Background
To investigate regional splanchnic and cerebral tissue oxygen saturation in preterm infants <30 weeks gestation.

Methods
Cerebral (cTOI) and splanchnic (sTOI) Tissue Oxygenation Index were measured weekly in 5 min epochs for a total period of 60 min using NIRS (NIRO-300) for the first 8 weeks of life, in 48 appropriately grown preterm infants born at <30 weeks gestation. Infants who developed HPI and/or NEC (n = 12) and those that died (n = 1) were excluded from our main outcome measure of regional gut and cerebral tissue oxygenation in healthy preterm infants <30 weeks gestation.

Results
Median birthweight 789 g (460–1486), gestational age 25+6 weeks (23+0–29+1) and 51.4% female. 217 NIRS measurements were completed across the first 8 weeks of life. Mean weekly cTOI ranged from 56.8–65.4% and sTOI ranged from 36.7–46.0%. Mean cTOI was significantly higher than mean sTOI (p < 0.001) throughout the first 8 weeks of life. Mean cTOI decreased significantly with increasing postnatal age [−0.59% each week (−1.26% to −0.07%) p = 0.04]. None of the examined confounding factors had a significant effect.

Conclusions
This is the first report of regional cerebral and splanchnic tissue oxygen saturation ranges during the first 8 weeks of life for preterm infants born at <30 weeks gestation.