Discussion
Blood transfusions and re-exploration carry substantial risk for postoperative morbidity and mortality and should be used prudently.2-8,12,13 In a study of over 18,000 patients at Cleveland Clinic from 2000 to 2010, Vivacqua et al noted that transfusion and reoperation for bleeding were independently associated with increased risk of mortality and morbidity, respectively (8.5% vs 1.8%).8 Mehta and colleagues noted a risk-adjusted mortality of 5.9% for bleeding post CABG in patients who required re-exploration compared to 2.0% for others.4 Ranucci et al showed higher mortality (14.2% vs 3.4%; p = .001) and greater morbidity in patients requiring surgical re-exploration compared to patients who did not.5 In addition, the amount of packed red blood cells was associated with significantly increased morbidity and mortality (0.25% increase for each unit transfused). In a study that included almost 5400 patients, Frojd et al noted a twofold increase in early postoperative mortality and an increase in risk of mortality beyond 90 days in patients requiring re-exploration for bleeding.3 In an international prospective study of patients undergoing urgent CABG with acute coronary syndrome on antithrombotic agents, Stone et al noted that patients receiving > 4 units of packed red blood cells was an independent risk factor for mortality for up to 1 year after CABG.6Freeland and colleagues14 noted that blood transfusion is an independent predictor of acute kidney injury in cardiac surgical patients. Several studies have linked transfusions to potentially lethal complications, including infection and lung damage.15-18
The landmark paper in 1979 by Cosgrove and colleagues19 showed that blood transfusions during myocardial revascularization could be reduced to 6%. In his 2015 commentary, Svensson noted several important factors for achieving low prevalence of transfusions, including tolerating lower hematocrits on-pump and use of cell saver, among others.20 He pointed out, however, that over time there has been an increase in transfusions, perhaps attributable to greater use of anticoagulant and antiplatelet agents and reduced concern regarding transfusion-related infections.
Although the Society of Thoracic Surgery established guidelines in 200710 and 201111 for blood transfusions, prevalence of transfusions in patients undergoing CABG increased from 12% in 1999 to 32% in 20101 and is likely associated with older age, increased comorbidities, and the complexity and multiple component aspect of surgical procedures. Nevertheless, only a small percentage of team members, including perfusionists, anesthesiologists, and even surgeons, reported reading the guidelines, implementing them, or altering practice habits.1,21
Cost effectiveness and value-based medicine have become a cornerstone of our health care system. Cardiac surgery accounts for a noteworthy proportion of the 14 million annual RBCs transfused in the United States.9,22 Shanders et al noted the cost of transfusions to be US $1,158 per unit (2007 value) when indirect overhead and acquisition costs are included, and even higher when transfusion-related complications are considered.23 In addition, the postoperative length of stay in the current study, was significantly reduced to 4.5 days in the blood restricted group, adding further cost savings as suggested and corroborated by others.24,25
The lack of adherence to conservation measures may be because of the assumption that restricting red blood cell use could be detrimental and undermine patient safety. This is contrary to the findings of several studies demonstrating the use of blood conservation techniques without adverse consequences.26-28 Magruder and colleagues29 noted significant variation in blood transfusion practices even after risk adjustment, suggesting that transfusion practices may be physician- rather than patient-driven.
Blood transfusions can be lifesaving and are more likely needed in patients at higher risk of blood loss, such as those undergoing reoperations, complex aortic, or valvular surgeries. As stated in the Introduction, the reported prevalence of transfusions for primary CABG is more than 32%, and the objective of this study was to concentrate on the subset of patients in whom transfusion reduction could be accomplished safely. A significant reduction in blood use for isolated primary CABG following implementation of perioperative conservation guidelines was observed, with no negative impact on patient safety or outcome. Transfusions decreased intraoperatively and postoperatively, resulting in a statistically significant decline in overall prevalence of transfusions and postoperative length of stay.
These findings can likely be extended to other surgeries as well. Yaffee and colleagues assessed a conservation strategy for aortic valve replacement, emphasizing permissive anemia and minimization of hemodilution (also through use of autologous priming and vasopressors).30 They found a 14.9% decrease (82.9% to 68.0%) in the number of patients transfused with RBCs, as well as a 54.4% reduction in overall mean blood product transfusions, with no increase in mortality or major complications.30