What are TACO (Transfusion-Associated Circulatory Overload) and TRALI (Transfusion-Related Acute Lung Injury)?

TACO and TRALI: Transfusion-Related Pulmonary Complications

Transfusion-Associated Circulatory Overload (TACO) and Transfusion-Related Acute Lung Injury (TRALI) are distinct but serious transfusion complications that both present as acute respiratory distress following blood transfusion, with TACO being cardiogenic pulmonary edema occurring within 12 hours of transfusion and TRALI being non-cardiogenic pulmonary edema occurring within 6 hours of transfusion. 1

Key Definitions

TACO (Transfusion-Associated Circulatory Overload)

• Definition: Cardiogenic pulmonary edema due to circulatory overload following transfusion 1
• Timing: During or within 12 hours of transfusion 2, 1
• Incidence: Relatively common, with rates of 1-8% of transfused patients depending on the clinical setting 2

TRALI (Transfusion-Related Acute Lung Injury)

• Definition: Non-cardiogenic pulmonary edema occurring within 6 hours of transfusion 1
• Timing: Within 6 hours of transfusion 1
• Incidence: Approximately 0.81 per 10,000 transfused blood components (8.1 per 100,000) 2, 1

Distinguishing Features

Characteristic	TACO	TRALI
Pathophysiology	Cardiogenic pulmonary edema	Non-cardiogenic pulmonary edema
Onset	During or up to 12 hours post-transfusion	Within 6 hours of transfusion
Blood Pressure	Typically hypertension	Normal or hypotension
BNP/NT-proBNP	Significantly elevated	Normal or mildly elevated
Imaging	Bilateral infiltrates with cardiogenic pattern and vascular redistribution	Bilateral infiltrates with permeability edema pattern
Response to diuretics	Usually positive	Limited or no response

Pathophysiology

TACO

• Results from volume overload exceeding the heart's capacity to maintain adequate cardiac output 1
• Risk factors include:
  • Age >70 years
  • Heart failure
  • Renal failure
  • Positive fluid balance before transfusion
  • Rapid transfusion rate 1

TRALI

• Follows a "two-hit" model:
  1. First hit: Pre-existing inflammation in the patient (the "primed" state)
  2. Second hit: Transfusion-related factors 1
• Mechanisms:
  • Immune-mediated: HLA class I/II antibodies or Human Neutrophil Antibodies (HNA) in donor plasma react with recipient's white blood cells (accounts for ~2/3 of cases) 1
  • Non-immune mediated: Biological response modifiers (e.g., lipids) in stored blood products 1, 3

Clinical Presentation

TACO

• Acute respiratory distress
• Tachycardia and hypertension
• Evidence of fluid overload (jugular venous distension, peripheral edema)
• Elevated BNP/NT-proBNP 1

TRALI

• Acute respiratory distress
• Hypoxemia (PaO2/FiO2 ≤ 300 mmHg or SpO2 < 90% on room air)
• Bilateral pulmonary infiltrates
• Fever (common)
• Normal blood pressure or hypotension
• No evidence of left atrial hypertension 1

Management

TACO

• Immediate cessation of transfusion
• Upright positioning
• Oxygen supplementation
• Diuretic therapy (IV furosemide)
• Close monitoring of fluid balance
• Respiratory support as needed 1

TRALI

• Immediate cessation of transfusion
• Respiratory support (oxygen, mechanical ventilation if needed)
• Avoid diuretics unless concurrent fluid overload is present
• Judicious fluid management
• Vasopressors for persistent hypotension
• Lung-protective ventilation strategies if intubated 1

Prevention

TACO Prevention

• Risk assessment before transfusion
• Slower transfusion rates for high-risk patients
• Body weight dosing for RBCs
• Prophylactic diuretics in high-risk patients
• Appropriate blood product utilization 1

TRALI Prevention

• Male-only plasma when possible
• Screening donors with history of pregnancy for anti-HLA antibodies
• Deferring donors implicated in previous TRALI cases
• Avoiding unnecessary transfusions 1

Prognosis

• TACO: Generally responds well to diuretic therapy and supportive care
• TRALI: Most patients show clinical improvement within hours, with complete resolution typically occurring within 96 hours 1
• Both conditions remain leading causes of transfusion-related morbidity and mortality 4, 3

Understanding the distinctions between these two entities is crucial for appropriate management, as treatment strategies differ significantly, particularly regarding fluid management and use of diuretics.