Preserving central blood volume: changes in body fluid compartments during hemodialysis.

The understanding of fluid changes during hemodialysis (HD is essential for reducing complications as well as efficacy of the procedure. Bioimpedance spectroscopy provides a non invasive method of measuring total body water (TBW), the distribution of intra (ICF) and extracellular (ECF) fluids, and their changes during HD. Segmental bioimpedance may be used to measure the same fluid shifts but from different body segments; the technique has previously been shown to com pare well with whole body measures. It is possible that fluid shifts occur differently in different body compartments during HD. Based on previous hemodynamic studies we postulated that during HD ultrafiltration (UF) the body attempts to preserve its central blood volume (cardiopulmonary circula tion plus great vessels), and thus fluid shifts would be greater from the periphery than from central compartments. To test this hypothesis, segmental bioimpedance (Xitron Technolo gies, San Diego, CA) was performed on 11 subjects undergoing HD where ECF and ICF values were obtained from the legs, arms and trunk before and after a period of UF. Blood volume change (ABV%) was also followed using an on-line optical hematocrit (Hct) sensor (Crit-Line monitor, In-Line Diagnostics, UT) where deltaBV% = deltaBV% = (1 - Hct1/Hct0) x 100 (Hct0 = baseline Hct; Hct1 = postultrafiltration Hct) The UF of 2.0 L +/- 0.79 L (M +/- SD) over 75 minutes was associated with a deltaBV% of -9.43% +/- 3.6% (M +/- SD), a significant (Student's paired t-test) reduction in total body (TB) ECF (p < 0.02), a weak correlation in reduction in TBW (p = 0.09) but not in TB ICF. The ECF reductions from the trunk, legs, and arms were all significant (minimum p < 0.02); no ICF changes from these compartments were significant. The amount of ECF reduction was greater from the legs (0.7 L +/- 0.6 L) than the arms (0.12 L +/- 0.08 L) and trunk (0.2 L +/- 0.2 L) (all M +/- SD). Multiple regression analysis showed that TB ECF changes correlated strongly with leg (r = 0.94, p < 0.001) and arm (r = 0.72, p = 0.002) ECF changes but not with trunk changes. deltaBV% correlated weakly with leg (r = 0.45, p = 0.08) and arm (r = 0.42, p = 0.10) ECF changes but not with the trunk. As the deltaBV% represents the net volume change between UF and plasma water refilling, thiss indicates that plasma water is being removed more from the peripheral compartments than from the trunk. These data suggest that plasma refilling during HD to preserve central blood volume is more dynamic from the leg ECF than from elsewhere and may, in turn, explain the frequent occurrence of leg cramps during and after hemodialysis.

Relationship between effective ionic dialysance and in vivo urea clearance during hemodialysis.

Effective ionic dialysance (EID) can be measured from dialyzer inlet and outlet conductivity changes following two steps of dialysate conductivity. Relationships between EID and in vivo urea clearances were studied four times per hemodialysis treatment in eight patients, each undergoing six hemodialysis treatments (192 data sets). Dialyzer blood flow was varied from 190 to 500 mL/min. Dialysate flow was constant (751 to 771 mL/min), and a standard dialyzer (700 HG; Cobe, Lakewood, CO) was used. Double samples were drawn for arterial, venous, and dialysate urea measurements. Two laboratory values were missing. Twelve unreliable laboratory values indicated by divergent results were excluded. Urea clearances were calculated by formulae converting whole-blood to blood-water urea clearances. EID was measured using Diascan (Gambro-Dasco, Medolla, Italy). Mass balance was checked by comparison of dialysate and blood-water urea clearances. Divergent results between dialysate and blood-water urea clearance values led to the exclusion of an additional three laboratory values. A small error (4.2%) in urea mass balance was found (dialysate greater than blood-water urea clearances). A total of 175 data sets were compared. EID showed excellent correlation with blood-water urea clearances (r = 0.92) over the line of identity, with a mean difference of -3.5 mL/min (-1%), and similarly with dialysate urea clearances (r = 0.92; mean difference, -13.4 mL/min; -5%). For both blood- and dialysate-side comparisons, differences increased with greater clearances. Because EID is an effective clearance and urea clearance is a measure of dialyzer clearance, the curves were corrected for cardiopulmonary recirculation; access recirculation was zero (Transonic monitor; Transonic Systems Inc, Ithaca, NY). For cardiopulmonary recirculation correction, cardiac output and access flows were assumed to be 6.4 L and 1.46 L/min. Corrected data show EID correlates with blood-side urea clearance (r = 0.92), with a mean difference of +7.3 mL/min (3.3%), and is constant over the range of clearances. EID correlated with dialysate urea clearance (r = 0.92) with virtually no difference. The difference on the blood side is consistent with the urea mass balance error found. These data indicate that EID using Diascan can provide an accurate indication of effective urea clearances obtained during hemodialysis and is of value in monitoring dialysis adequacy.

Flaxseed in lupus nephritis: a two-year nonplacebo-controlled crossover study.

OBJECTIVE: The objective of this study was to determine the renoprotective effects of ground flaxseed in patients with lupus nephritis. METHODS: Forty patients with lupus nephritis were asked to participate in a randomized crossover trial of flaxseed. Twenty-three agreed and were randomized to receive 30 grams of ground flaxseed daily or control (no placebo) for one year, followed by a twelve-week washout period and the reverse treatment for one year. At baseline and six month intervals, serum phospholipids, flaxseed sachet counts, serum creatinine, 12-hour urine albumin excretion and urine albumin to creatinine ratios, serum viscosity and plasma lipids were measured. RESULTS: There were eight drop-outs and of the 15 remaining subjects flaxseed sachet count and serum phospholipid levels indicated only nine were adherent to the flaxseed diet. Plasma lipids and serum viscosity were unaltered by the flaxseed supplementation whereas serum creatinine in the compliant patients during flaxseed administration declined from a mean of 0.97+/-0.31 mg/dL to a mean of 0.94+/-0.30 mg/dL and rose in the control phase to a mean of 1.03+/-0.28 mg/dL [p value <0.08]. Of the fifteen patients who completed the study, similar changes were noted [p value <0.1]. The nine compliant patients had lower serum creatinines at the end of the two-year study than the 17 patients who refused to participate [p<0.05]. Microalbumin at baseline declined in both control and flaxseed time periods, but there was a trend for a greater decline during flaxseed administration [p<0.2]. CONCLUSIONS: Flaxseed appears to be renoprotective in lupus nephritis, but this interpretation is affected by under powering due to poor adherence and potential Hawthorne effects.

Kt/V: patients do not get what the physician prescribes.

Monthly urea kinetic modeling is performed [service Kt/V (urea)] to ensure that dialysis prescriptions provide patients a Kt/V greater than or equal to 1 and yield a protein catabolic rate (PCR) greater than or equal to 0.8. The frequency with which the dialysis prescription (physician's order +/- 5%, p +/- 5%) was achieved was calculated by three methods: 1) CompuMod (3 ureas; computer derived), 2) Jindal-Goldstein, and 3) Daugirdas, (2 and 3% reduction of urea). Ten patients were followed serially over 1 month for a total of 120 dialyses. Mean Kt/V values for each method were: prescription, 1.54 +/- 0.36; service, 1.40 +/- t0.63; CompuMod, 1.33 +/- 0.27; Jindal-Goldstein, 1.55 +/- 0.24; and Daugirdas, 1.33 +/- 0.23. The percentages of dialyses within the p +/- 5% were 12.4%, CompuMod; 12.8%, Jindal-Goldstein and 14.3%, Daugirdas. The percentages above p +/- 5% were 20.4%, CompuMod; 47%, Jindal-Goldstein; and 21.4%, Daugirdas. The percentages below p +/- 5% were 67.3%, CompuMod; 40.2%, Jindal-Goldstein; and 64.3%, Daugirdas. The CompuMod and Daugirdas methods of assessment of Kt/V were significantly lower (p less than 0.001) than the prescribed Kt/V, whereas the Jindal-Goldstein estimate was not. The authors conclude that dialysis patients rarely achieve their prescribed Kt/V. The service Kt/V, therefore, is not a useful parameter for prescribing dialysis therapy. The CompuMod and Daugirdas methods are the best estimates of the Kt/V, while the Jindal-Goldstein equation overestimates the Kt/V. The need for frequent urea kinetic modelling is stressed. An online urea monitor for each dialysis would be the ideal solution.

The influence of dialysis membrane upon protein catabolic rate.

It has been hypothesized that the protein catabolic rate (PCR) is dependent upon the amount [Kt/V (urea)] and the type of dialysis (synthetic vs. cellulosic membrane). In an ongoing multicenter study comparing short hour-high flux with conventional cellulosic dialysis, 49 patients have completed 6 months and serial urea kinetic data has been obtained. Of the 49, 28 were on AN69S membrane dialyzers, and 21 on cellulosic. The patients on AN69S received significantly less Kt/V than those on cellulosic dialyzers (0.97 +/- 0.3 vs. 1.20 +/- 0.2; p = 0.0016), yet attained similar PCRs (1.07 +/- 0.2 vs. 1.02 +/- 0.1, NS). Significant (p = 0.002) linear relationships between PCR and Kt/V (urea) were found, yet the line slopes were higher for AN69S (average 0.46) than cellulose (average 0.25). Patients on AN69S achieve the same PCR for less Kt/V than patients on cellulosic dialyzers, supporting the hypothesis.

A multicenter study of short hour dialysis using AN69S. Preliminary results.

A multicenter prospective study of short hour (SH, less than or equal to 3 hr) dialysis using a high flux membrane (AN69S) plus volumetric control (VC), versus conventional (greater than or equal to 4 hr) (CNV) cellulosic non-VC dialysis, is ongoing. The study hypothesizes that SH treatment over 1 year will provide adequate dialysis, will not increase morbidity, and may improve quality of life. To date, 112 patients have been entered, and 54 have completed 6 months, 30 by SH. There were no differences in biophysiologic parameters at 6 months. Mean hospitalization was 5.24 days per patient. The SH group had a higher (p = 0.0374) hospitalization rate because of two patients. Quality of life was similar in SH and CNV groups. The study indicates that SH dialysis is feasible, safe, and as comfortable as CNV.

Urea monitoring during dialysis: the wave of the future. A tale of two cities.

The National Cooperative Dialysis Study (NCDS) suggested that the removal of small molecules controls the adequacy of the dialysis prescription, and it would seem appropriate that renal units regularly carry out formal urea kinetic modeling to ensure that the adequacy of dialysis is provided. Current methods of calculating Kt/V (urea) are complex and require the accurate measurement of dialyzer urea clearance and calculation of the volume of distribution of urea. This may be done by the direct measurement of total urea removed or by the use of computer programs that examine plasma urea and weight changes over time. Both methods have inherent problems, and this has stimulated the search for easier "bedside" formulas for the calculation of Kt/V. These newer formulas involve examination of the percentage reduction in blood urea concentration during hemodialysis. Two such formulas were examined and applied to 78 patients undergoing hemodialysis in two centers. One center routinely carried out formal urea kinetic modeling; the other did not. In the first center, it was found that the majority of patients were receiving more dialysis than necessary to achieve Kt/V (urea) = 1 when the latter was judged by those formulas. This suggested the possibility of time savings, with considerable implications for cost efficiency. In the second center, the majority of patients required more dialysis. It was concluded that intermittent formal urea kinetic modeling tends to overshoot the necessary prescription to allow for occasional "imperfect" dialyses and also that it is impossible to base dialysis prescriptions on routine pre-dialysis blood work and a "feel" for patients' needs.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship of depression to survival in chronic renal failure.

The authors examine the relationship between psychosocial factors and factors and survival of patients with chronic renal failure, while considering simultaneously the influence of parameters of physiologic functioning. Psychosocial and physiologic variables selected for discriminant analysis were extracted from data on 285 home-dialysis patients in Ontario, Canada. This analytical procedure defined which variables best discriminated between the survivor and nonsurvivor groups. The findings suggest that demographic and psychosocial factors may be more important than physiologic variables in determination of survival on home dialysis. The severity and type of depression is of particular importance to outcome.