The Authors Respond

We appreciate the comments made by the reader about the results of our systematic review investigating the association between adverse clinical outcomes after coronary artery bypass graft (CABG) surgery and perioperative blood transfusions. We are grateful for the opportunity to respond to these concerns as they reflect a common misinterpretation of the methods used for our review. We conducted a rigorous review of the literature to determine if there was an association between perioperative blood transfusions and postoperative adverse outcomes. We did not conduct original research. To determine if transfusions caused adverse outcomes would require a randomized controlled trial, which would be unethical given the well-known benefits of blood and volume replacement.We concur that CABG surgery is 1 of the most invasive types of surgical interventions, and bleeding is a relatively common postoperative complication. Blood transfusions have improved hemodynamic indices such as arterial pressure values (mean arterial pressure, systolic and diastolic blood pressure) and made complex surgeries possible. Adverse events, including short- and long-term mortality, which have been explored in our manuscript, are critical patient outcomes and should be carefully considered.Patients with coexisting heart diseases, including coronary artery disease, tolerate acute normovolemic anemia well, and they may even benefit from a restrictive blood transfusion strategy.1 Additionally, alternative strategies to decrease perioperative blood loss and transfusion algorithms should be considered for implementation. Several blood-conservation strategies exist, such as antifibrinolytics, shorter circuit length of the cardiopulmonary bypass, and intraoperative autologous donations.2,3 Specific and considerable attention must be paid to surgical technique and cause of blood loss.Consideration of potential confounding variables is critical to studies of association, such as those included in our systematic review. We evaluated the quality of the studies included in our review and most took confounding variables into account, including those known to be related to adverse patient outcomes, such as risk factors, age, comorbid conditions, demographic characteristics, and clinical characteristics. We acknowledged that studies meeting our inclusion criteria were observational. Furthermore, randomized controlled trials, which are the gold standard, are needed to determine causal links between blood transfusion and adverse outcomes, and they may not be feasible. Blood transfusions have been found to be independent predictors of adverse events in some studies. As we noted, our findings may improve providers’ awareness of risks associated with transfusion in order to better manage anemia and volume replacement postoperatively. Transfusions should not be considered as the default decision when there is clinical uncertainty as to the risk/benefit ratio.4