(5) Evaluation of Kidney Oxygenation Compared to Intestinal Oxygenation and Feeding Timing in Preterm Neonates

Background: Kidney oxygenation monitoring with Near Infrared Spectroscopy (NIRS) is being used with increasing frequency in the neonatal intensive care unit (NICU). However, given the small size of neonates and the depth of light from the NIRS sensor, it is possible that kidney oxygenation measured on the flank includes or is impacted by intestinal oxygenation or enteral feeds.

Objectives: To evaluate kidney oxygenation changes based on enteral feeding timing and compare simultaneous intestinal oxygenation measured on the anterior abdomen to kidney oxygenation measured on the flank.

Design/Methods: A secondary analysis of a prospective observational study measuring kidney and intestinal oxygenation with NIRS was performed in neonates < 32 weeks’ gestation. Intestinal oxygenation was measured for three or four-hour increments with simultaneous kidney oxygenation monitoring in a subset of neonates. Additionally, mean kidney oxygenation was collected one hour prior to enteral feeding initiation, during an enteral feeding, and at one and two hours post feeding. Kidney oxygenation surrounding feedings were compared using Wilcoxon signed-rank test. T-test statistics were used to compare simultaneous kidney and intestinal oxygenation.

Results: Eleven subjects underwent simultaneous intestinal and kidney oxygenation monitoring with means statistically significantly different (p = 0.01) between the two groups and demonstrated in figure 1. Kidney oxygenation was compared 1228 times related to enteral feeding times (418 pairs from one hour prior to feeding and during feeding; 403 pairs from one hour prior to feeding and one hour post feeding; and 407 pairs from one hour prior to feeding and two hours post feeding). The median kidney oxygenation values for each time point are demonstrated in figure 2. There was no significant difference in kidney oxygenation between one hour prior to feeding and any of the subsequent time points (p= 0.09; p=0.90; p=0.23).

Conclusions: In this cohort, kidney oxygenation does not appear to be influenced by enteral feeding and are significantly different from simultaneous intestinal oxygenation. This study further validates NIRS monitoring for kidney oxygenation in preterm neonates.