Clinical biochemistry
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An approach to acid-base physiology based on quantitative relationships between systems is presented. Key elements in the approach advocated by Stewart are, first, that changes in H+ or protons and bicarbonate are not considered "primary," or initiating disturbances, but rather as changes that are "dependent" on the interactions between several systems. ⋯ In plasma, the systems and variables are strong ions (strong ion difference, SID); weak acids, or buffers (ion equivalence of total protein concentration, AtOt); and carbon dioxide (PCO2, as influenced by alveolar ventilation). This system provides a quantitative description of the interplay between systems, and it makes it much simpler to understand the effects of ion movements between cells and plasma, renal control of acid-base, the influence of metabolism, and management of acid-base disorders.