IJCS | Volume 32, Nº6, November / December 2019

566 Tagliari et al. Blood transfusion in cardiovascular surgery Int J Cardiovasc Sci. 2019;32(6):565-572 Original Article If, in one hand anemia is an independent risk factor for morbidity and mortality by reducing oxygen supply, leading to ischemic injury, 7 on the other hand, the immune response caused by transfusion could be a potential harm factor. 8 However, clinical trials such as TRACS 9 and TITRe 2, 10 which compared restrictive versus (vs) liberal RBC transfusion strategies, have shown non inferiority for a composite endpoint of 30-day all-cause mortality and severe morbidity [cardiogenic shock, acute respiratory distress syndrome or acute renal failure (ARF)] during the hospital stay (10% liberal vs. 11% restrictive), 9 as well as for infectious or ischemic events (35.1% vs. 33.0%). 10 RBC transfusion was an independent risk factor for 30- days clinical complications or death [hazard ratio (HR) for each unit transfused = 1.2; 95% confidence interval (CI) 1.1 – 1.4]. 10 Analyzing long-term results, the recent TRICS trial demonstrated that, in moderate-to-high risk for death patients, a restrictive transfusion strategy (hemoglobin < 7.5 g/dL intra or postoperatively) was non-inferior to a liberal strategy [hemoglobin < 9.5 g/dL in the intensive care unit (ICU) or < 8.5 g/dL in the non-ICU ward] in terms of death, myocardial infarction, stroke or new dialysis in 6-months (17.4% vs. 17.1%; 95% CI 0.87 – 1.18). 11 Choosing between a liberal or a restrictive RBC transfusion strategy has been a major concern and, although clinical trials have supported more restrictive practices, some authors are still attempting to identify an “accurate” hemoglobin threshold for transfusion. 12 In view of the clinical relevance and persistently high transfusion rates, we believe that recognition of modifiable risk factors and adverse events is the first step towards changing our daily practice. Objectives To analyze the incidence of blood transfusion in patients undergoing cardiovascular surgery in a tertiary university hospital in southern Brazil, betweenMay 2015 and February 2017, as well as to analyze adverse events and risk factors associated with the transfusion. Methods Analysis of a prospective cohort of patients submitted to cardiovascular surgery, consecutively enrolled from May 2015 to February 2017. Patients were divided into two groups according to whether or not they received any blood products (RBC, FFP or platelets), and were followed until hospital discharge or up to 30 days after the procedure, in order to evaluate early postoperative adverse outcomes. All patients older than 18 years old undergoing cardiovascular surgeries at Hospital de Clínicas de Porto Alegre , a tertiary university hospital in southern Brazil, were invited to participate in the study. Patients who did not agree to participate and those who did not sign the informed consent form were excluded. The project was approved by the research ethics committee of the Hospital de Clínicas de Porto Alegre (approval number: 15-0332). All procedures were in accordance with the ethical standards for human experimentation and with the 1975 Helsinki Declaration revised in 2008. Mortality and other postoperative outcomes were considered early if they occurred before hospital discharge or up to 30 days after surgical intervention. The outcome “other infections” was considered positive if the patient had superficial (e.g. saphenectomy infection) or deepwound infection (e.g. osteomyelitis ormediastinitis), infective endocarditis, sepsis or bacteremia. The use of anticoagulant or antiplatelet agents was considered recent if the patient received unfractionated heparin or low molecular weight heparin at therapeutic doses in the 24 hours preceding surgery, warfarin or clopidogrel in the last 5 days or non-vitamin K antagonist oral anticoagulants (NOACs) in the last 48 hours. No patient used any other anticoagulant medication. Statistical analysis Data were obtained by clinical interview or review of electronic medical records, stored in a service database and analyzed using the Statistical Package for Social Sciences (SPSS) 18.0 software. Quantitative variables were described as mean (M) and standard deviation (SD) and qualitative variables as absolute number and percentages. Independent samples t-test was performed for continuous variables whereas the chi-square test was used to compare categorical variables. Normality test and non-parametric tests were not performed, since parametric tests are considered robust even for non-normal distributions and skewed data once the sample size is deemed sufficiently large (more than 40 individuals). 13-15