Prolonged Anticoagulation After Discontinuation of Argatroban and Warfarin Therapy in an Obese Patient with Heparin‐Induced Thrombocytopenia

A 32‐year‐old, morbidly obese African‐American woman developed bilateral pulmonary emboli 12 days after undergoing Roux‐en‐Y gastric bypass surgery. Three days later, after receiving heparin and warfarin, she developed heparin‐induced thrombocytopenia type II (HIT‐II). An argatroban 1.5‐μg/kg/minute infusion was administered for approximately 2.5 days. The patient also received four doses of warfarin, totaling 37.5 mg. The argatroban infusion was discontinued early on hospital day 6, at which time the patient's international normalized ratio (INR) was 4.36 and activated partial thromboplastin time (aPTT) 85.9 seconds. Her INR and aPTT values continued to rise after the argatroban was discontinued and peaked 3 days later at 5.28 and 123.6 seconds, respectively. At this time her platelet count had improved from 139 × 10 3 /mm 3 to 543 × 10 3 /mm 3 . No additional warfarin was administered before discharge. On hospital day 11, the patient was discharged home with an INR of 4.12 and an aPTT of 67.1 seconds. Her aPTT and INR values remained elevated for 19 days after receiving her last dose of warfarin and for 20 days after argatroban discontinuation. She experienced no bleeding complications from these supratherapeutic coagulation parameters. She resumed treatment with warfarin as an outpatient and completed a 6‐month course of anticoagulation without further incident. Clinicians should be aware that coagulation parameters may remain elevated longer than expected after argatroban discontinuation in certain patients taking concomitant warfarin. Patients with liver dysfunction and obesity appear most likely to be affected.