By Will Rust
Transfusion-associated circulatory overload (TACO) is becoming increasingly recognized as a serious and frequent complication of blood transfusion in the ICU. Challenges faced by practitioners in their efforts to prevent and treat TACO include the difficulty in obtaining a clear diagnosis, quantifying the incidence, and determining the risk factors. "Understanding TACO and Making It Go Away" (9122-TC) explored the epidemiology of TACO and introduced strategies for increasing TACO awareness, educating practitioners and enhancing patient care.
Transfusion-Associated Circulatory Overload
Mark A. Popovsky, MD, from Harvard Medical School and Haemonetics, provided the audience with fundamentals of transfusion-associated circulatory overload (TACO). The most frequent presentation is shortness of breath, hypertension, and O2 desaturation. The incidence of TACO from published studies is 1% to 8%. The clinical impact of this condition is increased morbidity (21% of cases are life-threatening) and increased stay in the intensive care unit (ICU). Mortality data from the Food and Drug Administration (FDA) suggest that TACO is responsible for up to 27% of fatalities related to transfusion. Risk factors include very young or old age, but demographics from the Quebec Hemovigilance System suggest that TACO can occur at any age group. Mortality data from French Hemovigilance, Quebec Hemovigilance, and the université Pierre et Marie Curie (UPMC) demonstrate that TACO is not a benign condition.
Risk factors for patients in the ICU include a positive fluid balance, a faster rate of transfusion and underlying left ventricle dysfunction. Recommendations for diagnosis, treatment and prevention are provided by the Circular of Information and the AABB Technical Manual; however, the guidance does not account for the patient's weight or underlying cardiac reserve.
Transfusion-Associated Circulatory Overload in the Critically Ill
Daryl J. Kor, MD, from the Mayo Clinic, noted that it is important to recognize the epidemiology of TACO in the critically ill and to understand the challenges of making a diagnosis. The incidence of TACO ranges from 1% (according to hemovigilance reports) to 11% (according to active surveillance data). There is a higher incidence in the critically ill but the true incidence is unclear due to poor recognition and under-reporting. Attributable mortality is unclear, with estimates as much as 15%. TACO is clearly associated with requirements for advanced levels of care and greater duration of ICU and hospital stays.
A chronic problem with TACO diagnosis and reporting is unclear diagnosis. A report of active surveillance of all plasma transfusion episodes for one month (84 patients) was presented. Of these, four TACO episodes occurred and none were reported to the blood bank by the clinical service. Electronic surveillance of arterial blood gas identified 10,184 alerts and 101,348 no-alerts. After review by an expert panel, 123 cases were identified as TACO. The active surveillance algorithm correctly identified 45 TACO cases. Of these, only five were reported to the blood bank. A challenge for correct identification is that TACO presents similarly to TRALI and transfusion-associated dyspnea (TAD). The CDC biovigilance criteria has helped to define TACO for recognition and reporting.
A case study was presented in which the patient could have TACO, TRALI, or both — showing that cases are not always clear. It is also more complex than fluid overload. There could be some contribution by nitric oxide scavenging by red cells, leading to increased vascular resistance. The pathophysiology of TACO includes increased hydrostatic pressure in the pulmonary capillaries, leading to excess edema fluid filtering through the capillary endothelium. The lymphatic drainage becomes overwhelmed, flooding the alveoli with fluid. The management of TACO includes supportive care with oxygen supplementation, ventilator support and volume reduction.
Mitigating TACO: The Role of Bedside Biovigilance
Chester Andrzejewski, PhD, MD, FCAP, from Baystate Health and Tufts University, followed with more specifics on recognition and mitigation. Echoing earlier comments, he observed that TACO is caused by increased hydrostatic pressure in the pulmonary blood circuit, which in turn leads to extravascular fluid accumulation in the lungs. TACO causes shortness of breath, cyanosis, rales, cough, increased heart rate, increased blood pressure, headache and pulmonary edema. It occurs during or within several hours of transfusion.
TACO is clinically acknowledged but many times ignored. A cause for under-appreciation of TACO is that there is no universally accepted case definition. Variability exists in the identification and reporting of TACO and few data are available. Regardless, TACO is a frequent and serious event in an orthopedic surgical setting. It is associated with advanced age, increased health care costs, and may occur with only modest transfusion volumes. Several case studies were presented highlighting diagnoses and treatments for TACO.