Is There an Optimal Perioperative Hemoglobin?

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Blood transfusions remain the most common procedure performed in hospitals in the United States. With recent trial evidence supporting the use of restrictive transfusion thresholds and the rise of patient blood management programs, however, red blood cell transfusion rates have been declining since 2008. Approximately 10.7 million units of red blood cells were transfused in the United States in 2017. It is estimated that 30% to 40% of all inpatient stays requiring blood transfusions are associated with major or minor surgical procedures. ^, Surgical patients are frequently anemic from the underlying disease, from the injury leading to the need for surgery, and/or from the blood loss associated with the surgical procedure.

Over the past 35 years, there has been a trend toward using lower hemoglobin concentration as a transfusion trigger. The main motivation has been concern about blood safety prompted by the human immunodeficiency virus (HIV) epidemic in the 1980s. Fortunately, the risks of transmitting viral infections have become extremely low. The most recent estimates of the risk for residual units of infected blood donated were 1 per 2,600,000 for hepatitis C virus, 1 per 1,529,000 for hepatitis B virus, and 1 per 2,300,000 for HIV. On the other hand, noninfectious risks, such as transfusion-related acute lung injury (TRALI) and transfusion-associated circulatory overload (TACO), may be even more common than previously appreciated, especially in critically ill patients. ^,

With the improvement in safety and recently published clinical trials, it is time to evaluate the evidence on when blood transfusion should be administered in the perioperative time period.

OPTIONS/THERAPIES

Most recommendations suggest that the decision to transfuse should be based on individual assessment of signs and symptoms of anemia. In practice, however, most clinicians transfuse at a specific hemoglobin concentration, such as 8 g/dL. The therapeutic options for red blood cell transfusions include either blood bank–directed allogeneic or predeposit autologous sources. Advances in blood conservation surgical techniques and the safety of the current US blood supply, as previously noted, have led to the continued decline in the use of predeposit autologous blood. Autologous blood donations represented only 0.08% of all red blood cell units collected in 2017. Furthermore, the use of predeposit autologous transfusion is generally not recommended because it does not reduce overall exposure to transfusion.

EVIDENCE

Several critical lines of evidence are needed to guide transfusion decisions. First, it is necessary to understand the risks associated with different levels of anemia in the perioperative time period. Second, randomized clinical trials are needed to document that transfusion improves outcome. Third, as previously described, the risks of allogeneic and autologous transfusion must also be taken into account. The current data suggest that allogeneic blood transfusion is extremely safe. ^, To determine the efficacy of transfusion, we need to know at what point the risks for anemia increase and whether transfusions can eliminate or reduce the risks.