Renal hemodynamics during norepinephrine and low-dose dopamine infusions in man
Richer, M.; Robert, S.; Lebel, M.
Critical Care Medicine 24(7): 1150-1156
1996
ISSN/ISBN: 0090-3493 PMID: 8674327 Document Number: 460220
Objectives: To characterize the effects of pressor doses of norepinephrine and low-dose dopamine (3 mu-g/kg/min) on renal hemodynamics in man, as well as to determine the clinical relevance of combining dopamine with norepinephrine. Design: Prospective, single-blind, randomized study. Setting: Clinical research unit of a tertiary care hospital. Subjects: Six healthy male volunteers ranging in age between 20 and 28 yrs. Interventions: The subjects were assigned randomly to four treatments (1 wk apart) in which renal hemodynamics and electrolyte excretion were assessed. Treatments consisted of 180-min infusions of the following: a) 0.9% sodium chloride (control); b) pressor doses of norepinephrine; c) dopamine at 3 mu-g/kg/min; and d) pressor doses of norepinephrine and dopamine at 3 mu-g/kg/min. Pressor doses of norepinephrine were defined as doses required to increase mean arterial pressure (MAP) by 20 mm Hg. Measurements and Main Results: Glomerular filtration rate and renal blood flow were derived from inulin and para-aminohippurate clearances, respectively. Urine output and urine solute excretion were also determined. The mean norepinephrine dose required to increase MAP by 22 +- 2 mm Hg was 118 +- 30 ng/kg/min (range 76 to 164). After the addition of dopamine, similar doses of norepinephrine resulted in an MAP increase of 15 +- 4 mm Hg. Glomerular filtration rate and urine output were comparable under all conditions. The infusion of norepinephrine decreased renal blood flow from 1241 +- 208 to 922 +- 143 mL/min/1.73 m-2 (p = .03). The addition of dopamine returned renal blood flow to baseline values. The clearance of urine sodium increased significantly with the infusion of dopamine alone (p = .03). All subjects completed the four treatment periods. Adverse events, manifested mostly as palpitations and flushing, were rare and self-limiting. Conclusions: The addition of dopamine (3 mu-g/kg/min) to pressor doses of norepinephrine normalized renal blood flow in healthy volunteers. These hemodynamic changes were not reflected In urine output and glomerular filtration rate; hence, these monitoring parameters may be unreliable indicators of renal function in the setting of vasopressor therapy. In addition, systemic effects were observed with dopamine (3 mu-g/kg/min), as indicated by a decrease in MAP.