Figure 196

Modalities for anticoagulation for continuous renal replacement therapy. While systemic heparin is the anticoagulant most commonly used for dialysis, other modalities are available. The utilization of these modalities is largely influenced by prevailing local experience. Schematic diagrams for heparin, A, and citrate, B, anticoagulation techniques for continuous renal replacement therapy (CRRT). A schematic of heparin and regional citrate anticoagulation for CRRT techniques. Regional citrate anticoagulation minimizes the major complication of bleeding associated with heparin, but it requires monitoring of ionized calcium. It is now well-recognized that the longevity of pumped or nonpumped CRRT circuits is influenced by maintaining the filtration fraction at less than 20%. Nonpumped circuits (CAVH/HD/HDF) have a decrease in efficacy over time related to a decrease in blood flow (BFR), whereas in pumped circuits (CVVH/HD/HDF) blood flow is maintained; however, the constant pressure across the membrane results in a layer of protein forming over the membrance reducing its efficacy. This process is termed concentration repolarization [10]. CAVH/CVVH—continuous arteriovenous/venovenous hemofiltra-tion. (From Mehta RL, et al. [11]; with permission.)

Solute Removal

Membrane

Middle molecules

Small molecules-

Membrane

Middle molecules

Small molecules-

Diffusion

Dialysate

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