What is CRRT?
- A set of four different modalities which are used to slowly and gradually purify blood
- Slow continuous ultrafiltration (SCUF)
- Continuous Veno-Venous Hemofiltration (CVVH)
- Continuous Veno-Venous Hemodialysis (CVVHD)
- Continuous Veno Venous Hemodiafiltration (CVVHDF)
When is CRRT used?
- Patients with acute renal failure who is expected to quickly recover kidney function
- For patients that are being stablized prior to transfer to a center that performs intermittent dialysis
- Treatment of a toxin exposure or drug overdose
- How does CRRT differ from intermittent dialysis?
- Intermittent dialysis is performed several times a week for relatively short intervals
- CRRT is performed on a continuous basis
- Intermittent dialysis makes large corrections to the patient's blood in short periods of time
- In CRRT the patient's blood is continuously and gradually cleansed
- CRRT more closely approximates the function of a normal kidney
- By using convection and diffusion, CRRT can remove larger contaminants
- Intermittent dialysis is primarily a diffusive therapy
What is meant by convection and diffusion?
All blood purification in CRRT and intermittent dialysis is performed by first dividing a patient’s blood into many straw-like semi-permeable membranes. In intermittent dialysis, these straw-like semi-permeable membranes are bathed in dialysate. By adjusting the composition of the dialysate, substances can be made to enter or leave the blood. This process is called diffusion. Convection exposes the blood traveling within the straw-like semi-permeable membranes to a positive trans-membrane pressure resulting in fluid being pushed out of the blood and across the membrane. Toxins, electrolytes and other small molecules are carried with the fluid and discarded. The lost fluid is then replaced with a sterile balanced electrolyte solution. The advantage of convection is that larger molecules are removed. CRRT can utilize both convection and diffusion.