Is increased subjective thirst associated with greater interdialytic weight gains, extracellular fluid and dietary sodium intake?

BACKGROUND: Some previous studies have reported an effect of increasing subjective thirst and interdialytic weight gains (IDWG), and that this may be influenced by nonadherence to dietary sodium restrictions, whereas others reported no such association. As such we wished to review the effect of self-reported thirst on IDWGs and dietary sodium intake. METHODS: Dialysis patients were asked to complete visual analogues thirst, distress thermometer (DT) scores and complete a sodium food frequency questionnaire (SFFQ). IDWG and pre and post dialysis volumes were measured with multifrequency bioelectrical impedance. RESULTS: One hundred and eleven patients completed the questionnaires and had bioimpedance measurements: 63% male, mean age 63.8 ± 16.1 years, 33% diabetic with a median thirst score 3 (0-5) and SFFQ 52.0 ± 18, and IDWG 2.1 ± 1.3%. Thirst was associated with DT (r = 0.28, p = 0.004) and negatively with age (r = -0.31, p < 0.001), but not SFFQ, IDWG, extracellular water, or dialysate sodium, or dialysate to plasma gradient. Patients with higher thirst scores were younger (58.0 ± 15.2 vs. 69.4 ± 15.0 years, p < 0.001) with higher DT scores (5 [2-7] vs. 2 [0-5], p < 0.001). On multivariate logistic analysis, only age was associated with self-reported thirst (odds ratio 0.95, 95% confidence limits 0.92-0.98, p < 0.001). CONCLUSION: We found that subjective thirst was greater for younger patients and those who reported higher levels of distress, but no association with IDWGs, dietary sodium intake, or dialysate sodium. However, most of our patients followed the dietary advice, as evidenced by the low SFFQ scores and % IDWGs. Whether thirst increases distress or distress increases subjective thirst remains to be determined.

Calcium mass balance in adults during single hemodialysis and hemodiafiltration treatments using lower calcium dialysate concentrations.

BACKGROUND: Debate continues as to the optimum hemodialysis (HD) dialysate calcium concentration. Although current guidelines advocate 1.25-1.5 mmol/L, some investigators have suggested these may cause calcium gains. As such we investigated whether using dialysate calcium of 1.25 mmol/L risked calcium gains, and whether there were differences between hemodiafiltration and high flux HD. METHODS: We continuously collect an aliquot of effluent dialysate during dialysis sessions, and calculated dialysis calcium mass balance by the difference between the amount of calcium delivered as fresh dialysate and that lost in effluent dialysate. RESULTS: We studied 106 stable outpatients, 64% male, mean age 64.4 ± 16.2 years, median dialysis vintage 32 (22-60) months. Most sessions (69%) used a 1.0 mmol/L calcium dialysate, with a median sessional loss of 13.7 (11.5-17.1) mmol, whereas using 1.25 mmol/L the median loss was 7.4 (4.9-10.1) mmol, but with 6.9% had a positive balance (p = 0.031 vs dialysate calcium 1.0 mmol/L). Most patients (85.8%) were treated by hemodiafiltration, but there was no difference in sessional losses (11.7 (8.4-15.8) vs 13.5 (8.1-16.8)) with high flux HD. Dialysis sessional calcium balance was associated with the use of lower dialysate calcium concentration (ß -19.5, 95% confidence limits (95%CL) -27.7 to -11.3, p < 0.001), and sessional duration (ß 0.07 (95% CL) 0.03-012, p = 0.002). CONCLUSION: Ideally, the choice of dialysate calcium should be individualized, but clinicians should be aware, that even when using a dialysate calcium of 1.25 mmol/L, some patients are at risk of a calcium gain during hemodiafiltration and high-flux hemodialysis.

Impact of convective clearance on intra-dialytic potassium removal in chronic dialysis patients.

INTRODUCTION: Hyperkalemia is frequently encountered and associated with cardio-vascular mortality in chronic hemodialysis (HD) patients. While online hemodiafiltration (OL-HDF) is thought to offer clinical benefit over high-flux HD, the impact of convective clearance on intra-dialytic potassium removal is unknown. METHODS: Chronic dialysis patients undergoing outpatient HD or OL-HDF at a single center attached to a university hospital were recruited in a prospective observational study. Spent dialysate along with clinical and biological variables were collected during a single mid-week session. RESULTS: We included 141 patients, with 21 treated with HD and 120 with OL-HDF. Mean age was 65.7 ± 15.6 years with 87 (61.7%) men. Mean intra-dialytic potassium removal was 69.9 ± 34.2 mmol. Patients on OL-HDF and HD have similar intra-dialytic potassium removal, with mean values of 69.1 ± 34.2 and 74.3 ± 35.0, respectively. In multivariate analysis, factors associated with intra-dialytic potassium removal were (decreasing order of effect size): dialysate potassium (ß -15.5, p < 0.001), pre-HD serum potassium (ß 9.1, p < 0.001), and session time (ß 7.8, p = 0.003). In OL-HDF patients, substitution flow was not associated with potassium removal. CONCLUSION: In chronic dialysis patients, convective therapy provided by OL-HDF does not affect potassium removal when compared with high-flux HD. Moreover, the importance of convective volume is not associated with potassium clearance in OL-HDF. Overall, session length and serum-to-dialysate potassium gradient are the main determinants of potassium clearance regardless of dialysis modality. Those results should inform clinicians on the optimal therapy in chronic dialysis patients in the era of OL-HDF.

Prehemodialysis hyponatremia and extracellular water: Is it simply too much water?

Observational hemodialysis (HD) studies report an association between hyponatremia and increased mortality. As volume overload is also associated with mortality, we wished to determine whether hyponatremia is linked to increased extracellular water (ECW). We measured ECW, total body water (TBW) and body composition predialysis with multifrequency bioimpedance, arm strength with pinch gauge and hand grip strength (PS, HGS), standard biochemistry profiles, comorbidity and clinical frailty scores (CFS). We reviewed 324 patients, 195 (60.2%) male, mean age 62.3 ± 15.6 years. Thirty-eight (11.7%) patients were hyponatremic (sodium ≤135 mmol/L), ECW/height2 was not different, but ECW/TBW (0.409 ± 0.016 vs. 0.402 ± 0.016, p < 0.01), C reactive protein (CRP) (9(4-6) vs. 5(2-12) g/L, p < 0.05), CFS (5(4-6) vs. 4(3-6), p < 0.05) were higher in hyponatremic patients, whereas appendicular lean mass index (8.6 ± 1.7 vs. 9.4 ± 1.8 kg/m2, p < 0.01), serum albumin (36.3 ± 5.5 vs. 38.8 ± 5.0 g/L, p < 0.01) and PS (3.7(2.7-4.7) vs. 4.7 (3.2-6.5) kg, p < 0.05)) were lower. Both serum sodium, and serum sodium after adjustment for glucose were associated with serum creatinine (ß 4.26, (95% confidence limits [CL] 1.9-6.7), ß 3.98 (CL 1.6-6.4), both p = 0.001, respectively) and negatively with CRP (ß -0.76, [CL] -1.5 to -0.5), ß -0.72 (CL -1.44 to -0.12), p = 0.036, p = 0.046, respectively) in a multivariable model. Hyponatremic HD patients did not simply have an increased ECW, as the increased ECW/TBW and ECW/ICW ratios were more likely secondary to loss of muscle mass and strength, associated with increased CRP and reduced albumin, suggesting that hyponatremia is associated with inflammation, loss of muscle mass and increasing frailty.

Is there a therapeutic role for selenium in alpha-1 antitrypsin deficiency?

Selenium is an essential trace mineral of fundamental importance to human health. Much of its beneficial influence is attributed to its presence within selenoproteins, a group of proteins containing the rare amino acid selenocysteine. There are 25 known human selenoproteins including glutathione peroxidases, thioredoxin reductases and selenoproteins. Selenoprotein S (SEPS1) is an endoplasmic reticulum (ER) resident selenoprotein involved in the removal of misfolded proteins from the ER. SEPS1 expression can be induced by ER stress, an event that is associated with conformational disorders and occurs due to accumulation of misfolded proteins within the ER. Alpha-1 antitrypsin (AAT) deficiency, also known as genetic emphysema, is a conformational disorder in which the roles of ER stress, SEPS1 and selenium have been investigated. SEPS1 can relieve ER stress in an in vitro model of AAT deficiency by reducing levels of active ATF6 and inhibiting grp78 promoter- and NFκB activity; some of these effects are enhanced in the presence of selenium supplementation. Other studies examining the molecular mechanisms by which selenium mediates its anti-inflammatory effects have identified a role for prostaglandin 15d-PGJ2 in targeting NFκB and PPARγ. Together these ER stress-relieving and anti-inflammatory properties suggest a therapeutic potential for selenium supplementation in genetic emphysema.