Summary
The diagnostic value of renal concentrating capacity expressed as free water clearance
(CH2O), in comparison with other routine criteria for the early identification of
acute renal failure (ARF), was evaluated in 1,203 adult patients undergoing cardiac
surgical procedures. On the basis of the appearance of pathologic CH2O values in the
range of -20 to 0 ml/hour or more positive, reversible or irreversible ARF was observed
in 90 (= 7.5 %) of our patients. Mortality in the presence of ARF was 47 %; total
ARF mortality was 3.5 %. CH2O was pathologic for the first time on an average of 1.6
days after operation. In contrast, routine ARF criteria reported in the literature,
such as serum urea and creatinine at varying substrate levels or oliguria, allowed
diagnosis 1 to 5.5 days later. Moreover, these parameters only partially and less
frequently met the criteria for ARF at the different levels. Likewise, the incidence
of ARF decreased to a minimum of 1.7 % and the total ARF mortality to 1.3 %, depending
on the severity of the criteria used. Altogether, the occurrence of pathologic CH2O
values proved to be the earliest, most frequent and most reliable criterion for the
recognition of ARF following cardiac surgery with cardiac-pulmonary bypass.
Key-Words:
Acute renal failure - Cardiac surgery - Cardio pulmonary bypass - Free water clearance
