Since 1982, 32 uraemic patients were treated in our institution by high flux haemodiafiltration (H-HDF) in order to shorten significantly the dialytic treatment session. H-HDF used a high surface area filter (1.4-1.9 m2) with high hydraulic permeability (polyacrylonitrile and polysulfone), at high blood flow (450 ml/min) and high rates of reinfusion of substitution fluid (22 l/session). In this way the dialytic session was shortened to 140 +/- 19 min, maintaining a good cardiovascular stability and high dialytic efficiency (Kt/V > 1.1). Human recombinant erythropoietin rHuEpo introduced in the therapy of this group in 1987 has resulted in an improvement of renal anaemia, but also a prolongation of the time of dialytic treatment due to a decrease in the efficiency of filters. During the period of the study, the treatment time increased from 140 +/- 19 min to 168 +/- 25 min with a concomitant increase of haematocrit and haemoglobin (from 24% to 36% and from 7.9 to 10.5 g/dl, respectively). H-HDF maintains a noticeable increase in dialytic efficacy with good cardiovascular stability, but the goal of a significant reduction in the time of treatment can no longer be obtained.
Intermittent substitutive treatments in severely ill patients with acute renal failure are difficult or not suitable because of technical problems and/or hemodynamic instability. Continuous venovenous hemodiafiltration allows an adequate, slow removal of fluid, electrolytes, and waste products by combining diffusive and convective solute transport. Eight patients with acute renal failure, after cardiovascular surgery and cardiogenic shock, were treated by continuous venovenous hemodiafiltration. An automatic system (Equaline System, Amicon Division, USA) was employed. Venous accesses (femoral or subclavian) were used with double lumen catheters. A polysulfone filter (0.4 m2) was used in the study. Blood flow was 30 ml/min and dialysate flow rate 16.6 ml/min. Sterile pyrogen-free hemofiltration substitution fluid was used as dialysate. Mean duration of treatment was 10.3 +/- 3.2 days. After 72 hours blood urea nitrogen levels dropped from 136 +/- 46.13 to 53.5 +/- 12.3 mg/dl and creatinine levels dropped from 6.9 +/- 1.7 to 2.6 +/- 0.9 mg/dl. A controlled steady-state was then maintained. Mean urea clearance was 21 +/- 5.3 ml/min; mean ultrafiltration rate was 20.3 +/- 4.1 L/day. Continuous venovenous hemodiafiltration, with the Equaline System, is effective for the clearance of waste products and is able to maintain perfect fluid balance in catabolic patients with acute renal failure and multiple organ failure.
