Objective

To evaluate the effects of cardiopulmonary bypass (CPB) on peripheral white blood cell counts, neutrophil surface marker expression, and neutrophil function by comparing patients undergoing on-pump CABG (ONCAB) versus off-pump CABG (OPCAB), and to identify CPB-related immunological and inflammatory alterations.

Methods

Patients undergoing on-pump CABG (ONCAB) or off-pump CABG (OPCAB) were recruited. Blood samples were collected preoperatively and at 24 h postoperatively. The primary outcome was the neutrophil-to-lymphocyte ratio (NLR) measured at 24 h after surgery. Secondary outcomes included monocyte Human leukocyte antigen-DR (HLA-DR) expression, lymphocyte programmed cell death protein-1 (PD-1) expression, and neutrophil surface markers (CD11b, CD18, CXCR2, CD35, CD63, CD66b, CD88, and programmed cell death-ligand 1). Neutrophil apoptosis, reactive oxygen species (ROS) production, and plasma inflammatory mediators (interleukin-6, tumor necrosis factor-alpha, interleukin-10) were also measured. Postoperative clinical outcomes and laboratory parameters were recorded.

Results

Data from 36 ONCAB patients and 18 OPCAB patients were analyzed. Postoperative NLR was significantly higher in the ONCAB group than in the OPCAB group (16.6 ± 6.1 vs. 13.1 ± 3.9; p = 0.015). This difference was attributable to lower lymphocyte counts in the ONCAB group (0.7 ± 0.2 vs. 0.8 ± 0.2 × 10⁹/L; p = 0.002), whereas neutrophil counts did not differ significantly between groups. In both groups, monocyte HLA‑DR expression decreased and lymphocyte PD-1 expression increased after surgery. CPB did not result in significant alterations in neutrophil adhesion, chemotaxis, degranulation markers, ROS production, or apoptosis. ONCAB patients had higher postoperative levels of aspartate aminotransferase (AST), cardiac troponin I (cTnI), and procalcitonin (PCT), as well as longer durations of mechanical ventilation and intensive care unit stay.

Conclusions

CPB elevates the NLR after CABG primarily, accompanied by reduced level of lymphocyte count, but not neutrophil count or molecular markers of neutrophil functional. These results might reflect a higher risk of short-term complications after on-pump CABG.