Protein-Bound Solute Clearance During Hemodialysis. In: Pokorski M, editor. Medical Science and Research. Cham: Springer International Publishing; 2019. pp. 69-77. [DOI: 10.1007/5584_2019_336]

Reduction of protein-bound uraemic toxins in plasma of chronic renal failure patients: A systematic review

BACKGROUND

Protein-bound uraemic toxins (PBUTs) accumulate in patients with chronic kidney disease and impose detrimental effects on the vascular system. However, a unanimous consensus on the most optimum approach for the reduction of plasma PBUTs is still lacking.

METHODS

In this systematic review, we aimed to identify the most efficient clinically available plasma PBUT reduction method reported in the literature between 1980 and 2020. The literature was screened for clinical studies describing approaches to reduce the plasma concentration of known uraemic toxins. There were no limits on the number of patients studied or on the duration or design of the studies.

RESULTS

Out of 1274 identified publications, 101 studies describing therapeutic options aiming at the reduction of PBUTs in CKD patients were included in this review. We stratified the studies by the PBUTs and the duration of the analysis into acute (data from a single procedure) and longitudinal (several treatment interventions) trials. Reduction ratio (RR) was used as the measure of plasma PBUTs lowering efficiency. For indoxyl sulphate and p-cresyl sulphate, the highest RR in the acute studies was demonstrated for fractionated plasma separation, adsorption and dialysis system. In the longitudinal trials, supplementation of haemodialysis patients with AST-120 (Kremezin®) adsorbent showed the highest RR. However, no superior method for the reduction of all types of PBUTs was identified based on the published studies.

CONCLUSIONS

Our study shows that there is presently no technique universally suitable for optimum reduction of all PBUTs. There is a clear need for further research in this field.

Renal Replacement Modality Affects Uremic Toxins and Oxidative Stress

Nowadays, the high prevalence of kidney diseases and their related complications, including endothelial dysfunction and cardiovascular disease, represents one of the leading causes of death in patients with chronic kidney diseases. Renal failure leads to accumulation of uremic toxins, which are the main cause of oxidative stress development. The renal replacement therapy appears to be the best way to lower uremic toxin levels in patients with end-stage renal disease and reduce oxidative stress. At this moment, despite the increasing number of recognized toxins and their mechanisms of action, it is impossible to determine which of them are the most important and which cause the greatest complications. There are many different types of renal replacement therapy, but the best treatment has not been identified yet. Patients treated with diffusion methods have satisfactory clearance of small molecules, but the clearance of medium molecules appears to be insufficient, but treatment with convection methods cleans medium molecules better than small molecules. Hence, there is an urgent need of new more validated, appropriate, and reliable information not only on toxins and their role in metabolic disorders, including oxidative stress, but also on the best artificial renal replacement therapy to reduce complications and prolong the life of patients with chronic kidney disease.

Alterations of body composition patterns in pre-dialysis chronic kidney disease patients

PURPOSE

Body mass index (BMI) might be an inaccurate estimate of detailed body composition because it does not differentiate muscle from fat mass. We sought to understand the effect of kidney function decline on alterations of body composition patterns among pre-dialysis CKD patients.

METHODS

Body composition was measured by multi-frequency bioelectrical impedance analysis (BIA). Low muscle mass was defined as appendicular muscle mass (kg) adjusted to the square of height in meters < 7.0 and 5.7 kg/m² in men and women, respectively. The designation of obesity by percent body fat was ≥ 25% in men and ≥ 30% in women. Alternative definition of obesity by BMI was ≥ 25 kg/m². Visceral fat area cut point was > 100 cm² as indication of abdominal obesity.

RESULTS

Mean age of participants was 61.3 ± 13.8 years (n = 103). The average glomerular filtration rate (GFR) was 34.0 ± 24.2 mL/min/1.73 m². By BIA, the prevalence of low muscle mass was 16.5% and was comparable between both sexes. Obesity by percent body fat was identified in 71.8% of patients and 38.2% had abdominal obesity. Using BMI criteria, the prevalence of obesity was less common (55.3%) and associated with under-identification of obesity by 27.0%. Low muscle mass and obesity by percent body fat were more prevalent in the more advanced stages of CKD. By multivariable regression analysis, a 10 mL/min/1.73 m² decline in GFR was associated with a 0.59 kg reduction of total body muscle mass (p = 0.01), but not fat mass or BMI, after adjusting for confounders.

CONCLUSION

Low muscle mass was prevalent among pre-dialysis CKD patients. BMI commonly classified obese CKD individuals by percent body fat criteria as non-obese. The reduction of muscle mass was associated with GFR decline.

Biocompatibility of Hemodialysis

This study was designed to investigate the biocompatibility of hemodialysis procedures, largely depending on the contact of patient's blood with the dialysis membranes. We addressed the issue by comparing the content of the proteolytic enzymes collagenase and cathepsin B and that of neutrophil myeloperoxidase (MPO) and C-reactive protein (CRP) in the blood before and after a single session treatment and a full course of successive 8-week-long therapies with three types of hemodialysis: low-flux (lfHD), high-flux (hfHD), and post-dilution hemodiafiltration (HDF). The study included 19 patients with chronic nephropathy. We found that collagenase significantly increased after a single session of each type of hemodialysis. Cathepsin B tended to decrease after single sessions; the decrease reached significance only after hfHD. CRP increased significantly after single hfHD and HDF treatments. These changes were meager, with no differences depending on the dialysis type, and their significance was lost after 8-week-long therapy, except the persisting increase in CRP after HDF. Neutrophil MPO apparently was not activated during any type of dialysis, as its content was below the detection threshold. We conclude that all three types of hemodialysis are compatible with the biological system, so that they would rather unlikely lead to clinically harmful effects in chronically hemodialyzed patients. Nonetheless, proteolytic enzymes and myeloperoxidase seem hardly appropriable estimators of hemodialysis biocompatibility due to meager and variable changes. Upregulation of C-reactive protein, on the other hand, expresses a general pro-inflammatory propensity of hemodialysis and is not a suitable estimator of biocompatibility either.