Clotting in the dialysis circuit is triggered by both the extrinsic and the intrinsic pathways at the same time but to different degrees depending on the composition of the dialysis membrane and design and composition of the lines. Once the blood flow is initiated, plasma proteins deposit on the dialyser surface, and factor XII and high-molecular-weight kallikrein accumulate and act as initiating factors for contact coagulation
BAY 80-6946 – the Intrinsic Pathway. Peripheral blood leucocytes and monocytes, which contact the dialyser membrane, become adherent or activated and release blebs of surface membrane rich in tissue factor – activating the Extrinsic pathway. Platelets become activated by contact and in response to turbulent flow and high shear stress. The surface of platelets provides an enhancing environment promoting the interaction of coagulation cascade components. These triggers activate the clotting cascade, platelet aggregation, activation and degranulation, cytokine release and activation of circulating white cells, all of which can contribute in differing degrees to the triggering of or progressive activation GSK126 purchase of the clotting cascade leading to thrombosis in the dialysis circuit. Anticoagulation is routinely required to prevent clotting of the dialysis lines
and dialyser membranes, in both Carnitine palmitoyltransferase II acute intermittent haemodialysis and
continuous renal replacement therapies.5 As the field of anticoagulation is constantly evolving it is important to regularly review advances in knowledge and changing practices in this area.6 The responsibility for prescribing and delivering anticoagulant for haemodialysis is shared between the dialysis doctors and nurses. Dialysis is a medical therapy, which must be prescribed by an appropriately trained doctor. The prescribing doctor usually determines which anticoagulant agent will be used and the dosage range. The doctor’s prescription may include broad instructions such as ‘no heparin’, ‘low heparin’ or ‘normal heparin’. In a mature dialysis unit the dose and delivery of anticoagulant is, however, the responsibility of professional and experienced dialysis nurses, who have latitude within parameters determined by detailed written policies or standing orders. Dosing regimens, while generally safe and effective, are somewhat unscientific. In terms of monitoring, most units do not practise routine monitoring, although the anticoagulant effect of unfractionated heparin (UF heparin) can be monitored with some accuracy by the APTT or the activated clotting time tests where indicated. The dialysis nurses know there is too much anticoagulation if the needle sites continue to ooze excessively for a prolonged period (e.g. more than 15 min) after dialysis.