Continuous Replacement Therapies

Continuous Renal Replacement Therapy (CRRT)

When patients requiring dialysis cannot tolerate a regular four-hour hemodialysis treatment usually due to hypotension, CRRT is now an option. CRRT can be used to treat an acute condition and it can be used as a “bridge” until the patient can tolerate conventional hemodialysis. CRRT actually describes four different therapies. At the Medical Center we exclusively use the PRISMA made by Gambro Healthcare, Inc. to deliver CRRT.

CVVHDF is the mode of CRRT that is usually ordered; the terms listed below are the continuous replacement therapies that can be delivered by the PRISMA. Ultrafiltration is the fluid that is actually removed from a patient during dialysis.

SCUF: Slow Continuous Ultrafiltration

Provides a maximum of 2000 ml/hr patient fluid removal (ultrafiltration), but “Slow Continuous” usually is more like 50–200; enough to keep the patient in a negative fluid balance. No replacement fluid is used.

 

CVVH: Continuous Veno-Venous Hemofiltration

Offers high volume ultrafiltration using replacement fluid which can be given pre-filter (pre-dilution) or post-filter (post dilution). The advantage of this therapy is that you increase removal of solutes because the replacement solution “carries” the solute across the membrane (removal by convection).
Maximum patient fluid removal = 1000 ml/hr.

 

CVVHD: Continuous Veno-Venous Hemodialysis

This mode increases solute removal by providing the concentration gradient associated with dialysate. The dialysate is ordered by the kidney specialist and is tailored to the patient's individual electrolyte needs. Dialysate is pumped at counter flow to the patient's blood to maximize solute removal. The maximum fluid removal rate (ultrafiltration) in CVVHD is 1000 ml/hr.

 

CVVHDF: Continuous Veno-Venous Hemodiafiltration

This is the mode that is most widely used here at the Medical Center. This mode offers solute removal by diffusion and convection simultaneously, and patient fluid removal. Replacement fluid is added to the patient's blood either pre-filter (pre-dilution) or added post filter (post-dilution). As the replacement fluid is removed, it carries solutes across the membrane (convection). Solutes are also removed by the concentration gradient that exists between the patient's blood and the dialysate (diffusion). The maximum patient fluid removal rate (ultrafiltration) in CVVHDF is 1000 ml/hr.

A Few Things About The Prisma

• Hemodialysis nurses are available 24/7 to help with problems and questions and can be reached at 6-3170 or after hours beeper; ask the operator to page the dialysis nurse on duty.
• The Prisma measures pressures in several areas. It is very sensitive to changes in access pressures and return pressures. Therefore, if a patient is log rolled and the lines or catheter kink, the machine will stop and give an audible alarm. Most of the time this can be corrected by muting, identifying the problem and restarting the treatment. Trouble shooting techniques are covered with the nurse during the initial setup of the Prisma. Troubleshooting tips are also found in chapter #6 of the Prisma System Operators Manual found on the back of every Prisma.
• The Prisma measure filter pressures. These pressures are useful because they let us know if the membrane is developing a clot.