Negative inotropic action of propofol is enhanced in the acute ischemic myocardium of dogs

Purpose We investigated the effects of propofol on contractility and oxygen balance in acute ischemic myocardium and compared them with those of normal myocardium using a coronary microembolization model in dogs.Methods In open-chest dogs, the left anterior descending coronary artery (LAD) was perfused through an extracorporeal bypass from the carotid artery. Regional myocardial contractility and myocardial oxygen balance were evaluated along with segment shortening (%SS), regional myocardial oxygen consumption (MVO₂), and lactate extraction ratio (LER) of the area perfused by the LAD. Acute ischemia was produced by repeated injection of microspheres into the LAD-perfused area until %SS decreased by 50% of baseline.Results In normal myocardium, intracoronary infusion of propofol at doses of 1.2 and 2.4mg·kg^–1·h^–1 caused slight decreases in %SS to 83% ± 8% and 80% ± 10%, respectively. In ischemic myocardium, propofol caused greater decreases in %SS (59% ± 18% and 35% ± 20%, respectively). The changes in MVO₂ after propofol infusion generally paralleled the changes in %SS, but LER was not changed in either ischemic or normal myocardium.Conclusion Propofol causes a greater decrease in the contractility of acute ischemic myocardium as compared with normal myocardium in which myocardial oxygen imbalance is not involved as a mechanism.