Transfusion-associated circulatory overload

Did You Know?

• Death from pulmonary edema due to circulatory overload after transfusion was reported as early as 1936.
• The term 'transfusion-associated circulatory overload' was coined in the 1990s.

Risk factors

Conditions that predispose to excess circulatory fluid—such as liver failure with hypoalbuminemia, heart failure, renal insufficiency, or nephrotic syndrome—increase the risk of TACO. Lung disease, severe anemia requiring large-volume transfusions, and extremes of age (under 3 years or over 60 years) are also risk factors. The risk rises with the number of blood product units transfused.

Diagnosis

Within 12 hours after transfusion ends, a patient must have acute or worsening respiratory distress (tachypnea, dyspnea, cyanosis, hypoxemia) without other causes, or evidence of acute or worsening pulmonary edema on exam or chest imaging. Additionally, there must be elevated BNP or NT-proBNP, cardiovascular changes (tachycardia, hypertension, widened pulse pressure, jugular venous distension, peripheral edema), or evidence of fluid overload. Severity is categorized as non-severe, severe, life-threatening, or death. TACO is often confused with TRALI; differentiating them relies on fluid status: TACO always involves positive fluid balance, hypertension, jugular venous distension, elevated BNP, peripheral edema, and response to diuretics, whereas TRALI does not.

Pathogenesis

TACO is thought to follow a two-hit mechanism. The first hit is the patient’s underlying condition—such as heart or kidney dysfunction—that predisposes to fluid excess. The second hit is the blood transfusion itself, which overwhelms the circulatory system with additional volume. The resulting increased hydrostatic pressure forces fluid into tissues: in the lungs it accumulates in air sacs, causing hypoxemia and dyspnea; in the limbs it causes peripheral edema, most notably in the legs due to gravity. Conditions that raise hydrostatic pressure (heart failure, renal insufficiency) or lower oncotic pressure (liver failure, malnutrition, nephrotic syndrome) increase susceptibility.

Prevention

Prevention relies on avoiding unnecessary transfusions by adhering to strict transfusion criteria, monitoring patients closely, and transfusing smaller volumes at slower rates. For high-risk individuals, the infusion rate may be reduced to 1.0 ml/kg per hour. Patients susceptible to volume overload, such as those with renal insufficiency or heart failure, may receive a diuretic during or immediately after transfusion to lower net fluid balance.