Patient characteristics of infants with no NEC and definite NEC.

Data are expressed as median (range) or as numbers unless specified otherwise. Abbreviations: NEC—necrotizing enterocolitis; NIRS—near-infrared spectroscopy; PDA—patent ductus arteriosus; PNA—postnatal age; RBC—red blood cell. Circulatory failure was defined as hemodynamic instability and scored by the need for volume expansion or the use of inotropes or both, from one hour before NEC onset until the first forty-eight hours after NEC onset, or until surgery, whichever came first. Statistical differences between the two groups are marked by * (