Nitroprusside infusion in experimental acute myocardial infarction with systemic hypertension: effects on systemic hemodynamics and regional myocardial blood flows.
The effects of graded doses of nitroprusside on regional myocardial blood flow were studied in awake, acutely hypertensive dogs with acute myocardial infarction. Acute systemic hypertension was produced by infusing a mixture of norepinephrine and epinephrine for 80 minutes after coronary artery occlusion. The increase in aortic pressure produced by catecholamine infusion was accompanied by increases in heart rate, left ventricular (LV) end-diastolic pressure, first derivative of LV pressure (dP/dt), dP/dt at an LV developed pressure of 50 mm Hg (dP/dt/P) and pressure-rate product, but total peripheral vascular resistance did not change significantly. Two graded doses of nitroprusside were then infused, each for 25 minutes, beginning 30 minutes after the onset of coronary artery occlusion. The smaller dose of nitroprusside returned aortic pressure to control levels and significantly reduced total peripheral vascular resistance and LV end-diastolic pressure, but did not affect cardiac output, heart rate, LV dP/dt, dP/dt/P and pressure-rate product. Regional blood flow increased to both the ischemic and normal myocardium. The larger dose of nitroprusside further reduced aortic pressure and total peripheral vascular resistance and LV end-diastolic pressure and significantly increased heart rate and cardiac output. However, LV dP/dt, dP/dt/P and pressure-rate product remained unchanged. Regional blood flow to normal myocardium increased, but the increase in ischemic endocardial blood flow produced by the smaller dose of nitroprusside was no longer significant when the larger dose was administered. These changes were not produced by administration of normal saline solution.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects*; D004285:Dogs; D004837:Epinephrine; D005292:Ferricyanides / Q000627:therapeutic use*; D006439:Hemodynamics / Q000187:drug effects*; D006973:Hypertension / Q000139:chemically induced / Q000188:drug therapy*; D007263:Infusions, Parenteral; D009203:Myocardial Infarction / Q000188:drug therapy*; D009599:Nitroprusside / Q000627:therapeutic use*; D009638:Norepinephrine
D005292:Ferricyanides; D009599:Nitroprusside; D009638:Norepinephrine; D004837:Epinephrine