CRRT Circuit (Fig 3)
- Central double-lumen veno-venous hemodialysis catheter
- Extracorporeal circuit and filter (dialyzer)
- Blood pump
- Dialysate pumps
- Replacement fluid pump
The dialyzer is the main constituent of the circuit. It allows blood flow in
opposite direction to the dialysate solution (countercurrent), both
separated by a dialyzer membrane.
Membranes are made of synthetic and biocompatible materials designed
to filter unwanted molecules from the blood during dialysis. They are semi
permeable as they allow the selective clearance of small, medium or large
molecules size according to the size of its pores. A commonly used
membrane is the AN-69 is associated with hypotension due to bradykinin
release. Some propose the use of synthetic membranes such as
polyarylethersulfone (PAES) membranes to avoid this reaction. Other
biosynthetic membranes are made of polysulfone, polyamida,
polyacrylonitrile.
The dialysate pump regulates the pressure of the dialysate solution.
Although low pressures are preferred in the dialysate side of the system
