Effect of heat exposure on dehydration and kidney function among sea salt workers in Thailand

Background. Excessive heat exposure and dehydration among agricultural workers have been reported to reduce kidney function and lead to chronic kidney disease of unknown etiology (CKDu). Objective. This cross-sectional study aimed to assess heat exposure, factors related to dehydration and the relationship between dehydration and biomarkers of kidney function among sea salt workers in Thailand. Material and methods. Wet bulb globe temperature (WBGT) was used at the time workers started work outdoors on salt farms. Urine-specific gravity, urine osmolarity, and serum creatinine were collected from 50 workers after work. Results. The results showed that more than 50% of the participants were dehydrated after work. The maximum hours spent working per day was 10. The average water intake was 1.51 L. Urine specific gravity was highly significant correlated with urine osmolality (rs = 0.400, p<0.01), and urine osmolality was significantly correlated with the estimated glomerular filtration rate (eGFR) (rs = 0.349, p<0.05). In bivariate analysis adjusted for age, sex, and current alcohol consumption, we found that a WBGTTWA ≥ 30°C (OR = 0.08, 95% CI = 0.01-0.44, p = 0.003) and hours spent working (OR=2.22, 95% CI = 1.42-3.47, p <0.001) were independently associated with dehydration. This suggests that workers should increase their time spent on breaks and increase water consumption. Conclusions. Educational program on heat exposure and heat-related illness prevention strategies should be provided

The simple, conventional markers of fatigue - variations in neuromuscular performance, creatine kinase and hydration status in elite soccer players over a season.

Background and Purpose: Fixture congestion, game-intensities and limited recovery negatively influence physical/physiological responses during a competitive soccer season. Therefore, the aim of the investigation was to examine weekly alterations in neuromuscular performance markers, creatine kinase and hydration in elite soccer players throughout a season. Study Design: Longitudinal Observational Study. Methods: Sixteen male professional soccer players competing in the English Football League Championship were assessed over the course of a season. All players provided a urine sample, a blood sample to assess creatine-kinase concentration and performed a countermovement jump test at the start of the season, in-season, pre-and post-match over 38 weeks. Results: Jump height was the most common marker of performance to be significantly reduced in-season compared to baseline (-5.4 to -11.3%, P<0.05) with 45.2% of the time-points affected. Measures of FT:CT (-7.5 to -12.4%) and AP (-9.4 to -11.5%), also showed significant deteriorations throughout the season compared to baseline (P<0.05) at several time-points. Max force (MF) significantly increased in-season (+5.1 to 7.0%) in 20% of the observed time-points compared to baseline. CK concentration significantly increased during 19% of the time-points (P<0.05; 62 to 159%). Urine osmolality demonstrated significant differences in season compared to baseline, but none to levels of dehydration. Conclusion: Monitoring elite soccer players over the course of a competitive season shows alterations in neuromuscular performance and hydration status. These data suggest that assessing counter-movement jump performance may be a useful marker for monitoring responses to training/competition, while creatine-kinase and hydration status may be limited.

Prescribed Water Intake in Autosomal Dominant Polycystic Kidney Disease

In patients with autosomal dominant polycystic kidney disease (ADPKD), drinking more water could potentially reduce urine osmolality and suppress arginine vasopressin release and decrease the rate of kidney cyst growth and its associated organ dysfunction. In a 3-year trial, adults with ADPKD randomized to drink more water so as to lower urine osmolality did not have slower kidney growth than did a group who drank water as they wished.

Relationship between Urine Creatinine and Urine Osmolality in Spot Samples among Men and Women in the Danish Diet Cancer and Health Cohort

Assays of urine biomarkers often use urine creatinine to account for urinary dilution, even though creatinine levels are influenced by underlying physiology and muscle catabolism. Urine osmolality—a measure of dissolved particles including ions, glucose, and urea—is thought to provide a more robust marker of urinary dilution but is seldom measured. The relationship between urine osmolality and creatinine is not well understood. We calculated correlation coefficients between urine creatinine and osmolality among 1375 members of a subcohort of the Danish Diet, Cancer, and Health Cohort, and within different subgroups. We used linear regression to relate creatinine with osmolality, and a lasso selection procedure to identify other variables that explain remaining variability in osmolality. Spearman correlation between urine creatinine and osmolality was strong overall (ρ = 0.90; 95% CI: 0.89–0.91) and in most subgroups. Linear regression showed that urine creatinine explained 60% of the variability in urine osmolality, with another 9% explained by urine thallium (Tl), cesium (Cs), and strontium (Sr). Urinary creatinine and osmolality are strongly correlated, although urine Tl, Cs, and Sr might help supplement urine creatinine for purposes of urine dilution adjustment when osmolality is not available.

The syndrome of inappropriate antidiuresis after vaccination against COVID-19: case report

Background The Syndrome of Inappropriate Antidiuresis (SIADH) has been described to be associated with a multitude of conditions and medications, including the severe acute respiratory syndrome coronavirus 2. We describe the case of a patient with newly diagnosed and symptomatic SIADH after receiving the second COVID-19 vaccination not explained otherwise. Case presentation A 79-year-old male person was admitted to the emergency department due to a worsening of his general health state expressed by weakness, fatigue and anorexia. Vital signs and clinical findings were normal, in particular the patient was considered to be euvolemic. Laboratory investigations revealed a serum sodium of 117 mmol/L, a serum osmolality of 241 mosm/kg and a urea of 1.2 mmol/L with creatinine within normal range. Urine chemistry showed a urine osmolality of 412 mosm/kg and urine sodium of 110 mmol/L. TSH, C-reactive protein, and basal cortisol levels were normal. Under therapy with balanced crystalloid fluids, hyponatremia worsened and in absence of diuretic medications, diagnosis of SIADH was made. Since fluid restriction was not sufficiently effective, oral urea was administered. Under this therapy regimen hyponatremia resolved. Conclusions Local as well as systemic reactions have been described for the new mRNA-based vaccines including pain and fever. Therefore, it is imaginable that the vaccine might trigger SIADH in some patients.

Hypohydration produced by high-intensity intermittent running increases biomarkers of renal injury in males

Purpose Whilst there is evidence to suggest that hypohydration caused by physical work in the heat increases renal injury, whether this is the case during exercise in temperate conditions remains unknown. This study investigated the effect of manipulating hydration status during high-intensity intermittent running on biomarkers of renal injury. Methods After familiarisation, 14 males (age: 33 ± 7 years; V̇O2peak: 57.1 ± 8.6 ml/kg/min; mean ± SD) completed 2 trials in a randomised cross-over design, each involving 6, 15 min blocks of shuttle running (modified Loughborough Intermittent Shuttle Test protocol) in temperate conditions (22.3 ± 1.0 °C; 47.9 ± 12.9% relative humidity). During exercise, subjects consumed either a volume of water equal to 90% of sweat losses (EU) or 75 mL water (HYP). Body mass, blood and urine samples were taken pre-exercise (baseline/pre), 30 min post-exercise (post) and 24 h post-baseline (24 h). Results Post-exercise, body mass loss, serum osmolality and urine osmolality were greater in HYP than EU (P ≤ 0.024). Osmolality-corrected urinary kidney injury molecule-1 (uKIM-1) concentrations were increased post-exercise (P ≤ 0.048), with greater concentrations in HYP than EU (HYP: 2.76 [1.72–4.65] ng/mOsm; EU: 1.94 [1.1–2.54] ng/mOsm; P = 0.003; median [interquartile range]). Osmolality-corrected urinary neutrophil gelatinase-associated lipocalin (uNGAL) concentrations were increased post-exercise (P < 0.001), but there was no trial by time interaction effect (P = 0.073). Conclusion These results suggest that hypohydration produced by high-intensity intermittent running increases renal injury, compared to when euhydration is maintained, and that the site of this increased renal injury is at the proximal tubules.

The association of urine osmolality with decreased kidney function and/or albuminuria in the United States

Background Decreased kidney function is commonly caused by hypovolemia. When hypovolemic, the kidney reabsorbs water resulting in concentrated urine. Osmolality is a measure of urine concentration which is more objective than self-reported fluid intake. It has a positive association with hypovolemia. However, it remains controversial whether osmolality is associated with decreased kidney function and/or albuminuria. Methods We conducted a cross-sectional analysis of the 2009–2012 National Health and Nutrition Examination Survey, a standardized survey in the U.S. population. Participants aged 18–70 years old with random urine osmolality were included. Osmolality was categorized as quartiles. Decreased kidney function was defined by estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m2 and albuminuria was defined by albumin-to-creatinine ratio ≥ 30 mg/gm. We performed multivariable regression via four sequential models. Results Our study sample included 7,373 participants. The mean age was 42.9 ± 0.4 years. Overall, 51.4% were male and 67.3% were white. The mean osmolality was 603.8 mOsm/kg and 629.1 mOsm/kg in those with and without decreased eGFR and/or albuminuria, respectively. The number of cases was 610 (6.7%). The prevalence from the lowest to highest quartiles of osmolality was 116 (6.2%), 213 (8.6%), 179 (7.5%), and 102 (4.3%), respectively (p-value for trend = 0.02). The relationship between osmolality and eGFR appeared nonlinear. After adjustment for demographic, social, cardiovascular, and dietary risk factors, there was no significant association of osmolality quartiles with decreased eGFR and/or albuminuria (odds ratio [OR] 0.77, 95% confidence interval [CI] 0.56, 1.07). In sensitivity analyses, osmolality ≥ 500 mOsm/kg was associated with lower eGFR (adjusted ß -1.13, 95% CI -1.98, -0.28). In pre-specified subgroup analyses, osmolality had a statistically significant negative correlation with eGFR among individuals with eGFR ≥ 60 mL/min/1.73m2, but a positive correlation among those with eGFR < 60 mL/min/1.73m2 (adjusted ß -0.19, 95% CI -0.36, -0.01 versus adjusted ß 0.50, 95% CI 0.05, 0.96; p-value for interaction = 0.016). Conclusions Higher osmolality was significantly associated with lower eGFR among adults with eGFR ≥ 60 mL/min/1.73m2 Future research should examine the relationship between osmolality and change in kidney function over time among adults with normal eGFR.

Relationships Between WUT (Body Weight, Urine Color, and Thirst Level) Criteria and Urine Indices of Hydration Status

Background: A Venn diagram consisting of percentage body mass loss, urine color, and thirst perception (weight, urine, thirst [WUT]) has been suggested as a practical method to assess hydration status. However, no study to date has examined relationships between WUT and urine hydration indices. Thus, the purpose of this study was to investigate relationships between urine specific gravity, urine osmolality, and the WUT criteria. Hypothesis: Urine specific gravity and urine osmolality indicate hypohydration when the WUT criteria demonstrate hypohydration (≥2 markers). Study Design: Laboratory cohort study. Level of Evidence: Level 3. Methods: A total of 22 women (mean ± SD; age, 20 ± 1 years; mass, 65.4 ± 12.6 kg) and 21 men (age, 21 ± 1 years; body mass, 78.7 ± 14.6 kg) participated in this study. First morning body mass, urine color, urine specific gravity, urine osmolality, and thirst level were collected for 10 consecutive days in a free-living situation. Body mass loss >1%, urine color >5, and thirst level ≥5 were used as the dehydration thresholds. The number of markers that indicated dehydration levels were counted and categorized into either 3, 2, 1, or 0 WUT markers that indicated dehydration. One-way analysis of variance with Tukey pairwise comparisons was used to assess the differences in urine specific gravity and urine osmolality between the different number of WUT markers. Results: Urine specific gravity in 3 WUT markers (mean ± SD [effect size], 1.021 ± 0.007 [0.57]; P = 0.025) and 2 WUT markers (1.019 ± 0.010 [0.31]; P = 0.026) was significantly higher than 1 WUT marker (1.016 ± 0.009). Urine mosmolality in 2 WUT markers (705 ± 253 mOsmol [0.43]; P = 0.018) was significantly higher than 1 WUT (597 ± 253 mOsmol). Meeting at least 2 WUT markers resulted in sensitivities of 0.652 (2 WUT criteria met) and 0.933 (3 WUT criteria met) to detect urine osmolality >700 mOsmol. Conclusion: These results suggest that when 3 WUT markers are met, urine specific gravity and urine osmolality were greater than euhydration cutoff points. The WUT criterion is a useful tool to use in field settings to assess hydration status when first morning urine sample was used. Clinical Relevance: Athletes, coaches, sports scientists, and medical professionals can use WUT criteria to monitor dehydration with reduced cost and time.

The Beverage Hydration Index: Influence of Electrolytes, Carbohydrate and Protein

The beverage hydration index (BHI) facilitates a comparison of relative hydration properties of beverages using water as the standard. The additive effects of electrolytes, carbohydrate, and protein on rehydration were assessed using BHI. Nineteen healthy young adults completed four test sessions in randomized order: deionized water (W), electrolytes only (E), carbohydrate-electrolytes (C + E), and 2 g/L dipeptide (alanyl-glutamine)-electrolytes (AG + E). One liter of beverage was consumed, after which urine and body mass were obtained every 60 min through 240 min. Compared to W, BHI was higher (p = 0.007) for C + E (1.15 ± 0.17) after 120 min and for AG + E (p = 0.021) at 240 min (1.15 ± 0.20). BHI did not differ (p > 0.05) among E, C + E, or AG + E; however, E contributed the greatest absolute net effect (>12%) on BHI relative to W. Net fluid balance was lower for W (p = 0.048) compared to C + E and AG + E after 120 min. AG + E and E elicited higher (p < 0.001) overall urine osmolality vs. W. W also elicited greater reports of stomach bloating (p = 0.02) compared to AG + E and C + E. The addition of electrolytes alone (in the range of sports drinks) did not consistently improve BHI versus water; however, the combination with carbohydrate or dipeptides increased fluid retention, although this occurred earlier for the sports drink than the dipeptide beverage. Electrolyte content appears to make the largest contribution in hydration properties of beverages for young adults when consumed at rest.