It has been noted that the residual calculated osmolal gap increases with increasing ethanol levels. Purssell et al. found that there is a linear relationship between the serum ethanol level and the osmolal gap. What do they suggest the multiplicative factor for ethanol in formulas to calculate serum osmolarity be?
Purssell et al. findings suggest that each millimole of ethanol contributes 1.25 mOsm to serum osmolarity and that the multiplicative factor for ethanol in formulas should be 0.27 (1/3.7) or 1.25 if using SI units.
Purssell RA et al. Derivation and Validation of a Formula to Calculate the Contribution of Ethanol to the Osmolal Gap. Ann Emerg Med 2001; 38(6): 653-659. https://doi.org/10.1067/mem.2001.119455