Samer R. Abbas - Academia.edu (original) (raw)

Papers by Samer R. Abbas

Journal of Applied Physiology, Jun 2, 2022

We found that fluid overload (FO) in patients with nondialysis CKD was largely underestimated by ... more We found that fluid overload (FO) in patients with nondialysis CKD was largely underestimated by clinical assessment compared with bioimpedance methods, which was majorly due to lack of appropriate techniques to assess FO. In addition, although degree of FO by bioimpedance markers positively correlated with the age in healthy subjects (HSs), no difference was observed in the three hydration markers between groups of 50 ≤ age <70 yr and age ≥70 yr in the patients with CKD.

Journal of Renal Nutrition, May 1, 2018

Physiological Measurement, May 22, 2017

BMC Nephrology, May 17, 2019

Nephrology Dialysis Transplantation, Jun 1, 2020

Background and Aims The aim of this study was to investigate relationship of glucose gradient dyn... more Background and Aims The aim of this study was to investigate relationship of glucose gradient dynamics with change in intraperitoneal volume (IPV) measured by segmental bioimpedance analysis (SBIA). Method Ten PD patients (age 59±8.8 years, 7 females, 5 Blacks, weight 69.8±12.4 kg) were studied during standard peritoneal equilibrium test (PET). Dialysate glucose concentration (D) was measured hourly throughout the PET. IPV was monitoring continuously using SBIA (Hydra 4200; Zhu et al, Kidney Blood Press Res 2019). Hourly IPV was used to calculate (1) the difference between two conservative hours (ΔIPVt = IPVt+1 - IPVt; t=0, 1, 2 and 3) and (2) the IPVt / IPV0 ratio vs. the concurrent Dt/D0. Results IPVs were successfully measured in nine patients (1 high transporter, 6 high-average, 2 low-average). Ultrafiltration volume (UFV, 0.55±0.17 L) at the end of dwell was measured by SBIA. ΔIPV1(0.26±0.17 L) was positive during the first hour of dialysate dwell in 7 patients, their corresponding ΔD1 (calculated as D1 – D0) was -902±278 mg/dL. However, 2 patients (1 high and 1 high-average transporter) showed negative ΔIPV1(-0.13±0.1 L) and a ΔD1 of -861±367 mg/dL. The relationship between IPVt/ IPV0 and Dt/D0 is shown in Fig.1 (a) – (i). The figures indicate the dynamics of IPV and glucose concentration changes in all 9 patients. Conclusion Peak IPV appears at different time points and is associated with different glucose gradients. These findings may represent specific, individual characteristics of the peritoneal membrane. Since first hour ΔIPV represents almost half of total UFV at the end of dwell, it could emerge as an important indicator of peritoneal membrane characteristics. Monitoring IPV using SBIA provides a useful tool for further investigation.

Journal of Applied Physiology

Nephrology Dialysis Transplantation, 2020

Kidney and Blood Pressure Research, 2019

Background: Ultrafiltration failure and fluid overload are common in peritoneal dialysis (PD) pat... more Background: Ultrafiltration failure and fluid overload are common in peritoneal dialysis (PD) patients. Knowledge of intraperitoneal volume (IPV) and time to peak IPV during a dwell would permit improved PD prescription. This study aimed to utilize trunk segmental bioimpedance analysis (SBIA) to quasi-continuously monitor IPV (IPVSBIA) during the peritoneal dwell. Methods: IPVSBIA was measured every minute using lower-trunk SBIA (Hydra 4200; Xitron Technologies Inc., CA, USA) in 10 PD patients during a standard 240-min peritoneal equilibration test (PET). The known dialysate volume (2 L) rendered IPVSBIA calibration and calculation of instantaneous ultrafiltration volume (UFVSBIA) possible. UFVSBIA was defined as IPVSBIA – 2 L. Results: Based on dialysate-to-plasma creatinine ratio, 2 patients were high, 7 high-average, and 1 low-average transporters. Technically sound IPVSBIA measurements were obtained in 9 patients (age 59.0 ± 8.8 years, 7 females, 5 African Americans). Drained ul...

Journal of renal nutrition : the official journal of the Council on Renal Nutrition of the National Kidney Foundation, Jan 18, 2017

This prospective study uses calf bioimpedance spectroscopy (cBIS) to guide the attainment of dry ... more This prospective study uses calf bioimpedance spectroscopy (cBIS) to guide the attainment of dry weight (DWcBIS) in chronic hemodialysis (HD) patients. The primary aim of this study was to evaluate whether body composition is altered when fluid status is reduced to DWcBIS. Target post-HD weight was gradually reduced from baseline (BL) until DWcBIS was achieved. DWcBIS was defined as the presence of both flattening of the curve of extracellular resistance and the attainment calf normalized resistivity in the normal range during the dialysis treatment. Extracellular volume (ECV), intracellular volume, and total body water (TBW) were measured using whole body BIS (Hydra 4200). Fluid overload, lean body mass, and fat mass were calculated according to a body composition model. Seventy-three patients enrolled and 60 completed the study (55 ± 13 years, 49% male). Twenty-eight patients (25% diabetes) achieved DWcBIS, whereas 32 patients (47% diabetes) did not. Number of treatment measuremen...

Physiological measurement, 2017

Normal fluid status (dry weight) can be identified by hydration markers established in the health... more Normal fluid status (dry weight) can be identified by hydration markers established in the healthy population. The general population average could be influenced by age with its accompanying physiological changes and/or illness. The aims of this study were (1) to evaluate the effect of age and systolic blood pressure (SBP) on these markers; (2) to compare mean values of hydration markers as assessed by different bioimpedance techniques. Subjects from the general population (n = 212, males 105, 57.1% White, 31.6% Black, and 11.3% others) were studied. Body weight, height and SBP were measured. Whole body and calf bioimpedance (Hydra 4200) methods were utilized with subjects in the supine position. Calf normalized resistivity (CNR), fluid overload (FO), extracellular (ECV) and intracellular (ICV) volume measurements ECV/total body water (TBW) were calculated. Subjects were stratified by age; young (Group1): 18-35 years; middle (Group2): 36-60 years, senior (Group3): 61-80 years. Bod...

In hemofiltration, performance of blood filters can be evaluated by the analysis of sieving coeff... more In hemofiltration, performance of blood filters can be evaluated by the analysis of sieving coefficients and clearances. Mainly for higher molecular weight uremic toxins (middle molecules) a decrease of dialyzer clearance may be expected depending on the duration of the extracorporeal renal replacement therapy. This study was designed to validate protein permeability of different blood filters at different times of treatment. Methods: Three hemodialysis filters (dialyzers) with different membranes (FX-60 ® polysulfone, Fresenius Medical Care), (Diacap HI PS 15 ® polysulfone, BBraun) and (BK-1.6P ® polymethlmethacrylate, Toray Industries) were examined during the first hour of a hemofiltration treatment. Filtrate samples were collected every 15 min applying different blood flow rates (125, 250, 300 ml/min). The ultrafiltration rate (UFR) was kept at 1000ml/h. Protein permeability of the membranes was evaluated by measurement of concentration of total protein, β2 microglobulin (β2M) a...

Prilozi / Makedonska akademija na naukite i umetnostite, Oddelenie za biološki i medicinski nauki = Contributions / Macedonian Academy of Sciences and Arts, Section of Biological and Medical Sciences, 2008

Since the beginning of maintenance haemodialysis many attempts have been made to quantify this ki... more Since the beginning of maintenance haemodialysis many attempts have been made to quantify this kind of renal replacement therapy. The most widely used methods are urea kinetic models and simple approximation formulae based on measured data of the individual patients. The most common term of dialysis dose is Kt/V. The errors of data put into the calculations are transferred to the result. Analysis of the error of the calculated result depending on the errors of the primary data using Gauss' law of progression of errors reveals errors of the calculated Kt/V between 7.7% and 18%. It is concluded that comparison of different groups of dialysis patients by means of Kt/V should only be done using one method with the least error.

Néphrologie & Thérapeutique, 2009

Journal of Renal Nutrition, 2015

Nephron. Clinical practice, 2014

Bioimpedance analysis (BIA) is well established to assess body composition. Agreements between si... more Bioimpedance analysis (BIA) is well established to assess body composition. Agreements between single- and multi-frequency bioimpedance (SF-BIA, MF-BIS) measurements in subjects undergoing 6 or 3 times/week hemodialysis (HD) were analyzed. Total body water (TBW) and intra- and extracellular fluid (ICF, ECF) of subjects enrolled in the Frequent Hemodialysis Network (FHN) Daily Trial (www.clinicaltrials.gov No. NCT00264758) were measured with a Hydra 4200 at baseline (BL) and at 5 months (M5). Volumes were computed using SF (at 50 kHz) and MF approaches. Agreement was assessed by means of linear regression and Bland-Altman analysis and treatment effects by t test. 35 subjects (17 on the more frequent regimen, 26 males, 20 African-American, 48 ± 9 years, pre-HD weight 84 ± 19 kg) were studied. Assessments with SF-BIA and MF-BIS correlated significantly at BL and M5 in both arms. No proportional errors, but systematic biases over the entire range of values were found at BL and M5. Agree...

Kidney and Blood Pressure Research, 2012

Background: In incident hemodialysis (HD) patients, the relationship between early systolic blood... more Background: In incident hemodialysis (HD) patients, the relationship between early systolic blood pressure (SBP) dynamics and mortality is unknown. Methods: Baseline SBP levels were stratified into 5 categories ranging from <120 and ≥180 mm Hg. Early pre-HD SBP change was defined as the slope of pre-HD SBP from week 1 to 12 and categorized in quartiles (Q1, lowest slope). SBP slopes were computed for each patient by simple linear regression. Results: In 3,446 incident HD patients (42% females, 44% black, age 62 ± 15 years), the median pre-HD SBP slope was –1.7 (Q1) to +2.3 (Q4) mm Hg/week. In an adjusted multivariate Cox regression analysis, patients with declining SBP (slope Q1) had higher mortality compared to patients with increasing pre-HD SBP (slope Q4) at 12 months (hazard ratio 2.01, 95% confidence interval 1.35–3.01). In addition, patients with baseline pre-HD SBP <120 mm Hg showed higher mortality compared to the reference group (SBP ≥180 mm Hg) at 12 months (hazard r...

Journal of Applied Physiology, 2014

This study explored divergence (error) between ultrafiltration volumes (UFV) and intradialytic ch... more This study explored divergence (error) between ultrafiltration volumes (UFV) and intradialytic changes in extracellular volume (ΔECV) in hemodialysis (HD) patients measured by whole body (wBIS) and sum of segmental bioimpedance spectroscopy (sBIS). The primary aim of the study was to evaluate the effect of different ultrafiltration rates (UFR) on error of estimation of ΔECV by changes in their distribution in body segments (arm, trunk, and leg). Forty-four HD patients (26 men, age 63.5 ± 14.3 yr) were studied twice in the same week following high and low UFR treatments. ΔECV and distributions (segmental ΔECV/∑segmental ΔECV, %) in arm, trunk, and leg were measured. ΔECV by wBIS underestimated UFV (0.58 ± 0.43 in high vs. 0.36 ± 0.5 liters at low UFR; P < 0.001, respectively); however, using sBIS no significant difference between UFV and ΔECV was present. Divergence using wBIS but not sBIS correlated positively with UFR. ΔECV distribution in trunk and leg at high UFR (44.1 ± 8.3, ...

Blood Purification, 2014

Background: Bioimpedance (BI) is maturing as a clinical technique for assessing fluid volume stat... more Background: Bioimpedance (BI) is maturing as a clinical technique for assessing fluid volume status. The aim of this study was to compare the sensitivity of four BI methods to detect changes in fluid status in hemodialysis patients. Methods: Forty-five patients were studied twice in the same week, i.e. once after the long and short interdialytic intervals, respectively. The four BI methods used were: (a) calf normalized resistivity (CNR) at a 5-kHz frequency, (b) whole-body multifrequency BI spectroscopy (MF-BIS) to estimate the normal hydration weight (NHWWBM), (c) whole-body MF-BIS to estimate the ratio of extracellular volume to total body water (wECV/wTBW), and (d) whole-body single-frequency (50 kHz) BI analysis to compute the ratio of ECV (sfECV) to TBW (sfTBW). Results: The relationship (slope of the regressive line) between relative changes (%) in the above mentioned four BI parameters and differences in weight (kg) was most pronounced with CNR (5.2 ± 1.6%/kg), followed by w...

Journal of the American Society of Nephrology, Nov 1, 2023