Low Renal Oxygen Saturation at Near-Infrared Spectroscopy on the First Day of Life Is Associated with Developing Acute Kidney Injury in Very Preterm Infants

<b><i>Background:</i></b> Acute kidney injury (AKI) is a frequent complication in preterm infants, and the identification of early markers of renal hypoperfusion is a chief challenge in neonatal intensive care units. <b><i>Objectives:</i></b> To describe the association between early markers of cardiovascular function and renal perfusion with AKI occurrence in a cohort of preterm infants &#x3c; 32 weeks’ gestation. <b><i>Methods:</i></b> 128 infants were prospectively included from birth to discharge. During the first day of life, we assessed cardiovascular function, systemic and organ blood flow by Doppler ultrasound, and monitored cerebral and renal regional oxygen saturation (rSO₂) using near-infrared spectroscopy (NIRS). These measures were analyzed in relation to developing AKI and serum creatinine (SCr) peak from day 2 to 7 of life. <b><i>Results:</i></b> 12 of 128 infants presented with AKI (9.4%). SCr peak was 155.3 ± 30.2 µmol/L in infants with AKI versus 82.0 ± 16.5 in non-AKI infants (<i>p</i> &#x3c; 0.001). Among all measures of cardiovascular function and renal perfusion, low mean cerebral and renal rSO₂ during the first day of life and a low resistive index at renal artery Doppler were significantly associated with developing AKI. After adjustment for possible confounding factors, low renal rSO₂ on the first day of life remained associated with a high SCr peak from day 2 to 7 of life. <b><i>Conclusion:</i></b> Low renal rSO₂ values during the first day of life correlate with developing AKI in preterm infants &#x3c; 32 weeks’ gestation. NIRS monitoring of renal function during adaptation seems promising, and its very early use after birth to detect kidney hemodynamic dysfunction deserves further investigations.