Isoprenaline (Isoproterenol) Infusion Protocol
The recommended protocol for isoprenaline infusion is to start at 0.5 mcg to 5 mcg per minute as an intravenous infusion for shock, and titrate gradually based on patient response. 1
Dosing Guidelines by Indication
For Shock/Hemodynamic Support
- Initial dose: 0.5-5 mcg/minute as an intravenous infusion 1
- Titrate gradually based on clinical response 1
- For persistent bradycardia after atropine failure: Consider isoprenaline at 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV 2
- For refractory cases: Can increase dose carefully while monitoring for adverse effects 2
For Bronchospasm During Anesthesia
- 10-20 mcg as an intravenous injection 1
- For severe asthma: Dose range of 0.0375 to 0.225 mcg/kg/minute has shown efficacy with maximal bronchodilator effect occurring within 2-5 minutes 3
Preparation and Administration
Standard Preparation
- Dilute in compatible IV fluid (normal saline preferred) 4
- When infusion pumps are unavailable, can dilute in 500 mL of crystalloid solution and infuse using a drop regulator or micro-infusion set 5
- Administer through a central venous catheter when possible to minimize risk of extravasation 5
Administration Precautions
- Do not mix with epinephrine HCl due to compatibility concerns 4
- Avoid mixing with alkali-labile drugs including norepinephrine bitartrate 4
- Frequently check the infusion site for signs of extravasation as substantial skin necrosis may occur 5
Monitoring Requirements
- Continuous cardiac monitoring is essential during administration 2
- Measure arterial blood pressure and heart rate frequently (every 5-15 minutes) 5
- Monitor for signs of excessive tachycardia, arrhythmias, or myocardial ischemia 1
- Consider arterial blood pressure monitoring for patients requiring higher doses 2
Contraindications
Isoprenaline is contraindicated in patients with:
- Tachycardia 1
- Ventricular arrhythmias 1
- Angina pectoris 1
- Use caution in patients with asthma as it may precipitate atrial fibrillation 5
Special Considerations
- In post-cardiac transplant patients: Reduce dose as these patients may have increased sensitivity 5
- Use with caution in patients taking dipyridamole or carbamazepine 5
- A defibrillator should be readily available when administering to patients with Wolff-Parkinson-White syndrome due to risk of rapid atrial fibrillation 5
- Age-related decreases in cardiac and peripheral vascular responsiveness to isoprenaline have been observed, potentially requiring dose adjustments in elderly patients 6
Potential Adverse Effects
- Tachycardia and palpitations are common adverse reactions 1
- May induce cardiac arrhythmias and myocardial ischemia 1
- Contains metabisulfite which may cause allergic reactions 1
- Paradoxical bradycardia has been reported in approximately 7% of patients during isoprenaline infusion, particularly in young patients with hypervagotonia 7
Drug Interactions
- Do not administer simultaneously with epinephrine as combined effects may induce serious arrhythmias 1
- Concomitant use with tricyclic antidepressants, MAOIs, levothyroxine, or certain antihistamines may potentiate clinical response 1
- Beta-adrenergic blocking drugs may reduce cardiostimulating and bronchodilating effects 1
Remember that isoprenaline is a potent beta-adrenergic agonist requiring careful titration and continuous monitoring. The protocol should be implemented in settings where appropriate cardiac monitoring and resuscitation equipment are readily available.