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Postdialytic rebound (PDR) of plasma solutes is a relevant drawback of intermittent hemodialysis, but its pathophysiological process remains undefined. We assessed the independent effects of efficiency and length of dialytic session on PDR of urea, phosphate, and potassium.Uremic patients were evaluated at the beginning and end of dialysis and after 180 minutes in 2 randomized crossover studies. In study 1, we compared the effect of standard versus higher efficiency acetate-free biofiltration (AFB) while maintaining the same duration of 4 hours. In study 2, we compared the effect of 3- versus 5-hour AFB sessions while maintaining similar efficiency.In study 1, greater Kt/V (1.49 +/- 0.20 versus 1.22 +/- 0.15; P0.0001) was coupled with significant increases in both absolute removal and PDR of urea and phosphate (PDR of urea, +45% versus +29%; PDR of phosphate, +79% versus +52%), but not of potassium. Similarly, in study 2, shortening the AFB session while maintaining similar absolute removal and Kt/V (1.28 +/- 0.09 versus 1.31 +/- 0.09) significantly increased PDR of urea and phosphate (PDR of urea, +32% versus +19%; PDR of phosphate, +63% versus +36%), but not of potassium. In both studies, greater PDRs of urea and phosphate were associated with estimated greater removal of these solutes per hour.The rate of removal of phosphate and urea is a critical determinant of their PDR; conversely, potassium is not influenced by removal rate, likely because of its marked cell compartmentalization.

Maximal suppression of renin-angiotensin system in nonproliferative glomerulonephritis. Background Elimination of residual proteinuria is the novel target in renoprotrection; nevertheless, whether a greater suppression of renin-angiotensin system (RAS) effectively improves the antiproteinuric response in patients with moderate proteinuria remains ill-defined. Methods We evaluated the effects of maximizing RAS suppression on quantitative and qualitative proteinuria in ten patients with stable nonnephrotic proteinuria (2.55 ± 0.94 g/24 hours) due to primary nonproliferative glomerulonephritis (NPGN), and normal values of creatinine clearance (103 ± 17 mL/min). The study was divided in three consecutive phases: ( 1 ) four subsequent 1-month periods of ramipril at the dose of 2.5, 5.0, 10, and 20 mg/day; ( 2 ) 2 months of ramipril 20 mg/day + irbesartan 300 mg/day; and ( 3 ) 2 months of irbesartan 300 mg/day alone. Results Maximizing RAS suppression was not coupled with any major effect on renal function and blood pressure; conversely, a significant decrement in hemoglobin levels, of 0.8 g/dL on average, was observed during up-titration of ramipril dose. The 2.5 mg dose of ramipril significantly decreased proteinuria by 29%. Similar changes were detected after irbesartan alone (-28%). The antiproteinuric effect was not improved either by the higher ramipril doses (-30% after the 20 mg dose) or after combined treatment (-33%). The reduction of proteinuria led to amelioration of the markers of tubular damage, as testified by the significant decrement of α 1 microglobulin (α 1 m) excretion and of the tubular component of proteinuria at sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Conclusion In nonnephrotic NPGN patients, standard doses of either ramipril or irbesartan lead to significant reduction of residual proteinuria and amelioration of the qualitative features suggestive of tubular damage. The enhancement of RAS suppression up to the maximal degree does not improve the antiproteinuric response and is coupled with a decrement of hemoglobin levels.

Maintenance hemodialysis (HD) patients were studied to assess the effect on hemoglobin (Hb) concentration induced by the cyclic variation in hydration status.Forty-nine HD patients were examined in three consecutive HD sessions in a 1-week treatment period. In a subgroup of 23 patients, Hb levels also were investigated during the long interdialytic interval.Hb levels at the end of the long interdialytic interval were significantly lower by 0.5 to 0.6 g/dL (5 to 6 g/L) than those at the end of short intervals. Among all pre-HD and post-HD Hb values, levels measured at the end of short intervals were closest to the mean Hb value of the week, derived from calculation of the area under the curve (12.0 +/- 0.2 g/dL [120 +/- 2 g/L]). Intradialytic Hb increments were different in the three sessions (+1.6 +/- 0.1 g/dL [+16 +/- 1 g/L] after the long interval, +1.1 +/- 0.1 g/dL [+11 +/- 1 g/L] and +1.1 +/- 0.1 g/dL [+11 +/- 1 g/L] after short intervals [P0.001] and proportionate to weight loss [-3.4 +/- 0.1, -2.7 +/- 0.1, and -2.6 +/- 0.1 kg, respectively; P0.001]). Hb level increment and weight loss correlated directly (r = 0.527; P0.0001); each 1 L of ultrafiltration (UF) led to an increase in Hb level of approximately 0.4 g/dL (4 g/L). Plasma refilling accounted for an approximately 45% decrement in the intradialytic increase in Hb level 2 hours post-HD.This study suggests that: (1) the end of the short interdialytic period is the most appropriate timing for anemia assessment, and (2) the remarkable hemodiluting effect of post-HD plasma refilling protects against excessive increments in Hb levels induced by UF.

To evaluate the role of plasma tonicity in the postdialysis increment of plasma potassium (p[K(+)]), the outcome of two hemodiafiltration treatments that differed only in the Na(+) level in dialysate (Na(D))-143 mmol/L (high dialysate sodium concentration [H-Na(D)]) and 138 mmol/L (low dialysate sodium concentration [L-Na(D)])-were compared in the same group of uremic patients from the end of treatment (T0) to the subsequent 30 to 120 min and up to 68 h. Kt/V and intradialytic K(+) removal were comparable. At T0, plasma [Na(+)] was 145+/-1 and 137+/-1 mmol/L after H-Na(D) and L-Na(D), respectively (P

To gain insights into postdialytic rebound of serum phosphate (PDR-P), serum phosphate (P), calcium (Ca), and parathyroid hormone (PTH), levels were compared from the end of treatment (T0) to the subsequent 30 to 120 min and up to 68 hr in uremic patients who underwent with crossover modality a single session of two dialytic treatments characterized by different convective removal: standard hemodialysis (HD) and hemodiafiltration (HDF). In HDF, versus HD, P removal was greater (1171 +/- 90 versus 814 +/- 79 mg; P < 0.05) in the presence of similar predialytic P levels (6.0 +/- 0.2 and 5.9 +/- 0.4 mg/dl) and Kt/V (1.35 +/- 0.06 and 1.34 +/- 0.05); however, the serum P values at T0 did not differ (3.0 +/- 0.2 versus 3.3 +/- 0.2 mg/dl). In HDF, PDR-P was more rapid (30 min versus 90 min) and of a greater extent (at T120: +69 +/- 6% versus +31 +/- 4%; P < 0.0001). The higher P levels were maintained throughout the interdialytic period. Ca x P and PTH changed in parallel. Thereafter, patients were randomized to receive either HD or HDF for 3 mo. During this period, in the presence of similar Kt/V, protein intake, and dose of phospate binder, predialytic serum P levels diminished in HDF (from 5.8 +/- 0.2 to 4.4 +/- 0.3 mg/dl; P < 0.05), but they remained unchanged in HD. A similar pattern of changes was detected in Ca x P. Therefore, PDR-P is likely dependent on the mobilization of phosphate from a deep compartment induced by the intradialytic removal of this solute. Enhancement of convective removal acutely amplifies the entity of the phenomenon but allows a better control of Ca-P homeostasis in the medium term.