Effect of dopamine on hemodynamics and myocardial metabolism in shock following acute myocardial infarction in man.

Eight patients in shock associated with acute myocardial infarctions were treated with dopamine. We titrated the dopamine dose to increase mean arterial pressure to 65-70 mm Hg and urine output to greater than 40 ml/hr. Increase of heart rate to 120-125 beats/min and occurrence of potentially dangerous arrhythmias were limiting end-points. Dopamine administration averaged 17.2 microgram/kg/min. Heart rate increased from 95 to 118 beats/min (P less than 0.001), and mean arterial pressure rose from 60 to 65 mm Hg (P less than 0.05). Dopamine increased myocardial contractility as indicated by increase in cardiac index and systolic ejection rate, with only moderate decrease in systemic vascular resistance. Pulmonary wedge pressure and right atrial pressure decreased from 23 to 18 mm Hg (P less than 0.05) and from 10 to 8 mm Hg (P less than 0.001) respectively. Improvement in hemodynamic status by dopamine was associated with deterioration of myocardial metabolism. Myocardial oxygen extraction ratios and arterial-coronary sinus oxygen differences increased from 73 to 76% (P less than 0.05) and from 13.02 to 14.19 ml/100 ml (P less than 0.02) respectively. Myocardial lactate production increased from -8 to -15% (P = 0.05). We conclude that dopamine improved cardiac performance at the expense of myocardial oxygenation and that dopamine is potentially harmful to acutely ischemic myocardium.