[Why does blood have a pH-value of 7.4? The theory of acid-base management].

Aim of the present paper is to discuss the physiologic principles of the acid-base status, in particular those of the pH value. The alpha-stat theory of acid-base management interprets the normal value of arterial pH, usually thought of as being 7.40, as a value derived from the intracellular pH, which is close to neutrality. This appears to have offered an evolutionary advantage, since most of the intermediates in biosynthetic pathways are ionized at neutrality resulting in a decreased rate of penetration across biological membranes of these compounds thus producing a benefit for the economy of a cell. Finally, we present the clinical implications of both the alpha-stat and the pH-stat strategy of acid-base management.