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1.
[Human Body Water Composition Measurement:Methods and Clinical Application].
Zhou, SG, Chen, W
Zhongguo yi xue ke xue yuan xue bao. Acta Academiae Medicinae Sinicae. 2018;(5):603-609
Abstract
Being the largest single component of the human body,water is essential for life. Disease can lead to salt and water imbalance, and it is particularly important to measure the content and distribution of water in body. The current body water measurement methods are still not mature,and it's even hard to measure extracellular and intracellular water. Isotope dilution method(ID),bioelectrical impedance analysis(BIA),skinfold thickness measurement,and resonant cavity perturbation(RCP)are the commonly used methods for measuring human body water composition. This paper analyzes the advantages and disadvantages of these methods and concludes that all these four methods can be used to measure total body water;more specifically,ID and BIA can measure extracellular water and intracellular water,whereas BIA is more suitable for clinical applications such as monitoring of fluid balance,guiding of fluid management,assessment of lymphedema and nutritional risk,and management of obesity. Body water measurement will play more important roles in diagnosis,prevention,treatment,and prognosis of diseases.
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Water Intake, Water Balance, and the Elusive Daily Water Requirement.
Armstrong, LE, Johnson, EC
Nutrients. 2018;(12)
Abstract
Water is essential for metabolism, substrate transport across membranes, cellular homeostasis, temperature regulation, and circulatory function. Although nutritional and physiological research teams and professional organizations have described the daily total water intakes (TWI, L/24h) and Adequate Intakes (AI) of children, women, and men, there is no widespread consensus regarding the human water requirements of different demographic groups. These requirements remain undefined because of the dynamic complexity inherent in the human water regulatory network, which involves the central nervous system and several organ systems, as well as large inter-individual differences. The present review analyzes published evidence that is relevant to these issues and presents a novel approach to assessing the daily water requirements of individuals in all sex and life-stage groups, as an alternative to AI values based on survey data. This empirical method focuses on the intensity of a specific neuroendocrine response (e.g., plasma arginine vasopressin (AVP) concentration) employed by the brain to regulate total body water volume and concentration. We consider this autonomically-controlled neuroendocrine response to be an inherent hydration biomarker and one means by which the brain maintains good health and optimal function. We also propose that this individualized method defines the elusive state of euhydration (i.e., water balance) and distinguishes it from hypohydration. Using plasma AVP concentration to analyze multiple published data sets that included both men and women, we determined that a mild neuroendocrine defense of body water commences when TWI is ˂1.8 L/24h, that 19⁻71% of adults in various countries consume less than this TWI each day, and consuming less than the 24-h water AI may influence the risk of dysfunctional metabolism and chronic diseases.
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3.
Skin hydration and lifestyle-related factors in community-dwelling older people.
Iizaka, S
Archives of gerontology and geriatrics. 2017;:121-126
Abstract
OBJECTIVE This study aimed to investigate skin hydration status of the lower legs by comparing several methods and examining lifestyle-related factors in community-dwelling older people. METHODS A cross-sectional study was conducted in three community settings in Japan from autumn to winter. Participants were older people aged ≥65 years (n=118). Skin hydration status of the lower legs was evaluated by stratum corneum hydration using an electrical device, clinical symptoms by an expert's observation and the visual analogue scale. Lifestyle factors of skin care were evaluated by a self-administered questionnaire. RESULTS The mean age of participants was 74.4 years and 83.9% were women. Stratum corneum hydration was significantly correlated with clinical scores by an expert's observation (rho=-0.46, P<0.001), but it was not correlated with the visual analogue scale (rho=-0.08, P=0.435). Among participants who did not perceive dry skin, 57.5% showed low stratum corneum hydration. Hospitalization in the past year (b=-9.4, P=0.008), excessive bathing habits (b=-4.6, P=0.014), and having an outdoor hobby (b=-5.7, P=0.007) were negatively associated, and diuretics (b=11.5, P=0.002) and lotion-type moisturizer use (b=4.6, P=0.022) were positively associated with stratum corneum hydration. CONCLUSION Stratum corneum hydration measurements show an adequate association with observation-based evaluation by an expert, but poor agreement with subjective evaluation in community-dwelling older people. Hospitalization experience and lifestyle factors are associated with skin hydration.
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4.
Effect of tolvaptan on renal water and sodium excretion and blood pressure during nitric oxide inhibition: a dose-response study in healthy subjects.
Al Therwani, S, Rosenbæk, JB, Mose, FH, Bech, JN, Pedersen, EB
BMC nephrology. 2017;(1):86
Abstract
BACKGROUND Tolvaptan is a selective vasopressin receptor antagonist. Nitric Oxide (NO) promotes renal water and sodium excretion, but the effect is unknown in the nephron's principal cells. In a dose-response study, we measured the effect of tolvaptan on renal handling of water and sodium and systemic hemodynamics, during baseline and NO-inhibition with L-NMMA (L-NG-monomethyl-arginine). METHODS In a randomized, placebo-controlled, double blind, cross over study, 15 healthy subjects received tolvaptan 15, 30 and 45 mg or placebo. L-NMMA was given as a bolus followed by continuous infusion during 60 min. We measured urine output (UO), free water clearance (CH2O), fractional excretion of sodium (FENa), urinary aquaporin-2 channels (u-AQP2) and epithelial sodium channels (u-ENaCγ), plasma vasopressin (p-AVP) and central blood pressure (cBP). RESULTS During baseline, FENa was unchanged. Tolvaptan decreased u-ENaCγ dose-dependently and increased p-AVP threefold, whereas u-AQP2 was unchanged. During tolvaptan with NO-inhibition, UO and CH2O decreased dose-dependently. FENa decreased dose-independently and u-ENaCγ remained unchanged. Central BP increased equally after all treatments. CONCLUSIONS During baseline, fractional excretion of sodium was unchanged. During tolvaptan with NO-inhibition, renal water excretion was reduced dose dependently, and renal sodium excretion was reduced unrelated to the dose, partly via an AVP dependent mechanism. Thus, tolvaptan antagonized the reduction in renal water and sodium excretion during NO-inhibition. Most likely, the lack of decrease in AQP2 excretion by tolvaptan could be attributed to a counteracting effect of the high level of p-AVP. TRIAL REGISTRATION Clinical Trial no: NCT02078973 . Registered 1 March 2014.
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5.
Myths and methodologies: Making sense of exercise mass and water balance.
Cheuvront, SN, Montain, SJ
Experimental physiology. 2017;(9):1047-1053
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Abstract
What is the topic of this review? There is a need to revisit the basic principles of exercise mass and water balance, the use of common equations and the practice of interpreting outcomes. What advances does it highlight? We propose use of the following equation as a way of simplifying exercise mass and water balance calculations in conditions where food is not consumed and waste is not excreted: ∆body mass - 0.20 g/kcal-1 = ∆body water. The relative efficacy of exercise drinking behaviours can be judged using the following equation: percentage dehydration = [(∆body mass - 0.20 g kcal-1 )/starting body mass] × 100. Changes in body mass occur because of flux in liquids, solids and gases. This knowledge is crucial for understanding metabolism, health and human water needs. In exercise science, corrections to observed changes in body mass to estimate water balance are inconsistently applied and often misinterpreted, particularly after prolonged exercise. Although acute body mass losses in response to exercise can represent a close surrogate for body water losses, the discordance between mass and water balance equivalence becomes increasingly inaccurate as more and more energy is expended. The purpose of this paper is briefly to clarify the roles that respiratory water loss, gas exchange and metabolic water production play in the correction of body mass changes for fluid balance determinations during prolonged exercise. Computations do not include waters of association with glycogen because any movement of water among body water compartments contributes nothing to water or mass flux from the body. Estimates of sweat loss from changes in body mass should adjust for non-sweat losses when possible. We propose use of the following equation as a way of simplifying the study of exercise mass and water balance: ∆body mass - 0.20 g kcal-1 = ∆body water. This equation directly controls for the influence of energy expenditure on body mass balance and the approximate offsetting equivalence of respiratory water loss and metabolic water production on body water balance. The relative efficacy of exercise drinking behaviours can be judged using the following equation: percentage dehydration = [(∆body mass - 0.20 g kcal-1 )/starting body mass] × 100.
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6.
Water balance in the fetus and neonate.
Lindower, JB
Seminars in fetal & neonatal medicine. 2017;(2):71-75
Abstract
Fetal water balance is dependent prenatally on the placental transfer of water from maternal to fetal circulation. Adequate amniotic fluid volume is one indicator of stable fetal status and development. Excessive or less than expected amniotic fluid volume may be a precursor to postnatal morbidity and mortality. Postnatal transition is marked by predictable changes in body water including contraction of extracellular volume and insensible fluid loss, primarily across the skin barrier. The degree to which these occur is determined by gestational and postnatal age. Neonatal complications and clinical conditions associated with either retention or excessive loss of body water can occur. Fluid therapy in the neonatal intensive care unit may be guided using three clinical indicators: change in body weight, serum sodium concentration, and urine output.
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7.
CORP: Improving the status quo for measuring whole body sweat losses.
Cheuvront, SN, Kenefick, RW
Journal of applied physiology (Bethesda, Md. : 1985). 2017;(3):632-636
Abstract
The measurement of whole body sweat losses (WBSL) is important to the study of body heat balance, body water balance, establishing guidelines for water and electrolyte consumption, and the study of metabolism and health. In principal, WBSL is measured by an acute change in body mass (ΔBM) in response to a thermoregulatory sweating stimulus. In this Cores of Reproducibility in Physiology (CORP) review, we revisit several basic, but rarely discussed, assumptions important to WBSL research, including the common equivalences: mass = weight = water = sweat. Sources of large potential measurement errors are also discussed, as are best practices for avoiding them. The goal of this CORP review is to ultimately improve the accuracy, reproducibility, and application of WBSL research.
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Why choose high volume online post-dilution hemodiafiltration?
Basile, C, Davenport, A, Blankestijn, PJ
Journal of nephrology. 2017;(2):181-186
Abstract
The mortality rate of patients on maintenance dialysis remains alarmingly high, at approximately 15-20 % per year. Increasing dialyzer urea clearance has not been shown to improve survival and hence interest has shifted towards convective therapies, such as hemodiafiltration (HDF) which can remove middle molecular weight uremic toxins, which have been suggested to increase mortality in patients with end-stage kidney disease. During the last few years, four large prospective randomized controlled trials (RCTs) have been conducted in different European countries to compare survival outcomes in prevalent patients receiving conventional hemodialysis with online post-dilution HDF (OL HDF). Furthermore, a pooled individual participant data analysis from four RCTs was performed and four large meta-analyses on convective therapies have been published in the last 2 years. Taken together, these studies support the conclusion that high volume post-dilution OL HDF is associated with improved overall survival. This advantage results predominantly from a lower cardiovascular mortality, possibly due to better preservation of left ventricle mass and function. Improved intra-dialytic blood pressure stability may contribute to the beneficial effect of high volume post-dilution OL HDF on survival. The beneficial effect is not restricted to selected subgroups, such as age, comorbidity or dialysis vintage. There is no compelling evidence that high volume post-dilution OL HDF reduces mortality by improvements in traditional and non-traditional risk factors. There are still no studies or case reports published describing adverse clinical outcomes in more than 20 years of HDF clinical experience. In conclusion, most of the available data support the choice of high volume post-dilution HDF over the current dialysis techniques. However, considering that we live in the era of evidence-based medicine, the evidence supporting the superiority of high volume post-dilution OL HDF in comparison to hemodialysis is still missing: in fact, a new RCT targeting different convection volumes would be needed to definitively examine the dose-response effect shown in previous studies.
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Validation of an integrative mathematical model of dehydration and rehydration in virtual humans.
Pruett, WA, Clemmer, JS, Hester, RL
Physiological reports. 2016;(22)
Abstract
Water homeostasis is one of the body's most critical tasks. Physical challenges to the body, including exercise and surgery, almost always coordinate with some change in water handling reflecting the changing needs of the body. Vasopressin is the most important hormone that contributes to short-term water homeostasis. By manipulating vascular tone and regulating water reabsorption in the collecting duct of the kidneys, vasopressin can mediate the retention or loss of fluids quickly. In this study, we validated HumMod, an integrative mathematical model of human physiology, against six different challenges to water homeostasis with special attention to the secretion of vasopressin and maintenance of electrolyte balance. The studies chosen were performed in normal men and women, and represent a broad spectrum of perturbations. HumMod successfully replicated the experimental results, remaining within 1 standard deviation of the experimental means in 138 of 161 measurements. Only three measurements lay outside of the second standard deviation. Observations were made on serum osmolarity, serum vasopressin concentration, serum sodium concentration, urine osmolarity, serum protein concentration, hematocrit, and cumulative water intake following dehydration. This validation suggests that HumMod can be used to understand water homeostasis under a variety of conditions.
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10.
Comparative study of temporary effect on the water content at different depths of the skin by hot and cold moisturizing formulations.
Cortázar, TM, Guzmán-Alonso, M, Novoa, H, Riaño, M
Skin research and technology : official journal of International Society for Bioengineering and the Skin (ISBS) [and] International Society for Digital Imaging of Skin (ISDIS) [and] International Society for Skin Imaging (ISSI). 2015;(3):265-71
Abstract
BACKGROUND Researchers have studied the water content at different skin depths. Since skin differs among tissue depth, we sought to determine the depth variability of the water content after moisturizing formulation application. Furthermore, we compared the effects of formulations with different type of manufacturing processes (hot and cold process). METHODS To characterize the variations in the water content at different depths in the skin, measurements were done on the center of the inner forearm middle line of 18 sitting healthy women, before and after 1, 3, and 5 h of the application of two different moisturizing formulations (hot and cold process). Measurements included stratum corneum hydration via capacitance (SC) at 1.25 MHz (30-40 μm), and dermal water via tissue dielectric constant (TDC) at 300 MHz to depths of 500, 1500, and 2500 μm. RESULTS There were significant differences between the SC mean values at all evaluated time intervals after application of both formulations when compared to baseline before application (T0). The SC mean values at 1 and 3 h are higher than those of the 5 h post application for both formulations. When comparing the formulations, hot formulation shows higher SC levels at 3 and 5 h, than cold formulation. TDC mean values to skin depths of 500 and 1500 μm increased after the application for both formulations. This increase was statistically significant at 1 and 3 h, when compared with T0. At 5 h no increases were seen in the TDC for any of the formulations. When comparing the mean values of each time evaluated, there is no statistically significant difference between the two formulations at depth of neither 500 μm nor 1500 μm. TDC mean value to a depth of 2500 μm does not increase after the application of any of the formulations. CONCLUSIONS Hot and cold formulations are effective moisturizers; however, a distinct profile was obtained for each. When water content averages were compared, the effect of hot formulation in the superficial layers of the skin was greater and longer in time than those of the cold formulation. On the other hand, moisturizing formulations applied to the skin affected the dermis water content until depth of 1500 μm.