Red blood cell (RBC) transfusion is often required during cardiac surgery in children. However, RBC is a rare product, and its transfusion is associated with adverse events and a worse surgical outcome. Characterization of factors related to RBC transfusion during cardiac surgery in children would provide prevention strategies.

We conducted a retrospective single-center study, including all children who underwent their first cardiac surgery using bloodless priming cardiopulmonary bypass (CPB).

The study included 173 children between 2011 and 2019,; 57 had intraoperative transfusion and 17 postoperative transfusion. Age (OR: 0.76, p<0.001), weight (OR: 0.93, p<0.001), body mass index ([BMI] OR: 0.83, p<0.001), hemoglobin level (OR: 0.68, p<0.05), hematocrit level (OR: 0.88, p<0.05), mean corpuscular volume ([MCV] (OR: 0.86, p<0.001), hemodilution (OR: 100, p<0.01), and CPB duration (OR: 1.01, p<0.05) were associated with an increased risk of intraoperative transfusion in univariate analysis. In multivariate analysis, only CPB duration (OR: 1.02, p<0.001) and MCV (OR: 0.89, p<0.05) were associated with transfusion. Concerning postoperative transfusions, the RACHS surgical difficulty score (OR: 6.83, p<0.01), duration of CPB (OR: 1.01, p<0,001), length of stay in the PICU (OR: 2.37, p<0.001), length of hospitalization (OR: 1.2, p<0.001), and reoperation (OR: 20.59, p<0.001) were significant using univariate analysis, and only the need for a reoperation (OR: 19.16, p<0.01) remained significant in multivariate analysis.

Low MCV appears to be one of the main risk factors for intraoperative transfusion in RBC. It may reflect iron deficiency that should be checked and supplemented preoperatively in order to reduce the risk of transfusion.