Relations between feeding intolerance and stress biomarkers in preterm infants

Objectives: Feeding intolerance (FI) in preterm infants is common but the etiology remains unclear. This study examined FI as a stress-related disease involving brain-gut interactions and tested the model of allostatic load and complications of prematurity. Specific aims were to describe demographic/medical variables and biomarker levels at each time and over time for the sample; describe/compare variables and biomarker levels at each time for infants with/without FI; and compare biomarker interquartile/interpercentile distributions between infants with/without FI. Methods: Preterm infants <32 weeks' gestation were recruited. The primary outcome was FI by day 7 defined as a feeding withheld, discontinued, or decreased because the infant was not tolerating enteral feedings. Allostatic load was operationalized using cortisol and 8-hydroxydeoxyguanosine (8-OHdG) from cord blood and from saliva and urine on days 1, 7, and 14. Descriptive statistics and comparative analyses were performed. Results: Seven of 31 infants enrolled met criteria for FI. Infants with FI had lower median urinary cortisol on day 1 (P=0.007) and trended to have lower cortisol in the cord blood (P=0.056). Interquartile distributions were significantly different between infants with/without FI for urinary cortisol on day 1 (P=0.034) and trended for differences in 8-OHdG on day 14 (P=0.087). Interpercentile distributions were significantly different in salivary cortisol on day 14 (P=0.034) and trended for differences in 8-OHdG on day 1 (P=0.079). Conclusions: Results support further testing of the model in a larger sample; investigation of the cellular mechanisms associated with the stress and the free radical/antioxidant systems; and inclusion of prenatal factors.