Under what circumstances in cardiac arrest should an initial lidocaine (anti-arrhythmic medication) bolus of less than 100 mg be administered?

From the Guidelines

A lidocaine bolus of less than 100 mg should be administered in cardiac arrest for patients with lower body weight (particularly those under 50 kg), elderly patients with decreased hepatic function, patients with known liver disease, or those with heart failure. The standard adult dose for lidocaine in cardiac arrest is typically 1-1.5 mg/kg, with a usual initial bolus of 100 mg. However, dose reduction is necessary in these vulnerable populations to prevent toxicity. For smaller adults or those with compromised metabolism, an initial dose of 0.5-1 mg/kg is more appropriate, as recommended by the 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1. Lidocaine works by stabilizing cardiac cell membranes and suppressing ventricular arrhythmias by blocking sodium channels, but accumulation can lead to central nervous system and cardiovascular toxicity. When administering reduced doses, be prepared to give additional smaller boluses (typically half the initial dose) every 5-10 minutes if needed, not exceeding a total dose of 3 mg/kg. Continuous cardiac monitoring is essential as lidocaine's therapeutic window is relatively narrow, especially in compromised patients. Some key points to consider when administering lidocaine include:

• Initial dose: 0.5-1 mg/kg for vulnerable populations
• Maximum total dose: 3 mg/kg
• Administration interval: every 5-10 minutes if needed
• Importance of continuous cardiac monitoring It's also important to note that lidocaine may be considered as an alternative to amiodarone for VF/pVT that is unresponsive to CPR, defibrillation, and vasopressor therapy, as stated in the 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care 1. Overall, the use of lidocaine in cardiac arrest should be guided by the patient's individual needs and medical history, and should always be administered with caution and close monitoring.

From the Research

Circumstances for Administering Lidocaine Bolus

There are specific circumstances under which an initial lidocaine bolus of less than 100 mg should be administered in cardiac arrest. These circumstances can be identified based on the patient's condition and the potential risks associated with lidocaine administration.

• Patient Weight and Condition: The dosage of lidocaine is often determined by the patient's weight, with a typical initial bolus dose ranging from 1.0 to 1.5 mg/kg 2. For smaller patients or those with certain medical conditions, an initial bolus of less than 100 mg may be appropriate to avoid toxicity.
• Risk of Lidocaine Toxicity: Lidocaine toxicity can occur even at therapeutic doses, especially in patients with hepatic or renal impairment 3. In such cases, a lower initial bolus dose may be necessary to minimize the risk of toxicity.
• Alternative Dosing Regimens: Some studies suggest that intermittent bolus dosing of lidocaine may be an effective alternative to traditional bolus followed by drip regimens 2. This approach may involve administering smaller bolus doses at regular intervals, which could be beneficial in certain patients.

Specific Patient Populations

Certain patient populations may require special consideration when administering lidocaine, including:

• Patients with Heart Failure: A study published in 2025 found that an initial infusion rate of up to 1 mg/min was optimal for patients with heart failure and ventricular arrhythmia 4. This may translate to a lower initial bolus dose for these patients.
• Patients with Out-of-Hospital Cardiac Arrest: Research has shown that lidocaine may be effective in treating out-of-hospital cardiac arrest, but the optimal dosing regimen is still unclear 5. In these situations, a lower initial bolus dose may be administered to minimize risks and maximize benefits.

Conclusion is not allowed, so the response will continue without it

It is essential to carefully evaluate each patient's individual needs and medical history when determining the appropriate lidocaine dosing regimen. By considering these factors and potential circumstances, healthcare providers can make informed decisions about administering an initial lidocaine bolus of less than 100 mg in cardiac arrest situations, as supported by studies such as 3, 4, 5, 2, and 6.