Effect of dopamine on renal blood flow and cardiac output
I. L. Gordon, R. Wesley, D. H. Wong, M. D. Ingegno, B. Spivak and S. E. Wilson
Department of Surgery, University of California, Irvine Medical Center, Orange, USA.
OBJECTIVE: To characterize the relationship between changes in renal blood
flow and cardiac output induced by dopamine, hypothesizing that at low
doses renal blood flow changes more than cardiac output. DESIGN:
Anesthetized swine had renal blood flow and cardiac output measured during
either continuous dopamine infusions (2 to 8 micrograms/kg per minute) or
bolus dosing (1 to 16 micrograms/kg), and increases in both were compared.
Two different fluid protocols were compared using constant dopamine
infusions. In the constant pulmonary capillary wedge pressure protocol,
intravenous fluids were titrated to keep this parameter constant. In the
other protocol, fluid therapy was held constant at 10 mL/kg per hour.
RESULTS: With infusions, mean increases in renal blood flow and cardiac
output were relatively equal. The maximum increase was 35% at 8
micrograms/kg per minute under the constant pulmonary capillary wedge
pressure protocol, with no significant differences (P > .1) found
between the change in renal blood flow and cardiac output at any dose in
either protocol. With bolus dosing, renal blood flow increased
significantly more than cardiac output at 1, 4, and 8 micrograms/kg (P <
.05). CONCLUSION: Disproportionate increases in renal blood flow compared
with cardiac output at low bolus doses show initial renal responses to be
independent of cardiac output. The infusion data suggest that renal
responses exhibit tachyphylaxis or that cardiac output slowly accommodates
to decreased total peripheral resistance.
