Total Body Potassium Research Articles

Randomized Controlled Trial of Nutritional Counseling on Body Composition and Dietary Intake in Severe CKD

Progressive loss of kidney function results in an increased risk of malnutrition. Despite this, there is little evidence informing the impact of nutrition intervention on predialysis patients with chronic kidney disease (CKD; stages 4 and 5). Randomized controlled trial. 56 outpatients (men, 62%; mean age, 70.7 +/- 14.0 [SD] years) with CKD were randomly allocated to intervention (n = 29) or control (n = 27) by using a concealed computer-generated sequence. The intervention group, provided with individualized dietary counseling with regular follow-up aimed at achieving an intake of 0.8 to 1.0 g/kg of protein and greater than 125 kJ/kg of energy, or control, receiving written material only. Change in body composition (body cell mass, measured by means of total-body potassium, in 40 of 56 participants), nutritional status (Subjective Global Assessment), and energy and protein intake (3-day food record). During the 12 weeks, the intervention group had 3.5% (95% confidence interval, -2.1 to 9.1) less decrease in body cell mass, 17.7-kJ/kg/d (95% confidence interval, 8.2 to 27.2) greater increase in energy intake, greater improvement in Subjective Global Assessment (P < 0.01), and no significant difference in protein intake compared with the control group (-0.04 g/kg/d; 95% confidence interval, -0.73 to 0.16). The intervention was associated with greater increases in energy and protein intake in women than men (interaction P < 0.001 for both). Power to detect change in body cell mass, potential bias in ascertainment of Subjective Global Assessment. In predialysis patients with CKD, structured nutrition intervention had a greater effect on energy and protein intake in women than men. Additional investigations are warranted to determine the impact on body composition.

A Comparison of Aerobic Exercise and Resistance Training in Patients With and Without Chronic Kidney Disease

The morbidity and mortality associated with chronic kidney disease (CKD) are primarily caused by atherosclerosis and cardiovascular disease, which may be in part caused by inflammation and oxidative stress. Aerobic exercise and resistance training have been proposed as measures to combat obesity, inflammation, endothelial dysfunction, oxidative stress, insulin resistance, and progression of CKD. In non-CKD patients, aerobic exercise reduces inflammation, increases insulin sensitivity, decreases microalbuminuria, facilitates weight loss, decreases leptins, and protects against oxidative injury. In nondialysis CKD, aerobic exercise decreases microalbuminuria, protects from oxidative stress, and may increase the glomerular filtration rate (GFR). Aerobic exercise in hemodialysis patients has been reported to enhance insulin sensitivity, improve lipid profile, increase hemoglobin, increase strength, decrease blood pressure, and improve quality of life. Resistance training, in the general population, decreases C-reactive protein, increases insulin sensitivity, decreases body fat content, increases insulin-like growth factor-1 (IGF-1), and decreases microalbuminuria. In the nondialysis CKD population, resistance training has been reported to reduce inflammation, increase serum albumin, maintain body weight, increase muscle strength, increase IGF-1, and increase GFR. Resistance training in hemodialysis increases muscle strength, increases physical functionality, and improves IGF-1 status. Combined aerobic exercise and resistance training during dialysis improves muscle strength, work output, cardiac fitness, and possibly dialysis adequacy. There is a need for more investigation on the role of exercise in CKD. If the benefits of aerobic exercise and strength training in non-CKD populations can be shown to apply to CKD patients as well, renal rehabilitation will begin to play an important role in the approach to the treatment, prevention, and slowed progression of CKD.

Resting Energy Expenditure in Children With Inflammatory Bowel Disease

There is controversy in the literature regarding the effect of inflammatory bowel disease (IBD) on resting energy expenditure (REE). In many cases this may have resulted from inappropriate adjustment of REE measurements to account for differences in body composition. This article considers how to appropriately adjust measurements of REE for differences in body composition between individuals with IBD. Body composition, assessed via total body potassium to yield a measure of body cell mass (BCM), and REE measurements were performed in 41 children with Crohn disease and ulcerative colitis in the Royal Children's Hospital, Brisbane, Australia. Log-log regression was used to determine the power function to which BCM should be raised to appropriately adjust REE to account for differences in body composition between children. The appropriate value to "adjust" BCM was found to be 0.49, with a standard error of 0.10. Clearly, there is a need to adjust for differences in body composition, or at the very least body weight, in metabolic studies in children with IBD. We suggest that raising BCM to the power of 0.5 is both a numerically convenient and a statistically valid way of achieving this aim. Under circumstances in which the measurement of BCM is not available, raising body weight to the power of 0.5 remains appropriate. The important issue of whether REE is changed in cases of IBD can then be appropriately addressed.

A New Total Body Potassium Method to Estimate Total Body Skeletal Muscle Mass in Children ,

A whole body skeletal muscle [(SM); kg] mass estimation model, based on total body potassium [(TBK); mmol] measured by whole body 40K counting (WBC) was developed (SM = 0.0082·TBK) and validated in adults in a previous study. It is unknown whether the adult TBK SM prediction model is applicable for pediatric use. The aim of this study was to derive and validate a pediatric TBK SM prediction equation. SM measured by MRI was used as the criterion and TBK was measured by WBC. The protocol was completed in 116 healthy children, 66 males and 50 females, 11.7 α 3.5 y (mean α SD, range = 5–17 y). A strong linear correlation was observed between TBK and SM (r = 0.984; P < 0.001). The SM:TBK ratio was 0.0071 α 0.0008 kg/mmol in the children studied, much lower than the corresponding value of 0.0082 kg/mmol in adults. An empirical SM prediction equation was developed using TBK alone: SM = 0.0085·TBK − 2.83, r2 = 0.97, SEE = 1.39 kg. Bland-Altman analysis did not disclose a significant bias in the prediction of SM. When biological factors entered along with TBK in the general linear model, another prediction equation was developed: SM = 5.52 + 0.001·TBK (mmol) + 0.081·weight (kg) − 0.049·height (cm) + 0.00004·TBK · height + race (−0.60 for Caucasian, 0.49 for African-American, and 0 for Hispanic). Because the adult TBK SM prediction model is not applicable for pediatric use, this study provides new empirical TBK SM prediction equations that should prove useful for studies on nutrition, growth, and development in children.

Body composition of children with chronic and end‐stage renal failure

Protein energy malnutrition is common in children with chronic renal failure (CRF) and may negatively impact on clinical outcome. Although the aetiology of malnutrition is multifactorial, descriptive information on body composition may guide nutritional interventions aimed at optimising nutritional status. This prospective cohort study in children with CRF was conducted from April 1999 to November 2000. Patients were categorised according to their glomerular filtration rate (GFR) into CRF and end-stage renal failure (ESRF). Body composition was assessed based on anthropometry, total body potassium (TBK), total body protein (TBP) and dual X-ray absorptiometry (DEXA). Fifteen patients (10 male, 5 female; mean age: 13.4 +/- 4.3 years) were studied, including eight patients with CRF (mean GFR: 17.0 +/- 7.2 mL/min/1.73 m(2)) and seven patients with ESRF (mean GFR: 6.4 +/- 1.7 mL/min/1.73 m(2)). Patients in both groups (n = 15) had deficits in height and TBP (mean z-score height-for-age: -1.19 +/- 1.05, P < 0.01; mean z-score TBP: -0.71 +/- 0.71, P < 0.05). There were no significant differences in weight, height, fat-free mass, TBK and TBP between patients with CRF and ESRF. Linear growth impairment and decreased TBP are common in children with chronic and ESRF. TBK and DEXA may underestimate the degree of malnutrition in these patients.

Changes in Body Composition with Weight Loss: Obese Subjects Randomized to Surgical and Medical Programs

To assess changes in body composition with weight loss in obese subjects randomized to a laparoscopic adjustable gastric band surgical program or a medical program using a very-low-energy diet and orlistat. Using body composition measurements by DXA, neutron activation for total body nitrogen, and whole body gamma counting for total body potassium, we studied changes in fat mass, fat distribution, fat-free mass, total bone mineral content, total body protein, and body cell mass at 6 (n = 61 paired) and 24 months (n = 53 paired) after randomization. At 24 months, the surgical group had lost significantly more weight (surgical, 20.3 +/- 6.5 kg; medical, 5.9 +/- 8.0 kg). There was favorable fat-free mass to fat mass loss ratios for both groups (surgical, 1:5.5; medical, 1:5.9). Changes in total body nitrogen or potassium were favorable in each group. A small reduction in mean bone mineral content occurred throughout the study but was not associated with extent of weight loss or treatment group. At 6 months, weight loss for both groups was similar (surgical, 14.1 +/- 4.5 kg; medical, 13.3 +/- 7.3 kg). The medical program subjects lost less fat-free mass and skeletal muscle and had increased total body protein. The proportion of body fat to limb fat remained remarkably constant throughout the study. Weight loss programs used in this study induced fat loss without significant deleterious effects on the components of fat-free mass.

Evaluation of Nutrition Assessment Tools Compared With Body Cell Mass for the Assessment of Malnutrition in Chronic Kidney Disease

We compared the subjective global assessment (SGA) and a range of SGA-based assessment tools with body cell mass (BCM) in patients with stage IV and V predialysis chronic kidney disease (CKD). This was a cross-sectional, observational study. The study took place at a public tertiary hospital predialysis outpatient clinic. A total of 56 consecutive consenting patients with CKD (61% were male; age [mean +/- standard deviation] 70.2 +/- 11.6 years; glomerular filtration rate 22.2 +/- 6.8 mL/min). Nutrition status was the main outcome measure. In this population, the prevalence of malnutrition was 19.6% (n = 11, SGA B; no C ratings). Malnutrition was associated with lower BCM (mean BCM, 26.3 vs. 33.4 kg, P = .007, measured by total body potassium), body weight (64.8 vs. 76.1 kg, P = .042), body mass index (23.7 vs. 27.6 kg/m(2), P = .015), and greater weight loss over the previous 6 months (-6.2 vs. -0.1 kg, P = .004). BCM had a weak relationship with 7-point SGA (P = .267), malnutrition inflammation score (r = -0.27 P = .063), and patient-generated SGA (r = -0.27 P = .060). There was no association for either measure of nutrition status (SGA or BCM) with albumin, glomerular filtration rate, or C-reactive protein. SGA in its original form most accurately delineated malnutrition by depleted BCM and is the most appropriate tool for cross-sectional assessment of nutrition status in patients with predialysis CKD.

Extracellular water across the adult lifespan: reference values for adults

Extracellular water (ECW) is a large and clinically important body compartment that varies widely in volume both in health and disease. Interpretation of ECW measurements in the clinical setting requires consideration of potential influencing factors such as age, race, sex and other variables that influence fluid status. An important gap in physiological research is a lack of normative ECW values against which to reference perturbations in fluid homeostasis. The current study's aim was to develop conditional quantile equations for ECW based on weight, height, age, sex and race using a large (n = 1538, 854 females and 684 males) healthy adult multi-ethnic (African American, Asian, European American, Hispanic) sample. ECW was derived from total body water and potassium measured by isotope dilution and whole-body 40K counting, respectively. Quantile regression methods were used to identify five percentile levels (10th, 25th, 50th, 75th, 90th). Weight and height were significant variables at each quantile in both males and females; age made a significant contribution in the male but not the female sample. These regression equations provide ECW quantile reference values based on a large multi-ethnic adult population that should not only prove useful in clinical settings and physiological research, but serve as a model approach for developing body composition normative ranges.

Metabolic consequences of body size and body composition in hemodialysis patients

Small body mass index is associated with increased mortality in chronic hemodialysis patients. The reasons for this observation are unclear but may be related to body composition. This study aimed to investigate the body composition in chronic hemodialysis patients. The difference between body mass and the sum of muscle, bone, subcutaneous, and visceral adipose tissue masses, measured by whole body magnetic resonance imaging, was defined as the high metabolic rate compartment representing the visceral mass. Protein catabolic rate was calculated from urea kinetics. Forty chronic hemodialysis patients (mean age 54.7 years; 87.5% African Americans; 45% females) were studied. High metabolic rate compartment expressed in percent of body weight was inversely related to body weight (r=-0.475; P=0.002) and body mass index (r=-0.530; P<0.001). In a multiple linear regression model, protein catabolic rate was significantly correlated only with high metabolic rate compartment (r=0.616; P<0.001). Assuming that protein catabolic rate in addition to protein intake reflects urea and uremic toxin generation, it follows that high metabolic rate compartment is the major compartment involved in their generation. Consequently, uremic toxin production rate may be relatively higher in patients with low body weight and low body mass index as compared to their heavier counterparts. The poorer survival observed in smaller dialysis patients may be related to these relative differences.

Type 2 Pseudohypoaldosteronism: New Insights Into Renal Potassium, Sodium, and Chloride Handling

Type 2 Pseudohypoaldosteronism: New Insights Into Renal Potassium, Sodium, and Chloride Handling

Evaluation of fat-free mass by whole-body counter in Japanese healthy young adults

Whole-body counters (WBCs) are special instruments for measuring internal irradiation doses and are usually housed within or around nuclear facilities in the event of unexpected radiation emergencies. As a substantial proportion of total body potassium (TBK) is found in fat-free mass (FFM), FFM volume can be predicted from WBC-measured (40)K. We screened TBK in Japanese healthy young adults using a WBC and found strong linear correlations between TBK and lean body mass (LBM) and body mass index (r = 0.97, P < 0.01 and r = 0.47, P < 0.01, respectively). Multiple linear regression analysis, following adjustments for sex, indicates that only LBM has a significant correlation with TBK (P < 0.01). These results strongly support the feasibility of using WBCs for estimating FFM.

A new method of body habitus correction for total body potassium measurements

This paper describes an accurate and time-efficient method for the determination of total body potassium via a combination of measurements in the Birmingham whole body counter and the use of the Monte Carlo n-particle (MCNP) simulation code. In developing this method, MCNP has also been used to derive values for some components of the total measurement uncertainty which are difficult to quantify experimentally. A method is proposed for MCNP-assessed body habitus corrections based on a simple generic anthropomorphic model, scaled for individual height and weight. The use of this model increases patient comfort by reducing the need for comprehensive anthropomorphic measurements. The analysis shows that the total uncertainty in potassium weight determination by this whole body counting methodology for water-filled phantoms with a known amount of potassium is 2.7% (SD). The uncertainty in the method of body habitus correction (applicable also to phantom-based methods) is 1.5% (SD). It is concluded that this new strategy provides a sufficiently accurate model for routine clinical use.

Metabolically active portion of fat-free mass: a cellular body composition level modeling analysis.

The proportion of fat-free mass (FFM) as body cell mass (BCM) is highly related to whole body resting energy expenditure. However, the magnitude of BCM/FFM may have been underestimated in previous studies. This is because Moore's equation [BCM (kg) = 0.00833 x total body potassium (in mmol)], which was used to predict BCM, underestimates BCM by approximately 11%. The aims of the present study were to develop a theoretical BCM/FFM model at the cellular level and to explore the influences of sex, age, and adiposity on the BCM/FFM. Subjects were 112 adults who had the following measurements: total body water by (2)H(2)O or (3)H(2)O dilution; extracellular water by NaBr dilution; total body nitrogen by in vivo neutron activation analysis; and bone mineral by dual-energy X-ray absorptiometry. FFM was calculated using a multicomponent model and BCM as the difference between FFM and the sum of extracellular fluid and solids. The developed theoretical model revealed that the proportion of BCM to FFM is mainly determined by water distribution (i.e., E/I, the ratio of extracellular to intracellular water). A significant correlation (r = 0.90, P < 0.001) was present between measured and model-predicted BCM/FFM for all subjects pooled. Measured BCM/FFM [mean (SD)] was 0.584 +/- 0.041 and 0.529 +/- 0.041 for adult men and women (P < 0.001), respectively. A multiple linear regression model showed that there are independent significant associations of sex, age, and fat mass with BCM/FFM.

Enhanced Sodium Extraction with Ultrafiltration Compared to Intravenous Diuretics

Introduction: Head to head comparisons between ultrafiltration (UF) and intravenous diuretics (IVD) have consistently revealed superior volume removal and weight reduction with UF. However, the impact of these therapies in patients hospitalized with acute decompensated heart failure (ADHF) on total body sodium, potassium, and magnesium has not been described. Hypothesis: UF, beyond removing excessive volume as compared to IVD, also removes more sodium and less potassium and magnesium. Methods: Fifteen hospitalized ADHF patients with presumed diuretic resistance and clinical evidence of volume overload had their urine electrolyte concentrations measured after a dose of IVD.

Body fluid volume determination via body composition spectroscopy in health and disease

The assessment of extra-, intracellular and total body water (ECW, ICW, TBW) is important in many clinical situations. Bioimpedance spectroscopy (BIS) has advantages over dilution methods in terms of usability and reproducibility, but a careful analysis reveals systematic deviations in extremes of body composition and morbid states. Recent publications stress the need to set up and validate BIS equations in a wide variety of healthy subjects and patients with fluid imbalance. This paper presents two new equations for determination of ECW and ICW (referred to as body composition spectroscopy, BCS) based on Hanai mixture theory but corrected for body mass index (BMI). The equations were set up by means of cross validation using data of 152 subjects (120 healthy subjects, 32 dialysis patients) from three different centers. Validation was performed against bromide/deuterium dilution (NaBr, D2O) for ECW/TBW and total body potassium (TBK) for ICW. Agreement between BCS and the references (all subjects) was −0.4 ± 1.4 L (mean ± SD) for ECW, 0.2 ± 2.0 L for ICW and −0.2 ± 2.3 L for TBW. The ECW agreement between three independent reference methods (NaBr versus D2O−TBK) was −0.1 ± 1.8 L for 74 subjects from two centers. Comparing the new BCS equations with the standard Hanai approach revealed an improvement in SEE for ICW and TBW by 0.6 L (24%) for all subjects, and by 1.2 L (48%) for 24 subjects with extreme BMIs (<20 and >30). BCS may be an appropriate method for body fluid volume determination over a wide range of body compositions in different states of health and disease.

A comparative study of body potassium content in males and females at Kalpakkam (India)

A group of 300 subjects of both sexes were measured for total body potassium content using a shadow shield whole-body counting system at Kalpakkam (India). The mean body potassium content for males was 1.7 +/- 0.5 g kg(-1) body weight and 1.5 +/- 0.5 g kg(-1) body weight for females. The body potassium content varies inversely with age as well as with the body weight for both the sexes. However, the total body potassium varies directly with body-build index for both males and females. The mean annual dose due to (40)K for males and females was found to be 149 +/- 44 and 132 +/- 41 uGy, respectively.

Thiazide-Associated Glucose Abnormalities: Prognosis, Etiology, and Prevention

Thiazide diuretics have been recommended as the preferred class of antihypertensive (AHT) drugs for initial therapy and for inclusion in a regimen of multiple drugs.1 This recommendation is based on 4 decades of randomized clinical events trials with placebo (or usual care) comparators, meta-analyses of such trials, and active-controlled trials, including the very large Antihypertensive and Lipid Lowering treatment to prevent Heart Attack Trial (ALLHAT).2,3 In the latter, treatment beginning with the thiazide-like diuretic chlorthalidone reduced the risk for major coronary events (the primary outcome) similar to treatment based on representatives of newer drug classes (amlodipine, doxazosin, and lisinopril); diuretic-based treatment was more effective at preventing heart failure, and in some comparisons, other cardiovascular disease (CVD) events. However, in ALLHAT mean fasting blood glucose (FBG) and incident diabetes mellitus (IDM) were slightly but significantly increased in the chlorthalidone compared with the other arms.3 Although the design precluded distinguishing between a benefit of the alternate drugs (especially lisinopril) and an adverse effect of the diuretic, previous evidence suggested that thiazides can cause dysglycemia (impaired glucose tolerance, impaired fasting glucose, or diabetes).4 One point about the ALLHAT results that has not received enough emphasis is that if the calcium channel blocker is taken as metabolically neutral, the 4-year IDM rates in the diuretic and calcium channel blocker arms (11.6% and 9.8%, respectively) imply that 83% of IDM occurring in association with thiazide use is not because of the diuretic. Nevertheless, based on the assumption that there is a direct relationship between thiazide exposure and dysglycemia, several key questions need to be addressed: (1) What are the long-term morbidity/mortality consequences, if any? (2) What are the mechanisms? and (3) Are the changes preventable and/or reversible? The role of potassium may be important to addressing each of these issues. Evidence …

Measuring partial body potassium in the arm versus total body potassium

Skeletal muscle (SM), the body's main structural support, has been implicated in metabolic, physiological, and disease processes in humans. Despite being the largest tissue in the human body, its assessment remains difficult and indirect. However, being metabolically active it contains over 50% of the total body potassium (TBK) pool. We present our preliminary results from a new system for measuring partial body K (PBK) that presently are limited to the arm yet provide a direct and specific measure of the SM. This uniquely specific quantification of the SM mass in the arm, which is shielded from the body during measurement, allows us to simplify the assumptions used in deriving the total SM, thereby possibly improving the modeling of the human body compartments. Preliminary results show that PBK measurements are consistent with those from the TBK previously obtained from the same subjects, thus offering a simpler alternative to computed tomography and magnetic resonance imaging used for the same purposes. The PBK system, which can be set up in a physician's office or bedside in a hospital, is completely passive, safe, and inexpensive; it can be used on immobilized patients, children, pregnant women, or other at-risk populations.

Treatment of Adult Short Bowel Syndrome With Recombinant Human Growth Hormone

Extensive resection of the intestinal tract frequently results in inadequate digestion and/or absorption of nutrients, a condition known as short bowel syndrome (SBS). Several therapies, including parenteral nutrition (PN), bowel rehabilitation, and surgical procedures to reconstruct the bowel, have been used for patients with SBS. However, these treatments only partially correct the underlying problem of reduced bowel function in some patients. This review investigates the results of studies of recombinant human growth hormone (r-hGH) in patients with SBS. In one randomized, controlled and five open-label studies, treatment with r-hGH significantly increased absorption of energy, protein and/or carbohydrates. Four studies also demonstrated significantly increased body weight, lean body mass, total body potassium and/or total body water in response to r-hGH. However, in two other randomized controlled trials, r-hGH had no significant effect on energy or fluid absorption. In one randomized, controlled study and six open-label trials, treatment with r-hGH also allowed a majority of patients, including those with no colon and significant bowel resection, to eliminate or substantially reduce PN. Optimal clinical benefits appear to be achieved when r-hGH is administered in combination with a specialized oral diet and perhaps with glutamine. Although the use of r-hGH to treat SBS patients remains controversial, results from these studies suggest that short-term r-hGH treatment in combination with optimized medical and dietetic treatments can enhance bowel absorption and function and, with the continuation of optimized medical and dietetic treatments, may reduce PN requirements for a wide range of patients with SBS.

Total Body Protein Mass: Validation of Total Body Potassium Prediction Model in Children and Adolescents

Protein is an important body component for monitoring growth, development, and nutritional status. We previously developed a total body potassium (TBK, in mmol) and bone mineral (Mo, in kg) model for predicting total body protein (TBPro, in kg) in adults (TBPro = 0.00252 x TBK + 0.732 x Mo). However, the applicability of the TBK-Mo model for children is unknown. The study aims were to develop a TBK-independent 6-component (6-C) TBPro approach as the criterion, and then to validate the TBK-Mo model in children. The following measurements were made in adolescents and children (n = 62, 38 boys and 24 girls, aged 5-17 y): body weight (BW, in kg), body volume (BV, in liters) by air displacement plethysmography, total body water (TBW, in kg) by 2H2O dilution, Mo by dual-energy X-ray absorptiometry, and TBK by whole-body counting. A 6-C model was derived as TBPro = 2.922 x BW - 0.301 x TBW - 2.039 x Mo - 2.632 x BV. The TBPro estimates did not differ between the 6-C and TBK-Mo models (mean +/- SD, 0.20 +/- 0.86 kg). There was a significant correlation between TBPro by the 6-C and TBK-Mo models (r = 0.94, P < 0.001). Bland-Altman analysis indicated that the differences between TBPro by 6-C and TBK-Mo models were not significantly correlated with the mean TBPro estimates by the 2 models (r = 0.032, P > 0.05). The TBK-Mo model can thus be used to estimate TBPro in healthy adults, adolescents, and children > 5 y old.