Outcome measures and quality markers for perioperative blood  loss and transfusion in cardiac surgery.
OBJECTIVE
The purpose of this narrative review is to address perioperative bleeding and transfusion as determinants of adverse outcomes after cardiac surgery.


RESULTS
The relationship between postoperative bleeding and adverse outcomes is non-linear, with an increase in the risk of mortality only in cases of severe perioperative bleeding. When perioperative bleeding is used as an outcome variable, it should be dichotomized according to the existing definitions. In retrospective observational studies, red blood cell transfusions have been associated with an increase in morbidity and mortality, which points to restriction of transfusion as a potential benefit. Nevertheless, randomized-controlled trials have not confirmed that restrictive transfusion policies are associated with better outcomes. Additionally, a transfusion policy that is too restrictive may actually increase postoperative mortality in cardiac surgery patients.


CONCLUSIONS
Perioperative bleeding itself is a complex syndrome that can be classified as an outcome measure. Red blood cell transfusion has limitations when considered as an outcome variable and can be biased by many confounders. Its relationship with clinical outcome remains uncertain. In addition to being potential outcome measures, transfusion rates and the number of allogeneic blood products transfused may also be considered as quality-of-care markers.
Marco
M
Ranucci
D015982:Bias; D016063:Blood Loss, Surgical; D001803:Blood Transfusion / Q000379:methods; D006348:Cardiac Surgical Procedures / Q000009:adverse effects / Q000379:methods* / Q000592:standards; D017707:Erythrocyte Transfusion / Q000379:methods; D006801:Humans; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011787:Quality of Health Care; D016032:Randomized Controlled Trials as Topic; D065227:Transfusion Reaction