Acute effects of amrinone on regional myocardial and systemic blood flow distribution in the dog.

The effect of bolus intravenous injections of amrinone (1-2 mg/kg) on abdominal organ, central nervous system, and myocardial blood flow distribution was examined in 15 anesthetized dogs. Blood flows were measured during control conditions and 5 and 60 min following drug administration using left atrial injection of 15-micrometers radionuclide-labeled spheres. Analysis of variance revealed that blood flow changes were similar in dogs receiving either drug dose (P greater than 0.10). Five minutes following injection, blood flow was increased (all P less than 0.05) in the renal cortex (+20.4%), spleen (+40.4%), and liver (+47.1%); flow was unchanged in other abdominal organs (pancreas, gallbladder, small and large intestine, and fundic and antral gastric mucosa) and the central nervous system (cervical spinal cord, pons, medulla, dorsal thalamus, cerebellum, caudate nucleus, and cerebral cortical gray and white matter); and flow was reduced in the triceps muscle (-23.7%). At this time, left ventricular flow was increased (+25.0%) and the left ventricular subendocardial/subepicardial (Endo/Epi) flow ratio was reduced (1.09 +/- 0.02 (SE) vs. 0.90 +/- 0.02, P less than 0.001). Sixty minutes following injection, renal and hepatic flows had returned to control values while splenic flow remained increased (+61.6%); intestinal, gastric mucosal, gallbladder, and triceps flows were reduced by values ranging from 26.7 to 38.9% and central nervous system perfusion was reduced by values ranging from 11.8 to 19.4% in all regions except the caudate nucleus. Although left ventricular flow had returned to control values, the Endo/Epi ratio (1.02 +/- 0.02) remained minimally reduced at this time (P less than 0.001). These results suggest that vascular responsiveness to intravenous amrinone is not uniform in different circulatory beds and that relative subendocardial under-perfusion of the left ventricular myocardium occurs following bolus intravenous amrinone injections in the dog.