BACKGROUND: Preoperative beta-adrenergic receptor (beta-AR) antagonist administration is known to improve ventricular function by decreasing the myocardial oxygen demand in coronary artery obstructive disease (CAOD). This study evaluated the effect of preoperative propranolol on response to beta-AR agonist, dobutamine in patients undergoing off-pump coronary artery bypass graft surgery (CABG). METHODS: Twenty six patients undergoing off-pump CABG, and treated with propranolol preoperatively, were enrolled in this study. After anesthesia, the infusion of dobutamine was started at 2microgram/kg/min (D2) for 5 min and then increased to 4microgram/kg/min (D4) and 8microgram/kg/min (D8) in succession. The same protocol was performed twice before and after coronary artery anastomosis (pre-graft and post-graft). Hemodynamic variables were measured just before the infusion of dobutamine (D0, baseline) and after each dobutamine infusion at D2, D4 and D8. RESULTS: No significant change was observed in the cardiac index (CI) during the pre-graft period, but CI increased significantly at D4 and D8 compared with D0 during the post-graft period. Mean arterial pressure (MAP), mean pulmonary artery pressure (MPAP) and systemic vascular resistance index (SVRI) increased at D2, D4 and D8 and heart rate (HR) decreased at D2 and D4 during the pre-graft period. MAP and SVRI did not change and HR and CI increased at D4 and D8 during the post-graft period. The % change of CI from D0 significantly increased at D4 and D8 during the post-graft period than during the pre-graft period but not at D2. MAP, SVRI and MPAP after dobutamine infusion significantly increased during the pre-graft period than during the post-graft period. HR showed a reversed trend. CONCLUSIONS: Dobutamine infusion did not exert any known positive inotropic effect, besides increased MAP, MPAP and SVRI, in patients treated with propranolol preoperatively undergoing off-pump CABG during the pre-graft period. Meanwhile, dobutamine exerted slight inotropic effects during the post-graft period. Cautious use of dobutamine during the pre-graft period is needed in patients treated with propranolol preoperatively.