What muscle relaxant to use after cardioversion (cardioversion procedure)?

From the Guidelines

Muscle relaxers are not typically used after cardioversion procedures, and their use is not recommended due to potential interactions with cardiac medications and unwanted sedation. Cardioversion is an electrical procedure to restore normal heart rhythm, and muscle relaxers are not part of the standard post-procedure care 1. Instead, patients usually receive anticoagulants like warfarin, apixaban, rivaroxaban, or dabigatran to prevent blood clots, and antiarrhythmic medications such as amiodarone, sotalol, or flecainide to maintain normal rhythm.

If a patient experiences muscle pain or soreness at the site where the electrical paddles were placed, over-the-counter pain relievers like acetaminophen or ibuprofen are generally sufficient. Muscle relaxers like cyclobenzaprine or baclofen could potentially interfere with cardiac medications or cause unwanted sedation in the post-cardioversion period 1. The use of muscle relaxants during anesthesia has been studied, and it has been found that they can improve muscle relaxation, especially when using high doses of sufentanil or remifentanil, or low doses of a hypnotic 1. However, this does not apply to the post-cardioversion period, where the focus is on maintaining normal heart rhythm and preventing blood clots.

Some key points to consider when evaluating the use of muscle relaxers after cardioversion include:

• The potential for interactions with cardiac medications, such as antiarrhythmic medications and anticoagulants
• The risk of unwanted sedation, which can affect the patient's ability to recover from the procedure
• The availability of alternative treatments for muscle pain and soreness, such as over-the-counter pain relievers
• The importance of consulting with the cardiologist who performed the procedure before prescribing any medication, to ensure that it will not interact with cardiac medications or affect heart rhythm 1.

From the Research

Muscle Relaxers for Cardioversion

The choice of muscle relaxer for cardioversion depends on various factors, including the patient's medical history, the type of procedure, and the desired level of sedation.

• Midazolam is a commonly used sedative for cardioversion, with a study showing it to be effective in 99% of cases 2.
• Propofol is another option, with a study comparing its effectiveness to etomidate, midazolam, and midazolam with flumazenil, finding it to be well-tolerated and lacking myoclonus, prolonged sedation, and resedation noted with the other groups 3.
• Diazepam has also been compared to midazolam, with a study finding it to be associated with fewer minor adverse events and a quicker recovery time 4.
• A systematic review of 23 studies comparing various anaesthetic and sedative agents for electrical cardioversion found that there is no evidence to suggest that current anaesthetic practice for cardioversion should change, with most study authors concluding that the agents compared were adequate for cardioversion procedures 5.

Comparison of Muscle Relaxers

The following muscle relaxers have been compared in various studies:

• Midazolam vs. diazepam: diazepam was associated with fewer minor adverse events and a quicker recovery time 4.
• Midazolam vs. propofol: propofol was well-tolerated and lacked myoclonus, prolonged sedation, and resedation noted with midazolam 3.
• Etomidate vs. midazolam: etomidate was found to have a shorter induction time and recovery time, but was associated with myoclonus in some patients 3.
• Propofol vs. etomidate: propofol was found to be well-tolerated and lacked myoclonus, prolonged sedation, and resedation noted with etomidate 3.

Adverse Events

The following adverse events have been reported with the use of muscle relaxers for cardioversion:

• Hypotension: reported with midazolam, etomidate, and propofol 3, 4.
• Myoclonus: reported with etomidate 3.
• Prolonged sedation: reported with midazolam 3.
• Resedation: reported with midazolam after flumazenil was discontinued 3.
• Nausea and vomiting: reported with various agents, including propofol and etomidate 5.
• Pain at injection site: reported with various agents, including propofol and etomidate 5.