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Definition

Volume overload, or transfusion‐associated circulatory overload (TACO), is recognized when signs of respiratory distress and pulmonary edema occur after a large volume transfusion.

Risk factors

 Large volume of whole blood given to normovolemic patient

 Total dose (ml/kg) of blood products was a risk factor in a study of dogs receiving packed RBC transfusions [15].

 Large volume of crystalloid or colloid fluids administered in addition to blood transfusion

 Preexisting conditions, such as heart failure and renal failure

Pathogenesis

Volume overload is uncommon in adult horses receiving blood transfusions, but may occur with smaller patients such as miniature horses and foals [16]. Massive transfusion, defined as transfusion of one blood volume or more within 24 hours or 50% of one blood volume within 3 hours, may lead to additional complications [17]. Massive transfusion can cause hypocalcemia associated with citrate toxicity. Liver failure has been reported in neonatal foals receiving large volume transfusions to treat neonatal isoerythrolysis, likely due to iron overload [18].

Prevention

Volume overload can be avoided with careful calculation of total fluid volume planned for treatment of the patient. In normovolemic patients, packed RBCs should be used, when available.

Diagnosis

Clinical signs include dyspnea and cyanosis. Signs of pulmonary edema may be seen on thoracic ultrasound or radiographs.

Treatment

Discontinue the transfusion (if still in progress) and administer supplemental oxygen. Furosemide (1.1 mg/kg IV) should be administered as a diuretic.

Expected outcome

Prognosis is good if the condition is recognized early and treated appropriately, assuming there are not underlying clinical conditions such as heart failure, renal failure, or sepsis.