anticoagulation, is prescribed by dialysis doctors but delivered by dialysis nurses. The main agents used in clinical practice for anticoagulation during haemodialysis are unfractionated heparin (UF heparin) and low-molecular-weight heparin (LMWH). LMWH has a number of potential advantages, apart from cost. One of the most serious complications of the use of any form of heparin is heparin-induced thrombocytopaenia (HIT) Type II, which occurs more commonly with UF heparin than LMWH. HIT Type II selleck screening library risks severe morbidity and mortality and is challenging to treat successfully in both the acute and chronic phase. In HIT Type II anticoagulation must be delivered without heparin. A wide array of newer anticoagulants are becoming progressively available, each with unique advantages and disadvantages. In maintenance haemodialysis patients with an increased risk of bleeding, a ‘no heparin’ dialysis may be undertaken, or regional anticoagulation considered. Because this aspect of dialysis is so important to the safe and effective delivery of haemodialysis therapy, dialysis clinicians need to review and update their
knowledge of dialysis anticoagulation on a regular basis. The coagulation cascade is complex, multiply redundant and includes intricate checks and balances. While the complexity of the coagulation cascade has been well studied, most schemas simplify the cascade into two arms – the intrinsic pathway and the extrinsic pathway, meeting at factor X which is activated to Xa to
trigger the subsequent activation of prothrombin (factor II) to thrombin (factor selleckchem IIa), leading to the formation of fibrin from fibrinogen in the final common pathway.1 The intrinsic pathway is activated by damaged or negatively charged surfaces and the accumulation of kininogen and kallikrein. The activated partial thromboplastin time (APTT) tends to reflect changes in the intrinsic pathway. The extrinsic pathway is triggered by trauma or injury, which releases tissue factor. The extrinsic pathway is measured by the prothrombin test. Haemodialysis involves the circulation of whole blood through a dialysis circuit and artificial kidney (dialyser) both of which have the tendency to activate coagulation pathways. The dialyser is generally constructed of synthetic microfibres with narrow lumen, lacking endothelial Immune system lining and experiencing disordered flow – including both shear and turbulence. Factors that determine the thrombogenicity of different dialysis membranes include chemical composition, charge, ability to adhere or activate circulating cellular elements (including platelets) and other characteristics which activate thrombotic pathways.2 Studies suggest that cuprophane membranes may be more thrombogenic than polyacrylonitrile, which is more thrombogenic than polysulphone membranes and haemophan, with the least thrombogenic possibly being polyamide.