660 - Characterizing Patterns of Intestinal Oxygenation in Preterm Infants with and without Necrotizing Enterocolitis

Publication Number: 1637.660

Bella Anadkat, Mary Institute and Saint Louis Country Day School, Saint Louis, MO, United States; Samer Bou Karroum, Washington University in St. Louis School of Medicine, St Louis, MO, United States; Halana Whitehead, Washington University in St. Louis School of Medicine, St. Louis, MO, United States; Zachary A. Vesoulis, Washington University School of Medicine, St. Louis, MO, United States

Background: Necrotizing enterocolitis (NEC) is a devastating complication of prematurity, impacting around 7% infants born before 32 weeks gestation. NEC is associated with the highest morbidity and mortality rates among preterm infants, with mortality rates of 20-30%, increasing to 50% when surgical intervention is required. NEC is a complex disease without a clear singular cause and non-specific presenting symptoms. Efforts to reduce NEC include strict feeding regimens, probiotics, and promotion of breastfeeding, yet early prediction remains a challenge. Near-infrared spectroscopy (NIRS) is a noninvasive method for measuring oxygenation in specific tissues. NIRS has been extensively used to study patterns of cerebral and renal oxygenation in preterm infants, but there has been comparatively little study of abdominal oxygenation.

Objective: The aim of this study was to characterize longitudinal intestinal oxygenation in preterm infants with and without NEC.

Design/Methods: Preterm infants born < 32 weeks were recruited to the study. Each participant underwent weekly abdominal NIRS monitoring, 6-8 hours in length, using INVOS 5100 or ForeSight Elite NIRS monitors from birth until discharge. The mean value of each recording was calculated, and the longitudinal trajectory was calculated using LOESS smoothing (R version 4.5.0).

Results: The study included 1976 recordings from 194 infants: 98 female and 96 male. The majority of values fell between 60% and 80%, with a mean value of 71.9% for all recordings across the entire cohort (Figure 1). All infants followed a similar trajectory over the course of hospitalization, with an initial period of stable intestinal oxygenation, a steep drop, followed by recovery. The initiation of the decrease was observed earlier for NEC infants compared to those without NEC, ~15 days of life and ~25 days of life, respectively. More mature infants-those born 28-32 weeks GA-had a drop in rSO2 to ~52%, while less mature infants had a less severe drop to ~65% (Figure 2). There was not a notable distinction between infants with different types of NEC; however, those without NEC observed a more significant drop-15% change versus ~5% change (Figure 3).

Conclusion(s): Preterm infants have dynamic changes in intestinal oxygenation. The overall pattern closely mirrors the onset of anemia, a common complication of prematurity and the consequence of frequent lab draws during NICU stays. This study identifies, for the first time, a potential early signature of NEC-of all natures-as an early drop in intestinal oxygenation within the first two weeks of life.

Figure 1: Distribution of Abdominal rSO2 Values
Distribution of individual abdominal rSO2 values with mean and median values for the entire cohort.

Figure 2: rSO2 Trajectories by Gestational Age Category
The chart represents rSO2 trajectories for extremely, very, and moderately-late preterm infants. Those born 28-32 weeks gestational age (GA) saw a more severe drop in rSO2 percentage than those born earlier, less than 28 weeks GA.

Figure 3: rSO2 Trajectories by NEC Status
rSO2 trajectories for infants with surgical, medical, or no necrotizing enterocolitis are shown. Infants with medical and surgical NEC saw a drop in rSO2 about 10 days earler than those without NEC.