(454) Effect of Hyperbilirubinemia and Plasma Exchange on Anticoagulation With Unfractionated Heparin

Introduction: Monitoring unfractionated heparin (UFH) is challenging in the setting of mechanical circulatory support. Further complicating this are conditions that alter traditional coagulation tests. We present a case of extreme hyperbilirubinemia managed with therapeutic plasma exchange (TPE) where the anti- factor Xa (anti-Xa) assay and activated partial thromboplastin time (aPTT) were unreliable.

Description: A 67-year-old female with newly diagnosed hiatal hernia presented for elective paraesophageal hernia repair. Her operative course was complicated by a massive pulmonary embolism (PE) requiring venoarterial extracorporeal membrane oxygenation (ECMO). Peri-arrest chest tube placement was complicated by a liver laceration. Massive transfusion protocol was initiated. Computed tomography (CT) the next morning showed bilateral PEs with right ventricular strain and bilateral mechanical thrombectomy was performed. The patient was initially on bivalirudin, but imaging on ECMO day seven showed unchanged clot burden with one new subsegmental PE. The patient was transitioned to UFH given concern for failure to respond to bivalirudin.

The patient also developed acute liver dysfunction and direct hyperbilirubinemia early in her course. By day 16 the total bilirubin was 53 mg/dL. The laboratory was unable to accurately report aPTT and the patient was converted to an activated clotting time (ACT)-guided UFH titration strategy. Ultimately, the patient underwent TPE to manage hyperbilirubinemia. Repeat CT on day 19 demonstrated a 20-40% improvement in clot burden with therapeutic ACT (180-200 seconds).

Discussion: Monitoring of UFH in the setting of hyperbilirubinemia has proven difficult. Measurements of anti-Xa and aPTT have both been shown to be impacted by the presence of high bilirubin levels and it has been previously recommended to switch to direct thrombin inhibitors in this case. However, our patient had already failed to respond to bivalirudin and this was not an acceptable approach. TPE was initiated to help reduce bilirubin levels and render laboratory values more accurate for patient monitoring. However, TPE itself has also been known to interfere with both anti-Xa and aPTT monitoring. Ultimately, an ACT-guided approach was successfully utilized to manage UFH without complications.