What is plasma osmolarity?

Solutes in plasma. Plasma osmolarity is a reflection of various salts in plasma. It can be measured directly, usually by freezing point depression, or commonly calculated using the following equation = 2[na+] + [glucose]/18 + [ BUN ]/2.8 where [glucose] and [bun] are measured in mg/dl. Normal value is 270-310 milli-osmoles per kilogram.

Related Questions

What is plasma osmolarity? Plasma osmolality?

Conc. electrolytes. These refer to the concentration of electrolytes in the body/plasma, or the electrolyte-water balance. These measure the same thing, only that osmolality is the number of osmoles per kilogram of solvent or osm/kg, while osmolarity is the number of osmoles per liter of solution or osm/ltr. Osmolality excludes the solute, while osmolarity includes it, so osmolality has a slightly higher reading. Read more...
Minor difference. Osmolarity is number of moles in a liter of solution and osmolality is number of moles of solute in a kg of water. Normal plasma osmolality is about 290 mosmol/kg. Read more...

When tumors secrete high levels of vasopressin, what happens to plasma osmolarity, urine osmolarity and urine volume?

SIADH. Plasma osmolarity will decrease, urine osmolarity will increase, and urine volume will decrease. Read more...
Tricky concept. ADH / vasopressin makes the body reabsorb water. However, the atrial natriuretic peptide then kicks in and rids the body of that water by forcing excretion of sodium in the urine. Low plasma sodium / lowish osmolarity; urine sodium will be inappropriately high. Read more...

What happens to plasma and urine osmolarity with a lung tumor that secretes vasopressin (adh)?

V plasma & ^ Urine. Vasopressin/adh increases the amount of water reabsorbed by the kidneys and decreases the amount of water excreted into the urine. With more water in the bloodstream, the concentration of everything else decreases (so osmolality goes down), while the concentration of everything in the urine goes up (as dose the urine osmolality). Read more...