The Silent Risks of Blood Transfusion
Recent studies have challenged the universal benefit of blood transfusions, which are now linked to organ dysfunction, immunosuppression, and survival in various clinical situations. Rawn discusses some of the newer findings that raise questions about the risks and benefits of blood transfusions. The historical risks of transfusions, infection transmission and ABO mismatch hemolytic reactions, have decreased but have not disappeared. Transfusion-related acute lung injury (TRALI) is a more recently recognized complication of transfusions. The 1999 Transfusion Requirements in Critical Care study found that patients with a hemoglobin level of <10 g/dL had more cardiac and pulmonary complications and increased mortality compared with those with a hemoglobin of <7 g/dL. Retrospective analyses have found that the number of blood transfusions is associated with length of stay, mortality, and an increased incidence of infection. Two recent studies have also associated transfusions with vulnerability to malignancy. One study determined that transfusions within 5-29 years before the initial cancer diagnosis had a 26% increase in the risk of patients developing non-Hodgkin’s lymphoma; the other found that patients given blood during hepatocellular carcinoma resection had a 5-year cancer-related survival rate of 38% versus 67% in those not receiving blood. Studies in patients undergoing cardiac surgery found that RBC transfusion is associated with an increase in infectious complications, myocardial infarction (MI), stroke, renal failure, prolonged ventilation, atrial fibrillation, hospital length of stay, and mortality. In patients with acute coronary syndromes and MI, transfusions have been associated with increased survival but also an increase in pulmonary edema and multiorgan system dysfunction; other studies showed an increased risk of MI and death. Anemia has been associated with adverse outcomes in many conditions and can predict adverse outcomes. Using current transfusion guidelines, attempts to correct anemia by transfusions is either not beneficial or is actually harmful to the patient. One study showed that the ischemic complications were not decreased by blood transfusion regardless of the patient’s nadir hemoglobin value or comorbidities. One contributing possibility is storage defects in the transfused blood; a study showed that patients receiving blood stored >2 weeks had a significant increase in hospital mortality, prolonged intubation, renal failure, and sepsis or septicemia. The Society of Thoracic Surgeons and the Society of Cardiovascular Anesthesiologists have developed guidelines indicating that the current evidence is not an adequate guide to making decisions about transfusions; they recommend a “trigger” of a hemoglobin level < 7 g/dL in postoperative cardiac surgery patients. As evidence of harm from transfusion continues to be published, restrictive transfusion strategies should be emphasized and implemented.
