We currently use a 2 in 1 TPN system in our NICU which is the practice recommended in all the references I have read. A different pharmacist has started coming into our unit (> 25yrs experience but in adult TPN) and is wanting to change to a 3 in 1 system to allow for 30% lipid emulsion to free up slightly more volume.
I cited all the reasons for the 2 in 1 mixture that I am aware of: separate lipid has larger particle size and requires larger pore size filter of 1.2 microns, whereas a 0.22-micron (bacteria-eliminating) filter can be used for "main" bag when lipids are infused separately,