Abstract
Hemodialysis aims at removing uremic toxins thus decreasing their concentrations. The present study investigated whether Kt/Vurea, used as marker of dialysis adequacy, is correlated with these concentrations. Predialysis blood samples were taken before a midweek session in 71 chronic HD patients. Samples were analyzed by colorimetry, HPLC, or ELISA for a broad range of uremic solutes. Solute concentrations were divided into four groups according to quartiles of Kt/Vurea, and also of different other parameters with potential impact, such as age, body weight (BW), Protein equivalent of Nitrogen Appearance (PNA), Residual Renal Function (RRF), and dialysis vintage. Dichotomic concentration comparisons were performed for gender and Diabetes Mellitus (DM). Analysis of Variance in quartiles of Kt/Vurea did not show significant differences for any of the solute concentrations. For PNA, however, concentrations showed significant differences for urea (P<0.001), uric acid (UA), p-cresylsulfate (PCS), and free PCS (all P<0.01), and for creatinine (Crea) and hippuric acid (HA) (both P<0.05). For RRF, concentrations varied for β2-microglobulin (P<0.001), HA, free HA, free indoxyl sulfate, and free indole acetic acid (all P<0.01), and for p-cresylglucuronide (PCG), 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF), free PCS, and free PCG (all P<0.05). Gender and body weight only showed differences for Crea and UA, while age, vintage, and diabetes mellitus only showed differences for one solute concentration (UA, UA, and free PCS, respectively). Multifactor analyses indicated a predominant association of concentration with protein intake and residual renal function. In conclusion, predialysis concentrations of uremic toxins seem to be dependent on protein equivalent of nitrogen appearance and residual renal function, and not on dialysis adequacy as assessed by Kt/Vurea. Efforts to control intestinal load of uremic toxin precursors by dietary or other interventions, and preserving RRF seem important approaches to decrease uremic solute concentration and by extension their toxicity.
Highlights
Failure of the kidneys is associated with the gradual retention of a myriad of solutes [1], causing an endogenous intoxication and failure of almost all organ systems [2,3]
We demonstrated in Chronic Kidney Disease (CKD) patients not yet on dialysis that estimated GFR, as the main currently used marker of renal function, was barely and inconsistently associated with concentrations of uremic toxins, the latter are associated with organ dysfunction [26,27]
The 71 chronic hemodialysis patients included were on thrice weekly hemodialysis for 38.0 (19.5– 61.5) months: 26/45 females/males, 28 diabetes mellitus, 31 with Residual Renal Function (RRF), age 72 (63.0–80.0) years, body weight 69.0
Summary
Failure of the kidneys is associated with the gradual retention of a myriad of solutes [1], causing an endogenous intoxication and failure of almost all organ systems [2,3]. Many strategic modifications have been introduced, such as large pore membranes, convection, frequent dialysis and extended dialysis. All these alternative strategies enhance solute removal [10,11,12,13,14,15,16] and have been associated with improved outcome [15,17,18,19,20,21,22,23], but do not necessarily increase Kt/Vurea [10,11,22,23]. The number of known uremic toxins has extended [24,25], mostly with compounds that are difficult to remove by standard dialysis
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