Respiratory acidosis

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Background

  • acidemia = pH < 7.38
  • respiratory acidosis = pCO2 > 42
  • Acute respiratory acidosis: Change in pH = 0.008 X (40 - PaCO2)

vs. Chronic respiratory acidosis: Change in pH = 0.003 X (40 - PaCO2)

  • determine if another primary acid/base disturbance is occurring
    • calculate AG
    • if HCO3 < 24 + (pCO2-40)/10 x 3(+/-1) then there is a superimposed primary metabolic acidosis
      • for every 10mm increase in pCO2 >40, HCO3expected increases by 2-4mEq (2 if acute/limited time for metabolic compensation, 4 if chronic i.e. COPD)
    • if HCO3 > 24 + (pCO2-40)/10 x 3(+/-1) then suspect primary metabolic alkalosis

Etiology

Hypoventilation - acute vs chronic

Differential Diagnosis

Evaluation

Management

Improve alveolar ventilation

  1. Bronchodilators
  2. CPAP
  3. Intubation (esp of pH < 7.25)

See Also

References