The Effect of Esmolol Combined with Nitroglycerin on Cardiac Hemodynamics and Myocardial Oxygen Balance during Cross-Clamping of Thoracic Aorta in Induced Ischemic Canene Heart

Kwoen, Ou Kyoung; Choi, Jong Ho; Kim, Young Jin

Abstract

The purpose of this study is to investigate the protective role of esmolol during cross-clamping of descending thoracic aorta on the ischemic myocardium induced by the ligation of the left anterior descending coronary artery(LAD) in dogs. LAD was ligated for 15 min followed by reperfusion. Nitroglycerin with or without esmolol were continuously infused throughout procedure and the thoracic aorta was cross-clamped for 45 mins. Eighteen dogs were divided into three groups; group C-no drug administerd, group N-nitroglycerin(5 ug/kg/min), and group NE-nitroglycerin(5 ug/kg/min) with esmolol(0.5 mg/kg as loading dose following 50 ug/kg/min as maintenance dose). Heart rate(HR), mean arterial pressure(MAP), stroke volume(SV), cardiac index(CI), left ventricular stroke work index(LVSWI), pulmonary capillary wedge pressure(PCWP), triple index(TI), mixed venous oxygen tension of great cardiac vein(PgvO2), Ca-vDO2(carotid arterial oxygen content-great cardiac vein oxygen content) and lactate were measured three times in each group before ligation of LAD(stage 1), 15 minutes after LAD ligation(stage 2) and 45 minutes after cross-clamping of descending thoracic aorta(stage 3). The results were as follows: 1) MAP of group NE at stage 3 was significantly high compared with group C but low compared with group N (P<0.05). 2) SV of group NE at stage 3 was significantly high compared with group C and group N. A significant change was observed between group C and group N(P<0.05). 3) CI, LVSWI, PgvO2 of group NE at stage 3 were significantly high compared with group C but not significantly high compared with group N(P<0.05). 4) HR, PCWP, Lactate level of group NE at stage 3 were significantly low compared with group C and group N. A significant change was also observed between group C and group N(P<0.05). 5) TI, Ca vDO2 of group NE at stage 3 were significantly low compared with group C and group N, but no significant change was observed between group C and group N(P<0.05). These results suggest that esmolol could protect ischemic myocardium from progressive damage via reduction of myocardial oxygen consumption without decrease of cardiac output and left ventricular stroke work index.