SEARCH · PubMed Health

Results for “Dehydration”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed2000

Effect of dehydration on gastrointestinal function at rest and during exercise in humans.

Dehydration leads to the aggravation of gastrointestinal (GI) complaints during exercise. The aim of this study was to examine the effect of dehydration on various GI parameters during strenuous exercise. Ten healthy well-trained men were investigated in dehydrated and in euhydrated conditions. Dehydration took place before the experiments using a dehydration regimen in a sauna leading to a 3% loss of body mass. Each experiment consisted of 1 h pre-exercise rest, 1.5 h cycling at 70% maximal exercise intensity, and 3.5 h post-exercise rest. During cycling, liquid gastric emptying (GE), orocaecal transit time (OCTT) and intestinal permeability and glucose absorption were measured. The GI-symptoms were scored using a questionnaire. Body temperature, plasma volume and vasopressin were measured before and after cycling. The GE was significantly slower during dehydration [median time to peak 13C enrichment in the breath sample (13C-TTP) 23.6 min, range 13.7-50.0 min, P = 0.02] than in the control situation (median 13C-TTP 17.1 min, range 9.8-38.4 min). The OCTT was unchanged (median 173 min, range 98-263 min compared to median 128 min, range 98-195 min, P = 0.18). Dehydration did not change intestinal permeability, glucose absorption, plasma volume, rectal temperature or plasma vasopressin concentration. In the dehydration experiment, exercise induced a significant increase in nausea (P = 0.01) and epigastric cramps (P = 0.05), in contrast to the control situation. In both experiments, exercise led to a significant increase in rectal temperature and plasma vasopressin concentration, and a significant decrease in plasma volume. The increase in plasma vasopressin concentration was significantly higher in the dehydration experiment (P = 0.015). No significant differences in either the post-exercise rectal temperatures or in plasma volumes was observed. The difference in GE between the two experiments was significantly correlated with the difference in nausea score (r = 0.87, P = 0.002). We concluded that dehydration leads to a delayed GE but not to differences in OCTT, intestinal permeability or glucose uptake during intense cycling. The delay in GE is significantly associated with an increase in exercise-induced nausea.

Absorption↗

PubMed2005

[Hypernatremic dehydration in children: retrospective study of 105 cases].

UNLABELLED: The hypernatremic dehydration defined by a serum sodium concentration> or = to 150 mmol/l, is a particular form of acute dehydration and constitutes a medical emergency requiring a prompt and adequate diagnosis and management. PURPOSE: To precise the epidemiological profile, course, causes and therapeutic particularities of hypernatremic dehydration in children. POPULATION AND METHODS: Retrospective review of 105 children admitted in the general Paediatrics department of the Fattouma Bourguiba university hospital in Monastir (Tunisia), for hypernatremic dehydration between January 1st 1990 and December 31 2002. RESULTS: Hypernatremic dehydration represented 11.51% of all kinds of dehydration. The mean age was 6.5 months with a small male predominance. The socio-economic level of the parents was good in 62.8% of cases. Half of the children were in shock. Severe dehydration was present in 87.6% of cases and neurological signs were observed in 77.14% of cases. The initial mean serum sodium concentration was 159 mmol/L. Acidosis and acute renal failure were associated respectively in 97.2% and 76.2% of cases. Prominent cause of hypernatremic dehydration was diarrhoea (94.3%). Intravenous rehydration with 5% glucose solution at the average of 147 ml/kg/day and containing a mean sodium level of 42 mmol/L was performed in 74% of cases. In most cases (84.1%) serum sodium was normalized within the first 72 hours. Complications were noted in 5.7% of cases and mortality rate was 11.4%. CONCLUSION: Hypernatremic dehydration was common in infant and the prominent cause is still dominated by diarrhoea in our country. The management of hypernatremic dehydration is based on oral or intravenous rehydration and plasma expanding fluids when shock is present or imminent. The serum sodium concentration should be gradually corrected and should not exceed 0.5 mmol/L/h. Prevention is based on the pursuit of breastfeeding and the use of oral rehydration solution in infantile diarrhoeas.

Dehydration↗

PubMed2006

Effect of pulverization and dehydration on the pharmaceutical properties of calcium lactate pentahydrate tablets.

The effects of heat conduction and pulverization on dehydration kinetics and tablet hardness were studied by a variety of kinetic equations and physical models. The dehydration behavior of unpulverized calcium lactate pentahydrate (UCLP) and pulverized calcium lactate pentahydrate (PCLP) tablets was investigated by using differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). The hardness of both UCLP and PCLP tablets was significantly decreased after dehydration. The relationship between the extent of dehydration and the tablet hardness of both UCLP and PCLP tablets was linear. The results suggest that the reduction in tablet hardness is dependent on the dehydration of crystal water, and the values of the slopes indicate that the bonding energy of the UCLP was stronger than that of the PCLP. The dehydration of both UCLP and PCLP tablets at 55 degrees C followed a one-dimensional diffusion mechanism, whereas dehydration at storage temperatures of 60-80 degrees C followed a three-dimensional diffusion mechanism. UCLP and PCLP tablets contracted in thickness and diameter during dehydration, but final contraction ratios showed that PCLP tablets were more affected than UCLP tablets. In contrast, the micropore radius of both UCLP and PCLP tablets increased after dehydration. Thus, the pharmaceutical properties of calcium lactate pentahydrate (CLP) tablets are affected both by pulverization and by the extent of dehydration of the bulk powder in the tablet formulation.

Calcium Compounds↗

PubMed2002

Biological mechanisms underlying voice changes due to dehydration.

Four vocally untrained healthy adults, 2 men and 2 women, completed the study. A double-blind placebo-controlled approach was used to administer three treatments to each participant on separate days. Drugs treatments involved a single 60-mg dose of a diuretic, Lasix (LA), on one day, and a single 50-mg dose of an oral antihistamine, diphenhydramine hydrochloride (DH), on another day. A third day involved the administration of a placebo, sugar pills (SP). Critical posttreatment measures were weight (kg), which estimated systemic dehydration, saliva viscosity (centipoise), which estimated secretion dehydration, and phonation threshold pressure (PTP, in cm H2O), at high pitches, which indicated pulmonary drive for phonation. The central experimental question was: Does systemic dehydration, or secretory dehydration, or both, mediate increases in PTP that are known to occur following dehydration treatments? The results showed that LA induced systemic dehydration, as shown by a decrease in total body mass of about 1%. Weight losses were seen during a 1- to 4-hour block following drug administration and persisted for at least 8 hours thereafter. PTPs also increased in that condition, about 23% relative to baseline, but only several hours after whole-body dehydration was initially seen (5-12 hours after drug administration). In contrast, no evidence was seen that DH accomplished either secretory dehydration or PTP shifts. The results indicate that systemic dehydration can mediate PTP increases. The influence of secretory dehydration on PTP is unclear.

Adult↗

PubMed1997

A prospective study of the usefulness of clinical and laboratory parameters for predicting percentage of dehydration in children.

To evaluate the relative utility of clinical and laboratory parameters of dehydration in children for predicting the magnitude of percent less of body weight (PLBW), we studied 97 children who required intravenous fluids for acute dehydration. After a complete history and physical examination, the managing physician made a clinical estimation of dehydration for each child, based on a standard clinical scale. Serum electrolytes were obtained in all children prior to intravenous hydration therapy. PLBW was calculated after recovery from acute dehydration by comparing the weight on presentation to the emergency department with the weight measured at a follow-up visit when the child was judged well. Children were classified according to PLBW into three groups which reflect the categories in a standard clinical scale: mild = PLBW < or = 5 (n = 50), moderate = PLBW 6-10 (n = 30), and severe = PLBW > 10 (n = 17). The physician's clinical estimate of dehydration compared to PLBW had a sensitivity of 74% (95% confidence interval (CI): 60-85) for mild dehydration, 33% (95% CI: 17-53) for moderate dehydration, and 70% (95% CI: 44-89) for severe dehydration. There was a significant difference in the mean serum bicarbonate concentrations (HCO3) between the PLBW groups (P < 0.01). The sensitivity of the HCO3 < 17 mEq/L in predicting PLBW was 77% (95% CI: 58-90) for PLBW 6-10, and 94% (95% CI: 71-100) for PLBW > 10. The combination of the clinical scale and the serum bicarbonate identified all 17 children with PLBW > 10 and 90% (27 of 30) children with PLBW 6-10. Our data suggest that physicians should not rely solely on clinical assessment to rule out severe dehydration in children, and that obtaining a serum bicarbonate may improve the accuracy of predicting serious dehydration.

Acute Disease↗

PubMed2003

Increased tonic activation of presynaptic metabotropic glutamate receptors in the rat supraoptic nucleus following chronic dehydration.

Chronic dehydration induces structural changes in the hypothalamic supraoptic nucleus (SON), including increased glutamate synapses and retraction of astroglial processes. We performed whole-cell recordings in acute hypothalamic slices to determine whether these changes increase tonic activation of presynaptic metabotropic glutamate receptors (mGluRs) by increasing ambient glutamate in the SON. Activation of presynaptic group III mGluRs caused a decrease in the frequency of miniature excitatory postsynaptic currents (mEPSCs) in SON neurones that was significantly attenuated in slices from dehydrated rats (-27.8 %) compared with untreated rats (-41.7 %), suggesting a higher basal occupancy of mGluRs by ambient glutamate during dehydration. Blocking group III mGluRs caused an increase in the frequency of mEPSCs that was significantly higher in slices from dehydrated rats (+42.8 %) than untreated rats (+31.4 %), suggesting greater tonic activation of presynaptic mGluRs by ambient glutamate during dehydration. Increasing ambient glutamate levels by inhibiting astrocyte glutamate uptake resulted in a decrease in mEPSC frequency due to increased activation of presynaptic mGluRs. This was attenuated in slices from dehydrated rats (-35.4 %) compared with slices from untreated rats (-48.8 %), suggesting diminished astrocytic glutamate uptake during dehydration. Immunochemical analyses revealed a robust expression of the GLT-1 transporter protein in the SON, which was diminished in SON punches from dehydrated rats compared with untreated controls. Thus, dehydration leads to increased tonic activation of presynaptic mGluRs on glutamate terminals, consistent with a decrease in glutamate buffering capacity. The resulting reduction in glutamate release probability may compensate for the increase in glutamate release sites that occurs during dehydration.

Animals↗

PubMed2000

Dehydration-induced vasopressin secretion in humans: involvement of the histaminergic system.

In rats, the hypothalamic neurotransmitter histamine participates in regulation of vasopressin secretion and seems to be of physiological importance, because blockade of the histaminergic system reduces dehydration-induced vasopressin secretion. We investigated whether histamine is also involved in regulation of vasopressin secretion during dehydration in humans. We found that 40 h of dehydration gradually increased plasma osmolality by 10 mosmol/kg and induced a fourfold increase in vasopressin levels. Pretreatment with the H(2)-receptor antagonists cimetidine or ranitidine significantly reduced the dehydration-induced increase in vasopressin levels approximately 40% after 34 and 37 h of dehydration, whereas this was not the case with the H(1)-receptor antagonist mepyramine. Dehydration reduced aldosterone secretion by approximately 50%. This effect of dehydration was reduced by both H(1)- and H(2)-receptor blockade after 16 and/or 34 h of dehydration. We conclude that vasopressin secretion in response to dehydration in humans is under the regulatory influence of histamine and that the effect seems to be mediated via H(2)-receptors. In addition, the regulation of aldosterone secretion during dehydration also seems to involve the histaminergic system via H(1) and H(2) receptors.

Adult↗

PubMed1984

Cardiovascular and respiratory responses to heat in dehydrated dogs.

The effect of dehydration on rectal temperature, respiratory frequency, upper respiratory evaporation, cardiac output, and common carotid blood flow was studied in large mongrel dogs at rest at ambient temperatures between 25 and 45 degrees C. Measurements were made in animals hydrated ad libitum and when they had been dehydrated by removal of drinking water. In hydrated animals, mean body weight was 31.6 +/- 1.7 (SE) kg and plasma osmolality was 296 +/- 2 mosmol/kg H2O. Dehydration decreased body weight to 28.2 +/- 1.5 kg and increased osmolality to 328 +/- 5 mosmol/kg H2O. At all ambient temperatures, every dehydrated animal had a higher rectal temperature, lower respiratory frequency, lower upper respiratory evaporation, lower cardiac output, and lower common carotid blood flow. Rectal temperature, measured in seven animals, was constant as ambient temperature was raised from 25 to 45 degrees C in both the hydrated and dehydrated state, but was elevated by 0.72 degrees C in dehydrated animals. Hypothalamic temperature, measured in two animals, was elevated less than rectal temperature when they were dehydrated. Upper respiratory evaporation and respiratory frequency, measured in seven animals, increased with increasing ambient temperature in both the hydrated and the dehydrated dogs, but were lower at every ambient temperature in dehydrated animals. Cardiac output, measured in five animals, was lower in dehydrated animals at every ambient temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1981

Effects of dehydration on thermoregulation in cats exposed to high ambient temperatures.

Measurements of evaporative water loss (EWL), metabolic rate (MR), body core temperature (Tc), and respiratory rate (RR) were made in nine hydrated cats exposed to several high ambient temperatures. Measurements were made in animals hydrated ad libitum and during progressive dehydration. At 43 and 40 degrees C, no significant change in EWL occurred during dehydration. At 38 and 35 degrees C, EWL in animals dehydrated for 4 days was reduced to about 50% of hydrated levels. Reductions in RR correlated highly with reduced EWL, suggesting that control of evaporation in dehydrated cats is dependent largely on control of RR. Significant elevations in Tc occurred in dehydrated animals at 43, 40, and 38 degrees C, and an insignificant upward trend was observed at 35 degrees C. Multiple linear regression analysis of data for EWL, Tc, and level of dehydration indicates that dehydration reduces the evaporative response to elevations in Tc and suggests that a change in the sensitivity of the thermoregulatory system is occurring. A similar analysis for MR, Tc, and level of dehydration shows that dehydration results in a lower MR at a given Tc. Changes in MR, corrected for body temperature, during dehydration are principally related at altered ventilatory energy expenditure. A model has been formed for estimating the metabolic cost of ventilation in the cat.

Animals↗

PubMed1997

Dehydration markedly impairs cardiovascular function in hyperthermic endurance athletes during exercise.

We identified the cardiovascular stress encountered by superimposing dehydration on hyperthermia during exercise in the heat and the mechanisms contributing to the dehydration-mediated stroke volume (SV) reduction. Fifteen endurance-trained cyclists [maximal O2 consumption (VO2max) = 4.5 l/min] exercised in the heat for 100-120 min and either became dehydrated by 4% body weight or remained euhydrated by drinking fluids. Measurements were made after they continued exercise at 71% VO2max for 30 min while 1) euhydrated with an esophageal temperature (T(es)) of 38.1-38.3 degrees C (control); 2) euhydrated and hyperthermic (39.3 degrees C); 3) dehydrated and hyperthermic with skin temperature (T(sk)) of 34 degrees C; 4) dehydrated with T(es) of 38.1 degrees C and T(sk) of 21 degrees C; and 5) condition 4 followed by restored blood volume. Compared with control, hyperthermia (1 degrees C T(es) increase) and dehydration (4% body weight loss) each separately lowered SV 7-8% (11 +/- 3 ml/beat; P < 0.05) and increased heart rate sufficiently to prevent significant declines in cardiac output. However, when dehydration was superimposed on hyperthermia, the reductions in SV were significantly (P < 0.05) greater (26 +/- 3 ml/beat), and cardiac output declined 13% (2.8 +/- 0.3 l/min). Furthermore, mean arterial pressure declined 5 +/- 2%, and systemic vascular resistance increased 10 +/- 3% (both P < 0.05). When hyperthermia was prevented, all of the decline in SV with dehydration was due to reduced blood volume (approximately 200 ml). These results demonstrate that the superimposition of dehydration on hyperthermia during exercise in the heat causes an inability to maintain cardiac output and blood pressure that makes the dehydrated athlete less able to cope with hyperthermia.

Adult↗

PubMed2005

Oral versus intravenous rehydration of moderately dehydrated children: a randomized, controlled trial.

BACKGROUND: Dehydration from viral gastroenteritis is a significant pediatric health problem. Oral rehydration therapy (ORT) is recommended as first-line therapy for both mildly and moderately dehydrated children; however, three quarters of pediatric emergency medicine physicians who are very familiar with the American Academy of Pediatrics recommendations for ORT still use intravenous fluid therapy (IVF) for moderately dehydrated children. OBJECTIVE: To test the hypothesis that the failure rate of ORT would not be >5% greater than the failure rate of IVF. Secondary hypotheses were that patients in the ORT group will (1) require less time initiating therapy, (2) show more improvement after 2 hours of therapy, (3) have fewer hospitalizations, and (4) prefer ORT for future episodes of dehydration. METHODS: A randomized, controlled clinical trial (noninferiority study design) was performed in the emergency department of an urban children's hospital from December 2001 to April 2003. Children 8 weeks to 3 years old were eligible if they were moderately dehydrated, based on a validated 10-point score, from viral gastroenteritis. Patients were randomized to receive either ORT or IVF during the 4-hour study. Treating physicians were masked and assessed all patients before randomization at 2 and 4 hours of therapy. Successful rehydration at 4 hours was defined as resolution of moderate dehydration, production of urine, weight gain, and the absence severe emesis (> or =5 mL/kg). RESULTS: Seventy-three patients were enrolled in the study: 36 were randomized to ORT and 37 were randomized to IVF. Baseline dehydration scores and the number of prior episodes of emesis and diarrhea were similar in the 2 groups. ORT demonstrated noninferiority for the main outcome measure and was found to be favorable with secondary outcomes. Half of both the ORT and IVF groups were rehydrated successfully at 4 hours (difference: -1.2%; 95% confidence interval [CI]: -24.0% to 21.6%). The time required to initiate therapy was less in the ORT group at 19.9 minutes from randomization, compared with 41.2 minutes for the IVF group (difference: -21.2 minutes; 95% CI: -10.3 to -32.1 minutes). There was no difference in the improvement of the dehydration score at 2 hours between the 2 groups (78.8% ORT vs 80% IVF; difference: -1.2%; 95% CI: -20.5% to 18%). Less than one third of the ORT group required hospitalization, whereas almost half of the IVF group was hospitalized (30.6% vs 48.7%, respectively; difference: -18.1%; 95% CI: -40.1% to 4.0%). Patients who received ORT were as likely as those who received IVF to prefer the same therapy for the next episode of gastroenteritis (61.3% vs 51.4%, respectively; difference: 9.9%; 95% CI: -14% to 33.7%). CONCLUSIONS: This trial demonstrated that ORT is as effective as IVF for rehydration of moderately dehydrated children due to gastroenteritis in the emergency department. ORT demonstrated noninferiority for successful rehydration at 4 hours and hospitalization rate. Additionally, therapy was initiated more quickly for ORT patients. ORT seems to be a preferred treatment option for patients with moderate dehydration from gastroenteritis.

Administration, Oral↗

PubMed1994

The burden and outcomes associated with dehydration among US elderly, 1991.

OBJECTIVES: Dehydration has been underappreciated as a cause of hospitalization and increased hospital-associated mortality in older people. This study used national data to analyze the burden and outcomes following hospitalizations with dehydration in the elderly. METHODS: Data from 1991 Medicare files were used to calculate rates of hospitalization with dehydration, to examine demographic characteristics and concomitant diagnoses associated with dehydration, and to analyze the contribution of dehydration to mortality. RESULTS: In 1991, 6.7% (731,695) of Medicare hospitalizations had dehydration listed as one of the five reported diagnoses, a rate of 236.2/10,000 elderly Medicare beneficiaries. In 1991, Medicare reimbursed over $446 million for hospitalizations with dehydration as the principal diagnosis. Older people, men, and Blacks had elevated risks for hospitalization with dehydration. Acute infections, such as pneumonia and urinary tract infections, were frequent concomitant diagnoses. About 50% of elderly Medicare beneficiaries hospitalized with dehydration died within a year of admission. CONCLUSIONS: Hospitalization of elderly people with dehydration is a serious and costly medical problem. Attention should be focused on understanding predisposing factors and devising strategies for prevention.

Age Factors↗

PubMedDate not supplied

[Diagnostic value of the determination of blood urea in dehydrated patients with and without central diabetes insipidus].

Dehydrated patients usually present with an elevated serum urea level, owing in part to increased renal reabsorption of urea mediated by antidiuretic hormone (ADH). This study was carried out in order to examine whether, during dehydration, the variations in the serum urea level could discriminate patients with central diabetes insipidus (CDI) from those with dehydration due to other causes. We studied retrospectively 27 episodes of dehydration in 23 patients with CDI and 14 episodes in 14 patients without CDI. The mean serum urea level was 2.9 mmol/L in the CDI group and 15.4 mmol/L in the patients without CDI (p less than 0.001) while the mean serum sodium level was 155 mmol/L in both groups. During dehydration, patients with CDI decreased their serum urea level (4.0 +/- 2.3 vs 2.9 +/- 1.5 mmol/L, p less than 0.001). In addition, a positive correlation was found in the patients with CDI between the magnitude of diuresis and the percentage decrease in the serum urea level compared with the level before dehydration (r = 0.70, p less than 0.001). A striking increase in the clearance of urea (0.8 +/- 1 vs 2.1 +/- 1 ml/s, P less than 0.01), which exceeded the creatinine clearance (1.8 +/- 0.5 ml/s), was observed during dehydration in the six patients in whom clearance studies were done. Therefore, our results suggest that serum urea values can be used to distinguish patients dehydrated because of CDI from those with hypertonic dehydration but without ADH deficiency and that during dehydration the reabsorption of urea is mainly dependent on the renal action of ADH.

Adult↗

PubMed1988

Low serum urea level in dehydrated patients with central diabetes insipidus.

Dehydrated patients usually present with an elevated serum urea level, owing in part to increased renal reabsorption of urea mediated by antidiuretic hormone (ADH). We carried out a study to examine whether, during dehydration, the variations in the serum urea level could discriminate patients with central diabetes insipidus (CDI) from those with dehydration not due to CDI. We studied retrospectively 27 episodes of dehydration in 23 patients with CDI and 14 episodes in 14 patients without CDI. The mean serum urea level was 2.9 mmol/L in the CDI group and 15.4 mmol/L in the patients without CDI (p less than 0.001); the mean serum sodium level was 155 mmol/L in both groups. All the patients with CDI had a sodium/urea ratio greater than 24.2, whereas the ratio was less than 21.7 in all the patients without CDI. In the patients with CDI a positive correlation was found between the magnitude of diuresis and the percentage decrease in the serum urea level compared with the level before dehydration (p less than 0.001). In the patients with CDI the serum urea level returned to the level before dehydration after the administration of vasopressin; a striking increase in the clearance of urea, which exceeded the creatinine clearance, was observed during dehydration in the three patients in whom clearance studies were done. The results suggest that serum urea values can be used to distinguish patients dehydrated because of CDI from those with hypertonic dehydration but without ADH deficiency and that during dehydration the net reabsorption of urea is dependent on the renal action of ADH.

Adult↗

PubMed2001

Dehydration behavior of nedocromil magnesium pentahydrate.

The dehydration of nedocromil magnesium (NM) pentahydrate proceeds in two steps, corresponding to the loss of four water molecules in the first step and one water molecule in the second step. The effects of temperature, particle size, sample weight, water vapor pressure and dehydration-rehydration cycle on both the kinetics and activation energy of the dehydration of NM pentahydrate were studied using isothermal TGA and temperature-ramp DSC analyzed by Kissinger's method. The dehydration kinetics for both steps are best described by the Avrami-Erofeev equations, suggesting a nucleation-controlled mechanism. The high activation energy for the second dehydration step indicates that the last water molecule, which is bonded both to a magnesium ion and to a carboxylate oxygen atom, is more 'tightly bound'. The activation energy decreased with increasing sample weight and decreasing particle size. The dehydration rate increased with decreasing water vapor pressure and with repetition of the dehydration-hydration cycle. Dynamic and isothermal PXRD, and 13C solid-state NMR were employed to provide an insight into the dehydration mechanism and the nature of solid-state phase transformation during the dehydration. Molecular modeling with Cerius(2) was used to visualize the crystal structure and to construct the molecular packing diagram. A correlation was noted between the dehydration behavior and the bonding environment of the water molecules in the crystal structure.

Chemical Phenomena↗

PubMed1999

Dehydration behavior of eprosartan mesylate dihydrate.

Eprosartan mesylate (SKF 108566-J; EM) is an antihypertensive agent approved for marketing in the USA. EM dihydrate was prepared by three methods, one of which included suspending the anhydrous drug in an aqueous solution of 1.0 M methanesulfonic acid to form a slurry, followed by filtration. The dehydration kinetics of EM dihydrate were derived by analyzing the fit of the isothermal thermogravimetric analytical (TGA) data to numerous kinetic models. EM dihydrate undergoes dehydration in two distinct steps, each involving the loss of 1 mol of water at 25-70 degrees C and 70-120 degrees C, respectively. Recrystallization of EM occurs at approximately 120-140 degrees C after dehydration to the anhydrous phase. This explanation is supported by variable temperature powder X-ray diffractometry. The mechanism of the dehydration reaction is complex, the dependence of the reaction rate on temperature varying as a function of the particles size. For the dihydrate of sieve fraction <125 microm, the kinetics of the first and second dehydration steps are consistent with the Avrami-Erofeev equation (A3, n = 1/3) over the temperature range studied, corresponding to three-dimensional growth of nuclei. In contrast, for the 125-180-microm and 180-250-microm sieve fractions, the kinetics are best described by the two-dimensional phase boundary reaction (R2) at a lower dehydration temperature (i.e., 28.3 degrees C), and by the Avrami-Erofeev equation (A3, n = 1/3) at a higher dehydration temperature (i.e., 93.7 degrees C). The activation energies (15-40 kcal/mol) and frequency factors of the dehydration of EM dihydrate were determined both by Arrhenius plots of the isothermal rates determined by TGA and by Kissinger plots of the nonisothermal differential scanning calorimetric data. Hot stage microscopy of single crystals of EM dihydrate showed random nucleation at the surface and dehydration with the growth of microcrystals along the needle a axis. Cerius(2) molecular modeling software showed the existence of water channels along the a axis and enabled the observed dehydration behavior of EM dihydrate crystals to be explained in terms of the bonding environment of water molecules in the crystal structure.

Acrylates↗

PubMed1995

Dehydration. Evaluation and management in older adults. Council on Scientific Affairs, American Medical Association.

OBJECTIVE: To review published literature regarding dehydration in older individuals and formulate a consensus on the evaluation and treatment of this unrecognized cause of hospitalizations, morbidity, and mortality. DATA SOURCES AND STUDY SELECTION: The literature concerning dehydration in the elderly population from MEDLINE was reviewed from 1976 through 1995. Search terms included dehydration, elderly, evaluation, hospitalization, and treatment. Particular emphasis was placed on articles describing original research leading to the development of new information on the evaluation and treatment of dehydration and review articles relating to the epidemiology, detection, treatment and health outcomes of this syndrome common in the geriatric population, including frail, institutionalized individuals. DATA EXTRACTION: Data contributing to a broad scientific understanding of dehydration were initially grouped according to topic areas of the physiology of normal aging, illness-associated clinical reports of dehydration in the elderly population, and diagnostic and therapeutic interventions. The authors developed a consensus based on the weight of evidence presented and the authors' experience in the field. CONCLUSIONS: Early diagnosis is sometimes difficult because the classical physical signs of dehydration may be absent or misleading in an older patient. Many different etiologies place the elderly at particular risk. In patients identified as being at risk for possible dehydration, an interdisciplinary care plan with regard to prevention of clinically significant dehydration is critical if maximum benefit is to result.

Advance Directives↗

PubMed2001

Garlic prevents ultrastructural alterations caused by dehydration in mouse cerebral microvessels.

Dehydration is known to significantly reduce both the time required for the first platelet aggregate and the time to full occlusion in photochemically-induced thrombosis, in vivo. Ultrastructural changes that contribute to such events remain unknown. Therefore, the effect of water deprivation for 24 hr, (as a model for dehydration) on the ultrastructure of mouse pial microvessels was investigated. The possible beneficial effect of garlic in preventing such ultrastructural changes was also investigated. Four groups of TO strain: control, control-garlic treated, dehydrated, and dehydrated-garlic treated male mice, 10/group, were used. Dehydration was induced by water deprivation for 24 hr. Garlic solution was i.p. injected at 0.1 ml/10g body weight. In urethane-anesthetized (2 mg/g, i.p.) mice, topical and transvessel bimodal fixation of pial microvessels was done with a phosphate buffered mixture of glutaraldehyde and paraformaldehyde, followed by a conventional electron microscopy procedure. Examination of control cerebral pial microvessels showed no evidence of cellular damage. Membranes of endothelial cells were intact. Within pial microvessels there was no evidence of platelet aggregation. Garlic treatments did not cause any ultrastructure abnormalities in control mice. Compared with control, dehydration caused the appearance of thrombi that consisted of platelet aggregates. Discoid platelets containing granules, spheroid degranulated platelets, and those with large pseudopodia were present in 80% of dehydrated mice. The venular endothelial surface of dehydrated mice revealed dilated profiles of endoplasmic reticulum and variously shaped vacuoles. Swelling of nuclear envelopes and mitochondrial distension were also present in dehydrated mice. Concomitant garlic treatment prevented most of these ultrastructural changes. These findings demonstrated the extent of damage to the pial microvessels in response to water deprivation and demonstrated the beneficial effect of garlic as a possible mean of protection against oncoming vascular pathology.

Animals↗