Red Blood Cell Transfusion and Digestive Tract Oxygenation in Preterm Infants Weighing ≤ 1250 Grams

Necrotizing Enterocolitis (NEC) is a leading cause of neonatal morbidity and mortality in preterm infants. To date, no effective genetic or clinical markers exist to predict which premature infant will develop NEC, limiting targeted prevention strategies. Anemia and digestive tract complications are common problems in extremely low birth weight infants. Anemia is a condition in which the body does not have enough red blood cells (RBC). RBCs are important because they contain hemoglobin, the substance that carries oxygen throughout the body. Transfusions of RBCs in these infants is frequently required to correct the anemia.

Multiple observational studies have reported an association between the exposure to red blood cell (RBC) transfusion and the subsequent development of transfusion related-NEC (TR-NEC).However, no clinical studies have investigated the underlying pathophysiologic mechanisms of TR-NEC. In adults, prolonged RBC storage prior to transfusion has been associated with adverse outcomes and may also contribute to TR-NEC. However, the chronological storage age of blood may not be an accurate gauge of donor RBC function; irradiation of RBCs to prevent transfusion-associated graft-vs-host disease may also contribute to TR-NEC. Currently, the duration considered safe for RBC storage following irradiation (irradiation storage time (IST)) is unclear. Given the multifactorial etiology of NEC, preventative efforts will be more successful if clinicians understand the underlying pathophysiologic mechanisms and modifiable risk factors.

In this study the researchers will conduct a multicenter observational cohort study of very preterm (VPT) infants weighing ≤1250g at birth to prospectively investigate the associations between RBC transfusion, digestive tract oxygenation, and TR-NEC. The overarching hypothesis for this study is that irradiation of RBC units followed by prolonged storage perturbs RBC metabolism and function, and these derangements are associated with paradoxical microvascular vasoconstriction, tissue hypoxia and TR-NEC in transfused infants with already impaired gut oxygenation due to significant anemia. All RBC units transfused to VPT infants throughout the study will be stored based on current standard operating procedures per local site blood banking practices. There will be no study-specific approaches to transfusions or transfusion thresholds, and the decision to transfusion will be made as part of current clinical care by the treating clinicians. No study-specific blood draws will occur and all samples will be obtained from residual samples collected for clinical care that are to be discarded.

Oxygen levels in the digestive tract will be measured before, during and after each blood transfusion using a tissue oxygen monitor called Near Infrared Spectroscopy (NIRS). By using this technology, the researchers intend to better understand intestinal blood flow patterns. RBC function in RBC products transfused to infants will be compared between the infants who develop TR-NEC and matched control infants who do not develop TR-NEC. The researchers will explore the clinical implications of severe anemia when infants are 28 to 34 weeks of postmenstrual age, which is when infants are vulnerable to NEC.

Currently, there are no inexpensive, simple, patient/healthcare provider-operated hemoglobin tests available for diagnosing and assessing the degree of anemia without the use of a blood draw. To that end, Emory investigators have recently developed an algorithm that enables patients/healthcare providers to check if a patient is anemic by simply taking a picture of their fingernail beds on a Smartphone, and running the algorithm on a computer using MATLAB. These studies have shown that the degree of pallor in the fingernail beds, correlates with physiologic levels of hemoglobin in the blood and determines whether or not the patient is anemic. To date, the accuracy of this device has only been tested on adults and older children. Having an accurate and noninvasive means of testing for anemia in VPT infants would reduce the number of blood draws required, decrease the common side effects of phlebotomy, transfusion of RBCs, and would potentially be more cost-effective. As an additional study aim, the researchers of this study seek to develop a new image analysis algorithm (IAA) to predict hemoglobin level and anemia status from fingernail photos. The fingernail beds of VPT infants are extremely small and therefore it is uncertain if the nail bed is the most accurate site to assess anemia in these infants. To determine which site is most accurate in this population pictures will be taken of the fingernail beds, the toe nail beds, the palm of the hand and the sole of the foot with be photographed and analyzed.