Approximately 10% of the critically ill patients required renal replacement therapy (RRT). 1 Continuous renal replacement therapy (CRRT) is the most commonly used RRT modality in critical care setting. 2,3 In order to maintain adequate patency of the extracorporeal circuit and the performance of the filter, anticoagulation is usually needed for CRRT. 4 However, critically ill patients are commonly associated with coagulation abnormalities, including thrombocytopenia, prolonged prothrombin time (PT), and activated partial thromboplastin time (APTT), and decreased antithrombin or protein C, which indicate high risk of bleeding. [5][6][7][8] The increased bleeding risk contributed to the hesitation of anticoagulant use for CRRT in clinical practice. A worldwide survey demonstrated that approximately one third of patients did not receive any anticoagulants during CRRT. 9 The Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline recommended CRRT without anticoagulation in patients with contraindication to citrate and increased bleeding risk. 10 Nevertheless, compared to circuits managed with anticoagulation, the averaged circuit lifespan of anticoagulation-free CRRT was significantly shorter. 11 Premature circuit failure due to clotting could lead to blood loss, decreased therapeutic efficacy, and increased medical workload and costs. 4,12,13 However, in some patients with prolonged APTT and/or thrombocytopenia, anticoagulation-free CRRT could proceed effectively. 14 The efficacy of anticoagulation-free CRRT