Background The factors that determine the effect of enteral feeding on intestinal perfusion after preterm birth remain largely unknown. We aimed to determine the effect of enteral feeding on intestinal oxygen saturation (r(int)SO(2)) in preterm infants and evaluated whether this effect depended on postnatal age (PNA), postmenstrual age (PMA), and/or feeding volumes. We also evaluated whether changes in postprandial r(int)SO(2) affected cerebral oxygen saturation (r(c)SO(2)). Methods In a longitudinal observational pilot study using near-infrared spectroscopy we measured r(int)SO(2) and r(c)SO(2) continuously for two hours on postnatal Days 2 to 5, 8, 15, 22, 29, and 36. We compared preprandial with postprandial values over time using multi-level analyses. To assess the effect of PNA, PMA, and feeding volumes, we performed Wilcoxon signed-rank tests or logistic regression analyses. To evaluate the effect on r(c)SO(2), we also used logistic regression analyses. Results We included 29 infants: median (range) gestational age 28.1 weeks (25.1-30.7) and birth weight 1025 g (580-1495). On Day 5, r(int)SO(2) values decreased postprandially: mean (SE) 44% (10) versus 35% (7), P = .01. On Day 29, r(int)SO(2) values increased: 44% (11) versus 54% (7), P = .01. Infants with a PMA >= 32 weeks showed a r(int)SO(2) increase after feeding (37% versus 51%, P = .04) whereas infants with a PMA <32 weeks did not. Feeding volumes were associated with an increased postprandial r(int)SO(2) (per 10 mL/kg: OR 1.63, 95% CI, 1.02-2.59). We did not find an effect on r(c)SO(2) when r(int)SO(2) increased postprandially. Conclusions Our study suggests that postprandial r(int)SO(2) increases in preterm infants only from the fifth week after birth, particularly at PMA >= 32 weeks when greater volumes of enteral feeding are tolerated. We speculate that at young gestational and postmenstrual ages preterm infants are still unable to increase intestinal oxygen saturation after feeding, which might be essential to meet metabolic demands.
Trial registration: For this prospective longitudinal pilot study we derived patients from a larger observational cohort study: CALIFORNIA-Trial, Dutch Trial Registry NTR4153.