Surgery>>>>>Fluid and Electrolyte Management of the Surgical Patient
Question 10#

If a patient's serum glucose increases by 180 mg/dL, what is the increase in serum osmolality, assuming all other laboratory values remain constant?

A. Does not change
B. 8
C. 10
D. 12

Correct Answer is C

Comment:

Osmotic pressure is measured in units of osmoles (osm) or milliosmoles (mOsm) that refer to the actual number of osmotically active particles. For example, 1 millimole (mmol) of sodium chloride contributes to 2 mOsm (one from sodium and one from chloride).

The principal determinants of osmolality are the concentrations of sodium, glucose, and urea (blood urea nitrogen [BUN] ):

Calculated serum osmolality= 2 x sodium + glucose / 18 + BUN / 2.8