Anion Gap and Osmolar Gap (High)

Calculations

Anion Gap

AG = Na - (Cl + HCO3)

Calculated Osm

Calculated Osm = 2 x Na + (glu/18) + (BUN/2.8) + (ethanol/4.6) + (methanol/2.6) + (ethylene glycol/5) + (acetone/5.5) + (isopropanol/5.9)

  • Normal = 275-295

Osmolal Gap

Osmolal Gap = measured osm - calculated osm

  • Normal = (-)14-10 mOsm/L

Differential Diagnosis

Toxicological

Non-Toxicological

CAT MUDPILERS

Evaluation

Toxic Alcohols Anion/Osmolar Gaps

Osmolar gap Anion gap Management
Ethanol + + if ketoacidosis Mainly supportive
Ethylene glycol + + Fomepizole, Thiamine, Pyridoxine, +/- Dialysis
Methanol + + Fomepizole, Folinic acid, +/- Dialysis
Isopropyl alcohol + - Mainly supportive

See Also

External Links

References