Not 100% sure but 99% sure that Medical item will not trigger Use an Item
Use an Item in your adventures. I have use as Bacta Patch, Healing stick, Bacta refill a few times and nothing of that "field" trigger that achievement.
I can't remember how I got that achievement as it as so long ago but I have only ever used Bacta patches and healing sticks on myself. I did heal someone else with a bacta patch though, but I'm sure that doesn't make a difference who you use it on.