Department of Gastroenterology, Heart & Lung Centre, Wolverhampton, WV10 0QP United Kingdom. Electronic address: firstname.lastname@example.org. Department of Gastroenterology, Heart & Lung Centre, Wolverhampton, WV10 0QP United Kingdom. Department of Shrewsbury Health Library, Royal Shrewsbury Hospital, Shrewsbury, SY3 8XQ United Kingdom. Department of Cardiothoracic Anaesthesiology, Heart & Lung Centre, Wolverhampton, WV10 0QP United Kingdom. Department of Cardiothoracic Surgery Department, Heart Centre, American Hospital Dubai, Oud Metha, Dubai, United Arab Emirates.
BACKGROUND Pre-operative 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 following 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 in-hospital mortality. Secondary outcomes included
acute kidney injury (AKI), stroke, blood transfusion, and infection. A meta-analytic model was used to determine the differences in the above postoperative outcomes between anemic and non-anemic patients. RESULTS Out of 1103 studies screened, 22 met the inclusion criteria. A total of 23624 (20.6%) out of 114277 patients 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<0001), AKI (OR 3.13, 95% CI 2.37-4.12; I(2)=71.1%; p<0001), stroke (OR 1.46, 95% CI 1.24-1.72; I(2)=21.6%; p<0001), and infection (OR 2.65, 95% CI 1.98-3.55; I(2)=46.7%; p<0001). More anemic patients were transfused than non-anemic (33.3 versus 11.9%). 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=0.12) 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 following cardiac surgery. These findings support the addition of preoperative anemia to future risk prediction models, and as a target for risk modification.