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For further information, see CMDT Part 21-22: Respiratory Alkalosis
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Occurs when hyperventilation reduces the PCO2, increasing serum pH
The most common cause is hyperventilation syndrome (Table 21–16)
Bacterial septicemia and cirrhosis are other common causes
Pregnancy is another cause of chronic respiratory alkalosis; progesterone stimulates the respiratory center, producing an average PCO2 of 30 mm Hg
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Elevated arterial blood pH, low PCO2
Serum HCO3– is decreased in chronic respiratory alkalosis
Although serum HCO3– is frequently < 15 mEq/L in metabolic acidosis, such a low level in respiratory alkalosis is unusual and may represent a concomitant primary metabolic acidosis
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Treatment is directed toward the underlying cause
Rapid correction of chronic respiratory alkalosis may result in metabolic acidosis as PCO2 is increased in the setting of previous compensatory decrease in HCO3–
In acute hyperventilation syndrome from anxiety,
The severity of hypocapnia in critically ill patients has been associated with adverse outcomes