Osmolality

 

ECF osmolality can be approximated using the major solutes: (2 x sodium) + (glucose / 18 ) + (BUN / 2.8)

 

Measured osmolality usually equals the calculated osmolality. However, if other osmotically active substances are present, the measured value will be higher, and the osmolality gap suggests the presence of toxins.

 

 

Causes of Osmolar Gap

Methanol, mannitol

Alcohols: ethanol, isopropanol

Dyes

Glycols, glycerol

Acetone

Sorbitol