Use the Measured Sodium Concentration!

• During a recent shift, a question arose regarding whether to use the measured or corrected sodium to calculate the anion gap in a critically ill patient with DKA.
• Recall that the anion gap provides an estimation of unmeasured anions - in this case acetoacetate and beta-hydroxybutyrate.
• Glucose is electrically neutral and therefore does not affect the anion gap.
• When calculating the anion gap in a patient with DKA, use the actual (measured) serum Na, rather than the corrected value.

References

Beck, L. Cleveland Clin J Med 2001;68:673.