by "Grog" (Alan W. Grogono), Professor Emeritus, Tulane University Department of Anesthesiology
This tutorial was completely rewritten in March 2018 with new text, diagrams, fonts, and colors. It explains clinical acid-base balance and introduces an interactive acid-base diagram which displays typical clinical disturbances. Click on the small icons and diagrams throughout the website to get additional information – sometimes serious, sometimes light-hearted!
Several Unfortunate Historical Decisions complicate this subject and this website explains this history.
"What do I need to know?" The Bird's Eye View after this paragraph may help you. The concepts do not need numerical values for PCO2, pH, or Base Excess. This is important because, in an emergency, you might have to treat a patient without knowing these laboratory values anyway:
Respiratory: When breathing is inadequate carbon dioxide accumulates. The extra CO2 molecules combine with water to form carbonic acid, also known as respiratory acid, which contributes to an acid pH. The treatment, if all else fails, is to lower the PCO2 by breathing for the patient using a ventilator.
Metabolic: When normal metabolism is impaired acid forms, e.g., poor blood supply stops oxidative metabolism and lactic acid forms. This acid is not respiratory so, by exclusion, it is "metabolic." If severe, the patient may be in shock and require treatment, possibly by neutralizing this excess acid with bicarbonate, possibly by allowing time for excretion/metabolism.
That's it! The whole of acid-base balance in six sentences. As you explore this site, keep this bird's eye-view in mind. We will also consider low levels of metabolic and respiratory acid (alkalosis) - but clinical problems usually result in acidosis which justifies this initial overview.
Variations in pH or PCO2 used to be thought of as pathological entities. Experiments by Xu et al have shown, however, that very low pH and very high PCO2 may both be well tolerated when circulation and oxygenation are maintained. The implication is that abnormal levels of PCO2 or pH are best regarded as indicators of serious trouble, but not as pathology in themselves.
History, Physiology, and the Interactive Diagram are all good places to start.
Alternatively, use the Index to select the topic that interests you most.
The interactive acid-base diagram is a major feature of this website. It shows characteristic zones on an interactive diagram and simultaneously provides continuous text interpretation. In addition to showing the Classical Zones, it also allows Self Testing.
Contact me if you wish. I appreciate receiving your feedback, especially if you have ideas comments or suggestions, or if you find errors or spelling mistakes. Thank you.
Peer-reviewed successfully by:|
MedEdPORTAL. Number: 402.
Subsequent Revisions: Minor corrections only.
Alan W. Grogono, MB, BS, MD(Lond), FRCA, Professor Emeritus Department of Anesthesiology, Tulane University. Until his retirement in 1988 he was the Jack Aron Professor and departmental chairman. For more information visit About the Author.
Alan W. Grogono
|Copyright Mar 2018.|
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