“…Data regarding postoperative mean ABG ( Fig. 4) were available for 20 included studies (6 prospective studies 19,22,23,26,28,29 and 14 retrospective studies 32,34,39,[41][42][43][44][45][46][47]49,[52][53][54] ). Because there were two prospective studies with a low risk of bias, we did not perform the meta-analysis in this subset.…”