High altitude pulmonary edema

Background

• Also known as HAPE

1. Noncardiogenic pulm edema d/t increased microvascular pressure in the pulm circulation
2. Most lethal of the altitude illnesses
3. Occurs in <1/10,000 skiers in Colorado; 2-3% of Mt. McKinley climbers
4. Typical pt is strong and fit; may not have symptoms of AMS before onset of HAPE
5. Most commonly noticed on the second night at a new altitude

Risk Factors

• Heavy exertion
• Rapid ascent
• Cold
• Excessive salt ingestion
• Use of a sleeping medication
• Preexisting pulmonary HTN
• Preexisting respiratory infection (children)
• Previous history of HAPE

Clinical Features

• Early
  • Dry cough, decreased exercise performance, dyspnea on exertion, localized rales
  • Resting SaO2 is low for the altitude and drops markedly w/ exertion (aids in the dx)
• Late
  • Dyspnea at rest, marked weakness, productive cough, cyanosis, generalized rales
  • Tachycardia and tachypnea correlate with the severity of illness
  • Altered mental status and coma (from severe hypoxemia)

Workup

• ECG
  • Right strain pattern
• CXR
  • Progresses from interstitial to localized-alveolar to generalized-alveolar infiltrates
• ABG
  • Hypoxemia with respiratory alkalosis

Differential Diagnosis

• Asthma
• Bronchitis
• CHF
• COPD
• MI

High Altitude Illnesses

• Acute mountain sickness
• Chronic mountain sickness
• High altitude cerebral edema
• High altitude pulmonary edema
• High altitude peripheral edema
• High altitude retinopathy
• High altitude pharyngitis and bronchitis
• Ultraviolet keratitis

Pulmonary Edema Types

Pulmonary capillary wedge pressure <18 mmHg differentiates noncardiogenic from cardiogenic pulmonary edema

• Cardiogenic pulmonary edema
• Noncardiogenic pulmonary edema
  • Negative pressure pulmonary edema
    • Upper airway obstruction
    • Reexpansion pulmonary edema
    • Strangulation
  • Neurogenic causes
    • Seizure
    • Head trauma
    • Subarachnoid hemorrhage
    • Electrocution
  • Iatrogenic fluid overload
    • Multiple blood transfusions
    • IV fluid
    • Inhalation injury
    • Pulmonary contusion
    • Aspiration pneumonia and pneumonitis
  • Other
    • High altitude pulmonary edema
    • Hypertensive emergency
    • ARDS
    • Flash pulmonary edema
    • Immersion pulmonary edema
    • Hantavirus pulmonary syndrome
    • Missed dialysis in kidney failure
    • Naloxone reversal

Treatment

• Immediate descent is treatment of choice - minimize exertion
• If cannot descend use combination of:
  • Supplemental O2 - Can completely resolve the pulmonary edema within 36-72hr
  • Hyperbaric bag
  • Keep pt warm (cold stress elevates pulm artery pressure)
  • Use expiratory positive airway pressure mask
  • Consider the medications listed below that are usually used for prevention

Disposition

• Admission
  • Warranted for severe illness that does not respond immediately to descent
• Discharge
  • Progressive clinical and X-ray improvement and a PaO2 of 60mmHg or SaO2>90%

Prevention

• Nifedipine 20mg q8hr while ascending is effective prophylaxis in pts who had HAPE before
• Tadalafil 10mg BID 24hr prior to ascent
• Salmeterol inhaled BID

See Also

• High Altitude Medicine