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During exercise water and electrolytes are lost in sweat. There is a large variation in both sweat rate and sweat composition and as a consequence sweat electrolyte loss can be large, especially for sodium, the primary cation in sweat. The loss of large amounts of sodium in sweat has been linked with hyponatraemia and muscle cramps. Sodium intake is encouraged in some athletes and in some exercise situations, which is in direct contrast to guidelines aimed at the general population aimed at reducing average sodium intakes to 2.4g of sodium per day (6g salt/day). Dietary sodium intakes have been determined by numerous methods, including weighed dietary records and 24h urine collections. As dietary sodium intake in excess of basal requirement is primarily excreted in the urine in non-sweating individuals, and the basal requirement for sodium is small, 24h urine collections can provide an accurate estimate of dietary sodium intake. In Chapter 3, 24h urinary sodium excretion was measured in eighteen subjects on 4 separate occasions. Subjects consumed their normal diet with the exception of a 5g creatine supplement and 500ml of water, which was part of a separate investigation. The relationship between urine sodium excretion in each 24h collection period was weak, but on average males excreted 200 ± 48mmol of sodium per day and females excreted 157 ± 33mmol of sodium per day, which is equivalent to 4.6g and 3.6g of sodium, respectively. This is in excess of the current recommended intake. In chapter 4, the variation in sodium excretion was determined in eight subjects who consumed the same diet for 5 consecutive days. Despite the similar intake of sodium each day, a day to day variation in sodium excretion of 13% was still observed. This was not related to either sodium intake or potassium intake. In chapter 5, nine subjects consumed their normal diet for 5 consecutive days but weighed and recorded all food and drink consumed. During this period, 24h urine samples were also collected. No strenuous exercise was permitted apart from an exercise task on day 4. This involved intermittent cycling in the heat until 2% body mass (BM) was lost. Sweat was collected from four absorbent patches placed on the back, chest, forearm and thigh. Sweat sodium concentration was adjusted to account for the 35% over-estimation using this regional collection method. Subjects lost 1.51 ± 0.19L of sweat and 66 ± 16mmol (range 32 86mmol) of sodium. There was no difference in sodium balance between each 24h period due to a significant decrease in urine sodium excretion on the day of exercise (day 4). In chapter 6, the effect of prior exercise on sweat composition during a second exercise bout completed later that same day was determined. Eight healthy males cycled for 40 minutes in the heat on one or two occasions. A period of 5h elapsed between exercise bouts when two exercise sessions were performed. Sweat was collected using a whole body washdown method and by 4 absorbent patches placed on the back, chest, forearm and thigh. The main finding was that prior exercise did not affect sweat rate or sweat sodium, potassium and chloride concentrations in the second exercise bout when using the whole body washdown method. Chapter 7 determined the effects of two exercise sessions completed on the same day on electrolyte balance. Nine subjects followed their normal dietary behaviour but weighed and recorded all food and drink consumed during 5 consecutive days. During this period 24h urine samples were also collected. No strenuous exercise was permitted during this period apart from two exercise tasks on day 4. During exercise sweat was collected using a whole body washdown technique. Sweat rate and sweat sodium, potassium and chloride concentrations during the second exercise bout were found to be similar to the first exercise bout. Subjects lost 2.64L (range 1.80 3.48L) of sweat and 138 ± 106mmol of sodium (range 32 287mmol). Sodium balance was not significantly affected on the day of exercise, but urine sodium was lower than dietary sodium intake on the day of exercise (Day 4) and the day following exercise (day 5), indicating significant sodium conservation by the kidney. In contrast, no change in sodium intake was observed. In chapter 8, the effect of skimmed milk and a sports drink in restoring fluid balance was examined following exercise-induced dehydration. Seven physically active males cycled intermittently in the heat until 2% BM was lost. During a 1h rehydration period a sports drink (23mmol Na+/L) or skimmed milk (32mmol Na+/L) was consumed in a volume equivalent to 150% of BM loss. Fluid balance at the end of the 3h recovery period tended to be more positive when milk was consumed. Despite this, no difference in exercise capacity in the heat was observed. This thesis shows that exercise did not increase sodium intake, but this may be due to the already high dietary sodium intake of individuals. Sodium balance was maintained in the majority of individuals due to a significant conservation of sodium by the kidneys. When sweat sodium losses are large, urine sodium conservation may not be sufficient to prevent a negative sodium balance. When no food is consumed in the acute period post-exercise, the higher sodium content of skimmed milk than a sports drink may be partly responsible for the increased retention of the ingested fluid. But this did not enhance subsequent performance in the heat.

The aim of this study was to evaluate the fluid balance of polytrauma patients hospitalized in the intensive care unit at the University Hospital in Hradec Kralove. Very little knowledge about this issue can be found; therefore we tried to clarify how the body responds to trauma and whether it is possible to influence the further course of the disease by controlling the amount of administered fluid. The study included 13 patients, 12 men and 1 woman with different length of hospitalization. The examination of the patients was carried out by the bioelectrical impedance analysis of the body composition which is able to determine the proportion of individual body components (water, muscle mass, fat). All the patients were examined twice, each after a different time period. Other data were collected from medical documentation related to fluid balance and laboratory results. After assessing the results we discovered differences in the measured values in the first and second test. While during the first examination no statistical correlation between the distribution of the fluids in the body and the intake and output was found, the second examination showed a statistically significant relationship between the fluid intake and subsequent body composition (fluid overload, total body water, extra and...

Fluid balance is critical for cells to maintain at homeostasis as disturbances in it can disrupt cellular function and consequently the physiology of an organism. Fluid loss for an organism can be classified as either intra- or extracellular, and it appears that different mechanisms have developed to restore homeostasis after intra- or extracellular dehydration. The renin-angiotensin system (RAS) has been shown to be an important mediator of extracellular dehydration induced fluid intake. Various lines of evidence have demonstrated the importance of the subfornical organ (SFO) to mediate fluid intake, especially due to the RAS, and we have shown that production and action of angiotensin (ANG) at the SFO is necessary for fluid intake due to ANG within the brain. Protein kinase C (PKC), specifically PKC-a;, is shown to be a necessary and sufficienty sufficient effector in the SFO to mediate brain angiotensin-II (ANG-II) polydipsia. It is also demonstrated that production of ANG from the SFO is sufficient to increase fluid intake through the ANG-II type 1 (AT1R) receptor and PKC. While production of ANG from the SFO is sufficient to increase fluid intake it is not sufficient to increase blood pressure, metabolism, or sodium appetite. Thus, production and action of ANG to activate PKC-a; is both necessary and sufficient to increase fluid intake at the SFO, and the fluid, pressor, and metabolic phenotypes of brain ANG through the SFO can be separated.

This study was undertaken to locate and characterise the neurons in the central nervous system that project to the kidney. In particular, the aim was to illustrate and characterise the neural link between regions in the hypothalamus known to influence renal function and fluid balance, and nerves known to innervate the kidney.

Adequate fluid consumption is central to human survival. Previous literature suggests that there some misconceptions regarding hydration and fluid balance in some populations. Available data also show that the role of thirst sensations in maintaining fluid balance in different settings is also equivocal. Therefore, this thesis aimed to examine the perception of hydration, thirst and fluid intake in freeliving populations, to examine the feasibility of thirst as a marker of hydration status and to investigate the effect of thirst related sensations on fluid balance in resting and exercising individuals under different ambient temperatures. The findings in this thesis (Chapter 3) show that individuals who work within the fitness industry demonstrated substantial knowledge about drinking practices, hydration status and health consequences of water consumption, but lack understanding on the type of beverages that adequately hydrate the body. Further, thirst perception and mood states did not affect (P>0.05) the fluid intake in free living individuals (Chapter 4) and resting individuals under cool and warm exposure (Chapter 6), but some other factors such as subjective feelings of mouth dryness and the extent of hydration status might influence the fluid intake behaviour in these populations. In addition, following ingestion of flavoured carbohydrate drinks, thirst sensations was rated lower over time (P<0.05) during exercise in the cool, but was higher over time in the warm temperature (Chapter 7). Moreover, subjective feelings related to dehydration such as mouth dryness, thirst perception, desire to drink (water pleasantness) and hunger rating could be used as index of hydration status to signify at least a 1% body mass loss due to food and fluid restriction in resting individuals (Chapter 5). In conclusion, the findings in this thesis provide some new insight with respect to hydration, thirst and fluid balance in different populations under different settings. Nevertheless, some inconclusive findings regarding the role of thirst related sensations in fluid balance require further investigations.

abstract: Exposure to sun radiation (SUR) with ambient temperature may be an influencer on athletes’ sweat loss in different environments, but the results are not currently known. The purpose of this study was to determine the effects of SUR on fluid balance (FB) and hydration status (HS) in athletes exercising indoors and outdoors. Initial FB and HS were assessed in NCAA-DI female soccer athletes (n=10) of a single team in temperate, dry conditions (55-68°F, 18-48% humidity) who were monitored during 3 practices of equal estimated energy expenditure (EE): two outdoors in direct SUR (cold/moderate temperatures) and one indoors without SUR (moderate temperatures). Humidity, temperature, and wet bulb globe temperature (WBGT – a measurement partly based on SUR, including ambient temperature/relative humidity) were recorded using Heat Stress Meters placed in the direct sun or in the shade. Each athlete’s semi-nude dry body weight was recorded before and after exercise. Urine samples were taken before, after, and the morning after. Urine specific gravity (USG) was tested to assess HS. Athletes wore combined heart rate and activity monitors to estimate EE and were provided ad libitum water and/or a zero-calorie sports drink. Their total intake included weights of consumed food and drink. Sweat rate was calculated using body weight change and intakes of liquids minus urine losses/hour. Two-way repeated measures ANOVA analyzed group-level differences. No significance was found in total FB (1.01±0.32 L/hr) or EE/hr (444±97.1 kcal/hr) across all days (p>0.05). In analyzing individual athlete results, 40% had consistent USG >1.025 (p=0.001) suggesting potential dehydration. These 4 athletes selected water as their beverage, of which is known that consuming only water does not stimulate drinking behavior as does electrolyte drinks. The remaining 60% were overall not dehydrated (USG <1.025) but must be aware of incidental dehydration in hotter temperatures. The conclusion is that in low-moderate temperatures, athletes self-regulate drinking habits and achieve fluid balance during exercise with or without sun radiation. However, athletes with average USG >1.025 are likely to remain dehydrated in moderate temperatures. The findings suggest that more education would benefit these athletes by ensuring hydration in any environment. / Dissertation/Thesis / Masters Thesis Nutrition 2019

Epithelial sodium channels (ENaC) are located throughout the epithelial lining of the respiratory tract and play a crucial role in ion and fluid homeostasis of the lungs. Increasing ENaC activity through stimulation of β₂-adrenergic receptors has been shown to increase sodium and fluid reabsorption from the airspace to the interstitial space. In cystic fibrosis lung disease there is a hyperabsorption of sodium through ENaC which results in dehydration of the airway surface liquid. Previous work has identified a common functional genetic variant of SCNN1A, the gene encoding the ENaC alpha-subunit. This variant manifests as an alanine to threonine substitution at amino acid 663 (T663), with the T663 variant resulting in a more active channel due to a greater number of channels in the membrane. We sought to determine the influence of the T663 variant on exhaled ions, pulmonary function, and the diffusing capacity of the lungs in healthy subjects as well as in patients with cystic fibrosis. We used exercise, which can increase endogenous epinephrine by up to 1000 fold at peak exercise, and albuterol, an exogenous β₂-adrenergic agonist, to stimulate ENaC activity. In healthy individuals we hypothesized that the T663 variant would be beneficial for lung function due to a greater fluid removal, which could improve gas transfer in a healthy lung. In the CF patients we predicted that the T663 variant would be detrimental to lung function due to an exaggerated absorption of sodium and drying/thickening of the mucus layer in the airways. Measurements of exhaled sodium were made in the healthy subjects at baseline, 30, 60, and 90 minutes post-albuterol administration. Subjects with the A663 variant had higher baseline exhaled sodium and a significant decrease in exhaled sodium by 90 minutes after β₂-adrenergic stimulation with albuterol, suggesting a removal of sodium from the airways. No changes in exhaled sodium were seen in the T663 variant in response to albuterol. In response to exercise the A663 variant had a greater increase in the diffusing capacity of the lung than the T663 variant, possibly due to differences in alveolar sodium and therefore fluid handling. Taken together, these results suggest that healthy humans with the A663 variant can increase ENaC activity in response to β₂-adrenergic stimulation, whereas individuals with the T663 variant have a diminished capacity for increasing ENaC activity in response to β₂-adrenergic stimulation. In CF patients, the T663 variant had significantly lower baseline pulmonary function, weight, and body mass index. In response to exercise, patients with the T663 variant had a greater increase in the diffusing capacity of the lungs, possibly due to purinergic inhibition of ENaC. Finally, we recruited additional CF patients to confirm our pulmonary function findings. Individuals with at least one allele resulting in the T663 variant had significantly lower body mass index, and tended to have lower exhaled chloride and pulmonary function. These results suggest greater dehydration of the lung in CF patients with the T663 variant. Overall, these results may suggest that the T663 variant modifies disease severity in CF, although more work is certainly warranted to confirm this result.

Akutsjukvård är tidskänsliga vårdinsatser som ges till patienter som drabbas av akut sjukdom. Akut sjukdom kan innebära försämring av kronisk sjukdom eller nytillkommen plötslig ohälsa i behov av snabb handläggning. När en patient drabbas av akut sjukdom ökar risken för vätskebalansrubbningar, exempelvis dehydrering och hyperhydrering. Vätskebalansrubbningar kan leda till ökad ohälsa samt ökade samhällskostnader. Sjuksköterskan ansvarar för bedömning och dokumentation av vätskebalans. Detta ska göras med en helhetssyn och består till stor del av tre komponenter; bedömning av kliniskt status, klinisk kemi och dokumentation i vätskebalanslistor. Hantering av den akut sjuka patientens vätskebalans utgör en avgörande del av patientens vård. Då bedömning och dokumentation av vätskebalans syftar till att tidigt upptäcka inadekvat vätskebalans innebär suboptimal hantering en ökad risk för vårdskada hos patienten. Syftet var att belysa sjuksköterskans genomförande av bedömning och dokumentation av vätskebalans hos patienter som vårdas inom akutsjukvård. Metoden litteraturöversikt valdes för att besvara studiens syfte. Endast studier publicerade mellan åren 2007-2017 samt genomförda inom en akutsjukvårdskontext på vuxna patienter inkluderades. Datainsamlingen skedde genom sökning i de elektroniska databaserna PubMed, CINAHL complete, MEDLINE samt SveMed+ med indexeringsord och fritextord baserade på litteraturöversiktens syfte. Därtill genomfördes en manuell sökning. Datainsamlingen resulterade i att 17 originalartiklar inkluderades i litteraturöversikten. Artiklarnas kvalitet granskades mha Sophiahemmet Högskolas bedömningsunderlag för vetenskaplig klassificering samt kvalitet. Artiklarnas resultat analyserades med integrerad analys och presenterades därefter i en integrerad text. Resultatet visade att det fanns brister i sjuksköterskans bedömning och dokumentation av vätskebalans. Det fanns en fördröjning i agerande vid upptäckt av vätskebalansrubbningar och onormala värden i den kliniska kemin. Sjuksköterskan dokumenterade inte patientens vätskebalans i vätskebalanslista eller kroppsvikt på ett tillfredsställande vis. Faktorer som kunde påverka sjuksköterskans bedömning och dokumentation av vätskebalans var kommunikation, kunskap och patientens sjukdomstillstånd. Därtill indikerade resultatet att de mätmetoder som används för att bedöma vätskebalans inte verkar helt ändamålsenliga för äldre patienter, vilket gällande riktlinjer inte tillsynes tar hänsyn till. Vidare forskning behövs för att kartlägga detta vidare. Slutsatsen av litteraturöversiktens resultat indikerar att sjuksköterskans bedömning och dokumentation av vätskebalans idag är bristfällig. Insatser f  f ör att öka sjuksköterskans kunskap kring vätskebalans torde vara av värde för att förbättra detta. Vidare forskning behövs för att utvärdera huruvida de mätmetoder som används för bedömning och dokumentation av vätskebalans är väl lämpade för akutsjukvård. / Acute care is time sensitive care interventions given to patients who are acutely ill. Acute illness may imply deterioration of chronic disease or newly sudden illness that needs urgent treatment. In this state the risk of fluid balance disorders, such as dehydration and hyperhydration, increases. Fluid balance disorders may lead to increased morbidity and social costs. The nurse has a responsibility to assess and document fluid balance. This should be done with a holistic view and largely consists of three components; assessment of clinical status, clinical chemistry and documentation in fluid balance charts. Fluid balance management in the care of the acutely ill is a fundamental part of patient care. The aim of the assessment and documentation of fluid balance is to discover deviations early, and a suboptimal management of fluid balance implies an increases risk of care related injury. The aim was to illuminate the nurse’s implementation of fluid balance assessment and documentation in patients within acute care. The study was executed through a literature review. Only articles published between 2007 and 2017, conducted in acute care settings and of adult patients were included. The data collection was carried out using the electronic databases PubMed, CINAHL complete, MEDLINE and SveMed+ using keywords based on the purpose of the literature review. Both thesaurus and free text words were used as keywords. Thereafter a manual search was performed. The data collection process resulted in 17 original articles that were included in the literature review. The quality of the articles was assessed using the review template compiled by Sophiahemmet University. The results of the articles were analyzed using integrated analysis and presented within an integrated text. The findings revealed shortcomings in the nurse’s assessment and documentation of fluid balance. There was a delay in action after the detection of fluid imbalances and abnormal values ​​in the clinical chemistry. The nurse did not adequately document the patient's bodyweight or fluid balance in the fluid balance chart. Factors such as communication, knowledge, and the patient’s medical condition could affect the nurse’s assessment and documentation of fluid balance. In addition, the findings indicated that the measurement methods used to assess fluid balance do not appear to be entirely suitable for elderly patients. Applicable guidelines do not seem to recognize the diverse needs of these patients. Additional research is needed to explore this further. The conclusions of this literature review indicates that the nursing assessment and documentation of fluid balance is inadequate. Efforts to increase the nurse’s knowledge of fluid balance might be of value to improve this. Further research is needed to evaluate whether the measurement methods used for the assessment and documentation of the fluid balance are well suited for acute care settings.

<p> Subcutaneous injection of formalin produced acute sodium deficiency in rats, characterized by marked hypovolemia and hyponatremia, due to an extravascular leakage of plasma and destruction of cells at the injection site. This reduction in intravascular fluid volume elicited both behavioral and physiological mechanisms of fluid restoration: sodium appetite and thirst as well as renal retention of sodium and water. Appetite and retention evolved together but intakes continued well after retention ceased and plasma volume and sodium concentration were restored to normal. These results indicate that appetite alone is not a true indicator or need, and that sodium and water balances (intake - excretion) must be considered in defining the deficient state.</p> / Thesis / Master of Arts (MA)