osmolality


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osmolality

 [oz″mo-lal´ĭ-te]
the concentration of a solution in terms of osmoles of solutes per kilogram of solvent.
serum osmolality a measure of the number of dissolved particles per unit of water in serum. In a solution, the fewer the particles of solute in proportion to the number of units of water (solvent), the less concentrated the solution. A low serum osmolality means a higher than usual amount of water in relation to the amount of particles dissolved in it, and accompanies overhydration, or edema. An increased serum osmolality indicates deficient fluid volume. Measurement of the serum osmolality gives information about the hydration status within the cells because of the osmotic equilibrium that is constantly being maintained on either side of the cell membrane (homeostasis). Water moves freely back and forth across the membrane in response to the osmolar pressure being exerted by the molecules of solute in the intracellular and extracellular fluids. Serum osmolality reflects the status of hydration of the intracellular as well as the extracellular compartments and thus describes total body hydration. The normal value for serum osmolality is 270–300 mOsm/kg water.
urine osmolality a measure of the number of dissolved particles per unit of water in the urine. A more accurate measure of urine concentration than specific gravity, urine osmolality is useful in diagnosing renal disorders of urinary concentration and dilution and in assessing status of hydration. The normal value is 500 to 800 mOsm/L.

os·mo·lal·i·ty

(oz'mō-lal'i-tē), Do not confuse this word with osmolarity.
The concentration of a solution expressed in osmoles of solute particles per kilogram of soluent.

osmolality

Toxicology A measure of the amount of osmotically effective solute/1000 g of solvent; serum osmolality is↑ in Ethanol, azotemia, dehydration, DM, hypercalcemia, hyperglycemia, hypernatremia, ethylene glycol, glycerine, INH, ketosis, mannitol therapy, methanol, pyelonephritis, renal tubular necrosis, diabetes insipidus, shock, sorbitol, uremia ↓ in Overhydation, ↑ fluid intake, ↓ Na+, paraneoplastic syndrome, SIADH; urine osmolality is ↑ in SIADH, liver disease, heart disease, dehydration ↓ in Overhydration, diabetes insipidus, ↓ K+ Ref range Serum, 275-295 mOsm/Kg; urine 50–1400 mOsm/Kg Critical (panic) values ≤ 265 mOsm/Kg; ≥ 320 mOsm/Kg. See Delta osmolality, Effective osmolality.

os·mo·lal·i·ty

(oz'mō-lal'i-tē)
The concentration of a solution expressed in osmoles of solute particles per kilogram of solvent.

osmolality

The property of a solution that depends on its concentration in osmolal units. See OSMOLE.

Osmolality

A measurement of urine concentration that depends on the number of particles dissolved in it. Values are expressed as milliosmols per kilogram (mOsm/kg) of water.
References in periodicals archive ?
The purpose of this study were twofold: 1) to create reference values for juvenile black-bellied whistling ducks for select blood gases, electrolyte, and osmolality values by using a point-of-care analyzer, and 2) to compare osmolality and hematocrit values determined by the point-of-care analyzer against those measured by standard methods.
Serum electrolyte ([Na.sup.+], [K.sup.+], [Cl.sup.-]) levels and osmolality
Studies of the osmolality of human milk have typically focused in its fortification and nutritional aspects.
Measurement of Murine Urine pH and Osmolality. Murine urine was collected and the pH measured with pH strips and the osmolality measured using a Reichert TS 400 total solids refractometer (Reichert Analytical Instruments, Buffalo, NY) to assess the specific gravity.
Based on her clinical findings of witnessed seizure, laboratory findings of severe hyponatremia, hypoosmolality, elevated urine osmolality, and elevated urinary sodium in the presence of normal adrenal and thyroid function, a diagnosis of acute severe symptomatic hypotonic hyponatremia or SIADH was made based on the diagnostic criteria (Table 2).
After eight hours of observed water deprivation, urine osmolality increased from 270 mOsm/kg to 753 mOsm/kg.
Urine osmolality of above 100 mOsm/kg suggested a degree of vasopressin secretion leading to inability to excrete free water.
In applying the PDMS plate to the culture of bovine embryos, we then measured the osmolality of the medium in regular and LP-PDMS plates every 24 hours to investigate whether the difference in the surface structure affects the osmolality of the medium.
The models included the corresponding measurement (timepoint 0 for body weight, urinary volume excretion, AUC serum sodium concentration, serum-/urinary osmolality, serum glucose, natriuresis, glucosuria, FEurea, FEuricacid; timepoint -1 for copeptin, MR-proANP, NT-proBNP, aldosterone, and renin) as covariate, treatment, treatment-sequence (i.e., empagliflozin-placebo versus placebo-empagliflozin) and their interaction as predictors (fixed effects), and subject as a random effect.
The syndrome is characterized by a low level of sodium concentration in serum, that is, <135 mmol/l, urinary osmolality exceeding 200 mOsm/kg, serum osmolality of <280 mOsm/kg, and urinary sodium concentration exceeding 20 mmol/l.
An autonomous arginine-vasopressin (AVP) secretion, independent from plasma osmolality or from the volemic state, is present.