Conscious Sedation for Cardioversion

Direct current cardioversion (DCCV) is a safe and effective treatment for recent-onset atrial fibrillation (AF) or flutter, and when performed in the emergency department (ED), it can provide an excellent treatment option for patients, as well as reducing unnecessary hospital admissions and healthcare costs³. DCCV refers to the application of a synchronized electrical shock across a patient’s chest using a defibrillator, with the aim being to convert abnormal tachyarrhythmias back into sinus rhythm.⁸ Atrial Fibrillation (AF) is the most common arrhythmia treated in the ED.¹⁶ Recent years have seen a move toward primary electrical cardioversion (PEC) of the condition in the ED, fueled by both recognition of the limitations of chemical cardioversion and increased comfort and expertise in emergency department procedural sedation (EDPS).¹⁶ The chance of procedural success is inversely related to the duration of the arrhythmia.¹²

Indications for DCCV are as follows:

• Emergency DC cardioversion is indicated for any broad or narrow QRS complex tachyarrhythmia that causes hemodynamic decompensation. Usually, this represents heart rates in excess of 150 bpm associated with clinical shock, reduced conscious level, angina, or heart failure.¹⁵
• Relatively urgent cardioversion is indicated for supraventricular tachycardias (SVTs) and monomorphic ventricular tachycardias that have not responded to a trial of intravenous medical therapy.⁸
• Routine cardioversion is still frequently indicated in the management of AF when a rhythm rather than rate control strategy is employed.⁸ Indications for a rhythm strategy include a reversible cause of the AF, heart failure primarily caused by the AF, new onset AF, and situations where a rhythm control strategy is considered more suitable based on the clinical judgment of the attending physician.¹⁴ Numbers attributable to this last indication appear to be increasing, probably due to the perception of better symptomatic control in active patients and the increasing popularity of interventional procedures such as percutaneous pulmonary vein isolation.⁴ Initial success rates of 90% can be expected following cardioversion, but unfortunately, relapse is a common problem.¹⁷

 

No matter the location, whether in the ED, intensive care unit (ICU), angiography, or electrophysiology (EP) lab, DCCV is an uncomfortable procedure. No or minimal sedation can be associated with serious psychological sequela.⁹ Brief general anesthesia is required for elective cardioversion in hemodynamically stable patients.¹⁰ The pharmacological agent used to facilitate cardioversion should rapidly achieve the desired depth of anesthesia, should wear off rapidly, and should not cause cardiovascular or respiratory side effects.⁸

There are multiple agents that can be used for the purpose of DCCV, the ultimate choice being made by the anesthesia provider. Attending cardiologists, emergency physicians, and appropriately trained nursing staff undertake this role in a number of centers.⁷ Amongst anesthetists propofol is the most frequently utilized agent⁵ with etomidate enjoying limited popularity for hemodynamically unstable patients and sevoflurane providing an effective inhalational alternative.⁶

The Cochrane collaboration recently conducted a systematic review aimed at comparing the safety, effectiveness and adverse events associated with the various anesthetic or sedative drugs currently used for DC cardioversion.¹¹ They classified currently available agents into three groups to reflect perceived current practice:

• Traditional anesthetic induction agents: propofol, etomidate, and thiopentone.
• Inhalational anesthetic agents: sevoflurane and isoflurane.
• Drugs classified as sedative agents: diazepam and midazolam.

 

After scrutinizing 23 studies involving 1250 participants, the reviewers found no consistent differences between the agents studied and concluded that there was no need for a change in current practice.⁸

Kundar et al. reported in a double-blind study that Dexmedetomidine, when added to Propofol, lead to less patient discomfort, better sedation scores and lesser requirement of Propofol, and caused insignificant recall. Hence, it was advised to add dexmedetomidine to propofol for sedating patients undergoing elective cardioversion in a Cardiac ICU.

Propofol, a short-acting anesthetic agent, is the most commonly used medication for emergency department procedural sedation.¹ Although it can cause hypotension and respiratory depression, propofol has been extensively studied in the ED setting and has been shown to be both safe and efficacious.²

The exact anesthetic requirement deemed necessary to facilitate cardioversion has been debated ever since the original description of using thiopentone in the early 1960s.¹³ Although most anesthetists prefer utilizing a conventional depth of anesthesia, deep sedation seems perfectly acceptable to most patients.⁸ Deep sedation describes a level of sedation at which an individual cannot be easily aroused but responds purposefully to repeated or painful stimulation.⁸ It may require airway intervention and respiratory support, but cardiovascular function is usually maintained.⁴

Cardioversion is an intensely painful and stimulating procedure, but patients rarely experience pain following the procedure.⁸ The co-administration of opioids is therefore unnecessary and potentially increases the risk of apnea and post-procedural nausea and vomiting.⁸

DCCV is a common procedure used to convert abnormal rhythms using electrical stimulation to the cardiac conductive tissue. The short-term stimulation is uncomfortable, and patients need some type of sedation to prevent mental trauma and potential PTSD. The choice of sedative agent is up to the provider and based upon the stability of the patient. Old and new drugs have been used successfully, with patient safety and comfort being the ultimate goals along with conversion to a stable, perfusing rhythm.

Sources

• Butler M, Froese P, Zed P, Kovacs G, MacKinley R, Magee K, Watson ML, Campbell SG. Emergency department procedural sedation for primary electrical cardioversion—a comparison with procedural sedation for other reasons. World Journal of Emergency Medicine. 2017;8(3):165-169.
• Campbell SG, Magee KD, Zed PJ, Froese P, Etsell G, LaPierre A, et al. End-tidal capnometry during emergency department procedural sedation and analgesia: a randomized, controlled study. World Journal of Emergency Medicine. 2016;7(1):13-8.
• Carpenter A, Sargent S. DC cardioversion of atrial fibrillation and atrial flutter in the emergency department: Improving specialist protocols for the generalist. British Medical Journal Open Quality. 2018;7(4). DOI:10.1136/bmjoq-2017-000260.
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• Kowey PR. The calamity of cardioversion of conscious patients. American Journal of Cardiology. 1988;61:1106-7.
• Kundra TS, Kaur P, Nagaraja PS, Manjunatha N. (2017). To evaluate dexmedetomidine as an additive to propofol for sedation for elective cardioversion in a cardiac intensive care unit: A double-blind randomized controlled trial. Ann Card Anaesth. 2017 Jul-Sep;20(3):337-340. doi: 10.4103/aca.ACA_262_16.
• Lewis SR, Nicholson A, Reed SS, Kenth JJ, Alderson P, Smith AF. Anaesthetic and sedative agents used for electrical cardioversion. Cochrane Database Systematic Reviews. 2015;(3):CD010824.
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• Resuscitation Council (UK) Guidelines 2015. [Online] Available from https://www.resus.org.uk/resuscitationguidelines/peri-arrest-arrhythmias/ (accessed 22 March 2019).
• Stiell IG, Clement CM, Perry JJ, Vaillancourt C, Symington C, Dickinson G, et al. Association of the Ottawa Aggressive Protocol with rapid discharge of emergency department patients with recent-onset atrial fibrillation or flutter. Canadian Journal of Emergency Medicine. 2010;12(3):181-91.
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