What is the recommended starting dosage for isoprenaline (isoproterenol) infusion?

Isoprenaline Infusion Dosage

For shock and hypoperfusion states, start isoprenaline at 0.5 mcg/minute (0.25 mL/minute of diluted solution) and titrate up to 5 mcg/minute based on hemodynamic response, with rates exceeding 30 mcg/minute reserved for advanced shock. 1

Standard Preparation and Initial Dosing

For adults with distributive shock or shock due to reduced cardiac output:

• Dilute 5 mL (1 mg) of isoprenaline in 500 mL of 5% Dextrose Injection to create a 2 mcg/mL solution 1
• Start infusion at 0.5 mcg/minute (0.25 mL/minute of diluted solution) 1
• Titrate gradually up to 5 mcg/minute (2.5 mL/minute of diluted solution) based on patient response 1
• Concentrations up to 10 times greater may be used when volume limitation is essential 1

Titration Parameters and Monitoring

Adjust infusion rate based on the following hemodynamic parameters:

• Heart rate: If exceeds 110 beats/minute, consider decreasing or temporarily discontinuing the infusion 1
• Central venous pressure 1
• Systemic blood pressure 1
• Urine flow 1

Advanced shock management:

• Rates over 30 mcg/minute have been used in advanced stages of shock 1
• These higher doses should be reserved for severe hemodynamic compromise when lower doses prove inadequate 1

Pediatric Dosing

For children, the American Heart Association recommends:

• Initial infusion rate: 0.1 mcg/kg/min 1
• Usual dosing range: 0.1 mcg/kg/min to 1 mcg/kg/min 1
• Note: No well-controlled pediatric studies exist to establish definitive dosing 1

Alternative Indication: Bronchospasm During Anesthesia

For bronchospasm occurring during anesthesia:

• Dilute 1 mL (0.2 mg) to 10 mL with Sodium Chloride Injection or 5% Dextrose Injection 1
• Give 10-20 mcg (0.5-1 mL of diluted solution) as bolus intravenous injection 1
• May repeat initial dose when necessary 1

Critical Safety Considerations

Contraindications - Do not use isoprenaline in patients with: 1

• Tachycardia
• Ventricular arrhythmias
• Angina pectoris

Important warnings:

• May induce cardiac arrhythmias and myocardial ischemia, especially in patients with coronary artery disease or cardiomyopathy 1
• Contains sodium metabisulfite, which may cause allergic reactions including anaphylaxis in sulfite-sensitive patients 1
• Should not be administered simultaneously with epinephrine, as both are direct cardiac stimulants and may induce serious arrhythmias 1

Drug interactions requiring dose adjustment:

• Effects may be potentiated by tricyclic antidepressants, MAO inhibitors, levothyroxine, and certain antihistamines (chlorpheniramine, tripelennamine, diphenhydramine) 1
• Effects are antagonized by beta-blockers such as propranolol 1
• Contraindicated in patients with asthma when used for bradycardia, as it may precipitate atrial fibrillation 2

Common Pitfalls to Avoid

• Do not use if the injection appears pinkish, darker than slightly yellow, or contains precipitate 1
• Discard unused portions - diluted solution should be used immediately 1
• Avoid excessive tachycardia - heart rates above 110 beats/minute warrant dose reduction or temporary discontinuation 1
• Monitor for ischemia - particularly in patients with underlying coronary disease, as isoprenaline increases myocardial oxygen demand 1
• Have defibrillator readily available when using for bradycardia, as it may precipitate rapid atrial fibrillation in patients with WPW syndrome 2