Impact of the nature of the capillary wall on plasma refilling during hemodialysis.

OBJECTIVES: Our aim was to clarify the impact of the nature of the capillary wall, defined by the contribution of large (LP), small (SP), and ultrasmall (UP) pores, on plasma refilling in a hemodialysis session. METHODS: This study included data from 78 patients. The relative blood volume change (ΔBV%) was monitored using a Crit-Line monitor. A bioimpedance device was used to measure extracellular and intracellular fluid volumes, and the excess fluid mass (MExF) was calculated. We simulated blood volume change (sΔBV%) based on a three-pore model. Hydraulic permeability of the capillary wall (LpS) and fractional contribution of LP to LpS (αLP) were determined by fitting sΔBV to ΔBV. The total refilling volume (TVref) was calculated from the total ultrafiltration volume and total blood volume change. Values were standardized to a body surface area of 1.73 m2 and are denoted by the subscript BSA. RESULTS: LpS and αLP were 3.09 (2.32, 4.68) mL/mmHg/min and 0.069 (0.023, 0.109), respectively. The standardized regression coefficient (ß) of the ultrafiltration rate (UFRBSA) and initial excess fluid mass (MExF,BSA,0) by multiple linear regression analysis of TVref,BSA without (Model 1) and with (Model 2) αLP were as follows: UFRBSA, 0.714/<0.001 (ß/p); MExF,BSA,0, 0.247/<0.001 (Model 1); UFRBSA, 0.799/<0.001; MExF,BSA,0, 0.066/0.237; and αLP, -0.327/<0.001 (Model 2). CONCLUSIONS: The impact of volume overload (MExF,BSA,0) on plasma refilling became insignificant with the addition of αLP in the model, suggesting that the nature of the capillary wall described by inter-endothelial gaps (LP) may have a greater impact on plasma refilling than volume overload.

Association of bioimpedance-derived 50-kHz phase angle as marker of body composition with electrical parameters regarding the Cole-Cole model.

Our aim is to clarify the association of the bioelectrical impedance-derived 50-kHz phase angle (φ50 ) with electrical parameters regarding the Cole-Cole model and clinical parameters. A total of 440 sets of bioelectrical impedance data from pre- and post-hemodialysis from 157 patients were used. Resistance at infinite frequency (Rinf ), resistance at 0 frequency (R0 ), capacitance of the cell membrane (Cm), and a parameter for the distribution of the time constant (α) were examined as electrical parameters. Normally hydrated lean tissue mass as a percentage of the dry weight (PNHLT ), excess fluid mass as a percentage of the dry weight (PExF ), body mass index (BMI), age, and sex (Nsex , 0 for male, 1 for female) were examined as clinical parameters. φ50 increased with the decrease in Rinf /R0 and α and also with the increase in Cm (multiple regression coefficients [ß]: pre/post, -0.886/-0.936, -0.175/-0.212, and 0.167/0.141), which determined the ratio of intra- to extracellular fluid volume (ICV/ECV), tissue homogeneity, and total cell mass. φ50 increased with an increase in PNHLT and BMI and decrease in PExF , Nsex , and age (ß: pre/post, 0.654/0.581, 0.466/0.412, -0.483/-0.473, -0.216/-0.154, and -0.145/-0.127). The concordance correlation coefficient between φ50 for pre- and post-hemodialysis (ρ = 0.772) may be improved (ρ = 0.950) by adding a multiplication of 0.2 and PExF to φ50 for correction. φ50 may be used to estimate body composition through the association with ICV/ECV, tissue homogeneity, and total cell mass. The correction for excess fluid is essential in order to use φ50 as a marker of body composition related to nutrition.

Patient-Specific Relationship Between Hydraulic Permeability of Microvasculature and the Extent of Burden of Excess Fluid in Hemodialysis Patients.

We have reported a significant correlation between hydraulic permeability of microvasculature adjusted with ultrafiltration rate (AdjLpst) and excess fluid divided by dry weight (ExF/DW) in a cross-sectional study of hemodialysis patients. We aimed to study longitudinally whether a similar relationship between them exists in each patient. Twelve hemodialysis (HD) patients in whom AdjLpst and ExF/DW had been measured more than four times (total of 85 measurements) were enrolled. AdjLpst was calculated by monitoring blood volume during HD. ExF was calculated from the fluid volume measured via bioimpedance spectroscopy. The borders of overhydration were 1.66 mL/mm Hg per min for AdjLpst and a positive value for ExF/DW. There was a significant correlation between AdjLpst and ExF/DW (r = 0.517). When the 85 measurements were classified into four quadrants according to ExF/DW and AdjLpst, the evaluations of fluid status agreed in 66 measurements. In six patients, significant positive correlations were found. In nine patients, equal to or more than 80.0% of evaluations by AdjLpst and those by ExF/DW agreed. In only one patient was there neither significant correlation nor agreement. AdjLpst of two patients suffering from chronic heart failure and microscopic polyangiitis was reduced compared with that of others loaded with the same extent of excess fluid. We concluded that there was a significant correlation between AdjLpst and ExF/DW and high agreement between evaluation by AdjLpst and evaluation by ExF/DW in the majority of patients. However, the relationship between them was patient-specific to some extent.

Evaluation of a pseudo-one-compartment model for phosphorus kinetics by later-phase dialysate collection during blood purification.

PURPOSE: Phosphorus removal is a major issue to assess for physicians engaging in hemodialysis. A pseudo-one-compartment model was reported as a novel model for phosphorus kinetics. We aimed to evaluate the adequacy of this model from the standpoint of the total mass of removed phosphorus during prolonged treatment. METHODS: Dialysate was collected during 6-h hemodialysis and hemodiafiltration treatment in 5 patients. Later-phase (from 4 to 6 h) dialysate was collected separately. Mobilization clearance (K(m)) and dialyzer clearance (K) were calculated by simple arithmetic operations utilizing stable serum phosphorus concentrations in this later phase. Volume of the accessible compartment (V(0)) was estimated by a fitting method. Amounts of removed phosphorus were calculated with these parameters and compared with measured values. The best sampling time points during treatment were also assessed, when the parameters were determined by serial serum phosphorus concentrations alone. RESULTS: Pearson's correlation coefficient (R) between calculated and measured values of removed phosphorus was 0.991 and the concordance correlation coefficient (ρ) was 0.987. When K(m), K and V(0) were determined by serial serum concentrations alone, including those at 0, 1, 4, and 6 h, the calculated mass of removed phosphorus had high R (0.974-0.975) or ρ (0.966-0.972) with the measured values. CONCLUSIONS: We confirmed that a pseudo-one-compartment model is useful for the estimation of removed phosphorus mass during prolonged blood purification by collecting dialysate. When the parameters are determined by a fitting method using serial serum concentrations alone, sampling at 0, 1, 4, and 6 h seems to be adequate.

Evaluation of endocrine disrupting activity of plasticizers in polyvinyl chloride tubes by estrogen receptor alpha binding assay.

Polyvinyl chloride (PVC) tubing is an indispensable medical material for extracorporeal circulation therapy. However, di(2-ethylhexyl)phthalate (DEHP), a suspected endocrine disruptor, can be eluted from PVC, suggesting that an alternative material that does not contain DEHP is needed for clinical applications. First, we evaluated the endocrine disrupting risks of the plasticizers contained in PVC tubes by investigating their binding affinities for the human estrogen receptor alpha (ERalpha). Our results revealed that, while DEHP has some binding affinity for ERalpha, neither epoxidized soybean oil nor tris(2-ethylhexyl)trimellitate (an alternative to DEHP) has any affinity for ERalpha. Second, we evaluated the endocrine disrupting risks of a tube made of newly developed plasticizer-free (PF) materials. We confirmed the presence of DEHP and detected several unidentified substances in plasma stored within the PVC tube. This plasma's competitive binding affinity for ERalpha was significantly higher than that of control plasma (P < 0.01). In contrast, the profile of plasma stored in the PF tube was similar to that of the control, both in terms of high-performance liquid chromatography chromatograms and competitive binding capacity for ERalpha, suggesting that the PF tube is biocompatible and is useful for reducing the elution of substances capable of binding to ERalpha.