From the Guidelines
Isoproterenol is an effective treatment for severe beta blocker-induced bradycardia, and the recommended dosage is an infusion of 1-20 mcg/min based on heart rate response, as stated in the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1.
Key Considerations
- The dosage of isoproterenol can be adjusted based on the patient's heart rate response, with a range of 1-20 mcg/min 1.
- Isoproterenol works as a non-selective beta-adrenergic agonist that stimulates both beta-1 and beta-2 receptors, effectively competing with and overcoming the blockade caused by beta blockers.
- Alternative treatments to consider include glucagon (3-10 mg IV bolus followed by 3-5 mg/hr infusion), high-dose insulin with glucose, calcium salts, and vasopressors.
- In refractory cases, cardiac pacing or extracorporeal support may be necessary.
Important Side Effects
- Isoproterenol may cause hypotension, arrhythmias, and myocardial ischemia, particularly in patients with coronary artery disease.
- Continuous cardiac monitoring is essential during administration of isoproterenol.
Clinical Context
- The 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay provides evidence-based recommendations for the treatment of bradycardia, including the use of isoproterenol 1.
- The guideline emphasizes the importance of individualizing treatment based on the patient's underlying condition, medical history, and response to treatment.
From the FDA Drug Label
Isoproterenol Hydrochloride Injection is a beta-adrenergic agonist indicated: To improve hemodynamic status in patients in distributive shock and shock due to reduced cardiac output (1) Beta-adrenergic blocking drugs may reduce cardiostimulating and bronchodilating effects of isoproterenol (7)
The indication for isoproterenol does not directly mention its use for severe beta blocker induced bradycardia. However, it does mention that beta-adrenergic blocking drugs may reduce the effects of isoproterenol. Given this information, isoproterenol may be considered for severe beta blocker induced bradycardia, but with caution, as its effectiveness may be reduced by the beta blocker. 2 2
From the Research
Treatment Options for Severe Beta Blocker Induced Bradycardia
- Atropine and isoproterenol have been used to treat bradycardia and hypotension caused by beta-blocker overdose, but their effectiveness can be inconsistent 3, 4
- Glucagon is an alternative therapy that can increase heart rate and myocardial contractility, and improve atrioventricular conduction, even in the presence of beta-receptor blocking drugs 3, 4, 5
- High-dose insulin euglycaemic therapy, catecholamines, and vasopressors have also been associated with improved haemodynamics and reduced mortality in beta-blocker poisoning 5
- Isoproterenol can be used as an antidote for beta-blocker-induced bradycardia, but its use should be considered after first-line treatments have failed 4
Considerations for Treatment
- The choice of treatment should be based on the severity of the bradycardia and the presence of other symptoms such as hypotension or heart failure 4, 5
- Patients with severe beta-blocker overdose may require mechanical ventilation and temporary pacing in addition to pharmacological treatment 4, 6
- The use of multiple treatments simultaneously can make it difficult to determine the effectiveness of individual interventions 5
Specific Treatment Regimens
- Glucagon can be administered as a 50 micrograms/kg iv loading dose, followed by a continuous infusion of 1-15 mg/h, titrated to patient response 3
- High-dose insulin euglycaemic therapy can be initiated with a bolus dose, followed by a continuous infusion of 1-10 units/kg/h 5
- Isoproterenol can be used as an antidote, but the optimal dosage and administration regimen are not well established 4