I am sure your hospital is big and providing ICU care. For that reason, Admin asked to establish PN service. As the any hospital having neonatal and pediatric, surgical, and critical service, the hospital has to provide PN service. As these patient categories are badly need for PN anytime. in my opinion, there is no minimum number as you may expect unexpected number of PN prescribing depend on the situation.
You have the options to provide either customized or ready made PN but you have neonatal and pediatric service, you may need to focus on customized PN ( standard or tailored formula).
You need to create SOPs related to safe practice for PN and IV fluid first, establishing well defined procedures for safe PN compounding, well trained and skilled pharmacists, expert PN prescriber, and enough manpower either to compound PN manually or by Automated compounding device (ACD)
Roughly, preparation PN manually may take at least 45 minutes to one hour while using ACD may take 10 to 15 minutes per bag.
The option for choosing ACD is depending on the number of PN like more 10 bags, the budget of hospital (the average cost varies depending on the type of machine) Also supplies to ACD like tubing sets and inlets, , and others.