Is local anaesthesia superior to general anaesthesia in endovascular repair of abdominal aortic aneurysm? Free

Summary

A best evidence topic in cardiovascular surgery was written in accordance to a structured protocol. The question addressed was: in patients undergoing endovascular repair of abdominal aortic aneurysm (EVAR), is local anaesthetic (LA) superior to general anaesthetic in terms of perioperative outcomes? Altogether, 630 publications were found using the reported search protocol, of which 3 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type and primary outcomes were tabulated. The 3 included studies are systematic reviews with meta-analyses, with no randomized trials identified. Within the studies, there is a degree of heterogeneity in terms of surgical case-mix (elective or emergency EVAR or both) and anaesthetic technique (LA, regional anaesthetic, local-regional anaesthetic and general anaesthetic). With 1 study not providing pooled estimates, the second study demonstrated statistical significance in favour of local-regional anaesthetic within the elective setting in terms of mortality [pooled odds ratio (OR) 0.70, 95% confidence interval (CI) 0.52–0.95; P = 0.02], morbidity (pooled OR 0.73, 95% CI 0.55–0.96; P = 0.0006) and total length of hospital admission (pooled mean difference: −1.53, 95% CI −2.53 to −0.53; P = 0.00001). The third study failed to demonstrate a statistically significant mortality benefit with LA (pooled OR 0.54, 95% CI 0.21–1.41; P = 0.211). While the results of these studies fail to provide a clear answer to a complex surgical problem, it would be appropriate, in the light of current evidence, to recommend LA as non-inferior to general anaesthetic in both emergency and elective settings.

INTRODUCTION

A best evidence topic was constructed according to a structured protocol as fully described in ICVTS [1].

THREE-PART QUESTION

In [patients undergoing endovascular repair of abdominal aortic aneurysm], is [local anaesthetic] superior [to general anaesthetic] in terms of [peri-operative outcomes]?

CLINICAL SCENARIO

One of your colleagues is presenting the results of a case-series review conducted at your surgical unit. In patients undergoing endovascular stenting of aortic aneurysmal disease of the abdomen (EVAR), general anaesthetic (GA) was used in 100% of emergency cases. You are surprised to hear that local anaesthetic (LA) was used in only 7% of elective endovascular repairs of aortic aneurysm. You recall some recent studies showing favourable outcomes in using local anaesthesia in both the elective and emergency settings for EVAR. You decide to conduct a review of the literature and present the findings to a group of your surgical and anaesthetic colleagues.

SEARCH STRATEGY

A literature search of Medline (inception—January 2019) was performed through the PubMed interface, using the terms [general OR GA OR local OR LA] AND [elective OR emergency] AND [abdominal aortic aneurysm OR AAA] AND [endovascular stenting OR EVAR OR percutaneous OR minimally invasive].

SEARCH OUTCOME

A total of 630 publications were yielded from the search strategy. Of these, 3 papers were identified as representing the best available evidence to answer the clinical question. The primary outcomes of these studies are presented in Table 1.

RESULTS

Three systematic reviews representing the best available evidence were ultimately included within this review [2–4].

The first of the 3 studies, as reported by Armstrong et al. [2], included 26 526 participants across 21 studies, comparing GA to LA or regional anaesthetic (RA) or both. Participants were analysed based on the surgical context: elective EVAR only (14 studies, n = 9372), emergency EVAR only (4 studies, n = 3365) and elective and emergency EVAR or not specified (3 studies, n = 13 789). The primary outcome was overall 30-day or in-hospital mortality. Due to the serious risk of bias introduced by the included studies, all of which were reported as level 2-, as per the Scottish Intercollegiate Guidelines Network (SIGN) grading system [5], pooled estimates were not included within the quantitative analysis. In the elective setting, the mortality relative risk (RR) between LA cohorts and GA cohorts were <1.0 in six of the 7 reporting studies (mortality RR 0.08, 0.16, 0.37, 0.62, 0.89, 0.98, 1.53); however, the 95% confidence interval (CI) in all traversed 1.0, with all studies failing to achieve statistical significance. When comparing RA with GA in the elective setting, all 6 studies reporting the RR of mortality demonstrated favourability of RA (mortality RR 0.17–0.65); however, the 95% CI traverses 1.0 in all. Of the 5 studies reporting RR of mortality between LA and RA within the elective setting, two of the studies favoured LA (mortality RR 0.57, 0.63), and 3 studies favoured RA (mortality RR 1.15, 1.52, 3.91), with the 95% CI spanning 1.0 in all 5 studies. A more convincing relationship is demonstrated in the emergency EVAR analysis, in which all four of the studies reporting RR of mortality, demonstrated superiority in favour of LA compared with GA (mortality RR 0.40, 0.42, 0.66, 0.68), of which 3 had a corresponding 95% CI <1.0, demonstrating statistical significance.

The second of the 3 studies, as reported by Hajibandeh et al. [3], included 15  472 patients across 14 studies investigating anaesthesia within the elective setting, and compared LA, RA, local regional anaesthetic (LRA) to GA. A total of 10 489 patients underwent EVAR under GA, 3396 patients had EVAR under RA, and 1439 patients underwent the procedure under LA. All studies provided comparative data on perioperative mortality and morbidity with LRA versus GA, with 4 studies providing length of stay comparisons between LA and GA. Overall 30-day or in-hospital mortality was reported in terms of an odds ratio (OR). Of the 11 studies providing data on mortality, 10 demonstrated favourability of LRA compared with GA (mortality RR 0.06–1.50), of which 1 study had a corresponding 95% CI <1.0. The pooled mortality analysis demonstrated statistical significance in favour of LRA compared with GA (mortality OR 0.70, 95% CI 0.52–0.95; P = 0.02). Postoperative morbid cases occurred less frequently in LRA than in GA, with pooled OR demonstrating statistical significance (OR 0.73, 95% CI 0.55–0.96; P = 0.0006). The total length of stay was found to be statistically significantly lower in patients receiving LA than those of GA, with a pooled mean difference of 1.53 days (95% CI 2.53–00.53; P = 0.00001). This study concludes that local and/or RA is advantageous over GA in elective EVAR, as indicated by reduced perioperative mortality and morbidity.

The third systematic review and meta-analysis, as reported by Karthikesalingam et al. [4], included 13 459 patients across 10 studies. Of importance, this study failed to describe the surgical context of the case-mix; therefore, it should be assumed that this study includes participants undergoing both emergency and elective procedures; the proportion of each is unknown. LA was found to be more favourable than GA across all five of the primary outcomes: 30-day mortality, incidence of endoleak, operating time, fluid requirements and the requirement for transfusions. The pooled OR for 30-day mortality, whilst favouring LA, did not demonstrate statistical significance (OR 0.7, 95% CI 0.39–1.26; P = 0.235). Similarly, both the endoleak rate and requirement for blood transfusion, whilst favouring LA, showed no statistical significance (endoleak pooled OR 0.54, 95% CI 0.21–1.41; P = 0.211 and blood transfusion pooled OR 0.6, 95% CI 0.26–1.37; P = 0.226). The operating time and fluid requirements were found to be statistically significant in favour of LA, reported in terms of weighted-mean difference (weighted-mean difference operating time −0.54 h, 95% CI −0.87 to −0.22; P = 0.001, weighted-mean difference fluid requirement −0.47 l, 95% CI 0.89 to −0.06; P = 0.026). The presence of considerable selection bias is recognized as the main limitation of this review, preventing inference of causality. This study also demonstrates that patients undergoing LA/RA are older, have a higher ASA grade, and carry an increased burden of cardiopulmonary disease, compared with GA cohorts.

It is clear that within both the elective and emergency setting, general anaesthesia for EVAR is utilized more frequently than LA [2–4]. It is well-recognized that the burden of mortality associated with emergency EVAR is very high, found to be 16–25.2% within studies included within this review, which is much greater than the 0.8–1.8% for elective EVAR [2–4]. It should be noted that even a small reduction in perioperative mortality in emergency cases has the potential for significant improvements, therefore LA appears to represent an exciting medium for this. Within the 3 systematic reviews included, there is evidence that mode of anaesthesia impacts on postoperative outcomes. While it is important to consider the limitations of the literature-base in that no randomized trial data is available on this topic, a number of conclusions can be drawn and should be considered up-to-date, in that two of the included studies within this review include literature searches up-until 2018. First, there appears to be a mortality benefit in adopting LA in both the emergency and elective settings, with the effect-size greater in the former. With 1 study not providing pooled estimates, Hajibandeh et al. demonstrated statistical significance in favour of LRA within the elective setting in terms of mortality, morbidity and total length of hospital admission. Karthikesalingam et al. whilst not specifying the surgical context, failed to demonstrate a statistically significant mortality benefit with LA. While the results of these studies fail to provide a clear answer to a complex surgical problem, it would be appropriate, in light of current evidence, to recommend LA as non-inferior to GA in both emergency and elective settings. As per recommendation 67 of the European Society of Vascular Surgery 2019 guidelines, ‘local anaesthesia should be considered as the anaesthetic modality of choice for endovascular repair of ruptured abdominal aortic aneurysm whenever tolerated by the patient’ [6].

CLINICAL BOTTOM LINE

The current evidence suggests that LA is effective and safe in both the elective and emergency EVAR settings; therefore, its use in selected patients should be encouraged. Importantly, a randomized trial, which is currently lacking, is required to confirm or dispute these conclusions.

Conflict of interest: All authors declare no conflict of interest.

REFERENCES