[Standard bicarbonate and base excess--obsolete parameters!]

The various techniques of interpretation of acid-base disorders are reviewed with special reference to the in vitro generated parameters 'standard bicarbonate' and 'base excess' on one hand and to the application of in vivo physiological data on the different acid-base disturbances on the other hand. The pivotal assumption that in vitro titration of PCO2 in whole blood (needed for estimation of standard bicarbonate and base excess) is representative for the in vivo behavior of the intact organism lacks any supportive evidence. The more serious pitfalls of interpretating acid-base problems by use of standard bicarbonate and base excess can be: 1. Inaccurate identification of the severity of an underlying acid-base disturbance, 2. Inadequate estimation of the time course of adaptation to an acid-base disorder (acute versus chronic) and 3. Failure to identify mixed acid-base disorders. Therefore, it is strongly recommended to use the traditional parameters (pH, PCO2, bicarbonate) in the light of the wealth of physiological in vivo data that form a sound basis for accurate clinical diagnosis.