Preoperative Anemia and Outcomes in Cardiovascular Surgery: Systematic Review and Meta-Analysis

Background. Preoperative anemia is common in patients scheduled for cardiac surgery. However, its effect on postoperative outcomes remains controversial. This meta-analysis aimed to clarify the impact of anemia on outcomes after cardiac surgery. Methods. A literature search was conducted on MEDLINE, Embase, Cochrane, and Web of Science databases. The primary outcome was 30-day postoperative or inhospital mortality. Secondary outcomes included acute kidney injury, stroke, blood transfusion, and infection. A meta-analytic model was used to determine the differences in the above postoperative outcomes between anemic and nonanemic patients. Results. Of 1103 studies screened, 22 met the inclusion criteria. Of 114,277 patients, 23,624 (20.6%) were anemic. Anemia was associated with increased mortality (odds ratio [OR], 2.74; 95% confidence interval [CI], 2.32-3.24; I-2 = 69.6%; P <.001), acute kidney injury (OR, 3.13; 95% CI, 2.37-4.12; I-2 = 71.1%; P <.001), stroke (OR, 1.46; 95% CI, 1.24-1.72; I-2 = 21.6%; P <.001), and infection (OR, 2.65; 95% CI, 1.98-3.55; I-2 = 46.7%; P <.001). More anemic patients were transfused than nonanemic patients (33.3% vs 11.9%, respectively). No statistically significant association was found between mortality and blood transfusion (OR, 1.35; 95% CI, 0.92-1.98; I-2 = 83.7%; P = .12), but we were not able to compare mortality with or without transfusion in those who were or were not anemic. Conclusions. Preoperative anemia is associated with adverse outcomes after cardiac surgery. These findings support the addition of preoperative anemia to future risk prediction models and as a target for risk modification. (C) 2019 by The Society of Thoracic Surgeons