The effect of 'renal-dose' dopamine on renal tubular function following cardiac surgery: assessed by measuring retinol binding protein (RBP)

Objective: Acute renal failure complicating open heart surgery is not uncom mon. Dopamine infusion (2.5-4.0 mu g/kg per min) has often been advocated f or prophylactic 'renal protection' in this setting despite little objective evidence of real benefit. We aimed to investigate whether dopamine offers any 'renal protection' in patients with normal heart and kidney functions u ndergoing routine coronary artery bypass grafting (CABG). Urinary excretion of retinol-binding protein (RBP), previously validated as a sensitive and accurate marker of early renal tubular injury, was used to assess the renal effects of dopamine during the first postoperative week. Methods: Forty co nsecutive patients from the elective waiting list were prospectively random ized into two equal groups: those in Group A received dopamine infusion at 'renal dose' (2.5-4.0 mu g/kg per min) starting from induction of anaesthes ia for 48 h, whereas those in Group B served as untreated controls. Daily m easurements were made of weight-adjusted urine output (ml/kg), fluid balanc e (input/output), serum creatinine, blood urea and urinary REP. Statistical comparisons were made using Mann-Whitney U-test. Results: The two groups m atched in terms of age, time and temperature on cardiopulmonary bypass, num ber of grafts performed and perioperative haemodynamic status. No differenc es were detected in the weight-adjusted urine output, fluid balance, serum creatinine and blood urea between the groups. Control subjects (Group B) sh owed an increase in urinary REP during the first and second postoperative d ays (323 +/- 4 mu g/mmolCr and 50 +/- 3 mu g/mmolCr; mean +/- SD). However, patients treated with dopamine (Group A) demonstrated much greater urinary excretion of REP over the same period (1257 +/- 15 mu g/mmolCr and 149 +/- 21 mu g/mmolCr; P = 0.0006 and 0.03) than those in Group B, Conclusions: D opamine given at 'renal-dose' appears to offer no renal protection in patie nts with normal heart and kidney functions undergoing elective coronary sur gery. On the contrary, it exacerbates the severity of renal tubular injury during the early postoperative period. Based on these findings we do not re commend the use of dopamine for routine renal prophylaxis in this group of patients. (C) 1999 Elsevier Science B.V. All rights reserved.