Combined Epidural Analgesia and General Anesthesia Induce Ischemia Distal to a Severe Coronary Artery Stenosis in Swine

Abstract

Epidural analgesia combined with general anesthesia may improve cardiac function and reduce the work of the heart by decreasing the rate pressure product. However, the effect of this combined technique has not been studied in the presence of severe coronary artery stenosis. Therefore, we investigated epidural analgesia combined with general anesthesia in a swine model with a tight coronary artery stenosis. The coronary stenosis placed around the proximal left anterior descending coronary artery (LAD) allowed normal blood flow at rest but only minimum hyperemia in response to the coronary dilator, adenosine. To accomplish an extensive sympathetic block, we injected enough bupivacaine 0.5% into the lumbar epidural space to reach at least the level of the first thoracic vertebra (T1). Epidural catheter position was verified by fluoroscopy. Hemodynamic changes, LAD myocardial blood flow, and regional myocardial wall thickening were measured. Fifteen minutes after the injection of bupivacaine, systolic and diastolic blood pressure decreased 24.1% and 26%, respectively, cardiac output decreased 25.6%, and mean coronary blood flow decreased 42%, compared to the saline control. Myocardial wall thickening in the LAD bed decreased 31%, although it remained unchanged in the normal myocardium. Epidural bupivacaine added to general anesthesia resulted in moderate hypotension. Distal to the coronary stenosis was a moderate decrease in regional myocardial function and a severe reduction in blood flow.