Heparin Retention and Dispersion Following Injection of Locking Fluid in an Acute Hemodialysis Catheter: A Simulation Study

Heparin locking is used to maintain patency of acute hemodialysis catheters; however, unintended leakage of locking solution into the systemic circulation may increase bleeding risk. Ideally, locking solution would remain confined to the catheter lumen, maintaining patency while minimizing systemic anticoagulation, yet the mechanisms governing heparin retention and dispersion remain inadequately understood. Patient-specific computational fluid dynamics simulations incorporating non-Newtonian blood flow and species transport were performed using a microcomputed tomography-derived model of an acute dual-lumen hemodialysis catheter to evaluate the effects of injection rate, venous blood flow, and lock volume. Injection of the manufacturer-recommended 1.4 ml lock volume over durations of 0.5–5 seconds resulted in 13–16% (900–1100 U) of injected heparin entering the systemic circulation, yielding transient therapeutic systemic heparin concentrations. Rapid injections increased distal penetration of the locking solution and improved heparin retention (from 84% to 87%). Heparin clearance following injection occurred in two phases consisting of rapid early convective washout followed by prolonged slow diffusive clearance. Reducing lock volume substantially decreased systemic heparin exposure while preserving therapeutic intraluminal heparin concentrations. These findings provide mechanistic insight into catheter locking behavior and suggest that optimization of lock volume may reduce unintended systemic anticoagulation while maintaining catheter patency.