Ratio Of Extracellular Water Research Articles

A Ward-Based Procedure for Assessment of Fluid Status in Peritoneal Dialysis Patients Using Bioimpedance Spectroscopy

This study was carried out to evaluate a procedure for converting bioimpedance spectroscopy (BIS) data to a clinically useful measure of fluid status that is easily interpreted by nursing staff and patients. The ratio of extracellular water (ECW) to total body water (TBW) in a cohort of peritoneal dialysis (PD) patients was compared with the distribution for normal control subjects. The result was expressed as the difference between the measured ECW/TBW ratio and the mean ratio for age- and sex-matched controls divided by the standard deviation for the controls (the "hydration score"). Where possible, interventions were made to reduce the target weight in patients with a hydration score greater than +2.0. This clinical study was carried out in the nurse-led outpatient PD unit at St. James's University Hospital. BIS measurements were carried out during routine clinic visits. The data for the control subjects were obtained in a range of settings in the UK and the Czech Republic. 31 PD patients (21 M, 10 F; aged 19 - 78 years) who came to the PD unit for routine procedures during the study participated. The mean hydration score for PD patients was significantly higher than for the control subjects (+1.3 vs 0.0, p < 0.0001). 11 (35%) patients had a hydration score greater than +2.0, compared with only 2.5% of the controls; systolic blood pressure was greater than 130 mmHg in only two of these patients. After a 3-month follow-up, a weight reduction of 3.6 +/- 2.3 kg had been achieved in 7 patients through modality change and implementation of prescription changes, with no adverse effects. Although this was a small study, all the data collected indicated that the hydration score provides a reliable indication of fluid status in PD patients. BIS measurements are now carried out at 6-month intervals and are used to monitor the effect of interventions.

Effect of feeding malnourished patients for 1 mo on mitochondrial complex I activity and nutritional assessment measurements

We showed previously that the activity of complex I (the first enzyme of the electron transport chain) in peripheral blood mononuclear cells decreases with malnutrition and increases to a subnormal value after 1 wk of refeeding, but the traditional markers of nutritional status do not do so. The aim of this study was to ascertain whether a period of nutritional intervention longer than 1 wk would normalize complex I activity and traditional markers of nutritional status. Fifteen malnourished patients (7 women and 8 men) with > or =10% body weight loss over the previous 6 mo were studied on the day of their admission to hospital and 7, 14 and 30 d after the beginning of nutritional support. Complex I activity in peripheral blood mononuclear cells, weight, height, body composition, body water compartments, dietary intake, and serum albumin concentrations were measured on each occasion. The results before and during nutritional intervention were compared with values obtained in 30 healthy volunteers (17 women and 13 men). Complex I activity increased significantly after the first week of refeeding (P < 0.001) and reached a normal value after 1 mo of nutritional supplementation. Among the classic markers of nutritional status, only the ratio of extracellular water to intracellular water tended to decrease over the refeeding period. Complex I activity increases rapidly and is normalized by refeeding at a time when other markers of nutritional status do not change significantly.

Identification of hypertension-related QTLs in African American sib pairs.

To link hypertension-related phenotypes with chromosomal loci, genome scans were performed in 150 African American sib pairs concordant for essential hypertension. Phenotypes included blood pressure, anthropomorphic measurements, and estimates of body fluid compartments as determined by impedance plethysmography. These phenotypes were also measured in 335 normotensive African Americans. Phenotypes with LOD scores >3.3 were further evaluated for significance by use of permutation procedures. Significant linkage was detected for body mass index (BMI) on chromosomes 1 and 8 and for the ratio of extracellular water to total body water (ECF/TBW) on chromosomes 3, 5, 6, and 7. Both BMI and ECF/TBW were greater in hypertensive sibs than in normotensive subjects (P<0.001). In a subset of hypertensive sibs and normotensive subjects, average 24-hour blood pressures were correlated with ECF/TBW (P<0.01). A region linked to BMI in the hypertensive sibs corresponds to a region of conserved synteny containing blood pressure-related QTLs in an F2 cross of Brown NorwayxDahl salt-sensitive rats. Focusing on hypertension-related phenotypes is a promising approach for identifying the genetic determinants of hypertension.

Magnitude and variation of ratio of total body potassium to fat-free mass: a cellular level modeling study.

Potassium is an essential element of living organisms that is found almost exclusively in the intracellular fluid compartment. The assumed constant ratio of total body potassium (TBK) to fat-free mass (FFM) is a cornerstone of the TBK method of estimating total body fat. Although the TBK-to-FFM (TBK/FFM) ratio has been assumed constant, a large range of individual and group values is recognized. The purpose of the present study was to undertake a comprehensive analysis of biological factors that cause variation in the TBK/FFM ratio. A theoretical TBK/FFM model was developed on the cellular body composition level. This physiological model includes six factors that combine to produce the observed TBK/FFM ratio. The ratio magnitude and range, as well as the differences in the TBK/FFM ratio between men and women and variation with growth, were examined with the proposed model. The ratio of extracellular water to intracellular water (E/I) is the major factor leading to between-individual variation in the TBK/FFM ratio. The present study provides a conceptual framework for examining the separate TBK/FFM determinants and suggests important limitations of the TBK/FFM method used in estimating total body fat in humans and other mammals.

Cellular-level body composition model. A new approach to studying fat-free mass hydration.

Fat-free mass hydration, the ratio of total body water (TBW) to fat-free mass (FFM), is stable at approximately 0.73 in mammals, and this constancy provides a means of estimating total body fat in vivo. As there is no mechanistic theory to explain the magnitude and variability in TBW/FFM, the present investigation describes a cellular-level model indicating that FFM hydration is determined by four factors: body cell mass hydration, extracellular fluid hydration, ratio of extracellular solids to TBW, and ratio of extracellular water to intracellular water. According to the model, TBW/FFM can be predicted for adult humans as a mean of 0.73, and a variation range 0.69-0.77. The suggested modeling approach provides a conceptual framework for TBW-fat estimation method and identifies important areas that remain to be studied.

Analysis of body water compartments in relation to tissue depletion in clinically stable patients with chronic obstructive pulmonary disease

Tissue depletion often occurs in patients with chronic obstructive pulmonary disease (COPD), even in those that are weight-stable. Limited data are available, however, about changes in body water compartments in chronic wasting diseases such as COPD. The purpose of this study was to measure body composition in severe COPD patients with special attention to fat-free mass (FFM) depletion and the distribution of body water compartments. Total body water (TBW) and extracellular water (ECW) were measured by deuterium and sodium bromide dilution techniques, respectively, in 38 COPD patients (age: 65 +/- 9 y, forced expiratory volume in 1 s: 38 +/- 14% of predicted) in a stable clinical condition. FFM was calculated by assuming a hydration coefficient of 73%. Underweight patients [body mass index (BMI; in kg/m2) < or = 21] were characterized by a significantly lower percentage fat mass than normal-weight patients, but no significant difference was found in the ratio of ECW to intracellular water (ICW)(BMI < or = 21: 0.72 +/- 0.12, BMI > 21: 0.71 +/- 0.16; NS). When the study population was divided into depleted patients (FFM/height2 < or = 15 kg/m2) and nondepleted patients (FFM/height2 > 15 kg/m2), there was no significant difference in the percentage fat mass, but the ECW-ICW ratio was significantly higher in the depleted patients (0.78 +/- 0.16) than in the nondepleted patients (0.66 +/- 0.12, P < 0.05); this was most pronounced in women. In conclusion, it was found that COPD patients with extreme FFM wasting are characterized by an increased ECW-ICW ratio despite a relatively spared fat mass.

Body composition assessed by bioelectrical impedance analysis (BIA) in patients with Graves' disease before and after treatment.

Body composition was assessed by bioelectrical impedance analysis (BIA) in 11 female patients with Graves' disease and in 49 age-matched healthy Japanese women. Patients with Graves' disease were examined in the hyperthyroid state before treatment and in the stable euthyroid state after treatment with antihyroid drugs for 6 to 18 months. Body weight (BW), percent body fat (BF/BW), percent lean body mass (LBM/BW) and percent total body water (TBW/BW) were not statistically different between hyperthyroid Graves' patients and healthy subjects. Percent body cell mass (BCM/BW) was much lower in hyperthyroid Graves' patients than in healthy subjects (mean +/- SEM; 33.9 +/- 2.4% vs. 41.5 +/- 0.5%, P < 0.001). Percent ratio of extracellular water to total body water (ECW/TBW) was much greater in hyperthyroid Graves' patients than in healthy subjects (53.9 +/- 3.0% vs. 41.8 +/- 0.5%, P < 0.001). These abnormal ratios, BCM/BW and ECW/TBW, were normalized after treatment. Serum free T4 levels showed a positive correlation with ECW/TBW (r = 0.779) and a reverse correlation with BCM/BW (r = -0.760) in all of the patients with Graves' disease examined. These findings indicate that body composition is affected by thyroid hormones and that body composition in hyperthyroid Graves' disease is characterized by decreased BCM associated with increased ECW.

31P Magnetic Resonance Spectroscopy Demonstrates Expansion of the Extracellular Space in the Skeletal Muscle of Starved Rats

Starvation significantly alters the distribution of body water. To study the effects of starvation on cellular energetics and water distribution in skeletal muscle, a novel 31P magnetic resonance technique (31P MRS) was developed to measure water compartments. After 31P MRS-visible water space markers which distribute in total body water (dimethyl methylphosphonate, DMMP) and extracellular water (phenylphosphonate, PPA) were infused intravenously, 31P MRS spectra were obtained from the gastrocnemius muscle of male virus-free Wistar rats at baseline and after starvation or ad libitum feeding for 4 days. Muscle water spaces were also measured using the chloride method and Nernst's equation. Muscle water contents as determined by drying were equivalent in the two groups. In vivo measurements of changes in DMMP relative to all of the MRS visible phosphates also demonstrated that the total water space was similar in control and starved rats. However, starvation significantly increased the ratio of PPA/DMMP (0.67 ± 0.05 vs 0.87 ± 0.04, Control vs Starvation; P < 0.001), and therefore the ratio of extracellular water to total water in the gastrocnemius. Furthermore, because muscle water contents were comparable between the groups, this expansion of the extracellular space was accompanied by contraction of the intracellular compartment in starved animals. Equivalent changes were detected in vitro using the chloride method. Lastly, phosphocreatine/ATP ratios, which measured changes in high-energy phosphate stores, decreased after starvation (4.09 ± 0.06 vs 3.61 ± 0.06; P < 0.001) and were inversely related to changes in PPA/DMMP (r = -0.61; P < 0.001).We conclude that starvation alters the distribution of water within skeletal muscle and these changes are related to the depletion of energy stores. These phenomena can be studied simultaneously in a noninvasive fashion using in vivo31P MRS and MRS-visible water space markers.

Nutritional Aspects of Body Water Dislocations in Postoperative and Depleted Patients

Measurements of plasma volume with 125I human serum albumin, extracellular water (ECW) with 82Br-minus, and total body water (TBW) with 3-H2O were made on 16 postoperative patients, 15 depleted patients, and three control subjects. Intracellular water (ICW) was calculated as the difference between TBW and ECW. The observed findings for the series as a whole showed no change in blood volume, an increase of 3.7 I in ECW, and a decrease of 1.5 I in ICW as compared to predicted values based on current weight. Compared to predicted values based on normal (pre-illness) weight, the observed body weight decreased 16% and ICW decreased 22%; this suggests that body weight consistently under-estimates the extent of nutritional depletion. Severe depletion seen in postoperative patients indicates that frequently earlier use of total parenteral nutrition would be beneficial. ICW was found to be the most reliable single index of moderate or severe nutritional depletion; errors in estimating normal values interfere with its use in mild depletion. The ratio of ECW:TBW best reflects distortion of body water composition; it is largely independent of weight, and is a more sensitive index than absolute values of ICW. Repeat measurements of body composition were made on 9 patients given total parenteral nutrition for an average period of 18 days. On the average, there was an ECW decrease of 1.8 I, a body weight increase of 2 kg, and an ICW increase of 3.2 I after parenteral nutrition. The increased ICW represents the repletion of half of the average initial deficit of 6.1 The initial ratio of ECW:TBW of 0.58 was reduced to 0.50, returning it about three-quarters of the way to the expected normal value of 0.48. Intravenous administration of 5% glucose as sole source of calories may be a factor in distortion of body water compartments.

BODY WATER COMPARTMENTS IN THE PREMATURE INFANT, WITH SPECIAL REFERENCE TO THE EFFECTS OF THE RESPIRATORY DISTRESS SYNDROME AND OF MATERNAL DIABETES AND TOXEMIA

Normal values for both total body water and extracellular water have been determined in 86 premature infants aged 1 to 90 days and weighing 940 to 2,435 gm, with use of the techniques of deuterium oxide and bromide dilution. Nine full-term infants aged 1 to 6 days and weighing 2,590 to 4,985 gm were similarly studied. Nine infants with the respiratory distress syndrome and eight infants of toxemic mothers studied in the first 24 hours of life showed no significant difference in their body water compartments in comparison to a control group of normal infants matched for age and weight. Seven infants of diabetic mothers studied in the first 24 hours of life showed a significant decrease in total body water, expressed as percentage of body weight, with a normal intracellular to extracellular water ratio. These data indirectly support other evidence that there is an increase in body fat in these infants at birth. See Table in the PDF file

Famine Edema and the Mechanism of Its Formation

Famine edema was produced experimentally in 34 normal men who lost a quarter of their body weight while subsisting for 6 months on a European type of semi-starvation diet. The ratio of extracellular water to cellular tissue was roughly doubled. Their clinical state closely resembled that seen in Europe in 1945. There were no signs of renal or cardiac failure. The plasma protein concentration fell only slightly and the A/G ratio remained within normal limits. The venous pressure was roughly 50 per cent below normal. Data from the field lend support to these indications that famine edema is not simply a result of hypoproteinemia or of renal or cardiac failure. It is concluded that there is a dynamic nonequilibrium state of the capillary wall and, accordingly, calculations from equilibrium equations are inadmissible.