Changes in regional oxygen saturation of the kidney and brain of infants during hospitalization

Background In pre-term infants, the postnatal changes in the regional oxygen saturation (rSO 2 ) of the brain and kidney are unclear. Methods We performed a prospective observational study. We measured the cerebral/renal rSO 2 ratio and recorded the associated clinical features of infants born at 23 to 41 weeks of gestation weekly from the early postnatal period to discharge. Results The median cerebral/renal rSO 2 ratios (interquartile ranges) between birth and the expected date of birth were 1.13 (1.06–1.26) at 23–24 weeks (n = 7), 1.18 (1.10–1.32) at 25–26 weeks (n = 11), 1.24 (1.11–1.37) at 27–28 weeks (n = 9), 1.12 (1.05–1.19) at 29–30 weeks (n = 4), 1.11 (1.03–1.15) at 31–32 weeks (n = 5), 1.02 (0.98–1.06) at 33–34 weeks (n = 9), 0.98 (0.94–1.06) at 35–36 weeks (n = 19), and 0.95 (0.86–0.99) at 37–41 weeks of gestation (n = 22). The median cerebral/renal rSO 2 ratio did not significantly change after birth, but with increasing gestational age, the cerebral/renal rSO 2 ratio at the expected date of birth decreased (r = − 0.74, p < 0.001). Nephrotoxic drugs did not affect cerebral/renal rSO 2 at the expected date of birth, after adjustment for clinical factors. Conclusions Unlike in most infants born after the late pre-term period, the renal rSO 2 remained lower than the cerebral rSO 2 on the expected date of birth in infants born very pre-term.