What approaches do you take to prevent worsening kidney function for patients with chronic kidney disease who have an upcoming outpatient CT scan with iodinated contrast?  

If CT is really necessary, if not very high risk just encourage moderate oral hydration before and after. May hold diuretics if this can be done safely. If very high risk try to get IV saline for a few hours prior. 

I will schedule them for outpatient saline infusion around the time of the contrast. 

Rather than admit for IV Saline, I tell them to have a bowl of soup with extra salt for three days prior to the procedure, hold any diuretics day prior, no NSAID, and also hold ACE and ARB. If have CKD, I also give a statin and SGLT 2 inhibitor.

I ask them to hold diuretics, ACEI/ARB, MRA and SGLT2i a day of the procedure as long as that can be done safely. If very high risk (mostly advanced stage 4), I recommend peri-procedure IVF as long as there is no risk for acute volume overload (low EF, prior CHF hospitalization, etc). 

Hold diuretic day of study and give IV hydration prior.