In Vivo Visualization and Quantification of Rat Laryngeal Blood Supply After Hydration Challenge.

OBJECTIVES: Systemic dehydration decreases total body blood volume; however, hemodynamic alterations at the level of local organs, such as the larynx, remain unclear. Here we sought to quantify superior thyroid artery (STA) blood flow after dehydration and rehydration using in vivo magnetic resonance angiography (MRA) and ultrasound imaging in a rat model. METHODS: Male Sprague-Dawley rats (N = 17) were included in this prospective, repeated measures design. Rats first underwent MRA to determine baseline STA cross-sectional area, followed by high-frequency in vivo ultrasound imaging to measure STA blood velocity at baseline. Next, rats were systemically dehydrated (water withholding), followed by rehydration (water ad-lib). Ultrasound imaging was repeated immediately after dehydration and following rehydration. The STA blood velocity and STA cross-sectional area were used to compute STA blood flow. Three rats served as temporal controls for ultrasound imaging. To determine if the challenges to hydration status affected the STA cross-sectional area, four rats underwent only MRA at baseline, dehydration, and rehydration. RESULTS: Systemic dehydration resulted in 10.5% average body weight loss. Rehydration resulted in average body weight gain of 10.9%. Statistically significant reductions were observed in STA mean blood flow rate after dehydration. Rehydration reversed these changes to pre-dehydration levels. No significant differences were observed in STA cross-sectional area with dehydration or rehydration. CONCLUSION: Systemic dehydration decreased blood flow in the superior thyroid artery. Rehydration restored blood flow in the STA. Change in hydration status did not alter the STA cross-sectional area. These preliminary findings demonstrate the feasibility of using ultrasound and MRA to quantify hemodynamic changes and visualize laryngeal blood vessels. LEVEL OF EVIDENCE: NA Laryngoscope, 134:779-785, 2024.

Point-of-care ultrasound to assess degree of dehydration in children: a systematic review with meta-analysis.

BACKGROUND: There is no perfect method to assess level of dehydration in children. There are studies with conflicting results, where point-of-care ultrasound (POCUS) measurement of diameter ratio of the inferior vena cava to the aorta (IVC/Ao) was used to predict degree of dehydration. OBJECTIVE: To systematically review the diagnostic accuracy of POCUS measurement of IVC/Ao ratio in predicting dehydration in children. METHODS: MEDLINE, EMBASE and Cochrane databases were searched. The primary outcome was the diagnostic accuracy of IVC/Ao ratio. The pooled sensitivity and specificity were calculated. Quality analysis was conducted using Quality Assessment of Diagnostic Accuracy Studies-2. RESULTS: Eleven studies (2679 patients) were included. The most numerous group (five studies) used percentage weight change as a reference standard; the pooled sensitivity, specificity of POCUS in this group were: 0.7 (95% CI: 0.67 to 0.73), I2: 82%; 0.53 (95% CI: 0.5 to 0.53), I2: 84%. In the remaining studies, different comparator tests were used: Clinical Dehydration Scale (two studies, 0.8 (95% CI: 0.72 to 0.86), I2: 0%; 0.56 (95% CI: 0.48 to 0.65), I2: 0%; clinical judgement (three studies, 0.78 (95% CI: 0.73 to 0.83), I2: 95%; 0.82 (95% CI: 0.77 to 0.86), I2: 93% and one study used the Dehydration: Assessing Kids Accurately score model. CONCLUSION: This systematic review and meta-analysis showed that POCUS has a moderate sensitivity and specificity for identifying dehydration in children. Its use as a complementary diagnostic tool could be promising but needs to be validated in randomised controlled trials. PROSPERO REGISTRATION NUMBER: CRD42022346166.

Association of Bun/Cr ratio-based dehydration status with infarct volumes and stroke severity in acute ischemic stroke.

BACKGROUND: Only a few clinical research had previously investigated the dehydration status to predict the evolution of the ischemic core. The aim of this study is to clarify the association between blood urea nitrogen (BUN)/creatinine (Cr)ratio-based dehydration and infarct volume measured using DWI (Diffusion-weighted imaging) at admission in patients with AIS (Acute Ischemic Stroke). METHODS: We retrospectively recruited a total of 203 consecutive patients who were hospitalized through emergency or outpatient services within 72 h of acute ischemic stroke onset between October 2015 and September 2019. Stroke severity was measured by assessing the National Institutes of Health Stroke Scale (NIHSS) on admission. Infarct volume was measured using DWI with MATLAB software. RESULTS: In this study, 203 patients who met the study criteria were enrolled. Patients in the dehydration group (Bun/Cr ratio>15) had a higher median NIHSS score (6(IQR:4-10) VS. 5(3-7); P = 0.0015)and larger DWI infarct volume (1.55 ml (IQR:0.51-6.79) VS. (0.37 ml (0.05-1.22); P < 0.001) on admission compared with patients in normal group. Further, a statistically significant correlation was found between DWI infarct volumes and NIHSS score with nonparametric Spearman rank correlation (r = 0.77; P < 0.001). The median NIHSS scores for the DWI infarct volumes quartiles were 3 ml (IQR, 2-4), 5 ml (4-7), 6 ml (5-8), and12 ml (8-17) from lowest to highest. However, the second quartile group did not show any significant correlation with the third quartile group (P = 0.4268). Multivariable linear and logistic regression analyses were used to test dehydration (Bun/Cr ratio>15), representing a predictor of infarct volume and stroke severity. CONCLUSION: Bun/Cr ratio-based dehydration is associated with larger volumes of ischemic tissue measured using DWI and worse neurological deficit assessed by the NIHSS score in acute ischemic stroke.

Ultrasound Measurements of Subcutaneous Fat Thickness Are Robust Against Hydration Changes.

Ultrasound is an appealing tool to assess body composition, combining the portability of a field method with the accuracy of a laboratory method. However, unlike other body composition methods, the effect of hydration status on validity is unknown. This study evaluated the impact of acute hydration changes on ultrasound measurements of subcutaneous fat thickness and estimates of body fat percentage. In a crossover design, 11 adults (27.1 ± 10.5 years) completed dehydration and hyperhydration trials to alter body mass by approximately ±2%. Dehydration was achieved via humid heat (40 °C, 60% relative humidity) with exercise, whereas hyperhydration was via ingestion of lightly salted water. Ultrasound measurements were taken at 11 body sites before and after each treatment. Participants lost 1.56 ± 0.58 kg (-2.0 ± 0.6%) during the dehydration trial and gained 0.90 ± 0.21 kg (1.2 ± 0.2%) during the hyperhydration trial even after urination. The sum of fat thicknesses as measured by ultrasound differed by <0.90 mm across trials (p = .588), and ultrasound estimates of body fat percentage differed by <0.5% body fat. Ultrasound measures of subcutaneous adipose tissue were unaffected by acute changes in hydration status by extents beyond which are rare and overtly self-correcting, suggesting that this method provides reliable and robust body composition results even when subjects are not euhydrated.

Diagnostic efficacy of bedside ultrasound to detect dehydration in older patients attending an emergency care unit.

BACKGROUND: The diagnosis of dehydration in older patients remains a challenge because clinical and laboratory signs are unspecific. The use of B­Mode ultrasound of the inferior vena cava is proposed to aid in the diagnosis but data concerning diagnostic efficacy of bedside ultrasound are lacking. METHODS: In this study 78 patients ≥65 years old referred to the emergency unit of a university hospital and identified as being dehydrated by applying clinical signs were compared with a reference of 121 patients. The diameter of the inferior vena cava (IVC) was assessed by ultrasound while compressing the IVC during an inspiratory maneuver and the minimum and maximum diameter in M­Mode. RESULTS: Significant differences were found concerning compressibility, variability of the diameter assessed by M­Mode and the diameter during an inspiratory maneuver of the IVC (<0.001); however, a receiver operator characteristics (ROC) showed only moderate values for diagnostic efficacy for all these parameters where the best result was found for the inspiratory maneuver (Area under the curve [AUC] = 0.73). To reach a specificity of 0.8 to diagnose dehydration, a cut-off value of ≤0.4 cm for IVC diameter was suitable. CONCLUSION: Ultrasound of the IVC can easily be applied in a bedside setting and may be helpful in identifying dehydration in older patients; however, this remains challenging and a synopsis covering clinical and technical data is indispensable.

In Vivo Magnetic Resonance Imaging of the Rat Vocal Folds After Systemic Dehydration and Rehydration.

Objective Consuming less water (systemic dehydration) has long been thought to dehydrate the vocal folds. An in vivo, repeated measures study tested the assumption that systemic dehydration causes vocal fold dehydration. Proton density (PD)-weighted magnetic resonance imaging (MRI) of rat vocal folds was employed to investigate (a) whether varying magnitudes of systemic dehydration would dehydrate the vocal folds and (b) whether systemic rehydration would rehydrate the vocal folds. Method Male (n = 25) and female (n = 14) Sprague Dawley rats were imaged with 7T MRI, and normalized PD-weighted signal intensities were obtained at predehydration, following dehydration, and following rehydration. Animals were dehydrated to 1 of 3 levels by water withholding to induce body weight loss: mild (< 6% body weight loss), moderate (6%-10% body weight loss), and marked (> 10% body weight loss). Results There was a significant decrease in vocal fold signal intensities after moderate and marked dehydration (p < .0167). Rehydration increased the normalized signal intensity to predehydration levels for only the moderate group (p < .0167). Normalized signal intensity did not significantly change after mild dehydration or when the mildly dehydrated animals were rehydrated. Additionally, there were no significant differences in PD-weighted MRI normalized signal intensity between male and female rats (p > .05). Conclusion This study provides evidence supporting clinical voice recommendations for rehydration by increasing water intake after an acute, moderate systemic dehydration event. However, acute systemic dehydration of mild levels did not dehydrate the vocal folds as observed by PD-weighted MRI. Future programmatic research will focus on chronic, recurring systemic dehydration.

Dehydration assessment via a portable, single sided magnetic resonance sensor.

PURPOSE: Undiagnosed dehydration compromises health outcomes across many populations. Existing dehydration diagnostics require invasive bodily fluid sampling or are easily confounded by fluid and electrolyte intake, environment, and physical activity limiting widespread adoption. We present a portable MR sensor designed to measure intramuscular fluid shifts to identify volume depletion. METHODS: Fluid loss is induced via a mouse model of thermal dehydration (37°C; 15-20% relative humidity). We demonstrate quantification of fluid loss induced by hyperosmotic dehydration with multicomponent T2 relaxometry using both a benchtop NMR system and MRI localized to skeletal muscle tissue. We then describe a miniaturized (~1000 cm3 ) portable (~4 kg) MR sensor (0.28 T) designed to identify dehydration-induced fluid loss. T2 relaxometry measurements were performed using a Carr-Purcell-Meiboom-Gill pulse sequence in ~4 min. RESULTS: T2 values from the portable MR sensor exhibited strong (R2 = 0.996) agreement with benchtop NMR spectrometer. Thermal dehydration induced weight loss of 4 to 11% over 5 to 10 h. Fluid loss induced by thermal dehydration was accurately identified via whole-animal NMR and skeletal muscle. The portable MR sensor accurately identified dehydration via multicomponent T2 relaxometry. CONCLUSION: Performing multicomponent T2 relaxometry localized to the skeletal muscle with a miniaturized MR sensor provides a noninvasive, physiologically relevant measure of dehydration induced fluid loss in a mouse model. This approach offers sensor portability, reduced system complexity, fully automated operation, and low cost compared with MRI. This approach may serve as a versatile and portable point of care technique for dehydration monitoring.

Use of point-of-care ultrasound for the assessment of intravascular volume in five rural New Zealand hospitals.

INTRODUCTION: Measuring the diameter of the inferior vena cava (IVC) or the height of the jugular venous pressure (JVP) with point-of-care ultrasound (POCUS) is a practical alternative method for estimating a patient's intravascular volume in the rural setting. This study aims to determine whether or not POCUS of the IVC or JVP generates additional useful clinical information over and above routine physical examination in this context. METHODS: Twenty generalist physicians, working in five New Zealand rural hospitals, recorded their estimation of a patient's intravascular volume based on physical examination and then again after performing POCUS of the IVC or JVP, using a visual scale from 1 to 11. RESULTS: Data were available for 150 assessments. There was an only moderate agreement between the pre- and post-test findings (Spearman's correlation coefficient = 0.46). In 28% (42/150) of cases, the difference was four or more points on the scale, and therefore, had the potential to be clinically significant. CONCLUSION: In the rural context, POCUS provides new information that frequently alters the clinician's estimation of a patient's intravascular volume.

Résumé Introduction: La mesure du diamètre de la veine cave inférieure ou de la hauteur de la pression veineuse jugulaire à l'aide de l'échographie au point de service est une méthode pratique pour estimer le volume intravasculaire d'un patient en région rurale. Cette étude vise à déterminer si oui ou non l'échographie au point de service de la veine cave inférieure ou de la pression veineuse jugulaire génère un surcroît d'information clinique utile par rapport à l'examen physique de routine dans ce contexte. Méthodologie: Vingt médecins généralistes de 5 hôpitaux des régions rurales de la Nouvelle-Zélande ont noté sur une échelle visuelle de 1 à 11 leur estimation du volume intravasculaire des patients basée sur l'examen physique, puis après une échographie au point de service de la veine cave inférieure ou de la pression veineuse jugulaire. Résultats: Des données se rapportant à 150 évaluations étaient disponibles. La concordance entre les résultats d'avant le test et d'après le test n'était que modérée (coefficient de corrélation de Spearman = 0,46). Dans 28 % (42/150) des cas, la différence était de quatre points ou plus sur l'échelle et avait donc le potentiel d'être cliniquement significative. Conclusion: En contexte rural, l'échographie au point de service fournit de nouveaux renseignements qui altèrent fréquemment l'estimation du volume intravasculaire par le clinicien. Mots-clés: Échographie, évaluation du volume, point de service, rural, veine cave inférieure.

Vomiting and Dehydration in a 2-Year-Old.

A 2-year-old girl with a past medical history of cutaneous mastocytosis and eczema presented with 1 day of yellow-green, nonbloody vomiting, bradycardia, and listlessness. She was evaluated by her pediatrician and sent to the emergency department because of concern for dehydration. In the emergency department, she improved with fluid rehydration but still had decreased energy and bradycardia. Her electrocardiogram revealed sinus bradycardia, and laboratory results did not reveal any electrolyte abnormalities. Glucose levels were normal. An abdominal radiograph revealed a moderate-to-large stool burden, and the results of a computed tomography scan of the head were normal. An abdominal ultrasound was obtained to evaluate for intussusception. The ultrasound revealed a blind-ending tubular structure in the right-lower quadrant with adjacent free fluid, which was concerning for appendicitis. The patient was admitted to the surgical service for further management and was taken to the operating room, where a definitive diagnosis was made.

The effect of voluntary fasting and dehydration on posterior ocular structures.

PURPOSE: Islamic Ramadan is the month of fasting, in which intake of food and drink is restricted from sunrise until sunset. The objective of the present study was to find out the effects of religious fasting on posterior ocular structures. MATERIALS AND METHODS: In this prospective study, 34 eyes of 34 healthy volunteers with a mean age of 34.09 ± 7.20 years were enrolled. Volunteers with any systemic disorder and eyes with pathology or previous surgery were excluded. One week before Ramadan (non-fasting period) and during Ramadan (fasting period) at the same hours (at 08:00 and 16:00 h), choroidal, macular, and retinal nerve fibre layer (RNFL) thicknesses were measured by spectral domain optical coherence tomography. Results were compared using paired sample t-test, and a p value <0.05 was accepted as statistically significant. RESULTS: The comparison of 16:00-h measurements significantly revealed lower values during fasting period when compared non-fasting period for choroidal thickness (non-fasting and fasting, respectively; subfoveal: 299.26 ± 41.3 and 280.03 ± 38.75 p < 0.001, nasal: 246.09 ± 53.59 and 227.06 ± 53.82 p < 0.001, and temporal: 273.56 ± 42.68 and 257.44 ± 45.06 p = 0.001) and paracentral macular thickness (superior: p = 0.002, inferior: p = 0.010, temporal: p = 0.013, and nasal: p = 0.016). By contrast, no significant differences were found in the central macular thickness between the fasting and non-fasting periods (p = 0.735). Also, no statistically significant difference was noted for RNFL thickness at the different periods and time points. CONCLUSION: Our results reveal that Islamic religious fasting is associated with statistically significant alterations in choroidal and paracentral macular thickness in healthy volunteers. However, more detailed investigations should be designed to evaluate whether fasting has a pivotal influence on pathological conditions.

Magnetic resonance imaging quantification of dehydration and rehydration in vocal fold tissue layers.

Clinicians commonly recommend increased hydration to patients with voice disorders. However, effects on clinical voice outcome measures have been inconsistent. Hydration-induced change within different layers of vocal fold tissue is currently unknown. Magnetic Resonance Imaging (MRI) is a promising method of noninvasively measuring water content in vocal folds. We sought to image and quantify changes in water content within vocal fold mucosa and thyroarytenoid muscle after dehydration and rehydration. Excised porcine larynges were imaged using proton density (PD) weighted MRI (1) at baseline and (2) after immersion in one of five hypertonic, isotonic, or hypotonic solutions or in dry air. Larynges dehydrated in hypertonic solutions or dry air were rehydrated and imaged a third time. Scans revealed fluid-rich vocal fold mucosa that was distinct from muscle at baseline. Baseline normalized signal intensity in mucosa and muscle varied by left vs. right vocal fold (p < 0.01) and by anterior, middle, or posterior location (p < 0.0001). Intensity changes in the middle third of vocal fold mucosa differed by solution after immersion (p < 0.01). Hypertonic solutions dehydrated the middle third of mucosa by over 30% (p < 0.001). No difference from baseline was found in anterior or posterior mucosa or in muscle after immersion. No association was found between intensity change in mucosa and muscle after immersion. After rehydration, intensity did not differ by solution in any tissue, and was not different from baseline, but post-rehydration intensity was correlated with post-immersion intensity in both mucosa and muscle (p < 0.05), suggesting that degree of change in vocal fold water content induced by hypertonic solutions ex vivo persists after rehydration. These results indicate that PD-MRI can be used to visualize large mammalian vocal fold tissue layers and to quantify changes in water content within vocal fold mucosa and thyroarytenoid muscle independently.

Exercise-heat stress with and without water replacement alters brain structures and impairs visuomotor performance.

Effects of exercise-heat stress with and without water replacement on brain structure and visuomotor performance were examined. Thirteen healthy adults (23.6 ± 4.2 years) completed counterbalanced 150 min trials of exercise-heat stress (45°C, 15% RH) with water replacement (EHS) or without (~3% body mass loss; EHS-DEH) compared to seated rest (CON). Anatomical scans and fMRI Blood-Oxygen-Level-Dependent responses during a visuomotor pacing task were evaluated. Accuracy decreased (P < 0.05) despite water replacement during EHS (-8.2 ± 6.8% vs. CON) but further degraded with EHS-DEH (-8.3 ± 6.4% vs. EHS and -16.5 ± 10.2% vs. CON). Relative to CON, EHS elicited opposing volumetric changes (P < 0.05) in brain ventricles (-5.3 ± 1.7%) and periventricular structures (cerebellum: 1.5 ± 0.8%) compared to EHS-DEH (ventricles: 6.8 ± 3.4, cerebellum: -0.7 ± 0.7; thalamus: -2.7 ± 1.3%). Changes in plasma osmolality (EHS: -3.0 ± 2.1; EHS-DEH: 9.3 ± 2.1 mOsm/kg) were related (P < 0.05) to thalamus (r = -0.45) and cerebellum volume (r = -0.61) which, in turn, were related (P < 0.05) to lateral (r = -0.41) and fourth ventricle volume (r = -0.67) changes, respectively; but, there were no associations (P > 0.50) between structural changes and visuomotor accuracy. EHS-DEH increased neural activation (P < 0.05) within motor and visual areas versus EHS and CON. Brain structural changes are related to bidirectional plasma osmolality perturbations resulting from exercise-heat stress (with and without water replacement), but do not explain visuomotor impairments. Negative impacts of exercise-heat stress on visuomotor tasks are further exacerbated by dehydration.

Non-invasive Assessment of Significant Dehydration in Infants Using the Inferior Vena Cava to Aortic Ratio: Is it Useful?

OBJECTIVES: The aim of the study was to assess the accuracy of the inferior vena cava to aorta (IVC/Ao) diameter ratio for predicting significant dehydration in infants relative to their percentage weight change and the clinical diagnosis by a physician. METHODS: A prospective observational study was performed on 200 infants presented with acute diarrhea and clinical evidence of significant dehydration whose treatment required intravenous (IV) fluids as determined by the attending physician at the pediatric emergency department of Tanta University Hospital. Weight was recorded at admission before IV fluid treatment and at hospital discharge. The percentage of dehydration was determined using the following formula: (discharge weight - admission weight)/discharge weight × 100%. Patients with a percentage weight change of <5% were considered to be nonsignificantly dehydrated, whereas patients with a percentage weight change >5% were considered significantly dehydrated. The IVC/Ao diameter ratio was measured for all patients before IV fluid rehydration and again at discharge. RESULTS: Only 134 out of 200 dehydrated infants were found to be significantly dehydrated using the gold standard, percentage weight change. Receiver operating characteristics (ROC) curve analysis of the prehydration IVC/Ao ratio showed a sensitivity of 82%, a specificity of 91%, and an accuracy of 87% for predicting significant dehydration in infants at a cut-off point of less than 0.75. In contrast, physician clinical diagnosis showed a sensitivity of 70%, a specificity of 63%, and an accuracy of 73%. CONCLUSIONS: The IVC/Ao diameter ratio can be used as a reliable predictor for diagnosing significant dehydration in infants.

Proton density-weighted laryngeal magnetic resonance imaging in systemically dehydrated rats.

OBJECTIVES/HYPOTHESIS: Dehydrated vocal folds are inefficient sound generators. Although systemic dehydration of the body is believed to induce vocal fold dehydration, this causative relationship has not been demonstrated in vivo. Here we investigate the feasibility of using in vivo proton density (PD)-weighted magnetic resonance imaging (MRI) to demonstrate hydration changes in vocal fold tissue following systemic dehydration in rats. STUDY DESIGN: Animal study. METHODS: Sprague-Dawley rats (n = 10) were imaged at baseline and following a 10% reduction in body weight secondary to withholding water. In vivo, high-field (7 T), PD-weighted MRI was used to successfully resolve vocal fold and salivary gland tissue structures. RESULTS: Normalized signal intensities within the vocal fold decreased postdehydration by an average of 11.38% ± 3.95% (mean ± standard error of the mean [SEM], P = .0098) as compared to predehydration levels. The salivary glands experienced a similar decrease in normalized signal intensity by an average of 10.74% ± 4.14% (mean ± SEM, P = .0195) following dehydration. The correlation coefficient (percent change from dehydration) between vocal folds and salivary glands was 0.7145 (P = .0202). CONCLUSIONS: Ten percent systemic dehydration induced vocal fold dehydration as assessed by PD-weighted MRI. Changes in the hydration state of vocal fold tissue were highly correlated with that of the salivary glands in dehydrated rats in vivo. These preliminary findings demonstrate the feasibility of using PD-weighted MRI to quantify hydration states of the vocal folds and lay the foundation for further studies that explore more routine and realistic magnitudes of systemic dehydration and rehydration. LEVEL OF EVIDENCE: NA. Laryngoscope, 128:E222-E227, 2018.

The effect of hydration status on the measurement of lean tissue mass by dual-energy X-ray absorptiometry.

PURPOSE: Athletes cycle between exercise and recovery. Exercise invokes changes in total body water from thermal sweating, muscle and hepatic glycogen depletion and metabolic water loss. Recovery from exercise results in rehydration, substrate repletion, and possible glycogen supercompensation. Such changes may corrupt the measurement of hydrated tissues, such as lean tissue mass (LTM), by dual-energy X-ray absorptiometry (DXA). The purpose of this study was to determine the effect of exercise and thermal dehydration and subsequent glycogen supercompensation on DXA-based measurement of body composition. METHODS: Twelve active adult (18-29 years) males exercised at 70% VO2max on a cycle ergometer in a thermal environment (30 °C) to induce a 2.5% reduction in body mass. Participants subsequently underwent a glycogen supercompensation phase, whereby a high carbohydrate diet (8-12 g/kg body mass/day) was consumed for a 48-h period. Whole-body DXA measurement was performed at baseline, following exercise and supercompensation. RESULTS: Following exercise, mean body mass decreased by -1.93 kg (95% CI -2.3, -1.5), while total LTM decreased by -1.69 kg (-2.4, -1.0). Supercompensation induced a mean body mass increase of 2.53 kg (2.0, 3.1) and a total LTM increase of 2.36 kg (1.8, 2.9). No change in total fat mass or bone mineral content was observed at any timepoint. CONCLUSIONS: Training regimens that typically induce dehydration and nutrition regimens that involve carbohydrate loading can result in apparent changes to LTM measurement by DXA. Accurate measurement of LTM in athletes requires strict observation of hydration and glycogen status to prevent manipulation of results.

The diagnostic utility of sonographic carotid flow time in determining volume responsiveness.

OBJECTIVE: We aimed to predict volume responsiveness and to assess the diagnostic accuracy of carotid flow time (FTc) with the change in hydration status before and after a passive leg raise (PLR) maneuver. METHODS: Participants who presented at a community health fair in a dehydrated state following a prolonged fast while observing the month of Ramadan were recruited. Sonographic FTc measurements were obtained in the semi-Fowler position and after a PLR maneuver while participants were in a fasting state and repeated approximately 3 hours after breaking their fast. RESULTS: In total, 123 participants with mean age of 47±14 years, 55% male, were enrolled. Participants had fasted for an average of 16.9 hours and consumed an average of 933 mL between the 2 ultrasound measurements. Mean FTc values were significantly lower in the fasting state compared with the nonfasting state (312±22 vs 345±25milliseconds, P value < .001). Relative increases in FTc following a PLR maneuver demonstrated strong discrimination of volume status (area under the receiver operating curve: 0.86 [95% confidence interval, 0.81-0.91]). CONCLUSIONS: The use of point-of-care ultrasound to measure FTc may provide a noninvasive alternative to determine fluid status. Percentage change in FTc of ≥5% provides a reliable diagnostic accuracy for predicting fluid status.

Overdrinking, swallowing inhibition, and regional brain responses prior to swallowing.

In humans, drinking replenishes fluid loss and satiates the sensation of thirst that accompanies dehydration. Typically, the volume of water drunk in response to thirst matches the deficit. Exactly how this accurate metering is achieved is unknown; recent evidence implicates swallowing inhibition as a potential factor. Using fMRI, this study investigated whether swallowing inhibition is present after more water has been drunk than is necessary to restore fluid balance within the body. This proposal was tested using ratings of swallowing effort and measuring regional brain responses as participants prepared to swallow small volumes of liquid while they were thirsty and after they had overdrunk. Effort ratings provided unequivocal support for swallowing inhibition, with a threefold increase in effort after overdrinking, whereas addition of 8% (wt/vol) sucrose to water had minimal effect on effort before or after overdrinking. Regional brain responses when participants prepared to swallow showed increases in the motor cortex, prefrontal cortices, posterior parietal cortex, striatum, and thalamus after overdrinking, relative to thirst. Ratings of swallowing effort were correlated with activity in the right prefrontal cortex and pontine regions in the brainstem; no brain regions showed correlated activity with pleasantness ratings. These findings are all consistent with the presence of swallowing inhibition after excess water has been drunk. We conclude that swallowing inhibition is an important mechanism in the overall regulation of fluid intake in humans.

Accuracy of the caval index and the expiratory diameter of the inferior vena cava for the diagnosis of dehydration in elderly.

PURPOSE: Dehydration is a very common condition among elderly people. Till date there is not yet a fast and easy method to determine a state of dehydration in the emergency department. In the literature there are some exploratory studies that have tried to establish the relationship between some widely used laboratory values and ultrasound for the purpose of diagnosing dehydration. The primary aim of this study is to verify the correlation between two measures derived by ultrasound (caval index and expiratory diameter of inferior vena cava) and blood urea nitrogen (BUN)/creatinine ratio. The relationship between vital signs and BUN/creatinine ratio has also been explored. METHODS: An observational cohort study of patients aged 70 years or more, all examined in our ED. The population was divided on the basis of the BUN/creatinine ratio greater or lower than 20. RESULTS: A total of 270 patients have been considered. No vital sign correlated with an increased BUN/creatinine ratio. Both the diameter of the inferior vena cava in expiratory and the percentage of its collapsibility in inspiratory (caval index) have revealed a correlation with a BUN/creatinine ratio greater than 20. Areas under the curve are, respectively, 76 % (95 % CI 70-82) and 80 % (95 % CI 75-86). Sensitivity, specificity, positive predictive value and negative predictive value are, respectively, 85.5 % (95 % CI 79.4-90.4); 100 % (95 % CI 97-100); 100 % (95 % CI 97.5-100); 82.9 % (95 % CI 75.9-88.7) and 99.3 % (95 % CI 96.3-99.9); 100 % (95 % CI 97-100); 100 % (95 % CI 97.5-100); 99.2 % (95 % CI 95.6-99.9). CONCLUSIONS: Ultrasound has proved to be useful to diagnose dehydration in elderly people while in the emergency department. Vice versa the vital signs have shown to be unrelated to the hydration state of elderly patients.

Sonographic aorta/IVC cross-sectional area index for evaluation of dehydration in children.

OBJECTIVE: Current studies have not found sufficient evidence to encourage the use of ultrasound for assessing dehydration in children. We introduce a new sonographic parameter, the "aorta/inferior vena cava (IVC) cross-sectional area index" (Ao/IVCA) measured just inferior to the xiphoid process, for the effective evaluation of dehydration in children. METHODS: This is a prospective, observational study. We enrolled children who presented to the pediatric emergency department (PED) between May 2014 and January 2015. We measured the maximum diameter of the aorta from inner wall to inner wall, and the long and short axis diameters of IVC using a convex array transducer. Ao/IVCA was calculated and compared with aorta/IVC maximal diameter index (Ao/IVCD) and the clinical dehydration scale (CDS). RESULTS: A total of 34 children were enrolled. We found a statistically significant correlation between Ao/IVCA and CDS (R(2) = 0.30; P <.001). Ao/IVCD did not correlate significantly with CDS (R(2) = 0.08; P =.11). The ability of Ao/IVCA and Ao/IVCD to predict CDS ≥1 was assessed using the receiver operating characteristic analysis. The area under the receiver operating characteristic curve for Ao/IVCA was larger than that for Ao/IVCD (0.87 vs 0.75, P= .04). The cut-off value of Ao/IVCA that yielded the maximum value of Youden index was 1.81 (sensitivity: 72%, specificity: 89%). CONCLUSIONS: Ao/IVCA might be a promising index for the assessment of dehydration. The diagnostic performance of Ao/IVCA for dehydration might be higher than that of the method that uses the maximum diameter of IVC and the aorta.

Accuracy of Inferior Vena Cava Ultrasound for Predicting Dehydration in Children with Acute Diarrhea in Resource-Limited Settings.

INTRODUCTION: Although dehydration from diarrhea is a leading cause of morbidity and mortality in children under five, existing methods of assessing dehydration status in children have limited accuracy. OBJECTIVE: To assess the accuracy of point-of-care ultrasound measurement of the aorta-to-IVC ratio as a predictor of dehydration in children. METHODS: A prospective cohort study of children under five years with acute diarrhea was conducted in the rehydration unit of the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b). Ultrasound measurements of aorta-to-IVC ratio and dehydrated weight were obtained on patient arrival. Percent weight change was monitored during rehydration to classify children as having "some dehydration" with weight change 3-9% or "severe dehydration" with weight change > 9%. Logistic regression analysis and Receiver-Operator Characteristic (ROC) curves were used to evaluate the accuracy of aorta-to-IVC ratio as a predictor of dehydration severity. RESULTS: 850 children were enrolled, of which 771 were included in the final analysis. Aorta to IVC ratio was a significant predictor of the percent dehydration in children with acute diarrhea, with each 1-point increase in the aorta to IVC ratio predicting a 1.1% increase in the percent dehydration of the child. However, the area under the ROC curve (0.60), sensitivity (67%), and specificity (49%), for predicting severe dehydration were all poor. CONCLUSIONS: Point-of-care ultrasound of the aorta-to-IVC ratio was statistically associated with volume status, but was not accurate enough to be used as an independent screening tool for dehydration in children under five years presenting with acute diarrhea in a resource-limited setting.