Table 1

Equations used to calculate the serum molarity prior to the calculation of the osmole gap.

Equation Number

Equation


1

Osmc = 2 * Na (mEq/L) + BUN (mmol/L) + glucose (mmol/L) + ethanol (mmol/L)

2

Osmc = 2 * Na (mEq/L) + BUN (mmol/L) + glucose (mmol/L) + 1.25 * ethanol (mmol/L)


Equation 2 in effect inflates the ethanol concentration by 25% prior to calculating the osmole gap, as proposed by Purssell et al.[18]

Osmc = calculated molarity; Na = sodium; BUN = blood urea nitrogen

To convert from SI units, use the following corrections: BUN/2.8 mg/dl, glucose/18.1 mg/dl, ethanol/0.217 mg/dl

Lynd et al. BMC Emergency Medicine 2008 8:5   doi:10.1186/1471-227X-8-5

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