More may be less: increasing extracorporeal blood flow in an axillary arterio-arterial access decreases effective clearance.

Axillary arterio-arterial graft interposition has been described as a reasonable haemodialysis access in selected patients. In a patient with this unusual access, we measured and calculated effective clearance at different extracorporeal blood flows (Q(b)). Effective clearance increased with increasing blood flow and reached a maximum at a Q(b) of ~200 mL/min but then decreased when Q(b) was increased further. As this type of access typically provides low access flow, one has to be aware that local recirculation will easily occur. Therefore, a Q(b) above access flow has to be avoided since any increase beyond that threshold reduces effective clearance.