What is the recommended dose and rate of isoprenaline (isoproterenol) infusion?

Isoprenaline Infusion Dosing and Administration

For adults with shock and hypoperfusion states, start isoprenaline at 0.5 mcg/min (0.25 mL of diluted solution) and titrate up to 5 mcg/min, with rates over 30 mcg/min used in advanced stages of shock. 1

Standard Adult Dosing for Shock

Preparation and Initial Rate

• Dilute 5 mL (1 mg) of isoprenaline in 500 mL of 5% Dextrose Injection to create a standard concentration 1
• Start infusion at 0.5 mcg/min (0.25 mL of diluted solution per minute) and increase gradually to 5 mcg/min (2.5 mL of diluted solution per minute) based on hemodynamic response 1
• Concentrations up to 10 times greater may be used when volume limitation is essential 1
• In advanced stages of shock, rates exceeding 30 mcg/min have been employed 1

Titration Parameters

• If heart rate exceeds 110 beats per minute, decrease or temporarily discontinue the infusion 1
• Adjust infusion rate based on heart rate, central venous pressure, systemic blood pressure, and urine flow 1
• Maximal bronchodilator and hemodynamic effects occur within 2 to 5 minutes of starting or stopping the infusion 2

Pediatric Dosing

The American Heart Association recommends an initial infusion rate of 0.1 mcg/kg/min in children, with the usual therapeutic range being 0.1 to 1 mcg/kg/min. 1

• Start at the lowest recommended dose (0.1 mcg/kg/min) and titrate upward based on clinical response 1
• No well-controlled studies exist to establish definitive pediatric dosing, so careful monitoring is essential 1

Bronchospasm During Anesthesia

For acute bronchospasm occurring during anesthesia, a different approach is used:

• Dilute 1 mL (0.2 mg) to 10 mL with Sodium Chloride Injection or 5% Dextrose Injection 1
• Administer 10 to 20 mcg (0.5 to 1 mL of diluted solution) as a bolus intravenous injection 1
• The initial dose may be repeated when necessary 1

Critical Monitoring Requirements

Cardiovascular Monitoring

• Continuous cardiac rhythm monitoring is mandatory, as isoprenaline may induce cardiac arrhythmias and myocardial ischemia 1
• A defibrillator should be readily available during administration 3
• Monitor for tachyarrhythmias, palpitations, angina, ventricular arrhythmias, and pulmonary edema 1

Hemodynamic Assessment

• Track heart rate, systemic blood pressure, and central venous pressure continuously 1
• Monitor urine output as a marker of tissue perfusion 1
• Research demonstrates that isoprenaline increases heart rate and systolic pressure while decreasing diastolic pressure, with minimal change in mean arterial pressure at doses around 2 mcg/min 4

Absolute Contraindications

Isoprenaline is contraindicated in patients with tachycardia, ventricular arrhythmias, and angina pectoris. 3, 1

• Do not use in patients with pre-existing tachycardia or ventricular arrhythmias 1
• Contraindicated in angina pectoris due to increased myocardial oxygen demand 1
• Exercise extreme caution in patients with coronary artery disease or cardiomyopathy 3

Important Safety Considerations

Drug Interactions

• Never administer isoprenaline simultaneously with epinephrine, as both are direct cardiac stimulants and may induce serious arrhythmias 1
• Effects may be potentiated by tricyclic antidepressants, monoamine oxidase inhibitors, levothyroxine, and certain antihistamines (chlorpheniramine, tripelennamine, diphenhydramine) 1
• Beta-adrenergic blocking drugs (e.g., propranolol) antagonize the cardiostimulating and bronchodilating effects 1

Solution Preparation and Stability

• Inspect visually for particulate matter and discoloration before administration 1
• Do not use if the injection is pinkish or darker than slightly yellow, or if it contains a precipitate 1
• Diluted solution should be used immediately, and unused material should be discarded 1

Sulfite Sensitivity

• Isoprenaline contains sodium metabisulfite, which may cause allergic reactions ranging from mild to severe, including anaphylaxis or asthmatic episodes 1
• However, in life-threatening situations, the presence of metabisulfite should not preclude use, as alternatives may not be satisfactory 1

Common Adverse Effects

Expect nervous system effects including nervousness, headache, dizziness, and visual blurring 1. Cardiovascular effects are dose-dependent and include tachycardia, palpitations, and in severe cases, Adams-Stokes attacks 1. Other reactions include flushing, sweating, mild tremors, pallor, nausea, and dyspnea 1.