Application: Suspected poisoning with alcohol, methanol, ethylene glycol, acetone, isopropanol, diethyl ether or paraldehyde. Assessment of water and electrolyte balance, in conjunction with urine osmolality.
Explanation: Osmolality measures the concentration of dissolved particles in blood. Osmolality increases with dehydration and decreases with overhydration. An increased osmolar gap indicates the presence of alcohol or other osmotically active substances (organic acids, sugars). In the presence of these substances, there is an “osmolal gap”. This gap represents the difference between what the serum osmolality should be (based on serum Na, glucose, and BUN) and what the osmolality is actually measured to be. A large gap should raise suspicion of the presence of organic acids (e.g.-ketones) excessive glucose, or ethanol byproducts. Urine osmolality measurements may assist interpretation.
Specimen: 5 ml blood in red-top tube.
Reference Interval:
285-295 mOsm/kg H2O (Adult)
275-290 mOsm/kg H2O (Child)
