Thoracic epidural anesthesia for coronary bypass surgery affects autonomic neural function and arrhythmias

Abstract

Background: : In recent years, the invasiveness of coronary reconstruction has been markedly reduced. Awake off-pump coronary artery bypass (AOCAB), coronary bypass surgery with thoracic epidural anesthesia (TEA) without general anesthesia and cardiopulmonary bypass), has been reported in the literature. Because the details of this technique are still unclear, we evaluated its usefulness by examining the autonomic neural state and the incidence of arrhythmia.

Methods: : Fifty-five patients who underwent elective coronary artery bypass grafting (CABG) between April and December 2003 were included in the study. Patients who underwent CABG under high TEA alone comprised group A, those who underwent CABG under general anesthesia combined with TEA comprised group B, and those who underwent CABG under general anesthesia alone comprised group C. Holter electrocardiography was performed before and after surgery, and perioperative electrocardiograms were recorded (before surgery and during surgery, postoperative days 0-3, and postoperative day 7). On obtained electrocardiograms, the autonomic neural state was evaluated by analysis of heart rate variability, and the incidence of atrial fibrillation.

Results: : Concerning the autonomic neural state, sympathetic inhibition was observed during TEA in both groups A and B. After discontinuation of TEA, sympathetic activity recovered. Vagal activity was not inhibited in group A, but decreased during surgery and gradually recovered after surgery in group B. Evaluation of the balance between sympathetic and vagal activities showed that sympathetic activity became predominant rapidly on postoperative day 2 in group B but gradually after surgery in group A. The incidence of postoperative atrial fibrillation was the highest in group B.

Conclusions: : In AOCAB, because there is no vagal inhibition, vagal dominance can be maintained after surgery. This may be associated with the lower incidence of postoperative atrial fibrillation in group A compared with group B. Further studies are necessary to evaluate the details of AOCAB.