Risks associated with blood transfusion

Although transfusion of donated blood can be life saving, it is a procedure associated with considerable potential risk to the recipient patient. As with any medical treatment or procedure the decision to prescribe donated blood must be made after assessment of the balance between benefit and risk for that particular patient. 

In the case of the rapidly exsanguinating patient the decision is not difficult; benefit clearly outweighs risk. In most other cases the risks must be considered. In the past a major concern was the risk of transmitting viral infection (most notably the viruses that cause hepatitis and AIDS), but that risk has been largely eliminated by rigorous donor selection and improvements in testing of donated blood for the presence of viruses. 

With virtual elimination of the risk of viral transmission, the non-infectious risks of transfusion are now the major concern. In a recently published review the authors identify and discuss the many non-infectious hazards of transfusion. Eighteen separate hazards are identified under two headings: the immune-mediated and the non-immune-mediated. 

The immune-mediated reactions discussed include the familiar, such as hemolytic reaction, allergic reaction and transfusion-related lung injury (TRALI) along with the less familiar, posttransfusion purpura (PTP), transfusion-associated graft versus host disease (TA-GVD) and microchimerism. 

The non-immune-mediated hazards discussed include septic reaction caused by transfusion of bacterially contaminated blood, metabolic disturbances, e.g. hyperkalemia and disturbances of blood coagulation that can occur following massive red-cell transfusion. Consideration is given to controversial topics of transfusion medicine such as the significance of the so-called red-cell storage lesion and less clearly defined hazards such as transfusion-related immunomodulation.

This broad overview is complemented by a second review article in the same journal issue that focuses on a single non-infectious hazard of transfusion, transfusion-related acute lung injury (TRALI), which in recent years has emerged as the leading cause of transfusion-related morbidity and mortality. 

This review is directed at clinicians and includes clinical features used to make a diagnosis of TRALI along with consideration of the clinical management of patients suffering TRALI. There is also extensive discussion of current knowledge of the pathophysiology of TRALI. Taken together these two review articles and the 169 cited references provide a considerable resource for students of transfusion medicine, whether based in the ward or the laboratory.