Preoperative anemia and postoperative thirty-day mortality in patients undergoing non-cardiac surgery: a secondary analysis based on a single-center retrospective study.

Abstract

Introduction There is controversial and limited evidence to clarify the specific relationship between anemia and perioperative mortality in surgical patients at different ages. We aimed to investigate the relationship between them in patients undergoing non-cardiac surgery of different ages. Methods The present study was a retrospective analysis of the electronic medical records of 90,785 patients who underwent general surgery at the Singapore General Hospital from January 1, 2012 to October 31, 2016. We reanalyzed these data including patient demographics, comorbidities, laboratory results, surgical priority and surgical risk. The main outcome measures included anemia and postoperative 30day mortality. Results The average age of the 86,748 participants enrolled was 52.73 ± 17.24 years old, of which approximately 54.05% were female. 62878 (72.48%)people in the study population had no anemia, 13006 (14.99%) had mild anemia, 10863 (12.52%) had moderate to severe anemia. Multivariate logistic regression analysis showed that anemia was independently associated with postoperative 30day mortality [Compared with none anemia, adjusted odds ratio of mild anemia:1.6404, (95% confidence interval [CI]: 1.2295-2.1886; P =0.000768); and adjusted OR of moderate or severe anemia: 2.6643 (95% [CI]: 2.0315- 3.4941) ;P<0.000001)]. There is no statistical difference among the effect sizes of anemia on 30day mortality, regardless of different age(P=0.2469), gender(p=0.8067), and race (0.4629). And the effect sizes of anemia at each stage on postoperative 30day mortality showed statistically significant increase in intra-transfusion, emergency surgery, high surgery risk(p for interaction is 0.0125,0.0001,0.0032,respectively) Discussion In patients undergoing non-cardiac surgery, anemia is an independent risk factor for perioperative 30day mortality, especially among emergency surgery, high-risk surgery and surgery with intraoperative blood transfusion.