RENAL DOSE DOPAMINE DOES NOT ALTER THE RESPONSE TO BETA-ADRENERGIC STIMULATION BY ISOPROTERENOL IN HEALTHY-HUMAN VOLUNTEERS

Objectives: To determine if renal dose dopamine (3 mu g/kg/min) alters the heart rate (HR) by itself, or if a dopamine infusion alters the H R response to bolus doses of the beta-adrenergic agonist isoproterenol in healthy human subjects. Design: Prospective study. Setting: Clinic al laboratory of a university-affiliated academic medical center. Subj ects: A total of 15 health nonpregnant women and men aged 21 to 44 yea rs. Interventions: Subjects were monitored continuously with bedside E CG, pulse oximetry, and ambulatory ECG recording to measure the maxima l HR response to separate injections of 10, 20, and 30 ng/kg of isopro terenol, given before, during, and after the infusion of 3 mu g/kg/min of dopamine. Measurements and main results: Dopamine in the absence o f isoproterenol did not alter baseline HR significantly (62.7+/-2.2 be ats/min without dopamine; 65.4+/-2.2 with dopamine; p=0.15). All three doses of isoproterenol increased HR significantly above baseline, bot h in the presence and absence of dopamine (p<0.001). Dopamine infusion resulted in a higher HR following isoproterenol only for the 20-ng/kg dose. The incremental increases in HR, defined as the difference betw een peak HR following isoproterenol and baseline HR, were not increase d during dopamine infusion for an, of the doses of isoproterenol. Naus ea was reported by 5 of the 15 subjects during the dopamine infusion. Conclusions: In healthy human subjects, infusion of 3 mu g/kg/min of d opamine does not significantly increase the HR when combined with beta -adrenergic stimulation using isoproterenol, suggesting neither an add itive nor antagonistic interaction between the two drugs. While our st udy did not demonstrate an increase in HR in healthy subjects, the ris k of increasing the chronotropic response to beta-adrenergic inotropic medications with ''renal dose'' dopamine in critically ill patients n eeds to be investigated. The frequency of nausea during dopamine infus ion also may influence consideration of using dopamine to augment spla nchnic blood flow and renal function in conscious patients.