Mechanism -- Transfusion-Associated Circulatory Overload (TACO)

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].


  1. Popovsky, MA. Transfusion-associated circulatory overload. ISBT Science Series 2008, 3:166-169.
  2. Narick C, Triulzi DJ, Yazer MH. Transfusion-associated circulatory overload after plasma transfusion Transfusion. 2011. (ahead of print)
  3. Fontaine MJ, Malone J, Mullins FM, Grumet FC. Diagnosis of Transfusion-Related Acute Lung Injury: TRALI or Not TRALI? Annals of Clinical & Laboratory Science 2006;36:53-58.
  4. Li G, Rachmale S, Kojicic M, Shahjehan K, Malinchoc M, Kor DJ, Gajic O. Incidence and transfusion risk factors for transfusion-associated circulatory overload among medical intensive care unit patients. Transfusion 2010; 51:338-343.
  5. Hendrickson JE, Hillyer CD. Transfusion-Associated Circulatory Overload. In: Hillyer CD, Shaz BH, Zimring JC, Abshire, eds. Transfusion Medicine and Hemostasis: Clinical and Laboratory Aspects. 1st ed. New York, NY: Elsevier; 2009: 607-629.
  6. Standards for Blood Banks and Transfusion Services, 25th Edition. Bethesda, AABB Press.
  7. Kleinman S, Caufield T, Chan P et al. Toward an understanding of transfusion-related acute lung injury: Statement of a consensus panel. Transfusion 2004; 44:1774-1789.
  8. Vesely SK et al. ADAMTS13 activity in thrombotic thrombocytopenic purpura-hemolytic uremic syndrome: relation to presenting features and clinical outcomes in a prospective cohort of 142 patients. Blood 2003; 102(1):60-68.
  9. Popovsky MA. Transfusion and lung injury. Transfus Clin Biol 2001; 8:272-7.

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