Pro-inflammatory cytokines after different kinds of cardio-thoracic surgical procedures: is what we see what we know?

Abstract

Objective: Due to the combination of local trauma, extracorporeal circulation (ECC), and pulmonary and myocardial reperfusion, cardiac surgery leads to substantial changes in the immune system and possibly to post-operative complications. Procedures without ECC, however, have failed to demonstrate clear advantages. We hypothesized that ECC is far less important in this context than the reperfusion/reventilation of the lung parenchyma and the surgical trauma. We therefore conducted a prospective observational study to compare immune reactions after cardiac operations with those after thoracic surgery.

Methods: Serum levels of pro-inflammatory interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-alpha as well as C-reactive protein (CRP), lipoprotein-binding protein (LBP) and procalcitonin (PCT) were measured pre-operatively (d0), at the end of the operation (dx), 6h after the operation (dx+), on the 1st (d1), 3rd (d3), and 5th (d5) post-operative days in 108 patients (pts) undergoing elective coronary artery bypass grafting (CAB) with ECC (n=42, CPB CAB), off-pump coronary artery bypass surgery (n=24, OP CAB) without ECC or thoracic surgery (n=42, TS).

Results: After cardiac surgery (CS), IL-6 and IL-8 increased and reached a maximum on dx+. IL-6 returned to baseline values at d3, whereas IL-8 remained elevated until d5. No difference was found between OP CAB and CPB CAB patients. In the TS patients, IL-6 increased later (dx+) and absolute levels were lower than in the CS patients. No increase in IL-8 was noted in the TS patients. Due to the high variation in the results obtained in all three groups, there was no significant change in TNF-alpha. A comparison of TS, OP CAB, and CPB CAB revealed that the CS patients had higher levels on d0, dx, d3, and d5. Serum levels of CRP, LBP, and IL-2R increased from dx+ to d5 in all groups and reached maximum values on d3. Whereas we found no difference in CRP and IL-2R between the groups, LBP levels were significantly higher from dx+ to d3 after OP CAB. PCT was elevated from dx+ to d3 in all pts. Similar levels were noted for the TS and OP CAB patients. The CPB CAB patients showed the highest levels.

Conclusions: Surgical trauma and reperfusion injury appear to represent the predominant factors resulting in immunologic changes after cardiac surgery. Cardiopulmonary bypass (CPB) may be less important for immune response and acute-phase reactions than previously suspected. In addition, our data indicate a relationship between IL-6 synthesis and the degree of surgical trauma. IL-8 appears to be elevated only after cardiac surgery whereas PCT liberation depended on the use of ECC.