The cellular immunological responses of patients undergoing coronary artery bypass grafting compared with those of patients undergoing valve replacement.

Objective: Major surgical intervention such as cardiac surgery has been shown to have profound effects on the immune system. We conducted a prospective study comparing the effects of coronary artery bypass grafting (CABG) versus isolated valve surgery.

Methods: Blood samples were drawn from 59 patients undergoing either elective CABG or elective isolated valve replacement surgery. Samples were obtained preoperatively and on the first and third postoperative days. Total cell counts and differential counts were recorded. Several cellular immunity parameters were determined by flow cytometry.

Results: On all postoperative days, significant increases in white blood cell (WBC) and monocyte counts were observed. Significant decreases in all lymphocyte populations were also observed with similar decreases in both helper (CD4) and suppressor (CD8) T cells. An increase in activated T cells was noted on day 1, returning to normal on the third postoperative day. Despite the significant decrease in human leucocyte antigen-DR (HLA-DR) antigen expression on monocytes on both the first and third postoperative days, a significant increase in monocyte activation as represented by increased CD11b and CD64 expression was detected. No significant difference was found for any of the measured parameters between the CABG group and the valve replacement group. Eight patients developed early wound infections, with no correlation with any of the measured parameters, including magnitude and duration of decrease in HLA-DR antigen expression on monocytes.

Conclusions: Cardiac surgery induces both a state of pro-inflammation and of immune suppression. The two major types of cardiac surgery induce similar effects to the immune system. None of the measured parameters was predictive for development of postoperative wound infection.