Dopamine, norepinephrine, and epinephrine are vasoconstricting drugs that help to maintain adequate blood pressure during life-threatening hypotension and help to preserve perfusion pressure for optimizing flow in various organs. The mean blood pressure required for adequate splanchnic and renal perfusion (mean arterial pressure [MAP] of 60 or 65 mm Hg) is based on clinical indices of organ function.
In patients with inadequate tissue perfusion and adequate intravascular volume, initiation of inotropic and/or vasopressor drug therapy may be necessary. Dopamine increases myocardial contractility and supports the blood pressure; however, it may increase myocardial oxygen demand. Dobutamine may be preferable if the systolic blood pressure is higher than 80 mm Hg; it has the advantage of not affecting myocardial oxygen demand as much as dopamine does. However, the resulting tachycardia may preclude the use of this inotropic agent in some patients.
Dopamine is usually initiated at a rate of 5-10 mcg/kg/min intravenously, and the infusion rate is adjusted according to the blood pressure and other hemodynamic parameters. Often, patients may require high doses of dopamine (as much as 20 mcg/kg/min).
If the patient remains hypotensive despite moderate doses of dopamine, a direct vasoconstrictor (eg, norepinephrine) should be started at a dose of 0.5 mcg/kg/min and titrated to maintain an MAP of 60 mm Hg. The potent vasoconstrictors (eg, norepinephrine) have traditionally been avoided because of their adverse effects on cardiac output and renal perfusion.
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