Regional or general anaesthesia for carotid endarterectomy

This Invited Commentary is part of a Pro and Con debate and accompanies the following articles: Cedergreen P, Swiatek F, Nielsen HB. Local anaesthesia for carotid endarterectomy. Pro: protect the brain. Eur J Anaesthesiol 2016; 33:236–237 Unic-Stojanovic D, Jovic M. Local anaesthesia for carotid endarterectomy. Con: decrease the stress for all. Eur J Anaesthesiol 2016; 33:238–240 In this issue of the European Journal of Anaesthesiology, we debate the Pros and Cons of using regional or general anaesthesia for carotid endarterectomy (CEA).1,2 Experts will set out the physiological basis for and the clinical evidence supporting both the choices, together with their independent opinions, to provide a balanced overall view on this still controversial topic. Current risk factors in patients undergoing carotid endarterectomy Since 1970, CEA has emerged as the best treatment option in the prevention of cerebral infarction in patients with high-grade carotid artery stenosis.3 Given an average 5% reduction in long-term risk of stroke or death following CEA, there is a need to keep major cardiovascular events at the time of surgery lower than 4 to 5%. Most patients present with a ‘vulnerable brain’, from previous cerebral ischaemia and pathophysiologies that include diffuse atherosclerosis, coronary artery disease, chronic lung disease and diabetes mellitus. Most are taking antiplatelet or antihypertensive drugs and require temporary carotid occlusion during surgery. Current benchmarks indicate that major cardiovascular complications are even less than 2% following CEA. Indeed, perioperative rates of stroke and cardiac events have decreased by almost two-thirds over the past 30 years as a result of centralisation in high-volume centres, preoperative statin and antiplatelet therapy and tight perioperative haemodynamic control.4 Impact of the anaesthetic strategy: a balanced risk–benefit analysis In this context, does the choice of anaesthetic technique – regional vs general anaesthesia – make any difference? As discussed in the Pro and Con debate regarding ‘hard’ clinical outcomes such as myocardial infarction, stroke, pneumonia, re-intubation and death, the current answer is ‘no’ or remains ‘unclear’ given the low incidence of these adverse events. So far, in most institutions, the choice of anaesthetic techniques remains guided by local clinical practice (surgeon and anaesthetist preference) as well as patient condition and motivation. With technical advances in ultrasonic imaging, evidence to support the widespread application of ultrasonic guidance for regional anaesthesia in orthopaedic and vascular interventions has been growing.5–7 Undoubtedly, general anaesthesia is the most comfortable approach, providing safer airway management and easier ventilatory control while allowing the surgeon to operate on a fully relaxed patient. However, the insertion of a carotid shunt with its potential risk of plaque embolisation is needed more frequently despite the use of various brain monitoring tools that include stump pressure, somatosensory evoked potential, transcranial Doppler, processed EEG and near-infrared spectroscopy. In addition, anaesthetic-induced circulatory depression owing to inhibition of sympathetic neural drive and direct vasodilation requires greater vasopressor support. The higher incidence of early postoperative neurocognitive dysfunction following general anaesthesia could be linked to impairment in cerebral blood flow autoregulation, haemodynamic instability and the residual effects of general anaesthetic agents.8,9 So far, anaesthetic-associated neuroprotective effects are questionable, particularly in patients with senescent brains and atheromatous vascular disease.10 Several anaesthetic agents have also been incriminated in the reverse ‘Robin Hood’ syndrome in which abnormal cerebral vasodilation causes blood flow to be ‘stolen’ from active metabolic areas and diverted towards areas with lesser aerobic needs.11 In modern anaesthetic practice, cervical plexus blockade can be elegantly performed under ultrasound guidance with a high success rate and a low risk of procedural complications, even in patients taking dual antiplatelet therapy and in those with prior cervical surgery.12 Disadvantages of regional anaesthesia are the need for patient collaboration, remote access to the upper airways and procedural complications such as temporary unilateral diaphragmatic and vocal cord paralysis, neural injuries and epidural, and subarachnoid or intravascular injection of local anaesthetic. When a patient becomes agitated or unresponsive as a result of insufficient analgesia, a panic attack or cerebral ischaemia because of plaque embolisation or inadequate collateral blood flow, the urgent conversion of regional anaesthesia into general anaesthesia is always stressful and risky. Availability and experience with laryngeal mask airways offer new opportunities to maintain upper airways and satisfactory gas exchange under a moderate depth of anaesthesia while avoiding tracheal intubation.13 Preoperative consultation plays a key role in identifying those patients unable to tolerate a 2-hour procedure with the face and the neck covered by surgical drapes. Patients should be thoroughly informed regarding the anaesthetic and surgical approaches and emphasis should be placed on the importance of the ‘awake’ condition with verbal communication that contributes to the success of the intervention and offers the potential of preventing early neurocognitive dysfunction following CEA.9 Maintenance of the ‘awake’ state offers the unique opportunity to detect almost instantaneously any intraoperative mismatch in regional brain oxygen supply. In addition, the release of stress hormones and arousal of the sympathetic system are helpful in preventing or mitigating brain ischaemia by keeping arterial blood pressure in the upper normal range, while avoiding the administration of vasopressive agents.14 As viable cerebral tissues within the ischaemic penumbra are very sensitive to variations in blood pressure, improved early subclinical cognitive function after awake CEA (compared with general anaesthesia) could be attributed to better systemic haemodynamic control and preserved autoregulation of cerebral blood flow.8,15,16 Perspectives Taking into account the equivocal results of the GALA trial and the arguments put forward in the Pro and Con debate,17 the discussion around the ideal anaesthetic approach should be shifted from just technical aspects (regional anaesthesia vs general anaesthesia) towards a multifaceted strategy. Considering the vulnerable brain component, this protective strategy should include the best preoperative preparation, deciding an appropriate time delay after an ischaemic event and seeking common ground regarding intraoperative and postoperative interventions (whether to shunt or not, which type of brain monitoring to use and how to manage the blood pressure). Regardless of the anaesthetic technique, better clinical results can be achieved if standardised protocols and goal-directed strategies are applied by vascular teams that are composed of anaesthesiologists, angiologists and surgeons, in high-volume reference centres.6 Given the current low incidence of perioperative myocardial infarction, stroke and death, future studies should rather focus on endpoints such as prolonged hospital stay as a result of unplanned admission to the ICU, cerebral hyperperfusion syndrome or any other serious complication, and neurocognitive impairment that has a significantly negative impact on healthcare costs and the quality of life.18 Interestingly, administration of dexmedetomidine in elderly patients, but not in patients below 60 years, has been associated with better early neurocognitive performance and fewer delirium or confusional states, in comparison with monitored anaesthetic care or general anesthesia, in various types of surgery including CEA.19,20 This potent and highly selective α2-agonist appears suitable for many ‘awake’ interventions as it decreases central nervous sympathetic outflow, provides analgesia with sedation and anxiolysis without respiratory depression. Changes in vascular anaesthesia practice are hastened by technical advances, the choice of the type of intervention, whether to stent or perform CEA, the personal motivation of the patient and also a comparative risk assessment of the different anaesthesia regimens. To continue our pursuit towards better clinical care, we need more randomised controlled trials in the field of vascular surgery. Acknowledgements relating to this article Assistance with the Commentary: none. Financial support and sponsorship: none. Conflicts of interest: none. Comment from the Editor: this Invited Commentary accompanies a Pro and Con debate. The Commentary was checked and accepted by the editors but was not sent for external peer review.