[Kidney function in the newborn infant of 32 to 36 weeks gestation: the usefulness of the excreted sodium fraction].

: A total of 20 healthy premature newborns, with a gestational age between 32 and 36 weeks were studied for a year. The objective of the study was to determine the utility of the excreted sodium excretion fraction test (FENa) as a parameter used to evaluate renal function in this type of patients, using comparatively the excretion of creatinine. Of the patients studied, 12 were females and the rest males; the medium gestational age was 35.1 weeks (ranging from 32 to 36 weeks); their average weight at birth was 1,943 g (ranging from 1,372 to 2,626 g); serum creatinine varied from 0.3 to 1.2 mg/dL; urinary sodium was measured at 5.37 and 38 mEg/L; the excretion of creatinine was measured at 8.26 +/- 5.18 mL/min/1.73 m2. The FENa varied between 0.1 and 1.71% (x = 0.78 +/- 0.48). The results obtained showed that the FENa is a useful parameter to evaluate renal function in premature newborns with a gestational age between 32 and 36 weeks.