High Dialysate Calcium Concentration May Cause More Sympathetic Stimulus During Hemodialysis.

BACKGROUND/AIMS: Acute activation of sympathetic activation during hemodialysis is essential to maintain blood pressure (BP), albeit long-term overactivity contributes to higher mortality. Low heart rate variability (HRV), a measure of autonomic nervous system activity, and abnormal ankle-brachial index (ABI) are associated with higher mortality in patients on hemodialysis. In this study, we assessed HRV and ABI pre and post dialysis in incident patients on hemodialysis using high (1.75mmol/l) and low (1.25mmol/l) dialysate calcium concentration (DCa). METHODS: HRV was measured as the ratio between low frequency and high frequency power (LF/HF). Thirty patients (age 47±16 years, 67% men) were studied in two consecutive mid-week hemodialysis sessions. RESULTS: Mean BP variation was positive with DCa 1.75 and negative with DCa 1.25 [4.0 (-6.0, 12.2 mmHg) vs. -3.2 (-9.8, 1.3 mmHg); p=0.050]. Reduction of ABI from pre to post HD was related to higher sympathetic activity (p=0.031). The increase in LF/HF ratio was higher with DCa 1.75 (58.3% vs. 41.7% in DCa 1.75 and 1.25, respectively, RR 2.8; p=0.026). CONCLUSION: Although higher DCa is associated with better hemodynamic tolerability during hemodialysis, this occurs at the expense of increased sympathetic activity. Higher sympathetic activity was associated with a decrease of ABI during hemodialysis.

Hemodynamic behavior during hemodialysis: effects of dialysate concentrations of bicarbonate and potassium.

BACKGROUND/AIMS: Ultrafiltration that occurs during hemodialysis (HD) promotes profound alterations in a relatively short period of time. The dialysate content of bicarbonate (DBic) and potassium (DK) may have impact over intradialytic hemodynamics, which goes beyond ultrafiltration, and its impact was evaluated in a prospective cohort. METHODS: 30 patients under HD were submitted to hemodynamic assessment (HA) at the beginning and at the end of HD sessions, through a non-invasive method. Serum minus dialysate potassium concentration was expressed as K-Gap. Cardiac index (CI) and peripheral arterial resistance (PAR) variation (post-HD minus pre-HD) were expressed as ΔCI and ΔPAR. Dialysate content of sodium and calcium were expressed as DNa and DCa, respectively. RESULTS: Mean DNa, DK and DBic were, respectively, 136.4 ± 1.1, 2.1 ± 0.6 and 38.2 ± 2.1 mEq/L. In 15 patients, DCa was >1.5 mmol/L and in the other 15 patients ≤ 1.5 mmol/L. The K-Gap ranged from 1.4 to 5.1 mEq/l (median 3.0 mEq/L). There was a reduction in post-HD CI and systolic blood pressure (ΔCI = -0.72l/min/m(2) and -11.3±15.1mmHg, respectively, p<0.001 for both). Conversely, PAR increased (ΔPAR = 272dyn.s/cm(5), p<0.001). Lower post-HD CI was was associated to higher DBic (p=0.0013) and lower K-Gap (p=0.026). In multivariate analysis, ΔCI was dependent on DBic and K-Gap, whereas ΔPAR was dependent on dialysate calcium during HD. CONCLUSION: We confirmed that Na and Ca dialysate content exerts and important role on hemodynamic during HD. In addition, our findings pointed out that higher dialysate concentrations of bicarbonate and potassium promote lower cardiac performance at the end of hemodialysis session.

Reprocessing high-flux polysulfone dialyzers does not negatively impact solute removal in short-daily online hemodiafiltration.

There are no studies evaluating the impact of dialyzer reprocessing on solute removal in short-daily online hemodiafiltration (OL-HDF). Our aim was to evaluate the impact of dialyzer reuse on solute removal in daily OL-HDF and compare with that in high-flux short-daily hemodialysis (SDH). Fourteen patients undergoing a SDH program were included. Pre-dialysis and post-dialysis blood samples and effluent dialysate were collected in the 1st, 7th, and 13th dialyzer uses in SDH sessions and in daily OL-HDF sessions. Directly quantified small solute (urea, phosphorus, creatinine, and uric acid) total mass removal (TM(DQ)) and clearance (K(DQ)) were similar when the 1st, 7th, and 13th dialyzer SDH uses were compared with the 1st, 7th, and 13th daily OL-HDF uses. TMDQ and K(DQ) of small solutes were similar among analyzed dialyzer uses in SDH sessions and in daily OL-HDF sessions. ß2-Microglobulin TM(DQ) and K(DQ) were statistically higher in daily OL-HDF dialyzer uses than in the respective SDH uses. There was no difference in ß2-microglobulin TM(DQ) and K(DQ) among dialyzer uses in daily OL-HDF sessions or in SDH sessions. In daily OL-HDF, albumin loss was significantly different among dialyzer uses (P < 0.001), being lower in the 7th and 13th dialyzer uses than in the first use. Dialyzer reprocessing did not impair solute extraction in daily OL-HDF. ß2-Microglobulin removal was greater in daily OL-HDF than in SDH sessions, without significant differences in other solutes extraction. There was a significant reduction in intradialytic albumin loss with dialyzer reprocessing in daily OL-HDF sessions.