There wasn’t IV Tylenol when I practiced. But respiratory depression remains real, as does the effect on MAP with morphine, ..mif they still give morphine now. Many more prems undergo surgery now .. they are lighter and younger too. The procedures are more complex and invasive. The IV route, esp. central, is preferable for all meds because tiny stomachs don’t absorb drugs predictably. As to what you, Ax, questioned, NICU & PICU nurses (those with experience, that is) are pretty astute picking up pain signals with neonates. Sometimes it’s vital signs, sometimes it’s posturing, cries or lack thereof, sweating, grimacing, facials, lots of stuff. Knowing the babe shift to shift, their changes in behaviour, knowing the parents too and how they see their babe hour to hour, lots of stuff.