The paper by Clifford et al. reports on the results of a very interesting retrospective study evaluating the epidemiology of transfusion-associated circulatory overload (TACO) in the specific setting of non-cardiac surgery. Although TACO is currently considered one of the most frequent severe transfusion reactions and has been reported as the second leading cause of transfusion related-deaths by some international health institutions, few reliable data are available on its real incidence, particularly in the surgical setting where its rate could be expected to be lower than in other clinical situations because of the hypovolaemia-inducing condition associated with surgical bleeding. Interestingly, the authors also evaluated the possible beneficial role of leukoreduction in preventing the occurrence of TACO by comparing its incidence in patients transfused before (year 2004) and after (year 2011) the implementation of universal leukoreduction in their hospital.

The TACO episodes in the studied population (adult patients who received intraoperative blood product transfusions during non-cardiac surgery) were identified by screening the electronic medical records of all the eligible patients with an electronic algorithm allowing the selection of patients with evidence of hypoxemia within 6 hours of blood product transfusion and abnormalities consistent with TACO on chest radiographs. Patients with preoperative respiratory failure of diffuse bilateral infiltrates on chest radiographs, those receiving extracorporeal membrane oxygenation initiated intraoperatively before blood transfusion or undergoing non-general anaesthesia were excluded from the study. All the cases identified by the electronic algorithm as possible TACO were reviewed by two independent physicians to confirm or exclude the diagnosis, accordingly to the TACO definition from the Biovigilance Component of the CDC National Healthcare Safety Network.

Of the 4070 patients included in the evaluation, a total of 176 patients were identified as experiencing TACO with an overall rate of 4.3%. The incidence of TACO decreased significantly from 5.5% in 2004 to 3.0% in 2011 but the reduction in the rate of TACO could not be clearly attributed to variation in transfusion volume (which was comparable between calendar years) or intraoperative fluid balance (which was significantly reduced from 4632 mL to 3 655 mL for 2004 and 2001, respectively) thus supporting a potential preventive role of universal leukoreduction as previously reported by Blumberg et al. (Transfusion 2010;50:2738-44).

Interestingly, of the 176 cases of TACO identified by the authors, only 3 were included in the transfusion service’s database of potential transfusion reactions, which demonstrates how frequently TACO is unrecognised and underreported despite its clinical relevance. The study demonstrates that TACO occurrence was not clinically insignificant. Indeed, TACO cases had significantly longer postoperative hospital long of stay and an higher in-hospital mortality (odds ratio 3.8) compared with transfused patients who did not have TACO.

In conclusion, the large number of data on epidemiology of TACO reported by this very relevant study highlights the need for appropriate studies to better define both the patient population at higher risk for this still poorly recognised but clinically relevant transfusion reaction and the most effective strategies to mitigate its occurrence.

– G. Inghilleri

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