LAUSR

The aim of this study was to develop reference renal saturation (rSrO2) curves in premature infants, depict how they differ from cerebral saturation (rScO2) curves, and evaluate the effect of blood pressure on these values using near-infrared spectroscopy (NIRS). This is a prospective cohort study of 57 inborn infants <12 h and <30 weeks gestation. rScO2, rSrO2, fractional tissue oxygen extraction (FTOE), and mean arterial blood pressure (MAP) were continuously monitored every 30 s for 96 h. Quantile regression was used to establish nomograms, and mean saturation values were evaluated for different MAP ranges. Median rSrO2 at the start of monitoring was ~10% higher than rScO2. rSrO2 showed a significant decline over time while rScO2 peaked at 26 h. FTOE demonstrated a similar but inverse trend to their saturation counterparts. rScO2 declined as MAP increased, while rSrO2 showed a peak and decline as MAP increased. We provide rSrO2 reference curves for the first 4 days of life, which differ in their trajectory from rScO2 and from what has previously been reported for rSrO2 in the full-term population. In addition, we observed a peak and decline in renal saturation with increasing MAP, suggesting a renovascular response to blood pressure changes. This article depicts reference renal saturation curves during the perinatal transition in preterm infants. We show how renal saturation compares to cerebral saturation trends over time. We describe a peak and decline in renal saturation with increasing MAP, suggesting a renovascular response to blood pressure changes. This article depicts reference renal saturation curves during the perinatal transition in preterm infants. We show how renal saturation compares to cerebral saturation trends over time. We describe a peak and decline in renal saturation with increasing MAP, suggesting a renovascular response to blood pressure changes.