Measurement of endotoxin, IL-6, IL-8 and blood lactate after cardiac surgery: re-evaluation of the systemic inflammatory response induced by cardiopulmonary bypass

Introduction

Cardiopulmonary bypass (CPB) has been thought to induce endotoxemia and/or ischemia-reperfusion injury. These factors are believed to play an important role in the systemic inflammatory response following cardiac surgery with CPB. However, recent surgical advances made coronary artery bypass grafting (CABG) without CPB possible. In our study, we re-evaluate the relative contributions of CPB on the production of various mediators in patients who received cardiac surgery with CPB by comparing them with patients who received the off-pump coronary artery bypass grafting (OPCAB) procedure.

Methods

With institutional approval and informed consent, we studied: (1) the changes of endotoxin (ET) and beta-glucan (BG) during the perioperative period of cardiac operations performed with CPB (n = 15) or without CPB (n = 5) by using the kinetic turbidmetric assay (KTA) with ET-specific and BG-specific LAL reagents that allows separate determinations of ET and BG; and (2) the changes of interleukin-6 (IL-6), interleukin-8 (IL-8), and blood lactate during the perioperative period of CABG with CPB (n = 5) or without CPB (n = 5). Those were compared within the group and between the groups by ANOVA and other methods.

Results

(1) ET was not detectable at any time-point in any patients. In patients with CPB, BG rose in a time-dependent fashion, reaching a maximum (130.2 ± 93.1 pg/ml) at 2 hours after the initiation of CPB, then gradually decreased. No BG elevations were observed in patients without CPB. (2) IL-6 and IL-8 were elevated on ICU admission in both groups, but no significant differences were observed between the groups. In patients with CABG with CPB, blood lactate increased from ICU admission to 12 ICU hours compared with OPCAB patients, and decreased to the same level as those in OPCAB patients on 24 ICU hours.

Discussion

These results indicate that CPB does not affect the production of endotoxin, IL-6 and IL-8. Other factors may contribute to the rise in blood lactate. Further studies are needed to clarify the relationship between CPB and the postsurgical inflammatory response.