A complete discussion of transfusion reactions is beyond the scope of this manual. The incidence of infection through a blood transfusion has been greatly reduced, given the improvements in donor screening and processing techniques. The most significant infectious risk of transfusions is due to bacterially contaminated platelets. Platelets must be stored at room temperature and on an average 1 in 3,000 bags are contaminated with bacteria proven by culture. The risk of an infection through a platelet transfusion is approximately 1 in 20,000.

TRANSFUSION-RELATED ACUTE LUNG INJURY

Mechanism

The risk of transfusion-related acute lung injury (TRALI) is estimated at 1 case per 5,000 transfusions. It is characterized by acute onset of hypoxemia and the appearance of bilateral infiltration on chest X-ray within 6 hours of transfusion of a plasmacontaining product. The exact mechanism is unknown but in a subset of patients, donor antibodies (usually antiHLA) react with the recipient's white blood cells resulting in both release of intracellular inflammatory mediators and leukoagglutination in the lungs.

Differential Diagnosis

It may be difficult to distinguish TRALI from circulatory overload or adult respiratory distress syndrome.

Therapy

Care is supportive including supplemental oxygen. Approximately 75% of patients will require mechanical ventilation. Most patients will recover in 2 to 4 days; mortality rate is 5% to 10%.