Effects of catecholamines on myocardial viability in early reperfusion following hypothermic global ischemia in dogs--comparison between epinephrine and dobutamine.

Attempts were made to define the effects of epinephrine and dobutamine on the myocardium during early reperfusion for 60 minutes following hypothermic global ischemia at a myocardial temperature of 28 degrees C for 60 minutes under cardiopulmonary bypass. Ischemia was induced by cross-clamping the dog aorta. Epinephrine (0.1 microgram/kg/min) and dobutamine (5 micrograms/kg/min) were given throughout the reperfusion period by intravenous drip infusion, a control group was treated with saline infusion. Comparison of hemodynamic parameters was made before cardiopulmonary bypass, and at 30 and 60 minutes of reperfusion. Epinephrine and dobutamine significantly increased stroke volume index, left ventricular stroke work index and tissue calcium content compared with saline, however, myocardial water content was only slightly higher in the group given saline, compared with the other two groups. Myocardial mitochondrial membranes and cristae were slightly damaged and creatine phosphate content was reduced. Ultrastructural integrity was related to myocardial tissue calcium content, with a significant negative correlation. These results suggest that epinephrine (0.1 microgram/kg/min) will improve stroke volume index and left ventricular stroke work index, as does dobutamine (5 micrograms/kg/min), however, both agents had a minimal effect on reducing myocardial morphological and biochemical integrity, although catecholamines have detrimental effects on the myocardium in early reperfusion following ischemia.