Osmol gap

Osmol gap is a diagnostic measure used in medicine to identify the presence of certain substances in the blood. It is calculated by subtracting the measured osmolality of a blood sample from the calculated osmolality. An elevated osmol gap can indicate the presence of certain toxins or substances in the blood, such as methanol or ethylene glycol.

Calculation[edit | edit source]

The osmol gap is calculated using the following formula:

Osmol gap = Measured osmolality - Calculated osmolality

The calculated osmolality is typically determined using the concentrations of sodium, glucose, and blood urea nitrogen (BUN) in the blood. The formula for calculated osmolality is:

Calculated osmolality = 2 * Sodium (mEq/L) + Glucose (mg/dL) / 18 + BUN (mg/dL) / 2.8

Clinical significance[edit | edit source]

An elevated osmol gap can indicate the presence of certain substances in the blood that are not accounted for in the calculated osmolality. These can include toxins such as methanol, ethylene glycol, or isopropanol, as well as certain medications or substances used in medical treatments.

In addition to its use in identifying the presence of these substances, the osmol gap can also be used to monitor the effectiveness of treatment for poisoning by these substances. A decreasing osmol gap can indicate that the treatment is effectively removing the substance from the blood.

Limitations[edit | edit source]

While the osmol gap is a useful diagnostic tool, it has some limitations. It is not specific for any particular substance, and an elevated osmol gap can be caused by a variety of factors. Additionally, the osmol gap can be affected by errors in the measurement or calculation of osmolality.

See also[edit | edit source]

Osmol gap Resources
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