What is the dosage and formula for administration of inotropes (inotropic agents)?

Dosage and Administration of Inotropic Agents

The administration of inotropic agents requires careful dosing according to specific formulas based on patient weight, with close monitoring of hemodynamic response and potential adverse effects. 1, 2

First-Line Inotropic Agents

Dobutamine

• Initial dose: 2-3 μg/kg/min without loading dose, progressively modified according to symptoms and clinical status 1
• Dose range: 2-20 μg/kg/min, with dose-related hemodynamic actions 1, 2
• In patients receiving beta-blocker therapy, doses may need to be increased to as high as 20 μg/kg/min to restore inotropic effect 1
• Requires gradual tapering when discontinuing (decrease by steps of 2 μg/kg/min) 1

Dopamine

• Low dose (2-3 μg/kg/min): Stimulates dopaminergic receptors with limited effects on diuresis 1
• Medium dose (3-5 μg/kg/min): Provides inotropic effect through beta-adrenergic stimulation 1
• High dose (>5 μg/kg/min): Acts as vasopressor through alpha-adrenergic stimulation 1
• Use with caution in patients with heart rate >100 bpm due to risk of tachycardia and arrhythmias 1

Second-Line Inotropic Agents

Milrinone

• Loading dose: 25-75 μg/kg administered over 10-20 minutes 1, 3
• Maintenance infusion: 0.375-0.75 μg/kg/min 1, 3
• Should be diluted prior to maintenance dose administration using 0.45% Sodium Chloride, 0.9% Sodium Chloride, or 5% Dextrose 3
• Requires dose adjustment in renal impairment based on creatinine clearance:
  • CrCl 5 mL/min: 0.2 μg/kg/min
  • CrCl 10 mL/min: 0.23 μg/kg/min
  • CrCl 20 mL/min: 0.28 μg/kg/min
  • CrCl 30 mL/min: 0.33 μg/kg/min
  • CrCl 40 mL/min: 0.38 μg/kg/min
  • CrCl 50 mL/min: 0.43 μg/kg/min 3

Levosimendan

• Optional loading dose: 12 μg/kg over 10 minutes (avoid bolus in hypotensive patients with SBP <100 mmHg) 1
• Maintenance infusion: 0.1 μg/kg/min, which can be decreased to 0.05 or increased to 0.2 μg/kg/min 1
• Has both inotropic and vasodilator properties 1

Enoximone

• Loading dose: 0.25-0.75 mg/kg 1
• Maintenance infusion: 1.25-7.5 μg/kg/min 1

Vasopressors

Norepinephrine

• No loading dose required 1
• Infusion rate: 0.2-1.0 μg/kg/min 1, 2
• First-line vasopressor for most shock states, especially in hypotensive patients with adequate fluid resuscitation 2

Epinephrine

• Bolus: 1 mg IV during resuscitation, repeated every 3-5 minutes if needed 1
• Infusion rate: 0.05-0.5 μg/kg/min 1, 2
• Reserved for persistent hypotension despite adequate cardiac filling pressures and use of other vasoactive agents 1, 2

Clinical Considerations for Administration

Indications for Inotropic Therapy

• Should only be administered in patients with low systolic blood pressure or low cardiac index with signs of hypoperfusion or congestion 1
• Signs of hypoperfusion include cold/clammy skin, vasoconstriction, acidosis, renal impairment, liver dysfunction, or impaired mentation 1
• Therapy should be reserved for patients with dilated, hypokinetic ventricles 1

Treatment Strategy Based on Blood Pressure

• SBP >100 mmHg: Consider vasodilators (nitroglycerin, nitroprusside) 1
• SBP 90-100 mmHg: Consider vasodilator and/or inotrope (dobutamine, levosimendan) 1
• SBP <90 mmHg: Consider fluid challenge, inotropes (dopamine), vasopressors, and mechanical support 1

Monitoring and Safety

• Continuous clinical monitoring and ECG telemetry is required due to risk of arrhythmias 1
• Blood pressure should be monitored, invasively or non-invasively 1
• Titrate all inotropes to the lowest effective dose to achieve adequate organ perfusion 2
• Monitor for adverse effects including tachyarrhythmias, myocardial ischemia, and peripheral tissue ischemia 2

Duration of Therapy

• Inotropic agents should be administered as early as possible and withdrawn as soon as adequate organ perfusion is restored and/or congestion reduced 1
• For bridge therapy to heart transplant or mechanical circulatory support, longer durations may be necessary 1, 4, 5

Pitfalls and Caveats

• Long-term use of inotropes is potentially harmful except when used as palliative therapy or as a bridge to advanced therapies 1
• Infusion of most inotropes is accompanied by increased incidence of both atrial and ventricular arrhythmias 1
• In patients with atrial fibrillation, dobutamine/dopamine may facilitate conduction through the AV node and lead to tachycardia 1
• Dobutamine is associated with more arrhythmias compared to milrinone, while milrinone is more likely to cause hypotension 6
• Inotropes should be used with caution in patients with severe aortic or mitral stenosis 1