Inotropes and Vasopressors
A Guide by Medicinoz App
Dosage Calculator
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
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