SERUM ALDOSTERONE CONCENTRATIONS AND URINE OUTPUT IN OLIGURIC INTENSIVE-CARE UNIT PATIENTS RECEIVING LOW-DOSE DOPAMINE

OBJECTIVE: To determine whether the diuretic and natriuretic effects of low-dose dopamine (2.5 μg/kg/min) are associated with changes in serum aldosterone concentration. DESIGN: Prospective clinical study. SETTING: Surgical intensive care unit (SICU) of a university hospital. PARTICIPANTS: Oliguric (urine output <0.5 mL/kg/h) SICU patients. All patients were resuscitated to pulmonary artery occlusion pressure >10 mm Hg, mean arterial pressure >65 mm Hg, and cardiac index >2.5 L/min/m2. Patients with a serum creatinine concentration >176.8 μmol/L (2.0 mg/dL), those who received diuretics within 12 hours prior to entry into the study, and renal transplant recipients were excluded. MAIN OUTCOME MEASURES: Hourly urine output (mean ± SD) was recorded 2 hours before and for 6 hours after the initiation of low- dose dopamine. Urine sodium and serum aldosterone concentrations were obtained prior to and 6 hours after the start of low-dose dopamine. RESULTS: Fifteen patients were enrolled in the study. Urine output (mean±SD) increased from 0.31 ± 0.11 mL/kg/h before to 0.80 ± 0.34 mL/kg/h following low-dose dopamine (p<0.01). Urine sodium concentrations increased from 46 ± 32 mmol/L baseline to 72 ± 53 mmol/L following low-dose dopamine (p<0.05), and serum aldosterone concentrations decreased from 415.82 ± 341.48 pmol/L prior to low-dose dopamine infusion to 256.04 ± 204.17 pmol/L (p<0.05). Cardiac output, pulmonary artery occlusion pressure, mean arterial pressure, and heart rate did not change. CONCLUSIONS: Low-dose dopamine significantly increases urine output and urine sodium excretion in oliguric, critically ill, surgical patients, and is associated with a decrease in serum aldosterone concentration. The diuretic and natriuretic effects of low-dose dopamine may be, in part, related to a dopamine-mediated inhibition of aldosterone secretion.