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    Chief Complaint


    Organ System


    Patent Pending

    Serum Osmolality/Osmolarity

    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.

    Note that at extremes of serum glucose, such as in hyperosmolar hyperglycemic state (HHS), osmolar gap is skewed, and clinical judgment should be used to make decisions regarding correction.



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    Creator Insights
    Dr. Roy Purssell

    About the Creator

    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

    Are you Dr. Roy Purssell? Send us a message to review your photo and bio, and find out how to submit Creator Insights!
    MDCalc loves calculator creators – researchers who, through intelligent and often complex methods, discover tools that describe scientific facts that can then be applied in practice. These are real scientific discoveries about the nature of the human body, which can be invaluable to physicians taking care of patients.
    About the Creator
    Dr. Roy Purssell
    Are you Dr. Roy Purssell?