Renal effects of dopamine in vascular surgical patients

Abstract

Low-dose dopamine (DA) is often used in surgical patients to induce diuresis when appropriate volume replacement is unsuccessful. Despite wide application, there are little objective data supporting any beneficial effects on renal hemodynamics in this patient population. To better define the response to dopamine in the clinical setting, we studied the renal effects of low-dose DA in 13 patients having vascular surgery. Glomerular filtration rate (GFR) and renal blood flow (RBF) were measured by inulin and p-maminohippurate clearance, respectively. Group I (n = 8) included patients in stable condition after operation who were administered intravenous DA, 0.5 μg/kg/min, for 2 hours. RBF significantly increased from 579 ± 85 to 726 ± 114 ml/min/1.73 m2 (p< 0.05). Increases were also observed in GFR (95.0 ± 10.9 to 107 ± 15.7 ml/min/1.73 m2), sodium excretion (164 ± 35 to 239 ± 53 μEq/min), and osmolar excretion (709 ± 78 to 866 ± 93 μOsm/min). There were no changes in urine output (2.17 ± 0.36 to 2.49 ± 0.43 ml/min). Group II (n = 5) consisted of patients having abdominal aortic surgery who were treated with DA, 2.0 μg/kg/min, before and after surgery. Increases in RBF were seen in both the preoperative period (414 ± 59 to 659 ± 96 ml/min/1.73 m2, p < 0.01) and postoperative period (439 ± 60 to 623 ± 94 ml/min/1.73 m2, p < 0.01). There were no significant differences in the preoperative and postoperative response to DA with respect to urine output, GFR, RBF, sodium excretion, potassium excretion, or osmolar excretion. We conclude that DA in very low doses (0.5 μg/kg/min) consistently increases RBF without causing a significant diuresis. The renal effects of 2.0 μg/kg/min DA are similar in the preoperative and postoperative period of aortic reconstructive surgery. Most importantly, DA-induced increases in RBF and GFR cannot be reliably predicted from the diuretic response.