Splanchnic tissue oxygenation, but not brain tissue oxygenation, increases after feeds in stable preterm neonates tolerating full bolus orogastric feeding

Objective: The objective of this prospective, observational study was to test the hypothesis that tissue oxygenation in the splanchnic bed compared with tissue oxygenation in the cerebral circulation changes after feeding in preterm neonates who are tolerating full bolus orogastric feeds. Study Design: Clinically stable premature neonates with postmenstrual age between 32 and 35^6/7 weeks who were tolerating full bolus feedings were studied before feeding and 1h after feeding using near-infrared spectroscopy. The ratio of oxygenated to reduced hemoglobin (tissue oxygenation index, TOI) in the splanchnic circulation bed was divided by the TOI in the cerebral circulation, thereby yielding the cerebro-splanchnic oxygenation ratio (CSOR). We compared TOI and CSOR before and after feeding. As the changes in TOI and CSOR had non-Gaussian distribution, nonparametric statistics were used. Result: Among 32 infants, CSOR increased significantly after feeding (median difference 0.08; range -0.48, +0.58; P = 0.011), whereas pulse oximetry did not change significantly (P=0.600). The change in CSOR with feeding was associated with a significant increase in splanchnic TOI (preprandial median 43.8, range 25.2 - 68.4 vs postprandial 47.5, range 25.8 - 70.8; P = 0.013), without any significant change in brain TOI (preprandial median 64.9, range 44.5 - 75.4 vs postprandial 58.9, range 42.2 - 72.3; P = 0.153). Conclusion: This study indicates that CSOR and splanchnic TOI, but not brain TOI, increase significantly after feeding in stable preterm infants who are tolerating full orogastric feeds.