I have read that RCI accomodates passengers who are on peritoneal dialysis, which requires even larger and heavier bags of treatment solutions, so I am thinking this is possible (I am a Registered Nurse).
I would first email special_needs@rccl.com and confirm exactly what they require: physican documentation, prescriptions, supply list, etc. Ask if there would be customs issues getting clearance for the TPN and supplies.
As the previous poster mentioned--I am thinking your wife has reliable central line access of some kind and you are knowledgable in managing any unexpected complications with it.
Best of luck and hopefully things go smoothly for your cruising needs!