Hemodynamic effects of intravenous phentolamine in low output cardiac failu;e. Dose-response relationships

Nineteen patients with chronic low output cardiac failure were studied before, during and after infusion of phentolamine in doses of 10, 20, 30 and 40 microgram/kg/min. Significant reduction of left- and right-sided pressures and increases in cardiac index and heart rate (HR) were present within 15 minutes of starting phentolamine at the 10 microgram/kg/min dose. Minimal additional effect was observed at 30 minutes. Increased dose from 10 to 20 mu/kg/min resulted in small but significant (P less than 0.05) additional reduction in pressures and increases in HR. No additional significant changes occurred at doses of 30 or 40 microgram/kg/min. Significant hemodynamic changes persisted for at least an hour (53 +/- 3 min) after the phentolamine infusion was discontinued. Near maximal ;emodynamic effects occur within 15 minutes of starting phentolamine infusion and can be achieved at doses of 10 to 20 microgram/kg/min. Increased HR during phentolamine infusion may limit its usefulness in patients with ischemic heart disease.