PLASMA DOPAMINE CONCENTRATION AND EFFECTS OF LOW DOPAMINE DOSES ON URINARY OUTPUT AFTER MAJOR VASCULAR-SURGERY

To evaluate plasma dopamine concentration and the effects of low doses infusion on urinary output after abdominal vascular surgery in patien ts with renal function impairment we performed a prospective clinical study. Twenty hemodynamically stable patients (mean age 66.6 years), w ith serum creatinine concentration < 2 mg %, who undergoing general an esthesia for major vascular surgery participated. A low dose of dopami ne (3 mu g/kg/min) was administrated to patients with postoperative pr otracted urinary output < 0.5 ml/kg/hr for at least eight hours. Plasm atic determinations were taken at TO (no dopamine administration), whe n urinary output began to increase, or if nor, after two hours (T1), a t eight (T2) and 24 (T3) hours after the beginning of infusion. After 24 hours the dopamine infusion was stopped and the patient's plasmatic level was measured four hours later (T4). Dopamine plasma concentrati ons were measured using high-performance liquid chromatography. Plasma dopamine concentration increased in all patients and reached a steady state at T2 (T2 = 76.41 +/- 16.84 ng/ml). Dopamine induced a concentr ation-dependent increase in urinary output (T0 = 0.45 +/- 0.14; T1 = 1 .49 +/- 1.11; T2 = 2.34 +/- 1.44; T3 = 1.57 +/- 0.57; T4 = 0.85 +/- 0. 7 ml/kg/hr). Three patients did not have an enhanced urinary output af ter dopamine infusion; they did have a prolonged clamping time and ope ration time (162 +/- 24 and 570 +/- 30 min, respectively). We conclude that low dose dopamine induces a dose-dependent increase of urinary o utput. This phenomenon also has been found in patients when their plas ma concentration had not yet reached the steady-state. Lack of respons iveness to dopamine suggests a renal function impairment probably due to the prolonged aortic clamping time.