by "Grog" (Alan W. Grogono), Professor Emeritus, Tulane University Department of Anesthesiology
The devastating 1952 poliomyelitis epidemic in Copenhagen (Danish: København) demonstrated the critical need for accurate acid-base assessment. About 3,000 people were infected, of whom roughly one in ten had respiratory paralysis due to bulbar poliomyelitis and about one in hundred died. The story of how 1,500 medical and dental students provided 24-hour manual ventilation and saved about 100 lives (Berend 2018) is summarized in greater detail at the start of the History Section. The author's own involvement in critical care, the creation of ventilators, and the design of acid-base diagrams is is at the foot of History Section
This tutorial was completely rewritten in March 2018 with new text, diagrams, fonts, and colors. It explains clinical acid-base balance and features the revised Interactive Acid-base Diagram (on the right) that now displays typical clinical disturbances in both Metric and US Units. Click on the small icons and diagrams throughout the website to get additional information – sometimes serious, sometimes light-hearted!
The website also focuses on the many Unfortunate Historical Decisions whose legacy still complicates this subject.
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."Either treat, or wait and watch."
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."Just six Sentences!"
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 starting with acidosis.
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.
It will depend on what you know and how you like to learn. History, Physiology, and the Interactive Diagram are all good places to start.
Alternatively, use the Index to select a particular topic that interests you most.
The 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 provides Self Testing and a large Teaching Version.
The mathematics and programming underlying the interactive diagrams and equations are described on a separate page.
"Correspond, touch, associate, connect." Contact me if you wish. I appreciate feedback, especially if you have ideas comments or suggestions, or if you find errors or spelling mistakes. Thank you.
Peer-reviewed accepted 11/21/06:|
MedEdPORTAL. Number: 402.
Alan W. Grogono
|Copyright Mar 2018.|
All Rights Reserved