Lidocaine is commonly used as a local and regional anesthetic. A Class Ib antiarrhythmic agent, lidocaine is also approved by the Food and Drug Administration (FDA) to treat ventricular arrhythmias that occur during cardiac manipulation (i.e., cardiac surgery) and life-threatening arrhythmias such as those that are ventricular in origin or those occurring during an acute myocardial infarction (Facts and Comparisons, 2022). In this blog we will focus on the use of lidocaine to treat cardiac arrhythmias. How does it work?

Mechanism of Action

In a healthy heart, the ventricles contract in response to impulses from the sinoatrial (SA) node, the natural cardiac pacemaker. Normal myocardial cells allow a limited amount of sodium ions to enter, which leads to controlled depolarization. Conversely, ischemic or injured myocardial cells allow a rapid infusion of sodium ions. This causes the cells to depolarize much more quickly than normal and then begin firing spontaneously, creating an ectopic pacemaker that may trigger a ventricular arrhythmia.
 
Lidocaine works in injured or ischemic myocardial cells to slow the influx of sodium, raising the cells’ electrical stimulation threshold (EST) of the ventricle and His-Purkinje conduction system. The increased EST prolongs depolarization in the ischemic cells, suppresses the automaticity of conduction tissue and returns control to the SA node.

Adult Dosing (Facts and Comparisons, 2022)

The typical dosing for lidocaine is 50 to 100 mg, administered as an intravenous (IV) bolus at a rate of approximately 25 to 50 mg/minute. Monitor the patient’s electrocardiogram (ECG) closely. If the cardiac rhythm does not respond to the initial injection of 50 to 100 mg, a second dose may be repeated after 5 minutes. The maximum dosage is 200 to 300 mg, administered during a 1-hour period.
 
Lidocaine may be administered (off-label) to treat sudden cardiac arrest due to ventricular fibrillation or pulseless ventricular tachycardia, unresponsive to cardiopulmonary resuscitation, defibrillation, and epinephrine. The initial IV dose is a 1 to 1.5 mg/kg bolus. For refractory ventricular fibrillation or pulseless ventricular tachycardia, repeat 0.5 to 0.75 mg/kg bolus every 5 to 10 minutes (maximum cumulative dose of 3 mg/kg). Follow with a continuous infusion of 1 to 4 mg/minute after perfusion returns. Dosage should be adjusted for patients with liver or kidney impairment.

Contraindications (Facts and Comparisons, 2022)

Lidocaine is contraindicated in patients with a history of hypersensitivity to local anesthetics of the amide type. Lidocaine hydrochloride injection should not be used in patients with Stokes-Adams syndrome, Wolff-Parkinson-White syndrome or with severe degrees of sinoatrial, atrioventricular or intraventricular block in the absence of an artificial pacemaker.

Monitoring (Facts and Comparisons, 2022)

In addition to ECG monitoring, laboratory tests should include liver function tests and lidocaine concentrations. In patients requiring the drug for greater than 24 hours, lidocaine level monitoring is recommended.
 
For complete information, please consult the drug’s specific package insert or the Nursing2022 Drug Handbook® + Drug Updates. 

References
Facts and Comparisons (2022, June 23). Lidocaine Injection. Facts and Comparisons. https://fco.factsandcomparisons.com/lco/action/search?q=lidocaine%20injection&t=name&acs=false&acq=lidocaine%20injection