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PubMed1995

Dehydration stimulates hypothalamic gene expression of histamine synthesis enzyme: importance for neuroendocrine regulation of vasopressin and oxytocin secretion.

Dehydration associated with hyperosmolality and decreased extracellular volume stimulates arginine vasopressin (AVP) and oxytocin (OT) secretion from magnocellular neurons of the hypothalamus. The effects of hyperosmolality and decreased extracellular volume on the magnocellular neurons are mainly indirect and seem to be mediated centrally via several neurotransmitters and neuropeptides. Because histamine (HA), which serves as a central neurotransmitter, releases AVP and OT from the neurohypophysis when administered centrally, we investigated the possible role of HA in dehydration-induced AVP and OT secretion. To do this, we studied 1) the effect of dehydration on messenger RNA (mRNA) expression of the HA synthesis enzyme, histidine decarboxylase (HDC), in the tuberomammillary nucleus of the hypothalamus; and 2) the effect of HA synthesis inhibition during dehydration on AVP and OT mRNA expression in the supraoptic nucleus of the hypothalamus as well as on plasma AVP and OT levels. Forty-eight hours of dehydration increased the mRNA level of HDC in the tuberomammillary nuclei, whereas 24 h of dehydration had no effect. Pretreatment with the HA synthesis inhibitor alpha-fluoromethylhistidine (alpha FMH) increased the expression of HDC mRNA in 24-h dehydrated rats, but had no effect in euhydrated rats. In rats dehydrated for 48 h, the already increased level of HDC mRNA was not increased further by alpha FMH. Twenty-four and 48 h of dehydration increased AVP and OT mRNA levels in the supraoptic nucleus. This effect was inhibited by alpha FMH pretreatment. Dehydration increased the plasma levels of AVP and OT to an extent which depended on the duration of dehydration. Pretreatment with alpha FMH inhibited the hormone responses to 24 h of dehydration, but did not affect the responses to 48 h of dehydration. Twenty-four and 48 h of dehydration had no significant effect on the contents of AVP and OT in the neurohypophysis, whereas pretreatment with alpha FMH combined with 48 h of dehydration led to depletion of AVP stores in the neurohypophysis. Based on the present findings, we conclude that hypothalamic histaminergic neurons are involved in the regulation of dehydration-induced stimulation of magnocellular AVP and OT neurons.

Animals↗

PubMed2004

Intracerebroventricular administration of atrial natriuretic peptide prevents increase of plasma ADH, aldosterone and corticosterone levels in restrained conscious dehydrated rabbits.

In order to investigate the effects of centrally administered ANP on plasma ADH, aldosterone and corticosterone levels as well as on blood pressure and on heart rate, 20 male New Zealand White (NZW) rabbits were used. Measurements were made on restrained conscious animals one week after the implantation of an indwelling intracerebroventricular (icv) cannula and two indwelling intravascular catheters (intracarotid and intrajugular). Animals were classified into two main groups, those with water available ad libitum ("euhydrated" group) and those who were dehydrated for 24 h ("dehydrated" group) before blood pressure and heart rate recordings and blood sampling for hormonal determination. Each group's individuals were divided into two subgroups of five animals each. Blood samples were collected at 0 min (control) and 30, 60, 90, 120 min following icv administration of 25 microl of either artificial cerebrospinal fluid (aCSF) (subgroups "aCSF") or human (h) ANP (1 microg) in aCSF (25 microl) (subgroups "hANP"). Blood pressure and heart rate were also recorded at the same times. Plasma ADH, aldosterone and corticosterone concentrations were determined using RIA. The results were analysed by analysis of variance (ANOVA). Blood pressure and heart rate values were unaffected by water deprivation or by ANP administration. Mean plasma corticosterone levels at all times (30-120 min) were significantly higher (p<0.001) than those at 0 min time. Plasma corticosterone levels in the "dehydrated+aCSF" group were significantly higher (p<0.05) than in each of the other groups ("dehydrated+hANP", "euhydrated+aCSF", "euhydrated+hANP"). Plasma corticosterone levels in each of those other groups did not differ significantly from one another. Dehydration resulted in a tendency to increase in aldosterone levels (p<0.07), and icv administration of hANP tended (p<0.08) to prevent in the "dehydrated+hANP" experimental group the increase in aldosterone levels observed in the control "dehydrated+aCSF" group from 30 to 120 min. Dehydration resulted in an increase in ADH levels (p<0.0001), and icv administration of hANP prevented (p<0.05) in "dehydrated+hANP" experimental group the increase in ADH levels observed in the control "dehydrated+aCSF" group from 90 to 120 min. The increase of corticosterone and ADH and the tendency towards increase in aldosterone in the control dehydrated groups could possibly be due to the combined stress stimulus of dehydration and restriction in the restrain box. These results indicate that centrally administered ANP, at the concentration achieved in the present study, neither affects blood pressure and heart rate in conscious restrained euhydrated and 24 h-dehydrated NZW rabbits nor decreases the ADH, aldosterone and corticosterone response to dehydration, but does apparently modulate ADH, aldosterone and corticosterone responses to other stimuli in the dehydrated state. In conclusion, the results of this study confirm that brain ANP may have an inhibitory effect on stimulated ADH, aldosterone and corticosterone release.

Aldosterone↗

PubMed2002

Evaluation of laboratory tests in dehydrated children with acute gastroenteritis.

OBJECTIVE: The aim of the present study was to demonstrate the utility of laboratory tests in predicting dehydration severity. METHODOLOGY: We evaluated retrospectively 168 dehydrated children aged 1-21 months with acute gastroenteritis. The degree of dehydration in each patient was calculated as the percentage change in weight from admission to after rehydration. The associations between degree of dehydration, urea, bicarbonate and serum sodium were examined. RESULTS: Dehydration severity was significantly related to concentrations of urea (P < 0.00001) and bicarbonate (P = 0.01), but not to serum sodium or age. Children were divided into three groups on the basis of blood urea: (i) normal (< 6.7 mmol/L or < 40 mg/dL); (ii) intermediate (6.8-16.6 mmol/L); and (iii) high (>or=16.7 mmol/L or >or=100 mg/dL). Groups 1 and 3 had statistically significant associations with the degree of dehydration and combining the urea groups with plasma bicarbonate levels enhanced the accuracy of predictions. Group 1 had only mild to moderate dehydration, but if bicarbonate was 15 mmol/L or higher, there was a positive predictive value (PPV) of 93% for mild dehydration. Group 3 had moderate to severe dehydration, but if bicarbonate was 15 mmol/L or higher, moderate dehydration could be predicted (PPV 100%). Sixty per cent of mildly dehydrated children (32/53) had low bicarbonate, but only 7% (2/29) with bicarbonate 15 mmol/L or higher had severe dehydration. Serum sodium did not have any significant association with the degree of dehydration, or the levels of bicarbonate or urea. CONCLUSIONS: The results suggest that serum urea and bicarbonate concentrations can be helpful in the estimation of fluid deficit independently from serum sodium concentration, and may be considered to be adjuncts to clinical evaluation in assessing the degree of dehydration.

Acute Disease↗

PubMed2004

Seasonal effects of dehydration on glucose mobilization in freeze-tolerant chorus frogs (Pseudacris triseriata) and freeze-intolerant toads (Bufo woodhousii and B. cognatus).

It has been hypothesized that freeze-tolerance in anurans evolved from a predisposition for dehydration tolerance. To test this hypothesis, we dehydrated summer/fall-collected and winter acclimated freeze-tolerant chorus frogs and dehydration-tolerant, but freeze-intolerant, Woodhouse's and Great Plains toads to 25% and 50% body water loss (BWL). Following treatments, we measured glucose, glycogen, and glycogen phosphorylase and glycogen synthetase (summer/fall only) activities in liver and leg muscle. Hepatic glucose levels were not significantly altered by dehydration in either summer/fall-collected frogs or toads. Conversely, winter acclimated frogs did show an increment (2.9-fold) in hepatic glucose with dehydration, accompanied by a reduction in hepatic glycogen levels. Winter acclimated toads did not mobilize hepatic glucose in response to dehydration. Further, hepatic glycogen and phosphorylase activities did not vary in any consistent manner with dehydration in winter toads. Mean leg muscle glucose values were elevated at 50% BWL relative to other treatments, significantly so compared to 25% BWL for summer/fall-collected frogs. The pattern of hepatic glucose mobilization with dehydration in winter frogs is consistent with that in other freeze-tolerant frog species, and provides additional support for the hypothesis that freezing tolerance evolved from a capacity for dehydration tolerance. However, the lack of hepatic glucose mobilization in response to dehydration in fall frogs suggests that a seasonal component to dehydration-induced regulation of glucose metabolism exists in chorus frogs. Furthermore, the absence of a dehydration-induced mobilization of hepatic glucose at both seasons in toads suggests that this dehydration response is not universal for terrestrial anurans.

Acclimatization↗

PubMed1998

Effects of intracerebroventricular administration of atrial natriuretic peptide (ANP) on blood pressure, heart rate and plasma ADH and corticosterone levels in normal and dehydrated rabbits.

In order to investigate the effects of centrally administered Atrial Natriuretic Peptide (ANP) on plasma ADH and corticosterone levels as well as on blood pressure and on heart rate, 20 male New Zealand White (NZW) rabbits were used. Measurements were made on restrained conscious animals one week after the implantation of an indwelling intracerebroventricular (i.c.v.) cannula and two indwelling intravascular catheters (intracarotid and intrajugular). Animals were classified into two main groups, those with water available ad libitum ("euhydrated" group) and those who were dehydrated for 24h ("dehydrated" group) before blood pressure and heart rate recordings and blood sampling for hormonal determination. Each group's individuals were divided into two subgroups of five animals each. Blood samples were collected at 0 min (control) and 30; 60, 90, 120 min following i.c.v. administration of 25 microliters of either artificial cerebrospinal fluid (aCSF) (subgroups "aCSF") or human (h) ANP (1 microgram) in aCSF (25 microliters) (subgroups "hANP"). Blood pressure and heart rate were also recorded at the same times. Plasma ADH and corticosterone concentrations were determined by RIA. The results were analysed by ANOVA. Blood pressure and heart rate values were unaffected by water deprivation or by ANP administration. Mean plasma corticosterone levels at all times (30-120 min) were significantly higher (p < 0.001) than at 0 min time. Plasma corticosterone levels in the "dehydrated + aCSF" group were significantly higher (p < 0.05) than in each of the other groups ("dehydrated + hANP", "euhydrated + aCSF", "euhydrated + hANP"). Plasma corticosterone levels in each of those other groups did not differ significantly from one another. Dehydration resulted in an increase in ADH levels (p < 0.0001) and i.c.v. administration of hANP prevented (p < 0.05) in "dehydrated + hANP" experimental group, the increase in ADH levels observed in the control "dehydrated + aCSF" group from 90 to 120 min. The increase of corticosterone and ADH in the control dehydrated groups could possibly be due to the combined stress stimulus of dehydration and restriction in the restrain box. These results indicate that centrally administered ANP, at the concentration achieved in the present study, neither affects blood pressure and heart rate in conscious restrained euhydrated and 24h-dehydrated NZW rabbits nor decreases the ADH and corticosterone response to dehydration, but does apparently modulate ADH and corticosterone responses to other stimuli in the dehydrated state. In conclusion, the results of this study confirm that brain ANP may have an inhibitory effect on stimulated ADH and corticosterone release.

Animals↗

PubMedDate not supplied

Clinical indicators of dehydration severity in elderly patients.

STUDY OBJECTIVE: To determine which of the signs and symptoms of dehydration obtainable from patient history and physical examination in the emergency department are most useful in assessing the severity of dehydration in elderly patients. DESIGN: Prospective, correlational study. SETTING: Two university teaching hospitals. PATIENTS: Fifty-five patients aged 60 or older presenting to the emergency department with suspected dehydration were studied. MEASUREMENTS AND MAIN RESULTS: In the emergency department, patients were evaluated by a standardized history and physical examination that included assessment of 38 signs and symptoms commonly attributed to dehydration. The relationships between the presence and intensity of these putative dehydration indicators and an independent rating of dehydration severity based on a comprehensive review of the medical record were evaluated. Also evaluated were the relationships between these dehydration indicators and patient age. Indicators that correlated best with dehydration severity but were unrelated to patient age included: tongue dryness (P less than 0.001), longitudinal tongue furrows (P less than 0.001), dryness of the mucous membranes of the mouth (P less than 0.001), upper body muscle weakness (P less than 0.001), confusion (P less than 0.001), speech difficulty (P less than 0.01), and sunkenness of eyes (P less than 0.01). Other indicators had only weak associations with dehydration severity or were also related to age. Patient thirst was unrelated to dehydration severity. CONCLUSIONS: A set of signs and symptoms related to dehydration severity in elderly patients has been identified. These indicators may be more useful for evaluation of dehydration severity in the emergency department than other commonly used indicators.

Aged↗

PubMed2004

Water and electrolyte salvage in an animal model of dehydration and malnutrition.

BACKGROUND AND AIM: Recently, a new oral rehydration solution (ORS) called Resomal has been designed specifically for children with severe malnutrition. The aim of this study was to assess the effect of malnutrition on renal and intestinal responses to dehydration, and to compare intestinal water and electrolyte absorption from Resomal and from the standard World Health Organization-Oral Rehydration Solution (WHO-ORS). METHOD: Malnutrition was achieved in a rabbit model by feeding the animals daily for 30 days with half the amount of food that a well-nourished group of control animals had consumed on the previous day. Dehydration was achieved by water deprivation for 46 hours in both control and malnourished rabbits. At 46 hours, dehydration was assessed by changes in body weight, urinary volume and osmolarity, and blood urea nitrogen concentration. At that time active colonic and jejunal mucosal electrolyte transport in Ussing chambers was also measured. Small intestinal absorption of water, sodium, and potassium was measured in vivo during intestinal perfusion of the two ORSs and in vitro by measurement of mucosal electrogenic glucose-stimulated sodium absorption across intestinal patches. RESULTS: Compared to controls (C), well-nourished but dehydrated (C+D) animals lost 12% of their body weight, with an 87% reduction in urine volume, a 110% increase in urine osmolality, and a 94% increase in blood urea nitrogen. In the colon of C+D animals, short-circuit current (Isc) and net sodium transepithelial flux (JNa+ net) were increased. Almost identical results were obtained in malnourished and dehydrated (M+D) animals. In the jejunum, net in vivo absorption of water (JWater), sodium (JNa+), and potassium (JK+) were increased during standard ORS infusion in both dehydrated groups. During Resomal infusion, water absorption was the same as seen with WHO-ORS, but sodium absorption was reduced, and potassium absorption was increased in both well-nourished and malnourished dehydrated animals. In vitro, compared to controls, the glucose-stimulated short-circuit current (DeltaIsc), JNa+ net and G were increased in both dehydrated groups. CONCLUSION: During experimental dehydration, the kidney and large intestine salvage water and electrolytes, thus reducing the consequences of dehydration. These findings indicate that jejunal water absorption from Resomal and WHO-ORS is increased during dehydration, but Resomal allows for less sodium and more potassium to be absorbed, both in well-nourished and malnourished dehydrated rabbits.

Animals↗

PubMed2004

Value of laboratory studies in assessment of dehydration in children.

BACKGROUND: Due to the lack of a reliable way of clinically measuring dehydration, laboratory tests are usually used to improve the accuracy of clinical assessment of dehydration in children. The purpose of this study was to compare the relationship between clinical and laboratory parameters in the assessment of dehydration and to evaluate the improvement of those parameters over time. METHODS: We conducted a retrospective study to assess the relationship between clinical assessment of dehydration and laboratory findings. RESULTS: Three hundred children were eligible for the study. Twenty-six per cent of those with mild dehydration had serum urea concentrations greater than 14.3 mmol/L, compared with 38% and 5% of those with moderate or no dehydration, respectively. Urea concentration showed a good specificity, 95%. Creatinine concentrations and mean pH were similar whether or not dehydration was present. Bicarbonate and base excess concentrations decreased with the increasing severity of dehydration and were significantly greater in subjects with moderate dehydration than in those without. The sensitivity (71%) and specificity (74%) of both tests were rather poor. All groups had an abnormal anion gap, which was significantly greater in those with mild or moderate dehydration. CONCLUSION: This study confirms that there is a discrepancy between clinical assessment and laboratory parameters of dehydration. Urea showed good specificity, and anion gap was the most sensitive laboratory parameter for assessment of dehydration. These findings need further validation.

Adolescent↗

PubMed2000

Permeability of the infective juveniles of Steinernema carpocapsae to glycerol during osmotic dehydration and its effect on biochemical adaptation and energy metabolism.

Permeability of the sheath and cuticle of the infective juveniles (IJs) of Steinernema carpocapsae to glycerol and its effect on biochemical adaptation of the IJs to osmotic dehydration were examined by incubating both sheathed and exsheathed IJs in glycerol-d5 solution then monitoring the changes in levels of deuterium labelled and non-labelled glycerol and trehalose. Energy metabolism of the IJs during osmotic dehydration and subsequent rehydration and the effect of the permeated glycerol on this process were investigated by examining and comparing the changes in mean dry weight and key biochemical composition of the IJs dehydrated in glycerol and sodium chloride solutions. The results show: (1) similarly to evaporative dehydration, osmotic dehydration induces IJs to synthesise the protectants glycerol and trehalose; (2) glycerol permeates the sheath and the cuticle into the body of IJs during dehydration in glycerol solution. Part of the permeated glycerol plays a role as protectant like that synthesised by IJs from their energy reserve materials while part is incorporated into trehalose; (3) the sheath reduces the rate of permeation of glycerol and therefore affects the equilibrium glycerol and trehalose levels of the IJs and also the time needed to reach the equilibrium levels; (4) the reduction in mean dry weight and lipids of the IJs during dehydration in glycerol solution is substantially less than those dehydrated in sodium chloride solution. Both the total protectant level and the ratio of glycerol to trehalose of the IJs dehydrated in glycerol solution are higher than those dehydrated in sodium chloride solution; (5) glycogen reserves of the IJs play a role as a buffer reservoir of the protectants during both dehydration and rehydration but the principal sources of the protectants during dehydration are more likely to be lipids and proteins rather than glycogen.

Adaptation, Physiological↗

PubMed2002

In vitro evaluation of the dehydration characteristics of silicone hydrogel and conventional hydrogel contact lens materials.

PURPOSE: This study investigated the in vitro dehydration performance of silicone hydrogel and conventional hydrogel contact lens materials. METHODS: In vitro dehydration was assessed using a gravimetric method. The mass loss over time of Focus Night&Day, PureVision, Optima, Acuvue and Proclear Compatibles was measured as the ambient temperature increased from room temperature to 34 degrees C under varying airflow and humidity conditions. RESULTS: Dehydration data demonstrated a typical ogival form. The results were best fitted with a double exponential, non-linear regression model, which accounted for at least 99% of the variance. Regardless of material, increased airflow had a greater impact on dehydration rate than increased humidity (P<0.05). Relative dehydration amounts were strongly correlated with initial water content (r(2)=0.92), with higher water content materials dehydrating to a greater extent. CONCLUSIONS: In vitro dehydration studies of conventional and novel silicone-containing hydrogel materials indicated that evaporation rates from materials are predominantly water content related, with only subtle differences between materials of similar water contents being seen. Environmental conditions have a significant impact on in vitro dehydration, with increased airflow having a greater impact than reduced humidity on increasing dehydration rates. In vitro dehydration is closely related to bulk water diffusion rates and, as a result of their low water content, silicone-containing hydrogel materials exhibit low levels of dehydration compared with high water content hydrogel contact lens materials. Further, in vivo studies are necessary to see if the in vitro dehydration behaviour of silicone hydrogel materials is predictive of in-eye performance.

Journal Article↗

PubMed1983

Dehydration Injury in Germinating Soybean (Glycine max L. Merr.) Seeds.

The sensitivity of soybean (Glycine max L. Merr. cv Maple Arrow) seeds to dehydration changed during germination. Seeds were tolerant of dehydration to 10% moisture if dried at 6 hours of imbibition, but were susceptible to dehydration injury if dried at 36 hours of imbibition. Dehydration injury appeared as loss of germination, slower growth rates of isolated axes, hypocotyl and root curling, and altered membrane permeability. Increased electrolyte leakage due to dehydration treatment was observed only from isolated axes but not from cotyledons, suggesting that cotyledons are more tolerant of dehydration. The transition from a dehydration-tolerant to a dehydration-susceptible state coincided with radicle elongation. However, the prevention of cell elongation by osmotic treatment in polyethylene glycol (-6 bars) or imbibition in 20 micrograms per milliliter cycloheximide did not prevent the loss of dehydration tolerance suggesting that neither cell elongation nor cytoplasmic protein synthesis was responsible for the change in sensitivity of soybean seeds to dehydration. Furthermore, the rate of dehydration or rate of rehydration did not alter the response to the dehydration stress.

Journal Article↗

PubMed1983

Characterization of Solute Efflux from Dehydration Injured Soybean (Glycine max L. Merr) Seeds.

Soybean (Glycine max L. Merr) seeds lose their tolerance of dehydration between 6 and 36 hours of imbibition. Soybean axes and cotyledons were excised 6 hours (tolerant of dehydration) and 36 hours (susceptible) after commencing imbibition and subsequently dehydrated to 10% moisture. Kinetics of the efflux of potassium, phosphate, amino acid, sugar, protein, and total electrolytes were compared in the four treatments during rehydration. Only slight differences were observed in the kinetics of solute efflux between the two cotyledon treatments dehydrated at 6 and 36 hours suggesting that the cotyledons may retain their tolerance of dehydration at this stage of germination. Several symptoms of injury were observed in the axes dehydrated at 36 hours. An increase in the initial leakage of solutes during rehydration, as quantified by the y-intercept of the linear regression line for solute efflux between 2 and 8 hours suggests an increased incidence of cell rupture. An increase in the rate of solute efflux (slope of regression line between 2 and 8 hours) from fully rehydrated axes was observed in comparison to axes dehydrated at 6 hours. The Arrhenius activation energy for potassium, phosphate, and amino acid efflux decreased and for protein remained unchanged. Both observations indicate an increase in membrane permeability in dehydration-injured tissue. Increasing the H(+) concentration of the external solution increased K(+) efflux from both control and dehydrated/rehydrated samples, increased sugar efflux from axes at 6 hours imbibition but decreased sugar efflux from axes at 36 hours imbibition, indicating changes in membrane properties during germination. The dehydration treatment did not alter the pattern of the pH response of axes dehydrated at 6 or 36 hours but did increase the quantity of potassium and sugar efflux from dehydration injured axes. These results are interpreted as indicating that dehydration of soybean axes at 36 hours of imbibition increased both the incidence of cell rupture during rehydration and altered membrane permeability of the rehydrated tissue.

Journal Article↗

PubMed2000

Effects of dehydration on plasma osmolality, thirst-related behavior, and plasma and brain angiotensin concentrations in Couch's spadefoot toad, Scaphiopus couchii.

Under dehydrating conditions, many terrestrial vertebrates species exhibit increases in plasma osmolality and their drinking behavior. Under some circumstances, this behavioral change is accompanied by changes in plasma and central angiotensin concentrations, and it has been proposed that these changes in angiotensin levels induce the thirst-related behaviors. In response to dehydration, the spadefoot toad, Scaphiopus couchii, exhibits thirst-related behavior in the form of cutaneous drinking. This behavior has been termed water absorption response (WR) behavior. Spadefoot toads live in harsh desert environments and are subject annually to dehydrating conditions that may induce thirst-related behavior. We tested the hypothesis that an increase in WR behavior is associated with both an increase in plasma osmolality and an increase in plasma and brain angiotensin concentrations. First, we determined the degree of dehydration that was necessary to initiate WR behavior. Animals dehydrated to 85% of their standard bladder-empty weight via deprivation of water exhibited WR behavior more frequently than control toads left in home containers with water available. Next, using the same dehydration methods, we determined the plasma osmolality and sodium concentrations of dehydrated toads. Toads dehydrated to 85% standard weight also had a significant increase in plasma osmolality, but exhibited no overall change in plasma sodium concentrations, indicating that while an overall increase in plasma osmolality appears to be associated with WR behavior in S. couchii, changes in sodium concentrations alone are not sufficient to induce the behavior. Finally, plasma and brain angiotensin concentrations were measured in control toads and toads dehydrated to 85% standard weight. Plasma and brain angiotensin concentrations did not increase in dehydrated toads, indicating that dehydration-induced WR behavior that is associated with changes in plasma osmolality may not be induced by changes in endogenous angiotensin concentrations in S. couchii.

Angiotensin II↗

PubMed2005

Is the prevalence of dehydration among community-dwelling older adults really low? Informing current debate over the fluid recommendation for adults aged 70+years.

OBJECTIVE: The fluid recommendation for adults aged 70+ years has been criticised on the basis of a low prevalence of dehydration in community-dwelling older adults. This study explores whether the low prevalence might reflect limitations of individual dehydration indices. DESIGN: Cross-sectional data on plasma sodium, blood urea nitrogen (BUN), creatinine, glucose and potassium were used to classify 1,737 participants of the 1992 Established Populations for Epidemiologic Studies of the Elderly (EPESE) (70+ years) according to multiple dehydration indices. Associations between dehydration indices, health and functional status were evaluated. RESULTS: Depending on the indicator used, the prevalence of dehydration ranged from 0.5% for hypotonic hypovolaemia only (plasma tonicity < 285 mOsm l(-1) with orthostatic hypotension) to 60% with dehydration defined as either plasma sodium >or=145 mEq l(-1), BUN/creatinine ratio >or=20, tonicity >or=295 mOsm l(-1), or hypotonic hypovolaemia. Elevated tonicity and BUN/creatinine ratio were respectively associated with chronic disease and functional impairment. CONCLUSIONS: The true prevalence of dehydration among community-dwelling adults may be low or high, depending on the indicator(s) used to define dehydration. Before we can pinpoint a generalisable prevalence of dehydration for community-dwelling seniors and draw conclusions about fluid recommendations, validation studies of dehydration indices and longitudinal studies of dehydration, health and functional status are needed.

Aged↗

PubMed2000

Effect of mild dehydration on the lactate threshold in women.

PURPOSE: The purpose of this investigation was to examine the effects of dehydration on the lactate threshold and performance time to exhaustion in women. METHODS: Seven moderately trained women (age = 23.6 +/- 1.6 yr) performed two graded exercise tests on separate occasions, once in a normally hydrated state (HY) and once in a dehydrated state (DE). Dehydration was achieved by a 45-min submaximal exercise the evening before testing, followed by a 12-h period of fluid restriction. VO2, VCO2, V(E), R-values, blood lactate, and catecholamine concentrations were measured at baseline and during each workload. Plasma volume and plasma osmolality were also determined. Body weight dropped significantly for the dehydrated trial (2.6 +/- 0.7%). RESULTS: There was a corresponding decrease in plasma volume measured (3.5 +/- 2.6%). The VO2max (3.1 +/- 0.3 L x min(-1) HY; 3.0 +/- 0.1 L x min(-1) DE) obtained was not significantly different between the hydration and dehydration trial. Plasma norepinephrine, epinephrine, and lactate concentrations were not significantly different at baseline or maximum intensity although epinephrine concentrations were higher for the dehydrated trial during submaximal workloads. Lactate concentrations were highly correlated with epinephrine (r = 0.95 HY; r = 0.97 DE). The lactate threshold occurred at a significantly lower relative percent of VO2max for the dehydrated trial (72.2 +/- 1.1% HY; 65.5 +/- 1.8% DE) as well as a lower absolute power output when compared with that in the hydrated trial. There was a significant decrease in time to exhaustion for the dehydrated trial (17.3 +/- 0.7 min HY; 16.3 + 0.7 min DE). Time to exhaustion for the dehydrated trial was correlated with the % VOmax at which the lactate threshold occurred (r = 0.74). CONCLUSIONS: These data indicate that low levels of dehydration induced a shift in the lactate threshold, in part because of elevated epinephrine concentrations. This shift may have been one cause for the decrease in time to exhaustion for the dehydrated trial.

Adolescent↗

PubMedDate not supplied

Is biolectrical impedance analysis a tool at bedside, during heat waves to assist geriatricians with discriminative diagnosis of hypertonic dehydration?

OBJECTIVES: To assess BIA data given by Analycor 3 and some bio-impedance equations to assist geriatricians with discriminative diagnosis of hypertonic dehydration, during heat waves. DESIGN: Prospective study: a dehydrated patients group has been compared with a randomised control group. SETTING: The study was carried out in a French geriatric department, in the Emile Roux geriatric hospital. PARTICIPANTS: 36: six men and twelve women in each group. MEASUREMENTS: The most valuable clinical indicators of dehydration severity were recorded and scored. BIA measurements were performed with an Analycor 3 analyzer; TBW was calculated from impedances at 50 and 100 kHz, ECW from impedance at 5 kHz; Calculations were made also with formula described in the literature, validated in healthy or in institutionalised elderly subjects. RESULTS: TBW and ECW values were always lower in dehydrated group than in control group, but without significance, whatever the applied formula; however ICW values calculated with "manufacturers equations" significantly decreased in dehydrated group. Data given by the analyzer used in this study, as well as BIA age specific equations discriminated the severely hypertonic dehydrated patients sub-group, but not the mildly hypertonic dehydrated patients sub-group. CONCLUSION: The BIA data given by the analyzer used in this study assist geriatricians at bedside with discriminative diagnosis of hypertonic dehydration, especially in severe hypertonic dehydration, but data given by the analyzer used in this study, as well as age specific equations are sometimes in poor agreement with clinical and biological parameters usually selected to assess dehydration, in mildly dehydrated patients.

Aged↗

PubMed2004

Clinical presentation of hypernatremic dehydration in exclusively breast-fed neonates.

OBJECTIVE: To identify the clinical presentation of dehydration related to failure of lactation in exclusively breast-fed term infants. METHOD: A prospective study was performed between January 2000 and June 2003 in Al Qassimi Hospital in the Emirate of Sharjah. Enrollment criteria included term neonates whose birth weight of > 2000 g with no underlying organic illness causing poor feeding admitted for clinical manifestations of dehydration with weight loss of > 10% during the first 2 weeks of life. The control group, a non-randomized sample included healthy full term neonates, seen in Sharjah maternal and child health care center at 4-7 days old for their routine Guthrie screening test. For each dehydrated neonate we took two neonates as controls. Mother's age, parity, length of pregnancy, any pathologic conditions, breastfeeding history and her level of knowledge of lactation was recorded. Neonatal information included mode of delivery, percentage of weight loss, clinical examination, and stool and urine output the previous day. Data was analyzed with Student 't' test and chi-square test. RESULTS: Out of 17208 live births, 29 neonates between the ages of 2-13 days were admitted with weight loss of between 12 and 29% (dehydrated group). 27 patients had hypernatremic dehydration with serum sodium level ranging from 150 to 195 mmol/l. Mean age of admission was 4.9 days. Reasons for admission were: signs of dehydration (55%); hyperthermia (55%); hypoglycemia (27%) and jaundice (59%). The control group included 58 healthy neonates. Their birth weight and age were comparable to those in the dehydrated group. In comparison with the control group, delivery by cesarean section (P< 0.0001), lower level of maternal breastfeeding knowledge (P=0.03), transient inadequate breast milk quantity (P=0.005) and nipple anomalies (P=0.001) was significantly more common in the dehydrated group. Fewer voidings of urine (< 6 times /day) and stool (< 3 times/day) in the previous 24 hours before admission was more frequently observed in the dehydrated group (P < 0.0001). CONCLUSION: Low level of maternal knowledge in lactation, cesarean section and failure of early postnatal follow up was associated with the neonatal dehydration. Decreased urine and stool frequency might be considered as a warning for failure of lactation.

Breast Feeding↗

PubMed1997

Second messenger and cAMP-dependent protein kinase responses to dehydration and anoxia stresses in frogs.

The effects of whole body dehydration (up to 40% of total body water lost) or anoxia exposure (up to 2 days under N2 gas) at 5 degrees C on tissue levels of adenosine 3'-5' cyclic monophosphate (cAMP) and the percentage of cAMP-dependent protein kinase present as the free catalytic subunit (PKAc), as well as the levels of the protein kinase C (PKC) second messenger, inositol 1,4,5-trisphosphate (IP3), were assessed in two anurans, the freeze-tolerant wood frog, Rana sylvatica, and the freeze-intolerant leopard frog, Rana pipiens. Dehydration of wood frogs resulted in a rapid elevation of liver cAMP and PKAc; cAMP was 3.4-fold greater than control values in animals that had lost 5% of total body water, whereas PKAc was elevated threefold in 20% dehydrated frogs. These results indicate protein kinase A mediation of the liver glycogenolysis and hyperglycemia that is induced by dehydration in this species. Skeletal muscle PKAc content also rose with dehydration but neither cAMP nor PKAc was affected by dehydration in leopard frog tissues. Anoxia exposure had different effects on signal transduction systems. PKAc was elevated after 1 h anoxia in R. sylvatica brain and was sustained over time but the enzyme was unaffected in other organs; by contrast, R. pipiens showed variable responses by PKAc to anoxia in three organs. Both species showed rapid (within 30 min) and large (3 to 7.8-fold) increases in IP3 in liver of anoxic frogs that decreased slowly with continued anoxia. IP3 also increased quickly in heart of anoxia-exposed wood frogs. This suggests that PKC may mediate various metabolic adjustments that promote hypoxia/anoxia resistance such as coordinating metabolic rate depression. A progressive rise in liver IP3 during dehydration in wood frogs (reaching fourfold higher than controls in 40% dehydrated animals) may also mediate similar hypoxia resistance adaptations under this stress since anurans experience progressive hypoxia due to increased blood viscosity when water loss reaches high values. The patterns of second messenger and PKAc changes in wood frog liver during dehydration closely parallel the changes seen in these same parameters during natural freezing suggesting that the freeze tolerance of selected terrestrially hibernating anurans may have evolved out of various anuran mechanisms of dehydration resistance.

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