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Clinical Biochemistry Aug 2016The terms osmotic pressure, osmotic coefficient, osmole, osmolarity, osmolality, effective osmolality and delta osmolality are formally defined. Osmole is unit of the... (Review)
Review
The terms osmotic pressure, osmotic coefficient, osmole, osmolarity, osmolality, effective osmolality and delta osmolality are formally defined. Osmole is unit of the amount of substance, one mole of nonionized impermeant solute is one osmole. Assuming an ideal solution, osmotic pressure (π) in mmHg is 19.3 times the osmolarity. Osmolarity is defined as the number of milliosmoles of the solutes per liter of solution. Suitable equations are presented for the rapid calculation of the osmolarity of different solutions. The concentrations of electrolytes are expressed by mEq/L that is, equal to their osmolarity as mOsm/L. If the solute concentration (C) is expressed as mg/L, mg/dL and g%, osmolarity is calculated as: C.n' /MW, C.n' (10)/MW and C.n' (10(4))/MW respectively. Osmolality is milliosmoles of solutes per one kilogram (or liter) of water of solution (plasma) and is calculated by osmolarity divided to plasma water. The osmolal concentration is corrected to osmolal activity by using the osmotic coefficient, φ. The salts of sodium (choloride and bicarbonate) and nonelectrolyte glucose and urea are the major five osmoles of plasma. The equation: Posm =2 [Na(+)]+glucose (mg/dL)/18+BUN (mg/dL)//2.8 is also the simplest and best formula to calculate plasma osmolality. The concentration of only effective osmoles evaluates effective osmolality or tonicity as: Eosm =2 [Na(+)]+glucose/18. The normal range of plasma tonicity is 275-295mOsm/kg of water. The difference between the measured and calculated osmolality is called osmolal gap. It is recommended to withdraw the formula of Dorwart-Chalmers from the textbooks and autoanalyzers and to use the simplest equation of Worthley et al. as the best equation for calculating serum osmolality. Furthermore the normal ranges of osmolal gap also must be corrected to 0±2mOsm/L.
Topics: Humans; Models, Theoretical; Osmolar Concentration; Serum
PubMed: 27343561
DOI: 10.1016/j.clinbiochem.2016.06.001 -
Pediatric Nephrology (Berlin, Germany) Apr 2023Serum osmolality is the sum of the osmolalities of every single dissolved particle in the blood such as sodium and associated anions, potassium, glucose, and urea. Under... (Review)
Review
Serum osmolality is the sum of the osmolalities of every single dissolved particle in the blood such as sodium and associated anions, potassium, glucose, and urea. Under normal conditions, serum sodium concentration is the major determinant of serum osmolality. Effective blood osmolality, so-called blood tonicity, is created by the endogenous (e.g., sodium and glucose) and exogenous (e.g., mannitol) solutes that are capable of creating an osmotic gradient across the membranes. In case of change in effective blood osmolality, water shifts from the compartment with low osmolality into the compartment with high osmolarity in order to restore serum osmolality. The difference between measured osmolality and calculated osmolarity forms the osmolal gap. An increase in serum osmolal gap can stem from the presence of solutes that are not included in the osmolarity calculation, such as hypertonic treatments or toxic alcoholic ingestions. In clinical practice, determination of serum osmolality and osmolal gap is important in the diagnosis of disorders related to sodium, glucose and water balance, kidney diseases, and small molecule poisonings. As blood hypertonicity exerts its main effects on the brain cells, neurologic symptoms varying from mild neurologic signs and symptoms to life-threatening outcomes such as convulsions or even death may occur. Therefore, hypertonic states should be promptly diagnosed and cautiously managed. In this review, the causes and treatment strategies of hyperosmolar conditions including hypernatremia, diabetic ketoacidosis, hyperglycemic hyperosmolar syndrome, hypertonic treatments, or intoxications are discussed in detail to increase awareness of this important topic with significant clinical consequences.
Topics: Humans; Mannitol; Urea; Osmolar Concentration; Sodium; Glucose
PubMed: 35779183
DOI: 10.1007/s00467-022-05668-1 -
Nihon Rinsho. Japanese Journal of... Feb 1995
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ELife Nov 2021Two neural circuits control the release of vasopressin in response to eating and drinking before there are any detectable changes in blood water levels.
Two neural circuits control the release of vasopressin in response to eating and drinking before there are any detectable changes in blood water levels.
Topics: Drinking; Osmolar Concentration; Water
PubMed: 34792465
DOI: 10.7554/eLife.74551 -
International Journal of Laboratory... Jun 2023
Topics: Humans; Erythrocyte Indices; Osmolar Concentration; Erythrocytes
PubMed: 36700927
DOI: 10.1111/ijlh.14022 -
American Journal of Diseases of... Nov 1981
Topics: Dehydration; Humans; Hypernatremia; Infant; Osmolar Concentration
PubMed: 7294018
DOI: 10.1001/archpedi.1981.02130350001001 -
Developmental Pharmacology and... 1988The use of physical methods such as freezing point depression for the estimation of osmolality of preparations given to infants may be misleading. The reasons for this... (Review)
Review
The use of physical methods such as freezing point depression for the estimation of osmolality of preparations given to infants may be misleading. The reasons for this are discussed, and reference made to some other properties of preparation vehicles which may be of concern.
Topics: Animals; Chemical Phenomena; Chemistry; Humans; Infant; Osmolar Concentration; Pharmaceutical Vehicles
PubMed: 3056675
DOI: 10.1159/000457707 -
Nature Reviews. Gastroenterology &... Apr 2022
Topics: Humans; Osmolar Concentration; Thirst; Water-Electrolyte Balance
PubMed: 35149844
DOI: 10.1038/s41575-022-00590-1 -
American Journal of Hospital Pharmacy Apr 1980The confusion that often exists between osmolality and osmolarity is discussed, and the clinical importance of careful distinction between these terms is emphasized. The... (Review)
Review
The confusion that often exists between osmolality and osmolarity is discussed, and the clinical importance of careful distinction between these terms is emphasized. The clinical effects of abnormal osmotic strength of parenteral solutions, methods of determining osmolality and osmolarity, and the practical applications of these concepts are reviewed. Although osmolality can be determined experimentally (whereas osmolarity cannot) it is difficult or impossible to use osmolality in calculations associated with the extemporaneous preparation and administration of fluids such as i.v. admixtures. Hence, there is a need in many cases for product labels to state both osmolality and osmolarity.
Topics: Chemistry, Pharmaceutical; Hypertonic Solutions; Hypotonic Solutions; Mathematics; Osmolar Concentration; Osmotic Pressure; Terminology as Topic
PubMed: 6990751
DOI: No ID Found -
Liver International : Official Journal... Aug 2020
Topics: Hepatic Encephalopathy; Humans; Liver Failure; Osmolar Concentration; Specific Gravity
PubMed: 33135858
DOI: 10.1111/liv.14549