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

In pre-term infants, the postnatal changes in the regional oxygen saturation (rSO₂) of the brain and kidney are unclear.

We performed a prospective observational study. We measured the cerebral/renal rSO₂ 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.

The median cerebral/renal rSO₂ 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 rSO₂ ratio did not significantly change after birth, but with increasing gestational age, the cerebral/renal rSO₂ ratio at the expected date of birth decreased (r = - 0.74, p < 0.001). Nephrotoxic drugs did not affect cerebral/renal rSO₂ at the expected date of birth, after adjustment for clinical factors.

Unlike in most infants born after the late pre-term period, the renal rSO₂ remained lower than the cerebral rSO₂ on the expected date of birth in infants born very pre-term.