Renal oxygenation measured by near-infrared spectroscopy in preterm neonates in the first week.

OBJECTIVE: To describe renal regional saturation of oxygen (RrSO2) values during the first week of life for preterm neonates born at <32 weeks gestational age (GA). METHODS: RrSO2 values recorded over the first week of life using near-infrared spectroscopy were retrospectively analyzed in this two-center cohort study of preterm infants without known congenital anomalies of the kidney. RESULTS: A cohort of 109 neonates with a median GA of 26.9 weeks and a median of 120 (IQR: 87-141) hours of continuous RrSO2 monitoring were included. Separately fitted trends in RrSO2 did not differ (p = 0.52) between sites and demonstrated a consistent decrease in RrSO2 by 20 points (95% CI: 9.6-30.1) during the first 60 h of life, followed by a stabilization of RrSO2 thereafter. RrSO2 baseline trends increased by 2.1 (95% CI: 0.8-3.3) percentage points for each additional week GA between 24 and 32 weeks GA. CONCLUSIONS: Despite differences in adjusted RrSO2 values between sites, profiles over time are consistent, allowing for the determination of RrSO2 trajectories in preterm infants. This expected pattern of RrSO2 changes in the first week may help guide future investigations and interventions to identify and reduce kidney injury in the preterm neonate. IMPACT: Renal regional saturation of oxygen (RrSO2) slowly decreases during the first 60 h of age in <32-week preterm neonates. While site differences were identified with respect to absolute values, RrSO2 trends from two different centers were not different. Lower gestational age neonates have lower RrSO2 levels during the first week.