Near-Infrared Spectroscopy Demonstrates Changes In Cerebral Blood Volume, Oxygenation, And Metabolism In Premature Neonates During Bolus Gavage Feeding† 974

Abstract

Objective: To determine whether bolus gavage feeding (GF) causes changes in the cerebral vascular or metabolic status of premature neonates detectable by Near-Infrared Spectroscopy (NIRS). Background: Although GF is a routine neonatal practice, its effect on the premature infant's brain is unknown. NIRS is a safe, portable, noninvasive technique which monitors cerebrovascular and metabolic status by determining changes in cerebral concentrations of oxygenated hemoglobin (HbO), deoxygenated hemoglobin (HbR), total hemoglobin (THb) and oxidized cytochrome aa3 (cytaa3). THb is an index of cerebral blood volume and cytaa3 is the terminal electron acceptor in the mitochondrial respiratory chain whose redox status reflects cerebral metabolism. Methods: Fourteen premature infants (24-32 wk GA) receiving intermittent GF were studied 20 min before and up to 1h following a GF. NIRS and systemic parameters (SaO2, HR, RR) were monitored and recorded throughout the study. Eight infants were fed by intermittently passed orogastric tube (OGT) and six were fed by indwelling OGT. Changes in NIRS parameters were determined during OGT insertion and after bolus feed relative to pre-GF values. Data were analyzed during OGT insertion and during defined 5 min intervals following feeding, and analyzed by ANOVA for repeated measures, p<0.05. Results: OGT insertion decreased cerebral HbO and cytaa3 in 6/8 infants. THb was also decreased in 4/6 of these infants. Within 20 min of the feed infusion, THb decreased from baseline in 11/14 infants. In 8/11 of these infants, HbO and HbR were also decreased. Conclusions: Cerebral HbO and cytaa3 decreased during OGT insertion. In infants in whom THb also decreased during OGT insertion, changes in HbO and cytaa3 may be related to diminished cerebral blood flow. Decreased THb, HbO, and HbR after bolus feeds suggest that cerebral blood flow may decrease due to spanchnic steal. These findings highlight the cerebrovascular and metabolic reactivity of premature infants during routine nursery procedures. These changes in cerebral circulation and metabolism are detectable by NIRS but are not clinically evident or detected by routine monitoring. The significance of these changes in the preterm infant's brain is unknown and warrants further study.