Newsletter



SCA Newsletter -- October 2001

Thoracic Epidural Anesthesia And Perioperative Arrhythmias

Reviewer: Mark A. Chaney, M.D.
University of Chicago

Perioperative atrial as well as ventricular arrhythmias remain a serious problem, particularly in patients undergoing cardiothoracic surgery.1 Atrial fibrillation is perhaps the most encountered perioperative arrhythmia in patients undergoing cardiac and/or thoracic surgery and is fairly common. It is thought that sympathetic nerve activity plays an important role in development of perioperative arrhythmias, particularly tachyarrhythmias. Because thoracic epidural anesthesia with local anesthetics blocks sympathetic nervous system outflow, it has been suggested that it may be beneficial in patients at increased risk for perioperative arrhythmias. Recent animal and human clinical investigations indicate that use of thoracic epidural anesthesia in patients undergoing cardiothoracic surgery may help decrease the incidence of perioperative arrhythmias. 2-4

Meissner and associates studied electrophysiologic effects (right atrial and ventricular repolarization by recording monophasic action potentials) after thoracic epidural anesthesia and complete blockade of the autonomous nervous system in awake dogs.2 They found that thoracic epidural anesthesia with lidocaine significantly increased ventricular monophasic action potential duration and that changes in monophasic action potential duration were paralleled by a concomitant prolongation of effective refractory period at higher rates so that the ratio of effective refractory period to action potential duration was unaffected. These results indicate that thoracic epidural anesthesia may be protective against generation of ventricular arrhythmias mediated by increased sympathetic tone because lengthening of repolarization and prolongation of refractoriness, in certain circumstances, is antiarrhythmic. This investigation also revealed that the beneficial role of thoracic epidural anesthesia may be stronger at ventricular sites as compared to atrial sites. Thus, thoracic epidural anesthesia may have antiarrhythmic properties, especially in situations that result in a shortening of repolarization, such as ventricular and atrial (mainly atrial flutter and fibrillation) tachyarrhythmias and increased sympathetic tone or myocardial ischemia.

Oka and associates investigated whether postoperative epidural bupivacaine could reduce the tachyarrhythmias following pulmonary resection.3 Fifty patients with lung cancer scheduled for elective pulmonary resection were prospectively randomized to receive either epidural bupivacaine or epidural morphine during the postoperative period. Tachyarrhythmias were diagnosed by using the continuous heart rate trend and arrhythmia trend with a central monitoring system. While postoperative analgesia was not different between the two groups, the incidence of postoperative tachyarrhyth-mias was significantly lower in patients receiving epidural bupivacaine when compared to patients receiving epidural morphine (1/23 versus 7/25, respectively, p = 0.05). These results indicate that the continued infusion of thoracic epidural bupivacaine can reduce supraventricular tachyarrhythmias during the postoperative period following thoracic surgery, presumably because of attenuation of the sympathotonic status.

Jideus and associates evaluated whether thoracic epidural anesthesia with bupivacaine could possibly reduce the incidence of atrial fibrillation in patients after coronary artery bypass grafting.4 They studied forty-one patients undergoing coronary artery bypass grafting supplemented with thoracic epidural anesthesia intraoperatively and postoperatively (another eighty patients served as the control group). Postoperative atrial fibrillation occurred in 31.7% of the thoracic epidural patients and in 36.3% of the controls (not significant). However, thoracic epidural anesthesia significantly suppressed sympathetic activity, as indicated by less pronounced increases in blood levels of norepinephrine (p = 0.03), epinephrine (p = 0.02) and neuropeptide U (p = 0.01) during the postoperative period in patients receiving thoracic epidural anesthesia when compared to controls. Further
more, heart rate variability (expressing sympathetic activity) was lower (p = 0.01) and increases in heart rate were less (p < 0.001) during the postoperative period in patients receiving thoracic epidural anesthesia compared to controls. These results indicate that thoracic epidural bupivacaine, while not able to decrease clinical atrial fibrillation significantly, is able to significantly reduce sympathetic activity during the postoperative period in patients following coronary artery bypass grafting.

In summary, perioperative atrial and ventricular arrhythmias remain a serious problem in patients undergoing cardiac and/or thoracic surgery. Thoracic epidural anesthesia with local anesthetics attenuates sympathetic nervous system outflow (as assessed in a number of ways) and thus has the potential to decrease the incidence of clinical arrhythmias, as some studies have shown. Further studies are required in order to identify the exact beneficial mechanism of action and which patients will benefit the most from this technique.

REFERENCES

  1. Allessie MA, et al. Pathophysiology and prevention of atrial fibrillation (current perspective). Circulation 2001; 103: 769-777.
  2. Meissner A, et al. Effects of thoracic epidural anesthesia with and without autonomic nervous system blockade on cardiac monophasic action potentials and effective refractoriness in awake dogs. Anesthesiology 2001; 95: 132-138.
  3. Oka T, et al. Thoracic epidural bupivacaine attenuates supraventric-ular tachyarrhythmias after pulmonary resection. Anesth Analg 2001; 93:253-259.
  4. Jideus L, et al. Thoracic epidural anesthesia does not influence the occurrence of postoperative sustained atrial fibrillation. Ann Thorac Surg 2001; 72: 65-71.


Table of Contents
Archived Newsletter Articles


© Society of Cardiovascular Anesthesiologists
Questions or comments? Please send email to webmaster@scahq.org