Comparison of the renal effects of low to high doses of dopamine and dobutamine in critically ill patients: A single-blind randomized study

Objective: The renal effects of dopamine in critically ill patients remain controversial. Low-dose dobutamine has been reported to improve renal funct ion. We compared the effects of various doses of dopamine and dobutamine on renal function in critically ill patients. Design: Prospective, single-blind, randomized study. Setting: University hospital, 19-bed multidisciplinary intensive care unit. Patients: Twelve hemodynamically stable patients with mild nonoliguric rena l impairment. Interventions: Each patient randomly received four different doses of dopam ine and dobutamine (placebo, 3, 7, and 12 mu g/ kg/min). Each infusion last ed for 4 hrs. Cardiac output and systemic hemodynamic variables were measur ed using a pulmonary arterial catheter at the beginning (H0) and the end (H 4) of each infusion. The bladder was emptied at H0 and H4 to determine urin e volume and to collect samples. Measurements and Main Results: The cardiac index increased significantly wi th both dopamine and dobutamine (p <.001). Mean arterial pressure (MAP) inc reased, with the maximum effect of 20% seen with 12-mu g/kg/min dopamine in fusion (p <.01). No change in MAP was seen with dobutamine. Dobutamine infu sions did not change any renal variables. Conversely, all dopamine infusion s significantly increased diuresis, creatinine clearance, and the fractiona l excretion of sodium (p <.01). Creatinine clearance increased from 61 +/- 16.9 (SD) mL/min to a maximum of 85.7 +/- 30 mL/min at the 7-mu g/kg/min do se; fractional excretion of sodium increased from 0.26% +/- 0.28% to a maxi mum of 0.62% a 0.51% at the 12-mu g/kg/min dose (p <.01). During dopamine i nfusions, there was a significant relationship between MAP and creatinine c learance (p =.018). Conclusions: At all doses studied, 4-hr infusions of dopamine significantly increased creatinine clearance, diuresis, and the fractional excretion of sodium in stable critically ill patients. Conversely, dobutamine did not mo dify these variables. Although the level of MAP might partially contribute to the improvement in renal variables, it is more likely that the activatio n of renal dopamine receptors played a prominent role.