Serum_Osmolality v.1

Calculates expected serum osmolarity, for comparison to measured osmolarity to detect unmeasured compounds in the serum.

Emma Malm

emmalm@kth.se

Cambio CDS

To detect unmeasured compounds in the serum. Osmolal gaps (difference between measured and expected) of >10 can be caused by toxic alcohols.

Formula 1 Purssell et al equation for calculating serum osmolality with US units: Serum osm [mOsm/kg] = (2 × Na + (BUN / 2.8) + (glucose / 18) + (ethanol / 3.7) Purssell et al equation for calculating serum osmolality with SI units: Serum osm [mOsm/kg] = 2 × Na + BUN + glucose + ethanol Normal serum osm is 285-295 Formula 2 Osmolal gap equation: Osmolal gap [mOsm/kg] = measured serum osm [mOsm/kg or mmol/kg] - calculated serum osm [mOsm/kg] Normal serum osm gap is -14 to +10

1. Purssell RA, Pudek M, Brubacher J, Abu-Laban RB.Derivation and validation of a formula to calculate the contribution of ethanol to the osmolal gap.Ann Emerg Med 2001;38(6): 653-9.doi:10.1067/mem.2001.119455. PMID 1171974. 2. Glasser L, Sternglanz PD, Combie J, Robinson A. Serum osmolality and its applicability to drug overdose. Am J Clin Pathol. 1973 Nov;60(5):695-9. doi: 10.1093/ajcp/60.5.695. PMID: 4751712.

OBSERVATION.lab_test-serum_sodium.v1, OBSERVATION.lab_test_glucose.v1, OBSERVATION.lab_test_serum_ethanol.v0, OBSERVATION.lab_test-urea_and_electrolytes.v1, OBSERVATION.blood_serum.v0