Hypoxic/ischemic hits predispose to necrotizing enterocolitis in (near) term infants with congenital heart disease: a case control study

Background Necrotizing enterocolitis (NEC) is a devastating disease that is relatively frequently diagnosed in term infants with congenital heart disease (CHD), compared with term infants without CHD, in whom NEC is rare. The exact pathogenesis of NEC in term infants with CHD is unknown, but it is hypothesized that ischemia of the intestines plays a pivotal role. We aimed to explore whether (near) term CHD infants, who develop NEC, exhibit more clinical signs of hypoxia/ischemia and low body perfusion directly after birth and during the first 48 hours after admission to the neonatal intensive care unit, when compared with (near) term CHD infants who did not develop NEC. Methods 956 infants with CHD born after ≥ 35 weeks of gestational age were retrospectively reviewed for this case-control study between January 1999 and February 2020. We included infants with radiographically confirmed pneumatosis intestinalis and controls matched by type of CHD. Seven infants were diagnosed with transposition of the great arteries, six with left and four with right ventricular outflow tract obstruction. Several parameters suggestive of (relative) hypoxia/ischemia were used for analyses. Results We included sixteen CHD infants with NEC and selected sixteen controls. There were no significant demographic differences between both groups. Apgar score at one and five minutes (median [IQR]) were lower in infants who developed NEC compared with control infants (8 [7-8]) vs. (9 [8-9], P = .011) and (8 [8-9]) vs. (9 [9-10], P = .009). A higher proportion of infants with NEC required respiratory support in the delivery room (11(69) vs. 2(13), P = .001). The (median [IQR]) diastolic blood pressure on the second day after admission (39 mmHg [34–42], vs. 43 mmHg [37–51], P = .112) and lowest (median [IQR]) pH in the 48 hours after admission (7.24 [7.17–7.35] vs. 7.38 ([7.27–7.43], P = .157) were not significantly lower in NEC infants but both demonstrated a similar direction towards (relative) hypoxia/ischemia in NEC infants. Conclusions Our clinical results support a hypoxic/ischemic pathophysiology of NEC in (near) term CHD infants, with lower Apgar scores, more respiratory support in the delivery room and a tendency towards a lower diastolic blood pressure and pH in CHD infants who develop NEC.