Background: Myocardial ischemia is a metabolic phenomenon that occurs in patients undergoing open heart surgery like coronary artery bypass grafting (CABG). In myocardial ischemia, secondary myocardial carnitine deficiency has been observed. Objectives: Recording the perioperative hemodynamic changes among patients undergoing coronary artery bypass. Evaluation of the intraoperative cardiac ischemia via biochemical assessment of serum levels of Pyruvate, Lactate, L-carnitine and calculation of lactate/pyruvate ratio preoperative, intraoperative and postoperative. Methods: A prospective case control and clinical observational study was carried out on 17 ischemic heart disease male patients undergoing elective coronary artery bypass grafting who admitted at cardiothoracic surgery department-Faculty of Medicine- Assiut University. This was in addition to 25 apparently healthy age matched males as control group. Serum levels of pyruvate and lactate were estimated using spectrophotometric methods, while serum levels of L-carnitine were estimated using ELISA assay kit. Results: There were significant hemodynamic changes regarding the heart rate, arterial blood pressure and central venous pressure, preoperative versus one hour postoperative (p< 0.001). Also, there were significant lower serum pyruvate levels and higher serum lactate levels and lactate /pyruvate ratio intraoperatively when compared with the control group (p < 0. 01) .A significant lower serum L-carnitine levels intraoperatively when compared with the control group (p < 0. 01) and when compared with the preoperative assay levels (p < 0. 05).There was a negative correlation between intraoperative seum L-carnitine levels versus the clamping time (r= -0.607, p=0.01). Conclusions: The myocardial ischemia in various degrees that developed during the intraoperative phase of coronary bypass operations causes significant changes in the serum levels of pyruvate, lactate, lactate/pyruvate ratio and L-carnitine, which should be non-elevating and decreasing towards the control levels post-operatively to indicate good myocardial function with its return to aerobic metabolism with lower morbidity and mortality. Preoperative administration of L-carnitine in such group of patients is recommended as a protector against the intraopeartive cardiac ischemia.