Continuous renal replacement therapies (CRRT) have advantages over intermittent hemodialysis (IHD) in the treatment of critically ill patients with acute renal failure (ARF). These benefits include:
- Improved cardiovascular stability
- Improved tolerance to ultrafiltration, thereby enabling the removal of large obligatory fluid loads
- Ability to maintain excellent azotemia and solute control even in severely catabolic patients
Renal replacement therapies have been developed which, although not necessarily continuous, have therapeutic aims in common with CRRTs; these include lower solute clearances that are maintained for longer periods of time . In this topic review, such regimens will be collectively referred to by the umbrella term "prolonged (daily) intermittent renal replacement therapy" (PIRRT) [2,3], although the term "hybrid therapy" is also acceptable (figure 1) [4,5]. Other terms are used in the literature to refer to subsets of PIRRT, and include "sustained low efficiency (daily) dialysis" (SLEDD), "sustained low efficiency (daily) diafiltration" (SLEDD-f), "extended daily dialysis" (EDD), "slow continuous dialysis" (SCD), "go slow dialysis", and "accelerated venovenous hemofiltration" (AVVH).
PIRRT using a variety of machines are safe and convenient, providing excellent control of electrolytes and fluid balance. Urea kinetics follows single compartment models and the delivered dose of dialysis is high. Larger solute clearance is enhanced by concurrent use of high flux membranes and on-line diafiltration.
Hemodialyzer clotting is a common complication; available data indicate that monitoring the degree to which dialysate is saturated with urea may enable elective hemodialyzer or tubing changes and optimization of anticoagulation, prior to clotting of the extracorporeal circuit.