Osmolality
Posted: Thursday, August 5th, 2021 | Updated: Monday, February 7th, 2022
Posted: Thursday, August 5th, 2021 | Updated: Monday, February 7th, 2022
Calculation of Osmolality
mOsm/L = 2 [(Na+) + (K+)] + (BUN/2.8) + (Glucose/18)
Na+ and K+ are measured in mEq/L
BUN and Glu are measured in mg/dL
When to Start Treatment
Therapy is warranted when osmolality concentrations are less than 260 mOsm/L or greater than 360 mOsm/L
The Osmolality Gap
The difference between the measured osmolality and the calculated osmolality. Osmolality Gap should be <10 mOsm/L. If the osmolality gap is >20 mOsm/L consider the presence of anions (ex. ethylene glycol metabolites)
Note
Hyperosmolality can lead to disorientation, stupor, and coma. Hyperosmolality is classified as such with levels at or above 330 to 340 mOsm/L
mOsm/L = 2 [(Na+) + (K+)] + (BUN/2.8) + (Glucose/18)
Na+ and K+ are measured in mEq/L
BUN and Glu are measured in mg/dL
When to Start Treatment
Therapy is warranted when osmolality concentrations are less than 260 mOsm/L or greater than 360 mOsm/L
The Osmolality Gap
The difference between the measured osmolality and the calculated osmolality. Osmolality Gap should be <10 mOsm/L. If the osmolality gap is >20 mOsm/L consider the presence of anions (ex. ethylene glycol metabolites)
Note
Hyperosmolality can lead to disorientation, stupor, and coma. Hyperosmolality is classified as such with levels at or above 330 to 340 mOsm/L
Sources:
Ford, Richard B., and Elisa M. Mazzaferro. Kirk and Bistner's Handbook of Veterinary Procedures and Emergency Treatment. 8th ed., Saunders Elsevier, 2006.
Ford, Richard B., and Elisa M. Mazzaferro. Kirk and Bistner's Handbook of Veterinary Procedures and Emergency Treatment. 8th ed., Saunders Elsevier, 2006.