The Effects of Ketamine-Xylazine Pentobarbital Halothane and Soflurane Anesthesia on the Reduction of Infarct Size with Preconditioning
This investigation sought to determine whether anesthesia had an effect on myocardial area at risk and infarct size during experimental myocardial preconditioning. Four anesthetic regimens, ketamine plus xylazine, pentobarbital, halothane, and isoflurane, were studied in both non-preconditioned and preconditioned rabbits. Systemic hemodynamics were monitored throughout each experiment. A branch of the left main coronary artery was occluded for 30-min followed by 2-h reperfusion to produce infarction. For preconditioning, the above phases were preceded by 5-min of brief coronary artery occlusion and l0-min of recovery. Normal tissue, area at risk, and infarct sizes were determined by planimetry analysis. Systemic hemodynamics were not found to be significantly different from control in most cases. When compared to baseline values, left-ventricular end-diastolic pressure was significantly higher at 28-min of occlusion in all groups except non-preconditioned, pentobarbital anesthetized rabbits. Mean arterial pressure was significantly smaller than initial pressures at l20-min of reperfusion in preconditioned rabbits anesthetized with both halothane (p=O.0005) and isoflurane (p=O.006). A significant reduction from baseline L V+dP/dtmax was observed at l20-min of reperfusion with halothane anesthesia and preconditioning, and at 28-min occlusion, 30-min reperfusion, and l20-min reperfusion in preconditioned rabbits anesthetized with isoflurane (p<O.02). Preconditioning with both ketamine-xylazine and pentobarbital anesthesia was found to reduce infarct size significantly more than with either halothane or isoflurane anesthesia. However, nonpreconditioning with halothane and isoflurane anesthesia reduced infarct size greater than with ketamine-xylazine or pentobarbital. Halothane and isoflurane anesthesia were seen to reduce infarct size regardless of preconditioning. This is thought to occur because of a reduction in calcium content, and a corresponding decrease in contractility. Ketamine-xylazine and pentobarbital, on the other hand, were seen to enhance the effect of preconditioning on infarct size.