Calculations shouldn't be used alone for patient care, and don't substitute for professional judgment. See our full disclaimer.
Calculates expected serum osmolarity, for comparison to measured osmolarity to detect unmeasured compounds in the serum.
When to Use
Osmolal gaps (difference between measured and expected) of >10 can be caused by toxic alcohols (ethanol, methanol, ethylene glycol, isopropyl alcohol*); mannitol; and lorazepam infusions (which contain propylene glycol).
*Isopropyl alcohol causes a large osmolar gap but does not cause a anion gap metabolic acidosis.
Roy Purssell, MD, is an emergency doctor at Vancouver General Hospital and a professor in the Department of Emergency Medicine at the University of British Columbia. He is also the medical director of the BC Drug and Poison Information Centre and the president of the Canadian Association of Poison Control Centres. Dr. Purssell's areas of research include impaired driving, substance abuse, laboratory testing and adverse drug reactions.
To view Dr. Roy Purssell's publications, visit PubMed