Interpretation of neonatal blood gases, Part I: Physiology and acid-base homeostasis.

Accurate interpretation of blood gases is paramount in clinical management in the NICU. This interpretation should be based on a sound understanding of acid-base physiology. Acid-base homeostasis depends on a series of complex chemical reactions controlled by the kidneys and the lungs. The maintenance of a blood pH within the narrow range required for normal cellular reactions requires a balance between acid production and excretion. Somewhat separate but equally important to blood gas interpretation is an understanding of oxygen transport. Included in this is the relationship between oxygen and hemoglobin. This article, the first in a two-part series, discusses the physiology of acid-base balance and oxygen transportation. The second article provides an approach for systematic interpretation of blood gases.