Cardioversion lecture

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Cardioversion : 

Cardioversion Advanced Principles of Anesthesia University of New England School of Nurse Anesthesia

General Considerations : 

General Considerations Most cardioversions are scheduled in advanced. Typically done in areas outside of the operating room, such as post-anesthesia care unit (PACU), holding areas of cardiac catheterization labs, coronary care units (CCU) or minor procedure rooms. Airway and monitoring equipment as well as anesthesia and emergency drugs required but anesthesia machine may or may not be present. Emergency cardioversion sometimes necessary due to acute changes with severe hemodynamic instability

Cardioversion: Indications : 

Cardioversion: Indications Used most commonly to restore sinus rhythm in atrial fibrillation and atrial flutter. Atrial fibrillation is the most common cardiac dysrhythmia and associated with significant morbidity and mortality.

Cardioversion: Indications : 

Cardioversion: Indications Patients benefiting most include those with recent onset and those who a sinus mechanism improves hemodynamics. Symptomatic atrial fibrillation < 12 months duration. History of embolism. No response to medications.

Cardioversion: Indications : 

Cardioversion: Indications Supraventricular tachycardias which are refractory to medical management. Less effective in treating arrhythmia caused by increased automaticity (ie, digitalis-induced or catecholamine-induced).

Cardioversion: Mechanism of Action : 

Cardioversion: Mechanism of Action Cardioversion refers to an electrical energy discharge that is synchronized with the large R or S wave of the QRS complex. Synchronization in the early part of QRS complex avoids energy delivery in the early phase of repolarization when ventricular fibrillation can be easily induced. Transient delivery of electrical current causes a momentary depolarization of most cardiac cells. This allows the sinus node to resume normal pacemaker activity.

Atrial Fibrillation : 

Atrial Fibrillation Irregular and often rapid heart rhythm in which atrial contractions are irregular, disorganized and chaotic. Atrial rate may be up to 400-600 per minute. Irregular impulses reach AV node but not all are conducted. Ventricles beat slower, often at rates of 110- 180 beats/min

Atrial Fibrillation:Cardiovascular Causes : 

Atrial Fibrillation:Cardiovascular Causes Valvular heart disease Left ventricular hypertrophy Coronary artery disease Hypertension Cardiomyopathy Sick sinus syndrome Pericarditis

Atrial fibrillation: Other causes : 

Atrial fibrillation: Other causes Hyperthyroidism Alcohol Use Pulmonary Embolism Pneumonia Cardiovascular surgery

Atrial Fibrillation:Medical Management : 

Atrial Fibrillation:Medical Management Control rate of ventricular response. Can be accomplished with: Ca-channel blockers (diltiazem or verapamil) Beta blockers (metoprolol or esmolol) Digoxin Restore and maintain normal rhythm. Pharmacologic methods include: Quinidex (quinidine),Pronestyl (procainamide), Norpace (disopyramine),Tambocor (flecainide acetate), Rythmol (propafenone), Betapace (sotalol), Tikosyn (dofetilide), Cordarone (amiodarone) and Ibutilide (Corvert). Prevent embolic stroke (4.5%). Anticoagulation therapy. Coumadin, Heparin, Aspirin.

Atrial Flutter : 

Atrial Flutter Much less common than atrial fibrillation. Characteristic flutter waves with atrial rates of 250-350. Maybe regular or irregular ventricular response.

Atrial Flutter: Causes : 

Atrial Flutter: Causes 30% no underlying cardiac disease. 30% coronary artery disease. 30% hypertensive cardiac disease. Conditions include cardiomyopathy, hypoxia, chronic obstructive pulmonary disease, thyrotoxicosis, pheochromocytoma, electrolyte imbalance, and alcohol consumption.

Atrial Flutter: Medical Management : 

Atrial Flutter: Medical Management Ventricular rate control, thromboembolism prevention and Pharmacological conversion like that for atrial fibrillation, although atrial flutter may be less tolerated and more difficult to treat medically. Vagal manuevers or IV adenosine may help diagnose the atrial rhythm by slowing or blocking the conduction through AV node.

Other Treatments : 

Other Treatments Surgical treatments include Cox-Maze procedure or Mini-Partial Maze procedure which consists of creating a number of incisions in the atrium that disrupt the reentrant circuits. Radiofrequency, microwave and cryothermy are also methods to ablate pathways. Pulmonary vein ablation.

Cardioversion:Preoperative Considerations : 

Cardioversion:Preoperative Considerations Although procedure is brief, thorough and detailed history and physical exam should be performed on each patient. Consider underlying cardiovascular pathology, concurrent illnesses, current medical regimen including anticoagulation. History of previous thromboembolization should be noted and brief neurologic exam performed immediately prior to procedure.

Cardioversion:Preoperative Considerations : 

Cardioversion:Preoperative Considerations Standard NPO procedures maintained and risks of pulmonary aspiration (i.e. GERD, gastroparesis) assessed. Confirm persistent of arrhythmia by 12- lead EKG immediately prior to procedure. Continue meds preoperatively. Laboratory values within normal limits.

TransesophogealEchocardiography (TEE) : 

TransesophogealEchocardiography (TEE) Used to guide anticoagulation for cardioversion. TEE visualizes the left atrial appendage If thrombi not present, data suggest that patients can be cardioverted. If thrombi visualized, cardioversion is deferred and a standard 3-week anticoagulation regimen. TEE-guided approach with short-term anticoagulation can be considered a safe clinically-effective alternative to conventional management.

TEE : 

TEE

Cardioversion: Setup : 

Cardioversion: Setup Standard monitors required. Airway equipment for intubation, mask/ bag device, supplemental O2 and suction essential if no anesthesia machine available in procedure area. Assure reliable IV access prior to beginning. Full of emergency medications and IV anesthesia agents.

Cardioversion: Anesthetic Technique : 

Cardioversion: Anesthetic Technique Premedication may not be required. Midazolam may be useful. Brief period of amnesia or general anesthesia required. Preoxgenate with 100% O2 prior to administration of sedative-hypnotic. As soon as consciousness is lost, the patient is cardioverted. Eyelid response can be used as a rough gauge for depth of sedation. Airway maintained and supported until pt awake.

Cardioversion: Anesthetic Agents : 

Cardioversion: Anesthetic Agents Midazolam associated with longer recovery times. Can be reversed. Etomidate provides more hemodynamic stability, but myoclonus (40%) may interfere with EKG interpretation. Propofol produces greater hypotension as a bolus due to myocardial depression. Slow induction can attenuate this drop.

TEE and Cardioversion:Anesthetic Technique : 

TEE and Cardioversion:Anesthetic Technique TEE may be performed immediately prior to cardioversion in order to evaluate for the presence of thrombus in the atria. Requires deeper sedation in order to tolerate passage of TEE probe. Airway can be anesthetized topically prior to procedure in order to avoid deeper levels of sedation and loss of airway control.

TEE and Cardioversion:Anesthetic Technique : 

TEE and Cardioversion:Anesthetic Technique Set up and preoxygenate as usual. Topical anesthesia to pharynx. Versed 1-2 mg IV and Alfentanil 250-500 mcg IV to facilitate passage of scope. If no thrombi present, Propofol 50-150 mg IV given for actual cardioversion. Can be done with LMA and volatile agents as well. Some cardiologists prefer this for TEE passage. May have to remove air from LMA to facilitate passage of TEE probe.

Cardioversion: Complications : 

Cardioversion: Complications Transient myocardial depression. Post-conversion arrhythmias, VT, VF or asystole. Arterial embolism that can cause stroke or organ damage. Burns, bruises, or pain from electrodes. Myocardial injury. Trauma to extremities, spine, dislocations. DEATH

Monophasic vs. Biphasic Shock : 

Monophasic vs. Biphasic Shock Research suggests that biphasic shock for cardioversion is more efficient that monophasic, requiring lower energy levels. Clinical benefit not yet established in terms of lessened myocardial damage, reduction of atrial stunning and thromboembolic risk.

The end……… : 

The end………

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