The Journal of Thoracic and Cardiovascular Surgery, Vol 87, 452-465, Copyright © 1984 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Comparison of catecholamine effects on canine myocardial metabolism and regional blood flow during and after cardiopulmonary bypass
HB Ward, S Einzig, T Wang, RW Bianco and JE Foker
The acute metabolic and hemodynamic effects of dopamine, dobutamine (both
at 10 micrograms . kg-1 . min), and isoproterenol (at 0.05 or 0.1
micrograms . kg-1. min) were determined in dogs following 20 minutes of
normothermic global myocardial ischemia. The catecholamines were started 10
minutes before cardiopulmonary bypass (CPB) was discontinued and were
continued for 1 hour after bypass. Regional myocardial and systemic blood
flow distribution was measured by means of the radioactive microsphere
technique. On bypass all catecholamines sharply increased heart rate,
myocardial oxygen consumption, and left ventricular blood flow (p less than
0.01). Because the hearts were unloaded, these data suggest that velocity
of contraction is an important component of myocardial oxygen consumption.
Although these drugs did not lower myocardial adenosine triphosphate (ATP)
and creatine phosphate (CP) levels, the significant rise in oxygen
consumption suggested that inotropic treatment on bypass may not be
beneficial. Furthermore, renal blood flow was diminished in dobutamine-
treated dogs (p less than 0.01) and tended to decrease with isoproterenol
infusion. No change was seen with dopamine infusion. After bypass,
dobutamine treatment increased cardiac output (p less than 0.01) and stroke
volume (p = 0.017) with no change in heart rate, myocardial oxygen
consumption, high-energy phosphate levels, and total or transmural
distribution of left ventricular blood flow. Dopamine infusion did not
change cardiac output but did increase oxygen consumption (p less than
0.01). Isoproterenol showed a slight inotropic effect, but frequent
ventricular arrhythmias were present during weaning from bypass. In all
treatment groups, blood flow in the other systemic beds (cerebral,
gastrointestinal, and renal) was similar to that in control dogs. These
data suggest that dobutamine is the most efficient of the drugs tested for
support of the heart following global myocardial ischemia but, when given
during bypass, it appears to decrease renal blood flow.