Effect of Slow Versus Rapid Advancement of Enteral Feeding on Intestinal Oxygenation in Preterm Infants

<b>Background/Objectives:</b> The optimal rate of enteral feeding advancement in preterm infants remains uncertain despite decades of clinical research. This uncertainty arises from concerns that rapid feeding progression may increase the risk of feeding intolerance and necrotizing enterocolitis (NEC), two major causes of morbidity and mortality in this population. The feeding rate may also influence intestinal oxygenation due to mesenteric hemodynamic changes during feeding. This study aimed to evaluate whether the rate of enteral feeding advancement (slow vs. rapid) affects intestinal oxygenation and its association with feeding intolerance (FI) or necrotizing enterocolitis in very low birth weight preterm infants. <b>Methods:</b> This prospective, randomized, two-center study included infants born at 28-32 weeks of gestation. Group 1 received slow advancement (20 mL/kg/day) and Group 2 rapid advancement (30 mL/kg/day) of enteral feeds. Splanchnic (srSO₂) and cerebral (crSO₂) oxygenation were monitored daily using the FDA-approved INVOS NIRS device during feeding periods (08:00-16:00). Monitoring was performed during minimal enteral nutrition (Phase 1), advancement phases (Phase 2), and for two days after achieving full enteral feeding (Phase 3). The splanchnic-to-cerebral oxygenation ratio (SCOR) was also calculated. Percentage changes in srSO₂ and SCOR during and after feeding were calculated from baseline (prefeeding) values and analyzed. <b>Results:</b> Sixty infants were enrolled. Mean gestational age and birth weight were 29.76 ± 1.33 weeks and 1375.05 ± 271.19 g, respectively. Group 2 achieved full enteral feeding significantly earlier (<i>p</i> = 0.001), with no other demographic differences between groups. No cases of NEC were observed. Feeding intolerance occurred in 14 infants (23.3%): 8 in Group 1 and 6 in Group 2 (<i>p</i> = 0.192). Both groups exhibited increased srSO₂ and SCOR during feeding; however, the between-group differences were not statistically significant (Phase 2 srSO₂ and SCOR: <i>p</i> = 0.07, 0.08; Phase 3 srSO₂ and SCOR: <i>p</i> = 0.069, 0.071). However, the percentage change from baseline in srSO₂ and SCOR during and after feeding was significantly greater in Group 2 during the advancement and full enteral feeding phases (Phase 2 srSO₂ and SCOR: <i>p</i> = 0.03, 0.022; Phase 3 srSO₂ and SCOR: <i>p</i> = 0.015, 0.048). Infants with feeding intolerance demonstrated significantly lower srSO₂ and SCOR values compared to tolerant infants, and this reduction persisted even after reaching full enteral feeding. ROC analysis suggested gestational age < 30 weeks, birth weight < 1180 g, srSO₂ < 52, and SCOR < 0.6 were associated with feeding intolerance. <b>Conclusions</b>: Intermittent bolus feeding increased intestinal oxygenation, with a more pronounced effect in the rapid advancement group. No difference in gastrointestinal adverse outcomes was observed between groups. Lower intestinal oxygenation was associated with feeding intolerance, and the suggested predictive criteria may help guide individualized feeding strategies.