Comparison of Cardiac Preconditioning effects of Isoflurane and Sevoflurane in Coronary Artery Bypass Graft Surgeries done on Cardio Pulmonary Bypass

Sathish Kumar, D (2007) Comparison of Cardiac Preconditioning effects of Isoflurane and Sevoflurane in Coronary Artery Bypass Graft Surgeries done on Cardio Pulmonary Bypass. Masters thesis, Christian Medical College, Vellore.


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INTRODUCTION: Ischemic heart disease is one of the major causes of morbidity and mortality all over the world. Various medical and surgical strategies have been evolved to reduce the mortality from acute MI which includes the use of thrombolytic agents, β blockers, ACE inhibitors, antioxidants, PTCA and Coronary artery bypass surgery (CABG). CABG is still considered the gold standard. Many reports have shown that upto 90% of patients undergoing CABG surgery experience a fall in ejection fraction and cardiac index during the immediate post-operative period. This has been attributed to various factors of which ischemia associated with aortic cross clamping and inadequate myocardial protection during surgery seem to be the main causes. One intervention for myocardial preservation which has received universal acceptance and generated a lot of excitement is the phenomenon of “Myocardial Ischemic preconditioning”. Myocardial preconditioning can be achieved by various methods. Recently several studies have reported cardioprotective effects of volatile agents in coronary surgery patients. This has been achieved with different volatile agents like halothane, enflurane, isoflurane and sevoflurane. Isoflurane and recently sevoflurane have been shown to be better preconditioning agents in some studies. My study is an attempt to determine if administration of either isoflurane or sevoflurane in patients undergoing CABG surgery will improve postoperative myocardial contractility and function and also to determine which of these volatile agents would offer more cardiac protection when used as preconditioning and post conditioning agents throughout surgery including the cardio pulmonary bypass period. AIM OF THE STUDY: To compare the cardioprotective properties of Isoflurane and Sevoflurane when used before, during and after Cardiopulmonary bypass (CPB) to improve postoperative outcome in coronary artery bypass graft surgeries by analyzing: A) Hemodynamic parameters such as Invasive arterial blood pressure, Electrocardiogram, Cardiac index, Systemic vascular resistance and Central Venous pressure. B) Postoperative measurements of Creatinine kinase-MB to compare degree of ischemia. C) Markers of Oxidative and nitrosative stress such as protein carbonyl content, malondialdehyde, protein thiols, total thiols and nitrates. MATERIALS AND METHODS: This randomized, blinded, clinical controlled trial was approved by the Research and ethics committee of our institution. Twenty patients scheduled to undergo elective CABG surgery on cardio pulmonary bypass pump for coronary artery disease were included in this study. The surgeon, the pump technician and biochemist was blinded to the drug, the anaesthetist involved with the surgery could not be blinded to the anaesthetic agent. EXCLUSION CRITERIA: a) Off pump CABG, b) Previous coronary (or) valvular heart surgery, c) Preoperative hemodynamic instability requiring medical or mechanical support, d) Severe hepatic disease (ALT or AST >150U/L), e) Renal insufficiency (creatinine>1.5mg/dl.), f) COPD (FEV1<50% of predicted or <0.8L), g) H/o neurological disturbances. Randomization: Patients were randomly allocated into group A (isoflurane group) and group B (sevoflurane group) using computer generated random numbers. This randomization was done before the study began to assure equal allocation to the Group A and Group B. The randomization envelope was opened by an anesthetist, and accordingly that particular anesthetic agent either isoflurane or sevoflurane was used throughout the procedure. Pre-op evaluation: Following a thorough preoperative check up the procedure was explained to the patient. After obtaining informed consent, patients are randomly allocated to one of the two groups. Antiplatelet therapies were stopped 1wk before the operation and replaced by Heparin. ACE inhibitors are stopped one day prior to the surgery as a routine in our institution. Oral anti diabetic drugs were continued upto the night prior to surgery. Beta blockers and nitrates were continued upto the morning of surgery. Patients were premedicated with benzodiazepines and opioids one hour prior to the procedure. Statistical Analysis: Patient characteristics, hemodynamics parameters and biochemical markers were compared using non parametric Mann-Whitney, Wilcoxon signed rank test, paired t test and Fisher’s exact test wherever appropriate. RESULTS: 20 patients scheduled for coronary artery bypass grafting on CPB were enrolled in the study. Two patients were not included in the analysis; one surgery was done off pump, hence excluded from the analysis. In the other patient, due to damage of coronary sinus during surgical manipulation there were problems of separation from CPB pump, the patient required an Intra aortic balloon pump (IABP) as well as a pacemaker for weaning from bypass. Table 1 shows the demographic data of patients in both groups. There were no significant differences in age, weight, height and gender of the patients between the two groups. As can be seen from this table, there was only one female included in the study. Table 2 describes the premorbidity status of all patients. There was no statistically significant differences between the two groups .One patient in Group 2 had aortic stenosis and another had four vessel disease. CONCLUSIONS: 1. Our study strongly indicates definite cardiac preconditioning effects with both the volatile agents isoflurane and sevoflurane in clinically relevant concentrations when administered throughout CABG surgery. 2. The evidence of oxidative stress with CABG surgery was shown by decreasing levels of biochemical markers. The preconditioning effects with these agents were evident from the ease of separation from CPB bypass and outcome of surgery in the immediate post-operative period as shown by the clinical and biochemical markers at different time intervals. 3) Among the two agents, isoflurane seems to provide better protection. during the pre-bypass period and early reperfusion, while sevoflurane provides protection during early reperfusion as well as immediate postbypass period when the oxidative stress is much greater. Taking into account patient variability and the different mechanisms involved with different anaesthetic agents, larger adequately powered trials with defined outcomes need to be done to fully assess a possible beneficial effect of one volatile anaesthetic agent over the other and arrive at definite conclusions.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Cardiac Preconditioning effects ; Isoflurane ; Sevoflurane ; Coronary Artery Bypass Graft Surgeries ; Cardio Pulmonary Bypass ; Comparison Study.
Subjects: MEDICAL > Anaesthesiology
Depositing User: Subramani R
Date Deposited: 30 Apr 2018 02:53
Last Modified: 30 Apr 2018 02:53

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