Makindo Medical Notes

💉 Dopamine hydrochloride is an inotropic sympathomimetic agent used in the management of shock with hypotension and low cardiac output. Its effects are dose-dependent: at low doses it increases renal perfusion, at moderate doses it enhances myocardial contractility, and at high doses it causes vasoconstriction. ⚠️ Must be administered via a central line due to risk of tissue necrosis if extravasation occurs.

📘 About

• Always check the BNF entry here for detailed prescribing, dilution, and monitoring advice.
• Dopamine acts primarily on β₁-adrenergic receptors (inotropy) and D₁ receptors (renal vasodilation) at lower doses, with α₁ stimulation at higher doses causing vasoconstriction.
• It is now rarely used in favour of noradrenaline (norepinephrine) as the first-line vasopressor in septic or cardiogenic shock (per NICE/Surviving Sepsis guidelines).

⚙️ Mode of Action

• At low doses (1–3 μg/kg/min) → acts on D₁ receptors in renal and mesenteric vessels → vasodilation and increased renal blood flow.
• At moderate doses (3–10 μg/kg/min) → stimulates β₁ receptors → ↑ myocardial contractility, stroke volume, and cardiac output.
• At high doses (>10 μg/kg/min) → stimulates α₁ receptors → peripheral vasoconstriction and ↑ systemic vascular resistance (SVR).
• Also causes release of endogenous noradrenaline from sympathetic nerve terminals.

💊 Indications & Dosing

• For shock with hypotension and loss of vascular tone (e.g. cardiogenic, septic, or post–cardiac surgery shock) where perfusion remains inadequate despite fluids.
• Initial adult dose: 2–5 micrograms/kg/min by IV infusion.
• Titrate upwards to achieve target mean arterial pressure (MAP); typical range 5–20 μg/kg/min.
• Always dilute in Glucose 5% or 0.9% Sodium Chloride before infusion — do not mix with bicarbonate (inactivates dopamine).
• Monitor ECG, BP, urine output, and peripheral perfusion closely.

🔄 Interactions

• See BNF for full list.
• ⚠️ Avoid co-administration with MAOIs (hypertensive crisis) — reduce dose markedly if unavoidable.
• May enhance arrhythmogenic potential when combined with other sympathomimetics or anaesthetic agents (e.g. halothane).
• Tricyclic antidepressants potentiate vasopressor effects.

⚠️ Cautions

• Administer via central venous access to prevent extravasation and tissue necrosis.
• Use cautiously in tachyarrhythmias or myocardial ischaemia (may worsen oxygen demand).
• Correct hypovolaemia before starting dopamine — it is ineffective without adequate preload.
• Monitor acid–base balance and lactate; prolonged use can worsen peripheral perfusion.

🚫 Contraindications

• Phaeochromocytoma — risk of severe hypertension and arrhythmia.
• Tachyarrhythmias (e.g. VF, VT) — may exacerbate rhythm disturbance.
• Untreated hypovolaemia.
• Hypersensitivity to dopamine or bisulphite preservatives.

💥 Adverse Effects

• Cardiac: palpitations, tachycardia, arrhythmia, angina.
• Vascular: severe hypotension or hypertension (depending on dose/response), peripheral ischaemia, or gangrene (from vasoconstriction or extravasation).
• CNS: headache, anxiety, restlessness.
• Ocular: dilated pupils (mydriasis).
• GI: nausea and vomiting (dopaminergic stimulation of chemoreceptor trigger zone).

🧠 Teaching Note

Dopamine’s effect depends on dose and receptor selectivity — it exemplifies the graded receptor response concept. In modern practice, it has been largely replaced by noradrenaline as the preferred vasopressor due to a lower risk of arrhythmias and more predictable haemodynamic control. It remains a useful teaching model for understanding adrenergic pharmacology and receptor physiology.

📚 References

• BNF: Dopamine Hydrochloride
• Surviving Sepsis Campaign (2023): Hemodynamic Support Guidelines
• NICE NG51: Sepsis — Recognition, Diagnosis and Early Management
• Rang & Dale’s Pharmacology (10th ed.)