Renal adaptation to extrauterine life in patients with respiratory distress syndrome
A. T. Costarino, S. Baumgart, M. E. Norman and R. A. Polin
A spontaneous diuresis that precedes the improvement of pulmonary function
has been described in patients with respiratory distress syndrome (RDS).
The developmental changes in renal physiology responsible for this
spontaneous diuresis are not completely understood. To describe the
mechanisms responsible for the spontaneous diuresis, serial renal function
studies were performed during the first five days of life in nine premature
neonates with RDS. Diuresis was defined as a urine output that was at least
80% of fluid intake; prediuretic, diuretic, and postdiuretic periods were
observed in all study infants. Oxygenation did not improve until the
postdiuretic period. Renal function studies disclosed a significant
increase in free water clearance during the diuresis with the production of
dilute urine and a reciprocal rise in serum sodium concentration and plasma
osmolality. The glomerular filtration rate increased at the onset of
diuresis and remained elevated after the diuresis ended; however, the
proportion of filtrate excreted was significantly elevated during the
diuresis compared with prediuretic and postdiuretic values. These data
suggest that the diuresis in patients with RDS is a water diuresis
secondary to an endogenous water load.
