Modulation of the inflammatory response induced during coronary artery bypass graft surgery

Introduction

Ischaemic preconditioning provides endogenous protection against ischaemia and also inflammation resulting from ischaemia reperfusion injury. A number of exogenous pharmacological substances including adenosine, bradykinin, noradrenaline and inhalational halogenated anaesthetic agents are recognised triggers of preconditioning.

Methods

The investigation was approved by the Royal Brompton, Harefield & NHLI research ethics committees. Patients scheduled for first-time coronary artery bypass grafting (CABG) surgery with triple-vessel coronary artery disease and at least moderate left ventricular function were recruited. Exclusion criteria included: age >80 years; unstable angina; noninsulin-dependent diabetes mellitus treated with KATP channel blockade; use of nicorandil or nitrate use within 24 hours of surgery. Preoperative risk variables were compared using the EuroSCORE. Patients were randomised to anaesthesia facilitated using halogenated inhalational agents or total intravenous anaesthesia (TIVA) (propofol). The surgical technique was standardised as far as possible. All cases necessitated the use of cardiopulmonary bypass. Inflammation was assessed up to 72 hours postoperatively using a combination of physiological and biochemical parameters. Physiological assessment consisted of the development of systemic inflammatory response syndrome (SIRS). Biochemical assessment consisted of measurement of plasma IL-6, myeloperoxidase and C-reactive protein. Blood samples were obtained preoperatively and at 5, 24, 48 and 72 hours postoperatively.

Results

SIRS was reduced in patients who received TIVA (P < 0.05, Fisher's exact test; n = 13 TIVA, n = 8 inhalational; Figure 1). Plasma IL-6, myeloperoxidase and C-reactive protein were elevated postoperatively although levels were unaffected by the mode of anaesthesia (P = not significant, two-way ANOVA; n = 13 TIVA, n = 8 inhalational).

Figure 1

Systemic inflammatory response syndrome (SIRS) post coronary artery bypass grafting.

Conclusion

We have demonstrated a protective benefit of TIVA on the development of SIRS postoperatively in patients undergoing CABG surgery. A larger double-blind randomised controlled trial is required to confirm these results.