Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 21-22: Respiratory Alkalosis + Key Features Download Section PDF Listen +++ ++ 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 ++Table Graphic Jump LocationTable 21–16.Causes of respiratory alkalosis.View Table||Download (.pdf) Table 21–16. 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) Liver 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 Download Section PDF Listen +++ ++ Acute respiratory alkalosis Light-headedness Anxiety Paresthesias Perioral numbness Tetany in severe alkalosis from low ionized calcium + Diagnosis Download Section PDF Listen +++ ++ 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 + Treatment Download Section PDF Listen +++ ++ 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, Breathing into a paper bag should be discouraged because it does not correct PCO2 and may decrease PO2 Sedation may be necessary if the process persists The severity of hypocapnia in critically ill patients has been associated with adverse outcomes