Thirst in the elderly with and without heart failure. Arch Gerontol Geriatr. 2011;53:174-178. [PMID: 21035203 DOI: 10.1016/j.archger.2010.10.003]

Is the NICE Guideline for maintenance fluid therapy in adults in hospital appropriate?

BACKGROUND AND AIMS

The National Institute for Health and Care Excellence's (NICE) Guideline for Maintenance Fluid Therapy in Adults in Hospital is widely used, but the recommendations have not been evaluated properly. In this study, we investigated whether the recommendation of providing 25-30 mL/kg/day of fluid and 1 mmol/kg each of sodium and potassium is sufficient for human needs.

METHODS

First, we calculated the distribution of fluid between the extracellular fluid volume (ECV) and intracellular fluid volume (ICV) during a cross-over infusion experiment where 12 volunteers received 25 mL/kg/day of either a high-sodium (154 mmol/L) or low-sodium (54 mmol/L) solution over 48 h. Second, urine samples from 719 volunteers and clinical patients were used to quantify their renal water conservation and excretion of sodium and potassium. Third, retrospective analysis of a diet study was used to extrapolate how large the fluid intake and the electrolyte excretion likely had been in the 719 volunteers and hospital patients who delivered urine.

RESULTS

The high-sodium fluid maintained the ECV but the ICV had decreased by 1.3 L after 48 h. The low-sodium fluid resulted in a volume deficit of 1.7 L that equally affected the ECV and the ICV. Regression equations based on the diet study suggested that the daily intake of water in the 719 subjects averaged 2.6 L and that 2 mmol/kg of sodium and 1 mmol/kg of potassium was excreted.

CONCLUSION

The NICE guideline recommends too little water and sodium for a human to adequately maintain the ECV and ICV.

CLINICAL TRIAL REGISTRATIONS

EudraCT 2016-001846-24 and ISRCTN 12215472.

Thirst symptoms in patients with heart failure: An integrative review

AIM

To identify the risk and protective factors affecting thirst symptoms in patients with heart failure (HF) and intervention strategies to alleviate thirst symptoms.

DESIGN

An integrative review.

METHODS

A total of 61 articles were retrieved. Screening yielded a total of 21 articles which were appraised for quality. The quality of studies was assessed using the Mixed Methods Appraisal Tool.

DATA SOURCES

Ten electronic databases were searched in October 2023, including Embase, Pubmed, CINAHL, Cochrane, Web of Science, Wiley, CNKI, VIP, CBM and WanFang. In addition, we searched grey databases and manually searched reference lists of included and relevant reviews.

RESULTS

In total, 1644 articles were retrieved, of which 21 were included. Eight studies addressed the factors. Six themes emerged as risk factors, including demographics, severity of disease, psycho-environmental, medication, fluid restriction and homeostasis. Conversely, an increase in fluid intake, a high score of sodium restriction diet attitude and using ARB were identified as protective factors. Thirteen studies focus on intervention strategies. Five unique intervention strategies were identified, including Traditional Chinese Medicine, mint-related interventions, sour-flavour interventions, improved water restriction and cluster nursing strategy.

CONCLUSION

This finding identified the factors associated with thirst symptoms in patients with HF, especially concerning the elaboration of risk factors, which suggests that healthcare professionals should focus on the risk factors for thirst in patients with HF and consciously avoid the occurrence of these risk factors. Additionally, there are considerable cultural differences in interventions, therefore, to increase adherence during symptom management, careful selection of appropriate intervention strategies based on the requirements and preferences of patients is required. While there are some therapies, there aren't enough high-quality empirical investigations. Thus, multi-centre, large-sample studies are also required in subsequent research to demonstrate the interventions' effectiveness.

IMPLICATIONS FOR THE PROFESSION

The nurse must notice the symptoms of thirst in HF to slow down the disease's progression and improve the patient's physical and emotional well-being.

REPORTING METHOD

The review complies with the PRISMA guidelines for reporting systematic reviews.

PATIENT OR PUBLIC CONTRIBUTION

No patient or public contribution.

Detection of low urine output by measuring urinary biomarkers

BACKGROUND

Urine output < 1 L per 24 h is a clinical warning sign that requires attention from hospital staff, who should determine whether the low flow is due to low habitual intake of water or disease-induced dehydration. The incidence of this condition is unclear.

METHODS

A cohort of 20 healthy volunteers (mean age 42 years, range 23-62 years) recorded their food and water intakes daily for 8 days. They also collected and measured all urine and delivered first morning urine samples for analysis of osmolality and creatinine. Optimal cutoffs for these biomarkers to indicate urine output of < 1 L or 15 mL/kg during the preceding 24 h were applied with and without correction for age to cross-sectional data from 1,316 subjects in various clinical settings, including healthy volunteers, preoperative patients, patients seeking acute care at a hospital, and patients receiving institutional geriatric care.

RESULTS

The urine output amounted to < 1 L during 22 of the 159 evaluable study days and was indicated by urine osmolality > 760 mosmol/kg or urine creatinine > 13 mmol/L, which had sensitivity and specificity of approximately 80%. Days with urine output < 1 L were associated with significantly less intake of both water (-41%) and calories (-22%) compared to other days. Application of age-corrected biomarker cutoffs to the 1,316 subjects showed a stronger dependency of low urine output on age than the clinical setting, occurring in 44% of the 72 participants aged 15-30 years and 18% of the 62 patients aged 90-104 years.

CONCLUSION

Biomarkers measured in morning urine of young and middle-aged volunteers indicated urine output of < 1 L with good precision, but the cutoffs should be validated in older age groups to yield reliable results.

TRIAL REGISTRATIONS

ISRCTN12215472 at http://www.isrctn.com ; NCT01458678 at ClinicalTrials.gov, and ChiCTR-TNRC-14,004,479 at the chictr.org/en.

Origins of thirstiness sensation and current food solutions

The sensation of thirstiness is the desire to drink water. In certain situations, the ingestion of liquid water can be restricted. As a result, thirstiness is not relieved, resulting in an uncomfortable and distressing situation. The present review describes thirstiness and hydration, the food products and beverages that cause thirstiness, and the beverages and food products currently available to quench thirstiness in individuals with restricted access to liquid ingestion. It also discusses how to measure the effectiveness of calming thirstiness. To diminish thirstiness distress, different alternatives to liquids are proposed. Individuals with swallowing disorders are given thickened water, individuals with restricted water ingestion are given ice cubes or ice popsicles of different flavors, and sportspeople are given energy gels. However, current beverage solutions seem not to relieve thirst fully, although some stimuli like iced water, flavors (especially lemon and mint), or acids seem to work better than plain stimuli and could be added to existing products. Therefore, there is still a need to incorporate these strategies into beverage and food formulations and to test their effectiveness.

The Importance of Optimal Hydration in Patients with Heart Failure-Not Always Too Much Fluid

Heart failure (HF) is a leading cause of morbidity and mortality and a major public health problem. Both overhydration and dehydration are non-physiological states of the body that can adversely affect human health. Congestion and residual congestion are common in patients hospitalized for HF and are associated with poor prognosis and high rates of rehospitalization. However, the clinical problem of dehydration is also prevalent in healthcare and community settings and is associated with increased morbidity and mortality. This article provides a comprehensive review of the issue of congestion and dehydration in HF, including HF guidelines, possible causes of dehydration in HF, confirmed and potential new diagnostic methods. In particular, a full database search on the relationship between dehydration and HF was performed and all available evidence in the literature was reviewed. The novel hypothesis of chronic subclinical hypohydration as a modifiable risk factor for HF is also discussed. It is concluded that maintaining euvolemia is the cornerstone of HF management. Physicians have to find a balance between decongestion therapy and the risk of dehydration.

Thirst in heart failure: A scoping review

AIM

The aim of this study was to summarise the overall picture of thirst-related research in patients with heart failure.

DESIGN

We conducted a scoping review following the Arskey and O'Malley methodological framework along with the PAGER framework.

METHODS

PubMed, CINAHL, Web of Science, Embase, The Cochrane Library, Jonna Briggs Institute, ProQuest Database, Google Scholar, PsycINFO, PQDT, CNKI, Wan Fang, VIP and CBM. Additionally, grey literature including grey databases (Opengrey, OpenDoar, Openaire and BASEL Bielefeld Academic Search Engine), conferences or articles (Scopus and Microsoft Academic), graduate theses databases (eTHOS, DART Europe, Worldcat and EBSCO Open Dissertations) and government information media (UK guidance and regulations, USA government websites, EU Bookshop and UN official publications) were searched. The databases were searched from inception to 18 August 2022 for Articles written in English and Chinese. Two researchers independently screened articles based on inclusion and exclusion criteria, and a third researcher adjudicated disagreements.

RESULTS

We retrieved 825 articles, of which 26 were included. Three themes were summarised from these articles: (a) the incidence of thirst in patients with heart failure; (b) the thirst-related factors in patients with heart failure; and (c) the intervention measures of thirst in patients with heart failure.

Association Between Self-care and Resilience: A Cross-sectional Study in Heart Failure Patients

BACKGROUND

Self-care (SC) is a cornerstone in heart failure management and is related to patient outcomes. The continuous and complex demands of SC can be experienced as stressful and may require patients to apply resilient behaviors as they manage their conditions. Resilience may be a helpful factor in performing SC.

OBJECTIVE

The aim of this study was to determine the association between resilience and SC in patients with heart failure.

METHODS

A cross-sectional study was performed between January 2020 and January 2021. Participants were asked to complete a questionnaire addressing baseline characteristics, the 2-item Patient Health Questionnaire, the Resilience Evaluation Scale, and the Self-Care of Chronic Illness Inventory, which measures 3 concepts of SC: SC maintenance, SC monitoring, and SC management. Multiple regression analysis was performed to determine whether resilience was associated with SC.

RESULTS

Eighty-six patients were included, and 74 patients completed the questionnaire. In the univariate analysis, an association was found between resilience and SC maintenance, resulting in an increase in SC for patients with higher resilience (β = 0.24; 95% confidence interval, 0.03-0.96). In the multivariate analysis adjusted and corrected for confounders, no significant associations between resilience and all SC scales were found.

CONCLUSION

This study could not demonstrate significant associations between resilience and all SC scales. This study contributes to the body of knowledge on factors that can mediate or moderate SC. Further longitudinal research should be performed to study cause-effect relationships.

Prevalence of and risk factors for thirst in the intensive care unit: An observational study

AIM AND OBJECTIVES

This study investigated the incidence of thirst and contributing factors in intensive care unit (ICU) patients by analysing differences in physiologic, psychological, and disease- and environment-related parameters in ICU patients with vs without thirst.

BACKGROUND

Little is known about the factors that influence thirst, and there are no standardised methods for identifying at-risk patients in the ICU. Previous studies generalised the risk of thirst in ICU patients because of a lack of data on relevant variables. Here, we examined the factors contributing to thirst based on symptom management theory.

DESIGN

Prospective descriptive design.

METHODS

Physiologic, psychological, disease-related and environment-related data were collected for 301 patients from 4 ICUs (medical, surgical, cardiac and emergency ICUs) of a hospital from 15 December 2017-10 July 2019 through a screening interview, questionnaires and from electronic medical records. The data were analysed with descriptive statistics, the t-test and chi-squared test, and by logistic regression. Binary stepwise logistic regression was used to identify thirst-associated factors. The findings are reported according to the STROBE checklist for cross-sectional studies.

RESULTS

In total, 210/301 (69.8%) ICU patients experienced thirst. Risk factors were nil per os order (odds ratio [OR] = 4.10, 95% confidence interval [CI]: 1.44-11.69), surgery (OR = 2.96, 95% CI: 1.11-7.93), high glucose (OR = 3.36, 95% CI: 1.01-11.17) and greater disease severity (OR = 1.13, 95% CI: 1.02-1.24).

CONCLUSION

Thirst is common in ICU patients. Timely detection of patients' thirst and identification of those at high risk by ICU nurses can ensure the implementation of effective and safe interventions.

RELEVANCE TO CLINICAL PRACTICE

The results of this study highlight the need to evaluate thirst symptoms in patients with severe disease and develop relief strategies for fasting, perioperative, and hyperglycaemic patients and others who are at high risk of thirst.

Translation and Psychometric Evaluation of the German Version of the Thirst Distress Scale for Patients With Heart Failure

BACKGROUND

In patients with chronic heart failure, thirst can be perceived as an intensive and burdensome symptom, which may have a negative impact on patients' quality of life. To initiate thirst-relieving interventions, assessment of thirst and its related distress is essential. At the time of this study, no instrument was available to evaluate thirst distress in patients with heart failure in Germany.

OBJECTIVE

The aims of this study were to translate the "Thirst Distress Scale for patients with Heart Failure" (TDS-HF) from English into German and to test validity and reliability of the scale.

METHODS

The English version of the TDS-HF was translated into German. A linguistically and culturally sensitive forward-and-backward translation was performed. Psychometric evaluation included confirmatory factor analysis, reliability in terms of internal consistency, and concurrent validity.

RESULTS

Eighty-four hospitalized patients (mean age, 72 ± 10 years; 29% female; mean left ventricular ejection fraction, 36% ± 12%; 62% New York Heart Association functional classes III-IV, 45% on fluid restriction) from an acute care hospital were involved in the study. The item-total correlation ranged from 0.58 to 0.78. Interitem correlations varied between 0.37 and 0.79. Internal consistency was high, with a Cronbach α of 0.89. There was a high correlation between the total score of the TDS-HF and the visual analog scale to assess thirst intensity ( r = 0.72, P ≤ .001), and a low correlation with fluid restriction ( r = 0.35, P = .002).

CONCLUSIONS

The evaluation of the German TDS-HF showed satisfactory psychometric properties in this sample. The instrument is usable for further research and additional psychometric testing.

Thirst in stable heart failure patients; time to reconsider fluid restriction and prescribed diuretics

Aims

One of the bothersome symptoms that heart failure (HF) patients can experience is thirst. There are limited data on the association between thirst and fluid intake and clinical variables. Therefore, the aim of this study was to describe severe thirst in stable HF patients and assess factors related to severe thirst, including actual fluid intake and sodium intake.

Methods and results

The study had a cross‐sectional design. Stable HF patients from two HF clinics in the Netherlands were included and assessed thirst by a visual analogue scale ranging from 0 to 100. They also completed questionnaires on thirst distress, self‐care behaviour, and HF symptoms. A 3 day food diary was completed to assess actual fluid intake and sodium intake. Finally, patients collected urine for 24 h. Patients were divided into severe and low thirst based on thirst score and thirst distress. T‐tests, Mann–Whitney tests, and χ² tests were conducted to assess differences between both groups. Multivariable logistic regression analysis was performed to assess factors associated with severe thirst. A total of 100 patients were included (40% female, mean age 72 ± 12) of which 68 completed the food diary. The mean thirst score was 28 ± 25, and 25% experienced severe thirst. The majority of patients (94%) were prescribed a fluid restriction, 37% had a restriction between 1500 and 2000 mL, and 32% a restriction of 1500 mL. Severe thirst in the total group with 100 patients was associated with a higher dose of loop diuretics [odds ratio (OR) 3.25; 95% confidence interval (CI) 1.01–10.45; P = 0.048] and a higher urine output over 24 h (OR 1.002; 95% CI 1.00–1.003; P = 0.010). In the group of patients who completed the food diary (N = 68), severe thirst was associated with a higher sodium intake (OR 1.002; 95% CI 1.001–1.003; P = 0.003), a higher dose of loop diuretics (OR 22.69; 95% CI 2.78–185.04; P = 0.004), and more fatigue (OR 11.2; 95% CI 1.54–82.12; P = 0.017).

Conclusions

A quarter of all stable HF patients experienced severe thirst. A higher dose of loop diuretics was associated with more thirst; therefore, it might be important to review the dose of loop diuretics critically and try to decrease it in order to relieve severe thirst. Because all patients were prescribed a fluid restriction, a reconsideration of this restriction is also suggested.

Thirst distress in outpatients with heart failure in a Mediterranean zone of Spain

Aims

This study aimed to evaluate psychometric properties of the Spanish version of the Thirst Distress Scale for patients with Heart Failure (TDS‐HF) and to describe thirst distress‐associated factors in outpatients at a heart failure (HF) clinic in Spain. Thirst is common in patients with HF, but thirst distress has rarely been addressed and may significantly decrease quality of life.

Methods and results

A cross‐sectional study was performed assessing perceived thirst distress by patients with HF during the preceding 3 days, with the TDS‐HF (scores 8 to 40). Univariable and multivariable linear regression analyses were performed to identify variables independently associated with thirst distress. Three‐hundred two HF outpatients were included (age 67 ± 12 years, 74% male, HF duration 82 ± 75 months, left ventricular ejection fraction 42 ± 14%). Most patients were on treatment with fluid restriction (99%), sodium restriction (99%), and diuretics (70%). The psychometric evaluation of the Spanish version of the TDS‐HF showed satisfactory item‐total and inter‐item correlations (range from 0.77 to 0.85 and 0.60 to 0.84, respectively), and internal consistency was 0.95 (Cronbach's alpha). The majority perceived mild to moderate thirst distress, and 18% perceived it as high or severe. The mean score obtained was 16.2 ± 9.3 (median 13, Q1–Q3 8–20). Higher serum urea {beta coefficient 1.6 [95% confidence interval (CI) 0.267 to 2.92], P = 0.019} and lower potassium [beta coefficient −3.63 (85% CI −6.32 to −0.93), P = 0.009] remained significantly associated with thirst distress in the multivariable analysis, together with the dose of diuretics [beta coefficient 2.98 (95% CI 1.37 to 4.59), P < 0.001]. Treatment with angiotensin receptor blocker showed an independent protective effect [beta coefficient −3.62 (95% CI −6.89 to −0.345), P = 0.03].

Conclusions

The psychometric evaluation of the Spanish version of the TDS‐HF showed good psychometric properties. One in five patients experienced severe distress by thirst, but the majority had mild to moderate thirst distress. The dose of diuretics and angiotensin receptor blocker treatment influence thirst distress and could be clinically important targets to relieve thirst distress in patients with HF.

A RandomisEd ControLled TrIal of ChEwing Gum to RelieVE Thirst in Chronic Heart Failure (RELIEVE-CHF)

BACKGROUND

Thirst is a common and troublesome symptom of patients with chronic heart failure (CHF). To date, there are no interventions to help alleviate thirst in this cohort. Chewing gum is a novel intervention, which has been tested in people undergoing haemodialysis, also prescribed with a fluid restricted therapy. The aim of this study was to determine the effect of chewing gum on the level of thirst in the short-term (average of 24 hours each day for 4 days) and in the longer-term (Days 7, 14 and 28) individuals with CHF.

METHODS

Seventy-one (71) individuals with CHF on oral loop diuretics were randomised to chewing gum (n=36) or control (n=35) for 2 weeks. Both groups were assessed for their level of thirst at Days 1-4, 7, 14 and 28.

RESULTS

Significant improvements in the level of thirst of those who received chewing gum compared to the control group at Day 4 (p=0.04) and Day 14 (p=0.02) were observed.

CONCLUSION

Chewing gum provided relief from thirst in the short-term and in the longer term. This trial provides important information to inform future clinical trials on ways to relieve thirst.

Association between nocturia and frailty among elderly males in a veterans administration population

BACKGROUND

The relationship between frailty and nocturnal voiding is poorly understood.

AIM

To characterize the association between frailty, as defined by a frailty index (FI) based upon the Canadian Study of Health and Aging (CSHA) criteria, and nocturia, defined by measures of nocturnal urine production.

METHODS

Real-world retrospective analysis of voiding diaries from elderly males with lower urinary tract symptoms (LUTS) at an outpatient urology clinic. Males ≥ 65 years with ≥ 2 nocturnal voids were included. A modified FI was calculated from the LUTS database, which captured 39 variables from the original CSHA FI. Patients were divided into 3 groups by modified FI: low (≤ 0.077) (n = 59), intermediate (> 0.077 and < 0.179) (n = 58), and high (≥ 0.179) (n = 41). Diary parameters were compared using the Kruskal-Wallis test and pairwise comparisons with the Wilcoxon rank-sum test and Bonferroni adjustment.

RESULTS

The high frailty group was characterized by higher nocturnal urine volume (NUV), maximum voided volume (MVV), nocturnal maximum voided volume (NMVV), and nocturnal urine production (NUP). The presence of comorbid diabetes mellitus did not explain this effect.

CONCLUSION

Elderly males seeking treatment for LUTS with a high frailty burden are disproportionately affected by excess nocturnal urine production. Future research on the mechanistic relationship between urine production and functional impairment is warranted.

Thirst and factors associated with frequent thirst in patients with heart failure in Spain

BACKGROUND

Thirst is a troublesome symptom in patients with Heart Failure (HF) and one that might be perceived differently in different countries depending on climate, food and cultural habits. The aims of the study were to describe thirst frequency, duration and intensity and to identify factors associated with frequent thirst in outpatients with HF in a Mediterranean country.

METHODS

Data was collected in a cross-sectional study involving 302 patients diagnosed with HF (age 67±12 years, 74% male, LVEF 43%±14) in Spain on thirst frequency and duration, and thirst intensity by patient self-report (VAS, 0-100 mm). Clinical variables were collected from the medical files. Regression analysis was used to identify factors independently associated with frequent thirst.

RESULTS

Of all the patients, 143 (47%) were frequently thirsty, and their median (25^th and 75^th percentiles) thirst intensity was higher (VAS 50 mm [20-67] vs 7 [0-20], p<.001). Their thirst lasted longer compared to those who never/sometimes were thirsty (p<.001). Less treatment with angiotensin receptor blockers (Odds Ratio [OR] 2.72; 95% Confidence Interval [CI] 1.33-5.58), diuretics >40 mg/day (OR 1.92; 95% CI 1.02-3.64), depression (OR 2.99; CI 1.17-7.62), male gender (OR 1.98; CI 1.08-3.64) and worse New York Heart Association functional class (OR 1.92; 95% CI 1.05-3.52) were independently associated with frequent thirst.

CONCLUSIONS

About half of patients with HF and fluid restriction experienced frequent thirst in a Mediterranean area of Spain, and their thirst duration and intensity were significantly increased. Frequent thirst was associated with demographic, clinical and therapeutic variables. The results may help to identify patients with a higher risk of frequent thirst and might suggest therapeutic changes in order to diminish this troublesome symptom.

Signs of Dehydration after Hip Fracture Surgery: An Observational Descriptive Study

Background and Objectives: Dehydration might be an issue after hip fracture surgery, but the optimal tools to identify the dehydrated condition have not been determined. The aim of the present study was to compare the characteristics of elderly postoperative patients who were classified as dehydrated according to the methods used in the clinic. Materials and Methods: Thirty-eight patients aged between 65 and 97 (mean, 82) years were studied after being admitted to a geriatric department for rehabilitation after hip fracture surgery. Each patient underwent blood analyses, urine sampling, and clinical examinations. Results: Patients ingested a mean of 1,008 mL (standard deviation, 309 mL) of fluid during their first day at the clinic. Serum osmolality increased significantly with the plasma concentrations of sodium, creatinine, and urea. Seven patients had high serum osmolality (≥300 mosmol/kg) that correlated with the presence of tongue furrows (p < 0.04), poor skin turgor (p < 0.03), and pronounced albuminuria (p < 0.03). Eight patients had concentrated urine (urine-specific gravity ≥ 1.025) that correlated with a low intake of liquid and with a decrease in body weight during the past month of −3.0 kg (25–75 th percentiles, −5.1 to −0.9) versus +0.2 (−1.9 to +2.7) kg (p < 0.04). Conclusions: Renal fluid conservation of water, either in the form of hyperosmolality or concentrated urine, was found in 40% of the patients after hip fracture surgery. Hyperosmolality might not indicate a more severe fluid deficit than is indicated by concentrated urine but suggests an impaired ability to concentrate the urine.

Thirst-guided participant-controlled intravenous fluid rehydration: a single blind, randomised crossover study

BACKGROUND

Dehydration is common in hospitals and is associated with increased mortality and morbidity. Clinical assessment and diagnostic measures of dehydration are unreliable. We sought to investigate the novel concept that individuals might control their own intravenous rehydration, guided by thirst.

METHODS

We performed a single-blind, counterbalanced, randomised cross-over trial. Ten healthy male volunteers of mean age 26 (standard deviation [sd] 10.5) yr were dehydrated by 3-5% of their baseline body mass via exercising in the heat (35°C, 60% humidity). This was followed by a 4 h participant-controlled intravenous rehydration: individuals triggered up to six fluid boluses (4% dextrose in 0.18% sodium chloride) per hour in response to thirst. Participants undertook two blinded rehydration protocols which differed only by bolus volume: 50 ml (low volume [LV]) or 200 ml (high volume [HV]). Each hour during the rehydration phase, plasma osmolality (pOsm) was measured and thirst score recorded. Nude body mass was measured at baseline, after dehydration, and after the rehydration phase.

RESULTS

In both conditions, the mean dehydration-related body mass loss was 3.9%. Thirst score was strongly associated with pOsm (within-subject r=0.74) and demand for fluid decreased as pOsm corrected. In the HV condition, participants rapidly rehydrated themselves (mean fluid delivered 3060 vs 981 ml in the LV condition) to body mass and pOsm no different to their euhydrated state.

CONCLUSION

Healthy individuals appear able to rely on thirst to manage intravenous fluid intake. Future work must now focus on whether patient-controlled intravenous fluids could represent a paradigm shift in the management of hydration in the clinical setting.

CLINICAL TRIAL REGISTRATION

NCT03932890.

Thirst in patients on chronic hemodialysis: What do we know so far?

Thirst has been defined as "the sensation that leads animal's and human's actions toward the goal of finding and drinking water" or as "any drive that can motivate water intake, regardless of cause". Thirst, together with xerostomia, is the main cause of poor adherence to fluid restriction and of excessive intake of fluids in patients on chronic hemodialysis, and consequently of high interdialytic weight gain. Interdialytic weight gain (IDWG) should be lower than 4.0-4.5% of dry weight. Unfortunately, many patients have an IDWG greater than this value and some have IDWG of 10-20%. High IDWG is associated with a higher risk of all-cause and cardiovascular death and increased morbidity, such as ventricular hypertrophy and major adverse cardiac and cerebrovascular events. In addition, high IDWG leads to supplementary weekly dialysis sessions with consequent deterioration of quality of life and increased costs. Thus, the knowledge of thirst in patients on chronic hemodialysis is essential to prompt its adequate management to limit IDWG in the routine clinical practice. The present review aims to describe the physiology of thirst in patients on chronic hemodialysis, as well as the prevalence, its measures, the associated variables, the consequences, and the strategies for its reduction.

Thirst in heart failure: what do we know so far?

PURPOSE OF REVIEW

Thirst is a common and burdensome symptom of heart failure, which impacts adversely on quality of life. To date, there is limited research on the prevalence of thirst, the factors associated with thirst and interventions to help manage thirst in heart failure. This review summarizes key empirical research developments of thirst.

RECENT FINDINGS

Recent research shows that the heart failure syndrome, medications, self-care practice such as fluid restriction and anxiety contributes greatly to increased thirst in patients with heart failure. In addition, predictors such as being younger, male patient, with high symptom burden and serum urea is also associated with thirst. There are no intervention studies to manage thirst, only reports of various strategies recommended to heart failure patients in clinical practice.

SUMMARY

Despite the burden of thirst in heart failure patients, strategies to relieve thirst remains insufficiently addressed in literature. Further research to improve the understanding of the severity of thirst and its relationship to possible factors associated with thirst is required in order to develop future interventions to either prevent or alleviate troublesome thirst in patients with heart failure.

Water Intake from the Points of View of Rhazes and Avicenna

Owing to the effect of acute and chronic hypohydration on health and the lethal effects of hyperhydration, an appropriate amount of water intake is important for each individual. Traditional Iranian medicine (TIM) is a holistic system one of whose important parts deals with lifestyles and how to maintain health, including the amount of water intake for every person and the appropriate principles of drinking water. In this study, Avicenna's Canon of Medicine, Rhazes' Benefits of Food and Its Harmfulness, and conventional medical articles were reviewed to evaluate the amount of water intake for each person and the principles of drinking water. TIM has expressed an individualized difference in the amount of water intake in the form of temperament and the relationship between the appropriate time of drinking water with other daily activities. In this view, drinking water at the inappropriate time causes liver and gastrointestinal diseases; it can create the foundation for conducting new studies in the field of appropriate water intake and lifestyle changes to reduce malnutrition complications.

Signs of Dehydration in Nursing Home Residents

OBJECTIVES

Although dehydration can affect mental and physical health, there is no clear, consistent, and reproducible diagnostic tool for this condition in older people. We applied multiple methods to detect dehydration with the aim of assessing the value of using urine analysis for this purpose.

DESIGN

Nonrandomized cohort study.

SETTING AND PARTICIPANTS

Sixty nursing home residents, aged 64-103 (mean 84) years.

METHODS

Sampling of morning urine, blood analyses, and clinical examination. A previously validated algorithm summarized the urine specific gravity, osmolality, creatinine, and color to a Fluid Retention Index (FRI).

RESULTS

The cut-off for renal fluid conservation consistent with dehydration (FRI ≥ 4.0) was reached by 51% of the cohort. No statistically significant linear correlation was found between FRI and serum osmolality (mean 307.5 mOsmol/kg) or plasma sodium (mean 139 mmol/L), but the subjects reported less thirst with increasing FRI scores (linear correlation r = -0.35; P < .03). Clinical examinations of mucous membranes and tongue furrows did not correlate with other markers of dehydration. Subjects with sunken eyes had higher C-reactive protein (P < .02) and lower albumin (P < .002) concentrations in plasma than the others, while impaired skin turgor only correlated with age (P < .04).

CONCLUSIONS/IMPLICATIONS

Renal fluid conservation consistent with dehydration was found in half of the nursing home residents, which could partially be accounted for by decreased thirst. Clinical examinations probably reflected the physical status and age more than dehydration. The lack of correlation between the serum osmolality and the FRI, both of which are purported to be gold standards for dehydration, raises questions about whether a gold standard exists.

Changes in Thirst Intensity During Optimization of Heart Failure Medical Therapy by Nurses at the Outpatient Clinic

BACKGROUND

Thirst can be aggravated in patients with heart failure (HF), and optimization of HF medication can have positive impact on thirst.

OBJECTIVES

The aims of this study were to describe changes in thirst intensity and to determine factors associated with high thirst intensity during optimization of HF medication.

METHODS AND RESULTS

Patients with HF (N = 66) who were referred to an HF clinic for up-titration of HF medication were included. Data were collected during the first visit to the clinic and at the end of the treatment program. Data were dichotomized by the median visual analog scale score for thirst, dividing patients into 2 groups: low thirst intensity (0-20 mm) and high thirst intensity (>20 mm on a visual analog scale of 0-100 mm). In total, 67% of the patients reported a higher thirst intensity after the HF up-titration program. There was no difference in thirst intensity between the patients who reached target doses and those who did not. Plasma urea level (odds ratio, 1.33; 95% confidence interval, 1.07-1.65) and fluid restriction (odds ratio, 6.25; 95% confidence interval, 1.90-20.5) were independently associated with high thirst intensity in patients with HF.

CONCLUSIONS

Thirst intensity increased in two-thirds of the patients during a time period of optimization of HF medication. Fluid restriction and plasma urea levels were associated with high thirst intensity.

Trajectory of thirst intensity and distress from admission to 4-weeks follow up at home in patients with heart failure

BACKGROUND

Patients with heart failure (HF) can suffer from increased thirst intensity and distress. Trajectories of thirst intensity and distress from hospital to home are unclear. The aim of this study was to describe thirst intensity and distress trajectories in patients from the time of hospital admission to 4 weeks after discharge, and describe trajectories of thirst intensity and distress by patients' characteristics (gender, age, body mass index [BMI], plasma urea, anxiety, and depression).

PATIENTS AND METHODS

In this observational study, data were collected from patients with HF (n=30) at hospital admission, discharge, and at 2 and 4 weeks after discharge. Thirst intensity (visual analog scale, 100 mm) and distress (Thirst Distress Scale-HF, score 9-45) were used. Trajectories were examined using growth modeling.

RESULTS

Trajectory of the thirst intensity was significantly different, for patients with low and high thirst intensity levels (median cut-off 39 mm), from admission to 4 weeks follow up (thirst increased and decreased, respectively). Patients with high level of thirst distress (median score >22) at admission, having fluid restriction and women continued to have higher thirst distress over time. Patients feeling depressed had higher thirst intensity over time. There were no differences in the trajectories of thirst intensity and distress by age, BMI, plasma urea, and anxiety.

CONCLUSION

Intensity and distress of thirst, having fluid restriction, and feeling depressed at the admission were critical in predicting the trajectory of thirst intensity and distress after discharge to home in patients with HF. Effective intervention relieving thirst should be provided before their discharge to home.

Frequent drinking of small volumes improves cardiac function and survival in rats with chronic heart failure

Fluid retention is the main reason for the high hospitalization rate among patients with chronic heart failure (CHF). Given the lack of knowledge about fluid intake regulation and its consequences in patients with CHF, current guidelines do not provide clear direction for fluid management. Using a rat model of CHF, we investigated altering drinking behaviors and explored fluid management strategies. CHF was induced by ligating the left anterior descending coronary arteries in 8‐week‐old, male, Sprague‐Dawley rats. A custom‐designed drop counting and feedback control system was used to record and modulate drinking behaviors. During the first month after an induced myocardial infarction (MI), we observed that the spontaneous per drinking volume (PDV) was significantly increased in animals with prolonged intervals between drinking episodes. In addition, there was a significant inverse correlation between the early PDV and the post‐MI lifespan (r = −0.907; P < 0.001). Moreover, modulating the drinking behavior of rats with CHF to involve frequent drinking of small PDVs significantly enhanced hemodynamics and prevented cardiac remodeling, with a significant improvement in the 180‐day survival rate, compared with animals allowed to drink freely (50% vs. 36%; P < 0.01). The results of dynamic PDV changes, after MI, suggest that an impaired thirst mechanism is associated with the sensing and regulating of fluid balance in rats with CHF. These results suggest that increasing the drinking frequency, with small PDVs, may be beneficial to preventing progression of cardiac dysfunction in CHF.

Development and psychometric evaluation of the Thirst Distress Scale for patients with heart failure

BACKGROUND

Patients with heart failure can experience thirst distress. However, there is no instrument to measure this in patients with heart failure. The aim of the present study was to develop the Thirst Distress Scale for patients with Heart Failure (TDS-HF) and to evaluate psychometric properties of the scale.

METHODS AND RESULTS

The TDS-HF was developed to measure thirst distress in patients with heart failure. Face and content validity was confirmed using expert panels including patients and healthcare professionals. Data on the TDS-HF was collected from patients with heart failure at outpatient heart failure clinics and hospitals in Sweden, the Netherlands and Japan. Psychometric properties were evaluated using data from 256 heart failure patients (age 72±11 years). Concurrent validity of the scale was assessed using a thirst intensity visual analogue scale. Patients did not have any difficulties answering the questions, and time taken to answer the questions was about five minutes. Factor analysis of the scale showed one factor. After psychometric testing, one item was deleted. For the eight item TDS-HF, a single factor explained 61% of the variance and Cronbach's alpha was 0.90. The eight item TDS-HF was significantly associated with the thirst intensity score ( r=0.55, p<0.001). Regarding test-retest reliability, the intraclass correlation coefficient was 0.88, and the weighted kappa values ranged from 0.29-0.60.

CONCLUSION

The eight-item TDS-HF is valid and reliable for measuring thirst distress in patients with heart failure.

A survey of views and opinions of health professionals managing thirst in chronic heart failure

BACKGROUND

Thirst is a common and burdensome symptom of chronic heart failure (CHF) which affects adherence to self-care practices specifically fluid restriction. Despite this, there is no standard clinical practice for managing the symptom of thirst.

AIMS AND OBJECTIVES

The aim is to identify the current strategies recommended by health professionals to help relieve thirst in CHF patients and their perceived usefulness of these strategies.

METHODS

A survey was distributed to attendees of the 8th Annual Scientific Meeting of Australasian Cardiovascular Nursing College.

RESULTS

There were 42 of 70 respondents to the survey. The majority (33 of 40; 82.5%) had recommended various strategies to alleviate thirst. The most recommended strategy was ice chips (36 of 38; 94.7%). Overall, the respondents reported 'some use' in all of the strategies.

CONCLUSION

Information from this survey may help in the incorporation of thirst-relieving strategies into evidence-based guidelines; further improving the quality of care of patients.

The Effect of Psychological Intervention on Thirst and Interdialytic Weight Gain in Patients on Chronic Hemodialysis: A Randomized Controlled Trial

OBJECTIVE

Patients on hemodialysis (HD) are unable to eliminate excess fluid and must adhere to a regimen of dietary fluid restriction to prevent volume overload. Thirst represents a major obstacle to the achievement of such a goal. The aim of our study was (1) to assess the association of thirst and xerostomia, measured by validated questionnaires, Dialysis Thirst Inventory and Xerostomia Inventory with interdialytic weight gain (IDWG) and (2) to evaluate in a randomized controlled trial (RCT), the effect of psychological intervention on IDWG and thirst.

STUDY DESIGN

Cross-sectional evaluation of association of thirst and IDWG and single-blind RCT of psychological intervention on IDWG management.

SETTING

Outpatient dialysis unit.

SUBJECTS

The cross-sectional evaluation included 117 patients on HD (age, 71 ± 13 years); among these, 54 were selected for the RCT.

INTERVENTION

The questionnaires were administered to all the participating patients; IDWG (4-week average), Kt/V, predialysis blood pressure, dialyzate sodium, hematocrit, serum electrolytes, parathyroid hormone, and patients' medications were recorded. Fifty-four patients were randomized on a 1:1 basis to usual treatment (including dietary advice) or psychological intervention, consisting of group sessions, held once a week for 5 weeks; IDWG and all the other parameters were rechecked after 6 weeks and 6 months.

MAIN OUTCOME MEASURE

IDWG change from baseline.

RESULTS

Dialysis Thirst Inventory score was correlated with IDWG (ρ = 0.575; P < .001), body mass index (ρ = 0.257; P = .005), and inversely with age (ρ = -0.344; P < .001). A small but significant decrease of IDWG compared to baseline was observed in the intervention group (baseline 1332 ± 338 g/day; at 6 weeks, 1183 ± 258 g/day; at 6 months, 1203 ± 284 g/day; P < .001). No IDWG changes with respect to baseline occurred in controls (baseline 1310 ± 333 g/day; at 6 weeks, 1336 ± 340 g/day; at 6 months, 1323 ± 328 g/day; P = .57). The secondary outcomes were not affected by the intervention.

CONCLUSIONS

The findings of our study show that a psychological support may help managing IDWG in HD patients.

Clinical symptoms, signs and tests for identification of impending and current water-loss dehydration in older people

BACKGROUND

There is evidence that water-loss dehydration is common in older people and associated with many causes of morbidity and mortality. However, it is unclear what clinical symptoms, signs and tests may be used to identify early dehydration in older people, so that support can be mobilised to improve hydration before health and well-being are compromised.

OBJECTIVES

To determine the diagnostic accuracy of state (one time), minimally invasive clinical symptoms, signs and tests to be used as screening tests for detecting water-loss dehydration in older people by systematically reviewing studies that have measured a reference standard and at least one index test in people aged 65 years and over. Water-loss dehydration was defined primarily as including everyone with either impending or current water-loss dehydration (including all those with serum osmolality ≥ 295 mOsm/kg as being dehydrated).

SEARCH METHODS

Structured search strategies were developed for MEDLINE (OvidSP), EMBASE (OvidSP), CINAHL, LILACS, DARE and HTA databases (The Cochrane Library), and the International Clinical Trials Registry Platform (ICTRP). Reference lists of included studies and identified relevant reviews were checked. Authors of included studies were contacted for details of further studies.

SELECTION CRITERIA

Titles and abstracts were scanned and all potentially relevant studies obtained in full text. Inclusion of full text studies was assessed independently in duplicate, and disagreements resolved by a third author. We wrote to authors of all studies that appeared to have collected data on at least one reference standard and at least one index test, and in at least 10 people aged ≥ 65 years, even where no comparative analysis has been published, requesting original dataset so we could create 2 x 2 tables.

DATA COLLECTION AND ANALYSIS

Diagnostic accuracy of each test was assessed against the best available reference standard for water-loss dehydration (serum or plasma osmolality cut-off ≥ 295 mOsm/kg, serum osmolarity or weight change) within each study. For each index test study data were presented in forest plots of sensitivity and specificity. The primary target condition was water-loss dehydration (including either impending or current water-loss dehydration). Secondary target conditions were intended as current (> 300 mOsm/kg) and impending (295 to 300 mOsm/kg) water-loss dehydration, but restricted to current dehydration in the final review.We conducted bivariate random-effects meta-analyses (Stata/IC, StataCorp) for index tests where there were at least four studies and study datasets could be pooled to construct sensitivity and specificity summary estimates. We assigned the same approach for index tests with continuous outcome data for each of three pre-specified cut-off points investigated.Pre-set minimum sensitivity of a useful test was 60%, minimum specificity 75%. As pre-specifying three cut-offs for each continuous test may have led to missing a cut-off with useful sensitivity and specificity, we conducted post-hoc exploratory analyses to create receiver operating characteristic (ROC) curves where there appeared some possibility of a useful cut-off missed by the original three. These analyses enabled assessment of which tests may be worth assessing in further research. A further exploratory analysis assessed the value of combining the best two index tests where each had some individual predictive ability.

MAIN RESULTS

There were few published studies of the diagnostic accuracy of state (one time), minimally invasive clinical symptoms, signs or tests to be used as screening tests for detecting water-loss dehydration in older people. Therefore, to complete this review we sought, analysed and included raw datasets that included a reference standard and an index test in people aged ≥ 65 years.We included three studies with published diagnostic accuracy data and a further 21 studies provided datasets that we analysed. We assessed 67 tests (at three cut-offs for each continuous outcome) for diagnostic accuracy of water-loss dehydration (primary target condition) and of current dehydration (secondary target condition).Only three tests showed any ability to diagnose water-loss dehydration (including both impending and current water-loss dehydration) as stand-alone tests: expressing fatigue (sensitivity 0.71 (95% CI 0.29 to 0.96), specificity 0.75 (95% CI 0.63 to 0.85), in one study with 71 participants, but two additional studies had lower sensitivity); missing drinks between meals (sensitivity 1.00 (95% CI 0.59 to 1.00), specificity 0.77 (95% CI 0.64 to 0.86), in one study with 71 participants) and BIA resistance at 50 kHz (sensitivities 1.00 (95% CI 0.48 to 1.00) and 0.71 (95% CI 0.44 to 0.90) and specificities of 1.00 (95% CI 0.69 to 1.00) and 0.80 (95% CI 0.28 to 0.99) in 15 and 22 people respectively for two studies, but with sensitivities of 0.54 (95% CI 0.25 to 0.81) and 0.69 (95% CI 0.56 to 0.79) and specificities of 0.50 (95% CI 0.16 to 0.84) and 0.19 (95% CI 0.17 to 0.21) in 21 and 1947 people respectively in two other studies). In post-hoc ROC plots drinks intake, urine osmolality and axillial moisture also showed limited diagnostic accuracy. No test was consistently useful in more than one study.Combining two tests so that an individual both missed some drinks between meals and expressed fatigue was sensitive at 0.71 (95% CI 0.29 to 0.96) and specific at 0.92 (95% CI 0.83 to 0.97).There was sufficient evidence to suggest that several stand-alone tests often used to assess dehydration in older people (including fluid intake, urine specific gravity, urine colour, urine volume, heart rate, dry mouth, feeling thirsty and BIA assessment of intracellular water or extracellular water) are not useful, and should not be relied on individually as ways of assessing presence or absence of dehydration in older people.No tests were found consistently useful in diagnosing current water-loss dehydration.

AUTHORS' CONCLUSIONS

There is limited evidence of the diagnostic utility of any individual clinical symptom, sign or test or combination of tests to indicate water-loss dehydration in older people. Individual tests should not be used in this population to indicate dehydration; they miss a high proportion of people with dehydration, and wrongly label those who are adequately hydrated.Promising tests identified by this review need to be further assessed, as do new methods in development. Combining several tests may improve diagnostic accuracy.

Predictors of thirst in intensive care unit patients

CONTEXT

Thirst is a pervasive, intense, and distressing symptom in intensive care unit (ICU) patients. Although thirst may be avoided and/or treated, scant data are available to help providers identify patients most in need.

OBJECTIVES

This study was designed to identify predictors of the presence, intensity, and distress of thirst in ICU patients.

METHODS

This descriptive cross-sectional study enrolled 353 patients from three ICUs (medical-surgical, cardiac, and neurological). To measure outcomes, patients were asked to report the presence of thirst (yes/no) and, if present, to rate its intensity and distress on zero to 10 numeric rating scales (10=worst). Predictor variables were demographic (e.g., age), treatment-related (e.g., opioids), and biological (e.g., total body water). Data were analyzed with logistic regression and truncated regression with alpha preset at 0.05.

RESULTS

Thirst presence was predicted by high opioid doses (≥ 50 mg), high furosemide doses (>60 mg), selective serotonin reuptake inhibitors, and low ionized calcium. Thirst intensity was predicted by patients not receiving oral fluid and having a gastrointestinal (GI) diagnosis. Thirst distress was predicted by mechanical ventilation, negative fluid balance, antihypertensive medications, and a GI or "other" diagnosis.

CONCLUSION

Thirst presence was predicted by selected medications (e.g., opioids). Thirst intensity and/or thirst distress were predicted by other treatments (e.g., mechanical ventilation) and medical diagnoses (e.g., GI). This is one of the first studies describing predictors of the multidimensional characteristics of thirst. Clinicians can use these data to target ICU patients whose thirst might warrant treatment.

Thirst in chronic heart failure: a review

AIMS AND OBJECTIVES

This review will (1) explore factors related to thirst in chronic heart failure and (2) describe interventions to alleviate thirst in chronic heart failure patients.

BACKGROUND

Thirst is a common and troublesome symptom of chronic heart failure. Despite the burden and prevalence of this symptom, there are limited strategies to assist in its management.

DESIGN

This is a review of literature on the burden of thirst, contributors to thirst and potential management strategies of thirst in patients with chronic heart failure.

METHODS

Medline, Cumulative Index for Nursing and Allied Health, PubMed and Scopus were searched using the key words thirst, chronic heart failure, angiotensin II, fluid restriction and intervention. Of the 165 citations yielded, nine studies (n = 9) were included. The eligibility criteria included participants with confirmed diagnosis of chronic heart failure, randomised controlled studies or any studies with thirst as primary or secondary outcome, in humans and in English. There was no limit to the years searched.

RESULTS

Factors related to thirst in chronic heart failure were condition; prolonged neurohormonal activation, treatment; pharmacological interventions and fluid restriction and emotion. No intervention studies were found in chronic heart failure patients. Interventions such as artificial saliva and chewing gum have been investigated for their effectiveness as a thirst reliever in haemodialysis patients.

CONCLUSION

Thirst is a frequent and troublesome symptom for individuals with chronic heart failure. It is highly likely that this contributes to poor adherence with fluid restrictions. Chewing gum can help alleviate thirst, but investigation in people with heart failure is needed.

RELEVANCE TO CLINICAL PRACTICE

Increasing awareness of thirst and interventions to relieve it in clinical practice is likely to improve the quality of care for people with chronic heart failure.

Osmotic homeostasis

Alterations in water homeostasis can disturb cell size and function. Although most cells can internally regulate cell volume in response to osmolar stress, neurons are particularly at risk given a combination of complex cell function and space restriction within the calvarium. Thus, regulating water balance is fundamental to survival. Through specialized neuronal "osmoreceptors" that sense changes in plasma osmolality, vasopressin release and thirst are titrated in order to achieve water balance. Fine-tuning of water absorption occurs along the collecting duct, and depends on unique structural modifications of renal tubular epithelium that confer a wide range of water permeability. In this article, we review the mechanisms that ensure water homeostasis as well as the fundamentals of disorders of water balance.

Thirst trajectory and factors associated with persistent thirst in patients with heart failure

BACKGROUND

Thirst is often increased in patients with heart failure (HF) and can cause distress during the course of the condition. The aim of the present study was to describe the trajectory of thirst during an 18-month period and to identify variables associated with persistent thirst in patients with HF.

METHODS AND RESULTS

Data were collected from 649 patients with HF with the use of the Revised Heart Failure Compliance Scale at 1, 6, 12, and 18 months after a period of hospital treatment for worsening HF. Thirst trajectory was described for the 4 follow-up visits and logistic regression analysis was used to identify factors independently associated with persistent thirst. In total, 33% (n = 212) of the patients reported thirst on ≥1 occasions and 34% (n = 46) continued to have thirst at every follow-up visit. Nineteen percent (n = 121) of the patients had persistent thirst. Patients with persistent thirst were more often younger and male and had more HF symptoms. Higher body mass index and serum urea also increased the risk of persistent thirst.

CONCLUSIONS

Patients with HF who were thirsty at the 1-month follow-up were more often also thirsty at subsequent visits. Assessment of thirst is warranted in clinical practice because one-fifth of patients suffer from persistent thirst.

B-type natriuretic peptide and severity of cognitive disorder

BACKGROUND

Natriuretic peptides have been linked to cognitive disorder in previous studies. The aim of this study was to examine the association between the severity of cognitive disorder and the levels of B-type natriuretic peptide (BNP) in an older general population.

MATERIAL AND METHODS

This study is a part of the larger population-based, multidisciplinary Kuopio 75+ health study. A total of 601 subjects aged 75 or older participated in the study. A subgroup of 126 individuals was diagnosed with cognitive disorder, and the severity of the disease was assessed. The participants were tested for BNP. Analysis of covariance was carried out to study the relationship between BNP and the stage of cognitive disorder.

RESULTS

The association between the level of cognitive disorder and BNP resembled an inverse U-shaped curve, with higher levels of BNP observed among participants with mild cognitive disorder when compared to cognitively intact participants or counterparts with more severe cognitive disorder. This effect remained after adjustment for age (P = 0.02). However, association between BNP and level of cognitive disorder was lost in further adjustment with covariates connected to the levels of BNP.

CONCLUSION

The previously reported elevation of natriuretic peptides among individuals with diagnosed cognitive disorder was found only in people with milder stages of the disorder.

Quench the thirst: lessons from clinical thirst trials

Thirst, as a symptom, has long been considered the most prevalent clinical complaint patients voice in healthcare settings. Yet, rarely have researchers examined thirst by its correlation with physiologic factors. This review was undertaken to examine the relationships between thirst ratings and factors mediating its primary physiologic correlates: plasma osmolality (pOsm) and arginine vasopressin peptide (AVP). A literature search was undertaken to identify clinical studies in human subjects that investigated the relationship of thirst to specific physiologic thirst-related correlates and associated thirst mediators. Thirst was induced in 17 selected clinical studies by hyperosmolar infusion, through water deprivation or exercise weight-loss regimens. Positive linear relationships between the subjects' thirst ratings and rising serum pOsm levels confirmed the presence of intact osmotic thirst drives. However, there were significant variations in normal compensatory rises in AVP levels that followed the rises in plasma osmolality after the subjects were exposed to cold, physical pre-conditioning and water immersion tests. Notably, older adults in the studies reported diminished thirst ratings. Weak correlations suggest that angiotensin II may play only a minor role in thirst mediation. Atrial natriuretic hormone's inhibitory effect on thirst was inconsistent. Findings indicated that older adults are at higher risk for profound dehydration due to sensory deficits along with failure to correct volume losses. The thirst trials results support the close correlation between serum pOsm values and patients' thirst ratings, with the exception of the older adult.

Thirst response to acute hypovolaemia in healthy women and women prone to vasovagal syncope

The present study measured self-perceived thirst and plasma angiotensin II (ATII) concentrations during graded hypovolaemic stress, induced by lower body negative pressure (LBNP), to elucidate the dependence of thirst on haemodynamics. A total of 24 women aged between 20 and 36 (mean age, 23) years rated their thirst on a visual analogue scale, graded from 0 to 100, when LBNP of 20, 30 and 40 mmHg was applied. Half of the women had a history of vasovagal syncope (VVS). The results showed that the thirst score increased three-fold when LBNP was applied, from 11 (median; 25th-75th percentiles, 9-25) to 34 (27-53; P<0.001). The women in the VVS group had twice as great an increase as those without a history of VVS (P<0.02). The plasma ATII concentration increased significantly in response to LBNP, both in the VVS group and in the control group, but the changes did not correlate with thirst. Application of LBNP decreased systolic and mean arterial pressures, cardiac output and pulse pressure (P<0.001 for all), but thirst correlated only with increase in heart rate and, independently, with reduction of mean arterial pressure. In conclusion, thirst and ATII increase in response to hypovolaemic stress, but are not statistically related. The haemodynamic parameter that was most strongly related to thirst was tachycardia.

Thirst and hydration status in everyday life

Water is an essential nutrient for all persons; thus, maintaining a chronic state of optimal hydration is recognized to provide health benefits. Fluid balance is maintained via thirst, a feedback-controlled variable, regulated acutely by central and peripheral mechanisms. However, voluntary drinking is also a behavior influenced by numerous social and psychological cues. Therefore, whether "thirst-guided" drinking maintains optimal hydration status is a multifactorial issue. Thirst perception is typically assessed by subjective ratings using either categorical or visual analog scales; however, which instrument yields greater sensitivity to change in hydration status has not been examined. Ratings of thirst perception do not always yield predictable patterns of voluntary drinking following dehydration; therefore, perceived thirst and ad libitum drinking are not equivalent measures of human thirst. The recommendation "drink to thirst" is frequently given to healthy individuals during daily life. However, factors and conditions (e.g., age, disease) that influence thirst should be recognized and probed further.

Effects of tap water, electrolyte solution, and spontaneous and furosemide-stimulated urinary excretion on thirst

AIM: To contrast the effects of various modifications of body fluid volumes on thirst as reported by healthy volunteers.

METHODS: Ten male volunteers aged between 19 and 37 years (mean 22 years) underwent four experiments each, which comprised infusion of 400-800 mL of acetated Ringer’s solution and intake of 600 mL of tap water. Half of the experiments were preceded by volume depletion (median 1.7 L) with furosemide. A visual analogue scale (0-100 mm) was used to assess perceived thirst during each experiment.

RESULTS: Volume depletion (P < 0.001) and tap water (P < 0.03) both affected thirst by 13 mm per L of fluid, whereas spontaneous diuresis and infusion of Ringer’s acetate did not significantly change the thirst rating (multiple regressions). More detailed analyses showed that the volume depletion increased the median (25th-75th percentiles) thirst rating from 28 mm (21-43) to 59 mm (46-72, P < 0.001) while no change occurred in those who were only slightly thirsty (< 30 mm) before the volume depletion began. Ringer’s solution alleviated thirst in those who were very thirsty, but tended to increase thirst in the volunteers who were not thirsty before the infusion. Similarly, hydration with tap water decreased thirst (by 24 mm, P < 0.04) in those who were thirsty (> 60 mm) while the others reported no change.

CONCLUSION: The change in thirst rating during volume depletion, administration of Ringer’s acetate, and ingestion of tap water were all dependent on the thirst rating obtained when the manipulation of the body fluid volume was initiated.