THE KEY IS THE DEXTROSE PERCENTAGE, as SFRN points out. The rule at my old hospital was that if dextrose was >10%, then it must be given through a central line. PPN keeps dextrose at 10% or lower, so it can be given peripherally (as Critter Lover mentions above). THE MAIN PROBLEM IS WE USE THE TERM "TPN" FOR BOTH TPN & PPN. That's what causes the confusion, I think. Thanks for this great conversation!