In this approach, acid-base balance is considered to be determined by net influx and efflux of H + and HCO 3 − as independent variables. The rationale is based on the abundance, physiological importance, and homeostatic control of these three reaction components. P co 2 is used to describe the respiratory component and HCO 3 − the metabolic component of acid-base disturbances with use of the Henderson equation ( 2, 3). It is based solely on the P co 2/carbonic acid/bicarbonate (HCO 3 −) equilibrium. The most common approach is called the physiological approach by its proponents ( 1, 2). Differences arise from emphasis on the components of the solutions in the body. In reality all three overlap, for they are based on similar underlying basic physical-chemistry principles and common clinical parameters. Three distinct approaches for the assessment acid-base disorders have been identified: the physiological approach, the physical-chemical approach, and the base excess (BE) approach ( 1, 2).
Acid base balance made easy pdf free#
We have developed a simple free mobile app that can be used to input the necessary values to use this approach at the bedside (Physical/Chemical Acid Base Calculator).Īssessment of acid-base status is a central part of the management of critically ill patients. The advantage of this approach is that it gives a better understanding of the mechanisms behind acid-base abnormalities and more readily leads to clinical actions that can prevent or correct the abnormalities. These include the traditional PCO 2 component and the addition of four metabolic processes, which we classify as “water-effects,” “chloride-effects,” “albumin effects,” and “others.” Six values are required for the analysis:, , pH, P co 2, albumin concentration, and base excess.
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However, the analysis can be made more pragmatic by using a series of simple equations to quantify the major processes in acid-base disturbances. Acceptance of his analysis has been limited because it requires a complicated set of calculations to account for all the variables and it d oes not provide simple clinical guidance. His key argument was that the traditional carbon dioxide/bicarbonate analysis with just the use of the Henderson-Hasselbalch equation does not account for the important role in the regulation of H + concentration played by strong ions, weak acids and water itself.
The late Peter Stewart developed an approach to the analysis of acid-base disturbances in biological systems based on basic physical-chemical principles.