Reducing Narcotics in NICU

Hi there

I would be grateful if someone will help me in understanding how to calculate cumulative dose of Narcotics received by baby while staying in NICU.  

A baby in NICU can have narcotics/sedative infusions, intermittent injections for many days to week depending on surgical or medical condition. To reduce Narcotics use in NICU , I need to reduce the number of days the babies were on Narcotics and also to reduce the cumulative dose per kg. To retrieve data, from system suppose a baby receive 3000mcg total morphine in 60days, so to calculate per kg dose which weight should be taken. Definitely babies gain weight during these 2 months period.  I Will be oblige if someone explain with example.

Many thanks for reading