They're probably being extra safe (which is good), but low sodium levels and anesthesia don't mix very well. Have you ever been told that you may have Hyponatremia? This could be the reason they're being extra careful. Lots of information available on this condition.
With the abundance of salt found in today's prepared food, I would think that practically everyone gets at least their minimum allowance of it. Have you condsidered that your hormonal cycle could have something to do wit it?
I am having a colonoscopy under anesthesia my sodiun is low and they want to recheck my blood before procedure why is this a concern