In transfusion medicine, transfusion-associated circulatory overload (aka TACO) is a transfusion reaction (an adverse effect of blood transfusion) resulting in signs or symptoms of excess fluid in the circulatory system (hypervolemia) within 12 hours after transfusion. The symptoms of TACO can include shortness of breath (dyspnea), low blood oxygen levels (hypoxemia), leg swelling (peripheral edema), high blood pressure (hypertension), and a high heart rate (tachycardia).
It can occur due to a rapid transfusion of a large volume of blood but can also occur during a single red blood cell transfusion (about 15% of cases). It is often confused with transfusion-related acute lung injury (TRALI), another transfusion reaction. The difference between TACO and TRALI is that TRALI only results in symptoms of respiratory distress while TACO can present with either signs of respiratory distress, peripheral leg swelling, or both. Risk factors for TACO are diseases that increase the amount of fluid a person has, including liver, heart, or kidney failure, as well as conditions that require many transfusions. High and low extremes of age are a risk factor as well.