What the Anesthesiologist Should Know before the Operative Procedure

Cardioverion, or, more specifically, synchronized direct current cardioversion, is the discharge of direct current (DC) electricity through the heart timed with the QRS complex. The goal of synchronized cardioversion is the treatment of arrhythmia and the restoration of normal sinus rhythm.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Synchronized cardioversion may be undertaken emergently, urgently, or electively depending upon the clinical situation and patient condition. Tachyarrhythmias associated with hemodynamic instability may require emergent cardioversion, while cardioversion of stable arrhythmias may be performed electively in the fasting state (NPO) under sedation or general anesthesia.

Emergent: Immediate synchronized cardioversion is indicated to treat unstable tachyarrhythmias associated with clear QRS complexes and a pulse. Ventricular rates often exceed 150 beats per minute. Patients frequently demonstrate signs of poor perfusion including hypotension, angina, altered mental status, or heart failure. Sedation prior to cardioversion is desirable, although cardioversion should not be delayed if sedatives are not immediately available.

Urgent: Synchronized cardioversion is indicated for hemodynamically stable atrial fibrillation, atrial flutter, or supraventricular tachycardias with a known duration of less than 24 to 48 hours. Pharmacologic approaches to rate control may be attempted prior to cardioversion. Time should be taken to ensure a fasting state (NPO), to obtain informed consent, and to administer adequate sedation.

Elective: Synchronized cardioversion is indicated for the treatment of hemodynamically stable atrial fibrillation or atrial flutter with a duration of more than 48 hours (or of unknown duration). Current guidelines recommend 3 to 4 weeks of anticoagulant therapy prior to and 4 weeks of anticoagulant therapy following elective synchronized cardioversion. Patients with a history of intermittently therapeutic anticoagulation or at high risk for thromboembolic events often undergo transesophageal echocardiography immediately prior to cardioversion to rule out left atrial thrombus.

2. Preoperative evaluation

Patients presenting for elective synchronized cardioversion should undergo standard preanesthetic evaluation. When possible, laboratory tests should be performed to assess adequacy of anticoagulant therapy (e.g., INR of 2 to 3 in patients taking warfarin). In addition, a 12-lead electrocardiogram (ECG) is warranted to confirm the continued presence of arrhythmia prior to cardioversion.

Medically unstable conditions warranting further evaluation include angina, heart failure, hypotension, symptomatic tachycardia, stroke, or transient ischemic attack (TIA). Delaying cardioversion may be indicated if: evidence of subtherapeutic anticoagulation or transesophageal echocardiographic examination demonstrates left atrial thrombus.

3. What are the implications of co-existing disease on perioperative care?

b. Cardiovascular system:

Acute/unstable conditions: Immediate synchronized cardioversion is recommended to treat hemodynamically unstable supraventricular tachycardia, atrial fibrillation, atrial flutter, or monomorphic ventricular tachycardia with a pulse. Rhythms with an ectopic or automatic focus are not typically responsive to synchronized cardioversion.

Baseline coronary artery disease or cardiac dysfunction—Goals of management: Patients with persistent arrhythmia presenting for elective cardioversion almost always have coexisting coronary artery disease, valvular disease, or ventricular dysfunction. These patients require continuous ECG monitoring throughout the procedure to detect ischemia or new arrhythmia.

Patients with severe conduction system disease may develop bradycardia following cardioversion.

c. Pulmonary:

Heavy sedation or a brief general anesthetic is usually requested for the procedure. Supplemental oxygen should be administered by face mask or nasal cannula to maintain adequate arterial oxygen saturation throughout the procedure. Airway management equipment must be on hand in case intubation becomes necessary.

Patients with a history of COPD or reactive airway disease should continue to take their prescribed bronchodilators and inhaled steroids on the day of the procedure. If wheezing is heard on physical exam, nebulized bronchodilators may be administered prior to the procedure.

d. Renal-GI:

Patients presenting for elective synchronized cardioversion should adhere to ASA preprocedural fasting (NPO) guidelines. Electrolyte abnormalities should be treated prior to elective cardioversion to reduce the risk of ventricular tachycardia or fibrillation after cardioversion. Muscle relaxation is not required for the procedure. However, in patients with underlying renal insufficiency, a baseline serum potassium is helpful in deciding whether succinylcholine may be used should tracheal intubation become necessary.

e. Neurologic:

Patients with persistent atrial fibrillation or atrial flutter may develop left atrial thrombus and are at high risk for thromboembolism and neurologic events before or after synchronized cardioversion. Current guidelines recommend 3 to 4 weeks of anticoagulation before and 4 weeks of anticoagulation after elective cardioversion to prevent thromboembolic events. Patients who are considered high risk frequently undergo transesophageal echocardiographic exam prior to elective cardioversion to rule out left atrial thrombi.

f. Endocrine:

Hyperthyroidism is a potential cause of persistent atrial fibrillation and its presence should be excluded prior to elective synchronized cardioversion.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

N/A

4. What are the patient's medications and how should they be managed in the perioperative period?

Most medications are safe to continue throughout cardioversion. It is important to ensure that antiarrhythmics, beta-blockers, bronchodilators, and anticoagulants are continued on the day of cardioversion.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Patients with atrial fibrillation are occasionally treated with digitalis. In these patients a digitalis level and baseline ECG should be checked prior to cardioversion, as digitalis toxicity can predispose patients to ventricular fibrillation or tachycardia following cardioversion.

i. What should be recommended with regard to continuation of medications taken chronically?

Cardiac: Antiarrhythmics, beta-blockers, and antihypertensives should be continued on the day of cardioversion.

Pulmonary: Bronchodilators and inhaled steroids should be continued on the day of cardioversion.

Renal: Oral electrolyte supplementation should be continued to maintain normal serum electrolyte concentrations.

Antiplatelet: Antiplatelet and anticoagulant therapy should be continued before and after elective cardioversion.

Psychiatric: Psychiatric medications should be continued on the day of cardioversion.

j. How to modify care for patients with known allergies

The anesthetic plan can be modified to avoid agents that cause allergic response in individual patients. A large variety of short-acting sedatives and induction agents provide great flexibility in constructing an anesthetic plan for elective cardioversion.

k. Latex allergy – If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

N/A

l. Does the patient have any antibiotic allergies – Common antibiotic allergies and alternative antibiotics

Preprocedural antibiotics are not indicated prior to elective synchronized cardioversion.

m. Does the patient have a history of allergy to anesthesia?

A variety of short-acting induction agents may be used in patients with allergies to anesthesia.

Malignant hyperthermia (MH)

Documented: Avoid all trigger agents such as succinylcholine and inhalational agents. Follow a proposed general anesthetic plan: total intravenous anesthesia with propofol ± opioid infusion ± nitrous oxide. Ensure that an MH cart is available [MH protocol].

Local anesthetics/muscle relaxants

Local anesthetics and muscle relaxants are not required for elective synchronized cardioversion.

5. What laboratory tests should be obtained and has everything been reviewed?

Electrolytes: Serum electrolytes should be checked and corrected to reduce risk of ventricular tachycardia or fibrillation following cardioversion. Hypokalemia, in particular, is a risk factor for ventricular arrhythmia after cardioversion.

Coagulation panel: Patients taking warfarin should have a therapeutic INR (2 to 3) before cardioversion.

Other tests: 12-lead ECG should be performed prior to cardioversion to confirm presence of arrhythmia. A postprocedure ECG is frequently obtained to document sinus rhythm or resistant arrhythmia.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

Elective synchronized cardioversion is usually performed under heavy sedation or general anesthesia.

a. Regional anesthesia

Regional anesthesia is not an alternative for elective synchronized cardioversion.

General anesthesia

Patients are preoxygenated via face mask or nasal cannula and are monitored using continuous ECG, pulse oximetry, and frequent blood pressure assessment. Intravenous sedatives or induction agents are slowly titrated until the patient loses consciousness. Short-acting agents are preferred as cardioversion often requires only a few minutes of unconsciousness. Once the patient is unresponsive, direct current cardioversion is performed using 50 to 200 J of energy. One or more attempts at cardioversion may be required to achieve sinus rhythm. Patients usually regain consciousness quickly after cardioversion and are observed for a short period before being discharged from anesthesia care.

Benefits: General anesthesia reliably provides amnesia and analgesia during cardioversion.

Drawbacks: Providers must be able to perform airway management during period of unconsciousness.

Airway concerns: Equipment to provide positive-pressure ventilation and tracheal intubation must be available and ready.

c. Monitored anesthesia care or conscious sedation

Benefits: May be performed by a larger range of hospital or clinic staff.
Drawbacks: May have higher risk of recall or awareness during cardioversion.
Other Issues: Advanced airway management may be required in the event of overdose.

6. What is the author's preferred method of anesthesia technique and why?

A brief general anesthetic using judicious titration of a short-acting induction agent is the author’s preferred technique. Propofol is often used as its rapid redistribution allows for short periods of amnesia and unresponsiveness followed by a prompt return of consciousness. Care must be taken, however, to avoid hypotension and apnea during propofol administration.

What prophylactic antibiotics should be administered?

Preprocedural antibiotics are not indicated for synchronized cardioversion.

What do I need to know about the surgical technique to optimize my anesthetic care?

Synchronized cardioversion may require only a few minutes once the patient becomes unresponsive. Care must be taken to prevent overdose and prolonged sedation.

What can I do intraoperatively to assist the proceduralist and optimize patient care?

Close monitoring of vitals and airway management will allow the proceduralist to focus on rhythm assessment and cardioversion.

What are the most common intraoperative complications and how can they be avoided/treated?

Prioritize them by urgency. The most urgent complication of synchronized cardioversion is appearance of a new arrhythmia, such as bradycardia, ventricular tacchycardia, or ventricular fibrillation. ACLS algorithms should guide management of these arrhythmias. Other complications of cardioversion include thromboembolism, myocardial damage, and burn at the site of cardioversion pads. Anesthetic complications during cardioversion centers around airway management during periods of unconsciousness. Providers must have equipment ready to provide positive-pressure ventilation or tracheal intubation should the need arise.

a. Neurologic:

Unique to procedure: Patients in atrial fibrillation are at high risk for the development of left atrial thrombi and subsequent thromboembolic events. Current guidelines recommend 3 to 4 weeks of anticoagulant therapy prior to and 4 weeks of anticoagulant therapy following elective cardioversion to minimize risks of a thromboembolic event. Patients who are at high risk often undergo transesophageal echocardiographic examination of the left atrium to rule out thrombus prior to cardioversion.

b. If the patient is intubated, are there any special criteria for extubation?

Patients are not routinely intubated for synchronized cardioversion.

c. Postoperative management

What analgesic modalities can I implement?

Postprocedural analgesia is not usually required.

What level of bed acuity is appropriate?

Patients require a short period of observation after anesthesia. Most patients are discharged on the day of surgery.

What are common postoperative complications, and the ways to prevent and treat them?

Cardioversion is a brief and relatively safe procedure. Postoperative complications are rare, but the majority stem from sedative or anesthetic overdose. The resulting hypotension or hypoventilation can be managed with small doses of vasopressors or with airway management, respectively.

What's the Evidence?

Link, MS, Atkins, DL, Passman, RS. “2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care part 6: Electrical therapies”. Circulation . vol. 122. 2010. pp. S706-19. Indications for emergent and elective cardioversion.)

Singer, DE, Albers, GW, Dalen, JE. “Antithrombotic therapy in atrial fibrillation, American College of Chest Physicians evidence-based clinical practice guidelines (8th edition).”. Chest . vol. 133. 2008. pp. 546S-92S. (Anticoagulation guidelines for patients with atrial fibrillation.)

Gage, BF, Waterman, AD, Shannon, W. “Validation of clinical classification schemes for predicting stroke: Results from the National Registry of Atrial Fibrillation”. JAMA . vol. 285. 2001. pp. 2864-70. (Construction of the CHADS2 score for stroke risk assessment.)

Tracy, CM, Akhtar, M, DeMarco, JP. “American College of Cardiology/American Heart Association 2006 update of the clinical competence statement on invasive electrophysiology studies, catheter ablation, and cardioversion: a report of the American College of Cardiology/American Heart Association/American College of Physicians Task Force on Clinical Competence and Training”. J Am Coll Cardiol . vol. 48. 2006. pp. 1503-17.

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