Serum ethyl alcohol levels and osmolal gaps

We compared 56 paired measurements of osmolal gaps and serum ethyl alcohol levels in 15 anesthetized dogs. We then repeated these comparisons after correcting the osmolal gaps for the preceding (the administration of ethyl alcohol) difference between measured and calculated osmolalities. No statistical differences were observed between ethyl alcohol levels and either uncorrected or corrected osmolal gaps. However, uncorrected osmolal gaps differed from ethyl alcohol levels by less than 5 mmol/L in 39.3% of the measurements and by more than 10 mmol/L in 19.6% of the measurements. Corresponding percentages for corrected osmolal gaps were 94.6 and 0 respectively. Thus uncorrected osmolal gaps offer a rough screening test, whereas corrected osmolal gaps offer accurate predictions of serum ethyl alcohol levels.