Dopamine at a dose of 5–10 μg/kg/min produces which predominant receptor effect?

Explanation

## Dopamine: Dose-Dependent Receptor Selectivity **Key Point:** Dopamine exhibits **dose-dependent receptor selectivity** — at low doses it activates dopaminergic receptors, and as the dose increases, β₁ and then α₁ effects predominate. ### Dose-Response Relationship ```mermaid flowchart LR A["Dopamine Infusion"]:::action --> B["Low dose<br/>1-2 μg/kg/min"]:::outcome A --> C["Intermediate dose<br/>5-10 μg/kg/min"]:::outcome A --> D["High dose<br/>> 10 μg/kg/min"]:::outcome B --> B1["Dopaminergic receptors<br/>Renal & splanchnic<br/>vasodilation"]:::action C --> C1["β₁-adrenergic effects<br/>Increased HR & contractility<br/>+ dopaminergic effects"]:::action D --> D1["α₁-adrenergic effects<br/>Systemic vasoconstriction<br/>Hypertension"]:::urgent ``` ### Receptor Effects at 5–10 μg/kg/min | Effect | Mechanism | Clinical Outcome | | --- | --- | --- | | **Dopaminergic** | D₁/D₂ receptor activation | Renal and splanchnic vasodilation; increased urine output | | **β₁-Adrenergic** | Increased cAMP in cardiac myocytes | Positive inotropic effect; increased heart rate; improved cardiac output | | **α₁-Adrenergic** | Minimal at this dose | Negligible systemic vasoconstriction | **High-Yield:** At 5–10 μg/kg/min, dopamine is the **inotropic agent of choice** in septic shock and cardiogenic shock because it combines: - Inotropic support (β₁ effect) - Renal perfusion preservation (dopaminergic effect) - Minimal peripheral vasoconstriction (α₁ effect minimal) **Mnemonic:** **"Low-Dose Dopamine = Dopaminergic + Inotropic"** - **Low** (1–2 μg/kg/min): **D**opaminergic only - **Medium** (5–10 μg/kg/min): **D**opaminergic + **I**notropic (β₁) - **High** (>10 μg/kg/min): **A**drenergic (α₁ predominates) **Clinical Pearl:** The traditional concept of "renal-dose dopamine" (1–2 μg/kg/min for renal protection) is now controversial; however, intermediate-dose dopamine (5–10 μg/kg/min) remains standard for hemodynamic support in critical illness because of its balanced dopaminergic and inotropic effects.