High Altitude Illness
-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
-
risk factors
- 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)
Acute Mountain Sickness
“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
High Altitude Cerebral Edema (HACE)
- 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
High Altitude Pulmonary Edema (HAPE)
-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)
HACE prevention
- Ascend SLOWLY*
- Consider a preventative medication (drug of choice-Acetazalomide*, +/- Dexamethasone)
* Dexamethasone only if rapid ascent is necessary (rescue) and acclimatization is not possible-fast acting
HAPE prevention
- Ascend SLOWLY*
2. Consider preventative medication but only recommended for high risk individuals (drug of choice-Nifedipine*)
Acetazolamide (Diamox)
- 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
Nifedipine
- 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
HACE tx
MEDICAL EMERGENCY!
- Early recognition and treatment are critical
- Most importantlyDescend 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
Dexamethasone
- 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
HAPE TX
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
