Assessment of the length of each hemodialysis session by on-line dialysateurea monitoring

Hemodialysis (HD) prescription is usually based on the periodical measureme nt of the Kt/V achieved in a midweek dialysis session. The purpose of the s tudy was to assess the duration of each HD session to achieve a target dose of dialysis. This allowed to determine whether a given dialysis session ma y be considered representative of the other HD sessions. Seventy-two HD ses sions were studied in 4 stable patients, who were randomly dialyzed during 3 consecutive periods, each lasting 2 weeks, using a different blood flow r ate (Qb) in each period: 400, 300 or 200 ml/min. All HD were prolonged to a chieve an on-line dialysate urea monitor (UM) Kt/V of 1.2. The UM Kt/V was compared with the Kt/V calculated using pre-HD, post-HD and rebound (45 min post-HD) plasma water urea concentrations. Comparison of the duration of t he second midweek dialysis session with the length of the other HD showed 9 5% concordance intervals (+/-2 SD) of +/-21.08 min for Qb 400, +/-26.88 min for Qb 300 and +/-37.02 min for Qb 200 ml/min. The 95% concordance interva ls for whole body urea clearance were +/-32.0, +/-20.36 and +/-15.62 ml/min for Qb 400, 300 and 200 ml/min, respectively. No differences were observed between UM Kt/V and blood-based double-pool Kt/V obtained by the second-ge neration Daugirdas (1.18 +/- 0.08) and Garred (1.19 +/- 0.08) Kt/V formulas . In conclusion, a great variability was observed between different HD sess ions with regard to the whole body urea clearance and the time required to attain a target Kt/V even when the HD characteristics remained constant. Th e length of every HD required to achieve a target dose of dialysis can be a ssessed by on-line dialysate urea. monitoring. Copyright (C) 2001 S. Karger AG, Basel.