Strengths and limitations
The results of this network meta-analysis must be interpreted in light of its limitations. Several important limitations arise from the use of observational studies in a meta-analysis. The presence of unmeasured confounders and possible treatment allocation bias cannot be excluded. Ideally, a network meta-analysis is performed solely with the inclusion of randomized populations to guarantee that the relative treatment effects deriving from the network analysis remain unbiased21. However, the randomized evidence regarding the topic of hypothermic strategies in aortic arch surgery is scarce, leading to a relatively large amount of non-randomized studies in our network meta-analysis. Hence, incorporating both types of data allows assessments of larger sample sizes and multiple treatments simultaneously. Furthermore, there may be variability in surgeon and center expertise, technical variabilities and postoperative protocols. Additionally, heterogeneity may arise due to different definitions for stroke and postoperative AKI.