Packed Red Blood Cell Transfusion and Intestinal Blood Flow in Preterm Neonates

Necrotizing enterocolitis (NEC) is the death of intestinal tissue. It most often affects premature or sick babies. NEC occurs when the lining of the intestinal wall dies and the tissue falls off. NEC is a known complication of prematurity with high morbidity and mortality. About 7 to 13% of all very low birth weight infants admitted to Neonatal Intensive Care Units (NICU) develop NEC, with mortality ranging from 10 to 44% (1,2,3).

NEC is considered a multifactorial disorder converging on a common final clinical presentation associated with several etiologic mechanisms, including ischemia (eg reperfusion), infection (eg, gut colonization), mechanical injury (eg, viscosity, embolic), iatrogenic factors (eg catheters, excessive enteral feeding), and immunological barrier dysfunction (1,13,4,5) To date, there is no single, unifying consensus on causation (6).

Newly, the association between NEC and Packed Red Blood Cell (PRBC)transfusion has been a subject of recent debate. Several retrospective studies report increased incidence of NEC 22 hrs (7) or 48-72 hrs after PRBC transfusion (8) and increased odds of NEC development within 48 hrs posttransfusion (9). Singh, measuring the strength of association between the NEC and PRBC transfusion describes the association as strong < 24hrs, less strong < 48 hrs and absent at 96 hrs (10). Importantly, the majority of the infants in these studies were stable premature neonates on full enteral feeds, who decompensated and developed NEC after being transfused.

Based on poor or no evidence, many NICUs are implementing policy not to feed premature infants during the blood transfusion (11). A small recent prospective trial (8) reported decreased incidence of NEC (from 5.3 to 1.3%) when feeds are withheld during the transfusion. Similarly, the limited investigation of the superior mesenteric artery (blood vessel that supplies the greatest volume of blood to the intestinal tract) blood flow velocities (SMA BFV) revealed that the expected post-prandial increase in SMA BFV disappeared following the PRBC, placing the fed neonates receiving blood transfusion at higher risk for NEC (12).

This initial study had several major limitations, such as enrolling larger and more mature preterm neonates at lesser risk for PRBC transfusion related NEC, excluding infants with patent ductus arteriosus (PDA), common clinical condition in preterm neonates, losing 11 out of 22 patients for follow up studies (hence "normalization" of post-prandial blood flow velocities and finding potentially safe time point for feeds reintroduction could not be suggested by the study results) and using relatively less commonly transfused PRBC volumes over longer period of time.

In this study, the investigators intend to further their understanding of the hemodynamic consequences of PRBC transfusion in very low birth weight (VLBW) neonates by evaluating pre-and post-prandial SMA BFV in neonates who are not fed during the transfusion at different time points and correlate those with relevant clinical outcome measures. The investigators anticipate that the results from this study will be used by clinicians to help guide them in making decisions regarding the safety of administering PRBC transfusion in VLBW neonates.