Mechanisms of Endotoxin-Tolerance of Human Monocytes After CABG-Sugery - Effects of Hemofiltration and Mannitol Treatment

Background Cardiac surgery using cardiopulmonary bypass (CPB) causes a systemic inflammatory response. In addition to this immune response to CPB, a significant impairment of the responsiveness of peripheral blood mononuclear cells (PBMC) to further immunological stimuli has been observed. The aim of our present study was to evaluate the ability of antioxidant therapy with mannitol or hemofiltration during CPB to modulate the observed immunosuppression after CPB.

Methods With ethics committee approval, 52 patients undergoing elective CABG-surgery were prospectively enrolled and randomized into 3 groups (control, 50 g mannitol iv, hemofiltration during CPB). Blood samples were taken after induction of anesthesia (T1), 20 min after separation from CPB (T2) and 24 h postoperatively (T3). Expression density of the monocytic surface receptor CD14, HLA-DR expression and cytokine release (TNF- and IL10) after LPS-stimulation were evaluated.

Results At T2, the CD14dim cell population was maintained in both intervention groups while in the control group there was a significant decrease of this proinflammatory monocytic phenotype. At T3, all groups developed a significant shift towards the antiinflammatory CD14bright population. No significant differences regarding HLA-DR expression or cytokine release could be demonstrated.

Conclusion This study shows that the suppression of the stimulated immune response after CPB can be alleviated by iv administration of mannitol or hemofiltration. In the light of data showing that this depression of the immune response might affect the postoperative course of patients, these results could lead to an improvement of the management of patients undergoing cardiac surgery with CPB.