Is "Attenuation of Oxidative Stress" Helpful to Understand the Mechanism of Remote Ischemic Preconditioning in Cardiac Surgery?

Abstract

Objectives: The aim of this study was to determine the effect of remote ischemic preconditioning (RIPC) on markers of cardiac ischemia and response to oxidative stress in patients undergoing coronary artery bypass grafting (CABG) surgery.

Design: A prospective, randomized, and blinded study.

Setting: A single-center university hospital.

Participants: This study included patients who underwent isolated CABG surgery with cardiopulmonary bypass who were selected carefully to prevent confounding with factors known to affect markers of ischemia-reperfusion and response to oxidative stress.

Interventions: The authors randomly assigned patients to RIPC to the left lower extremity using a blood pressure cuff (study group) or a cuff that was applied but not inflated or deflated (control group).

Measurements and main results: At 6 hours after CABG surgery, high-sensitivity cardiac troponin T levels were significantly lower in the study group than in the control group. Levels of superoxide dismutase, an antioxidant enzyme, were significantly greater 15 minutes after release of the cross-clamp in the study group, whereas malondialdehyde levels were lower (not significantly) at 1 and 15 minutes after release of the cross-clamp. Hemodynamic parameters were not significantly different at any time point during the study.

Conclusions: The authors' method of RIPC before CABG surgery resulted in less myocardial ischemia, as indicated by lower troponin levels. Changes in levels of endogenous antioxidant enzymes supported the hypothesis that this protection from ischemia-reperfusion injury was related to scavenging of free oxygen radicals. Future studies might include a more heterogeneous population and medications that lower the body's response to oxidative stress.

Keywords: ischemia-reperfusion injury (heart); oxidative stress; preconditioning (remote).