Quantitative assessment of the effects of 'inodilators' on the myocardium in patients without primary cardiac insufficiency after coronary surgery: Part I--Amrinone.

The positive inotropic and peripheral vasodilating effect of amrinone has been measured in 20 patients without manifest cardiac insufficiency during the early (8-18 h postoperative) and late (18-48 h postoperative) recovery phase after coronary surgery. On conclusion of the surgical intervention first the aortocoronary bypass flow was compared during dobutamine and amrinone administration. It increased by 88% with amrinone and by 19% with dobutamine. Then a needle force probe was implanted in the myocardium. Directly measured local myocardial force increased not significantly by 3.5% after the first and by 5.1% after the second bolus injection of 2 mg/kg amrinone. The rate of myocardial contraction increased by 18.7% and 12%. The rate of relaxation decreased by 5.3% after the first and increased by 15% after the second injection. Mean pulmonary arterial pressure fell from 18.5 to 15.5 mmHg and from 19.7 to 17 mmHg. Cardiac output increased by 23% after the first and by 20% after the second injection. Heart rate rose from 88 to 99 bpm and from 86 to 94 bpm. Total peripheral resistance fell from 1,035 to 706 dyn*s*cm-5 and from 1,036 to 819 dyn*s*cm-5. The systolic arterial pressure fell from 132 to 116 mmHg after the first injection and did not change after the second injection. Amrinone was found to be a powerful peripheral vasodilator with a mild positive inotropic action. The variations in the effects between the early and late recovery phases mainly reflect a progressive haemodynamic stabilization with a decreasing tendency toward hypotensive disregulation. Careful consideration has to be paid to a properly balanced filling of the vascular system before administering amrinone.