Bioelectrical impedance analysis in dialysis patients

Calf circumference predicts sarcopenia in maintenance hemodialysis

BACKGROUND

Early recognition of sarcopenia in hemodialysis (HD) patients will be of great importance in preventing adverse outcomes and improving the quality of life in these patients. The main goal of this study was to evaluate the diagnostic accuracy of calf circumference (CC) measurement in detecting sarcopenia among CKD patients undergoing maintenance HD.

METHODS

This cross-sectional study included 52 patients (53 ± 17 years) who were currently in a maintenance HD. Muscle strength was evaluated using handgrip strength, and smooth muscle mass index (SMI) was assessed through bioelectrical impedance analysis, and CC was measured at the widest part of the calf with the foot pressed against a hard surface.

RESULTS

Out of the total patient population, sarcopenia was identified in 32.7% (n = 17). The two groups were comparable in terms of age, weight, and height, but the median body mass index of sarcopenic group was statistically lower than nonsarcopenic group (21.6 kg/m2 [18.9-24.6] vs 24.7 kg/m2 [21.4-27.3]. The sarcopenic group had a substantially smaller CC than the nonsarcopenic group (30.0 cm [26.5-32.0] vs 31.5 cm [30.3-34.8], P = 0.013; respectively). In the regression analysis, CC was found to be independently associated with post-HD SMI (P < 0.001; odds ratio, 1.938; and 95% CI, 1.020-2.856). CC was positively but weakly correlated with handgrip strength, however strong and significant correlation was found between CC and SMI (r = 0.277, P = 0.047 and r = 0.733, P < 0.001; respectively). A CC of 31 cm or less predicted confirmed sarcopenia in HD patients (area under the curve = 0.709, P = 0.006, specificity = 0.556, sensitivity = 0.765).

CONCLUSIONS

Low muscle mass and potentially low muscle strength in HD patients can be accurately identified through the use of CC measurements. Specifically, a CC measurement below 31 cm has found to be a useful indicator to identify individuals on maintenance HD.

Preoperative Body Composition Correlates with Postoperative Muscle Volume and Degeneration after Total Hip Arthroplasty

Impaired muscle recovery after total hip arthroplasty (THA) may affect gait and activities of daily living. Bioelectrical impedance analysis (BIA) can assess body composition and muscle volume, and computed tomography (CT) can assess muscle volume and the fatty degeneration of muscle. This study aimed to explore the effectiveness of BIA, and the correlation between preoperative body composition and postoperative muscle volume and degeneration after THA using BIA and CT. Thirty-eight patients who underwent THA and had BIA and CT performed pre- and postoperatively were retrospectively assessed. The BIA-derived measurements of preoperative body composition (fat mass index, fat-free mass index, and phase angle) were correlated with the CT-derived measurements (pre- and postoperative muscle volume and gluteus maximus and quadriceps Hounsfield Units of the affected hip). The preoperative fat mass index negatively correlated with the postoperative muscle volume of the gluteus maximus (p = 0.02) and quadriceps (p < 0.001) and the Hounsfield Units of the gluteus maximus (p = 0.03) and quadriceps (p = 0.03). The preoperative fat-free mass index positively correlated with the postoperative muscle volume of the quadriceps (p = 0.02). The preoperative phase angle positively correlated with the postoperative muscle volume of the quadriceps (p = 0.001) and the Hounsfield Units of the gluteus maximus (p = 0.03) and quadriceps (p = 0.001). In patients who underwent THA, preoperative body composition correlated with postoperative muscle volume and the fatty degeneration of the affected lower limb. Preoperative body composition may help predict postoperative muscle volume and fatty degeneration and thus, postoperative recovery.

Comparisons between Bioelectrical Impedance Variables, Functional Tests and Blood Markers Based on BMI in Older Women and Their Association with Phase Angle

The aim of the present study was to compare electrical bioimpedance variables, blood markers and functional tests based on Body Mass Index (BMI) in older women. Associations between Phase Angle (PhA) with functional tests and blood markers were also analyzed. A total of 46 independent elderly people participated in the study, and they were divided into four groups according to BMI values: Group 1 (G1, BMI < 25 kg/m2); Group 2 (G2, BMI > 25−30 kg/m2); Group 3 (G3, BMI > 30−35 kg/m2); Group 4 (G4, BMI > 35 kg/m2). In addition to the weight and height used to calculate the BMI, the following body composition variables were collected: fat mass (FM), fat-free mass, intracellular water (ICW), extracellular water (ECW), total body water (TBW) and PhA (50 kHz) through InBody S10 equipment. Functional capacity was assessed using the Fullerton battery of tests: arm-curl; chair-stand; 6 min walking test (6MWT); time up-and-go test (TUG); standing on one leg (SOOL) and take 10 foot-lines (10FL). The main results showed differences between groups in the tests: 6MWT, SOOL and 10FL between G1 vs. G3 and G2 vs. G3 (p < 0.05); ACT, AIC and AEC between G1 vs. G4 (p < 0.05); FM among all groups (p < 0.05). Negative correlations were found between PhA and the agility test in G1 (r = −0.848; p = 0.008) and G4 (r = −0.909; p = 0.005); PhA and chair-stand in G3 (r = 0.527; p = 0.044); PhA and forearm flexion in G3 (r = 0.641; p = 0.010) and G4 (r = 0.943; p = 0.001); PhA and 6MWT in G4 (r = 0.771; p = 0.042). This study found that there is a clear trend towards better functional capacities with better parameters of body composition. Although there were no differences between groups in PhA, associations were found between different functional tests with PhA, which reveals the importance of this variable as a marker of health status.

Body composition assessment using bioelectrical impedance analysis (BIA) in a wide cohort of patients affected with mild to severe obesity

BACKGROUND & AIMS

Obesity is characterized by fat mass excess (FM), extra cellular water increase (ECW) and, with ageing, decrease in fat free mass (FFM). The validity of body impedance analysis (BIA) in patients with mild to severe obesity is still debated. The purpose of this study is to describe the Resistance (Rz) and Reactance (Xc) values obtained by Body Impedance Analysis (BIA) in a wide cohort of Italian patients with mild to severe obesity. The secondary endpoint is to describe the resulting body composition values (as percentage and indexes) in this population.

METHODS

The study enrolled adult in-patients with mild to severe obesity (classified with class I, II and III obesity) undergoing clinical care rehabilitation program for obesity complications and weight loss. BIA values were grouped by sex, BMI and age classes.

RESULTS

A total of 8303 patients with obesity, aged 18 to 90 y, were studied. The Resistance (Rz) and Reactance (Xc) were reported by sex, age and BMI classes. In women and men both, the phase angle (PhA) decreases with increasing BMI (kg/m²) and the resulting BIA vector was significantly shifted. The FM index (FMI) was higher (p < 0.0001) in women while FFM index (FFMI) was higher in men (p < 0.0001) and significantly associated with BMI. FFMI decreased with age in both sex (p < 0.0001). Skeletal mass (SM) presents a progressive reduction in relation to age and gender both.

CONCLUSIONS

The present BIA-based body composition analysis in a wide cohort of mild to severe obese patients revealed a significantly decreased Rz and Xc values with a consequent significant decrease of PhA in a BMI-dependent manner. The body compartments estimation with available equations was BMI, sex and age dependent. These observational results could be the basis for the development of new equations adapted for patients suffering from obesity.

Bioelectrical impedance vector analysis evaluates cellularity and hydration in cirrhotic patients

BACKGROUND

Malnutrition in cirrhotic patients is correlated with mortality and a better response to liver transplantation. However, recovery of the nutritional status in these patients is a challenge due to the difficulty in establishing a reliable nutritional diagnosis. The bioelectrical impedance vector analysis (BIVA) method appears as a feasible tool in clinical practice to define the physiological state of cirrhotic patients by assessing hydration and body cellularity.

AIM

To evaluate body composition in cirrhotic patients using BIVA.

METHODS

This retrospective cross-sectional study was carried out by following cirrhotic outpatients at a hospital in Porto Alegre, Brazil. A tetrapolar bioelectrical impedance analysis device was used to evaluate cellularity and hydration and to perform the BIVA. The BIVA graphic was elaborated by software and for statistical analysis a significance level of 5% (P ≤ 0.05) was considered.

RESULTS

One hundred and ninety patients, 61.1% males, with a mean age of 56.6 ± 11.0 years, were evaluated. Of these, 56.3% had Child-Turcotte-Pugh (CTP) A score, and the prevalent etiology was hepatitis C virus (47.4%). The patients were classified according to cellularity and hydration by the quadrants and ellipses of the BIVA method, quadrant 1 (47.9%); quadrant 2 (18.9%); quadrant 3 (14.2%); and quadrant 4 (18.9%). Those classified in quadrant 1 and 2 had a higher phase angle compared to those in quadrants 3 and 4 (P < 0.001). Quadrant 2 patients had a lower average age than the other groups. The association with CTP score showed that patients in quadrant 2 had a higher proportion of CTP A, and those in quadrant 4 had a higher proportion of CTP C (P < 0.052).

CONCLUSION

The BIVA method allows identification of the cellularity and hydration status of cirrhotic patients, and its association with clinical factors determines the disease severity, age and prognostic index.

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.

Phase Angle From Bioelectrical Impedance Analysis: Population Reference Values by Age, Sex, and Body Mass Index

BACKGROUND

The use of bioelectrical impedance phase angle has been recommended as a prognostic tool in the clinical setting, but published reference data bases are discrepant and incomplete (eg, they do not consider body mass index [BMI], and data are lacking for children).

METHODS

Phase angle reference values stratified by age, sex, and BMI were generated in a large German data base of 15,605 children and adolescents and 214,732 adults, and the determinants of phase angle values were assessed. The reference values were applied to 3 groups of patients and compared with previously published reference values from the United States and Switzerland.

RESULTS

Gender and age were the main determinants of phase angle in adults, with men and younger subjects having higher phase angles. In children and adolescents, age and BMI were the main determinants of phase angle. In normal and overweight adults, phase angle increased with increasing BMI, but there was an inverse association at a BMI >40 kg/m2. In cirrhosis, the prevalence of a low phase angle increased with the state of disease, whereas it was not different between patients with the metabolic syndrome and controls. There are considerable differences between phase angle reference values from different populations. These differences are not explained by age or BMI and may be due to differences between impedance analyzers.

CONCLUSION

The determinants of phase angle differ between adults and children. In adults, the influence of BMI on phase angle depended on the BMI range. The prognostic value of phase angle may differ in different clinical settings. The use of population-specific and probably impedance-analyzer-specific reference values for phase angle is recommended.

Nutrition assessment and its effect on various clinical variables among patients undergoing liver transplant

BACKGROUND

Malnutrition is highly prevalent in patients undergoing liver transplantation and has been associated to various clinical variables and outcome of the surgery.

METHODS

We recruited 54 adult patients undergoing living donor liver transplant (LT) as study sample. Nutrition assessment was performed by body mass index (BMI), BMI for ascites, albumin, subjective global assessment (SGA) and anthropometry [mid upper arm circumference (MUAC), mid arm muscle circumference (MAMC), and triceps skin-fold (TSF)], Hand Grip strength, and phase angle of the body. Prevalence and comparison of malnutrition was performed with various clinical variables: aetiology, Child Turcotte Pugh scores and model for end stage liver disease (ESLD) grades, degree of ascites, blood product usage, blood loss during the surgery, mortality, days [intensive care unit (ICU), Ventilator and Hospital], and Bio-impedance analysis [weight, fat mass, fat free mass (FFM), muscle mass and body fat%].

RESULTS

Assessment of nutrition status represents a major challenge because of complications like fluid retention, hypoalbuminemia and hypoproteinemia. Different nutrition assessment tools show great disparity in the level of malnutrition among ESLD patients. In the present study recipient nutrition status evaluation by different nutrition assessment tools used showed malnutrition ranging from 3.7% to 100%. BMI and anthropometric measurements showed lower prevalence of malnutrition than phase angle and SGA whereas hand grip strength showed 100% malnutrition. Agreement among nutrition assessment methods showed moderate agreement (κ=0.444) of SGA with phase angle of the body. Malnutrition by different assessment tools was significantly associated to various clinical variables except MELD and days (ICU, Ventilator and Hospital). SGA was significantly (P<0.05) associated to majority of the clinical variables like aetiology, child Turcotte Pugh grades, degree of ascites, blood product usage, blood loss during the surgery, BIA (fat mass, FFM, muscle mass and body fat%).

CONCLUSIONS

The different nutrition assessment tools showed great variability of results. SGA showed moderate agreement with phase angle of the body and was associated with various clinical and prognostic variables of liver transplantation.

Nutritional assessment in patients with cirrhosis

CONTEXT

Malnutrition in cirrhotic patients with end-stage disease is common, and the degree of nutritional debilitation can play an important role in the pathogenesis of complications and cause a negative impact on prognosis. However, it involves difficulties and controversies regarding the identification of the best nutritional assessment method.

OBJECTIVE

To identify a method that provides a safe and effective nutritional diagnosis.

METHODS

Cross-sectional study with 129 cirrhotic patients. Anthropometric measurements, subjective global assessment, hand grip strength and bioelectrical impedance.

RESULTS

Through phase angle of bioelectrical impedance analysis (BIA) method, significant associations with Child-Pugh (P = 0.008), age group and gender were observed. The ROC (receiver operator characteristic) curve was generated to determine the best cutoff point of the phase angle of cirrhotic patients, serving as one of the reference parameters for the nutritional assessment with bioimpedance in this study, considering the classification through Child-Pugh score as the reference standard for the clinical conditions of patients with cirrhosis.

CONCLUSIONS

The assessment through bioelectrical impedance presented a statistically significant correlation with Child-Pugh score. The identification of phase angle of 5.44º is the new parameter suggested for the classification of the nutritional conditions of cirrhotic patients.

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.

Standardized phase angle from bioelectrical impedance analysis as prognostic factor for survival in patients with cancer

PURPOSE

Phase angle (PA), determined by bioelectrical impedance analysis (BIA), has been considered as a prognostic factor in several clinical conditions. The purpose of this study is to investigate PA, after adjusting for sex and age (standardized phase angle; SPA) as a prognostic factor for survival in cancer patients.

METHODS

A prospective study was conducted in 195 patients before the first chemotherapy course. BIA was performed in all patients and SPA was calculated. The Kaplan-Meier method was used to calculate survival. The Cox regression method was used to evaluate the independent prognostic effect of PA after adjustment for other variables.

RESULTS

Patients with SPA < -1.65 had a smaller survival rate than those with SPA ≥ -1.65 (p < 0.001). Using Cox regression, the mortality rate was higher in patients with SPA < -1.65 (RR 3.12 CI: 2.03-4.79; p < 0.001). After multivariate analysis, patients with PA < -1.65 still presented a higher mortality rate (RR 2.35 CI: 1.41-3.90; p = 0.001).

CONCLUSIONS

The present study demonstrates that PA, used as SPA, is an independent prognostic indicator in this group of cancer patients receiving chemotherapy treatment even after adjustment for other prognostic variables.

Bioelectrical impedance phase angle in clinical practice: implications for prognosis in stage IIIB and IV non-small cell lung cancer

Background

A frequent manifestation of advanced lung cancer is malnutrition, timely identification and treatment of which can lead to improved patient outcomes. Bioelectrical impedance analysis (BIA) is an easy-to-use and non-invasive technique to evaluate changes in body composition and nutritional status. We investigated the prognostic role of BIA-derived phase angle in advanced non-small cell lung cancer (NSCLC).

Methods

A case series of 165 stages IIIB and IV NSCLC patients treated at our center. The Kaplan Meier method was used to calculate survival. Cox proportional hazard models were constructed to evaluate the prognostic effect of phase angle, independent of stage at diagnosis and prior treatment history.

Results

93 were males and 72 females. 61 had stage IIIB disease at diagnosis while 104 had stage IV. The median phase angle was 5.3 degrees (range = 2.9 – 8). Patients with phase angle <= 5.3 had a median survival of 7.6 months (95% CI: 4.7 to 9.5; n = 81), while those with > 5.3 had 12.4 months (95% CI: 10.5 to 18.7; n = 84); (p = 0.02). After adjusting for age, stage at diagnosis and prior treatment history we found that every one degree increase in phase angle was associated with a relative risk of 0.79 (95% CI: 0.64 to 0.97, P = 0.02).

Conclusion

We found BIA-derived phase angle to be an independent prognostic indicator in patients with stage IIIB and IV NSCLC. Nutritional interventions targeted at improving phase angle could potentially lead to an improved survival in patients with advanced NSCLC.

Bioelectrical impedance phase angle as a prognostic indicator in breast cancer

Background

Bioelectrical impedance analysis (BIA) is an easy-to-use, non-invasive, and reproducible technique to evaluate changes in body composition and nutritional status. Phase angle, determined by bioelectrical impedance analysis (BIA), detects changes in tissue electrical properties and has been hypothesized to be a marker of malnutrition. Since malnutrition can be found in patients with breast cancer, we investigated the prognostic role of phase angle in breast cancer.

Methods

We evaluated a case series of 259 histologically confirmed breast cancer patients treated at Cancer Treatment Centers of America. Kaplan Meier method was used to calculate survival. Cox proportional hazard models were constructed to evaluate the prognostic effect of phase angle independent of stage at diagnosis and prior treatment history. Survival was calculated as the time interval between the date of first patient visit to the hospital and the date of death from any cause or date of last contact/last known to be alive.

Results

Of 259 patients, 81 were newly diagnosed at our hospital while 178 had received prior treatment elsewhere. 56 had stage I disease at diagnosis, 110 had stage II, 46 had stage III and 34 had stage IV. The median age at diagnosis was 49 years (range 25 – 74 years). The median phase angle score was 5.6 (range = 1.5 – 8.9). Patients with phase angle <= 5.6 had a median survival of 23.1 months (95% CI: 14.2 to 31.9; n = 129), while those > 5.6 had 49.9 months (95% CI: 35.6 to 77.8; n = 130); the difference being statistically significant (p = 0.031). Multivariate Cox modeling, after adjusting for stage at diagnosis and prior treatment history found that every one unit increase in phase angle score was associated with a relative risk of 0.82 (95% CI: 0.68 to 0.99, P = 0.041). Stage at diagnosis (p = 0.006) and prior treatment history (p = 0.001) were also predictive of survival independent of each other and phase angle.

Conclusion

This study demonstrates that BIA-derived phase angle is an independent prognostic indicator in patients with breast cancer. Nutritional interventions targeted at improving phase angle could potentially lead to an improved survival in patients with breast cancer.

Hypoalbuminemia is Also a Marker of Fluid Excess Determined by Bioelectrical Impedance Parameters in Dialysis Patients

Hypoalbuminemia may be secondary to volume expansion conditions and an independent risk factor for cardiovascular disease. Bioelectrical impedance analysis (BIA) is an accurate, non-invasive method to measure body composition, especially the water compartments in humans. The aim of this cross-sectional study is to evaluate the relationship between serum albumin concentration (SA) and hydration state measured by whole BIA. The study investigated 108 non-selected patients (73 on hemodialysis, 35 on peritoneal dialysis) with a mean age of 61.4 +/- 15.6 years, 42.7% of whom were female. The patients were allotted to groups according to their SA: Group 1, < or = 3.5 g/dL; Group 2, 3.6-4.0 g/dL; and Group 3, >4.0 g/dL. The BIA parameters used included: total body water, intracellular water (ICW), extracellular water (ECW), phase angle (PA), body cell mass (BCM), ICW/ECW ratio and ICW/ECW ratio patients/controls (fluid index). Seventy-five healthy volunteers formed the control group. A strong positive correlation was found between the PA and fluid index (r (2) = 0.993, P < 0.001), as well as between the PA and SA (r = 0.386, P < 0.001), and the ICW/ECW ratio and SA (r = 0.227, P < 0.001). The ECW was negatively correlated with SA (r = -0.330, P < 0.001). Every 0.1 g/dL decrease in SA was associated with a 0.33 L increase in ECW. Group 1 patients had lower reactance (P = 0.006), PA (P < 0.001), BCM (P = 0.012), fluid index (P < 0.001) and ICW/ECW ratio (P = 0.015), and an increased ECW (NS) than groups 2 and 3. We conclude that hypoalbuminemia is also a marker of fluid excess. The SA is associated to the fluid index and the PA allows assessment of the dry weight and its variations in an individualized manner in dialysis patients.

Body Composition Assessed by Impedance Changes Very Early with Declining Renal Graft Function

BACKGROUND

Kidney transplant (Tx) restores renal filtration, although it does not achieve the function of two native kidneys, and with time it may variably involute back to chronic renal failure. We hypothesized that bioelectrical impedance analysis (BIA) might highlight differences for body compartments among Tx with different filtration rates, and we compared them with healthy controls.

METHODS

38 Tx patients (25 males, 13 females) were studied at 75.9 +/- 37.8 months postsurgery and divided into three groups: good creatinine clearance (CrCl, ml/min/1.73 m2; > 65.0), borderline (35.0 < CrCl < 60.0) and bad (CrCl < 35.0). BIA was assessed three times in a year. Total body water, extracellular water (ECW), intracellular water (ICW), Na:K exchange rate (Nae:Ke) and phase angle were studied. Healthy (n = 11) and hemodialysis (n = 11) groups were also studied.

RESULTS

BIA showed no differences between healthy controls and good Tx while both borderline and bad Tx presented a significantly higher ECW and lower ICW than either good Tx or normal controls. Only good CrCl was different from predialysis.

CONCLUSIONS

A good kidney graft manages to restore and maintain normal body composition, even with potential disturbances brought about by steroids and cyclosporine. With mild renal dysfunction a change in body compartments was observed, moving towards the composition of that with chronic renal failure patients.

Assessment of body composition in long-term hemodialysis patients: rationale and methodology

Protein-energy malnutrition is seen in patients with advanced stages of chronic kidney disease (CKD) and is even more pronounced in patients receiving long-term hemodialysis treatment. Both entities have great impact on patient morbidity and mortality. Analysis of body composition is an integral part of nutritional assessment and includes the estimation of muscle, fat, and fat-free mass, as well as the extracellular water compartment. Clinical assessment of these compartments is difficult, and gold-standard methods such as tracer dilution, magnetic resonance imaging, and dual-energy x-ray absorptiometry are expensive, cumbersome, and rarely available. We report an ongoing study of body composition in hemodialysis patients involving deuterium and sodium bromide dilution, total body potassium counting, magnetic resonance imaging, whole-body and segmental bioimpedance spectroscopy, and anthropometry. The goals of the study are (1) to validate bioimpedance technology against gold-standard methods for assessment of the various body compartments, (2) to directly quantify visceral adipose tissue mass, a potential source of cytokine production (adipokines) promoting chronic inflammation, and to study its relation to inflammatory markers, and (3) to directly quantify visceral organ mass and to study its relation to uremia toxin generation as assessed by protein catabolic rate and resting energy expenditure. Preliminary results based on up to 40 hemodialysis patients are reported.

Bioelectric impedance and individual characteristics as prognostic factors for post-operative complications

BACKGROUND AND AIMS

Malnutrition increases morbidity and mortality in surgical patients, and for this reason, several nutritional markers have been used as prognostic tools to identify surgical patients under a higher risk to develop complications in post-operative period. Few studies show the impact of nutritional markers after controlling for others variables, such as age and severity of disease. A new method, bioelectric impedance analysis (BIA), and its parameter, phase angle, have been described as a prognostic tool in several clinical situations, but they have never been studied in surgical population. The objective of this work is to assess the importance of nutritional variables and parameters from BIA as predictors of post-operative complications in a multivariable regression model.

METHODS

The nutritional status of 225 adult patients scheduled to undergo gastrointestinal surgery was assessed by several methods, including bioelectric impedance analysis and subjective global assessment. Potential confounding factors were also studied. Patients were screened for post-operative complications until hospital discharge.

RESULTS

Weight loss greater than 10%, subjective global assessment, nutritional risk assessment, ECM/BCM ratio and phase angle (from BIA) were the prognostic factors significantly associated with post-operative complications in the crude analysis. After adjusting for sex, age, marital status, tumors and pre-operative infections, only phase angle remained as a prognostic factor (RR=4.3; CI95% 1.6-11.8 for phase angle <-0.8 sd), while the other nutritional variables lost their association with post-operative complications.

CONCLUSION

Phase angle remains as an important prognostic factor for postoperative complications, even after adjusting for other individual predictors and confounders. Its utility in the identification of patients eligible for nutritional therapy has now to be evaluated.

Nutrition and Metabolism in Kidney Disease

Nutritional and metabolic derangements are highly prevalent in patients with chronic kidney disease (CKD) and patients on renal replacement therapy. These derangements, which can be termed uremic malnutrition, significantly affect the high morbidity and mortality rates observed in this patient population. Uremic malnutrition clearly is related to multiple factors encountered during the predialysis stage and during chronic dialysis therapy. Several preliminary studies suggested that interventions to improve the nutritional status and metabolic status of uremic patients actually may improve the expected outcome in these patients, although their long-term efficacy is not well established. It therefore is important to emphasize that uremic malnutrition is a major comorbid condition in CKD and renal replacement therapy patients, and that all efforts should be made to try to understand better and treat these conditions effectively to improve not only mortality but also the quality of life of chronically uremic patients. In this article we review the current state of knowledge in the field of nutrition and metabolism in all stages of CKD and renal replacement therapy, including kidney transplant. We also address questions that face investigators in this field and suggest where future research might be headed.

Bioelectrical impedance analysis: population reference values for phase angle by age and sex

BACKGROUND

Phase angle is an indicator based on reactance and resistance obtained from bioelectrical impedance analysis (BIA). Although its biological meaning is still not clear, phase angle appears to have an important prognostic role.

OBJECTIVE

The aim of this study was to estimate population averages and SDs of phase angle that can be used as reference values.

DESIGN

BIA and other methods used to evaluate body composition, including hydrodensitometry and total body water, were completed in 1967 healthy adults aged 18-94 y. Phase angle was calculated directly from body resistance and reactance, and fat mass (FM) was estimated from the combination of weight, hydrodensitometry, and total body water by using the 3-compartment Siri equation. Phase angle values were compared across categories of sex, age, body mass index (BMI), and percentage FM.

RESULTS

Phase angle was significantly (P < 0.001) smaller in women than in men and was lower with greater age (P < 0.001). Phase angle increased with an increase in BMI and was significantly inversely associated with percentage fat in men. Phase angle was significantly predicted from sex, age, BMI, and percentage FM in multiple regression models.

CONCLUSIONS

Phase angle differs across categories of sex, age, BMI, and percentage fat. These reference values can serve as a basis for phase angle evaluations in the clinical setting.

Nutritional Status and Body Composition Evolution in Early Post–Renal Transplantation: Is There a Female Advantage?

OBJECTIVE

Chronic renal failure is associated with metabolic derangements, affecting proteins, amino acids, and lipids. Usually these patients follow a restricted diet. Kidney transplant patients enjoy a recovery of renal function, but their therapeutics may entail significant changes in general metabolism. We compare the anthropometric results during the first 3 months after successful transplant for male and female patients versus a healthy group.

METHODS

Eighteen patients (11 men and 7 women) were studied. Anthropometry was assessed before and at month 1 and month 3 posttransplant including body weight (Wt), body mass index (BMI), triceps (TSF), biceps (BSF), subscapular (SCSF), and suprailiac skinfolds (SISF), midarm circumference (MAC), midarm muscle circumference (MAMC), corrected arm muscle area (CT.AMA), total body muscle mass (MM), body density (D), fat mass (FM), and fat-free mass (FFM). The healthy group was evaluated three times in the first year.

RESULTS

Pretransplant men showed lower Wt, BMI, TSF, BSF, SCSF, SISF, MAC, MAMC, CT.AMA, MM, FM and FFM than controls, while women displayed no differences from controls. By the third month, men showed only a partial recovery and women higher TSF and SCSF than controls.

CONCLUSIONS

Uremic men before transplant displayed undernutrition indices. During the first 3 months posttransplant men showed an incomplete recovery of anthropometric parameters. Quite differently, women started close to normal and had significantly increased body weight and fat content posttransplant. We suggest that nutritional requirements post-kidney grafting may be significantly different among male compared to female patients.

Sequential body composition analysis by bioimpedance early post-kidney transplantation

BACKGROUND

While chronic renal failure patients present disturbed body water composition, few studies have been done on its behavior following kidney grafting (Tx). We report the changes associated with a successful Tx on body composition evaluated by bioelectrical impedance analysis (BIA).

METHODS

Twelve Tx (seven males, five females) were studied. The BIA was assessed before Tx, at month 1 and at month 3 post-Tx. Total body water (TBW), extracellular water (ECW), intracellular water (ICW), Na:K exchange rate (Nae:Ke) and phase angle (PA) were studied. An healthy group and a HD group were evaluated three times in a year interval.

RESULTS

Comparing before Tx with month 1 post-Tx, TBW, ECW and Nae:Ke increased, while ICW and PA decreased significantly. Comparing month 1 with month 3 post-Tx, ECW decreased, while ICW and PA increased. On comparing month 1 post-Tx with the healthy group, Nae:Ke was greater and PA was lower at month 1.

CONCLUSIONS

The BIA showed that the different body water compartments of Tx recipients quickly match the constitution of normal individuals, overcoming drug therapy side effects.

Bioelectrical impedance phase angle as a prognostic indicator in advanced pancreatic cancer

Bioelectrical impedance analysis (BIA) is an easy-to-use, non-invasive and reproducible technique to evaluate changes in body composition and nutritional status. Phase angle, determined by BIA, has been found to be a prognostic indicator in several chronic conditions, such as HIV, liver cirrhosis, chronic obstructive pulmonary disease and lung cancer, and in patients undergoing dialysis. The present study investigated the prognostic role of phase angle in advanced pancreatic cancer. We evaluated a case series of fifty-eight stage IV pancreatic cancer patients treated at Cancer Treatment Centers of America at Midwestern Regional Medical Center (Zion, IL, USA) between January 2000 and July 2003. BIA was conducted on all patients using a bioelectrical impedance analyser that operated at 50 kHz. The phase angle was calculated as capacitance (Xc)/resistance (R) and expressed in degrees. The Kaplan-Meier method was used to calculate survival. Cox proportional hazard models were constructed to evaluate the prognostic effect of phase angle independent of other clinical and nutritional variables. The correlations between phase angle and traditional nutritional measures were evaluated using Pearson and Spearman coefficients. Patients with phase angle <5.0 degrees had a median survival time of 6.3 (95% CI 3.5, 9.2) months (n 29), while those with phase angle >5.0 degrees had a median survival time of 10.2 (95% CI 9.6, 10.8) months (n 29); this difference was statistically significant (P=0.02). The present study demonstrates that phase angle is a strong prognostic indicator in advanced pancreatic cancer. Similar studies in other cancer settings with larger sample sizes are needed to further validate the prognostic significance of the phase angle.

Bioelectrical impedance phase angle in clinical practice: implications for prognosis in advanced colorectal cancer

BACKGROUND

Phase angle, determined by bioelectrical impedance analysis (BIA), detects changes in tissue electrical properties and has been found to be a prognostic indicator in several chronic conditions-such as HIV, liver cirrhosis, chronic obstructive pulmonary disease, and lung cancer-and in patients receiving dialysis.

OBJECTIVE

This study was conducted to investigate the prognostic role of phase angle in advanced colorectal cancer.

DESIGN

We evaluated a case series of 52 patients with histologically confirmed stage IV colorectal cancer. BIA was conducted on all patients and phase angle was calculated. The Kaplan-Meier method was used to calculate survival. Cox proportional hazard models were constructed to evaluate the prognostic effect of phase angle independent of other clinical and nutritional variables.

RESULTS

Patients with a phase angle < or =5.57 had a median survival of 8.6 mo (95% CI: 4.8, 12.4; n=26), whereas those with a phase angle >5.57 had a median survival of 40.4 mo (95% CI: 21.9, 58.8; n=26; P=0.0001).

CONCLUSION

Phase angle is a prognostic indicator in patients with advanced colorectal cancer. Similar studies of other cancer types with larger sample sizes are needed to further validate the prognostic significance of phase angle in cancer treatment settings.

Uremic malnutrition is a predictor of death independent of inflammatory status

BACKGROUND

Several studies have pointed out the influence of nutritional parameters and/or indices of inflammation on morbidity and mortality. Often, these conditions coexist, and the relative importance of poor nutritional status and chronic inflammation in terms of predicting clinical outcomes in chronic hemodialysis (CHD) patients has not been clarified.

METHODS

We undertook a prospective cohort study analyzing time-dependent changes in several established nutritional and inflammatory markers, and their influence on mortality in 194 CHD patients (53% male, 36% white, 30% with diabetes mellitus, mean age 55.7 +/- 15.4 years) throughout a 57-month period. Serial measurements of serum concentrations of albumin, prealbumin, creatinine, transferrin, cholesterol, and C-reactive protein (CRP), as well as normalized protein catabolic rate, postdialysis weight, and phase angle and reactance by bioelectrical impedance analysis were performed every 3 months. Clinical outcomes were simultaneously assessed using indicators of mortality.

RESULTS

Serum albumin, serum prealbumin, serum creatinine, and phase angle were significant predictors of all-cause mortality, even after adjustment for serum CRP concentrations. Serum CRP concentrations were not significantly associated with mortality. Serum albumin concentrations and phase angle were also independent predictors of cardiovascular deaths in the multivariate model.

CONCLUSION

The nutritional status of CHD patients predicts mortality independent of concomitant presence or absence of inflammatory response. Prevention of, and timely intervention to treat uremic malnutrition by suitable means are necessary independent of the presence and/or therapy of inflammation in terms of improving clinical outcomes in CHD patients.

Bioimpedance analysis highlights changes in body composition at the early stages of impairment of kidney transplant function

OBJECTIVE

Kidney transplantation restores renal filtration, although it does not achieve the function of 2 native kidneys, and with time it may involute back to chronic renal failure. We hypothesized that bioelectrical impedance analysis (BIA) might highlight differences for body compartments among kidney transplants (Tx) with different filtration rates.

METHODS

Thirty transplantation patients (19 male, 11 female) were studied at 62.4+/-26.6 months postsurgery and were divided into 3 groups: good creatinine clearance (crCl, mL/min/1.73 m2; >65.0), borderline (35.0<crCl<60.0), and bad (crCl <35.0). BIA was assessed 3 times in 1 year. Total body water, extracellular water (ECW), intracellular water (ICW), Na:K exchangeable ratio (Nae:Ke), and phase angle were studied. Healthy (n=11) and hemodialysis (n=11) groups were studied as well.

RESULTS

BIA showed no differences between healthy controls and good Tx, whereas both borderline and bad Tx presented a significantly higher ECW and lower ICW than either good Tx or normal controls. Only good crCl was different from predialysis.

CONCLUSIONS

A good graft kidney manages to restore and maintain normal body composition, whereas with mild renal dysfunction a change in body compartments was observed, moving toward the body water composition of chronic renal failure patients.

Urea space and total body water measurements by stable isotopes in patients with acute renal failure

BACKGROUND

Knowledge of urea volume of distribution (Vurea) in patients with acute renal failure (ARF) is critical in order to prescribe and monitor appropriate dialytic treatment. We have recently shown that in ARF patients, Vurea estimation by urea kinetic modeling is significantly higher than total body water (TBW) by anthropometric estimation. However, these estimates of Vurea and TBW have not been validated by isotopic methods, considered as reference measurement standards.

METHODS

In this study, we measured Vurea by [13C]urea and TBW by deuterium oxide (D2O) in 21 patients with ARF (14 males, 7 females, age 62.0 +/- 10.6 years old, 83% Caucasian, 17% African American) at three different centers. These measurements were compared to TBW estimates from anthropometric and bioelectrical impedance (BIA) measurements.

RESULTS

Our results show that Vurea by [13C]urea (51.0 +/- 11.7 L) is significantly higher than TBW estimated by all other methods (TBW by D2O: 38.3 +/- 9.8 L, P < 0.001; TBW by BIA: 45.7 +/- 15.7 L, P= 0.08; TBW by Watson formula: 38.3 +/- 7.3 L, P < 0.001; TBW by Chertow formula: 39.3 +/- 7.8 L, P= 0.002, all versus Vurea). Despite significant overestimation of the absolute value and considerable variation, Vurea significantly correlated with TBW by BIA (r= 0.66, P < 0.01) and TBW by D2O (r= 0.5, P= 0.04). There was also significant correlation between D2O and BIA determined TBW (r= 0.8, P < 0.001).

CONCLUSION

In terms of useful guidelines to prescribe a specific dose of dialysis in patients with ARF, conventional estimates of TBW as surrogates for Vurea should be used with caution. We propose that these conventional estimates of TBW should be increased by approximately 20% (a factor of 1.2) to avoid significant underdialysis.

Assessment and monitoring of uremic malnutrition

Assessment and monitoring of protein and energy nutritional status are essential to prevent, diagnose, and treat uremic malnutrition, a condition highly prevalent and associated with increased morbidity and mortality in patients with advanced kidney failure. Comprehensive assessments of protein and energy nutritional status can be achieved by several measurements to quantitatively and qualitatively estimate protein content in visceral and somatic body compartments, in addition to measurements of energy balance. However, uremic malnutrition is a complex metabolic disorder in which not only net nutrient intake is lower than nutrient requirements, leading to decreased tissue function and loss of body mass, but it is also associated with many comorbid conditions. Therefore, a clinically meaningful assessment of uremic malnutrition should include methods that are able to assess clinical outcome, identify the underlying diseases, and determine whether there is potential of benefit from nutritional interventions. Such assessment usually requires using multiple measurements concomitantly, with no definitive single method that can be considered as a "gold standard." In this review, we describe the various types of methods to assess uremic malnutrition, expanding and updating data on the readily available methods, and discuss more precise techniques to estimate protein and energy homeostasis. Special considerations of specific methods related to their clinical and/or research applicability as they pertain to renal failure are also addressed.

Plasma brain natriuretic peptide concentration on assessment of hydration status in hemodialysis patient

BACKGROUND

Brain natriuretic peptide (BNP) is released into circulation in response to ventricular dilatation and pressure overload. Plasma BNP concentration correlates with left ventricular mass and dysfunction, which is prevalent in hemodialysis (HD) patients.

METHODS

To evaluate the potential of BNP level for determination of hydration status, we measured inferior vena caval diameter (IVCD) and BNP levels and performed bioimpedance analysis in 49 HD patients.

RESULTS

Pre-HD BNP levels remained unchanged after HD. Agreement between IVCD and pre-HD BNP level in overhydration was significant (kappa = 0.304). The area under the receiver operating characteristic (ROC) curve for overhydration was 0.819 for pre-HD BNP level. When extracellular fluid/total-body water (ECF/TBW) ratios of HD patients were compared with those of 723 controls, pre- and post-HD BNP levels were significantly greater in overhydrated patients. The area under the ROC curve for overhydration by ECF/TBW ratio was 0.781 for pre-HD BNP level. However, there was no significance for pre- or post-HD BNP levels on assessment of normohydration or underhydration. Pre-HD BNP level correlated significantly with post-HD BNP level, post-HD diastolic blood pressure, pulse pressure, and ECF/TBW ratio. IVCD correlated significantly with post-HD BNP level.

CONCLUSION

BNP level seems to have a limited potential for assessment of overhydration in HD patients.

Can bioelectrical impedance analysis identify malnutrition in preoperative nutrition assessment?

OBJECTIVE

Malnutrition is characterized by changes in cellular membrane integrity and alterations in fluid balance, both of which can be detected by bioelectrical impedance analysis (BIA). We investigated whether BIA-measured variables could detect malnutrition, as defined by the Subjective Global Assessment (SGA), in preoperative surgical patients.

METHODS

We prospectively evaluated 279 patients hospitalized for elective gastrointestinal surgery during the first 72 h after admission. BIA estimates were used to derive body cell mass, ratio of extracellular mass to body cell mass, and phase angle. Malnutrition diagnosed with these measures was compared with the SGA score. Receiver operating characteristic curves also were formulated to explore alternative cutoff points for one measure, phase angle.

RESULTS

A linear trend for means across SGA categories was found for all indicators used, except percentage of body cell mass. However, there was only fair overall agreement between SGA and BIA estimates. The receiver operating characteristic curves for phase angle suggested that the test was too sensitive or too specific. No alternative cutoff points resulted in suitable tests that could provide an alternative to SGA.

CONCLUSIONS

Although not in close agreement with SGA, the results suggested that there are some alterations in tissue electrical properties with malnutrition that can be detected by BIA. New cutoff points may be needed for application of BIA as a complementary method in the nutrition assessment of surgical patients.

Comparison of three methods for the determination of body fat in patients on long-term hemodialysis therapy

OBJECTIVE

To compare three simple methods of body composition analysis for the assessment of body fat in patients on long-term hemodialysis therapy.

DESIGN

Cross-sectional study using the skinfold thickness, bioelectrical impedance analysis, and near-infrared interactance techniques after a hemodialysis session.

SUBJECTS/SETTING

Ninety clinically stable patients (57 male/33 female) undergoing hemodialysis at the Dialysis Unit of the Federal University of São Paulo.

STATISTICAL ANALYSIS

Analysis of variance, intraclass correlation coefficient, and Bland-Altman plot analysis were used for the comparative analysis between the methods.

RESULTS

Body fat measurements obtained by skinfold thickness (13.5+/-6.2 kg) and bioelectrical impedance analysis (13.7+/-6.7 kg) were similar, whereas those measured by near-infrared interactance (11.3+/-5.1 kg) were significantly lower in comparison with skinfold thickness and bioelectrical impedance analysis (P<.001). The strongest intraclass correlation coefficient was found between bioelectrical impedance analysis and skinfold thickness (r=0.87), and near-infrared interactance vs skinfold thickness and bioelectrical impedance analysis methods yielded r=0.78 and r=0.76, respectively. Near-infrared interactance showed a progressive underestimation of body fat values in comparison with the bioelectrical impedance analysis technique in patients with higher amount of adiposity.

CONCLUSION

In our study, we cannot consider that one method of body composition analysis is more accurate than the other because we did not apply a gold standard method. However, the most simple, long-established, and inexpensive method of skinfold thickness seems to be still very useful to the dietitians' routine for assessing body fat in patients on long-term hemodialysis therapy.

Improvement in nutritional parameters after initiation of chronic hemodialysis

BACKGROUND

Protein-calorie malnutrition is highly prevalent in patients with chronic renal failure and on chronic dialysis therapy. Longitudinal studies evaluating nutritional outcomes after the initiation of chronic dialysis therapy in incident dialysis patients are limited.

METHODS

This prospective cohort study evaluated time-dependent changes in several well-defined markers of nutritional status before and after initiation of chronic hemodialysis therapy. Fifty incident hemodialysis (HD) patients (60% men, 38% white, 32% with insulin-dependent diabetes mellitus) were studied. Multiple nutritional markers, including biochemical parameters and analysis of body composition, were assessed before the initial outpatient CHD treatment and every 3 months thereafter for 12 months.

RESULTS

At baseline, nutritional markers correlated well with each other. After the initiation of HD therapy, there were marked improvements in most nutritional parameters, including serum albumin, serum prealbumin, normalized protein catabolic rate, fat mass, reactance, and phase angle (P < 0.05 for all). Improvements in nutritional parameters were influenced by baseline nutritional status; ie, baseline nutritional parameters were predictors of their end-of-study value.

CONCLUSION

Initiation of CHD therapy is associated with improvements in most nutritional markers. Nutritional benefits of increased solute clearance provided by the initiation of chronic dialysis therapy prevail over its potential catabolic effects. However, the extent of improvement was dependent on nutritional status at the time of initiation of dialysis therapy, which remained an important determinant of subsequent nutritional improvements during the first year of treatment.

Role of bioimpedance spectroscopy in assessment of body water compartments in hemodialysis patients

Bioimpedance spectroscopy (BIS) has been advocated as a tool to assess fluid status in hemodialysis (HD) patients. However, uncertainty remains about the reliability of BIS in patients with abnormalities in fluid status. Aims of the study are to assess the agreement between total-body water (TBW) and extracellular volume (ECW) measured by BIS and tracer dilution (deuterium oxide [D(2)O] and sodium bromide [NaBr]), the influence of the relative magnitude of water compartments (expressed as TBW(D(2)O) and ECW(NaBr):body weight) on the agreement between BIS and tracer dilution, and the ability of BIS to predict acute changes in fluid status. BIS and tracer dilution techniques were performed in 17 HD patients before a dialysis session. Moreover, the relation between BIS and gravimetric weight changes was assessed during both isolated ultrafiltration and HD. Correlation coefficients between TBW and ECW measured by BIS and tracer dilution were r = 0.71 and r = 0.71, respectively. Mean differences (tracer-BIS) were 6.9 L (limits of agreement, -1.5 to 21.6 L) for TBW and 2.3 L (limits of agreement, -1.7 to 9.7 L) for ECW. There was a significant relationship between the relative magnitude of TBW and ECW compartments and disagreement between BIS and tracer dilution (r = 0.65 and r = 0.77; P < 0.05). During both isolated ultrafiltration and HD, there was a significant relation between gravimetric changes and change in ECW(BIS) (r = 0.83 and r = 0.76; P < 0.05), but not with change in TBW(BIS). In conclusion, agreement between BIS and tracer dilution techniques in the assessment of TBW and ECW in HD patients is unsatisfactory. The discrepancy between BIS and dilution techniques is related to the relative magnitude of body water compartments. Nevertheless, BIS adequately predicted acute changes in ECW during isolated ultrafiltration and HD, in contrast to changes in TBW.