Good Morning 20 August 2002 Anesthetic Considerations in

Good Morning 20 August 2002

Anesthetic Considerations in Patients With Cardiac Arrhythmias 麻醉科 林子富

Perioperative Cardiac Arrhythmias ® Incidence: ® Overall: 70. 2% ® > 90% in cardiac surgery ® Majority (90. 7%): ASA 1 and 2 ® Without preexisting cardiac dz. or noncardiac surgery: benign and short-lived ® 18% to 30% (conventional intermittent EKG) vs. 60% to 80% (continuous Holter) ® Common factors: ® Tracheal intubation, extubation & known heart dz. ® More frequently observed in neurologic, thoracic and head and neck procedures.

Causes of Perioperative Cardiac Arrhythmias ® Abnormalities of cardiac impulse formation (small portion): ® In normal automaticity: ® ® In abnormal automaticity: ® ® Bradycardia and escape beats with high dose narcotics A less negative diastolic potential In triggered automaticity: ® Etopic beat activated by preceding action potential l l “Early afterdepolarization” during phase 3 “Delayed afterdepolarization” during phase 4 ® Abnormalities ® of impulse conduction: Re-entry excitation (most common mechanism underlying premature beasts and tachyarrhythmias)

Physiologic Impact ® Tachyarrhythmias: ® Reduce diastolic ventricular filling ® Decrease cardiac output and BP ® Coronary perfusion suffers ® Myocardial ischemia ® Significant bradyarrhythmias also decrease cardiac output

Anesthsia and Arrhythmia ® Higher ® Anesthetic agents altering cardiac impulse generation and conduction ® ® incidence Volatile agents causing AV dissociation Perioperative ischemia and elevated catecholamine level ® ® Light anesthetic levels Hypoxemia Hypercarbia Exogenous epinephrine and aminophylline

Sinus Node Dysfunction ® Transient ® Autonomic ® implication Neuraxial blockade, laryngoscopy, endotracheal instrumentation ® B 1 agonist ® Atropine ® Cardiac pacing

Paroxysmal Supraventricular Tachycardia Onset and termination are usually abrupt. ® Higher incidence in major vascular, cancer, and orthopedic surgery ® Death rate in non-cardiac surgery remains high: 50% ® Causes of PSVT: ® ® Narrow-QRS PSVT ® ® ® AV node and accessory pathways re-entry: 85% to 90% SA node and intra-atrial re-entry: casual mechanism With WPW syndrome: Vagal maneuver, adenosine, B-bloker, and cardioversion Without WPW syndrome: Vagal maneuver, adenosine, Ca++ channel blocker followed by cardioversion Wide-QRS PSVT ® IV procainamide and amiodarone and cardioversion

Atrial Fibrilattion >90% of SVTs in the post-op setting ® Etiology: ® ® ® Cardiac cause Systemic process Electrolyte imbalance If ventricular rate increases in an acute fashion perioperatively leading to significant hemodynamic perturbation, treatment should be prompt. ® ® Verapamil, esmolol, digoxin DC cardioversion ® ® Acute onset ( <1 year) LA diameter < 45 mm No ventricular enlargement Prior anticoagulation for arrhythmias older than 4 to 5 days

Atrial Flutter ® ® ® Less frequently encountered Same etiological factors as AF Not typically responsive to antiarrhythmic drugs Pacing Catheter ablation

Ventricular Arrhythmias ® Benign ® Ventricular premature beats and nonsustained ventricular tachycardia ® ® ® 6. 3% incidence of VPBs, only 0. 62% severe adverse outcomes Structurally normal hearts Reduction of VPBs and NSVT in GA

Ventricular Arrhythmias ® Potentially malignant ® Sustained monomorphic ventricular tachycardia ® ® >90% previous infarction leading to LV dysfunction Antiarrhythmic effects of volatile agents (animal study) Lidocaine, procainamide, amiodarone High-energy cardioversion

Ventricular Arrhythmias ® Malignant ® Polymorphic ventricular tachycardias ® ® ® ® ® Mostly due to torsades de points or acute ischemia Significant prolongation of the Q-T interval Correction of ischemia Asynchronous DC cardioversion Repletion of K+ and Mg++ Atropine and isoproterenol ( not in ischemia ) V-pacing Lidocaine or phenytoin Ventricular fibrillation ® ® High-energy shock Drugs only for prevention of recurrence

Summary Common but most are transient and benign Greater implications in the presence if significant cardiac structural abnormality Special challenges of the operative setting ® ® ® Hypo- and hyper-tension, low-flow rate, volume overload, high catecholamine state, hypoxia, hypercarbia, temperature alterations, and pericardial tamponade… Antiarrhythmics with their proarrhythmic potential Devices for cardioversion, defibrillation, and pacing and familiarity with their use. .

References 1. 2. Anesthetic Considerations in Patients With Cardiac Arrhythmias, Pacemakers, and AICDs. International Anesthesiology Clinics 39(4): 21 -42, 2001 Fall Perioperative Cardiac Dysrhythmias diagnosis and management. Anesthesiology 1997; 86: 1397 -424

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