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PubMed1991

Dehydration in dying patients: study with physicians in French-speaking Switzerland.

We surveyed physicians in French-speaking Switzerland to assess the perception of suffering resulting from dehydration and its relation to the clinical choice between oral and artificial hydration. A questionnaire describing hypothetical cases of dehydration in an elderly terminal cancer patient in different clinical situations (conscious, demented, comatose) was sent to 978 physicians. The physicians were asked to assess the discomfort due to dehydration and the treatment they would propose in order to correct this situation (oral or artificial hydration). The return rate was 41%. The results show that there is no consensus with respect to the assessment of suffering (it gets a "low" score from 33% of replies and a "high" score from 41% of replies) or of thirst ("low": 30%, "high": 43%). Only 28% of the replies indicated artificial hydration for conscious patients while 44% chose this treatment for comatose patients. Physicians choosing artificial hydration were significantly more prone to consider suffering and thirst as "serious" than those preferring hydration by mouth. It can be concluded that two thirds of the physicians who responded think that artificial hydration is not the best way to respond to dehydration in dying patients. The choice depends partly on the assessment of the suffering and thirst resulting from terminal dehydration.

Attitude of Health Personnel↗
PubMed2004

Saliva flow rate, total protein concentration and osmolality as potential markers of whole body hydration status during progressive acute dehydration in humans.

OBJECTIVE: To identify whether saliva flow rate, total protein concentration and osmolality are sensitive non-invasive markers of whole body hydration status, we compared changes in these parameters with changes in body mass during progressive acute dehydration. DESIGN: Twelve euhydrated males reported to the laboratory following an overnight fast and cycled on a stationary ergometer at 60% maximal oxygen uptake in an environmental chamber (30 degrees C and 70% RH) until progressive body mass loss (BML) of 1.1+/-0.0, 2.0+/-0.0 and 2.9+/-0.2%. After exercise, subjects were given a volume of carbohydrate electrolyte solution equivalent to 150% BML to consume within 1h. Unstimulated whole saliva samples were collected over a 2 min period into pre-weighed tubes at pre-exercise, 1.1, 2.0 and 2.9% BML and then at 75, 135 and 195 min post-exercise. RESULTS: Saliva total protein concentration and osmolality increased and flow rate decreased (P<0.01) during dehydration. Saliva total protein concentration and osmolality correlated strongly with % BML during dehydration (mean r=0.97 and 0.94, respectively: P<0.01). The correlation for saliva total protein concentration with % BML was greater (P<0.05) than the correlation for saliva flow rate with % BML (mean r=-0.88: P<0.01) during dehydration. CONCLUSIONS: These data show that changes in saliva total protein concentration and osmolality, and to a lesser extent flow rate, are strongly associated with changes in body mass during progressive acute dehydration.

Acute Disease↗
PubMed2003

The role of glutathione in yeast dehydration tolerance.

Among the factors that affect cell resistance against dehydration, oxidation is considered to be of great importance. In this work, we verified that both control and glutathione deficient mutant strains were much more oxidized after dehydration. Moreover, cells lacking glutathione showed a twofold higher increase in oxidation and lipid peroxidation than the control strain. While glucose 6-phosphate dehydrogenase and glutathione reductase activities did not change in response to dehydration in the control strain, the mutant strain gsh1 (glutathione deficient) showed a reduction of 50% in both activities, which could explain the high levels of oxidation shown by gsh1 cells. In conformity with these results, the mutant lacking GSH1 showed a high sensitivity to dehydration. Furthermore, the addition of glutathione to gsh1 cells restored survival rates to the levels of the control strain. We conclude that glutathione plays a significant role in the maintenance of intracellular redox balance during dehydration.

Dehydration↗
PubMed2006

Changes in the pool of soluble sugars induced by dehydration at the heterotrophic phase of growth of wheat seedlings.

Loss of dehydration tolerance coincides with a shift from heterotrophy to autotrophy during post-germination growth of spring wheat seedlings. This critical stage falls on the fifth day following imbibition. Till the sixth day of experiment light had no effect on dry weight of the seedlings but the survival of six day old seedlings was reduced by half upon dehydration. Germinating seeds in the presence of 5 mM glucose, fructose, mannose or sucrose did not promote seedling growth but either increase (glucose, fructose) or decreased (mannose, sucrose) the survival of dehydrated seedlings. Protection against dehydration by the former sugars was correlated, irrespective of the seedling age, with the decrease of sugar pool in seeds and increase in shoots (coleoptile and first leaf) and roots. The opposite changes were provoked by the sugars hampering seedling survival. Generally, survival of wheat seedlings was not correlated with the size of soluble sugar pool but its distribution and composition. Lower mobilisation of soluble sugars in seed, lower proportion of reduced sugars to sucrose and higher share of raffinose is characteristic for the tolerant four day old seedlings and those grown in the media containing glucose or fructose. The results presented indicate that higher proportion of reduced sugars to sucrose and lower share of raffinose in six day old seedlings seems to be associated with the loss of dehydration tolerance of these seedlings, despite heterotrophic character of growth.

Carbohydrates↗
PubMed2004

Buffering limits plasma HCO3- dehydration when red blood cell anion exchange is inhibited.

Theory suggests that HCO3- dehydration in the plasma of rainbow trout is limited by both the absence of carbonic anhydrase (CA) activity and the low non-bicarbonate buffer capacity of the plasma (betaplasma). The potential for betaplasma to limit plasma HCO3- dehydration was assessed in rainbow trout in which HCO3- dehydration via the red blood cell (RBC) was inhibited using the anion exchange blocker 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS). DIDS administration reduced the rate of RBC HCO3- dehydration by 68-80% for at least 6h, resulting in the elevation of arterial CO2 tension (PaCO2) by 3.07 +/- 0.45 Torr (N = 6). Addition of bovine CA to the circulation of DIDS-treated trout caused PaCO2 to decrease significantly. This effect was increased significantly in rainbow trout in which betaplasma was elevated experimentally by intravascular injection of N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid] (HEPES), supporting the hypothesis that CA-catalysed HCO3- dehydration in the plasma of rainbow trout is limited by proton availability.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1998

Effects of intracerebroventricular dizocilpine (MK801) on dehydration-induced dipsogenic responses, plasma vasopressin and c-fos expression in the rat forebrain.

This study determines the interaction between glutamate receptors and dehydration-induced drinking, vasopressin (AVP) release, plasma osmolality and c-fos expression in the brain of conscious rats. The NMDA receptor antagonist dizocilpine (100 nmol infused into the cerebral ventricles) suppressed drinking following either 22 h water deprivation or intragastric injection of hypertonic saline (1.5 M), attenuated the increased plasma vasopressin induced by dehydration, but had no effects on peripheral hyperosmolality caused by either water deprivation or injections of hypertonic saline. Dizocilpine had no inhibitory effects on feeding after 24 h food deprivation. Dizocilpine also suppressed c-fos expression induced by dehydration in the median preoptic nucleus (MPN), the supraoptic and paraventricular nuclei (SON and PVN), but did not influence c-fos expression in the subfornical organ (SFO). The non-NMDA receptor antagonists CNQX (400 nmol) or DNQX (60 nmol) affected neither the animals' drinking nor c-fos expression induced by dehydration. Double staining showed that suppression of c-fos expression following dizocilpine occurred in the NMDA R1 receptor containing neurons in the hypothalamus. These results suggest that the NMDA-type glutamate receptors may be involved in dehydration induced dipsogenic and neuroendocrinological responses. They complement our earlier findings that dizocilpine also attenuates drinking and c-fos expression following intraventricular infusions of angiotensin II.

Animals↗
PubMed1998

Age-associated decrease in response of rat aquaporin-2 gene expression to dehydration.

It is well known that urine-concentrating ability decreases with aging and that this decreasing ability results from a reduced sensitivity of the renal collecting duct to arginine vasopressin (AVP). AVP regulates the water channel (aquaporin-2:AQP2) through V2 receptors and increases the water permeability of the collecting duct. To elucidate the mechanism of change with aging in urine-concentrating ability, we investigated the change of V2 receptor and AQP2 mRNA expression in young (8-week-old) and older (7-month-old) rats after dehydration for 2 days. After dehydration, plasma AVP levels in older rats were higher than young rats, and urinary osmolality in older rats was lower than young rats. By Northern blot analysis, there was no significant difference between young and older rats in both V2 receptor and AQP2 mRNA expression before dehydration. After dehydration, V2 receptor mRNA expression in young and older rats decreased in the same degree, suggesting the downregulation of V2 receptors may occur in the mRNA level. Northern blot analysis and in situ hybridization histochemistry showed that AQP2 mRNA expression increased and the increased expression in older rats was less than in young rats. The present study suggests the reduced response of AQP2 mRNA expression to dehydration, observed in 7-month-old rats, might be partially responsible for the decreasing urine-concentrating ability with aging.

Aging↗
PubMedDate not supplied

Role of rumen fluid hypertonicity in the dehydration-induced hypophagia of cows.

Three experiments were performed in non-lactating, rumen-fistulated cows to assess the role of rumen fluid hypertonicity in dehydration-induced hypophagia. First, the course of rumen fluid and plasma osmolality before and after an individual test meal was recorded when water was offered ad libitum and on the fifth day of a 65% water restriction period. Then, the effects of intraruminal water infusions on food intake were examined in dehydrated cows. Finally, two doses of the local anesthetic mepivacaine HCl were given into the rumen in an attempt to inactivate the osmosensors potentially involved in dehydration-induced hypophagia. Water restriction reduced test meal size and increased rumen fluid and plasma osmolality. Despite the smaller meal, the prandial increase in rumen fluid osmolality was more pronounced during water restriction than with water ad libitum. Independent of treatment, the test meal had no effect on plasma osmolality. Intraruminal water infusions during water deprivation decreased rumen fluid osmolality below the control level and normalized food intake. Injection of 2 or 4 g mepivacaine/cow into the rumen did not attenuate dehydration-induced hypophagia. All in all, these results suggest that rumen fluid hypertonicity, perhaps in concert with plasma hypertonicity, contributes to the early satiation induced by dehydration.

Anesthetics, Local↗
PubMed1997

Effects of preloads of water and saline on thermal dehydration-induced thirst.

The relative contribution of cellular and extracellular water deficits to the genesis of thirst due to thermal dehydration was studied in male Sprague-Dawley rats following exposure to a 40 degrees C environment for 4 h. Intragastric (I.G.) and intravenous (I.V.) preloads of water reduced the elevated plasma sodium and plasma osmolality of thermally dehydrated rats to control levels, but preloads of saline did not. I.G. and I.V. preloads of saline returned the hematocrit and plasma protein concentration of thermally dehydrated rats to control levels. Both the I.G. water preload and the I.G. saline preload reduced water intake, with the I.G. water preload having a greater effect. The I.V. water preload reduced water intake nearly to control levels, whereas the I.V. saline preload was without effect on water intake. These data indicate that the water intake of thermally dehydrated rats is primarily due to a cellular water deficit and that oral and gastric factors are also important in terminating water intake in thermally dehydrated rats.

Animals↗
PubMed2003

Comparison of dehydration and angiotensin II-stimulated cutaneous drinking in toads, Bufo punctatus.

Toads (Bufo punctatus) use a sequence of two postures to place the ventral skin on a moist surface and absorb water osmotically. First, the skin contacts the surface (seat patch down, SPD), and then the hindlimbs are abducted to maximize skin contact area (water absorption response, WR). Toads modulated behavior in response to hydration status and osmotic content of the hydration source. Dehydrated toads placed on water displayed both SPD and WR. Hydrated toads injected with angiotensin II (AII) displayed SPD longer than Ringer-injected controls but did not initiate WR and absorbed less water than dehydrated toads. These results suggest that dehydration has a more robust dipsogenic effect than AII. Dehydrated toads placed on 250 mM NaCl briefly initiated SPD but not WR. The addition of amiloride to the hyperosmotic salt solution resulted in brief display of WR but no water loss. Hydrated toads placed on 250 mM NaCl showed shorter periods of SPD behavior. The combination of AII injection and amiloride addition to the salt solution increased SPD initiation but SPD duration was short and water loss was prevented. Neither AII nor dehydration overrides chemosensory mechanisms in the skin that suppress cutaneous drinking from hypertonic solutions.

Angiotensin II↗
PubMed2002

Effect of isotope substitution and controlled dehydration on the photoinduced electron transport reactions of quinone acceptors and multiheme cytochrome C in bacterial photosynthetic reaction center.

Isotope substitution of H2O by 2H2O causes an increase in the rate of dark recombination between photooxidized bacteriochlorophyll (P+) and reduced primary quinone acceptor in Rhodobacter sphaeroides reaction centers (RC) at room temperature. The isotopic effect declines upon decreasing the temperature. Dehydration of RC complexes of Ectothiorhodospira shaposhnikovii chromatophores containing multiheme cytochrome c causes a decrease in the efficiency of transfer of a photomobilized electron between the primary and secondary quinone acceptors and from cytochrome to P+. In the case of H2O medium these effects are observed at a lower hydration than in 2H2O-containing medium. In the E. shaposhnikovii chromatophores subjected to dehydration in H2O, the rate of electron transfer from the nearest high-potential cytochrome heme to P+ is virtually independent of hydration within the P/P0 range from 0.1 to 0.5. In samples hydrated in 2H2O this rate is approximately 1.5 times lower than in H2O. However, the isotopic effect of this reaction disappears upon dehydration. The intramolecular electron transfer between two high-potential hemes of cytochrome c in samples with 2H2O is inhibited within this range of P/P0, whereas in RC samples with H2O there is a trend toward gradual inhibition of the interheme electron transfer with dehydration. The experimental results are discussed in terms of the effects of isotope substitution and dehydration on relaxation processes and charge state of RC on implementation of the reactive states of RC providing electron transfer control.

Bacterial Chromatophores↗
PubMed2003

Effects of a hypertonic saline solution and dextran 70 combination in the treatment of diarrhoeic dehydrated calves.

Thirty dehydrated diarrheic calves aged 2-45 days were used to study the effects of small volume intravenous 7.2% hypertonic saline and 6% dextran 70 solution in combination with alkalinising oral fluids and to compare this therapy with the large volume intravenous isotonic saline with alkalinising oral fluid treatment. This study included a total of 30 diarrhoeic dehydrated calves aged 2-45 days. After routine clinical and haematological examinations, the calves were allotted to two treatment groups. Isotonic saline solution (32 ml/kg, i.v.) with an oral electrolyte solution (22 ml/kg, p.o.) were administered to group I (control), and the combination of 7.2% hypertonic saline in 6% dextran 70 solutions (HSD) (4 ml/kg, i.v.) with an oral electrolyte solution (50 ml/kg, p.o.) were administered to group II (test). Additionally, an oral electrolyte solution (50 ml/kg, p.o.) was readministered to both groups at 12 h of the study. The clinical and haematological examinations of all calves were performed both before and after the treatment at the 1/2, 1, 2, 4, 12 and 24 h. The capillary refill time, peripheral pulse quality, dehydration degrees, mental status, haematocrit rates, haemoglobin and plasma values after treatment were found to be statistically different compared with the values before treatment. In comparison with group I, group II is observed to have shorter capillary refill time at 1, 4 and 12 h (P < 0.001) and better peripheral pulse quality at 1/2 (P < 0.05), 1, 2, 4 and 12 h (P < 0.001). Moreover, the degree of dehydration in group II, was significantly improved at 2 (P < 0.01), 4 and 12 h. Results of the study indicated that administration of low volumes of hypertonic sodium chloride and dextran 70 solution combinations with oral electrolyte solutions was concluded as quicker, practical, economical and most importantly an effective way for the treatment of dehydrated diarrhoeic calves.

Administration, Oral↗
PubMed2001

Urinary caffeine after coffee consumption and heat dehydration.

This study evaluated the effect of heat-induced dehydration on urinary caffeine excretion after the consumption of a strong coffee solution. Following ingestion of coffee (caffeine 4.9+/-0.1 [SE] mg/kg, 3-4 cups), ten healthy males were intermittently exposed to heat in a sauna until they had lost 2.9 % of lean mass. On a separate occasion, they consumed the same amount of coffee but remained quiet and euhydrated (control). Urine flow was reduced 7-fold in dehydration. At these low excretion rates (< 30 ml/h), caffeine concentration was negatively correlated with flow. Peak urinary caffeine (Cmax) was 7.6 +/- 0.4 (SE) microg/ml in dehydration and 7.1 +/- 0.2 microg/ml in the control (p > 0.05). Compared with the control, dehydration delayed Cmax by 1 hour, maintained higher saliva caffeine concentration (6.1 vs 5.2 microg/ml, p < 0.05) and a lower saliva paraxanthine/caffeine ratio (p < 0.001). The 24h-recovery of caffeine in urine was reduced (1.2 vs 2.8% of dose, p < 0.001), however at least 2.6% of dose were lost in sweat. These results suggest that the rise in circulating caffeine due to delayed metabolic clearance was partly opposed by a sizeable elimination in sweat. Therefore, heat dehydration did not lead to higher concentration of caffeine in urine after coffee ingestion.

Adult↗
PubMed1991

Mild dehydration and atrial natriuretic peptide in young and elderly subjects.

The influence of mild dehydration on plasma levels of atrial natriuretic peptide (ANP) was studied in both young (aged 18 to 25 years) and elderly (aged 72 to 86 years) subjects. We expected that dehydration would lower ANP concentrations due to the ensuing volume contraction. A different response of the ANP hormonal system in the elderly might help to explain the observation that elderly subjects are more predisposed to dehydration as compared to young subjects. Dehydration was induced by restriction of fluid intake to 25% of normal for one day. During the study, urinary osmolality increased while osmolar clearance and body weight decreased. Basal ANP concentrations were higher in the elderly subjects. However, these levels did not change during the dehydration study neither in the young nor in the elderly subjects. This may be explained by the activation of counter-regulatory systems preventing a decrease in central blood volume and hence a decrease in ANP concentration.

Adolescent↗
PubMed1998

Separate and combined influences of dehydration and hyperthermia on cardiovascular responses to exercise.

During endurance exercise in the heat athletes lose 1-21/h of fluid due to thermoregulatory sweating. The ensuing dehydration is accompanied by higher and faster increases in core temperature, which per se can cause fatigue. The main cardiovascular consequences of combined dehydration and hyperthermia [1 degree C higher core temperature and 3-4 kg (4%) body weight loss] are the significant reductions in cardiac output (3 l/min), muscle blood flow, skin blood flow and blood pressure. Separately, however, hyperthermia (i.e., 39.3 C) and dehydration do not significantly reduce cardiac output or blood pressure. In conclusion, the superimposition of dehydration on hyperthermia during exercise in the heat causes greater alterations in cardiovascular function that make the dehydrated athlete much less able to cope with hyperthermia.

Blood Pressure↗
PubMed1990

Arginine vasotocin and mesotocin in the anterior hypothalamus, neurohypophysis, proventriculus and plasma of White Leghorn cockerels, during dehydration.

1. The effect of 96 hrs of water deprivation on plasma electrolytes, osmolarity, arginine vasotocin (AVT), mesotocin (MT), and on AVT and MT content in the neurohypophysis, anterior hypothalamic area (AHA) and proventriculus, was studied at 24 hrs intervals, in adult White Leghorn cockerels. 2. Plasma AVT increased three fold during the first 24 hrs but there was no further change during the next 48 hrs. In the last 24 hrs, plasma AVT decreased in about 25%. Plasma MT did not change during the entire period of dehydration. 3. Plasma sodium and osmolarity gradually increased during that time. 4. Neurohypophysial AVT content was depleted by 95% during the period of dehydration while MT content did not change. 5. In the AHA there was no change in AVT levels during dehydration while the levels of MT increased while in the proventriculus there was no change in either AVT or MT levels. 6. For the data collected during the entire experimental period, no correlation was found between plasma osmolarity and plasma AVT, but there was a highly significant negative correlation between plasma osmolarity and neurohypophysial AVT content. 7. It may be suggested that the depletion in AVT content in the neurohypophysis during progressive water deprivation resulted in an insufficient level of AVT in circulation to enable the cockerels to counter the dehydration. This may explain the death of those cockerels which were dehydrated for a further 24 hr period.

Animals↗
PubMed1993

Disturbed fluid and electrolyte homoeostasis following dehydration in elderly people.

Disturbances in homoeostatic capacity are typical of the ageing process. Changes in the neuroendocrine controls of salt and water homoeostasis with age make elderly people more susceptible to fluid and electrolyte disturbances such as dehydration and overhydration. Not only do elderly subjects show reduced thirst and water intake following dehydration, but their kidneys are less able to retain water. This reduced thirst and water intake is not dependent on palatability of the liquids offered as the amounts drunk are no different if water alone or a variety of beverages are offered to healthy elderly dehydrated men. It is of interest that the arginine vasopressin (AVP) response to dehydration is maintained in elderly subjects, indicating that their reduced renal water retentive capacity is due to relative renal resistance to vasopressin. The mechanism underlying the reduced thirst is unclear. Dehydration causes plasma hypertonicity and reduced extracellular fluid (ECF) volume, both of which stimulate thirst and AVP secretion. Elderly subjects show deficits in sensing the reduced ECF volume through reduced low and high pressure baroreceptor sensitivity. In contrast, while the AVP responses to hypertonicity are maintained, the thirst responses seem to be reduced. It seems unlikely that the primary sensing 'osmoreceptor' neurons in the hypothalamus leading to AVP secretion or thirst would be differentially affected by age. Therefore the thirst deficit may result from changes with age in the more poorly defined pathways that bring thirst to consciousness. Following rehydration, thirst and AVP secretion are inhibited in young individuals thus avoiding overhydration.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Is it possible to predict which diarrhoea episodes will lead to life-threatening dehydration?

Early detection of children who are likely to develop life-threatening dehydration as a consequence of diarrhoea would be of great value for health care workers in developing countries. We carried out a case-control study to compare the symptoms and signs observed on the first day of diarrhoea in two groups of 192 children aged under two years, in the Brazilian city of Porto Alegre. The cases were children admitted to a hospital with moderate or severe dehydration, and controls were children from the same neighbourhoods as the cases, who had diarrhoea which did not lead to hospital admission. The sensitivity and specificity of different clinical indicators were calculated. Alterations in thirst (82%), followed by six or more stools (71%), fever (60%), vomiting (58%) and loss of appetite (57%) had the highest sensitivities, whereas the specificities were largest for blood in the stools (97%), fever (78%) and vomiting (78%). Assuming that dehydration occurs in 5% of all episodes of diarrhoea, the use of fever as a screening criterion, or the use of vomiting, would select 24% of all children with diarrhoea, and capture about 60% of all episodes of dehydration. The combination of fever or vomiting would increase the proportion selected to 36%, and capture 75% of episodes of dehydration.

Brazil↗