| Background Researches have proved that thoracic epidural anesthesia has certain protective effects on ischemic myocardium to the patients with ischemic heart diseases. Some cases of TEA combined with inhalation anesthetic or intravenous anesthetic have been reported. There are more concern about aggravation on hemodynamics of the combined anesthesia for the patients with ischemic heart diseases. Which anesthesia is well suited for the patients with ischemic heart diseases need surgical operations? Application of TEA combined with propofol to the patients has been reported, but there is no related report that effects on hemodynamics , cardiac function and ischemic myocardium.Objective To investigate the protective effects and mechanism of thoracic epidural anesthesia combined with propofol on myocardial infarction by observing the hemodynamics, left cardiac function , myocyteapoptosis and myocardial injury.Methods Seventy-two rabbits were anesthetized with 20% urethane (1.0g-kg-1, i.v.).Following tracheal intubation, epidural catheter was put into at T6~7 with the anterior end of the catheter reaching at T2~3, femoral artery was cannulated for determination of MAP. Cardiac catheter was placed via common carotid artery. After the epidural anesthesia was made sure to be effective, the anterior descending branches of left coronary artery (LAD) were ligated and myocardial infarction was confirmed by ST elevation>0.1mv.The rabbits were randomly divided into four groups(n=18):group C was control; in group T, 1%lidocaine 2~3mg-kg-1 was injected to epidural space; in group P, propofol was infused at a rate of 20mg-kg-1-h-1 for 30min;in group T+P, TEA combined with propofol. Hemodynamics and left cardiac function were monitored pre- and 30min post-ligation. Blood samples were collected before ligation, 4h and 8h after ligation to measure the blood serum levels of SOD, MDA and myocardial troponin I. TUNEL was applied to monitor the myocyte apoptosis, p53 and Bcl-2 protein expression were assessed by LSAB. The extent of infarcted area was determind by TTC staining.Results1. TEA combined with propofol significantly repressed the increasing of LVEDP and the decreasing of LVSP, dp/dtmax caused by LADligation compared with TEA, whereas propofol had no effect.2. In infracted area, TEA combined with propofol and propofol significantly inhibited the apoptosis and expression of p53 protein, increased the expression of Bcl-2 protein. The amount of most apoptosis in infracted area was positively correlated to p53 protein expression, and was negatively correlated to Bcl-2 protein expression.3. After ligation, MDA increased and SOD decreased in control group. At 4h after ligation, propofol and TEA combined with propofol induced a decrease of MDA, while TEA combined with propofol induced a increase of SOD from (23.32 6.46) U-ml-1 to (25.13 3.29) U-ml-1 at 8h after ligation.4. After ligation, myocardial troponin I increased in all groups. The level of cTnI significantly decreased in TEA combined with propofol contrast with TEA and there is no significant difference in 4h, 8h after ligation.5. TEA and TEA combined with propofol have a tendency of reducing the size of infarcted area contrast with control while there was no significant difference in 4h, 8h after ligation.ConclusionTEA combined with propofol can significantly protect myocardium from injury of rabbits with experiment myocardial infarction and thisaction is mediated by relieving the reverse effect on hemodynamics and the suppression of apoptosis and the damage of oxidative stress.
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