Equations of Khajuria and Krahn for Calculating Serum Osmolality

Description

Khajuria and Krahn developed 2 equations for predicting serum osmolality based on serum solutes, including the concentration of ethanol. The authors are from St. Boniface General Hospital and the University of Manitoba in Winnipeg, Manitoba, Canada.

Parameters:

(1) serum sodium in mmol/L

(2) serum potassium in mmol/L

(3) serum glucose in mmol/L

(4) serum urea in mmol/L

(5) serum ethanol in mmol/L

formula 1 for calculated serum osmolality in mOsm per kg water =

= (2 * (sodium concentration)) + (1.15 * (glucose concentration)) + (urea concentration) + (1.2 * (ethanol concentration))

formula 2 for calculated serum osmolality in mOsm per kg water =

= (1.86 * (sodium concentration)) + (1.86 * (potassium concentration)) + (1.15 * (glucose concentration)) + (urea concentration) + (1.2 * (ethanol concentration)) + 14

Osmolal Gap in Normal Patients	no ethanol present	ethanol present
Formula 1	-6.7 to 8.2	-4.0 to 6.5
Formula 2	-8.0 to 6.5	-5.0 to 4.8

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Equations of Khajuria and Krahn for Calculating Serum Osmolality

Description

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