Physiology of acid-base equilibrium:Why is the pH maintained at 7.4? Masaya HIBINO 1 , Norimichi UENISHI 1 1Department of Emergency and General Internal Medicine Fujita Health University School of Medicine pp.141-152
Published Date 2020/1/1
DOI https://doi.org/10.11477/mf.3102200719
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The pH of extracellular fluid is maintained at 7.4 through the action of multiple regulatory mechanisms including buffers system (carbonic acid-bicarbonate system, phosphate system, hemoglobin system, protein system), respiratory function, and renal system. The pH of extracellular fluid is strongly influenced not only by respiration (CO2) and buffers (HCO3-) but also by various intracellular fluids involved in synthesis and metabolism. The effect of the pH deviating from 7.4 on various organs, especially the circulatory system, have been studied for many years. In experiments with isolated hearts, acute metabolic acidosis causes cardiac dysfunction. In experiments using individual animals, the sympathetic nervous system is activated in a compensatory manner to increase cardiac contractility and increase blood pressure. Differences in the effects on circulation due to respiratory or metabolic acidosis are clear. There is a wide range of approaches to administering bicarbonate in acidosis. There is evidence that this treatment improves the hemodynamics although the prognosis is poor, and we await the results of future studies.

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