[Effects on hemodynamics and myocardial metabolism of nicardipine and nitroglycerin during aortic cross clamp in dogs with experimentally produced coronary stenosis].

We investigated the effects of hemodynamics and myocardial metabolism of nicardipine (NIC) and nitroglycerin (NTG) in experimentally coronary constricted dogs. Coronary constriction was produced by reducing 50% of the left anterior descending coronary blood flow. After stabilization of hemodynamics, we cross-clamped the descending aorta and administered nicardipine (10 micrograms.kg-1.min-1) or nitroglycerin (10 micrograms.kg-1.min-1). The drugs were infused for 15 minutes and were discontinued just before the clamp on the aorta was released. In NIC group, the cardiac output (CO) increased 32% and the heart rate (HR) decreased 17% significantly, compared with pre-clamping values. The myocardial blood flow (MBF) in ischemic area measured by hydrogen clearance method was maintained. The value of the myocardial oxygen extraction ratio (MO2EX) decreased significantly for 24.3% compared with the pre-clamping value of 41.4%. On the other hand, in NTG group, CO, HR, and MO2EX were unchanged, but MBF in ischemic area was well maintained. The results of these experimentally coronary constricted dogs suggest that both NIC and NTG maintain the cardiac function during the aortic cross-clamping, but regarding the improvement of the myocardial metabolism, NIC appears to be the better choice for blood pressure control.