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Abstract

Introduction: Impaired total or regional oxygen delivery in children recovering from heart surgery often leads to feeding intolerance. Cerebral and splanchnic near-infrared spectroscopy (NIRS) have been established as a measure of oxygen delivery in children with congenital heart defects, but the use of a regional abdominal probe has not been correlated with feeding intolerance. Methods: This quality improvement initiative was instituted to standardize the use of continuous NIRS monitoring in all infants undergoing heart surgery and incorporate the use of abdominal NIRS probes during the initiation and advancement of feeds. Data were collected from 3/2012 to 1/2013 in infants expected to take longer than 24 hours to reach full volume feeds and included both cyanotic and acyanotic lesions. Cerebral and splanchnic probes were placed at the time or shortly after admission to the Pediatric Cardiac Intensive Care Unit. An abdominal probe was placed at a minimum of 2 hours prior to the initiation of feeds. We estimated abdominal (rSO2A) cerebral (rSO2C) and splanchnic (rSO2S) oxygen extraction as the difference between systemic saturation and cerebral, splanchnic and abdominal NIRS values respectively. Among a cohort of 19 patients, 9 had at least one episode of feeding intolerance (group FI), defined as interruption of feeds due to gastrointestinal (GI) symptoms, while 10 did not (group FT). We compared rSO2A between these two groups using Wilcoxon Rank Sum tests and correlated rSO2A with other non-invasive surrogates of cardiac output (rSO2C, rSO2S) using Spearman’s rank correlation. Results: Median age and weight at surgery were 8 days (interquartile range 5, 102) and 3.3 kg (2.7, 4.5). Single ventricle physiology was present in 2/9 FI and 6/10 FT patients. Median rSO2A was higher in the FI group [56% (47%, 66%) vs. 49% (32%, 62%), p<0.001]. The proportion of patients with a lowest rSO2A>35% was similar [FI 3/9 vs. FT 3/10, p=0.63]. In the FI group median rSO2A prior to feeding interruption was 51% (42%, 55%). Median change in rSO2A from first measurement to first feeding intolerance was significantly higher than median change in rSO2A from first measurement to full feeds observed in FT infants (16% (7%, 27%) vs 3.5% (-4%, 13%), p=0.03). Overall, correlation between rSO2C and rSO2A was poor (0.29), but improved at the time of feeding intolerance (0.74). Results were similar when correlating rSO2S and rSO2A (0.51 and 0.89). Conclusions: Median abdominal oxygen extraction was higher in infants with feeding intolerance, and increase in extraction was greater with advancement of feeds compared to infants without feeding intolerance. While overall correlation with cerebral oxygen extraction was poor, it improved at the time of feeding intolerance. Further studies using abdominal NIRS measurements are warranted.