Showing papers on "Body water published in 2013"

Hydration biomarkers in free-living adults with different levels of habitual fluid consumption

Abstract: Little is known about the impact of habitual fluid intake on physiology. Specifically, biomarkers of hydration status and body water regulation have not been adequately explored in adults who consume different fluid volumes in everyday conditions, without prolonged exercise or environmental exposure. The purpose of the present study was to compare adults with habitually different fluid intakes with respect to biomarkers implicated in the assessment of hydration status, the regulation of total body water and the risk of kidney pathologies. In the present cross-sectional study, seventy-one adults (thirty-two men, thirty-nine women, age 25–40 years) were classified according to daily fluid intake: thirty-nine low drinkers (LD; ≤ 1·2 litres/d) and thirty-two high drinkers (HD; 2–4 litres/d). During four consecutive days, urinary parameters (first morning urine (FMU) on day 1 and subsequent 24 h urine (24hU) collections), blood parameters, and food and beverage intake were assessed. ANOVA and non-parametric comparisons revealed significant differences between the LD and HD groups in 24hU volume (1·0 (se 0·1) v. 2·4 (se 0·1) litres), specific gravity (median 1·023 v. 1·010), osmolality (767 (se 27) v. 371 (se 33) mOsm/kg) and colour (3·1 (se 0·2) v. 1·8 (se 0·2)). Similarly, in the FMU, the LD group produced a smaller amount of more concentrated urine. Plasma cortisol, creatinine and arginine vasopressin concentrations were significantly higher among the LD. Plasma osmolality was similar between the groups, suggesting physiological adaptations to preserve plasma osmolality despite low fluid intake. The long-term impact of adaptations to preserve plasma osmolality must be examined, particularly in the context of renal health.

Bioelectrical impedance analysis.

Abstract: It is 50 years since Thomasett demonstrated the application of the measurement of the impedance of the human body to the estimation of total body water...

Combining creatinine and volume kinetics identifies missed cases of acute kidney injury following cardiac arrest.

Abstract: Fluid resuscitation in the critically ill often results in a positive fluid balance, potentially diluting the serum creatinine concentration and delaying diagnosis of acute kidney injury (AKI). Dilution during AKI was quantified by combining creatinine and volume kinetics to account for fluid type, and rates of fluid infusion and urine output. The model was refined using simulated patients receiving crystalloids or colloids under four glomerular filtration rate (GFR) change scenarios and then applied to a cohort of critically ill patients following cardiac arrest. The creatinine concentration decreased during six hours of fluid infusion at 1 litre-per-hour in simulated patients, irrespective of fluid type or extent of change in GFR (from 0% to 67% reduction). This delayed diagnosis of AKI by 2 to 9 hours. Crystalloids reduced creatinine concentration by 11 to 19% whereas colloids reduced concentration by 36 to 43%. The greatest reduction was at the end of the infusion period. Fluid dilution alone could not explain the rapid reduction of plasma creatinine concentration observed in 39 of 49 patients after cardiac arrest. Additional loss of creatinine production could account for those changes. AKI was suggested in six patients demonstrating little change in creatinine, since a 52 ± 13% reduction in GFR was required after accounting for fluid dilution and reduced creatinine production. Increased injury biomarkers within a few hours of cardiac arrest, including urinary cystatin C and plasma and urinary Neutrophil-Gelatinase-Associated-Lipocalin (biomarker-positive, creatinine-negative patients) also indicated AKI in these patients. Creatinine and volume kinetics combined to quantify GFR loss, even in the absence of an increase in creatinine. The model improved disease severity estimation, and demonstrated that diagnostic delays due to dilution are minimally affected by fluid type. Creatinine sampling should be delayed at least one hour following a large fluid bolus to avoid dilution. Unchanged plasma creatinine post cardiac arrest signifies renal injury and loss of function. Australian and New Zealand Clinical Trials Registry ACTRN12610001012066 .

Prevalence and risk factors of fluid overload in Southern Chinese continuous ambulatory peritoneal dialysis patients.

Abstract: Background Fluid overload is frequently present in CAPD patients and one of important predictors of mortality. The aim of this study is to investigate the prevalence and associated risk factors in a cohort study of Southern Chinese CAPD patients. Methods The patients (receiving CAPD 3 months and more) in our center were investigated from January 1, 2008 to December 31, 2009. Multi-frequency bioelectrical impedance analysis was used to assess the patient’s body composition and fluid status. Results A total of 307 CAPD patients (43% male, mean age 47.8±15.3 years) were enrolled, with a median duration of PD 14.6 (5.9–30.9) months. Fluid overload (defined by Extracellular water/Total body water (ECW/TBW)≥0.40) was present in 205 (66.8%) patients. Univariate analysis indicated that ECW/TBW were inversely associated with body mass index (r = −0.11, P = 0.047), subjective global assessment score (r = −0.11, P = 0.004), body fat mass (r = −0.15, P = 0.05), serum albumin (r = −0.32, P<0.001), creatinine (r = −0.14, P = 0.02), potassium (r = −0.15, P = 0.02), and residual urine output (r = −0.14, P = 0.01), positively associated with age (r = 0.27, P<0.001), Chalrlson Comorbidity Index score (r = 0.29, P<0.001), and systolic blood pressure (r = 0.22, P<0.001). Multivariate linear regression showed that lower serum albumin (β = −0.223, P<0.001), lower body fat mass (β = −0.166, P = 0.033), old age (β = 0.268, P<0.001), higher systolic blood pressure (β = 0.16, P = 0.006), less residual urine output (β = −0.116, P = 0.042), and lower serum potassium (β = −0.126, P = 0.03) were independently associated with higher ECW/TBW. After 1 year of follow-up, the cardiac event rate was significantly higher in the patients with fluid overload (17.1% vs 6.9%, P = 0.023) than that of the normal hydrated patients. Conclusions The prevalence of fluid overload was high in CAPD patients. Fluid overload in CAPD patients were independently associated with protein-energy wasting, old age, and decreased residual urine output. Furthermore, CAPD patients with fluid overload had higher cardiac event rate than that of normal hydrated patents.

Differences in prescribed Kt/V and delivered haemodialysis dose—why obesity makes a difference to survival for haemodialysis patients when using a ‘one size fits all’ Kt/V target

Abstract: BACKGROUND: Morbid obesity is reported to be a survival factor for haemodialysis patients compared with those with a normal body mass index (BMI), yet morbid obesity (BMI >35) is a mortality risk factor for obese patients in the general population. Traditionally, haemodialysis dosing is prescribed to achieve a target Kt/V corrected for total body water (TBW). As obese patients typically have increased body fat, which contains less water than muscle, then obese patients may have lower levels of body water than their slimmer counterparts, and as such delivered Kt/V could be greater than that estimated using standard anthropomorphic equations, and so increased dialysis dose may help explain the increased survival reported for obese patients. METHODS: We compared multi-frequency bioelectrical impedance analysis (MF-BIA) measurements of TBW in healthy haemodialysis outpatients, and compared TBW with that calculated from the Watson equation derived from anthropomorphic measurements. RESULTS: Three hundred and sixty-three adult patients, mean age 58.1 ± 16.7 years, 60.9% male and 29.9% diabetic were studied. MF-BIA-measured body composition showed that as BMI increased from 35, the percentage skeletal muscle mass fell from 42.8 ± 4.9 to 29.2 ± 5.5% (P 35; 38.9 ± 6.8 versus 44.7 ± 6.9 L, P 35; spKt/V 1.63 ± 0.48 versus 1.41 ± 0.35 and BMI 30-35; 1.65 ± 0.3 versus 1.46 ± 0.26, both P < 0.01). CONCLUSIONS: Prescribing dialysis or quantifying on-line clearance based on the anthropomorphically derived Watson equation leads to underestimation of the delivered dose to obese patients, due to changes in underlying body composition. As such, when using a 'one size fits all' target Kt/V, obese patients have an advantage over patients with normal BMI, in that they will receive a greater delivered dose of dialysis, and this may potentially explain the paradoxical survival advantage of the morbidly obese haemodialysis patient.

Is bioelectrical impedance spectroscopy accurate in estimating total body water and its compartments in elite athletes

Abstract: Background: Bioelectrical impedance spectroscopy (BIS) provides an affordable assessment of the body's various water compartments: total body water (TBW), extracellular water (ECW) and intracellular water (ICW). However, little is known of its validity in athletes. Aim: To validate TBW, ECW and ICW by BIS in elite male and female Portuguese athletes using dilution techniques (i.e. deuterium and bromide dilution) as criterion methods. Subjects and methods: Sixty-two athletes (18.5 ± 4.1 years) had TBW, ECW and ICW assessed by BIS during their respective pre-season. Results: BIS significantly under-estimated TBW by 1.0 ± 1.7 kg and ICW by 0.9 ± 1.9 kg in relation to the criterion methods, with no differences observed for ECW. The values for the concordance correlation coefficient were 0.98 for TBW and ECW and 0.95 for ICW. Bland-Altman analyses revealed no bias for the various water compartments, with the 95% confidence intervals ranging from − 4.8 to 2.6 kg for TBW, − 1.5 to 1.6 kg for ECW and − 4.5 to 2.7...

Impact of body-composition methodology on the composition of weight loss and weight gain

Abstract: We intended to (i) to compare the composition of weight loss and weight gain using densitometry, deuterium dilution (D2O), dual-energy X-ray absorptiometry (DXA), magnetic resonance imaging (MRI) and the four-compartment (4C) model and (ii) to compare regional changes in fat mass (FM), fat-free mass (FFM) and skeletal muscle as assessed by DXA and MRI. Eighty-three study participants aged between 21 and 58 years with a body mass index range of 20.2–46.8 kg/m2 had been assessed at two different occasions with a mean follow-up between 23.5 and 43.5 months. Body-weight changes within 3% of initial weight was considered as a significant weight change. There was a considerable bias between the body-composition data obtained by the individual methods. When compared with the 4C model, mean bias of D2O and densitometry was explained by the erroneous assumption of a constant hydration of FFM, thus, changes in FM were underestimated by D2O but overestimated by densitometry. Because hydration does not normalize after weight loss, all two-component models have a systematic error in weight-reduced subjects. The bias between 4C model and DXA was mainly explained by FM% at baseline, whereas FFM hydration contributed to additional 5%. As to the regional changes in body composition, DXA data had a considerable bias and, thus, cannot replace MRI. To assess changes in body composition associated with weight changes, only the 4C model and MRI can be used with confidence.

Prediction of body water compartments in preterm infants by bioelectrical impedance spectroscopy.

Abstract: To evaluate nutritional interventions in preterm infants, a simple, accurate assessment of the type of growth, that is, change in body composition through the relative contributions of lean body tissue and fat mass to weight gain, is needed. Bioelectrical impedance may provide such a method. The aim of this study was to develop resistivity coefficients appropriate for use in bioelectrical impedance spectroscopy (BIS) analysis of body water volumes in preterm infants. A total of 99 preterm infants were enrolled (mean gestational age 32 completed weeks). Total body water (TBW) and extracellular water (ECW) were determined using the reference methods of deuterium and bromide dilution. BIS measurements taken at the same time allowed calculation of resistivity coefficients. Predictions of TBW and ECW obtained using these coefficients were then validated against volumes determined using the reference methods in a separate cohort of infants. Data were available for 91 preterm infants. BIS-predicted TBW and ECW correlated well with the measured volumes (Pearson’s rp=0.825 and 0.75, respectively). There was a small bias (TBW 10 ml and ECW 40 ml) but large limits of agreement (TBW±650 ml and ECW ±360 ml). BIS appears to have limited clinical utility; however, the relatively small bias means that it may be useful for measurements within a population or for comparisons between groups in which population means rather than individual values are compared.

Intraoperative Fluids: How Much Is Too Much?

Abstract: There is increasing evidence that intraoperative fluid therapy decisions may influence postoperative outcomes. In the past, patients undergoing major surgery were often administered large volumes of crystalloid, based on a presumption of preoperative dehydration and nebulous intraoperative 'third space' fluid loss. However, positive perioperative fluid balance, with postoperative fluid-based weight gain, is associated with increased major morbidity. The concept of 'third space' fluid loss has been emphatically refuted, and preoperative dehydration has been almost eliminated by reduced fasting times and use of oral fluids up to 2 h before operation. A 'restrictive' intraoperative fluid regimen, avoiding hypovolaemia but limiting infusion to the minimum necessary, initially reduced major complications after complex surgery, but inconsistencies in defining restrictive vs liberal fluid regimens, the type of fluid infused, and in definitions of adverse outcomes have produced conflicting results in clinical trials. The advent of individualized goal-directed fluid therapy, facilitated by minimally invasive, flow-based cardiovascular monitoring, for example, oesophageal Doppler monitoring, has improved outcomes in colorectal surgery in particular, and this monitor has been approved by clinical guidance authorities. In the contrasting clinical context of relatively low-risk patients undergoing ambulatory surgery, high-volume crystalloid infusion (20-30 ml kg(-1)) reduces postoperative nausea and vomiting, dizziness, and pain. This review revises relevant physiology of body water distribution and capillary-tissue flow dynamics, outlines the rationale behind the fluid regimens mentioned above, and summarizes the current clinical evidence base for them, particularly the increasing use of individualized goal-directed fluid therapy facilitated by oesophageal Doppler monitoring.

Myocardial, Smooth Muscle, Nephron, and Collecting Duct Gene Targeting Reveals the Organ Sites of Endothelin A Receptor Antagonist Fluid Retention

Abstract: Endothelin-1 binding to endothelin A receptors (ETA) elicits profibrogenic, proinflammatory, and proliferative effects that can promote a wide variety of diseases. Although ETA antagonists are approved for the treatment of pulmonary hypertension, their clinical utility in several other diseases has been limited by fluid retention. ETA blocker-induced fluid retention could be due to inhibition of ETA activation in the heart, vasculature, and/or kidney; consequently, the current study was designed to define which of these sites are involved. Mice were generated with absence of ETA specifically in cardiomyocytes (heart), smooth muscle, the nephron, the collecting duct, or no deletion (control). Administration of the ETA antagonist ambrisentan or atrasentan for 2 weeks caused fluid retention in control mice on a high-salt diet as assessed by increases in body weight, total body water, and extracellular fluid volume (using impedance plethysmography), as well as decreases in hematocrit (hemodilution). Mice with heart ETA knockout retained fluid in a similar manner as controls when treated with ambrisentan or atrasentan. Mice with smooth muscle ETA knockout had substantially reduced fluid retention in response to either ETA antagonist. Mice with nephron or collecting duct ETA disruption were completely prevented from ETA blocker-induced fluid retention. Taken together, these findings suggest that ETA antagonist-induced fluid retention is due to a direct effect of this class of drug on the collecting duct, is partially related to the vascular action of the drugs, and is not due to alterations in cardiac function.

Interpreting common hydration biomarkers on the basis of solute and water excretion.

Abstract: This investigation evaluated 12 hydration biomarkers, to determine which represent 24-h whole-body water balance (that is, measured as water retention or clearance (WR-C) by the kidneys). Healthy males (n=59; body mass, 75.1±7.9 kg; height, 178±6 cm; age, 22±3 years; body mass index, 23.9±2.4 kg/m2) met with a registered dietitian each morning (days 1–11) to optimize completeness and accuracy of food and fluid records, then went about ordinary daily activities. These men visited the laboratory for blood samples and collected all urine produced on days 1, 3, 6, 9 and 12. The reference standard (WR-C) was calculated using 24-h urine volume, 24-h urine osmolality, and serum osmolality (single morning venous sample). Statistical regression analyses indicated that, among the 12 hydration biomarkers, only 24-h urine osmolality (r2=0.60, P 0.05) predictors of WR-C, similar to serum osmolality and other single measurements (range of r2 values, 0.19–0.0001). These observations of healthy, active young men demonstrate that WR-C is strongly related to the 24-h concentration of urine, which in turn reflects the excretion of total solids in the diet. Although morning urine assessments provided information about a single time point, 24-h urine osmolality and 24-h urine specific gravity were the best predictors of 24-h body water balance.

Measurement of interscapular brown adipose tissue of mice in differentially housed temperatures by chemical-shift-encoded water-fat MRI.

Abstract: To determine differences in fat-signal fraction (FF) from chemical-shift-encoded water-fat MRI of interscapular BAT in mice housed at different ambient temperatures (Ta ).C57BL/6J male mice (8 weeks old) were singly housed at 16°C, 23°C, or 30°C (n = 16/group) for 4 weeks. Measures included food intake, body weight (both measured weekly) and body composition (at baseline, 2, and 4 weeks post-thermal exposure); chemical-shift-encoded water-fat MRI was performed on a 9.4 Tesla Bruker magnet with respiratory gating and anesthesia at 4 weeks post-thermal exposure.A significant inverse relationship between food intake and Ta was evidenced (P < 0.0001). Lean mass was similar among groups, while total fat mass was significantly different among groups ([mean ± SE]: 30°C = 5.10 ± 0.19 g; 23°C = 4.18 ± 0.16 g; 16°C = 3.48 ± 0.54 g; P < 0.0001). Mean BAT-FF was positively related to Ta (means: 30°C = 79.4%; 23°C = 61.8%; 16°C = 50.9%; P < 0.0001).These cross-sectional results demonstrate that MRI measurement of FF within the interscapular BAT in mice reflects recent functional status of the tissue, with a lower Ta leading to a significantly reduced BAT-FF, indicative of the tissue's involvement in thermogenesis.

The evaluation of body composition, adiponectin, C-reactive protein and cholesterol levels in patients with obstructive sleep apnea syndrome.

Abstract: BACKGROUND Obstructive sleep apnea syndrome (OSAS) is a frequent disease, characterized by repetitive episodes of upper airway obstruction during sleep, leading to many pathological events. Adiponectin is an adipocyte-specific secreted protein that plays a role in glucose and lipid homeostasis, in addition to antiatherogenic and anti-diabetic effects. Bioelectrical impedance analysis (BIA) is a reliable, non-invasive, safe and effective technique to measure body composition. OBJECTIVES The aim of the study was the evaluation of body composition and adiponectin serum levels in OSAS patients and their comparison with OSAS parameters as well as with C-reactive protein (CRP) and cholesterol levels. MATERIAL AND METHODS In this study, 137 patients with OSAS and 42 persons for the control group were enrolled. In the examined group with OSAS, there were 100 males (73%) and 37 females (27%). The average age was 54.37 + 9.8 years. All subjects underwent polysomnography with Grass Aura PSG Lite and bioelectrical impedance analysis (BIA) with a single-frequency bioimpedance analyzer (Model BIA 101, AKERN-RJL, Italy). The adiponectin serum level was measured using a sandwich ELISA kit. RESULTS In OSAS patients we demonstrated a higher body mass index (BMI) and percentage of extracellular water (ECW%) and lower percentage of intracellular water (ICW%) and phase angle. Moreover, severe OSAS and control comparison revealed a lower percentage of muscle mass (MM%) in severe OSAS. Positive correlations were found between the apnea-hypopnea index (AHI) and BMI, CRP and ECW%. Negative correlations were observed between AHI and ICW%, MM% and phase angle. We found neither differences in adiponectin levels between the control group and OSAS patients nor correlations between adiponectin and body composition parameters. But we showed that adiponectin levels were significantly lower in OSAS patients with diabetes than in OSAS patients without diabetes (2.64 vs. 13.46 µg/mL, p = 0.003). In OSAS patients without diabetes, we revealed many negative correlations between adiponectin levels and the body composition parameters (including phase angle, percentage of total body water - TBW%, ICW%, percentage of fat free mass - FFM% and MM%) and triglycerides. The positive relationships were between adiponectin and CRP, ECW% and percentage of fat mass (FM%). CONCLUSIONS Our results indicate that in OSAS patients there are many changes in body composition. The most interesting are higher BMI, TBW% and ECW% and lower BCM%, IW%, MM% and phase angle. Our results suggest that OSAS does not influence adiponectin level, but adiponectin levels are lower in patients with diabetes. Adiponectin levels correlate with many body composition parameters in OSAS patients without diabetes.

Development and validation of bioelectrical impedance analysis equations for predicting total body water and fat-free mass in North-African adults

Abstract: Development and validation of bioelectrical impedance analysis equations for predicting total body water and fat-free mass in North-African adults

Bioelectrical impedance analysis for assessment of fluid status and body composition in neonates—the good, the bad and the unknown

Abstract: Bioelectrical impedance analysis for assessment of fluid status and body composition in neonates—the good, the bad and the unknown

The diagnostic accuracy of multi-frequency bioelectrical impedance analysis in diagnosing dehydration after stroke

Abstract: Background Non-invasive methods for detecting water-loss dehydration following acute stroke would be clinically useful. We evaluated the diagnostic accuracy of multi-frequency bioelectrical impedance analysis (MF-BIA) against reference standards serum osmolality and osmolarity. Material and methods Patients admitted to an acute stroke unit were recruited. Blood samples for electrolytes and osmolality were taken within 20 minutes of MF-BIA. Total body water (TBW%), intracellular (ICW%) and extracellular water (ECW%), as percentages of total body weight, were calculated by MF-BIA equipment and from impedance measures using published equations for older people. These were compared to hydration status (based on serum osmolality and calculated osmolarity). The most promising Receiver Operating Characteristics curves were plotted. Results 27 stroke patients were recruited (mean age 71.3, SD10.7). Only a TBW% cut-off at 46% was consistent with current dehydration (serum osmolality >300 mOsm/kg) and TBW% at 47% impending dehydration (calculated osmolarity ≥295-300 mOsm/L) with sensitivity and specificity both >60%. Even here diagnostic accuracy of MF-BIA was poor, a third of those with dehydration were wrongly classified as hydrated and a third classified as dehydrated were well hydrated. Secondary analyses assessing diagnostic accuracy of TBW% for men and women separately, and using TBW as a percentage of lean body mass showed some promise, but did not provide diagnostically accurate measures across the population. Conclusions MF-BIA appears ineffective at diagnosing water-loss dehydration after stroke and cannot be recommended as a test for dehydration, but separating assessment by sex, and using TBW as a percentage of lean body weight may warrant further investigation.

The effects of racial differences on body composition and total body water measured by multifrequency bioelectrical impedance analysis influence delivered Kt/V dialysis dosing.

Abstract: Introduction: Haemodialysis dosing is traditionally based on urea clearance (Kt/V). Aiming for the same Kt/V target, some racial groups have better survival. We i

Effect of dialysate sodium reduction on body water volume, blood pressure, and inflammatory markers in hemodialysis patients - A prospective randomized controlled study

Abstract: Accumulating evidence suggests an association between body volume overload and inflammation in chronic kidney diseases. The purpose of this study was to evaluate the effect of dialysate sodium concentration reduction on extracellular water volume, blood pressure (BP), and inflammatory state in hemodialysis (HD) patients. In this prospective controlled study, adult patients on HD for at least 90 days and those with C-reactive protein (CRP) levels ≥ 0.7 mg/dL were randomly allocated into two groups: group A, which included 29 patients treated with reduction of dialysate sodium concentration from 138 to 135 mEq/L; and group B, which included 23 HD patients not receiving dialysate sodium reduction (controls). Of these, 20 patients in group A and 18 in group B completed the protocol study. Inflammatory, biochemical, hematological, and nutritional markers were assessed at baseline and after 8 and 16 weeks. Baseline characteristics were not significantly different between the two groups. Group A showed a significant reduction in serum concentrations of tumor necrosis factor-α, and interleukin-6 over the study period, while the BP and extracellular water (ECW) did not change. In Group B, there were no changes in serum concentrations of inflammatory markers, BP, and ECW. Dialysate sodium reduction is associated with attenuation of the inflammatory state, without changes in the BP and ECW, suggesting inhibition of a salt-induced inflammatory response.

Aldosterone and Mortality in Hemodialysis Patients: Role of Volume Overload

Abstract: Background Elevated aldosterone is associated with increased mortality in the general population. In patients on dialysis, however, the association is reversed. This paradox may be explained by volume overload, which is associated with lower aldosterone and higher mortality. Methods We evaluated the relationship between aldosterone and outcomes in a prospective cohort of 328 hemodialysis patients stratified by the presence or absence of volume overload (defined as extracellular water/total body water >48%, as measured with bioimpedance). Baseline plasma aldosterone was measured before dialysis and categorized as low ( 280 pg/mL). Results Overall, 36% (n = 119) of the hemodialysis patients had evidence of volume overload. Baseline aldosterone was significantly lower in the presence of volume overload than in its absence. During a median follow-up of 54 months, 83 deaths and 70 cardiovascular events occurred. Cox multivariate analysis showed that by using the low aldosterone as the reference, high aldosterone was inversely associated with decreased hazard ratios for mortality (0.49; 95% confidence interval, 0.25–0.76) and first cardiovascular event (0.70; 95% confidence interval, 0.33−0.78) in the presence of volume overload. In contrast, high aldosterone was associated with an increased risk for mortality (1.97; 95% confidence interval, 1.69–3.75) and first cardiovascular event (2.01; 95% confidence interval, 1.28−4.15) in the absence of volume overload. Conclusions The inverse association of aldosterone with adverse outcomes in hemodialysis patients is due to the confounding effect of volume overload. These findings support treatment of hyperaldosteronemia in hemodialysis patients who have achieved strict volume control.

Fluid balance does not predict estimated sodium balance in critically ill mechanically ventilated patients

Abstract: Background: Distribution of total body water (TBW) depends on local and systemic factors including osmolality, relative sodium content and permeability. Although positive fluid balance has been associated with increased morbidity and mortality in critically ill patients, the mechanisms and relative roles of sodium balance and water distribution are uncertain. Objective: To track changes in sodium and fluid balance, respiratory function and body composition in patients who required mechanical ventilation for >= 48 hours. Design, setting and participants: Prospective observational study, set in a tertiary intensive care unit, of 10 patients (seven men) with a mean age of 60 years (standard deviation [SD],12 years) and mean admission Acute Physiology and Chronic Health Evaluation (APACHE) III score of 71 (SD, 26). Methods: Sodium and fluid balances were estimated daily for up to 5 days, following institution of mechanical ventilation on Day 0. Serum sodium level, oxygenation (PaO2/FIO2), body weight, intracellular and extracellular fluid (ECF) distribution (bioelectrical impedance spectroscopy), and blinded chest x-ray oedema scores were performed daily. Results: After 5 days of mechanical ventilation, the cumulative fluid balance was - 954 mL (SD, 3181 mL) and estimated cumulative sodium balance was 253 mmol (SD, 346 mmol). Serum sodium had increased from 140mmol/L (SD, 4mmol/L) to 147 mmol/L (SD, 5mmol/L). Cumulative sodium balance was weakly correlated with worsening chest x-ray score (r = 0.35, P = 0.004), a reduction in PaO2/ FIO2 ratio (r = - 0.52, P = 0.001) and 24-hour urinary sodium (r = - 0.24, P = 0.02). Between Days 1 and 5, body weight decreased (- 2.7 kg; SD, 1.4 kg) and TBW decreased (- 3.4 L; SD, 1.3 L), despite a rise in ECF distribution (1.4% of TBW; SD, 1.9% of TBW). Conclusions: Fluid balance may not reflect sodium balance in critically ill patients. As sodium balance correlates with respiratory dysfunction and increased extracellular volume, further studies examining sodium balance and morbidity seem warranted.

Associations between bioelectrical impedance parameters and cardiovascular events in chronic dialysis patients.

Abstract: Purpose Malnutrition and fluid overload contribute to the poor cardiovascular prognosis of dialysis patients. Since bioelectrical impedance analysis is an option for the evaluation of body composition and for the monitoring of hydration state, it may assist in the identification of subjects at high cardiovascular risk. The objective of this study was to evaluate the association between bioelectrical impedance parameters and cardiovascular events.

The Quantification of Body Fluid Allostasis During Exercise

Abstract: The prescription of an optimal fluid intake during exercise has been a controversial subject in sports science for at least the past decade. Only recently have guidelines evolved from ‘blanket’ prescriptions to more individualised recommendations. Currently the American College of Sports Medicine advise that sufficient fluid should be ingested to ensure that body mass (BM) loss during exercise does not exceed >2 % of starting BM so that exercise-associated medical complications will be avoided. Historically, BM changes have been used as a surrogate for fluid loss during exercise. It would be helpful to accurately determine fluid shifts in the body in order to provide physiologically appropriate fluid intake advice. The measurement of total body water via D2O is the most accurate measure to detect changes in body fluid content; other methods, including bioelectrical impedance, are less accurate. Thus, the aim of this review is to convey the current understanding of body fluid allostasis during exercise when drinking according to the dictates of thirst (ad libitum). This review examines the basis for fluid intake prescription with the use of BM, the concepts of ‘voluntary and involuntary dehydration’ and the major routes by which the body gains and loses fluid during exercise.

Changes in upper limb extracellular water content during hemodialysis measured by multi-frequency bioimpedance.

Abstract: IntroductionHemodialysis patients are at risk of chronic volume overload, with consequent increased cardiovascular morbidity and mortality. Multifrequency bioimpedance allows assessment of body flu...