Do you recommend careful correction of serum sodium to avoid osmotic demyelination syndrome in patients who are found to have isoosmolar hyponatremia in the setting of an elevated BUN level?

Urea is an ineffective osm and so if the blood is "isoosmolar" in the setting of hyponatremia but is isoosmolar because of an elevated BUN it may be isoosmolar numerically but not physiologically.

I would ignore the BUN in making my decision. I would not ignore the BG though if it were elevated.

Rapid correction of hyponatremia should be avoided in a patient with iso-osmolar hyponatremia in the setting of an elevated BUN level. Since urea is freely diffusible across the cell membrane, there is no net transcellular water movement induced by urea since the urea concentration is equal on both sides of the cell membrane. In this setting, rapid correction of hyponatremia will result in cerebral shrinkage due to the transcellular shift of water from the ICF to the ECF.