Date	Event	Description
20 May 2014	New citation required but conclusions have not changed	We found eight new studies. After we assessed the full articles for eligibility criteria, we included two studies in our updated review (Severgnini 2013; Weingarten 2010). These two studies are randomized clinical trials. Severgnini 2013 assessed the effectiveness of protective mechanical ventilation during open abdominal surgery. Weingarten 2010 compared two ventilatory strategies in elderly study participants undergoing major abdominal surgery. These studies focused on assessment of intraoperative outcomes, and they did not assess most of the outcomes listed in this review. The conclusions were not changed.
20 May 2014	New search has been performed	The previous review authors (Imberger 2010) decided not to update the review. Three new review authors updated this version: Fabiano T Barbosa, Aldemar A Castro and Célio F Sousa‐Rodrigues. We reran the searches until October 2013. We updated the methods section. We included selective reporting in the risk of bias table. Bias related to blinding of participants and personnel was assessed separately from bias related to blinding of outcome assessment.