Many studies have shown an association between transfusion and adverse events, including short- and long-term mortality, in cardiac surgery. In this study, the authors aimed to investigate this association in patients undergoing isolated coronary artery bypass graft surgery (CABG) or combined CABG and aortic valve replacement (AVR). They found that intraoperative red blood cell (RBC) transfusion was associated with a more than three-fold increased risk for mortality. The study is a retrospective observational investigation based on data collected from June 2011 to September 2014, in which the authors performed a propensity score (PS) as single confounder to estimate the odds ratio for mortality among patients receiving intraoperative RBC transfusion. In this way they represented the likelihood of receiving RBC transfusion based on pre- and intraoperative characteristics.
According to the protocol applied, the trigger for intraoperative RBC transfusion was a haematocrit <20% during CPB or <25% after separation from CPB. Two main factors are involved in the intraoperative decrease of haemoglobin (Hb): low value of preoperative haemoglobin and haemodilution due to the priming fluid volume. Recent consensus statements and guidelines support preoperative anaemia treatment as the solution to reduce transfusions and perioperative Hb drop and to minimise the need to apply restrictive transfusion criteria that may not be well tolerated by cardiopathic patients. About haemodilution, the authors mention two options for cardiopulmonary bypass (CPB): a miniaturized extracorporeal circulation (MECC) or a conventional extracorporeal circulation (ECC) according to the preference of the surgeon and type of procedure. They did not consider the different characteristics of these two types of circuits and their impaact on haemodilution. An accurate analysis of the results obtained with these two types of CPB might suggest more indications about their utilisation in the future. In addition, tranexamic acid administration is widely used during cardiac surgery to reduce bleeding, blood product transfusions and reoperations caused by bleeding. I would recommend a well-defined standard protocol in the same way as intraoperative cell salvage was done.
– Marco Pavesi