Regional Vasodilating Properties of Isoflurane in Stunned Swine Myocardium

Abstract

Studies about the coronary vasodilating properties of isoflurane indicate that this drug induces coronary vasodilation. No work has examined isoflurane-induced vasodilation in known stunned myocardium. This study was conducted to determine isoflurane's coronary vasodilation potency in stunned myocardium and to compare the results obtained with normal myocardium. We determined the vasodilating properties of isoflurane in regionally perfused swine myocardium. Six domestic swine were anesthetized with pentobarbital and fentanyl. The left anterior descending artery (LAD) was cannulated and perfused with blood drawn from the carotid artery and passed thorough a membrane oxygenator. LAD arterial flow was controlled by a calibrated roller pump with continuous digital readout, and LAD arterial pressure was measured directly. The anterior interventricular vein was cannulated and dimension crystals placed in the LAD-perfused myocardium. Myocardial stunning was induced by reduction of coronary blood flow (CBF) to 30% of control flow for 20 minutes. One hour after reperfusion, the vasodilatory response to 0%, 1%, and 2% isoflurane administered via the membrane oxygenator was determined and compared to maximum vasodilatation produced by regional intracoronary administration of adenosine. Systemic blood pressure and heart rate remained constant throughout the experiment. At 2% isoflurane, systolic shortening and regional myocardial oxygen consumption decreased 53% and 17%, respectively. The same concentration increased CBF by 33% and reduced coronary vascular resistance (CVR) by 25%. One percent isoflurane affected neither CBF nor CVR. Regional coronary administration of adenosine produced much greater changes in CBF (+509) and CVR (-89.5%).(ABSTRACT TRUNCATED AT 250 WORDS)