The effects of feeding on blood flow to the gut in preterm infants receiving red blood cell transfusion

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Background: Development of anaemia in preterm infants is a common occurrence during hospitalisation as a result of iatrogenic blood loss and poor erythropoiesis. A significant proportion of extremely preterm infants are exposed to one or more RBC transfusions during their neonatal intensive care unit (NICU) stay. The association between red blood cell (RBC) transfusions and the development of necrotizing enterocolitis (NEC) in preterm infants was first recognized in the late 1980’s and has since been increasingly recognized. This association between RBC transfusion and NEC may coincide as a result of the timing of their occurrence, as most preterm infants will receive transfusions within the first 4 weeks of life, which is the same time frame for the development of NEC. Mechanisms related to the development of TANEC are unknown. Several hypotheses have been proposed including the prolonged storage of blood, increased viscosity of blood, perfusion-reperfusion injury and enteral feeding. The effect of enteral feeding during RBC transfusion on the mesenteric perfusion and oxygenation has not been fully elucidated. Due to the association between NEC and feeding practices in the preterm infants, there have been concerns about the effects of feeding during RBC transfusion. As a result, there is a wide variety of feeding practices during RBC transfusion of preterm infants including withholding of feeds to reduce the risk of NEC. Technological advances in near-infrared spectroscopy (NIRS) have allowed for the measurement of oxygenated and deoxygenated haemoglobin within tissue in real time. NIRS is able to measure changes in signals received via the skin sensors and calculate the proportion of haemoglobin in oxygenated and deoxygenated states from a mixed capillary, venous and arterial sample in the tissues approximately 2cm below the sensor placement. This allows for the non-invasive real-time measurement of the balance between oxygen supply and tissue demand. This technology has allowed for the continuous measurement of tissue oxygenation of the cerebral and splanchnic beds and for demonstration of differential tissue perfusion during periods of haemodynamic instability, anaemia and RBC transfusions. Autoregulation of brain perfusion allows for the oxygenation of the brain to be preserved except in the most severe situations. Thus, a ratio of cerebral splanchnic oxygenation has been proposed to be able to measure changes in gut perfusion. Aim: To assess the effect of feeding and withholding of feeding on gut oxygenation and perfusion in preterm infants receiving RBC transfusions. Hypothesis: We hypothesize that mean CSOR and mean mesenteric FOE during RBC transfusion will not be different between preterm infants in the withheld group and the full volume group.