Continuous Renal Replacement Therapy (CRRT)

The information contained in this page is intended for Singapore healthcare professionals only.

If your patient is critically ill with acute kidney injury (AKI), CRRT is one of the primary therapies. The goal of any continuous renal replacement therapy (CRRT) is to replace, as best as possible, the lost function of kidneys. CRRT provides slow and balanced fluid removal that even unstable patients - those with shock or severe fluid overload - can more easily tolerate. Both average and smaller size patients can undergo CRRT therapy and it can be adapted quickly to meet changing needs.

Principles of CRRT: Waste Management

Diffusion is used for removing small waste molecules (also known as solutes) during hemodialysis. In CRRT, blood flows through the hollow fibers of the dialyzer, and a cleansing fluid , known as a dialysate solution, flows in the opposite direction (See Image). This configuration maximizes the removal of wastes. Throughout this process, the waste molecules move from a higher concentration in the blood to a lower concentration in the dialysate.

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Convection, sometimes referred to as solvent drag, is used to remove both larger and smaller waste molecules. The difference in pressure between your blood and the replacement fluids (known as substitution solution), which creates a solvent drag for small and large waste molecules across the membrane. The solvent drag leads to the removal of waste from your blood. The faster the replacement fluid flows, the more waste is removed from your blood.

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Principles of CRRT: Fluid Management

Ultrafiltration uses positive pressure on the blood side of the membrane and negative pressure on the fluid side of the membrane to influence the movement of fluid. The gradient, positive to negative, results in fluid removal from the patient. The ultrafiltration rate depends on the pressure applied to the filter, inside and outside the fibers. Minimal waste removal happens by convection during ultrafiltration.

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Adsorption may cause limited removal of some waste from your blood. Membrane type affects adsorptive tendencies and effectiveness. High levels of adsorption can cause certain filters to clog and become useless.

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What types of CRRT are available?

CRRT includes several treatment types that use a venovenous access. Clinicians will examine the patient's injuries and can choose the option that best fits his or her specific needs and body tolerance level.


Therapeutic Plasma Exchange

TPE is performed on patients with a wide variety of rare diseases. With TPE, the blood is pumped through a plasma filter. Most of the plasma (a watery solution that forms the fluid of your blood) is removed and then replaced with fresh frozen plasma or albumin (a type of blood plasma protein). By replacing plasma, substances that threaten your body are removed.