Serum osmolal gap in clinical practice: usefulness and limitations

ABSTRACT

Background: Although serum osmolal gap can be a useful diagnostic tool, clinicians are not familiar with its use in clinical practice.

Objectives: The review presents in a series of questions-answers and under a clinical point of view the current data regarding the use of osmolal gap.

Discussion: The definition and the best formula used for the calculation of osmolal gap, the main causes of increased osmolal gap with or without increased anion gap metabolic acidosis, as well as the role of concurrent lactic acidosis or ketoacidosis are presented under a clinical point of view.

Conclusions: The calculation of osmolal gap is crucial in the differential diagnosis of many patients presenting in emergency departments with possible drug or substance overdose as well as in comatose hospitalized patients.

KEYWORDS:

• Osmolal gap
• osmol gap
• anion gap
• methanol
• toxic alcohols
• metabolic acidosis

Declaration of interest

M Elisaf has received speaker honoraria, consulting fees, and research funding from AstraZeneca, Schering Plough, Merck, Pfizer, Solvay, Abbott, Boehringer Ingelheim and Fournier, and has participated in clinical trials with AstraZeneca, Merck, Sanofi-Synthelabo, Solvay, Glaxo, Novartis, Pfizer and Fournier. The authors have given talks and attended conferences sponsored by various pharmaceutical companies, including Bristol-Myers Squibb, Pfizer, Lilly, Abbott, Amgen, Astrazeneca, Novartis, Vianex, Teva and MSD. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Additional information

Funding

This manuscript was not funded.