NT-pro-BNP as a diagnostic marker for Transfusion-Associated Circulatory Overload (TACO) in the Postoperative ICU Patient
Syed Rizvi MD1, & Dhamodaran Palaniappan MD1,2
Department of Anesthesiology, University of Connecticut School of Medicine, Farmington, CT1; Department of Anesthesiology, Hartford Hospital, Hartford, CT2
Introduction:
• NT-pro-BNP is released when there is stress on the myocardial walls from either pressure or volume overload. It is produced when the prohormone pre-pro-BNP is cleaved.1
• Accepted normal levels of NT-pro-BNP are less than 250 pg/ml. Elevated levels are age-dependent: >450 pg/ml (age <50 years old), >900 pg/ml (age 50-75 years old), and >1800 pg/ml (age >75 years old).
• Evidence has shown that NT-pro-BNP is released in cardiac and pulmonary diseases.2 It is also released in Transfusion-Associated Circulatory Overload (TACO).3
Case:
• 83-year-old male admitted to the ICU with urosepsis s/p ureteroscopy and stent change.
• PMH/PSH: CKD (Baseline Cr 2.8-3.0 mg/dl), chronic anemia, diabetes mellitus, and bladder cancer s/p robotic radical cystectomy and ileal loop creation (June 2011).
• POD #0: Patient was hypotensive. He received a one-liter bolus of normal saline and 250 mL 5% albumin bolus which improved his hypotension.
• POD #1: Patient had acute blood loss anemia from his ileal loop. His hemoglobin was 6.0 g/dl. The decision was made to transfuse him with two units of packed red blood cells.
• During the transfusion, the patient became acutely dyspneic and hypertensive.
Assessment and Management:
• Patient was evaluated and showed signs of increased work of breathing.
• He was placed on noninvasive positive pressure ventilation (NPPV).
• He was hypertensive with his oxygen saturations in the low 90’s.
• Differential diagnosis at this point included TACO or an acute pulmonary embolism.
• CXR showed nonspecific interstitial opacities.
• Ruling out a pulmonary embolism was difficult. CT angiogram could not be performed due to the patient’s kidney disease. V/Q scans are often indeterminate. An ultrasound doppler study of his lower extremities was negative for deep venous thrombosis. An echocardiogram did not show evidence of right heart strain although it did show pulmonary hypertension.
• A discussion did arise to treat the suspected pulmonary embolism with anticoagulation. It was decided that anticoagulation would not be wise in this patient who had active blood loss in the past day.
• Laboratory testing showed elevated NT-pro-BNP levels. This helped solidify our diagnosis of TACO.
• Given this information, the ICU team made the decision to diurese the patient.
• As the patient was diuresed, his NT-pro-BNP levels decreased and his clinical picture improved. He was taken off of the NPPV on POD #3.
Discussion:
• Acute pulmonary embolism can also cause an increase in NT-pro-BNP levels due to increased right heart strain.4 NT-pro-BNP levels are usually lower in acute pulmonary embolism than diseases which affect the left ventricle such as CHF.5
• The specificity of NT-pro-BNP levels in acute pulmonary embolism decreases with increasing levels of NT-pro-BNP.5
• Tobian et al., performed a case control study on 40 participants who had pre and post transfusion NT-pro-BNP levels recorded. Their study found the sensitivity of NT-pro-BNP to diagnose TACO to be 93.8% and the specificity to be 87.5%.3
• NT-pro-BNP levels can be a useful marker to help diagnose transfusion-associated circulatory overload.
• It can also be useful in the management of disease progression or regression.
• In this case, as the NT-pro-BNP levels decreased, the patient clinically improved.
• Due diligence must be performed when making any diagnosis. A single laboratory test cannot be used to make a diagnosis.
• Further research must be performed to specifically correlate laboratory values to specific disease states.
References:
1. Vanderheyden M, Bartunek J, Goethals M. Brain and other natriuretic peptides: molecular aspects. Eur J Heart Fail. 2004 Mar 15;6(3):261-8.
2. Salerno D, Marik P. Brain natriuretic peptide in pulmonary medicine. Respiratory Medicine. (2011) 105, 1770-1775
3. Tobian AAR, Sokoll LJ, Tisch DJ, Ness PM, Shan H. N-terminal pro-brain natriuretic peptide is a useful diagnostic marker for transfusion-associated circulatory overload.
Transfusion 2008;48:1143.
4. Pasha, S.M., Klok, F.A., van der Bijl, N., de Roos, A., Kroft, L.J., Huisman, M.V. NT-pro- BNP levels in patients with acute pulmonary embolism are correlated to right but not left ventricular volume and function. Thromb Haemost. 2012;108:367–372.
5. Guo L, Li G, Wang Y, et al. Diagnostic utility of N-terminal-proBNP in differentiating acute pulmonary embolism from heart failure in patients with acute dyspnea. Chin Med J. 2014;127(16):2888-93.
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