PRO: Conscious Neuraxial Anesthesia is a Viable Alternative to General Anesthesia in Cardiac Surgery

Paul Kessler, MD
University Hospital
Frankfurt, Germany

Since the first report of a patient undergoing awake coronary artery revascularization in 20001, high thoracic epidural anesthesia for cardiac surgery has been established as an alternative to standard anesthetic tech-niques in various medical centres worldwide.2-11 Currently, over 500 cases of patients from Europe, the US, Brazil and India under going awake CABG surgery with high thoracic epidural anesthesia alone have been published in case reports, observational cohort studies and controlled clinical trials. To date, approximately 2,000 procedures with this new anesthetic technique have been performed without reports of significant adverse events worldwide. Most of these patients underwent awake off-pump coronary artery revascularization using small lateral thoracotomy incisions, lower sternotomy incisions or full median sternotomy surgical approaches.12 Only two case reports describe patients undergoing aortic or mitral valve surgery with high thoracic epidural anesthesia using cardiopulmonary bypass.13,14

Neuraxial techniques in awake cardiac surgery are restricted to high thoracic epidural anesthesia. Recent experiences as well as prospective randomized studies and meta-analyses have demonstrated advantages of high thoracic epidural analgesia combined with general anesthesia when compared to general anesthesia alone.15-17 Clinical studies indicate that high thoracic epidural analgesia reduces the stress response to surgery, reduces the time to postoperative extubation and improves early postoperative pulmonary function. Further potential advantages of high thoracic epidural anesthesia include thoracic sympatholysis with subsequent improvement of coronary perfusion, decreased heart rate and endogenous stress response, and a reduced risk for myocardial ischemia perioperatively.18

So it seemed to be patently logical to apply high thoracic epidural anes-thesia using local anesthetics combined with opioids as the sole anesthetic technique in awake patients undergoing CABG surgery. Published data confirm our own encouraging results and prove that high thoracic epidural anesthesia as the sole anesthetic technique in cardiac surgery can not only be performed in feasibility studies, but has been established as a valid alternative to general anesthesia in selected patients.19

As long as the application of larger amounts of sedatives is avoided, appropriate ventilation and oxygenation of awake patients intraoperatively is guaranteed.19 Additional IV sedation intraoperatively is not mandatory since, apart from standard oral premedication, all patients benefit from the sedative effect of the epidural opioids reabsorbed. Undeniably, however, awake CABG is associated with a certain amount of psychological stress. But, in contrast to published presumptions,20 compared to general anesthesia, the patient's stress response is not increased21 and postoperative surveys have shown an extraordinary level of patient acceptance of this new anesthetic technique.19

The fundamental precondition for successful awake CABG surgery is an appropriate and highly defined patient selection. Thus, this anesthetic technique is not applicable to all kinds of coronary artery stenoses. Espe-cially patients with left anterior descending artery (LAD) or right coronary artery (RCA) stenosis, that are easily accessible from the surgical point of view ,may be operated on with high thoracic epidural anesthesia only, while revascularization of the left circumflex artery (LCx) requires Trendelenburg positioning and luxation of the heart and is therefore difficult to perform.In addition, patients with highly impaired left ventricular function depending on a certain cardiac sympathetic tone should be excluded from this new technique. Further exclusion criteria arise from common contraindications of epidural puncture, such as compromised coagulation (thromboplastin time <80%, prothrombin time >40 sec, platelets <100/nl), bleeding disorders and the use of any antiplatelet drugs (e.g. ticlopidine, clopidogrel etc.) within the last 10 days. Finally, patients undergoing awake CABG surgery have to be extensively and properly informed about pros and cons of this anesthetic technique, potential adverse events and the pre- and intraoperative course.

The controversy of awake CABG has been always a discussion of the potential risks of epidural hematoma and subsequent adverse neurological sequelae related to high thoracic epidural anesthesia. Based on the currently available data on 10,000 high thoracic epidurals combined with general anesthesia for cardiac surgery, epidural hematoma has been reported in only one patient.22 In this patient, who underwent aortic valve replacement, epidural hematoma developed postoperatively after alteplase, a thrombolytic drug, was used to flush a dysfunctional central venous catheter. After immediate laminectomy, neurologic restitution and integrity was gained in this patient. However, this adverse event demonstrates that it is crucial to monitor cardiac patients with high thoracic epidural anesthesia meticulously and tightly in the postoperative period to detect epidural bleeding early. Apart from this case report, the potential risk of epidural hematoma in cardiac surgery seems to be comparable to non-cardiac procedures, especially when off-pump surgical techniques using low-dose heparinization only are performed.23 It is self-evident that awake CABG should only be performed by anesthesiologists highly experienced with neuraxial blockade, e.g. high thoracic epidurals.

Advantages of CABG with high thoracic epidural anesthesia compared to general anesthesia have been described: safe and reliable hemodynamics intraoperatively,18, 19 faster mobilization and even daily life activities a few hours after surgery,24 short-term ICU stay or even bypass of the ICU,8,19,25 shorter intrahospital stay and, in conclusion, a modern fast tracking technique for cardiac patients8,26 with significant cost reduction potential and high patient acceptance.19 Furthermore, case reports have demonstrated advantages in patients with significant pulmonary risk factors such as COPD or post tracheal reconstruction to prevent endotracheal intubation and, consequently, potential weaning difficulties postoperatively.27 In addition, awake CABG allows for verbal intraopertive monitoring in patients with compromised cerebrovascular function, such as severe carotid artery stenosis.28

In conclusion of the published data to date and in strict consideration of defined exclusion criteria, neuraxial anesthesia for awake off-pump one and two vessel coronary artery revascularisation is a viable alternative to general anesthesia in highly selected patients. Especially patients with severe pulmonary coexisting disease and those with only a moderately impaired left ventricular function may benefit from high thoracic epidural anesthesia alone. However, more than by using standard anesthetic techniques, a team approach and excellent communication skills of the anaesthesiologist and the cardiac surgeon are crucial.

References

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