Avoiding mineral depletion Sd phosphate, potassium, magnesium

I'd say choose your doctor well, since many could be well-intention-ed but ignorant about the re-feeding Sd. I do not see how you are going to juice or get organic produce to re-feed with in a hospital. Tips? I'd think about daily potato-with-the-peels broth for phosphates with minced fresh parsley, greens/celery for magnesium, calcium and potassium and tomatoes, eventually spirulina.
If you are concerned about the B vitamins, you could get Tangy Tangerine 2.0 have handy or brewer's yeast in powder or cube; or AOR B-complex, just in case.
Ref
http://nutritiondata.self.com/foods-011121000000000000000-w.html
http://nutritiondata.self.com/foods-011122000000000000000-w.html
http://nutritiondata.self.com/foods-011120000000000000000-w.html