Transfusion-associated circulatory overload (TACO)

Transfusion-associated circulatory overload (TACO) is a common transfusion reaction where pulmonary oedema due to excess volume or circulatory overload results in the patient experiencing acute respiratory distress.
 
TACO is a clinical diagnosis and clinical evidence may include a positive fluid balance or cardiac involvement such as left heart failure, elevated blood pressure, or tachycardia.
 
TACO is the leading cause of transfusion-related deaths reported to the US Federal Drug Administration (FDA), accounting for 62 (or 34%) of reported fatalities from 2016-2020.
Similarly, TACO is also responsible for most deaths and major morbidity reported to the UK Serious Hazards of Transfusion (SHOT) scheme. In the period 2010 to 2024, there were 157 deaths (41.4%) reported. 

However, TACO remains poorly understood and almost certainly under-reported. 

When to suspect this adverse reaction

For haemovigilance reporting, the criteria for diagnosing TACO are taken from the NBA’s 2024 Australian Haemovigilance Minimum Data Set (AHMDS) and are modified from the SHOT definition:

The presence of a total of 3 or more of criteria A-E below, including at least one required criterion during or up to 12 hours after transfusion: 

Required criteria

A. Acute or worsening respiratory compromise and/or
B. Evidence of acute or worsening pulmonary oedema

Additional criteria

C. Evidence of cardiovascular system changes e.g., development of tachycardia, hypertension, jugular venous distension, enlarged cardiac silhouette and/or peripheral oedema 
D. Evidence of fluid overload, e.g., a positive fluid balance; clinical improvement following diuresis 
E. Supportive result of a relevant biomarker, e.g., an increase of B-type natriuretic peptide levels

Usual causes

TACO is typically seen in patients who rapidly receive a large volume of transfused products or those with underlying cardiovascular or renal disease. TACO is therefore both a volume and rate-related advrese reaction.
 
The risk generally increases with the number of blood products that are transfused.
 
Patients over 60 years of age, infants and the severely anaemic are particularly susceptible.
 
TACO occurs in approximately 1% to 2.7% of patients receiving transfusions.

Using a TACO assessment tool prior to transfusion is recommended

Investigation

• Perform a chest X-ray to assess for pulmonary oedema. 
• Assess other cause(s)/contributors to pulmonary oedema (e.g. renal function, sepsis, non-cardiogenic pulmonary oedema (TRALI). 
• Determine B-type natriuretic peptide (BNP) or NT pro-BNP levels – a normal post-transfusion level is not consistent with diagnosis of TACO. 
• Consider an echocardiogram to assess cardiac function (e.g. right atrial hypertension). 

Monitoring patients and observing vital signs during transfusion is the key to early recognition and diagnosis of TACO. Comparison with observations and net fluid balance from the 24 hours before the transfusion may be valuable.
 
TACO is frequently confused with transfusion-related acute lung injury (TRALI) and it’s possible for them to occur concurrently.  Both may exhibit new onset hypoxaemia and new or worsening bilateral infiltrates on chest X-ray consistent with pulmonary oedema.
 
Hypertension is a constant feature in TACO whereas it is infrequent in TRALI.

Other key clinical features include tachycardia and widened pulse pressure, lung crackles on auscultation and signs of congestive cardiac failure.

What to do

Stop transfusion immediately and follow other steps for managing suspected transfusion reactions.
 
Place the patient in an upright position and treat symptoms with oxygen, diuretics and other cardiac failure therapy.
 
In serious cases, mechanical ventilation and treatment in the intensive care unit (ICU) may be required.

How to prevent

In susceptible patients at risk for TACO (elderly or paediatric patients, patients with severe anaemia and patients with congestive heart failure or renal disease), transfusion should be administered slowly and consideration given to the use of a diuretic.

A formal pre-transfusion risk assessment (TACO checklist) should be undertaken whenever possible for all patients receiving blood transfusion especially if elderly (typically older than 70 years) or weighing less than 50 kg.
 
If principles of patient blood management (PBM) are followed, unnecessary transfusions in non-bleeding anaemic patients should reduce the number of transfusions and therefore potentially reduce the incidence of TACO.

Updated June 2026