Osmolarity is a measure of the osmoles of solute per liter of solution, while the osmolality is a measure of the osmoles of solute per kilogram of solvent.
from http://en.wikipedia.org/wiki/Osmolarity
To calculate plasma osmolarity (osmolality) use the following equation:
Posm = 2[Na+] + [Glucose]/18 + [ BUN ]/2.8
The above equation holds true if the glucose & ureas blood chemistry units are given as: mg/dL.
If the units are given as: mmol/l; then the calculated osmolality is given by:
P.OSM = 2[NA] + 2[K+] + [Urea] + [Glucose]
Osmolality can be measured on an analytical instrument called an Osmometer. It works on the method of depression of freezing point.
The Osmolar gap is the diffence between the measured osmolality and the calculated osmolality.
from http://en.wikipedia.org/wiki/Plasma_osmolality
from http://en.wikipedia.org/wiki/Osmolarity
Plasma osmolality
Plasma osmolality is a measure of the concentration of substances such as sodium, chloride, potassium, urea, glucose, and other ions in human blood. It is calculated as the osmoles of solute per kilogram of solvent. Normal osmolality in plasma is about 280 - 303 milli-osmoles per kilogram. It is affected by changes in water content.To calculate plasma osmolarity (osmolality) use the following equation:
Posm = 2[Na+] + [Glucose]/18 + [ BUN ]/2.8
The above equation holds true if the glucose & ureas blood chemistry units are given as: mg/dL.
If the units are given as: mmol/l; then the calculated osmolality is given by:
P.OSM = 2[NA] + 2[K+] + [Urea] + [Glucose]
Osmolality can be measured on an analytical instrument called an Osmometer. It works on the method of depression of freezing point.
The Osmolar gap is the diffence between the measured osmolality and the calculated osmolality.
from http://en.wikipedia.org/wiki/Plasma_osmolality
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