Hydration is the single best intervention to decrease the potential for renal impairment secondary to contrast, and contrast is the third leading cause of kidney failure in hospitalized patients. At my facility, we look up the GFR the day before CT.
GFR 50-60 we change the contrast to iso-osmolar i.e. Visipaque 320.
GFR 40-50, I call the pt. physician and ask them if they want to (a) cancel IV contrast and/or do another study (b) Use renal protection measures such as mucomust 600 mg bid x 3 days the day before, day of, & day aftere CT; or IV hydration in their preferred amount. Lately, they are ording D5W 500 ml with Bicarb 50 mEq to infuse over 5 hours. This is very impracticle for me, so I set them up to get their IV through the infusion or same day services department.