Although the stated objectives of the review referred to both safety and efficacy, in practice the focus was restricted to perioperative safety. The inclusion criteria were clear in most respects (although an "acceptable" procedure was not defined), but the search was limited. Only two databases were searched (one of which is restricted to RCTs). Journals searched were not named. No attempt was made to find unpublished articles. Some studies may have been missed and the review was prone to publication bias.
Steps were taken to minimise the risk of bias and error in study selection by having more than one reviewer make decisions independently, but it was not clear whether this also applied to data extraction. Few details were provided about the clinical or methodological characteristics of the included studies (for example, participant age, study design, follow up period). It did not appear that study validity was assessed. These factors made it difficult to evaluate the reliability of the findings reported.
The decision to combine the studies in narrative synthesis appears appropriate, but the use of procedures rather than participants as the unit of analysis increases difficulty in interpreting the results. Moreover, the results of prospective studies were not given prominence over retrospective studies. The limitations of the evidence were acknowledged in the text, including the lack of direct comparison of the interventions of interest, the poor design of primary studies and the potential for selection bias and publication bias. In view of the lack of properly controlled evidence and the methodological limitations of the review, in particular the limited search and lack of validity assessment, the conclusions did not appear reliable.