the mortally rate is between 50% and 80%. Although the etiology of ARF varies, it is often associated with
a reduction in urine output and a drop in systemic blood pressure. Waste products accumulate
in the blood, electrolyte levels become abnormal, pH usually drops, and edema sets in.
Initially, ARF was treated in the same manner as chronic renal failure, with intermittent
hemodialysis. This approach quickly removes the metabolite, electrolyte, and fluid imbalance.
However, these levels vary widely because the body continuously generates their production
between dialysis sessions. Consequently, there has been a move toward continuous
renal replacement therapy (CRRT) (Galletti et al., 1995). In this mode, renal function is
supplied continuously while the patient recovers. There are several different CRRT modalities.
Historically, arterial circulation was used to provide the force to move blood across a
dialyzer cartridge. Because of the need for arterial access and inherent complications and
the technical improvement in venovenous therapies, these methods have been largely abandoned.
The venovenous modalities differ primarily in the methods of clearance. Slow continuous
ultrafiltration (SCUF) is a method employed to remove volume by taking off fluid
filtered by a dialysis membrane by convective force. Continuous venovenous hemodialysis
(CVVHD) provides clearance using diffusive clearance by running dialysate across the
membrane. Continuous venovenous hemofiltration (CVVHF) removes fluid by convection
(as in SCUF) and then provides replacement fluid back to the patient. Finally, continuous
venovenous hemodiafiltration combines the clearance properties of CVVHD and CVVHF.
These approaches are provided by bedside machines incorporating the required pumps,
control instrumentation, filters, and fluids.