acetazalomide*, +/-Dexamethasone, ASA or NSAIDS (headaches). START TAKING 1-2 days prior and continue for 48 hrs OR until reaching highest altitude of trip! (IT IS A DIUERETIC - thought is that the body will secrete more base, body is tricked into thinking it is acidotic, breathing deepens to allow more O2 in and more CO2 out)
What is recommended for HAI and heart disease?
o Limit activity to lower maximal level than at sea level o Achieve a moderate degree of conditioning before exercising at high altitude o Stress test-IHD or previous MI, angioplasty/CABG o If MI w/in 2 wks-consider travel only if no angina, dyspnea, or hypoxia at rest, must carry NTG o If unstable angina, uncontrolled arrhythmias or poorly controlled CHF-travel only for emergency o Ultimately-pt should consult their Cardiologist
What is the role of Dexamethasone in HAI tx?
• As prev. mentioned can be used for prevention (AMS, HACE) • Critical medication to have available for all extended excursions above 3000m!!! • Administered immediately upon first suspicion of HACE* • Initial dose, then q 6 hrs until descent achieved Not a substitute for immediate descent*!
When should you take Nifedipine? What are the AE of Nifedipine?
• CCB that reduces PA pressure and BP • Start taking 24 hrs prior to ascent and continue for 5 days at destination altitude • HA, dizziness, drowsiness, nausea, GI upset, insomnia, chest pain • Caution w/ pregnancy
What are the typical HACE symptoms?
• Exhaustion • Drowsiness • Confusion • Irritability • Confusion • Acting "drunk-like" • Ataxic gait • Stupor Typically occurs w/in 1-3 days of traveling above 3000 m (9800 ft.) Before AMS was "hang over." Now these are "drunk" symptoms.
What is a portable hyperbaric chamber?
• Individual is zipped into chamber and device inflated with pressure bags • Individual breathes in 100% O2 • Air in chamber resembles air at lower altitudes • Increases amt of O2 in blood • Facilitates O2 transport to tissues
What would signs of HACE be on exam?
• general neurological signs (ataxia (incoordination), AMS) • papilledema or retinal hemorrhages • decreased O2 saturation Focal neurological findings (slurred speech, hemiparesis, discrete visual deficit etc.) should raise concern for alternative diagnosis* (ie stroke)
What would signs of AMS be on exam?
• no reliable objective measures • PE, lab values, vitals, and O2 sats typically normal NOT REALLY HELPFUL! INSTEAD: - Diagnosis is based on history* - Administration of supplemental O2 may help to support diagnosis as sxs typically improve rapidly with O2 if AMS (this can also help to show the difference between this and alcohol effects)
