General Medical Information

Arrhythmias

David M. Barrs

The clinician must treat an arrhythmia if it is hemodynamically significant and also must search for the underlying cause. Acute cardiac disease, hypoxia, hypotension, acid-base abnormalities, hypokalemia, and central venous or pulmonary artery catheter stimulation of the heart are common causes of arrhythmias. Hypokalemia may be worsened by intraoperative hyperventilation and resultant respiratory alkalosis and by intraoperative fluid replacement and fluid shifts. The underlying causes of cardiac arrhythmias must be evaluated rapidly and corrected. Some arrhythmias, such as nodal rhythm and bradycardia, are common during general anesthesia and usually do not require treatment. Others can be hemodynamically significant and may be tolerated poorly by a heart already affected by the negative inotropic action of the anesthetic agent.

Supraventricular tachyarrhythmias may be treated with i.v. adenosine, verapamil, propranolol, esmolol, or diltiazem. Intravenous digoxin may be used to control atrial fibrillation or persistent flutter. Ventricular tachycardia is treated initially with lidocaine, using a loading bolus dose of 1 to 1.5 mg/kg of body weight given intravenously, with a repeat bolus of 0.5 mg/kg 10 minutes later, followed by a continuous infusion of 1 to 4 mg/min. In all cases of tachyarrhythmias, direct current cardioversion may be necessary if severe hypotension, cardiac ischemia, or congestive heart failure and pulmonary edema develop. Simple bradyarrhythmias (e.g., sinus bradycardia) usually respond well to atropine. More significant bradyarrhythmias (e.g., sick sinus syndrome) need cardiac pacing under the supervision of a cardiologist. Any of these serious bradyarrhythmias or tachyarrhythmias will mandate observation in the cardiac care unit or with telemetry.