title: Maintaining residual renal function in patients on haemodialysis: 5-year experience using a progressively increasing dialysis regimen.
abstract: BACKGROUND
  In contrast to patients treated with peritoneal dialysis, those on periodical haemodialysis (HD) do not receive programmed progressive increases in dialysis dosage, nor is residual renal function taken into account in the calculation of the total dialysis prescription; rather, only dialyser clearance is factored into the equation. In 2006, we decided to establish a progressively increasing dialysis regimen at the start of renal replacement therapy, evaluating the possibility of starting with 2 sessions of HD/week when renal clearance of urea was equal to or greater than 2.5 ml/min. This study summarises our experience during the first 5 years of application of this progressively increasing HD prescription and its repercussions on residual renal function.
  
  
  METHODS
  We included all patients who started periodical HD between 1/1/2006 and 30/9/2010 and remained on dialysis for more than three months. The follow-up period ended on 31/12/2010 (study end date). When a patient started HD, urea and creatinine clearance levels were measured based on urea and creatinine concentrations in blood samples taken before dialysis and in urine samples taken 24 hours prior to starting the first dialysis session of the week. If urea clearance was equal to or greater than 2.5 ml/min, 2 sessions of HD per week were applied, as long as the patient's clinical situation allowed for it (according to the criteria of the attending physician). Residual renal function was analysed every 2 months until diuresis was less than 100ml/day, which is considered to be basically null. We evaluated the decrease in residual renal function, calculating the rate of decrease in glomerular filtration (ml/min/month) and 24-hour diuresis (ml/month) in patients receiving 2 and 3 HD sessions per week. In January 2010, we took a cross-sectional sample, evaluating glomerular filtration and how this value was associated with various clinical and laboratory parameters in patients receiving 2 or 3 dialysis sessions per week.
  
  
  RESULTS
  During the study period, 95 patients were included in the study, 41 of which (43%) started with 2 HD sessions per week, and 54 (57%) with 3 sessions per week. The mean time that patients remained on the 2HD sessions/week regimen was 11.1 ± 7.2 months (range: 2-25 months). Of the 41 patients that started with 2 HD sessions/week, 10 received a transplant while on the treatment regimen, 1 was transferred to peritoneal dialysis, 6 recovered renal function and were able to abandon dialysis treatment, 15 were switched to the 3 HD sessions/week regimen, and 9 continued on the 2 HD sessions/week regimen at the time the study ended. Of the 15 patients that were switched to the 3 HD sessions/week regimen, 4 received transplants, 3 died, and the remaining 8 continued on HD until the end of the study. A Kaplan-Meier survival analysis revealed that patients who started on the 2 HD sessions/week regimen had a greater survival rate (log-rank: 3.964; P=.04). Losses in both glomerular filtration rate and 24-hour diuresis were lower in patients on the 2 HD sessions/week regimen: 0.22 ± 0.36 ml/min/month vs 0.89 ± 1.26 ml/min/month for glomerular filtration (P=.001), and 90.59 ± 132 ml/month vs 206.23 ± 286 ml/month for 24-hour diuresis (P=.001), respectively. In the cross-sectional sample taken in January 2010, 17 patients were on the 2 HD sessions/week regimen and 47 were on the 3 HD sessions/week regimen. Serum concentrations of β2-microglobulin were significantly lower in the 2 HD sessions/week group (19.7 ± 5 vs 38.3 ± 13; P=.000). The mean haemoglobin concentration was similar between the two groups, with a significantly lower dose required of erythropoietin in patients on the 2 HD sessions/week regimen (7058 ± 3749 units/week vs 12 553 ± 10 826 units/week; P=.037).
  
  
  CONCLUSIONS
  In select populations, the start of HD can be administered on a progressively increasing dosage, starting with two sessions/week. In our experience, this is a safe prescription that probably contributes to preserving residual renal function.
authors.affiliation: Servicio de Nefrología. Hospital Universitario Ramón y Cajal. Madrid, Spain. mfernandez.hrc@salud.madrid.org
authors.forename: Milagros
authors.initials: M
authors.lastname: Fernández-Lucas
authors.forename: José L
authors.initials: JL
authors.lastname: Teruel-Briones
authors.forename: Antonio
authors.initials: A
authors.lastname: Gomis-Couto
authors.forename: Javier
authors.initials: J
authors.lastname: Villacorta-Pérez
authors.forename: Carlos
authors.initials: C
authors.lastname: Quereda-Rodríguez-Navarro
mesh_terms: D005260:Female; D006801:Humans; D007668:Kidney / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis / Q000379:methods*; D013997:Time Factors