Neonatal acid-base disturbances.

The introduction of the micro-Astrup technique (Siggaard Andersen, Engel, J0rgensen, and Astrup, 1960) with the subsequent modification of the nomogram (Siggaard Andersen, 1962) has given a rapid and simple method for separating the respiratory and metabolic components of acid-base equilibrium in the blood. Arterialized capillary blood from a heel stab has been used for the estimation ofpH and for equilibration with oxygen/ carbon dioxide mixtures of known composition. For the present discussion the respiratory aspects will not be considered, but only the so-called metabolic changes and the parameter used is the base excess. Base excess is defined as zero for blood with a pH of 7 40 at a Pco2 of 40 mm. Hg. A negative base excess indicates a deficit of base or an excess of fixed acid, i.e. a metabolic acidosis. Positive base excess indicates an excess of base or a deficit of fixed acid, i.e. a metabolic alkalosis. The normal range for base excess is from 2 to + 2 mEq/l. Metabolic Acidosis