Hi. Yes, IV Fluids for 2 or 3 days are always an option - and in most cases of severe kidney failure, the best option. To further help your guy please try feeding very small meals more often - so up to 6 small meals a day separated by a couple of hours - so the total intake for the day equals the recommended amount of food intake for such a big dog. This will help relieve the stress placed on the kidneys, and make it easier for the damaged organs to deal with the by-products and toxins.
Do you know what his current blood results are like (particularly creatinine, BUN, phosphorus, calcium, sodium, potassium, RBC, WBC, amylase)?
Tony