Dopamine

Dopamine's clinical effect depends entirely on the dose — low, medium, and high ranges activate different receptors and can either protect the kidneys or clamp them down. Knowing the cutoffs changes your patient's outcome.

Dopamine is a naturally occurring catecholamine precursor to norepinephrine that acts on three different receptor types depending on infusion rate. At low doses (1–5 mcg/kg/min), it stimulates dopaminergic receptors, historically thought to promote renal and mesenteric vasodilation — though current evidence does not support 'renal dose' dopamine as protective. At moderate doses (5–10 mcg/kg/min), beta-1 adrenergic effects dominate: increased heart rate and contractility, raising cardiac output. This is the range used for symptomatic bradycardia unresponsive to atropine and for cardiogenic shock. At high doses (10–20 mcg/kg/min), alpha-1 vasoconstriction predominates, increasing SVR and blood pressure similarly to norepinephrine. Dopamine must be administered via a central line when possible; peripheral IV extravasation causes tissue necrosis. Phentolamine is the antidote for extravasation — injected locally into the affected tissue. Continuous cardiac monitoring and arterial blood pressure monitoring are required. Titrate to target MAP (typically ≥65 mmHg) per provider orders. Abrupt discontinuation can cause rebound hypotension — always taper.

Key Distinctions

Don't confuse dopamine's dose-dependent receptor profile with norepinephrine's predominantly alpha effect — dopamine at moderate doses is more chronotropic (raises HR more), which is why septic shock guidelines now favor norepinephrine first-line. Students often believe 'renal dose' dopamine is evidence-based; it is not recommended for renal protection. Extravasation antidote is phentolamine for dopamine, not to be confused with holding pressure or applying nitroglycerin paste.

Clinical Pearl

Think 'D-B-A' as dose climbs: Dopaminergic (low), Beta (moderate), Alpha (high). Each jump in dose shifts the receptor target and the clinical effect entirely.