What is the role of the osmolal gap the workup for metabolic acidosis?

Updated: Oct 05, 2018
  • Author: Antonia Quinn, DO; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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The osmolal gap is the measured plasma osmolality minus calculated osmolality. The serum osmolality is composed of all osmotically active substances including ionic and nonionic substances such as serum ions, glucose, and BUN. Other substances such as alcohols, excess serum lipids and proteins, and delivered substances such as mannitol all contribute to the serum osmolality. The calculated osmolality is 2 X plasma [Na+] + [glucose]/18 + BUN/2.8.

Normal osmolal gap is 10-15.

Metabolic acidosis with elevated osmolal gap indicates methanol and ethylene glycol ingestions.

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