FINAL DIAGNOSIS: TRANSFUSION ASSOCIATED CIRCULATORY OVERLOAD
Transfusion associated circulatory overload, abbreviated TACO, is a crucial consideration in the differential diagnosis of a patient developing acute respiratory distress temporally coinciding with transfusion of blood product. In the case of NV, his rapid onset of respiratory distress and white-out chest x-ray was indeed concerning for Transfusion Related Acute Lung Injury, or TRALI. However, upon careful examination of the medical notes and transfusion records, it became evident that the patient received a large volume of blood product over a short period of time. The patient received the two units of FFP early in the day, and then received four additional units, for a total of six units FFP, approximately 1200 mL. The latter four units were transfused in rapid succession between 2:40PM and 3:25PM. In an elderly patient hospitalized for a procedure, this large volume challenge likely overloaded his circulatory system.
Two multicenter, retrospective analyses of patients undergoing total knee or total hip replacement surgery TACO was observed in 1% and 8 % of cases. If these data approximate the true frequency, TACO is drastically under-recognized and under-reported. An additional study indicated that 20% of the reported TACO cases occurred with single-unit RBC transfusion, suggesting that relatively small volumes of blood may trigger TACO.
A study by Zhou et al. at the University of Michigan examined the use of BNP as a useful adjunctive laboratory study to help differentiate TACO from other transfusion reactions. They examined the clinical outcomes of 40 patients who received transfusions, of which 21 patients were diagnosed with TACO. They used a rapid immunoassay for BNP in pre-transfusion and post-transfusion samples. They compared BNP levels between patients diagnosed with TACO and patients in a control category that included febrile non-hemolytic transfusion reactions, allergic reactions, and no reactions. There appeared to be an increased level of BNP in the TACO groups, however the separation between the data was not ideal (figure 5). The same data was analyzed in ratio form to compare BNP levels post-transfusion to pre-transfusion, which provided much stronger separation between the two groups (figure 6). Sensitivity and specificity were maximized with a ratio of 1.5, sensitivity of 81%, specificity 89%. Fisher's exact test was used to identify clinical features with statistically significant (p < 0.05) differences between TACO and control patients. These included a post-transfusion to pre-transfusion BNP ratio greater than 1.5, a significant change in systolic BP (greater than 30 mmHg), and acute dyspnea. Interestingly, clinical features which did not show statistically significant differences between TACO and control patients included transfusion of multiple units, history of congestive heart failure, impaired renal function, and tachycardia. This research suggests that a post-transfusion to pre-transfusion BNP ratio may be a useful non-invasive laboratory test to help differentiate TACO from other transfusion-associated pulmonary reactions. The study is limited by the small number of cases examined, and the absence of any TRALI cases for comparison.
A letter to the editor followed that reported a single case in which a 70 year old male with no history of heart disease underwent radical prostatectomy, cystectomy and received one unit of FFP. He developed TRALI, and as part of his laboratory workup a BNP level was drawn on a sample 85 minutes after the start of transfusion, 54 pg/mL (ref: 0-100 pg/mL). This normal BNP result lowered the likelihood that TACO caused his clinical picture. In the case of this patient, a diagnosis of TRALI was supported by high reactivity with HLA antigens, and the donor was deferred.
The patient management in both TACO and TRALI largely involves supportive care. The blood bank management differs depending on the diagnosis. TRALI requires work up of the donor product with HLA testing and possible donor deferral. TACO is a mechanical issue, and the blood bank will recommend slow transfusion of products in the future with careful input and output monitoring. Neither is a contraindication for future transfusion.
In the case of our patient NV, his clinical course was consistent with TACO. He improved rapidly and responded to diuretics, a repeat chest X-ray showed clearing of the white out picture with residual pulmonary edema (figure 7). His BNP laboratory values show a post-transfusion to pre-transfusion ratio approximating 1.5, which supports a diagnosis of TACO. With an INR of 1.1 the following day, he was cleared for surgery and underwent ORIF surgical repair (figure 8). He resumed coumadin for atrial fibrillation and DVT prophylaxis. Of note, the patient developed post-operative anemia with Hgb 7.5 g/dL and HCT 21.9%. He was transfused two units of packed red blood cells with premedication of Benadryl and hydrocortisone and experienced no adverse reaction.
Contributed by Amber Henry, MD, Darrell Triulzi, MD, and Mark Yazer, MD