Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content + Print Section ++ For further information, see CMDT Part 21-22: Respiratory Alkalosis + Key Features Print Section ++ ++ Elevated arterial blood pH (> 7.45), low PCO2 (< 32 mm Hg) Occurs when hyperventilation reduces the PCO2, increasing serum pH The most common cause is hyperventilation syndrome (Table 21–17) Bacterial septicemia and cirrhosis are other common causes Pregnancy is another cause of chronic respiratory alkalosis, probably from progesterone stimulation of the respiratory center, producing an average PCO2 of 30 mm Hg ++Table Graphic Jump LocationTable 21–17.Causes of respiratory alkalosis.View Table|Favorite Table|Download (.pdf)Table 21–17. Causes of respiratory alkalosis. Hypoxia Decreased inspired oxygen tension High altitude Ventilation/perfusion inequality Hypotension Severe anemia CNS-mediated disorders Voluntary hyperventilation Anxiety-hyperventilation syndrome Neurologic disease Cerebrovascular accident (infarction, hemorrhage) Infection Trauma Tumor Pharmacologic and hormonal stimulation Salicylates Nicotine Xanthines Pregnancy (progesterone) Hepatic failure Gram-negative septicemia Recovery from metabolic acidosis Heat exposure Pulmonary disease Interstitial lung disease Pneumonia Pulmonary embolism Pulmonary edema Mechanical overventilation Adapted, with permission, from Gennari FJ. Respiratory acidosis and alkalosis. In: Maxwell and Kleeman’s Clinical Disorders of Fluid and Electrolyte Metabolism, 5th ed. Narins RG (editor). McGraw-Hill, 1994. + Clinical Findings Print Section ++ ++ Acute respiratory alkalosis Light-headedness Anxiety Paresthesias Numbness about the mouth Tetany in severe alkalosis from low ionized calcium + Diagnosis Print Section ++ ++ Elevated arterial blood pH (> 7.45), low PCO2 (< 32 mm Hg) Serum HCO3– is decreased (< 22 mEq/L or < 22 mmol/L) in chronic respiratory alkalosis Although serum HCO3– is frequently below 15 mEq/L in metabolic acidosis, it is unusual to see such a low level in respiratory alkalosis, and its presence implies a superimposed (noncompensatory) metabolic acidosis + Treatment Print Section ++ ++ Rapid correction of chronic respiratory alkalosis may result in metabolic acidosis as PCO2 is increased in the setting of previous compensatory decrease in HCO3– Treatment is directed toward the underlying cause In acute hyperventilation syndrome from anxiety, rebreathing into a paper bag increases PCO2. Sedation may be necessary if the process persists