What is total parenteral nutrition (TPN)? Total parenteral nutrition (TPN) is a way to give nutrients to your baby through a tube (catheter). This tube is inserted into a vein. The tube sends liquid nutrients directly into the blood. The blood carries the nutrients to your baby's tissues and organs. The nutrients don't have to go through the digestive system. TPN is used if your baby can't get enough nutrition by mouth or through a feeding tube. Your baby can get TPN as long as needed. Your baby may need special care, such as being in the neonatal intensive care unit (NICU).