Respiratory Alkalosis
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Contents |
Introduction
- Decreased pCO2 due to hyperventilation. It may be primary or compensatory to metabolic acidosis.
Etiology
-
- gram-negative sepsis
- liver disease
- pregnancy
- excessive mechanical ventilation
- rapid correction of chronic metabolic acidosis may result in persistence of respiratory alkalosis (longer persistence of CNS acidosis)
Clinical-manifestations
- light-headedness
- syncope
- seizures
- palpitations
- cardiac arrhythmias
- symptoms resembling hypocalcemia
Laboratory
-
- chronic respiratory alkalosis mildly increases the anion gap
- chronic respiratory alkalosis mildly increases the anion gap
- * Rules for predicting [[[Hco3- | HCO3-]]] compensation for pure respiratory alkalosis
- acute: 2 meq decrease in [[[Hco3- | HCO3-]]] for each 10 mm Hg decrease in pCO2 ( PaCO2, arterial)
- chronic: 5 meq decrease in [[[Hco3- | HCO3-]]] for each 10 mm Hg decrease in pCO2
- failure of the [[[Hco3- | HCO3-]]] to decrease by the expected value suggests complicating metabolic alkalosis
- excessive increase in the [[[Hco3- | HCO3-]]] suggests complicating metabolic acidosis [2]4) serum
- [[[Hco3- | HCO3-]]] does not fall below 15 meq/L unless a concomitant metabolic acidosis is present
Management
- correct underlying disorder
- acute therapy is generally not necessary unless the pH is > 7.50
- if hypoxemia is not present
- reassurance
- breathing into a paper bag
- rapid correction of chronic respiratory alkalosis with compensatory metabolic acidosis will result in persistence of the metabolic acidosis
- CO2 rebreathing apparatus for persistent hyperventilation due to CNS disease
More General Terms
References
- Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 63-64
- Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15, American College of Physicians, Philadelphia 1998, 2006, 2009
