Norepinephrine alone versus norepinephrine plus low-dose dopamine: enhanced renal blood flow with combination pressor therapy.

Six normotensive, anesthetized dogs were infused intravenously with short-term, incremental infusions of norepinephrine (NE) with or without the addition of iv dopamine (DA) (4 micrograms/kg X min). The infusion of NE alone and in combination with low-dose DA produced similar, significant increases in mean arterial pressure. During the infusion of pressor doses of NE, the addition of DA resulted in significantly higher renal blood flow (p less than .001) and lower renal vascular resistance (p less than .001) than infusions of NE alone. Thus, the renal vasodilating action of low-dose DA persisted despite infusions of NE, a potent vasopressor which decreases renal blood flow. This suggests that shock patients receiving therapy with NE should be good candidates to receive low-dose DA to enhance renal blood flow.