Fluid Overload and Tissue Sodium Accumulation as Main Drivers of Protein Energy Malnutrition in Dialysis Patients

Predictors of excess fluid volume in hemodialysis patients: an observational study

OBJECTIVES

to assess risk factors for excess fluid volume in hemodialysis patients.

METHODS

a retrospective case-control study was conducted. A total of 392 patients (196 cases and 196 controls) from two hemodialysis centers were included. Sociodemographic data and 23 risk factors for excess fluid volume were assessed using a data collection form. Data were analyzed using a multivariate logistic regression model.

RESULTS

the insufficient knowledge (OR=2.06), excessive fluid intake (OR=2.33), inadequate fluid removal during hemodialysis (OR=2.62) and excessive sodium intake (OR=1.91) risk factors may increase the chance of occurrence of excess fluid volume in hemodialysis patients by approximately two times. Education level (OR=0.95) and age (OR=0.97) are protective factors for excessive fluid volume.

CONCLUSIONS

knowing these risk factors may help nurses with accurate and rapid diagnostic inference of the risk of excessive fluid volume.

Effect of Dialysate and Plasma Sodium on Mortality in a Global Historical Hemodialysis Cohort

SIGNIFICANCE STATEMENT

This large observational cohort study aimed to investigate the relationship between dialysate and plasma sodium concentrations and mortality among maintenance hemodialysis patients. Using a large multinational cohort of 68,196 patients, we found that lower dialysate sodium concentrations (≤138 mmol/L) were independently associated with higher mortality compared with higher dialysate sodium concentrations (>138 mmol/L). The risk of death was lower among patients exposed to higher dialysate sodium concentrations, regardless of plasma sodium levels. These results challenge the prevailing assumption that lower dialysate sodium concentrations improve outcomes in hemodialysis patients. The study confirms that until robust evidence from randomized trials that are underway is available, nephrologists should remain cautious in reconsideration of dialysate sodium prescribing practices to optimize cardiovascular outcomes and reduce mortality in this population.

BACKGROUND

Excess mortality in hemodialysis (HD) patients is largely due to cardiovascular disease and is associated with abnormal fluid status and plasma sodium concentrations. Ultrafiltration facilitates the removal of fluid and sodium, whereas diffusive exchange of sodium plays a pivotal role in sodium removal and tonicity adjustment. Lower dialysate sodium may increase sodium removal at the expense of hypotonicity, reduced blood volume refilling, and intradialytic hypotension risk. Higher dialysate sodium preserves blood volume and hemodynamic stability but reduces sodium removal. In this retrospective cohort, we aimed to assess whether prescribing a dialysate sodium ≤138 mmol/L has an effect on survival outcomes compared with dialysate sodium >138 mmol/L after adjusting for plasma sodium concentration.

METHODS

The study population included incident HD patients from 875 Fresenius Medical Care Nephrocare clinics in 25 countries between 2010 and 2019. Baseline dialysate sodium (≤138 or >138 mmol/L) and plasma sodium (<135, 135-142, >142 mmol/L) concentrations defined exposure status. We used multivariable Cox regression model stratified by country to model the association between time-varying dialysate and plasma sodium exposure and all-cause mortality, adjusted for demographic and treatment variables, including bioimpedance measures of fluid status.

RESULTS

In 2,123,957 patient-months from 68,196 incident HD patients with on average three HD sessions per week dialysate sodium of 138 mmol/L was prescribed in 63.2%, 139 mmol/L in 15.8%, 140 mmol/L in 20.7%, and other concentrations in 0.4% of patients. Most clinical centers (78.6%) used a standardized concentration. During a median follow-up of 40 months, one third of patients ( n =21,644) died. Dialysate sodium ≤138 mmol/L was associated with higher mortality (multivariate hazard ratio for the total population (1.57, 95% confidence interval, 1.25 to 1.98), adjusted for plasma sodium concentrations and other confounding variables. Subgroup analysis did not show any evidence of effect modification by plasma sodium concentrations or other patient-specific variables.

CONCLUSIONS

These observational findings stress the need for randomized evidence to reliably define optimal standard dialysate sodium prescribing practices.

Nutritional Assessments by Bioimpedance Technique in Dialysis Patients

Bioelectrical impedance analysis (BIA) has been extensively applied in nutritional assessments on the general population, and it is recommended in establishing the diagnosis of malnutrition and sarcopenia. The bioimpedance technique has become a promising modality through which to measure the whole-body composition in dialysis patients, where the presence of subclinical volume overload and sarcopenic obesity may be overlooked by assessing body weight alone. In the past two decades, bioimpedance devices have evolved from applying a single frequency to a range of frequencies (bioimpedance spectroscopy, BIS), in which the latter is incorporated with a three-compartment model that allows for the simultaneous measurement of the volume of overhydration, adipose tissue mass (ATM), and lean tissue mass (LTM). However, clinicians should be aware of common potential limitations, such as the adoption of population-specific prediction equations in some BIA devices. Inherent prediction error does exist in the bioimpedance technique, but the extent to which this error becomes clinically significant remains to be determined. Importantly, reduction in LTM has been associated with increased risk of frailty, hospitalization, and mortality in dialysis patients, whereas the prognostic value of ATM remains debatable. Further studies are needed to determine whether modifications of bioimpedance-derived body composition parameters through nutrition intervention can result in clinical benefits.

Clinical Significance of Nutritional Status, Inflammation, and Body Composition in Elderly Hemodialysis Patients-A Case-Control Study

Nutritional and inflammatory disorders are factors that increase the risk of adverse clinical outcomes and mortality in elderly hemodialysis (HD) patients. This study aimed to examine nutritional and inflammation status as well as body composition in older adults on HD compared to matched controls. A case-control study was conducted on 168 older participants (84 HD patients (cases) and 84 controls) age- and sex-matched. Demographic, clinical, anthropometric, and laboratory parameters were collected from medical records. The primary outcome was nutritional status assessment using a combination of nutritional and inflammatory markers along with the geriatric nutritional risk index (GNRI). Sarcopenic obesity (SO) was studied by the combined application of anthropometric measures. Body composition and hydration status were assessed by bioelectrical impedance analysis (BIA). Univariate and multivariate regression analyses were performed to identify nutritional and inflammatory independent risk indicators in elderly HD patients and controls. A significantly high prevalence of nutritional risk measured by the GNRI was found in HD patients (32.1%) compared to controls (6.0%) (p < 0.001). Elderly HD patients were overweight and had lower percent arm muscle circumference, phase angle (PA), serum albumin (s-albumin), as well as higher percent extracellular body water (ECW%) and serum C-reactive protein (s-CRP) than controls (all at least, p < 0.01). SO was higher in HD patients (15.50%) than in controls (14.30%). By multi-regression analyses, age < 75 years (OR: 0.119; 95%CI: 0.036 to 0.388), ECW% (OR: 1.162; 95%CI: 1.061 to 1.273), PA (OR: 0.099; 95%CI: 0.036 to 0.271), as well as BMI, s-albumin ≥ 3.8 g/dL, and lower s-CRP were independently related between cases and controls (all at least, p < 0.05). Elderly HD patients had increased nutritional risk, SO, inflammation, overhydration, and metabolic derangements compared to controls. This study highlights the importance of identifying nutritional risk along with inflammation profile and associated body composition disorders in the nutritional care of elderly HD patients. Further studies are needed to prevent nutritional disorders in elderly HD patients.

Hyponatraemia and fluid overload are associated with higher risk of mortality in dialysis patients

BACKGROUND

The 5-year mortality rate for haemodialysis patients is over 50%. Acute and chronic disturbances in salt and fluid homeostasis contribute to poor survival and are established as individual mortality risk factors. However, their interaction in relation to mortality is unclear.

METHODS

We used the European Clinical Database 5 to investigate in a retrospective cohort analysis the relationship between transient hypo- and hypernatremia, fluid status and mortality risk of 72 163 haemodialysis patients from 25 countries. Incident haemodialysis patients with at least one valid measurement of bioimpedance spectroscopy were followed until death or administrative censoring from 1 January 2010 to 4 December 2019. Fluid overload and depletion were defined as >2.5 L above, and -1.1 L below normal fluid status, respectively. N = 2 272 041 recorded plasma sodium and fluid status measurements were available over a monthly time grid and analysed in a Cox regression model for time-to-death.

RESULTS

Mortality risk of hyponatremia (plasma sodium <135 mmol/L) was slightly increased when fluid status was normal [hazard ratio (HR) 1.26, 95% confidence interval (CI) 1.18-1.35], increased by half when patients were fluid depleted (HR 1.56, 95% CI 1.27-1.93) and accelerated during fluid overload (HR 1.97, 95% CI 1.82-2.12).

CONCLUSIONS

Plasma sodium and fluid status act independently as risk factors on mortality. Patient surveillance of fluid status is especially important in the high-risk subpopulation of patients with hyponatremia. Prospective patient-level studies should examine the effects of chronic hypo- and hypernatremia, risk determinants, and their outcome risk.