Anaesthesia and amiodarone

Two recent reports support and one report disputes the existence of dangerous interactions between the new benzofuran antiarrhythmic amiodarone and the anaesthetic state. We have reviewed our experience with 17 anaesthetics administered to 16 patients taking amiodarone. Haemodynamics and serum amiodarone levels were evaluated where available. Twelve cases involved cardio-pulmonary bypass; of these, three patients died. There were no deaths in the non-cardio-pulmonary bypass group. The charts of 30 patients with poor left ventricular function, who were not receiving amiodarone but who were undergoing coronary artery bypass surgery, were reviewed to establish a comparison group. Interactions were manifested in three forms: nodal rhythm and/or complete heart block developed in ten of 15 patients (one patient had a preoperative pacemaker inserted for the sick sinus syndrome), poor cardiac output requiring intra-aortic balloon pump augmentation developed in six of 12 cardio-pulmonary bypass patients, or, a state of alpha adrenergic blockade leading to a low systemic vascular resistance despite alpha agonist therapy developed in two of 16 patients. We conclude that dangerous, fatal interactions may occur in patients taking amiodarone who undergo general anaesthesia with cardio-pulmonary bypass. Anaesthesia for non-cardiac surgery may be associated with haemodynamically significant bradyarrhythmias. We recommend aggressive invasive monitoring, including pulmonary artery catheterization and consideration of an atrio-ventricular pacemaker in high risk patients.