ObjectivesTo systematically review the risk factors of postoperative hypoxemia in patients undergoing coronary artery bypass grafting.MethodsPubMed, EBCO, The Cochrane Library, CNKI, VIP and WanFang Data databases were electronically searched to collect case-control studies and cohort studies on the risk factors of postoperative hypoxemia in patients undergoing coronary artery bypass grafting from inception to December 2018. Two reviewers independently screened literature, extracted data and assessed risk of bias of included studies, then, meta-analysis was performed by using RevMan 5.3 software.ResultsA total of 20 articles were included, including 3 926 patients. The results of meta-analysis showed that: age (OR=2.94, 95%CI 0.81 to 5.07, P=0.007), body mass index (OR=1.94, 95%CI 0.77 to 3.12, P=0.001), smoking (OR=2.72, 95%CI 1.68 to 4.42, P<0.000 1), diabetes history (OR=1.63, 95%CI 1.37 to 1.93, P<0.000 01), preoperative lung diseases (OR=4.11, 95%CI 1.64 to 10.28, P=0.003), complicated ventricular aneurysm (OR=1.57, 95%CI 1.12 to 2.21, P=0.01), left ventricular end-diastolic diameter (OR=1.28, 95%CI 0.12 to 2.44, P=0.03), aortic occlusion time (OR=13.25, 95%CI 4.93 to 21.57, P=0.002), operation time (OR=9.33, 95%CI 5.36 to 13.30, P<0.000 01), number of bypass branches (OR=0.19, 95%CI 0.02 to 0.36, P=0.03), intraoperative infusion volume (OR=383.46, 95%CI 282.16 to 484.76, P<0.000 01) and postoperative pulmonary infection (OR=6.00, 95%CI 3.83 to 9.42, P<0.000 01) were the risk factors for postoperative hypoxemia in patients undergoing coronary artery bypass grafting. Preoperative ejection fraction (OR=−2.60, 95%CI −4.56 to −0.64, P=0.009) and preoperative partial oxygen pressure (OR=−3.14, 95%CI −4.72 to −1.56, P=0.000 1) were the protective factors for postoperative hypoxemia.ConclusionsCurrent evidence shows that age, body mass index, smoking, diabetes history, preoperative lung diseases, complicated ventricular aneurysm, left ventricular end-diastolic diameter, aortic occlusion time, operation time, number of bypass branches, intraoperative infusion volume and postoperative pulmonary infection are risk factors for postoperative hypoxemia in patients undergoing coronary artery bypass grafting. Due to limited quality and quantity of included studies, the above conclusion is required to be assessed by further studies.