Respiratory Alkalosis Workup

  • Author: April Lambert-Drwiega, DO; Chief Editor: Zab Mosenifar, MD   more...
 
Updated: May 19, 2010
 

Laboratory Studies

The following laboratory studies may be helpful:

  • Arterial blood gas determinations: Alkalemia is documented by the presence of an increased pH level (>7.44) on arterial blood gas determinations. The presence of a decreased PCO2 level (< 36 mm Hg) indicates a respiratory etiology of the alkalemia.
  • Serum chemistries: Acute respiratory alkalosis causes small changes in electrolyte balances. Minor intracellular shifts of sodium, potassium, and phosphate levels occur. A minor reduction in free calcium occurs due to an increased protein-bound fraction. Compensation for respiratory alkalosis is by increased renal excretion of bicarbonate. In acute respiratory acidosis, the bicarbonate concentration level decreases by 2 mEq/L for each decrease of 10 mm Hg in the PaCO2 level. In chronic respiratory acidosis, the bicarbonate concentration level decreases by 5 mEq/L for each decrease of 10 mm Hg in the PaCO2 level. Plasma bicarbonate levels rarely drop below 12 mm Hg secondary to compensation for primary respiratory alkalosis.
  • Complete blood cell count: An elevation of the WBC count may indicate early sepsis as a possible etiology of respiratory alkalosis. A reduced hematocrit value may indicate severe anemia as the potential cause of respiratory alkalosis.
  • Liver function test: Findings may be abnormal if hepatic failure is the etiology of the respiratory alkalosis.
  • Cultures of blood, sputum, urine, and other sites: These should be considered, depending on information obtained from the history and physical examination and if sepsis or bacteremia are thought to be the cause of the respiratory alkalosis.
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Imaging Studies

Consider the following imaging studies:

  • Chest radiography: Perform chest radiography to help rule out pulmonary disease as a cause of hypocapnia and respiratory alkalosis. Potential etiologies that may be confirmed based on chest radiography findings include pneumonia, pulmonary edema, aspiration pneumonitis, pneumothorax, and interstitial lung disease.
  • CT scanning: CT scanning of the chest may be performed if chest radiography findings are inconclusive or a pulmonary disorder is strongly considered as a differential diagnosis. CT scanning is more sensitive for helping detect disease, and findings may reveal abnormalities not seen on the chest radiograph. Consider spiral CT angiography of the chest if pulmonary embolism is suggested. Consider CT scanning of the brain if a central cause of hyperventilation and respiratory alkalosis is suggested. Specific etiologies that may be diagnosed based on brain CT scan findings include cerebrovascular accident, CNS tumor, and CNS trauma.
  • Ventilation perfusion scanning: Consider this scan in patients who are unable to have intravenous contrast to assess for pulmonary embolism.
  • Brain MRI: If a central cause of hyperventilation and respiratory alkalosis is suggested and the initial brain CT scan findings are negative or inconclusive, an MRI of the brain can be considered. MRIs may reveal abnormalities not seen on CT scans. Possible etiologies based on MRIs include cerebrovascular accident, CNS tumor, and CNS trauma.
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Procedures

Perform a lumbar puncture if the history and physical examination findings are suggestive of a CNS infectious process. Perform cytologic analysis in patients suggested to have meningeal metastasis.

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Contributor Information and Disclosures
Author

April Lambert-Drwiega, DO  Fellow, Department of Pulmonology and Critical Care Medicine, East Tennessee State University

April Lambert-Drwiega, DO is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Medical Association, American Osteopathic Association, American Thoracic Society, Society of Critical Care Medicine, and Southern Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Ryland P Byrd Jr, MD  Professor, Department of Internal Medicine, Division of Pulmonary Medicine and Critical Care Medicine, Program Director of Pulmonary Diseases and Critical Care Medicine Fellowship, James H Quillen College of Medicine, East Tennessee State University; Medical Director of Respiratory Therapy, James H Quillen Veterans Affairs Medical Center

Ryland P Byrd Jr, MD is a member of the following medical societies: American College of Chest Physicians and American Thoracic Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Oleh Wasyl Hnatiuk, MD  Program Director, National Capital Consortium, Pulmonary and Critical Care, Walter Reed Army Medical Center; Associate Professor, Department of Medicine, Uniformed Services University of Health Sciences

Oleh Wasyl Hnatiuk, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and American Thoracic Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Senior Pharmacy Editor, eMedicine

Disclosure: eMedicine Salary Employment

Gregg T Anders, DO  Medical Director, Great Plains Regional Medical Command , Brooke Army Medical Center; Clinical Associate Professor, Department of Internal Medicine, Division of Pulmonary Disease, University of Texas Health Science Center at San Antonio

Gregg T Anders, DO is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and American Thoracic Society

Disclosure: Nothing to disclose.

Timothy D Rice, MD  Associate Professor, Departments of Internal Medicine and Pediatrics and Adolescent Medicine, St Louis University School of Medicine

Timothy D Rice, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Physicians

Disclosure: Nothing to disclose.

Chief Editor

Zab Mosenifar, MD  Director, Division of Pulmonary and Critical Care Medicine, Director, Women's Guild Pulmonary Disease Institute, Executive Vice Chair, Department of Medicine, Cedars Sinai Medical Center; Professor of Medicine, David Geffen School of Medicine at UCLA

Zab Mosenifar, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, and American Thoracic Society

Disclosure: Nothing to disclose.

References

  1. Kazmaier S, Weyland A, Buhre W, et al. Effects of respiratory alkalosis and acidosis on myocardial blood flow and metabolism in patients with coronary artery disease. Anesthesiology. Oct 1998;89(4):831-7. [Medline].

  2. Effros RM, Wesson JA. Acid-Base Balance. In: Mason RJ, Broaddus VC, Murray JF, Nadel JA, eds. Murray and Nadel's Textbook of Respiratory Medicine. Vol 1. 4th ed. Philadelphia, PA: Elsevier Saunders; 2005:192-93.

  3. DuBose TD, Jr. Acidosis and Alkalosis. In: Kasper DL, Braunwald E, Fauci AS, Hauser Sl, Longo DL, Jameson JL,eds. Harrison's Principles of Internal Medicine. 16th. New York, NY: McGraw-Hill; 2005:270-1.

  4. Phillipson EA, Duffin J. Hypoventilation and Hyperventilation Syndromes. In: Mason RJ, Broaddus VC, Murray JF, Nadel JA, eds. Murray and Nadel's Textbook of Respiratory Medicine. Vol 2. 4th ed. Philadelphia, PA: Elsevier Saunders; 2005:2069-70, 2080-84.

  5. Goldman A. Clinical tetany by forced respiration. JAMA. 1922;78:1193-95.

  6. Haldane JS, Poulton EP. The effects of want of oxygen on respiration. J Physiol. 1908;37:390-407.

  7. Kirsch DB, Jozefowicz RF. Neurologic complications of respiratory disease. Neurol Clin. Feb 2002;20(1):247-64, viii. [Medline].

  8. Gardner WN. The pathophysiology of hyperventilation disorders. Chest. Feb 1996;109(2):516-34. [Medline].

 
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