Effect of hemodiafiltration on measured physical activity: primary results of the HDFIT randomized controlled trial.

BACKGROUND: Dialysis patients are typically inactive and their physical activity (PA) decreases over time. Uremic toxicity has been suggested as a potential causal factor of low PA in dialysis patients. Post-dilution high-volume online hemodiafiltration (HDF) provides greater higher molecular weight removal and studies suggest better clinical/patient-reported outcomes compared with hemodialysis (HD). METHODS: HDFIT was a randomized controlled trial at 13 clinics in Brazil that aimed to investigate the effects of HDF on measured PA (step counts) as a primary outcome. Stable HD patients (vintage 3-24 months) were randomized to receive HDF or high-flux HD. Treatment effect of HDF on the primary outcome from baseline to 3 and 6 months was estimated using a linear mixed-effects model. RESULTS: We randomized 195 patients (HDF 97; HD 98) between August 2016 and October 2017. Despite the achievement of a high convective volume in the majority of sessions and a positive impact on solute removal, the treatment effect HDF on the primary outcome was +538 [95% confidence interval (CI) -330 to 1407] steps/24 h after dialysis compared with HD, and was not statistically significant. Despite a lack of statistical significance, the observed size of the treatment effect was modest and driven by steps taken between 1.5 and 24.0 h after dialysis, in particular between 20 and 24 h (+197 steps; 95% CI -95 to 488). CONCLUSIONS: HDF did not have a statistically significant treatment effect on PA 24 h following dialysis, albeit effect sizes may be clinically meaningful and deserve further investigation.

Effects of bone remodelling on calcium mass transfer during haemodialysis.

BACKGROUND: During haemodialysis, calcium balance can affect, or be affected by, mineral metabolism. However, when dialysate calcium concentration (d[Ca]) is chosen or kinetic models are employed to calculate calcium balance, bone remodelling is rarely considered. In this study, we examined whether bone remodelling affects calcium mass transfer during haemodialysis. METHODS: We dialysed 23 patients using a d[Ca] of 1.0, 1.25, 1.5 or 1.75 mmol/L. Calcium mass transfer was measured and associated with remodelling bone factors. RESULTS: Calcium balance varied widely depending on the d[Ca]. Calcium removal was -578 +/- 389, -468 +/- 563, +46 +/- 400 and +405 +/- 413 mg when a d[Ca] of 1.0, 1.25, 1.5 or 1.75 mmol/L was used, respectively (1.0 and 1.25 vs 1.5 and 1.75 mmol/L, P < 0.001; 1.5 vs 1.75 mmol/L, P < 0.05). Univariate analysis showed that calcium balance correlated with calcium gradient, parathyroid hormone (PTH), osteocalcin and dialysis vintage. Multivariate analysis revealed that calcium balance was dependent on calcium gradient, PTH and osteocalcin. CONCLUSIONS: These results suggest that bone remodelling could affect calcium mass transfer during haemodialysis.

Importance of the monthly biochemical evaluation to identify patients on hemodialysis with malnutrition.

INTRODUCTION: Malnutrition is a frequent complication in patients on hemodialysis and early diagnosis is important to reduce the morbidity and mortality of treatment. OBJECTIVE: To investigate the usefulness of biochemical tests performed monthly in order to identify hemodialysis patients with malnutrition. METHODS: The nutritional status of 252 patients was evaluated by objective and subjective global assessment, and the patients classified as malnourished and not malnourished. Then, during 4 consecutive months, serum creatinine, phosphorus, urea pre-and post-dialysis and Kt/V were recorded for calculation of averages. After analysis of these variables by the ROC curve we calculated the sensitivity and specificity of these parameters to identify patients with malnutrition. RESULTS: In ROC curve, the area under the curve for urea was 0.683, 0.71 for phosphorus, 0.724 for Kt/V and 0.765 for creatinine. For values of urea ≤ 90 mg/dL, phosphorus ≤ 4.2 mg/dL, Kt/V ≥ 1.6 and creatinine ≤ 6.5 mg/dL, the specificity ranged between 80% and 88% and sensitivity between 26% and 51%. The negative predictive value ranged between 90% and 92% and positive predictive value between 23% and 32%. The association of two or more of these índices did not change significantly these values. CONCLUSIONS: Our results suggest that serum urea ≤ 90 mg/dL, creatinine ≤ 6.5 mg/dL, phosphorus ≤ 4.2 mg/dL, and Kt/V ≥ 1.6 can be used for screening patients with malnutrition. However, using these cutoffs the parameters tend to overestimate the number of patients with malnutrition.

Characterization of acid-base status in maintenance hemodialysis: physicochemical approach.

Acidosis is a common and deleterious aspect of maintenance dialysis. Traditionally, it is considered to be an elevated anion gap acidosis caused by the inability to excrete nonvolatile anions. Stewart's approach made it possible to identify real determinants of the acid-base status and allowed quantification of the components of these disturbances, especially the unmeasured anions. We performed a cross-sectional study to identify and quantify each component of acidosis in hemodialysis maintenance patients. Sixty-four maintenance hemodialysis patients and 14 controls were enrolled in this study. Gasometrical and biochemical analysis were performed before the midweek dialysis session. Quantitative physicochemical analysis was carried out using the Stewart methodology. Hemodialysis patients were found to have mild acidemia (mean pH: 7.33 +/- 0.06 versus 7.41 +/- 0.05) secondary to metabolic acidosis (serum bicarbonate: 18.8 +/- 0.26 versus 25.2 +/- 0.48 mEq/l). The metabolic acidosis was due to retention of unmeasured anions (6.5 +/- 0.29 versus 3.1 +/- 0.62 mEq/l), hyperchloremia (105.1 +/- 0.5 versus 101.8 +/- 0.7 mEq/l), and hyperphosphatemia (5.90 +/- 0.19 versus 3.66 +/- 0.14 mg/dl). Compared with control values, the unmeasured anions and hyperchloremia had a similar acidifying effect (3.4 and 3.3 mEq/l), corresponding to almost 90% of the metabolic acidosis. Unmeasured anions and hyperchloremia are important components of acidosis in maintenance hemodialysis, in addition to phosphorus. Future studies to determine the etiology and consequences of hyperchloremic acidosis are warranted.