Background: Most preterm infants with a gestational age <32 weeks in the neonatal intensive care unit (NICU) undergo blood transfusion therapy during their hospital stay to enhance their oxygen-carrying capacity and improve the oxygenation of vital organs. However, anemia and blood transfusions can lead to intestinal damage. Bedside abdominal ultrasonography and near-infrared spectroscopy (NIRS) are widely applied to monitor intestinal injury and oxygen perfusion. We hypothesized that in preterm infants (gestational age <32 weeks) with anemia and indications for transfusion, signs of intestinal injury detected by abdominal ultrasound and NIRS may appear earlier than clinical symptoms, signs, and other auxiliary examinations. Herein, we present the protocol of a study designed to assess whether abdominal ultrasonography and NIRS could therefore improve the timeliness, sensitivity, and accuracy of intestinal injury diagnosis, thereby improving prognosis.

Methods: This prospective observational study will enroll infants with a gestational age between 23+0 and 31+6 weeks with neonatal anemia, who meet the criteria for blood transfusion, and scheduled to receive transfusion therapy. In addition to routine clinical symptoms, signs, and other auxiliary examination monitoring during the transfusion process, abdominal ultrasound and NIRS findings will be analyzed. The primary outcome is the prediction intestinal injury related to anemia/transfusion using ultrasound and NIRS. A sample size of 100 cases has been set.

Conclusion: The etiology of transfusion-associated neonatal enterocolitis (TANEC) remains unclear and may result from multiple factors. Several prospective studies have assessed the significance and advantages of abdominal ultrasound combined with NIRS for monitoring intestinal injury in anemic states and transfusion therapy. Therefore, this trial aims to test the following hypothesis: monitoring intestinal injury in preterm infants (gestational age < 32 weeks) with anemia receiving red blood cell transfusions using abdominal ultrasound and NIRS can provide real-time information on changes in intestinal oxygenation during transfusion, to identify specific signs and trends in the digestive system prior to clinical symptoms and other auxiliary examination methods, thereby guiding and adjusting clinical decisions more accurately, sensitively, and rapidly. Thus, monitoring could reduce or prevent the occurrence and progression of intestinal injury, thereby improving long-term survival and prognosis.

Inclusion Criteria:

• 1. preterm infants with a gestational age between 23+0 and 31+6 weeks, 2. infants hospitalized in our hospital's NICU after birth, receiving a blood transfusion during hospitalization; and 3. infants whose parents provide written informed consent.

Exclusion Criteria:

• 1. Presence of severe congenital malformations or chromosomal abnormalities, 2. anemia due to acute blood loss; 3. presence of severe hemodynamic disorders, coagulation dysfunction, and disseminated intravascular coagulation (DIC); 4. presence of neonatal necrotizing enterocolitis, sepsis, or severe infectious conditions such as septicemia that remain uncorrected before transfusion; 5. congenital hematological diseases (such as pure red cell aplasia); 6. death due to other complications; 7. incomplete data; 8. infants participating in other interventional studies; and 8. infants whose parents do not consent to their participation.

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