Mechanism -- Transfusion-Associated Circulatory Overload (TACO), in a background setting of thrombotic thrombocytopenic purpura (TTP)
Recognition of TACO
Transfusion-associated circulatory overload (TACO) is a recognized transfusion reaction in critically ill patients with an incidence range of 1:708 to 1:4075 in general hospital settings, and 1-8% in orthopedic patients [1]. TACO occurs when the circulatory system becomes overwhelmed by additional volumes of blood products, or a high infusion rate of such products [2]. Clinically, patients present with sudden dyspnea, orthopnea, tachycardia and a wide pulse pressure, often associated with hypertension and hypoxemia. If there is a progression to cardiac collapse, subsequent hypotension may result, as seen in this case.
TACO: More frequent, but frequently underreported
While a relatively common occurrence, TACO remains significantly underreported to blood banks and is often unrecognized by clinicians [3]. TACO is seen especially in elderly patients, small children, and patients with compromised left ventricular function [3]. Risk factors include increased volume and increased rate at which transfusion occurs, while cohort analysis has shown increased incidence of TACO in the setting of ICU and fresh-frozen plasma ordered for the reversal of anticoagulants [5].
Differentiating TACO from TRALI
Differentiating TACO from TRALI can be difficult; however, patients in TACO will have an increase in BNP over baseline and will show symptoms of central venous overload, such as an elevated jugular venous pulse [6]. Precaution measures include a transfusion rate appropriate for the patient (1-2.5 mL/kg per hour), close monitoring of patient's symptoms and vital signs, and small doses of diuretics between transfusions [8]. Unlike TRALI, TACO patients usually respond well to diuretics and oxygen supplementation [8]. Unlike TACO, lung injury with TRALI is associated with HLA (human leukocyte antigen) antibodies directed against the lung parenchyma [10].
In this patient, various indications suggest that this patient could have been susceptible to a TACO reaction during this admission:
Although TRALI may be in the differential, it is associated with an overall hypovolemic state as opposed to a hypervolemic state with TACO. While one could argue that this patient was hypovolemic by his hypotension, he had other parameters, including a massively increased BNP, liver failure, renal failure and multiple
transfused blood products. The chest x-ray did not show bilateral infiltrates or a 'whiteout' pattern, but rather increased pulmonary vascular congestion. It is important to note that TACO can present in any incident of transfusion, regardless of the amount given, with even a single transfused unit sufficient to precipitate a reaction in a susceptible recipient [12].
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