Predilution haemofiltration - the Second Sardinian Multicentre Study: comparisons between haemofiltration and haemodialysis during identical Kt/V andsession times in a long-term cross-over study

Background. The potential superiority of various renal replacement treatmen t modalities consisting largely of convective mass transfer as opposed to p rimarily diffusive mass transfer, is still a matter of debate. The objectiv e of the present study was to evaluate acute and long-term clinical effects of varying degrees of convection and diffusion in a group of 24 clinically stable patients with end-stage renal disease. Methods. The patients were prospectively assigned to three consecutive trea tment schedules of 6 months each: phase I (HF1) ton-line predilution haemof iltration) --> phase II (HD) thigh-flux haemodialysis) --> phase III (HF2, as phase I). We used the AK100/200 ULTRA monitor (Gambro), which prepares u ltrapure dialysis fluid for HD and sterile, pyrogen-free substitution solut ion for HF. The membrane (polyamide), fluid composition, and treatment time were the same on HF and HD. The targeted equilibrated Kt/V was 1.2 for bot h treatment modes, creating a similar urea clearance. Results. Fifteen patients, mean age 62.8+/-8.4 years, completed the study a ccording to the above conditions. Urea kinetics, nutritional parameters, an d dry weight were similar in the three periods. The frequency of intra-trea tment episodes of hypotension/patient/month was significantly lower on HF1 (1.24) and HF2 (1.27) than on HD (1.80) (P < 0.04). It decreased progressiv ely on HF1, then increased on HD, and decreased again during HF2. Patients had fewer muscular cramps on HF than on HD (P<0.03) and required significan tly less saline and plasma expander during HF than HD sessions. The prevale nce of inter-treatment symptoms, including fatigue and hypotension, was low er on HF than on HD (score difference P=0.04). Quality of life, determined by the Laupacis method in all three periods, showed a tendency towards impr ovement during the study, reaching the best values during HF2. Conclusions. HF has a progressive stabilizing haemodynamic effect, producin g a more physiological cardiovascular profile than HD. This long-term effec t, observed in stable patients treated under strictly identical conditions, is probably due to the mechanism of convection, and is different from the acute effect observed mainly in unstable patients.