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Inotropes and Vasopressors

A Guide by Medicinoz App

Dosage Calculator

Select Drug Dopamine Dobutamine Norepinephrine Epinephrine Phenylephrine Vasopressin

Usual range: 2-20 mcg/kg/min

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Clinical Notes:

Inotropes: Enhancing Contractility

Beta-Adrenergic Agonists

Dobutamine

• Predominantly β1 agonist, some β2 activity
• Use: Cardiogenic shock with adequate blood pressure
• Dosage: 2.5-20 mcg/kg/min IV infusion
• Note: Yellow discoloration doesn't indicate degradation
• Monitor ECG closely for tachycardia and arrhythmias
• Can be mixed with noradrenaline in the same line

Dopamine

• Dose-dependent effects
• Low dose: renal vasodilation (controversial)
• Moderate dose: β1 agonist | High dose: α1 agonist
• Warning: Must be diluted in D5W (NS causes rapid degradation)
• Blue-green discoloration indicates oxidation

Adrenaline (Epinephrine)

• Potent α and β agonist
• Used in cardiac arrest, anaphylactic shock
• Can cause lactic acidosis even without shock
• Duration: 5-10 minutes after bolus
• Very arrhythmogenic in hypothermia
• Can cause severe pulmonary edema in left heart obstruction

PDE3 Inhibitors & Glycosides

Milrinone

• Loading dose: 50 mcg/kg over 10 minutes
• Maintenance: 0.375-0.75 mcg/kg/min
• Half-life increases threefold in renal failure
• Warning: Never stop abruptly (risk of platelet crash)
• Best paired with noradrenaline
• Great for RV failure but watch for lung bleeding

Levosimendan

• Loading: 6-24 mcg/kg over 10 minutes (optional)
• Maintenance: 0.05-0.2 mcg/kg/min for 24 hours
• Effect lasts 7-10 days after 24-hour infusion
• Works even in acidosis, unlike catecholamines
• Better than dobutamine for RV failure
• Best results when given before severe shock

Digoxin

• Loading: 0.25 mg IV, then 0.25 mg every 6 hours
• Maintenance: 0.125-0.25 mg oral daily
• Toxicity more common in women and elderly
• DANGER: Calcium administration during toxicity can be fatal
• Yellow vision is a late sign of toxicity
• Reduce dose by 50% when combining with beta-blockers

Vasopressors: Increasing BP

Noradrenaline (Norepinephrine)

Predominantly α1 agonist, some β1 activity

• Strong vasoconstriction with some increase in contractility
• CRITICAL: Never administer peripherally (severe tissue necrosis risk)
• Pink discoloration indicates degradation
• Causes severe rebound hypotension if stopped suddenly
• Ineffective in profound acidosis—correct pH first

Phenylephrine

Pure α1 agonist

• Alternative to β1 agonists
• Can cause reflex bradycardia
• Useful in tachyarrhythmias requiring pressors
• Less arrhythmogenic than other vasopressors
• Consider in patients with coronary spasm

Quick Reference Table

Agent	Mechanism	Indications	Key Considerations
Dobutamine	β1 agonist	Low CO, high SVR, cardiogenic shock (BP > 90)	Tachycardia, arrhythmias
Dopamine	Dose-dependent	Limited role; avoid if possible	Nausea/vomiting, tissue necrosis with extravasation
Noradrenaline	α1, β1 agonist	Hypotension, septic shock, cardiogenic shock	Peripheral necrosis, rebound hypotension
Adrenaline	α, β agonist	Cardiac arrest, peri-arrest, anaphylaxis	Arrhythmias, hyperglycemia, renal impairment
Milrinone	PDE3 inhibitor	Acute decompensated HF, RV failure	Hypotension with loading dose, thrombocytopenia
Levosimendan	Ca sensitizer, PDE3 inhibitor	Acute decompensated HF	Expensive, headache, AF risk
Digoxin	Na/K ATPase inhibitor	Chronic HF, AF with rapid VR	Narrow therapeutic window, drug interactions

Monitoring Guidelines

Essential Monitoring

• Continuous ECG monitoring
• Blood pressure (invasive arterial line preferred)
• Central venous pressure/pulmonary artery catheter (select cases)
• Urine output
• Regular electrolyte checks (K+, Mg2+, Ca2+)
• Acid-base balance

Special Considerations

• Correct acidosis - impairs catecholamine efficacy
• Monitor for extravasation - especially with peripheral lines
• Watch for signs of digital ischemia
• Regular assessment of cardiac output/tissue perfusion
• Maintain adequate volume status before and during therapy