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Harrison's Principles of Internal Medicine, 18e
| Part 2. Cardinal Manifestations and Presentation of Diseases > Section 5. Alterations in Circulatory and Respiratory Functions > |
Chapter 35. Hypoxia and Cyanosis
Sections: Hypoxia, Cyanosis, Clubbing, Acknowledgements, Further Readings.
Topics Discussed: hypoxia.
Excerpt:"The fundamental purpose of the cardiorespiratory system is to deliver O2 and nutrients to cells and to remove CO2 and other metabolic products from them. Proper maintenance of this function depends not only on intact cardiovascular and respiratory systems but also on an adequate number of red blood cells and hemoglobin and a supply of inspired gas containing adequate O2.Decreased O2 availability to cells results in an inhibition of oxidative phosphorylation and increased anaerobic glycolysis. This switch from aerobic to anaerobic metabolism, the Pasteur effect, maintains some, albeit reduced, adenosine 5'-triphosphate (ATP) production. In severe hypoxia, when ATP production is inadequate to meet the energy requirements of ionic and osmotic equilibrium, cell membrane depolarization leads to uncontrolled Ca2+ influx and activation of Ca2+-dependent phospholipases and proteases. These events, in turn, cause cell swelling and, ultimately, cell death.Changes in the central nervous system (CNS), particularly the higher centers, are especially important consequences of hypoxia. Acute hypoxia causes impaired judgment, motor incoordination, and a clinical picture resembling acute alcohol..."
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