Laboratory Monitoring of Heparin Anticoagulation in Hemodialysis: Rationale and Strategies

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs) are commonly used to prevent clotting of the hemodialysis extracorporeal circuit and optimize hemodialysis adequacy. There is no consensus on the optimal dosing for UFH and LMWHs during hemodialysis. In clinical practice, semiquantitative clotting scoring of the dialyzer and venous chamber may help to guide UFH and LMWH dose adjustment. Laboratory monitoring has not been shown to improve clinical outcomes and is therefore not routinely indicated in most hemodialysis patients. It might, however, be considered in select patients, such as those with extremes of body weight or history of repeated clotting or bleeding. Methods for laboratory monitoring include the activated partial thromboplastin time, activated clotting time, and antifactor Xa assays for UFH and antifactor Xa assay for LMWHs. Target ranges for anticoagulation in hemodialysis have been suggested but not clearly defined. When utilizing these tests, issues such as availability, standardization, interfering factors, and interpretation must be considered. In this narrative review, we discuss the rationale and methods of monitoring anticoagulation in hemodialysis.