What must i ask my doctor about total parenteral nutrition?

Lots of issues: What's your underlying disease state/condition that requires that you get your nutrition from alternate means. Why won't peg tube feedings work? How many calories do you need? How much protein, fat, carbs, etc? Any other nutritional deficiencies? Do you need to lose, maintain or gain weight? Fluid status? Lots of issues to consider. Make sure a nutritionist is involved.