Therapeutic Plasma Exchange and Supratherapeutic Levels of Unfractionated Heparin in the Management of Critically Ill Patient with Myasthenia Gravis: A Case Report

Patient: Female, 78-year-old Final Diagnosis: Myasthenia gravis (MG) Symptoms: High activated partial thromboplastin time (aPTT) Medication: Unfractionated heparin (UFH) Clinical Procedure: Thymectomy • transfusion plasma exchange (TPE) Specialty: Critical Care Medicine • Hematology OBJECTIVE: Unusual clinical course BACKGROUND: Therapeutic plasma exchange (TPE) is an extracorporeal method of filtration indicated in several conditions, including myasthenia gravis (MG). The removal and replacement of plasma through TPE affect the level of coagulation factors, suggesting alterations in homeostasis. TPE also has the potential to remove medications from the plasma. Insufficient data are available that evaluate the effect of TPE on certain medications, such as unfractionated heparin (UFH). CASE REPORT: We report a case of a 78-year-old woman with MG. She underwent a thymectomy complicated by phrenic nerve injury and respiratory failure, requiring admission to the Intensive Care Unit (ICU) and mechanical ventilation. She developed a provoked left upper extremity deep venous thrombosis and started on therapeutic UFH with a target activated partial thromboplastin time (aPTT) of 50 to 80 seconds. Despite being on immunosuppressants, additional therapy with TPE was deemed necessary for her MG exacerbation. Therefore, she received 5 sessions of TPE, given every other day. Interestingly, while on TPE therapy, the aPTT increased significantly after each administration, with TPE reaching >170 seconds in some instances. As a precautionary measure, heparin infusion was held for 1 day based on the institutional heparin protocol and the physician’s decision. Fortunately, the patient did not develop any bleeding complications. CONCLUSIONS: TPE treatment may temporarily deplete the coagulation factors, leading to supratherapeutic aPTT levels. UFH dose adjustment and frequent assessment of aPTT levels are essential during TPE treatment to minimize serious bleeding complications. Future studies with a larger sample size are required to focus on understanding the effect of TPE on medications.