Altered kinetics of circulating progenitor cells in cardiopulmonary bypass (CPB) associated vasoplegic patients: A pilot study

Abstract

Vasoplegia observed post-cardiopulmonary bypass (CPB), is associated with substantial morbidity, multiple organ failure and mortality. Circulating counts of hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPC) are potential markers of neovascularization and vascular repair. However, changes in the circulating levels of these progenitors in perioperative CPB and their association with post-CPB vasoplegia remains to be determined. HSC and EPC counts were enumerated at different timepoints during CPB in 19 individuals who underwent elective cardiac surgery via flow cytometry. These 19 individuals were categorized into two groups based on severity of post-operative vasoplegia as: clinically insignificant vasoplegic Group 1 (G1) and clinically significant vasoplegic Group 2 (G2). The differential changes in progenitor cell counts during different stages of surgery were compared across these two groups.Machine-learning classifiers (logistic regression and gradient boosting) were employed to determine if differential changes in progenitor counts could differentiate and group subjects based on the severity of vasoplegia. Enumeration of progenitor cells revealed an early and significant increase in the circulating counts of CD34 + and CD34 + CD133 + hematopoietic stem cells (HSC) in G1 subjects which was attenuated in G2 individuals.Additionally, EPCs (CD34 + VEGFR2 + ) were lower in G2 individuals compared to G1.Gradient boosting outperformed logistic regression in assessing the vasoplegia grouping based on fold change in circulating CD 34 + levels. Our findings indicate that a lack of early response of CD34 + cells and CD34 + CD133 + HSCs might serve as an early marker for development of clinically significant vasoplegia after CPB.