Return to High Altitude After Altitude Illness

							High Altitude Illness
  Kevin deWeber, MD, FAAFP
  Lieutenant Colonel, US Army
Army World Class Athlete Program
         Ft. Carson, CO
              Objectives
• Review pathophysiology of high altitude
  illness (HAI)
• Review the types of HAI and how they are
  treated
• Review factors predisposing to HAI
• Discuss preventive treatment for those
  with a remote history of HAI
                 Preview
• Acclimatization and slow ascent are
  powerful
  – Ascend < 600 m/day
  – Rest day every 600 – 1200 m
• Prophylactic meds advised if unable to
  comply
• Treatment: rest, descent, oxygen, meds
     Environment at high altitude
        (>1500 m or 4920 ft)
• Barometric pressure
  decreases
• Partial pressure of
  oxygen decreases
• RESULT:
  “Hypobaric
  Hypoxia”
  – Lower alveolar O2
    leads to lower SaO2
                                     Ft. Carson, CO, ~6500 ft
    Pikes Peak, 14,110 ft (4300 m)




US Air Force Academy, ~7,000 ft
Acclimatization = body’s adaptation
       to hypobaric hypoxia
             Acclimatization
• Immediate (minutes to hours)
  – ↑ Sympathetic tone  ↑ HR & CO
  – ↑ Ventilation  ↑ PaO2 and ↓ PaCO2  ↓ pH
  – Renal bicarbonate diuresis (to balance pH)
  – ↑ Pulmonary artery pressure  ↑ O2
    absorption
• Delayed (days to weeks)
  – Erythropoietin  ↑ RBC production
  – Remodeling of pulmonary arterioles
             Altitude Illnesses
          (Failure to Acclimatize)
• Cerebral Syndromes
  – Acute Mountain Sickness (AMS)
  – High Altitude Cerebral Edema (HACE)

      mild AMS   moderate AMS        HACE


• Pulmonary Syndrome
  – High Altitude Pulmonary Edema (HAPE)

• Importance
  – HACE and HAPE can be fatal
      Acute Mountain Sickness
              (AMS)
• Defined as HEADACHE plus one or more
  symptom:
  – Anorexia, nausea or vomiting
  – Fatigue or weakness
  – Dizziness or lightheadedness
  – Difficulty sleeping
Effects of AMS on performance
• Mild: annoyance only
• Moderate: impaired concentration,
  memory, speech, and physical
  performance;
  – Can be disabling
  – Subtle abnormalities visible on MRI
  – Effects can last weeks
      High Altitude Cerebral Edema
                  (HACE)
•   AMS symptoms plus ALTERED L.O.C. and ATAXIA
•   Other neuro findings possible
•   Coma develops
•   Death results if untreated



• Pathophysiology
    – altered cerebral vascular permeability
      leads to brain swelling
    – MRI: cerebral edema,
      lesions of corpus callosum
  High Altitude Pulmonary Edema
               (HAPE)
• Defined by two pulmonary symptoms…
  – Cough, dyspnea at rest, exercise intolerance,
    chest tightness/congestion…
• and two pulmonary signs…
  – Crackles, wheezing, cyanosis, tachypnea,
    tachycardia
• Most common cause of death among HAI
  – 50% mortality rate if not treated quickly
  High Altitude Pulmonary Edema
               (HAPE)
• CXR findings
  – Blotchy fluffy infiltrates
• Pathophysiology
  Hypoxia
    pulmonary artery
      hypertension
     alveolar damage
         edema and
          hemorrhage into
          alveoli
          Risk factors for HAI
• Rapid gain in altitude
• Prior history of HAI
  – genetic factors involved
• Alcohol, sedatives
• HAPE: cold ambient
  temperature
      HAI Protective Factors
• Residence at elevation >900 m (2950 ft)
• Slow gain in elevation
  – <600 m (1970 ft) per day in sleeping elevation
• Genetic factors

• Physical fitness NOT protective
             Treating HAI
• Rest, halt ascent
• Descent
  – Moderate AMS: >500 m (1640 ft)
  – HACE: > 1000 m (3280 ft)
  – HAPE: 500 – 1000 m
• Oxygen if available
• Keep warm (esp. for HAPE)
• Portable hyperbaric chambers
Portable Altitude Chamber® (PAC)




Gamow® bag      Certec® bag
        Treating HAI (cont.)
• Acetazolamide
  – Speeds acclimatization
  – 75% effective in preventing AMS
  – Treats moderate AMS & HACE
  – Dose: 125-250 mg BID
        Treating HAI (cont.)
• Dexamethasone
  – Decreases cerebral edema
  – Treats moderate AMS and
    HACE
  – Prevents AMS, ? HACE
  – Dose
    • 2 mg po/IM/IV QID
    • 4 mg BID
         Treating HAI (cont.)
• Nifedipine
  – Decreases pulmonary artery
    pressure
  – Prevents and treats HAPE
  – Dose: 20 – 30 mg extended
    release BID
         Treating HAI (cont.)

• Salmeterol
  – Decreases alveolar fluid
    transport
  – Prevents and treats HAPE
  – Dose: 125 mcg inhaled BID
          Treating HAI (cont.)

• Tadalafil
  – Dilates pulmonary vessels,
    prevents pulmonary
    hypertension
  – May prevent HAPE
  – Dose: 10 mg po BID
     “Acute mountain sickness: influence of
   susceptibility, preexposure, and ascent rate”
         Incidence of AMS (%) during ascent to 4559 m in
               persons with a prior history of AMS
             58
    60
    50                                       Normal ascent rate
                                             and no pre-exposure
    40              33                       Slow ascent
                          29
    30
                                             Pre-exposure
    20
                                7            Pre-exposure AND
    10
                                             slow ascent
     0



Schneider M et al. Med Sci Sports Exerc 2002
        Treatment of Mild AMS
• Descend > 500 m (1640 ft)
  OR
• Rest 1-2 days at same altitude
• Oxygen 12-24 hours, if
  available
• Consider acetazolamide 125-
  250 mg po BID
• Symptomatic treatment with
  analgesics, anti-emetics
    Treatment of Moderate AMS

• Descend >500 m
• Rest 1-2 days
• Do not allow continued ascent/activity
  – Significant performance/cognition decrement
  – Risk of progression to HACE
• Oxygen 1-2 days, if available
• Acetazolamide; dex as alternate
   Prevention of recurrent AMS
• Proper acclimatization, slow ascent.
  If not possible…
• Acetazolamide 125-250 mg po BID starting 1
  day prior to ascent, continuing until at max
  altitude for 2 days. If not possible…
• Alternate: Dexamethasone 2 mg po QID or 4 mg
  BID, starting 1 day prior, cont. until at max
  altitude 2 days
• Unknown which is better or if combination
  therapy is indicated
       Treatment of HACE
• Immediate descent > 1000 m and
  hospitalize
• Oxygen to maintain SaO2 >90%
• Dexamethasone—8 mg PO/IM/IV
  initially followed by 4 mg QID
• Portable hyperbaric therapy if
  descent impossible
   Treatment of HACE (cont.)
• Management of coma
  – Bladder catheterization
  – Airway control
• Diagnostic studies
  – CXR to rule out concurrent HAPE
  – MRI to rule out other conditions
        Recovery from HACE:
           highly variable
• 1-3 days for symptoms to resolve
• Days to 12 weeks for neuropsychological
  function to normalize
• 3-4 weeks for papilledema to resolve
• Days to 5 weeks for MRI to normalize
 Prevention of recurrent HACE
(No evidence-based recommendations)
• Strong recommendation for acclimatization
  and slow ascent.
  If not possible, or descent/medical treatment not
     possible…
• Prophylaxis with acetazolamide or
  dexamethasone, as for AMS
        Treatment of HAPE
• Immediate descent 500-1000 m
• Oxygen to keep SaO2 >90%.
• If descent/O2 not immediately available…
  – Portable hyperbaric therapy
  – Nifedipine 20-30 mg extended release BID
    (avoid if concomitant HACE) and/or…
  – Salmeterol 125 mcg inhaled
    Treatment of HAPE (cont.)
• Admit if:
  – >4L/min O2 requirement
  – Elderly, very young
  – Concomitant HACE or co-morbid cardio-
    pulmonary disease
     • Dexamethasone if concomitant HACE
• Low-flow outpatient O2 for others; check
  daily
       Recovery from HAPE
• Variable; little evidence in literature
• May take 2 weeks to recover strength
• Resume some activity when SaO2 > 90%
  without supplemental O2
• Remaining at some altitude fosters
  acclimatization via pulmonary arteriolar
  remodeling
 Prophylaxis for recurrent HAPE
• Strong recommendation for acclimatization and
  slow ascent.
  If not possible, or descent/medical treatment not possible…
• Prophylactic options:
  –   Acetazolamide 125-250 mg po BID
  –   Salmeterol 125 mcg inhaled BID
  –   Nifedipine 20-30 mg extended release BID
  –   Dexamethasone 8 mg po BID (one DBPC study)
  –   Tadalafil 10 mg po BID (one DBPC study)
       • No evidence of superiority of one agent or risks/benefits of
         combination therapy
                 Preview
• Acclimatization and slow ascent are
  powerful
  – Ascend < 600 m/day
  – Rest day every 600 – 1200 m
• Prophylactic meds advised if unable to
  comply
• Treatment: rest, descent, oxygen, meds
Thank you!