Validation of equations used to predict plasma osmolality in a healthy adult cohort

Heavens, Kristen R.; Kenefick, Robert W.; Caruso, Elizabeth M.; Spitz, Marissa G; Cheuvront, Samuel N.

doi:10.3945/ajcn.114.091009

Cited by 37 publications

(34 citation statements)

References 42 publications

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“…In an equilibrated state, blood osmolality reflects the concentration of body fluids. The normal range of hydration as measured by osmolality for healthy populations is recognized as being between 275 and 295 mOsm (27, 58), with higher values indicating a greater degree of dehydration (30). However, body weight change provides an accurate index of hydration change when measurements are made more frequently than once a day (25).…”

Section: Discussionmentioning

confidence: 99%

Recruitment, Methods, and Descriptive Results of a Physiologic Assessment of Latino Farmworkers

Mitchell

Castro

Armitage

et al. 2017

Journal of Occupational &Amp; Environmental Medicine

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Objective The California Heat Illness Prevention Study devised methodology and collected physiological data to assess Heat Related Illness (HRI) risk in Latino farmworkers. Methods Bilingual researchers monitored HRI across a work shift, recording core temperature, work rate (METs) and heart rate at minute intervals. Hydration status was assessed by changes in weight and blood osmolality. Personal data loggers and a weather station measured exposure to heat. Interviewer administered questionnaires were used to collect demographic and occupational information. Results California farmworkers (n=588) were assessed. Acceptable quality data were obtained from 80% of participants (core temperature) to 100% of participants (weight change). Workers (8.3%) experienced a core body temperature ≥ 38.5°C and 10.8% experienced dehydration (lost more than 1.5% of body weight). Conclusions Methodology is presented for the first comprehensive physiological assessment of HRI risk in California farmworkers.

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Section: Discussionmentioning

confidence: 99%

Recruitment, Methods, and Descriptive Results of a Physiologic Assessment of Latino Farmworkers

Mitchell

Castro

Armitage

et al. 2017

Journal of Occupational &Amp; Environmental Medicine

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“…Plasma samples (150 µL) were also analyzed for sodium and blood urea nitrogen by direct ion selective electrode (ISE), and glucose by enzymatic determination, all being done using a Stat Profile Critical Care Xpress (Nova Biomedical, Waltham, MA). In an effort to minimize user complexity wherever possible, plasma osmolarity was calculated from the simplest of the most accurate equations available: sodium, glucose, and blood urea nitrogen (BUN) (2× sodium [mmol/L] + glucose [mmol/L] + BUN [mmol/L]) …”

Section: Methodsmentioning

confidence: 99%

Importance of sample volume to the measurement and interpretation of plasma osmolality

Sollanek

Kenefick

Cheuvront

2018

Clinical Laboratory Analysis

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BackgroundSmall sample volumes may artificially elevate plasma osmolality (Posm) measured by freezing point depression. The purpose of this study was to compare two widely different sample volumes of measured Posm (mmol/kg) to each other, and to calculated osmolarity (mmol/L), across a physiological Posm range (~50 mmol/kg).MethodsPosm was measured using freezing point depression and osmolarity calculated from measures of sodium, glucose, and blood urea nitrogen. The influence of sample volume was investigated by comparing 20 and 250 μL Posm samples (n = 126 pairs). Thirty‐two volunteers were tested multiple times while EUH (n = 115) or DEH (n = 11) by −4.0% body mass. Protinol™ (240, 280, and 320 mmol/kg) and Clinitrol™ (290 mmol/kg) reference solutions were compared similarly (n = 282 pairs).ResultsThe 20 μL samples of plasma showed a 7 mmol/kg positive bias compared to 250 μL samples and displayed a nearly constant proportional error across the range tested (slope = 0.929). Calculated osmolarity was lower than 20 μL Posm by the same negative bias (−6.9 mmol/kg) but not different from 250 μL Posm (0.1 mmol/kg). The differences between 20 and 250 μL samples of Protinol™ were significantly higher than Clinitrol™.ConclusionsThese results demonstrate that Posm measured by freezing point depression will be ~7 mmol/kg higher when using 20 μL vs 250 μL sample volumes. Approximately half of this effect may be due to plasma proteins. Posm sample volume should be carefully considered when calculating the osmole gap or assessing hydration status.

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“…There are several empirical formulas to calculate serum osmolality (21)(22)(23)(24)(25)(26)(27)(28)(29). These equations generally have been determined by plotting measured serum osmolality against sodium using linear regression analysis (21)(22)(23)(24).…”

Section: + Constant }/Plasma Watermentioning

confidence: 99%

“…But, the concentration of only effective osmoles refers to 'effective osmolality' or 'tonicity' (29 The normal range of plasma tonicity is 275-295 mOsm/kg of water (13). Osmolality and tonicity are not synonymous, so that, hyperosmolality may be without hypertonicity (e.g.…”

Section: Effective Osmolality or Tonicitymentioning

confidence: 99%

Basic concepts and practical equations on osmolality: Biochemical approach

Rasouli

2016

Clinical Biochemistry

120

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Validation of equations used to predict plasma osmolality in a healthy adult cohort

Cited by 37 publications

References 42 publications

Recruitment, Methods, and Descriptive Results of a Physiologic Assessment of Latino Farmworkers

Recruitment, Methods, and Descriptive Results of a Physiologic Assessment of Latino Farmworkers

Importance of sample volume to the measurement and interpretation of plasma osmolality

Basic concepts and practical equations on osmolality: Biochemical approach

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