Safety of anaesthesia techniques in patients undergoing carotid endarterectomy: a systematic review with meta-analysis of randomised clinical trials

Each year, approximately 3000–3500 patients undergo carotid endarterectomy in the UK, and over 150,000 worldwide [1, 2]. It is thought that the selection of anaesthetic method – whether cervical plexus block, general anaesthesia or a mix of both – can impact haemodynamic parameters differently and the oxygenation and perfusion of the brain and heart. This variability may have an impact on the risk of stroke, myocardial infarction and mortality [3]. We conducted a systematic review to compare the safety and clinical outcomes of different anaesthetic techniques in patients undergoing carotid endarterectomy.

This analysis was based on data from a systematic review, the protocol of which was registered prospectively. We included randomised clinical trials that enrolled patients aged ≥ 18 y undergoing carotid endarterectomy. The studies included comparisons between any two anaesthesia techniques (general, local/regional, combined regional and general). Our primary outcomes were stroke and myocardial infarction within 30 days of surgery. We also included studies reporting data on death within 30 days; postoperative pain within 24 h; arteries shunted; postoperative haematoma; time course of arterial occlusion; patient satisfaction; surgeon satisfaction; postoperative cognitive dysfunction; duration of surgery, ICU stay and hospital stay; need for reintervention; cranial nerve injury; respiratory complications; quality of life one month after surgery; and haemodynamic parameters. Screening and data collection were conducted in duplicate by independent reviewers. We assessed risk of bias in individual studies using the Risk of Bias 2 tool and judged the certainty of evidence according to GRADE recommendations (online Supporting Information Figure S1).

We categorised the interventions into four groups for the Bayesian network meta-analyses: epidural; regional (i.e. cervical plexus block and/or local infiltration); general; and combined regional and general anaesthesia. We also performed Bayesian pairwise meta-analyses comparing regional with general anaesthesia. Overall, 24 studies encompassing 5341 patients were included in the analyses.

We did not find any significant differences between the interventions for the primary outcomes of stroke and myocardial infarction within 30 days of surgery (Table 1 and Fig. 1). However, there was significantly less use of an arterial shunt with regional compared with general anaesthesia (relative risk (95% credible interval) 0.33 (0.17–0.66), Table 1). No significant differences were found for the remaining outcomes.

Our study did not yield results to inform decision-making regarding choice of anaesthetic technique for carotid endarterectomy. No significant differences were observed for most outcomes. However, readers should not interpret these findings as evidence of equivalence as they may reflect insufficient data.

While our findings show reduced use of arterial shunt with the use of regional anaesthesia, there is a possibility that this result is due to chance, given the number of analyses performed. Applying a Bonferroni correction would render this significant difference non-significant. Our results also indicate that regional anaesthesia may reduce mortality within 30 days of surgery (Table 1 and Fig. 1). However, it is important to emphasise that this was not statistically significant, the certainty of evidence is very low, and this finding should not be used to inform clinical practice.

Other researchers have summarised data from randomised trials and observational studies [3-5]. While observational data suggest improved outcomes with regional anaesthesia [3, 5], including a reduced incidence of stroke, myocardial infarction and death, these results were not confirmed by a previous summary of randomised studies [4], and not by our updated analysis.

While regional anaesthesia may improve outcomes by blocking nociceptive pathways and increasing cerebral blood flow, it is also possible that uncovered nerve fibres or inadequate sedation might lead to tachycardia and hypertension, increasing the risk of myocardial ischaemia in this high-risk cohort of patients. This adds complexity, as different techniques may affect key outcomes like stroke and myocardial infarction differently. Future research might consider evaluating composite or more critical outcomes, such as mortality.

Although our findings do not provide strong evidence to inform clinical decision-making, they do suggest a potential difference between anaesthetic techniques in relation to important outcomes such as the need for arterial shunt and mortality. These findings are consistent with observational data and may be associated with the incidence of stroke and myocardial infarction [3, 5]. As such, our results underscore the need for further research to determine whether any specific technique or combination of techniques may improve patient outcomes.

In conclusion, the current evidence does not provide robust support for the selection of any specific anaesthetic technique for carotid endarterectomy. We did not observe significant differences for most outcomes, and the one observed difference may be attributable to chance.