Grzegorz Wystrychowski

Application of Bioimpedance Techniques to Peritoneal Dialysis

Peritoneal dialysis (PD) has been used as a home dialysis therapy for renal replacement for more than 30 years. In a recent assessment of treatment quality, the mortality of patients on PD was referenced as being higher than of those on hemodialysis. Several reports suggest that a high proportion of PD patients are overhydrated. Clinical assessment of dry weight in PD patients is difficult and further complicated by the paucity of signs and symptoms indicative of dehydration (such as intradialytic hypotension or muscle cramps). Monitoring tools used for fluid status estimation during hemodialysis, e.g. online blood volume and blood pressure measurement, are not readily available in PD patients. Bioimpedance analysis technique has been considered as a potential tool to measure body fluid non-invasively, inexpensively and simply. Although Bioimpedance analysis has been used in clinical studies for more than 20 years, the knowledge of the electrical properties of body tissues is still evolving. In this review we aim to clarify the principles of different bioimpedance techniques and to introduce their applications in PD patients.

Size matters: body composition and outcomes in maintenance hemodialysis patients.

In hemodialysis patients a low body mass index (BMI) is correlated with an unfavorable clinical outcome, a phenomenon known as ‘reverse epidemiology’. Mechanisms underlying this observation are unclear. We propose the following: uremic toxin generation occurs predominantly in visceral organs and the mass of key uremiogenic viscera (gut, liver) relative to body weight is higher in small people. Consequently, the rate of uremic toxin generation per unit of BMI is higher in patients with a low BMI. Body water, mainly determined by muscle mass, serves as a dilution compartment for uremic toxins. Therefore, the concentration of uremic toxins is higher in small subjects. Uremic toxins are taken up by adipose and muscle tissues, subsequently metabolized and stored. Thus, the larger the ratio of fat and muscle mass to visceral mass, the lower the concentration of uremic toxins and the better the survival. To test this hypothesis, studies on uremic toxin kinetics in relation to body composition are needed.

Impact of switch of vascular access type on key clinical and laboratory parameters in chronic haemodialysis patients

BACKGROUND Observational studies demonstrate poor clinical outcomes in chronic haemodialysis patients with venous catheters as vascular access. This longitudinal study examines the impact of vascular access change on key clinical and laboratory parameters. METHODS We studied 2616 haemodialysis patients who had no or one vascular access change between January 2002 and June 2003. Two hundred and seventy-one patients switched from a catheter to an arteriovenous (AV) access (AV fistula or graft) and 69 patients from an AV access to a catheter. Accesses remained unchanged in 430 patients with catheters, and in 1846 patients with an AV access, who served as controls. Levels of serum albumin, white blood cell count (WBC), enPCR, eKdrt/V, blood haemoglobin and erythropoietin dosage were obtained monthly. Data were averaged over 6 months preceding (pre) and 6 months following the access change (post). Differences between post- and pre-access change were compared to changes in respective parameters between the last and first 6 months of the study period in controls. RESULTS The change from a catheter to an AV access was associated with a rise of serum albumin (+0.12 g/dL; P < 0.001), enPCR (+0.05 g/kg body weight/day; P = 0.001) and haemoglobin (+0.41 g/dL; P < 0.001) and a decrease in WBC (-370/microL; P = 0.048). Conversely, switching from an AV access to a catheter was followed by a significant fall in albumin (-0.11 g/dL; P = 0.035), enPCR (-0.07 g/ kg body weight/day; P = 0.001) and eKdrt/V (-0.09; P < 0.001) and a rise in erythropoietin dosage (+89 IU/kg body weight/week; P = 0.002), as compared to controls. CONCLUSION Change from a catheter to an AV access seems to alleviate malnutrition, inflammation and anaemia. Efforts to replace catheters with fistulae or grafts should be intensified.

Fluid dynamics during hemodialysis in relationship to sodium gradient between dialysate and plasma.

Fluid shifts during hemodialysis involve changes in both extracellular and intracellular volumes. This study aimed to determine the effect of intradialytic sodium gradients (GNa+), that is, the difference between dialysate and serum sodium concentration, on dynamics of extracellular and intracellular volumes in a group of maintenance hemodialysis patients. Extracellular volume change (deltaECV) between predialysis and postdialysis periods was determined by whole-body bioimpedance spectroscopy; intracellular volume change (deltaICV) was indirectly derived as the difference between deltaECV and the change in body weight, corrected for intradialytically given fluids. A total of 200 bioimpedance measurements were performed in 32 dialysis patients. Extracellular and intracellular volume changes were −2.6 ± 0.9 L (range: −4.7 to −0.5 L) and −0.2 ± 0.7 L (range: −2.5 to +1.5 L), respectively. There was a significant correlation between deltaICV and GNa+; deltaICV = −0.12 * GNa+ + 0.26 (p < 0.001). In contrast, GNa+ was not correlated with deltaECV. We conclude that the sodium gradient between dialysate and plasma has a significant effect on the ICV during dialysis. Hemodialysis with GNa+ = 0 mmol/L should be sought to prevent ICV shrinking or swelling and to prevent excessive thirst, consequently high interdialytic weight gains, and ultrafiltration rates.

Peritoneal dialysis as a mode of treatment for acute kidney injury in sub-Saharan Africa.

Background: Developing sustainable treatment programs for kidney failure in most countries of sub-Saharan Africa continues to remain an imposing challenge. While long-term renal replacement therapies in end-stage renal disease appear beyond national financial capabilities, there exist opportunities for a short-term and affordable treatment of acute kidney injury (AKI). Peritoneal dialysis (PD) is an effective and simpler modality compared to hemodialysis (HD) and can be performed without the need for machinery or electricity, making it an ideal choice in a low-resource setting. Methods: Since cost of treatment is the major obstacle, the goal is to develop a program that is cost effective. Developing an HD program requires a large capital investment by the hospital, needing water treatment systems and machinery and providing for their ongoing repair and maintenance. Gravity-driven PD is a simple, effective modality and can be performed in low-resource locales. Results: In a pediatric program that we started in the Komfo Anokye Teaching Hospital in Kumasi, Ghana, 28 patients have been treated with PD for AKI so far. Half of them were treated successfully and were discharged having fully recovered kidney function. Seven patients (25%) were determined to have end-stage renal disease, whereas 7 others (25%) died during hospitalization. In these cases, late presentation for dialysis may have contributed to the inability to recover. Conclusion: For individuals and governments alike, who are concerned about the cost of providing or paying for dialysis, using PD to treat AKI is an effective and simpler modality compared to HD and can be performed without the need for machinery or electricity, making it an ideal choice in a low-resource setting.

Selected climatic variables and blood pressure in Central European patients with chronic renal failure on haemodialysis treatment

Background/aims. Higher blood pressure (BP) in winter has been documented in healthy and hypertensive adults. It may potentially contribute to the observed excess winter cardiovascular mortality in the general population. The aim of the study was to assess whether BP varies similarly among patients with chronic renal failure on haemodialysis treatment, who present an increased risk of cardiovascular death. Methods. We retrospectively analysed values of pre‐dialysis BP and parameters of fluid retention – pre‐dialysis body weight and inter‐dialytic weight gain measured in 49 patients (23 male, 26 female; aged 46.0±13.5 years) from 1995 to 1998. For each patient we calculated deviations of monthly mean values of systolic BP, diastolic BP, pre‐dialysis body weight and inter‐dialytic weight gain from the lowest monthly means of these parameters in a given year. Monthly means of these deviations for the whole study group (dSBP, dDBP, dBW, dWG, respectively) were subsequently computed. Monthly means of air temperature (T), air relative humidity (H) and atmospheric pressure (AP) were provided by the local Institute of Meteorology. The Wilcoxon paired test was applied to compare mean values of BPs and parameters of fluid retention of every patient in three warmest and three coldest months of each year. Spearman rank correlation analysis was employed to evaluate relationships between dSBP, dDBP and climatic variables, dBW or dWG. Results. Systolic BP was higher in summer than in winter (146.6±20.5 vs 143.4±18.9 mmHg; p<0.00001). Diastolic BP was also higher in summer than in winter (82.6±8.5 vs 79.6±7.3 mmHg; p<10−9). Pre‐dialysis body weight and inter‐dialytic weight gain did not differ between summer and winter (66.0±13.2 vs 66.0±13.2 kg; p = 0.98 and 2.27±0.6 vs 2.29±0.5 kg; p = 0.53). There was a positive correlation between dSBP and T (RS = 0.424, p<0.003), as well as dDBP and T (RS = 0.591, p<0.00001) and an inverse correlation between dSBP and H (RS = −0.372, p<0.01), as well as dDBP and H (RS = −0.408, p<0.004). There were no significant associations between BPs and AP, dBW or dWG. Conclusions. In haemodialysed patients from southern Poland, BP is higher in summer than in winter. Changes in BP are related to seasonal changes in climatic variables – air temperature and air relative humidity. Seasonal variation in BP is not associated with variation in fluid retention. Possible alteration of cardiovascular reactivity to changes in climatic environment in haemodialysed chronic renal failure patients may be one of the potential explanations of these observations.

Nephroprotective Effect of Pentoxifylline in Renal Ischemia–Reperfusion in Rat Depends on the Timing of Its Administration

BACKGROUND Renal ischemia-reperfusion injury (IRI) induces inflammatory reaction damaging kidney. Pentoxifylline (PTX) given before IRI attenuates inflammation and prevents ischemic acute kidney injury (iAKI). Given that in clinical settings IRI is not always predictable, we aimed to assess whether PTX administration during or shortly after IRI affects the course of iAKI in the rat. METHODS In 58 male 10-week-old Sprague-Dawley rats, 14 days after right nephrectomy, a 45-minute clamping of solitary renal pedicle was conducted. PTX 100 mg/kg body weight or 0.9% NaCl 1 mL were given subcutaneously either 60 minutes before renal ischemia, 1 minute into ischemia, or 60 minutes after clamp release. Creatinine clearance (ClCr; mL/min/kg body weight), fractional excretions of sodium (FENa [%]) and potassium (FEK [%]), and urine protein/ClCr ratio (Uprot/ClCr [mg/1 mL ClCr]) at 48 hours after IRI were compared between PTX-treated animals and respective controls (Mann-Whitney U test). RESULTS Kidney function was improved in rats given PTX before IRI compared with controls: ClCr 2.10 ± 0.44 versus 1.03 ± 0.18; FENa 0.16 ± 0.12 versus 0.84 ± 0.55; FEK 40.3 ± 13.0 versus 75.5 ± 17.9, respectively (all P < .001). There was no difference in proteinuria: Uprot/ClCr 0.004 ± 0.002 versus 0.004 ± 0.002. Conversely, the analyzed parameters did not differ between animals administered PTX during IRI and controls: ClCr 0.42 ± 0.34 versus 0.73 ± 0.43; FENa 2.98 ± 2.71 versus 3.16 ± 3.05; FEK 280.1 ± 155.7 versus 206.2 ± 154.1; and Uprot/ClCr 0.031 ± 0.029 versus 0.029 ± 0.031, respectively, nor between rats given PTX after IRI and controls: ClCr 0.29 ± 0.38 versus 0.40 ± 0.47; FENa 4.25 ± 3.55 versus 3.80 ± 3.94; FEK 284.9 ± 117.5 versus 243.0 ± 150.6; and Uprot/ClCr 0.044 ± 0.018 versus 0.055 ± 0.061, respectively. CONCLUSIONS PTX given only before, and not at the time of renal ischemia or after reperfusion, alleviates subsequent iAKI in the rat. This implicates usefulness of PTX in the clinical settings of expected renal ischemia, like kidney transplantation, and suggests potential benefits of PTX in peritransplant period foremost with donor pretreatment.

Pentoxifylline and Methylprednisolone Additively Alleviate Kidney Failure and Prolong Survival of Rats after Renal Warm Ischemia-Reperfusion

Renal ischemia-reperfusion injury (IRI) induces local inflammation leading to kidney damage. Since pentoxifylline (PTX) and steroids have distinct immunomodulatory properties, we aimed to evaluate for the first time their combined use in IRI-induced acute kidney injury (AKI) and chronic kidney disease (CKD) in rats. In two experiments, PTX (100 mg/kg body weight subcutaneously) was administered 90 min prior to renal IRI or/and methylprednisolone (MP; 100 mg/kg body weight intramuscularly) was infused 60 min after reperfusion of a solitary kidney (AKI model: 45 min ischemia, 48 male Sprague-Dawley rats) or one kidney with excision of contralateral kidney 2 weeks later (CKD model: 90 min ischemia, 38 rats). Saline was infused in place of PTX or/and MP depending on the group. Renal function (diuresis, serum creatinine, creatinine clearance, sodium and potassium excretion, and urine protein/creatinine) was assessed at 48 h and 120 h post-IRI (AKI model) or 4, 16 and 24 weeks after IRI, along with survival analysis (CKD model). More evidently at early stages of AKI or CKD, treated animals showed higher glomerular filtration and diminished tubular loss of electrolytes, more so with PTX + MP than PTX or MP (serum creatinine (μmol/L) at 48 h of AKI: 60.9 ± 19.1 vs. 131.1 ± 94.4 vs. 233.4 ± 137.0, respectively, vs. 451.5 ± 114.4 in controls, all p < 0.05; and at 4 weeks of CKD: 89.0 ± 31.9 vs. 118.1 ± 64.5 vs. 156.9 ± 72.6, respectively, vs. 222.9 ± 91.4 in controls, p < 0.05 for PTX or PTX + MP vs. controls and PTX + MP vs. MP). Survival was better by >2-fold with PTX + MP (89%) vs. controls (40%; p < 0.05). PTX + MP largely protect from IRI-induced AKI and CKD and subsequent mortality in rats. This calls for clinical investigations, especially in kidney transplantation.

The correlation between LDL-cholesterol and arterial wall elasticity indices

BACKGROUND Elevated serum low-density lipoprotein cholesterol (LDL-C) concentration is a risk factor for atherosclerosis, which involves remodelling of the arterial walls with their subsequent stiffening. AIM We sought to evaluate the relationship between serum lipid levels and the elastic properties of the arterial wall. METHODS The study group comprised 315 men and women aged 55.84 ± 9.44 years. Serum glucose and lipid concentrations were determited. All subjects underwent blood pressure (BP) measurement, transthoracic echocardiography, and assessment of vascular compliance of large (C1) and small arteries (C2) using the HDI/Pulse Wave™ CR-2000 Research CardioVascular Profiling System (Hypertension Diagnostics Inc., Eagan, MN, USA). The subjects were divided into three groups: group I - LDL-C < 2.6 mmol/L, group II - LDL-C ≥ 2.6 mmol/L and < 4.0 mmol/L, and group III - LDL-C ≥ 4.0 mmol/L. RESULTS There were no intergroup differences with regard to smoking status (p = 0.56), serum glucose concentration (p = 0.13), body mass index (p = 0.96), systolic (p = 0.17) and diastolic BP (p = 0.29), or C1 (p = 0.09). However, C2 was higher in groups I and II than in group III (5.12 ± 2.57 vs. 5.18 ± 2.75 vs. 4.20 ± 1.58 mL/mmHg × 100, respectively, p < 0.01). Multivariate regression analysis negated the independent associations between C1 and serum lipid levels. In contrast, C2 was independently inversely associated with serum LDL-C concentration (r = -0.15, p < 0.01). CONCLUSIONS Higher serum LDL-C concentration seems to contribute independently to stiffening of small arterial vasculature in otherwise healthy adults. Screening for dyslipidaemia in the general population and its prompt treatment are highly recom-mended.