A pilot prospective study of the vascular repair response following red cell transfusion in critically ill patients

Background Red blood cell transfusion has been associated with adverse outcomes including infection, delayed recovery and increased mortality in some patient populations. Circulating cells that yield endothelial-like vascular progenitor cell (VPC) clusters are correlated with vascular repair and recovery after ischaemic injury. The impact of red cell transfusion on VPC clusters and vascular repair remains uncertain. Study design We prospectively enrolled patients admitted to intensive care requiring red cell transfusion and subjects at low likelihood of requiring red cell transfusion. Levels of VPC clusters and plasma levels of angiogenic cytokines were compared. A total of 17 patients were recruited and had blood samples collected at time of enrolment and at 2448h, 4872h and 1 week following transfusion. Results We could not discern differences in the number of VPC clusters between transfused patients (n=6) and non-transfused subjects (n=11) at baseline or throughout the study period. VPC cluster levels demonstrated wide variance and were highest at 24-h post-enrolment in the entire cohort. Furthermore, levels of all 16 cytokines analysed were not significantly different between transfused and non-transfused patients and we did not observe a correlation between cytokine concentrations and levels of circulating VPC-cluster forming cells in the overall study population. Conclusions Our data suggest that assessment of vascular repair responses after red blood cell transfusion in critically ill patients is challenging. Although our study did not allow us to discern an influence of red cell transfusion on VPC cluster levels or angiogenic cytokines, new methods evaluating vascular repair mechanisms may be required.