Bioimpedance norms for the hemodialysis population

Associations between bioelectrical impedance analysis-derived phase angle, protein-energy wasting and all-cause mortality in older patients undergoing haemodialysis

AIM

Protein-energy wasting (PEW) is a common syndrome in patients undergoing haemodialysis (HD) and is associated with poor prognosis. Bioelectrical impedance analysis (BIA)-derived phase angle (PA) is useful for predicting PEW, but sex and age need to be considered. We aimed to reveal sex-specific cut-off values of PA predicting PEW in HD patients aged ≥65.

METHODS

This two-centre retrospective cohort study included patients on HD who underwent BIA. PEW was detected using the International Society of Renal Nutrition and Metabolism (ISRNM) criteria as a reference. The PA was measured using a multifrequency bioimpedance device. Sex-specific cut-off values of PA predicting PEW were detected by receiver-operator characteristic analysis. We investigated the association between PEW determined using sex-specific cut-off values for PA and all-cause mortality.

RESULTS

This study included 274 patients undergoing HD, with a median age of 75 (70-80) years, mean PA of 3.8 ± 1.1° and PEW of 43%. Over a median follow-up duration of 1095 (400-1095) days, 111 patients died. Cut-off values of PA predicting PEW were as follows: female, 3.00° (sensitivity, 87.3%; specificity, 77.5%), and male, 3.84° (sensitivity, 77.6%; specificity, 71.4%). The kappa coefficient between sex-specific cut-off values of the PA and ISRNM criteria had a moderate coincidence level of 0.55. PEW detected by PA was independently associated with all-cause mortality (hazard ratio: 2.40; 95% confidence interval: 1.51-3.85; p < .001).

CONCLUSIONS

Sex-specific cut-off values for PA in older HD patients may be useful as a screening tool for predicting PEW and mortality.

Muscle Mass and Serum Creatinine Concentration by Race and Ethnicity among Hemodialysis Patients

SIGNIFICANCE STATEMENT

Serum creatinine is a product of skeletal muscle metabolism. Differences in serum creatinine concentration between Black and non-Black individuals have been attributed to differences in muscle mass but have not been thoroughly examined. Furthermore, other race and ethnic groups have not been considered. If differences in body composition explain differences in serum concentration by race or ethnicity, then estimates of body composition could be used in eGFR equations rather than race. Adjustment for intracellular water (ICW) as a proxy of muscle mass among patients with kidney failure in whom creatinine clearance should minimally influence serum concentration does not explain race- and ethnicity-dependent differences.

BACKGROUND

Differences in serum creatinine concentration among groups defined by race and ethnicity have been ascribed to differences in muscle mass. We examined differences in serum creatinine by race and ethnicity in a cohort of patients receiving hemodialysis in whom creatinine elimination by the kidney should have little or no effect on serum creatinine concentration and considered whether these differences persisted after adjustment for proxies of muscle mass.

METHODS

We analyzed data from 501 participants in the A Cohort Study to Investigate the Value of Exercise in ESKD/Analyses Designed to Investigate the Paradox of Obesity and Survival in ESKD study who had been receiving hemodialysis for >1 year. We examined the independent associations among race and ethnicity (Black, Asian, non-Hispanic White, and Hispanic), serum creatinine, and ICW (L/m 2 ), a proxy for muscle mass, derived by whole-body multifrequency bioimpedance spectroscopy, using multivariable linear regression with adjustment for several demographic, clinical, and laboratory characteristics. We examined the association of race and ethnicity with serum creatinine concentration with and without adjustment for ICW.

RESULTS

Black, Asian, and Hispanic patients had higher serum creatinine concentrations (+1.68 mg/dl [95% confidence interval (CI), 1.09 to 2.27], +1.61 mg/dl [95% CI, 0.90 to 2.32], and +0.83 [95% CI, 0.08 to 1.57], respectively) than non-Hispanic White patients. Overall, ICW was associated with serum creatinine concentration (0.26 mg/dl per L/m 2 ICW; 95% CI, 0.006 to 0.51) but was not statistically significantly different by race and ethnicity. Black, Asian, and Hispanic race and ethnicity remained significantly associated with serum creatinine concentration after adjustment for ICW.

CONCLUSION

Among patients receiving dialysis, serum creatinine was higher in Black, Asian, and Hispanic patients than in non-Hispanic White patients. Differences in ICW did not explain the differences in serum creatinine concentration across race groups.

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.

Bioimpedanciometry in nutritional and hydration assessments in a single dialysis center

BACKGROUND

Bioimpedance analysis (BIA) has been demonstrated to add accuracy to nutritional and volume status assessments in dialysis (HD) patients.

AIM

to describe a sample of dialysis patients from a single center on their demographics and BIA of volume distribution and nutritional status, and mortality during 12-month follow-up.

METHODS

prospective observational cohort study to evaluate vintage HD patients with single-frequency BIA.

RESULTS

we evaluated 82 patients, 29% over 65 years old. Elderly patients had higher ECW/TBW (0.51 vs. 0.44, p < 0.0001), and narrower phase angle (PhA) (4.9 vs. 6.4º, p < 0.0001). Fifteen patients (18.2%) died during follow-up, eight (53%) were elderly. Death was associated with age (62.6 vs. 50.2 years, p = 0.012), post-HD PhA (4.8 vs. 6.2º, p = 0.0001), and post-HD ECW/TBW (0.50 vs. 0.45, p = 0.015). The ROC curve analysis to predict mortality found ECW/TBW ≥ 0.47 and PhA ≤ 5.5º to have the best sensitivity and specificity. One-year patient survival was lower with post-HD ECW/TBW ≥ 0.47 (69.5% vs. 90.6%, p = 0.019), age ≥ 65 years (64.2%, vs. 86.2%, p = 0.029), and PhA ≤ 5.5º (68.2 vs. 91.0%, p = 0.002). Cox regression analysis demonstrated that PhA [HR 5.04 (95%CI 1.60-15.86), p = 0.006] remained associated with death after adjusting for age and ECW/TBW.

CONCLUSION

BIA is useful in assessing volume distribution and nutrition in HD patients, and combined with clinical judgement, may help determine dry weight, especially in elderly patients. Narrower PhA and higher ECW/TBW after HD were associated with poorer one-year survival.

Bioimpedanciometria em avaliações nutricionais e de hidratação em um único centro de diálise

RESUMO Antecedentes: Análise de bioimpedância (BIA) demonstrou adicionar acurácia às avaliações de estado nutricional e de volume em pacientes em diálise (HD). Objetivo: descrever amostra de pacientes em diálise de um único centro quanto aos aspectos demográficos e BIA na distribuição de volume e no estado nutricional, e a mortalidade em 12 meses de acompanhamento. Métodos: estudo de coorte observacional prospectivo para avaliar pacientes prevalentes em HD com BIA de frequência única. Resultados: avaliamos 82 pacientes, 29% acima de 65 anos. Pacientes idosos apresentaram maior AEC/ACT (0,51 vs. 0,44; p < 0,0001), e ângulo de fase mais estreito (PhA) (4,9 vs. 6,4º; p < 0,0001). Quinze pacientes (18,2%) foram a óbito durante acompanhamento, oito (53%) eram idosos. Óbito foi associado à idade (62,6 vs. 50,2 anos, p = 0,012), PhA pós-HD (4,8 vs. 6,2º; p = 0,0001), e AEC/ACT pós-HD (0,50 vs. 0,45, p = 0,015). A análise da curva ROC para prever mortalidade constatou que AEC/ACT ≥ 0,47 e PhA ≤ 5,5º apresentam melhor sensibilidade e especificidade. Sobrevida do paciente em um ano foi menor com AEC/ACT pós-HD ≥ 0,47 (69,5% vs. 90,6%; p = 0,019), idade ≥ 65 anos (64,2% vs. 86,2%; p = 0,029), e PhA ≤ 5,5º (68,2 vs. 91,0%; p = 0,002). A análise de regressão de Cox demonstrou que PhA [HR 5,04 (IC 95% 1,60–15,86); p = 0,006] permaneceu associado ao óbito após ajuste para idade e AEC/ACT. Conclusão: BIA é útil ao avaliar distribuição de volume e nutrição em pacientes em HD, e juntamente com julgamento clínico, pode ajudar a determinar o peso seco, principalmente em pacientes idosos. PhA mais estreito e maior AEC/ACT pós-HD foram associados a pior sobrevida em um ano.

Prognostic value of phase angle and bioelectrical impedance vector in critically ill patients: A systematic review and meta-analysis of observational studies

BACKGROUND AND AIMS

Assessment of the raw parameters derived from bioelectrical impedance analysis (BIA) has gained emphasis in critically ill patients. The phase angle (PhA) reflects the integrity of the cell membrane, and bioelectrical impedance vector analysis (BIVA) is indicative of patients' hydration status. The aim of this study was to investigate whether these parameters are associated with clinical outcomes in the intensive care unit (ICU) setting.

METHODS

We conducted a systematic review with meta-analysis. We searched PubMed, Embase, Scopus and Web of Science for all published observational studies without language restrictions up to April 2022. Two reviewers independently performed study selection and data extraction. We judged the risk of bias by the Newcastle-Ottawa Scale and the certainty of evidence by the GRADE approach. Mortality was the primary outcome. Secondary outcomes included ICU length of stay, hospital length of stay, duration of mechanical ventilation, nutritional risk, and malnutrition. A meta-analysis with a random-effect model was performed to combine data on R version 3.6.2.

RESULTS

Twenty-seven studies were included in the systematic review (4872 participants). Pooled analysis revealed that patients with low PhA had a higher risk of death (14 studies; RR = 1.82, 95% CI 1.46 to 2.26; I² = 42%) and spent more days in ICU (6 studies; MD = 1.79, 95% CI 0.33 to 3.24, I² = 69%) in comparison to patients with normal PhA. The pooled analysis also showed higher PhA values in survivors compared to non-survivor patients (12 studies; MD = 0.75°, 95% CI 0.60° to 0.91°, I² = 31%). Overhydration defined by BIVA was not a predictor of mortality (4 studies; RR = 1.01, 95% CI 0.70 to 1.46; I² = 0%). More than 40% of primary studies were classified with a high risk of bias, and the quality of evidence ranged from low to very low.

CONCLUSIONS

This meta-analysis revealed, with limited evidence, that low PhA was associated with higher mortality and ICU length of stay, while overhydration identified by BIVA was not a predictor of death in critically ill patients.

The Extracellular Mass to Body Cell Mass Ratio as a Predictor of Mortality Risk in Hemodialysis Patients

The extracellular mass/body cell mass ratio (ECM/BCM ratio) is a novel indicator of nutritional and hydration status in hemodialysis (HD) patients. This study aimed to explore the ECM/BCM ratio as a predictor of mortality risk with nutritional-inflammatory markers in HD patients. A prospective observational study was conducted in 90 HD patients (male: 52.2%; DM: 25.60%). Clinical and biochemical parameters [serum albumin, serum C-reactive protein (s-CRP), interleukine-6 (IL-6)] were analysed and bioelectrical impedance analysis (BIA) was performed. Protein-energy wasting syndrome (PEW) was diagnosed using malnutrition-inflammation score (MIS). Based on BIA-derived measurements, the ECM/BCM ratio with a cut-off point of 1.20 was used as a PEW-fluid overload indicator. Comorbidity by Charlson index and hospital admissions were measured. Out of 90 HD patients followed up for 36 months, 20 patients (22.22%) died. PEW was observed in 24 survivors (34.28%) and all non-survivors. The ECM/BCM ratio was directly correlated with MIS, s-CRP, Charlson index and hospital admissions but was negatively correlated with phase angle and s-albumin (all, p < 0.001). Values of the ECM/BCM ratio ≥ 1.20 were associated with higher probability of all-cause mortality (p = 0.002). The ECM/BCM ratio ≥ 1.20, IL-6 ≥ 3.1 pg/mL, s-CRP and s-albumin ≥ 3.8 g/dL and Charlson index were significantly associated with all-cause mortality risk in multivariate adjusted analysis. This study demonstrates that the ECM/BCM ratio ≥ 1.20 as a nutritional marker and/or fluid overload indicator had a significant prognostic value of death risk in HD patients.

Impedance-derived phase angle is associated with muscle mass, strength, quality of life, and clinical outcomes in maintenance hemodialysis patients

INTRODUCTION

We aimed to evaluate the association between the phase angle and muscle mass, muscle strength, physical performance tests, quality-of-life scales, mood scales, or patient and hospitalization-free survival rates in hemodialysis (HD) patients.

METHODS

We included 83 HD patients. The patients were divided into tertiles based on phase angle value. The phase angle was measured using a bioimpedance analysis machine. Thigh muscle area per height squared (TMA/Ht2), handgrip strength (HGS), nutritional indicators, physical performance, quality-of-life, depression or anxiety status, and the presence of hospitalization or death regardless of cause were evaluated.

RESULTS

In our study, no significant differences were observed in the serum albumin level and body mass index according to tertiles of phase angle. The phase angle tertiles were associated with TMA/Ht2 and HGS. The phase angle was also associated with physical performance measurements and depression or anxiety status. Subgroup analyses according to sex, age, and diabetes mellitus showed similar trends to those of the total cohort. Furthermore, the hospitalization-free survival rate and patient survival rate were favorable in patients with high values for the phase angle.

CONCLUSION

The present study demonstrated that the phase angle is associated with muscle mass, strength, physical performance, quality-of-life scale, and hospitalization-free survival in maintenance HD patients.

Bioelectrical Impedance Analysis Derived-Phase Angle as a Pragmatic Tool to Detect Protein Energy Wasting among Multi-Ethnic Hemodialysis Patients

Protein-energy wasting (PEW) is a devastating metabolic derangement that leads to increased morbidity and mortality in hemodialysis (HD) patients. This study aimed to determine the diagnostic test accuracy of bioelectrical impedance analysis derived-phase angle (PhA) in detecting PEW among HD patients. This was a multi-centre, cross-sectional study conducted amongst 152 multi-ethnic HD patients in Klang Valley, Malaysia. PEW was assessed using the International Society of Renal Nutrition and Metabolism criteria as the reference method. PhA was measured using a multi-frequency bioelectrical impedance spectroscopy at 50 kHz. Multiple and logistic regressions were used to determine factors associated with PhA and PEW diagnosis, respectively. A receiver operating characteristics curve analysis was used to establish the gender-specific PhA cut-offs to detect PEW. PEW existed in 21.1% of the HD patients. PhA was found as an independent predictor of PEW (adjOR = 0.308, p = 0.001), with acceptable to excellent discriminative performance (adjAUC_male = 0.809; adjAUC_female = 0.719). Male patients had higher PhA cut-off compared to female patients (4.26° vs. 3.30°). We concluded that PhA is a valid and pragmatic biomarker to detect PEW in multi-ethnic Malaysian HD patients and a gender-specific cut-off is necessary, attributed to the gender differences in body composition.

Nutritional assessment and support during continuous renal replacement therapy

Malnutrition is highly prevalent in patients with acute kidney injury, especially in those receiving renal replacement therapy (RRT). For the assessment of nutritional status, a combination of screening tools, anthropometry, and laboratory parameters is recommended rather than a single test. To avoid underfeeding and overfeeding during RRT, energy expenditure should be measured by indirect calorimetry or calculated using predictive equations. Nitrogen balance should be periodically measured to assess the degree of catabolism and to evaluate protein intake. However, there is limited data for nutritional targets specifically for patients on RRT, such as protein intake. The composition of commercial solutions for continuous renal replacement therapy (CRRT) varies. CRRT itself can be associated with both, nutrient losses into the effluent fluid and caloric gain from dextrose, lactate, and citrate. The role of micronutrient supplementation, and potential use of micronutrient enriched CRRT solutions in this setting is unknown, too. This review provides an overview of existing knowledge and uncertainties related to nutritional aspects in patients on CRRT and emphasizes the need for more research in this area.

Time Stamp - A Novel Time-to-Digital Demodulation Method for Bioimpedance Implant Applications

Bioimpedance analysis is a noninvasive and inexpensive technology used to investigate the electrical properties of biological tissues. The analysis requires demodulation to extract the real and imaginary parts of the impedance. Conventional systems use complex architectures such as I-Q demodulation. In this paper, a very simple alternative time-to-digital demodulation method or 'time stamp' is proposed. It employs only three comparators to identify or stamp in the time domain, the crossing points of the excitation signal, and the measured signal. In a CMOS proof of concept design, the accuracy of impedance magnitude and phase is 97.06% and 98.81% respectively over a bandwidth of 10 kHz to 500 kHz. The effect of fractional-N synthesis is analysed for the counter-based zero crossing phase detector obtaining a finer phase resolution (0.51˚ at 500 kHz) using a counter clock frequency ( f_clk = 12.5 MHz). Because of its circuit simplicity and ease of transmitting the time stamps, the method is very suited to implantable devices requiring low area and power consumption.

Accuracy of surrogate methods to estimate skeletal muscle mass in non-dialysis dependent patients with chronic kidney disease and in kidney transplant recipients

BACKGROUND & AIMS

Bioelectrical impedance analysis (BIA) and anthropometric predictive equations have been proposed to estimate whole-body (SMM) and appendicular skeletal muscle mass (ASM) as surrogate for dual energy X-ray absorptiometry (DXA) in distinct population groups. However, their accuracy in estimating body composition in non-dialysis dependent patients with chronic kidney disease (NDD-CKD) and kidney transplant recipients (KTR) is unknown. The aim of this study was to investigate the accuracy and reproducibility of BIA and anthropometric predictive equations in estimating SMM and ASM compared to DXA, in NDD-CKD patients and KTR.

METHODS

A cross-sectional study including adult NDD-CKD patients and KTR, with body mass index (BMI) ≥18.5 kg/m². ASM and estimated SMM were evaluated by DXA, BIA (Janssen, Kyle and MacDonald equations) and anthropometry (Lee and Baumgartner equations). Low muscle mass (LowMM) was defined according to cutoffs proposed by guidelines for ASM, ASM/height² and ASM/BMI. The best performing equation as surrogate for DXA, considering both groups of studied patients, was defined based in the highest Lin's concordance correlation coefficient (CCC) value, the lowest Bland-Altman bias (<1.5 kg) combined with the narrowest upper and lower limits of agreement (LoA), and the highest Cohen's kappa values for the low muscle mass diagnosis.

RESULTS

Studied groups comprised NDD-CKD patients (n = 321: males = 55.1%; 65.4 ± 13.1 years; eGFR = 28.8 ± 12.7 ml/min) and KTR (n = 200: males = 57.7%; 47.5 ± 11.3 years; eGFR = 54.7 ± 20.7 ml/min). In both groups, the predictive equations presenting the best accuracy compared to DXA were SMM-BIA-Janssen (NDD-CKD patients: CCC = 0.88, 95%CI = 0.83-0.92; bias = 0.0 kg; KTR: CCC = 0.89, 95%CI = 0.86-0.92, bias = -1.2 kg) and ASM-BIA-Kyle (NDD-CKD patients: CCC = 0.87, 95%CI = 0.82-0.90, bias = 0.7 kg; KTR: CCC = 0.89, 95%CI = 0.86-0.92, bias = -0.8 kg). In NDD-CKD patients and KTR, LowMM frequency was similar according to ASM-BIA-Kyle versus ASM-DXA. The reproducibility and inter-agreement to diagnose LowMM using ASM/height² and ASM/BMI estimated by BIA-Kyle equation versus DXA was moderate (kappa: 0.41-0.60), in both groups. Whereas female patients showed higher inter-agreement (AUC>80%) when ASM/BMI index was used, male patients presented higher AUC (70-74%; slightly <80%) for ASM/height² index.

CONCLUSIONS

The predictive equations with best performance to assess muscle mass in both NDD-CKD patients and KTR was SMM-BIA by Janssen and ASM-BIA by Kyle. The reproducibility to diagnose low muscle mass, comparing BIA with DXA, was high using ASM/BMI in females and ASM/height² in males in both groups.

Prevalence of Malnutrition Assessed by Bioimpedance Analysis and Anthropometry in Children on Peritoneal Dialysis

Objective

To evaluate the sensitivity of anthropometry and bioelectrical impedance analysis (BIA) in detecting alterations in body composition of children treated with peritoneal dialysis (PD), and to determine the prevalence of malnutrition in this population, in short- and long-term PD duration, using anthropometric and BIA-derived indices.

Patients

Eighteen children treated with automated PD (11 males, 7 females; mean age 8.7 ± 4.7 years).

Design

Eighteen patients were studied using anthropometry and BIA at the start (t0) and after 6 months (t1) of PD, 15 of these patients at 12 months (t2), and 8 at 24 months (t3) of PD. Midarm muscle circumference (MAMC), arm muscle area (AMA), and arm fat area (AFA) were calculated from anthropometric measures according to Frisancho (FrisanchoAR. New norms of upper limb fat and muscle areas for assessment of nutritional status. Am J Clin Nutr 1981; 34:2540–5.). The bioelectrical measures of resistance (R) and reactance (Xc) were obtained directly from the impedance signal; phase angle (PA) and distance (D) were calculated using mathematical formulas. Nutritional status was assessed by anthropometric measurements and BIA-derived indices, expressed as standard deviation scores (SDS), and by a score system based on BIA and anthropometric parameters. The percentage of children with values of anthropometric and BIA-derived indices below the 3rd percentile or between the 3rd and 25th percentiles, and the percentage of children with scores of 7 – 12 and 4 – 6 were calculated in order to detect patients with severe or moderate derangement of nutritional status.

Results

The mean SDS values of Xc, PA, and D significantly improved ( p = 0.05, p = 0.001, p = 0.02) during the first 6 months of PD and remained almost stable during the following months. The SDS values of the anthropometric indices were less compromised than those of the BIA-derived indices, particularly at the start of dialysis. By 6 months, the percentages of children with values of BIA and anthropometric indices below the 3rd percentile had decreased. The percentages of patients with moderate and severe derangement of BIA and anthropometric indices remained substantially unchanged after 12 months. However, at 24 months, the percentage of patients with moderate derangement of BIA indices increased. All these findings were confirmed by the nutritional score system.

Conclusion

BIA is more sensitive than anthropometry in detecting alterations in body composition of children on PD. The prevalence of malnutrition, high at the commencement of PD, decreases during the first year of treatment but not over the long term.

Relationship of Demographic, Dietary, and Clinical Factors to the Hydration Status of Patients on Peritoneal Dialysis

Objectives

To establish which clinical factors are associated with an increased proportion of extracellular fluid (ECF) in peritoneal dialysis (PD) patients.

Design

A single-center, cross-sectional analysis of 68 stable PD patients.

Method

Bioelectrical impedance measurements (RJL, single frequency; RJL Systems, Clinton, Michigan, USA) of resistance and reactance were used to determine the proportion of ECF comprising total body water (TBW) in 68 stable PD patients attending for routine clearance and membrane studies. All patients underwent detailed dietetic, adequacy, and membrane function tests. Blood pressure and antihypertensive requirements were also documented.

Results

Significant gender differences in body composition were observed, such that women had lower absolute TBW and fat-free mass per kilogram body weight, but proportionately more ECF for a given TBW, mean ECF:TBW 0.5 ± 0.03 versus 0.44 ± 0.05, p < 0.005. In view of this, patients were split into two groups, defined as “over-” or “normally” hydrated, either by using the single discriminator (median ECF:TBW = 0.47) for the whole population, which resulted in groups distorted by gender, or by using different discriminators according to gender (women: 0.49, men 0.45). In both analyses, overhydrated patients were older, had significantly lower plasma albumin, less total fluid removal per kilogram body weight, and higher peritoneal solute transport. When split by a single discriminator, the overhydrated patients had lower sodium removal and significantly less intracellular fluid volume due to an excess of women in this group who also had less residual function and had been on dialysis longer. Using gender-specific discrimination, overhydrated patients were heavier due to expansion of the ECF volume: 20 ± 4.1 L versus 16 ± 3.3 L, p < 0.001. Stepwise multivariate analysis found age ( p = 0.001), albumin ( p = 0.009), and fluid losses per kilogram body weight ( p = 0.025) to be independent predictors of gender-adjusted hydration status. Sodium intake did not vary according to hydration status.

Conclusion

Gender influences the assessment of hydration status of PD patients when employing bioimpedance, such that women tend to have more ECF. Taking this into account, age, albumin, and achieved fluid removal appear to be independently associated with hydration status, whereas peritoneal solute transport is not. Advice on dietary sodium should take account of hydration status and achievable losses.

Association of sarcopenia with phase angle and body mass index in kidney transplant recipients

Malnutrition is an important risk factor for the development of sarcopenia. Recently, phase angle (PhA) obtained from the bioelectrical impedance analysis is increasingly becoming known as a nutritional status marker and may be considered a good indicator to identify elderly patients at risk of sarcopenia. In this study, we investigated the prevalence of sarcopenia and the relationship between sarcopenia and PhA or body mass index (BMI) as nutritional factors, and evaluated the discrimination performance of these nutritional factors for sarcopenia in 210 kidney transplant recipients. The median age was 55 years and 11.1% had sarcopenia. This prevalence of sarcopenia was lower than previous reports in kidney transplant recipients, maybe because of the differences in sarcopenia definitions and population demographics such as age, sex, race, and comorbidities. Both PhA and BMI were negatively correlated with sarcopenia after adjusting for age, sex, dialysis vintage, time after transplant, presence of diabetes mellitus, hemoglobin, estimated glomerular filtration rate, and the other nutritional factor. The discrimination performance for PhA and BMI had enough power to detect sarcopenia. These results suggest that PhA and BMI can be used in clinical practice to predict sarcopenia in kidney transplant patients.

Prevalence and predictors of depression among hemodialysis patients: a prospective follow-up study

BACKGROUND

Even though depression is one of the most common psychiatric disorders, it is under-recognized in hemodialysis (HD) patients. Existing literature does not provide enough information on evaluation of predictors of depression among HD patients. The objective of the current study was to determine the prevalence and predictors of depression among HD patients.

METHODS

A multicenter prospective follow-up study. All eligible confirmed hypertensive HD patients who were consecutively enrolled for treatment at the study sites were included in the current study. HADS questionnaire was used to assess the depression level among study participants. Patients with physical and/or cognitive limitations that prevent them from being able to answer questions were excluded.

RESULTS

Two hundred twenty patients were judged eligible and completed questionnaire at the baseline visit. Subsequently, 216 and 213 patients completed questionnaire on second and final follow up respectively. The prevalence of depression among patients at baseline, 2nd visit and final visit was 71.3, 78.2 and 84.9% respectively. The results of regression analysis showed that treatment given to patients at non-governmental organizations (NGO's) running HD centers (OR = 0.347, p-value = 0.039) had statistically significant association with prevalence of depression at final visit.

CONCLUSIONS

Depression was prevalent in the current study participants. Negative association observed between depression and hemodialysis therapy at NGO's running centers signifies patients' satisfaction and better depression management practices at these centers.

Extracellular mass to body cell mass ratio as a potential index of wasting and fluid overload in hemodialysis patients. A case-control study

BACKGROUND & AIMS

Extracellular mass-to-body cell mass ratio (ECM/BCM ratio) which differentiates the proportion between intraextracellular compartments, could be a nutrition index of being wasted overloaded in hemodialysis (HD) patients. This study aimed to describe a cut-off point of the ECM/BCM ratio and, to find out the relationship between the nutritional-hydration status and this ratio in HD patients.

METHODS

A case-control study was carried out in 64 HD patients individually age-gender-matched to controls. Demographic, clinical and laboratory parameters were recorded. Bioelectrical impedance analysis was used to estimate ECM/BCM ratio as an indicator of the nutritional hydration status. Receiver operator characteristic (ROC) curve analysis was applied to determine the optimal cut-off point for identification of ECM/BCM ratio. An univariate and multivariate conditional logistic regression for the ECM/BCM ratio ≥1.20 was performed.

RESULTS

Median of ECM/BCM ratio was 1.50 (IQR:0.66) in HD patients, whereas 0.87 (IQR: 0.35) was found in controls (p < 0.001). HD-patients had lower body weight, serum albumin (s-albumin) and higher serum C-reactive protein (s-CRP) than controls. By ROC curve analysis, a cut-off point of 1.20 for the ECM/BCM ratio best discriminates to be wasted-overhydrated (sensitivity: 81.2%; specificity: 87.5%). Conditional logistic regression showed that for each 10%, ECM/BCM ratio increase the probability of developing fluid overload was increased 63% (OR: 1.63; 95% CI, 1.15-2.29), whereas an inverse association with s-albumin (OR: 0.15; 95% CI, 0.03-0.61) and other nutritional indicators were found.

CONCLUSIONS

The ECM/BCM ratio appears as a sensitive index that discriminates nutritional and/or hydration status in HD patients compared with age-gender-matched-controls. ECM/BCM ratios ≥1.20 are indicators of wasting and fluid overload in HD patients.

Bioelectrical Impedance Analysis Measures and Clinical Outcomes in CKD

RATIONALE & OBJECTIVE

Bioelectrical impedance analysis (BIA) provides a noninvasive assessment of body composition. BIA measures of cell integrity (phase angle) and hydration (vector length) have been associated with mortality among patients receiving dialysis. Whether these measures are associated with clinical outcomes in patients with chronic kidney disease (CKD) is unknown.

STUDY DESIGN

Observational study.

SETTINGS & PARTICIPANTS

We studied 3,751 participants with CKD in the prospective multicenter Chronic Renal Insufficiency Cohort (CRIC) who had baseline single-frequency BIA performed.

PREDICTORS

Predictors included phase angle and vector length, which were calculated from measurements of resistance and reactance from BIA. We ranked phase angle and vector length into quartiles and compared the 2 narrower quartiles of phase angle and shorter quartiles of vector length with the 2 upper quartiles.

OUTCOMES

Mortality, heart failure, atherosclerotic cardiovascular disease, and progression of CKD (30% decline in estimated glomerular filtration rate or end-stage kidney disease).

ANALYTIC APPROACH

We tested associations of phase angle and vector length with risks for mortality and progression of CKD using Cox proportional hazard models and the association with heart failure and atherosclerotic cardiovascular disease using Fine and Gray models. All models were adjusted for demographics, comorbid conditions, and kidney function.

RESULTS

Mean phase angle and vector length were 6.6°±1.8° and 470 ± 96 Ω/m, respectively. Relative to phase angle ≥ 6.40o, narrower phase angle (<5.59o) was significantly associated with mortality (HR, 1.31; 95% CI, 1.09-1.58). Relative to vector length ≥ 459 Ω/m, shorter vector length (<401 Ω/m) was significantly associated with heart failure (HR, 1.28; 95% CI, 1.01-1.61). Neither measure was associated with atherosclerotic cardiovascular disease or a composite renal end point.

LIMITATIONS

Observational study.

CONCLUSIONS

Adjusted for key confounders, BIA-derived measures of cellular integrity and tissue hydration were significantly associated with death and incident heart failure, respectively.

Influence of dietary protein intake on body composition in chronic kidney disease patients in stages 3-5: A cross-sectional study

INTRODUCTION

A controlled protein intake has shown beneficial effects to preserve renal function and nutritional status in chronic kidney disease (CKD) patients. This study aimed to analyze usual dietary protein intake and its potential contribution to body composition in CKD patients in stages 3-5.

METHOD

Cross-sectional study in 134 CKD patients in stages 3-5 (mean e-GFR: 19.4±8.7ml/min/1.73m²; males 68.7% and primary CKD etiology was diabetes mellitus, 35.8%). Demographic, clinical and nutritional parameters were evaluated. Normalized protein nitrogen appearance (nPNA), was used as a surrogate marker of dietary protein intake. The sample was classified into three nPNA groups (G_n): G₁: <0.8g/kg/day; G₂: 0.8-1g/kg/day and, G₃: ≥1g/kg/day. Assessment of nutritional status using the malnutrition-inflammation score (MIS), anthropometric measures and laboratory parameters. Analysis of body composition and hydration status by bioelectrical impedance analysis (BIVA-101-RJL system). Statistical analysis by SPSS v.20.

RESULTS

Overall mean nPNA values were 0.91±0.23g of protein/kg BW/day and only 32.1% had a dietary protein intake <0.8g of protein/kg BW/day. Most of the CKD patients (65.5%) were in stages 4 or 5. Prevalence of protein-energy-wasting (PEW) syndrome measured by MIS was 15%. By analyzing differences between nPNA groups, body weight (BW), BMI and triceps-skinfold (TSF) thickness were significantly higher in the group with nPNA ≥1g/kg BW/day (G₃), whereas a significant inverse relationship was found with the percentages of body cell mass (BCM%), fat-free mass (FFM%), muscle mass (MM%) and phase angle (PA) in the group with the lowest nPNA (G₁). Analysis of gender among subjects showed significant differences with BW, FFM%, TSF and mid-arm muscle circumference (MAMC%). Linear regression analysis showed that resistance, BCM%, MM%, and serum albumin were significant predictors of nPNA as a surrogate marker of daily protein intake (R=0.51; R²=0.29; R² adjusted=0.23; p<0.001).

CONCLUSION

Controlled protein intake is one of the cornerstones of treatment in CKD patients. A low protein intake in patients with CKD stages 3 and 4-5 was associated with loss of muscle mass in the advanced-CKD unit. The loss of muscle mass appears as an early indicator of nutritional comprised. Factors such, elderly age and loss of eGFR, showed lower protein intake and were associated with muscle loss, especially in women. Further longitudinal studies are required to evaluate the contribution of different protein intakes to uremic symptoms, nutritional status, body composition and CKD progression.

Estimating of Residual Kidney Function by Multi-Frequency Bioelectrical Impedance Analysis in Hemodialysis Patients Without Urine Collection

BACKGROUND/AIMS

Residual kidney function (RKF) is a pivotal predictor of better clinical outcomes in maintenance hemodialysis (MHD) patients. So far there has been no attempt to use bioimpedance analysis (BIA) measurements to calculate residual glomerular filtration rate (GFR) in dialysis population. We hypothesized that performing of multi-frequency BIA at the beginning and end of hemodialysis session can enable us to predict the measured residual GFR in MHD patients. Thus our aim was to develop and validate a new RKF prediction equation using multi-frequency BIA in MHD patients.

METHODS

It was diagnostic test evaluation study in a prospective cohort. Participants (n=88; mean age, 66.3±13.2 years, 59.1% males) were recruited from a single hemodialysis center. A new equation (eGFRBIA) to predict RKF, utilizing BIA measurements performed pre- and post-dialysis, was generated and cross-validated by the leave-one-out procedure. GFR estimated as the mean of urea and creatinine clearance (mGFR) using urine collections during entire interdialytic period.

RESULTS

A prediction equation for mGFR that includes both pre- and post-dialysis BIA measurements provided a better estimate than either pre- or post-dialysis measurements alone. Mean bias between predicted and measured GFR was -0.12 ml/min. Passing and Bablok regression showed no bias and no significant deviation in linearity. Concordance correlation coefficient indicated good agreement between the eGFRBIA and mGFR (0.75, P<0.001). Using cut-off predicted mGFR levels >2 ml/min/1.73 m2 yielded an area under curve of 0.96, sensitivity 85%, and specificity 89% in predicting mGFR. The κ scores for intraobserver reproducibility were consistent with substantial agreement between first and second estimation of RKF according to eGFRBIA (weighted κ was 0.60 [0.37-0.83]).

CONCLUSION

We present a valid and clinically obtainable method to predict RKF in MHD patients. This method, which uses BIA, may prove as accurate, convenient and easily reproducible while it is operator independent.

Charlson Comorbidity Index is a Predictor of Outcomes in Incident Hemodialysis Patients and Correlates with Phase Angle and Hospitalization

Background

The adjustment of comorbidity is important in international hemodialysis comparisons. The aim of this study is to verify if it is possible to use the Charlson Comorbidity Index (CCI), in an Italian population of incident hemodialysis patients from the Campania region as outcome predictors. A similar proposal has already been made for an American population of incident patients in peritoneal dialysis. Methods: The data for this study come from the Uremic Registry of Campania taken in the year 2001. This is an observational study in which demographic, comorbid, laboratory, treatment and insurance data were collected in 111 dialysis units (70%) in Campania. We evaluated 515 hemodialysis incident patients who were hemodialyzed in Campania between January 1 and December 31, 2001. The study was restricted to patients who had already undergone 90 days of hemodialysis. The duration of this study was 15 months. Charlson Comorbidity Index was performed. In 128 patients (24.8%) BIA measurements were performed after dialysis. Statistics: We used Student's t test for unpaired data and Cox proportional model to analyze predictors of mortality. The variables analyzed were age at start of hemodialysis, sex, CCI, hemoglobin, diabetes, hypertension, albumin, days of hospitalization. The statistically significant variables, analyzed initially by univariate analysis, were chosen for multivariate analysis. We considered p< 0.05 statistically significant.

Results

A total of 515 patients (M=316, F=199) (age: 63.62±15.35 years) presented with the following diseases: NO diagnosed in 93 patients (19%), GN in 64 (13%) IN in 42 (9%), Hereditary in 55 (11%), Vascular in 66 (14%), Diabetes in 135 (28%), others in 30 (6%). Hemoglobin levels were 10.71±1.51 g/dL and albumin was 3.79±0.54 g/dL. The days of hospitalization for the population studied were 3364/year. After the study, 75 patients died and the overall mortality rate was 11.65/100 patient/years. Univariate analysis shows that there are significant differences calculated for age (median value 73 and 65 years, respectively for non-survivers and survivers), BMI (median value and 22 and 24 kg/m2, respectively), Hb (median value 9.5 and 11g/dL, respectively), Albumin (median value 3.5 and 3.8 g/dL, respectively), days of hospitalization (median value 8 and zero days, respectively), CCI (median value 6 and 4 score, respectively, phase angle (median value 3.3 and 4 degree, respectively). The mortality rates (100 dialysis years) by the CCI score: the mortality rate was zero for patients with a CCI of 3; and it increased to approximately 60% of patient years with a CCI score of 6 or greater. The linear correlation between CCI and phase angle in living (y=18.90 × - 3.83; R2 = 0.56) and in the dead (y = 13.01 × - 1.87; R2 = 0.29).

Discussion

We found that CCI is a strong predictor of mortality in incident HD patients as has also been indicated in PD patients; CCI correlates with phase angle calculated from Bioelectrical Impedance Analysis and this last factor can be used in the following examinations; several days of hospitalization are a very important determinant in the survival in hemodialysis patients.

Inadequacy of Dialysis, Chronic Inflammation and Malnutrition in Nigerian Patients on Chronic Hemodialysis

Purpose

To identify the extent of underdialysis, chronic inflammation and malnutrition and their interrelationships in Nigerian hemodialysis patients.

Methods

In a prospective study including 10 adult patients, (6 men, 4 women) on hemodialysis in North Central Nigeria, malnutrition was assessed by body mass index (BMI), serum albumin and prealbumin, and bioimpedance (BIA) pre-and post dialysis, inflammation was evaluated by C-reactive protein (CRP) and adequacy of dialysis was judged by frequency of the hemodialysis sessions and Kt/V urea.

Results

Post-dialysis BMI was 21.3 (19.9, 24.3) kg/m2 (< 20 kg/m2 in 4 patients), serum albumin 31.5 (24.0, 32.0) g/L (< 30.0 g/L in 5), serum pre-albumin 25.2 (15.3, 31.1) mg/dL (< 18.0 mg/dL in 4), serum CRP 4.8 (1.2, 11.5) mg/dL (> 1.0 mg/dL in 8), phase angle 4.2 (3.7, 5.1)° (< 3° in 3) and body fat deficit was diagnosed by BIA in 4 patients. Weekly frequency of dialysis was 3 times in 2 patients, twice in 1 and ≤1 time in 7. Single-pool Kt/V urea was 0.81 (0.68, 0.95, <1.2 in 9 patients and > 1.2 in one patient receiving dialysis only twice weekly). By combined frequency of dialysis and Kt/V urea values, no patient received an adequate dose of dialysis and, indeed, all patients had overt symptoms of uremia. Low body weight, low serological and BIA nutrition indices, and high CRP levels occurred in the same patients. Patients on dialysis for > 1 year had worse nutrition indices than those on dialysis for < 1 year.

Conclusions

Underdialysis was universal, while poor nutrition and chronic malnutrition were found in the majority of the small number of patients studied. These three adverse conditions, which were interlinked, may be common in Nigerian hemodialysis patients, because their underlying socioeconomic causes are widespread. (Int J Artif Organs 2006; 29: 1067–73)

Parathyroidectomy in chronic kidney disease: effects on weight gain and on quality of life improvement

Objective:

to evaluate the benefit of parathyroidectomy in patients on hemodialysis, regarding nutritional and biochemical statuses, body composition and the health-related quality of life.

Methods:

this is a longitudinal study involving 28 hemodialysis adult patients with severe secondary hyperparathyroidism evaluated before and one year after surgery. Inclusion criteria: parathyroid hormone levels exceeding ten times the upper normal range and end-stage renal disease in hemodialysis program. We used the body mass index to classify the nutritional status and the biodynamics analyzer to evaluate the body composition. Biochemical analysis included markers of lipid and bone metabolism. We assessed quality of life with the SF36 (Short Form Health Survey) questionnaire. All individuals underwent total parathyroidectomy with a forearm implant.

Results:

there were significant gains in body weight (61.7 vs 66.0 kg, p<0.001), body cell mass (22.0 vs 24.5 kg/m2, p=0.05) and quality of life (p=0.001) after surgery. With respect to bone metabolism, intact PTH, calcium, phosphorus and alkaline phosphatase all stabilized and there were improvements in biochemical parameters such as albumin and hemoglobin.

Conclusion:

parathyroidectomy improves hemodialysis patient survival and is associated with weight and bone cell mass gain and improvement in health-related quality of life.

Protein and Energy Depletion in Chronic Hemodialysis Patients: Clinical Applicability of Diagnostic Tools

Protein and energy depletion states are common and associated with increased morbidity and mortality in chronic hemodialysis (CHD) patients. Therefore, proper use of diagnostic tools to assess depleted states in CHD patients is critical. Assessment of protein and energy status can be done by an array of methodologies that include simple estimates of the visceral and somatic pools of protein to more refined techniques to measure protein and energy balance. The nutritional and metabolic derangements in the CHD population are highly complex and can be confounded by multiple comorbidities and fluid shifts between body compartments. Therefore, assessment of protein and energy status in CHD patients requires a wide range of methodologies that not only identify depleted states but also monitor nutrition therapy and predict clinical outcome. Most important, these methods require cautious and individualized interpretation in order to minimize the interference of comorbid conditions frequently observed in the CHD population. Currently, there is not a single method that can be considered the gold standard for assessment of protein and energy status in CHD patients. Therefore, a combination of methods is recommended. In this review, we describe available methods to assess protein and energy status, with special considerations pertaining to CHD patients.

Impedance ratio: a novel marker and a powerful predictor of mortality in hemodialysis patients

PURPOSE

Impedance ratio (Imp-R) obtained by multifrequency bioimpedance analysis (BIA) has been shown to be associated with volume and nutrition status. In this prospective study, the predictive role of Imp-R for mortality in hemodialysis (HD) patients was investigated.

METHODS

Multifrequency (5-50-100-200 kHz) BIA was applied to 493 prevalent HD patients in March-April 2006. Imp-R was defined as the ratio of 200-5 kHz impedance values. Demographical, clinical and laboratory data at the time of the analysis were recorded. All-cause and cardiovascular (CV) mortality were assessed during 3 years of follow-up.

RESULTS

Mean age was 57.7 ± 13.9 years, HD duration 52.1 ± 42.6 months and prevalence of diabetes 21.7 %. Imp-R was negatively correlated with nutritional markers including albumin, creatinine and hemoglobin levels. In addition, there was a positive correlation between Imp-R and age, ratio of extracellular water to total body water and high-sensitive C-reactive protein. Over a mean follow-up period of 27.9 ± 11.1 months, 93 deaths (52 from CV reasons) were observed. In the multivariate analysis, Imp-R was significantly associated with all-cause and CV mortality after adjustments [HR 1.13, 95 % CI (1.04-1.23); p = 0.004 and HR 1.15, 95 % CI (1.03-1.27); p = 0.01, respectively]. The risk of all-cause mortality was 3.4 times higher in the fourth quartile of Imp-R (>83.5 %) compared to the first Imp-R quartile (<78.8 %) as reference. Cutoff value of Imp-R for all-cause mortality was 82.0 % with a sensitivity of 65.5 % and specificity of 64 %.

CONCLUSION

Impedance ratio measured by multifrequency in standardized conditions BIA is an independent and powerful predictor of both all-cause and CV mortality in hemodialysis patients.

Correlation of bioelectrical impedance analysis phase angle with changes in oxidative stress on end-stage renal disease patients, before, during, and after dialysis

Chronic kidney disease is a condition that promotes oxidative stress. There are conflicting evidence about the role of hemodialysis on oxidative stress, that are mostly related with the various types of membrane materials used, the quality and type of dialysate, the method used, etc. The phase angle (PhA), which is determined with bioelectrical impedance analysis (BIA), measures the functionality of cell membranes. In this study, the correlation of the PhA with parameters of oxidative stress is attempted for the first time. We evaluated parameters of oxidative status as total antioxidant capacity (TAC) in erythrocytes (RBCs) and plasma of patients with ESRD undergoing hemodialysis with low flux synthetic polysulfone membranes. Measurements were recorded from 30 patients (16 men and 14 women) aged 64 ± 14 years before, during, and after dialysis, and in 15 healthy volunteers aged 56 ± 12 years The PhA was obtained by BIA. The plasma TAC increased significantly (41%, p < 0.05). Intracellular TAC noted a non-significant increase. Total antioxidant capacity of the patients before and after hemodialysis was significantly lower from the healthy volunteers (p < 0.05) showing that ESRD patients are at the state of increased oxidative stress. The PhA increased in significantly positive correlation with plasma TAC at the end of hemodialysis. The process of hemodialysis with biocompatible synthetic membranes and bicarbonate dialysate improved plasma TAC. The positive correlation of PhA with extracellular TAC could evolve to a method of oxidative stress estimation by BIA but further research is needed.

Nutritional assessment methods for zinc supplementation in prepubertal non-zinc-deficient children

BACKGROUND

Zinc is an essential nutrient that is required for numerous metabolic functions, and zinc deficiency results in growth retardation, cell-mediated immune dysfunction, and cognitive impairment.

OBJECTIVE

This study evaluated nutritional assessment methods for zinc supplementation in prepubertal non-zinc-deficient children.

DESIGN

We performed a randomised, controlled, triple-blind study. The children were divided into a control group (10% sorbitol, n=31) and an experimental group (10 mg Zn/day, n=31) for 3 months. Anthropometric and dietary assessments as well as bioelectrical measurements were performed in all children.

RESULTS

Our study showed (1) an increased body mass index for age and an increased phase angle in the experimental group; (2) a positive correlation between nutritional assessment parameters in both groups; (3) increased soft tissue, and mainly fat-free mass, in the body composition of the experimental group, as determined using bioelectrical impedance vector analysis; (4) increased consumption of all nutrients, including zinc, in the experimental group; and (5) an increased serum zinc concentration in both groups (p<0.0001).

CONCLUSIONS

Given that a reference for body composition analysis does not exist for intervention studies, longitudinal studies are needed to investigate vector migration during zinc supplementation. These results reinforce the importance of employing multiple techniques to assess the nutritional status of populations.

Bioelectrical impedance vector analysis for evaluating zinc supplementation in prepubertal and healthy children

BACKGROUND

The prevalence of abnormal nutritional status has increased in children and adolescents. Nutritional assessment is important for monitoring the health and nutritional status. Bioelectrical impedance vector analysis (BIVA) combines changes in tissue hydration and structure and body composition that can be assessed.

OBJECTIVES

The objective of this study was to use BIVA to evaluate nutritional status in 60 prepubertal children, aged between 8 and 9 years, supplemented with zinc, to detect possible changes in body composition.

DESIGN

We performed a randomized, controlled, triple-blind study. The children were divided into the control group (CG; sorbitol 10%, n=29) or the experimental group (EG; 10 mg Zn/day, n=31), and the duration of the experiment was 3 months. Anthropometric assessments were performed for all of the children.

RESULTS

The body mass index-for-age increased after oral zinc supplementation in the EG (p=0.005). BIVA indicated that the CG demonstrated a tendency for dehydration and decreased soft tissue and the EG demonstrated a tendency for increased soft tissue, primarily the fat-free mass. After analyses of BIVA ellipses, we observed that this method could detect improvements in body composition in healthy children supplemented with zinc.

CONCLUSIONS

These results suggest that BIVA could be an auxiliary method for studying a small population undergoing zinc intervention.

Phase angle, frailty and mortality in older adults

BACKGROUND

Frailty is a multidimensional phenotype that describes declining physical function and a vulnerability to adverse outcomes in the setting of physical stress such as illness or hospitalization. Phase angle is a composite measure of tissue resistance and reactance measured via bioelectrical impedance analysis (BIA). Whether phase angle is associated with frailty and mortality in the general population is unknown.

OBJECTIVE

To evaluate associations among phase angle, frailty and mortality.

DESIGN

Population-based survey.

SETTING

Third National Health and Nutritional Examination Survey (1988-1994).

PARTICIPANTS

In all, 4,667 persons aged 60 and older.

MEASUREMENTS

Frailty was defined according to a set of criteria derived from a definition previously described and validated.

RESULTS

Narrow phase angle (the lowest quintile) was associated with a four-fold higher odds of frailty among women and a three-fold higher odds of frailty among men, adjusted for age, sex, race-ethnicity and comorbidity. Over a 12-year follow-up period, the adjusted relative hazard for mortality associated with narrow phase angle was 2.4 (95 % confidence interval [95 % CI] 1.8 to 3.1) in women and 2.2 (95 % CI 1.7 to 2.9) in men. Narrow phase angle was significantly associated with mortality even among participants with little or no comorbidity.

LIMITATIONS

Analyses of BIA and frailty were cross-sectional; BIA was not measured serially and incident frailty during follow-up was not assessed. Participants examined at home were excluded from analysis because they did not undergo BIA.

CONCLUSIONS

Narrow phase angle is associated with frailty and mortality independent of age and comorbidity.

Hydration in advanced cancer: can bioelectrical impedance analysis improve the evidence base? A systematic review of the literature

CONTEXT

Decisions surrounding the administration of clinically assisted hydration to patients dying of cancer can be challenging because of the limited understanding of hydration in advanced cancer and a lack of evidence to guide health care professionals. Bioelectrical impedance analysis (BIA) has been used to assess hydration in various patient groupings, but evidence for its use in advanced cancer is limited.

OBJECTIVES

To critically appraise existing methods of hydration status assessment in advanced cancer and review the potential for BIA to assess hydration in advanced cancer.

METHODS

Searches were carried out in four electronic databases. A hand search of selected peer-reviewed journals and conference abstracts also was conducted. Studies reporting (de)hydration assessment (physical examination, biochemical measures, symptom assessment, and BIA) in patients with advanced cancer were included.

RESULTS

The results highlight how clinical examination and biochemical tests are standard methods of assessing hydration, but limitations exist with these methods in advanced cancer. Furthermore, there is disagreement over the evidence for some commonly associated symptoms with dehydration in cancer. Although there are limitations with using BIA alone to assess hydration in advanced cancer, analysis of BIA raw measurements through the method of bioelectrical impedance vector analysis may have a role in this population.

CONCLUSION

The benefits and burdens of providing clinically assisted hydration to patients dying of cancer are unclear. Bioelectrical impedance vector analysis shows promise as a hydration assessment tool but requires further study in advanced cancer. Innovative methodologies for research are required to add to the evidence base and ultimately improve the care for the dying.

Prediction of limb lean tissue mass from bioimpedance spectroscopy in persons with chronic spinal cord injury

BACKGROUND

Bioimpedance spectroscopy (BIS) is a non-invasive, simple, and inexpensive modality that uses 256 frequencies to determine the extracellular volume impedance (ECVRe) and intracellular volume impedance (ICVRi) in the total body and regional compartments. As such, it may have utility as a surrogate measure to assess lean tissue mass (LTM).

OBJECTIVE

To compare the relationship between LTM from dual-energy X-ray absorptiometry (DXA) and BIS impedance values in spinal cord injury (SCI) and able-bodied (AB) control subjects using a cross-sectional research design.

METHODS

In 60 subjects (30 AB and 30 SCI), a total body DXA scan was used to obtain total body and leg LTM. BIS was performed to measure the impedance quotient of the ECVRe and ICVRi in the total body and limbs.

RESULTS

BIS-derived ECVRe yielded a model for LTM in paraplegia, tetraplegia, and control for the right leg (RL) (R(2) = 0.75, standard errors of estimation (SEE) = 1.02 kg, P < 0.0001; R(2) = 0.65, SEE = 0.91 kg, P = 0.0006; and R(2) = 0.54, SEE = 1.31 kg, P < 0.0001, respectively) and left leg (LL) (R(2) = 0.76, SEE = 1.06 kg, P < 0.0001; R(2) = 0.64, SEE = 0.83 kg, P = 0.0006; and R(2) = 0.54, SEE = 1.34 kg, P < 0.0001, respectively). The ICVRi was similarly predictive of LTM in paraplegia, tetraplegia, and AB controls for the RL (R(2) = 0.85, SEE = 1.31 kg, P < 0.0001; R(2) = 0.52, SEE = 0.95 kg, P = 0.003; and R(2) = 0.398, SEE = 1.46 kg, P = 0.0003, respectively) and LL (R(2) = 0.62, SEE = 1.32 kg, P = 0.0003; R(2) = 0.57, SEE = 0.91 kg, P = 0.002; and R(2) = 0.42, SEE = 1.31 kg, P = 0.0001, respectively).

CONCLUSION

Findings demonstrate that the BIS-derived impedance quotients for ECVRe and ICVRi may be used as surrogate markers to track changes in leg LTM in persons with SCI.

Bioelectrical impedance parameters in critically ill children: importance of reactance and resistance

BACKGROUND & AIMS

Currently, there are no clinical or laboratory parameters that can be used efficiently to predict the prognosis of critically ill patients, but in some situations, raw bioelectrical impedance parameters have been shown to be useful. The purpose of this study was to investigate the behavior of reactance and resistance in the severity of the critically ill pediatric patient.

METHODS

We prospectively analyzed bioelectrical impedance in a sample of 332 critically ill pediatric patients submitted to mechanical ventilation. The values taken on admission and discharge were correlated with major outcomes to the critically ill patient.

RESULTS

We found an association of low values of Xc/H (<27.7 Ohm/m) and of R/H (<563.6 Ohm/m) on admission with multiple organs dysfunction greater or equal to 4. Both R/H and Xc/H increased significantly between admission and discharge among survivors, while among nonsurvivors there was a trend of decrease between admission and the last measurement before death.

CONCLUSIONS

Bioelectrical impedance is a useful tool for monitoring of critically ill pediatric patients. A possible role of R/H and Xc/H, especially the latter, as a predictive biomarker of evolution for septic shock and organ dysfunction still remains to be elucidated.

Malnutrition-inflammation score is associated with handgrip strength in nondialysis-dependent chronic kidney disease patients

OBJECTIVE

The malnutrition-inflammation score (MIS) is a nutritional scoring system that has been associated with muscle strength among dialysis patients. We aimed to test whether MIS is able to predict muscle strength in nondialysis-dependent chronic kidney disease (NDD-CKD) individuals.

DESIGN AND METHODS

This was a cross-sectional study conducted at the Dante Pazzanese Institute of Cardiology, Hypertension, and Nephrology Division outpatient clinic. We evaluated 190 patients with NDD-CKD stages 2-5 (median 59.5 [interquartile range 51.4-66.9] years; 64% men). MIS was calculated without computing dialysis vintage to the scoring. HGS was assessed in the dominant arm. Anthropometric, laboratory, and body composition parameters were recorded.

RESULTS

A strong negative correlation was found between HGS and MIS (r = -0.42; P ≤ .001) in univariate analysis. In multivariate regressions, adjustment for age, sex, diabetes, glomerular filtration rate, body cell mass, and C-reactive protein did not materially diminish these relationships.

CONCLUSIONS

MIS shares strong links with objective measures of muscle strength in NDD-CKD patients.

Formulation of a dry weight bioimpedance index in hemodialysis patients

Hydration status has a major impact on hemodialysis (HD) patients. Overhydration is related to hypertension, pulmonary and peripheral edema, and other cardiovascular events; while dehydration is related to hypotension, and other severe ischemic symptoms. All result in increased morbidity and mortality. Bioimpedance has been newly developed to measure the amount of water in the body. Several predictive equations were used, taken from demographic and anthropometric data. The purpose of this study was to evaluate the body composition of HD patients and to propose a hydration index. We performed bioimpedance measures with the Tanita TBF-300 scale, which calculates Total Body Water (TBW). The tool was reliable, with good reproducibility. However, we found significant differences between weight variations (dW) and TBW variations (dTBW) during HD sessions. This paper proposes a hydration index (I=dW-dTBW), with the hypothesis that dry weight is reached when I=0, while I>0 or I<0 indicate overhydrated or dehydrated, respectively. In this study, the changes in the index corresponded to the variations in weight and hydration state. We conclude that impedancemetry is a currently available technique that can be used to estimate TBW in HD patients. Although the index has to be improved by complementary studies, it may be a good guide to assess the dry weight achieved.

The Relationship between Bioimpedance Analysis, Haemodynamic Parameters of Haemodialysis, Biochemical Parameters and Dry Weight

Adequate fluid management plays an important role in the treatment of haemodialysis patients and the assessment of dry weight is important for efficient therapy. Fluid volume parameters were assessed in adults undergoing haemodialysis for end-stage renal disease, using whole-body multifrequency bioimpedance analysis (BIA), and their relationship to haemodynamic and biochemical parameters of haemodialysis was evaluated. Ultrafiltration volume was correlated with age, sodium, haemoglobin, extracellular water (ECW)/total body water (TBW) ratio and ECW/intracellular water (ICW) ratio. The ECW/TBW ratio was correlated with age, body mass index, dry weight, predialysis systolic and diastolic blood pressure, and ECW/total body weight ratio. The ECW/ICW ratio correlated with age, dry weight, TBW, albumin, adequacy of dialysis and urea removal ratio. The study demonstrated a close relationship between bioimpedance-derived fluid volume parameters and the haemodynamic and biochemical parameters of haemodialysis. It is concluded that multifrequency whole-body BIA may have clinical value in the estimation of dry weight and other haemodynamic parameters of haemodialysis and so may protect patients from the risks associated with under- or over-hydration.

Comparison of nutritional parameters among adult and elderly hemodialysis patients

AIM

The aim of this study was to compare the nutritional biochemical parameters, prealbumin levels, and bioimpedance analysis parameters of adult and elderly hemodialysis (HD) patients.

METHODS

This prospective cross-sectional study included 50 adult HD patients (42.0 % female). Nutritional status was assessed by post-dialysis multifrequency bioimpedance analysis (BIA), serum prealbumin and other nutritional biochemical parameters.

RESULTS

Mean age of patients was 57.4±15.1 years (range: 30-83 years) and mean dialysis duration was 68.3 ± 54.5 months (range: 3-240 months). When the patients were divided into two groups according to age of patients (<65 and ≥65), prealbumin (p=0.003), blood urea nitrogen (BUN) (p=0.000), serum creatinine (p=0.013), albumin (p=0.016), protein catabolic rate per normalized body weight (nPCR) (p=0.001), intracellular water (ICW)/total body weight (0.003) , body fat mass (p00.000), lean body mass (p=0.031), lean dry mass (p=0.001), illness marker (p=0.005), basal metabolism (p=0.007), body mass index (BMI) (p=0.028), body fat mass index (BFMI) (p=0.000), fat free mass index (FFMI) (p=0.040) values were significantly different between the groups. In the elderly patients (age ≥65), body fat mass, illness marker, BMI, BFMI were higher compared to adult patients (age <65). Additionally, in the elderly patients, prealbumin, BUN, creatinine, albumin, nPCR, ICW/ total body weight, lean body weight, lean dry weight, basal metabolism and FFMI were lower than adult patients.

CONCLUSIONS

Our results indicate that BFMI were higher, albumin, prealbumin, nPCR and lean body mass and FFMI were lower in elderly patients compared to adults. These results imply that elderly HD patients may be prone sarcopenic obesity and may require special nutritional support.

Determinants of bioelectrical phase angle in disease

Phase angle (PhA), a parameter of bioelectrical impedance analysis, is a well-known predictor of morbidity and mortality in various diseases. The causes of decreased PhA are, however, not yet completely understood. We therefore investigated determinants of PhA in 777 hospitalised patients in a retrospective analysis. PhA was assessed by bioelectrical impedance analysis at 50 KHz. Subjective global assessment (SGA) was used to evaluate nutritional status. Age, sex, BMI as well as nutritional status (SGA), benign or malignant disease and C-reactive protein (CRP) were investigated as potential determinants of PhA and standardised PhA (SPhA) = (observed PhA - mean PhA of reference values)/standard deviation of reference values in a general linear model regression analysis. Next to age (estimated effect size, 46·6%; P<0·0001), malnutrition (39·1%; P<0·0001) emerged as a major PhA determinant in our study population. Moreover, sex (6·4%; P<0·0001), CRP (4·4%; P<0·0001) and BMI (3·5%; P < 0·0001) exhibited a significant influence on PhA, whereas malignant disease showed no significant effect in this model. The only significant determinants of SPhA were malnutrition (85·4%; P<0·0001) and inflammation (9·6 %; P<0·0001). In conclusion, next to the established predictors, malnutrition and inflammation have a strong impact on PhA in sick individuals, which partly explains its prognostic power. When investigating the SPhA, only malnutrition and inflammation were found to be significant predictors, as a result of which the SPhA is considered a more suitable indicator of nutritional and health status.

Relevância do estado de hidratação na interpretação de parâmetros nutricionais em diálise peritoneal

OBJETIVO: Identificar determinantes do estado de hidratação de pacientes em diálise peritoneal crônica, bem como investigar os efeitos da sobrecarga líquida sobre o estado nutricional. MÉTODOS: Foi feito estudo transversal, realizado em 2006, avaliando 27 pacientes em diálise peritoneal crônica, acompanhados no Hospital das Clínicas da Faculdade de Medicina de Botucatu (SP), quanto a parâmetros clínicos, dialíticos, laboratoriais, antropométricos e de bioimpedância elétrica. Para avaliar a influência de parâmetros sobre o estado de hidratação empregou-se modelo de regressão linear múltipla. A amostra foi estratificada quanto ao estado de hidratação pela relação entre água extracelular e água corporal total (0,47 para homens e 0,52 para mulheres), parâmetros obtidos por meio de bioimpedância elétrica. Comparações foram realizadas por análise de covariância, Mann-Whitney, Qui-quadrado ou teste exato de Fisher. Considerou-se significância estatística quando p≤0,05. RESULTADOS: Pacientes com maior volume urinário e em modalidade dialítica automatizada apresentaram melhor estado de hidratação. Pacientes com maior sobrecarga líquida, comparados àqueles com menor sobrecarga, apresentaram menor ângulo de fase (M=4,2, DP=0,9 vs M=5,7, DP=0,7º; p=0,006), menor albumina (M=3,06, DP=0,46 vs M=3,55, DP=0,52g/dL; p=0,05) e maior % prega cutânea tricipital (M=75,3, DP=36,9 vs M=92,1, DP=56,9%; p=0,058), sem outras evidências antropométricas. CONCLUSÃO: Pode-se sugerir que os níveis reduzidos de albumina e ângulo de fase nos pacientes com maior sobrecarga líquida não estiveram relacionados a pior estado nutricional. Para o diagnóstico nutricional em vigência de sobrecarga líquida, deve-se considerar o conjunto de variáveis obtidas por diversos métodos, buscando relacioná-las e interpretá-las de maneira abrangente, possibilitando um diagnóstico nutricional fidedigno.

An implantable biochip to influence patient outcomes following trauma-induced hemorrhage

Following hemorrhage-causing injury, lactate levels rise and correlate with the severity of injury and are a surrogate of oxygen debt. Posttraumatic injury also includes hyperglycemia, with continuously elevated glucose levels leading to extensive tissue damage, septicemia, and multiple organ dysfunction syndrome. A temporary, implantable, integrated glucose and lactate biosensor and communications biochip for physiological status monitoring during hemorrhage and for intensive care unit stays has been developed. The dual responsive, amperometric biotransducer uses the microdisc electrode array format upon which were separately immobilized glucose oxidase and lactate oxidase within biorecognition layers, 1.0-5.0 μm thick, of 3 mol% tetraethyleneglycol diacrylate cross-linked p(HEMA-co-PEGMA-co-HMMA-co-SPA)-p(Py-co-PyBA) electroconductive hydrogels. The device was then coated with a bioactive hydrogel layer containing phosphoryl choline and polyethylene glycol pendant moieties [p(HEMA-co-PEGMA-co-HMMA-co-MPC)] for indwelling biocompatibility. In vitro cell proliferation and viability studies confirmed both polymers to be non-cytotoxic; however, PPy-based electroconductive hydrogels showed greater RMS 13 and PC12 proliferation compared to controls. The glucose and lactate biotransducers exhibited linear dynamic ranges of 0.10-13.0 mM glucose and 1.0-7.0 mM and response times (t(95)) of 50 and 35-40 s, respectively. Operational stability gave 80% of the initial biosensor response after 5 days of continuous operation at 37 °C. Preliminary in vivo studies in a Sprague-Dawley hemorrhage model showed tissue lactate levels to rise more rapidly than systematic lactate. The potential for an implantable biochip that supports telemetric reporting of intramuscular lactate and glucose levels allows the refinement of resuscitation approaches for civilian and combat trauma victims.

Bioelectrical impedance analysis in clinical practice: implications for hepatitis C therapy BIA and hepatitis C

Background

Body composition analysis using phase angle (PA), determined by bioelectrical impedance analysis (BIA), reflects tissue electrical properties and has prognostic value in liver cirrhosis. Objective of this prospective study was to investigate clinical use and prognostic value of BIA-derived phase angle and alterations in body composition for hepatitis C infection (HCV) following antiviral therapy.

Methods

37 consecutive patients with HCV infection were enrolled, BIA was performed, and PA was calculated from each pair of measurements. 22 HCV genotype 3 patients treated for 24 weeks and 15 genotype 1 patients treated for 48 weeks, were examined before and after antiviral treatment and compared to 10 untreated HCV patients at 0, 24, and 48 weeks. Basic laboratory data were correlated to body composition alterations.

Results

Significant reduction in body fat (BF: 24.2 ± 6.7 kg vs. 19.9 ± 6.6 kg, genotype1; 15.4 ± 10.9 kg vs. 13.2 ± 12.1 kg, genotype 3) and body cell mass (BCM: 27.3 ± 6.8 kg vs. 24.3 ± 7.2 kg, genotype1; 27.7 ± 8.8 kg vs. 24.6 ± 7.6 kg, genotype 3) was found following treatment. PA in genotype 3 patients was significantly lowered after antiviral treatment compared to initial measurements (5.9 ± 0.7° vs. 5.4 ± 0.8°). Total body water (TBW) was significantly decreased in treated patients with genotype 1 (41.4 ± 7.9 l vs. 40.8 ± 9.5 l). PA reduction was accompanied by flu-like syndromes, whereas TBW decline was more frequently associated with fatigue and cephalgia.

Discussion

BIA offers a sophisticated analysis of body composition including BF, BCM, and TBW for HCV patients following antiviral regimens. PA reduction was associated with increased adverse effects of the antiviral therapy allowing a more dynamic therapy application.

Prevalence and correlates of cognitive impairment in hemodialysis patients: the Frequent Hemodialysis Network trials

BACKGROUND AND OBJECTIVES

Cognitive impairment is common among persons with ESRD, but the underlying mechanisms are unknown. This study evaluated the prevalence of cognitive impairment and association with modifiable ESRD- and dialysis-associated factors in a large group of hemodialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Cross-sectional analyses were conducted on baseline data collected from 383 subjects participating in the Frequent Hemodialysis Network trials. Global cognitive impairment was defined as a score <80 on the Modified Mini-Mental State Exam, and impaired executive function was defined as a score >or=300 seconds on the Trailmaking B test. Five main categories of explanatory variables were examined: urea clearance, nutritional markers, hemodynamic measures, anemia, and central nervous system (CNS)-active medications.

RESULTS

Subjects had a mean age of 51.6 +/- 13.3 years and a median ESRD vintage of 2.6 years. Sixty-one subjects (16%) had global cognitive impairment, and 110 subjects (29%) had impaired executive function. In addition to several nonmodifiable factors, the use of H1-receptor antagonists and opioids were associated with impaired executive function. No strong association was found between several other potentially modifiable factors associated with ESRD and dialysis therapy, such as urea clearance, proxies of dietary protein intake and other nutritional markers, hemodynamic measures, and anemia with global cognition and executive function after adjustment for case-mix factors.

CONCLUSIONS

Cognitive impairment, especially impaired executive function, is common among hemodialysis patients, but with the exception of CNS-active medications, is not strongly associated with several ESRD- and dialysis-associated factors.

Lowering postdialysis plasma sodium (conductivity) to increase sodium removal in volume-expanded hemodialysis patients: a pilot study using a biofeedback software system

BACKGROUND

Extracellular fluid expansion is common in hemodialysis patients. Aggressive fluid removal may lead to intradialytic complications. High dialysate sodium concentrations may lessen complications, but may increase extracellular volume. We hypothesized that decreasing plasma sodium concentration during dialysis will increase sodium removal and decrease extracellular volume.

STUDY DESIGN

Pilot clinical trial.

SETTING & PARTICIPANTS

16 patients with end-stage kidney disease treated using thrice-weekly hemodialysis at a university teaching hospital hemodialysis unit.

INTERVENTION

Stepwise decrease in postdialysis plasma sodium level (calculated as end-of-session plasma conductivity) over 4 phases effected by dialysate conductivity measurement cells and a biofeedback software system (Diacontrol; Hospal, www.hospal.it) that allowed alteration of dialysate inlet conductivity and calculation of plasma conductivity.

OUTCOMES

Decrease in postdialysis plasma sodium (conductivity) levels, sodium removal, redistribution of body water, and effect of these on interdialytic weight gain and blood pressure.

MEASUREMENTS

Plasma sodium and conductivity values (the latter measured in millisiemens per centimeter); ionic mass balance (sodium removal); bioelectrical impedance analysis measurements of body-water compartments and phase angle; interdialytic weight gain; and blood pressure.

RESULTS

Plasma sodium concentrations at the end of dialysis were decreased from 137.8 (phase 1) to 135.6 mmol/L (phase 4) and end-of-session plasma conductivity values were decreased from 14.0 (phase 1) to 13.5 mS/cm (phase 4; all mean values). Ionic mass balance increased from 383 to 480 mmol. Extracellular water was significantly decreased, phase angle was increased, and blood pressure and interdialytic weight gain were decreased. Plasma sodium levels correlated significantly with plasma conductivity; thus, changes in postdialysis plasma sodium levels can be inferred from changes in end-of-session plasma conductivity values.

LIMITATIONS

Small number of patients. No information for dietary sodium intake.

CONCLUSION

To decrease extracellular volume, it may be necessary to add diffusive to convective sodium losses.