Myocardial metabolism altered by ischemic preconditioning and enflurane in off-pump coronary artery surgery.

OBJECTIVE

During off-pump coronary artery bypass (OPCAB) surgery, the heart is subjected to ischemia and reperfusion. The authors hypothesized that the volatile anesthetics are as effective as ischemic preconditioning (IPC) in preserving myocardial function during off-pump cardiac surgery, and this effect is because of multiple mechanisms of action. Therefore, the effects of enflurane with its calcium inhibition and antioxidative properties were compared with mechanical IPC in preserving myocardial cellular markers.

DESIGN

A prospective, randomized, controlled, and partly blinded study.

SETTING

A tertiary care university hospital.

PARTICIPANTS

Twenty-five patients undergoing elective single-graft OPCAB surgery.

INTERVENTIONS

Patients were randomized into 3 groups: (1) control (n = 8), (2) a single 5-minute ischemia/reperfusion interval of IPC before coronary occlusion (n = 9), and (3) 1.6% enflurane anesthesia 15 minutes before and during graft attachment (n = 8). Arterial and coronary sinus venous blood were analyzed for biochemical indices of ischemia and hydroxyl radical generation.

MEASUREMENTS AND MAIN RESULTS

Although the hemodynamic changes were small, myocardial lactate production in the control group increased by 120%, whereas in the enflurane group it decreased significantly (p < 0.01) compared with the control and IPC groups. Oxygen utilization in the control group was 44% higher (p < 0.03), and there was also a larger release of the hydroxyl radical-dependent adduct 2,3-dihydroxybenzoic acid (225% increase, p < 0.05) compared with both study groups. During reperfusion, initial anterior wall hypokinesis by TEE was observed, with slow recovery during reperfusion compared with early recovery in both study groups.

CONCLUSIONS

Coronary occlusion during OPCAB surgery results in increased production of ischemia-related metabolic products. The application of methods such as IPC or volatile anesthesia appears to reduce the metabolic deficit, free-radical production, and physiologic changes.