Effect of changes in dialytic frequency, duration and flow rates on solute kinetics and effective clearances.
ASN 30th Annual Meeting, San Antonio
J Am Soc Nephrol (Sep) 8:280A 1997
The authors assessed the effect of variations in HD frequency, duration and blood/dialysate flow rates on steady state concentration profiles of five surrogates: urea (U), creatinine (Cr), vitamin B12 (B12), inulin (I), and beta-2-microglobulin (beta-2 M). This was a simulation study with no patient data, using a variable-volume double-pool model, which was solved by numerical integration.
For each solute/regimen combination, the equivalent renal clearance (EKR: mL/min) was calculated as a dimensionless value normalized to the EKR obtained using a "standard" regimen which consisted of a 4-h session given 3x/week. The comparisons were:
- regimen A: 4-h sessions given 3x/week
- regimen B: 100 min sessions given 7x/week
- regimen C: 8-h sessions given 3, 5 or 7x/week
| EKR in ml/min | |||||
| Regimen | Urea | Creatinine | B12 | inulin | Beta-2 |
| 4-h 3/week | 13.4 | 10.9 | 6.85 | 3.36 | 1.72 |
| Relative Removal Ratios to Above | |||||
| 100-min daily | 1.05 | 1.05 | 1.12 | 1.13 | 1.05 |
| 8-h 3/week | 0.96 | 1.10 | 1.33 | 1.58 | 1.28 |
| 8-h 5/week | 1.58 | 1.83 | 2.20 | 1.58 | 1.73 |
| 8-h 7/week | 2.25 | 2.20 | 3.15 | 2.65 | 2.24 |
The conclusions of the study were, that short-time daily dialysis results in a 5-13% increase in effective small solute, middle molecule, and low-molecular weight protein (LMWP) removal; but that 8-h sessions given 3/week could match the clearance of short-time dailys dialysis and then some, with the best clearances obviously with even longer times spent on the machine.
Comment: The main problem with this work is that the treatments were assessed, not in patients but in a mathematical model. This model has been shown to predict the urea kinetics of standard hemodialysis reasonably well. However, it has never been validated for solutes other than urea. Neither has this model been shown to predict the kinetics of non-standard dialyses.
The results are as might be expected, short treatments have greater post- dialysis solute rebounds, and more frequent treatments remove more solute, especially if the total weekly treatment time is also increased. This paper does serve to illustrate the theoretical advantages of increasing dialysis frequency and/or duration. This is an area of increasing interest to nephrologists and I am looking forward to the results of proper clinical studies. (James Tattersall, M.D., United Kingdom)
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ASN 30th Annual Meeting, San Antonio
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