Heparinization for routine hemodialysis.

Routine hemodialysis requires anticoagulation with heparin to prevent clotting in the extracorporeal circuit. Activated whole blood clotting times are used to measure the level of anticoagulation during dialysis. The magnitude of the clotting time obtained for a given level of heparin depends on the test used, and each dialysis unit must establish its own target range. The preferred dosage regimen for heparin is an initial loading dose, followed by a constant infusion. Dosage regimens based on intermittent boluses of heparin are associated with periods of under- and over-anticoagulation and require more staff attention during dialysis. Because patient responses to heparin differ markedly, the doses required to achieve suitable anticoagulation must be determined on an individual basis. The doses of heparin for an individual patient are best determined using a simple pharmacodynamic model, although they can be found empirically through trial and error. In spite of careful anticoagulation, an unsatisfactory outcome may still result. Patient-specific factors may be responsible for some of these adverse outcomes; however, in most cases they result from poor technique, including failure to deliver the prescribed dose of heparin, turbulence and foam formation in the extracorporeal circuit, and excessive access recirculation.