Transfusion-Associated Circulatory Overload (TACO) is similar to TRALI since it is associated with transfusion and presents with similar symptoms of hypoxia and pulmonary edema. As with most cases of TRALI, TACO is temporary, and symptoms generally subside within hours of transfusion. Unlike TRALI, the edema in TACO is caused by hydrostatic forces (hydrostatic edema) as opposed to changes in membrane permeability. Most patients with TACO respond well to diuresis, but the mortality rate remains high (5–15%). Risk factors include age (>70 years and infants are at higher risk) and kidney and cardiac dysfunction. Even though the mechanisms differ substantially, no direct tests can differentiate TRALI from TACO. Some clinical features that differentiate TACO from TRALI are listed in the table on the following page.
TACO incidence varies from 1 to 8% of all transfusions depending upon the patient population and the type of reporting (passive reporting versus active reporting). The risk of TACO increases as the transfusion volume and rate of infusion increase. Because of the volume infused, FFP is associated with a high risk for TACO. TACO has surpassed TRALI with the highest number of transfusion-related mortalities, with the highest number being an estimated 34%.
TACO risk can be reduced by careful attention to infusion volumes and rates in high-risk groups such as older people, avoiding unnecessary transfusion, and using diuretics as indicated.
