BACKGROUND: Norepinephrine infusion has been reported to be associated with adverse events in ischemic heart disease due to elevation of afterload and cardiac oxygen consumption. During coronary artery bypass graft, we observed changes of hemodynamic and laboratory parameters in low dose norepinephrine infusion. Also, we investigated effects of norepinephrine on cardiac oxygen metabolism by calculating oxygen consumption and lactate extraction ratio.

METHODS: Fifteen patients, ASA PS class IV-V, scheduled for elective coronary artery bypass graft were enrolled in this study. All of the operations were performed under general anesthesia. During harvesting of graft vessels, norepinephrine was infused at the rate of 0.02µgram/kg/min, and then at the rate of 0.05µgram/kg/min. We measured various hemodynamic and laboratory parameters in three periods (baseline, NE 0.02µgram/kg/min, NE 0.05µgram/kg/min). Also we calculated oxygen consumption and lactate extraction ratio of myocardium.

RESULTS: In the baseline period(no norepinephrine infusion), oxygen consumption (VO₂) is 159.2 ± 78.6 ml/min, lactate extraction ratio (LER) is 33.1 ± 13.0%. After norepinephrine infusion at the rate of 0.02µgram/kg/min, VO₂ is 157.6 ± 55.7 ml/min, LER is 29.9 ± 10.7%. After norepinephrine infusion at the rate of 0.05µgram/kg/min, VO₂ is 212.5 ± 134.5 ml/min, LER is 27.9 ± 13.4%. Although VO₂ and LER are changed in relation to the rate of norepinephrine infusion, there was no statistical significance.

CONCLUSIONS: In conclusion, infusion of low dose norepinephrine during coronary artery bypass graft did not produce significant differences in myocardial oxygen consumption and lactate extraction ratio associated with myocardial oxygen balance.