concurrent piggyback

correct me if i'm wrong but concurrent piggyback ivs are for when your secondary iv run for a lesser amt than the primary?

today in my clinical my pt. had a piggyback of piperacillin 50 ml so VTBI/hr is 100ml/hr
primary i believe, sorry for my faulty memory is NaCl 9% w/Kcl 20meq/ 1000ml @ 20ml/hr

my pt's other iv piggyback was a Mag Rider @100ml/hr

my other question is when do you do or when is it advisable to do a piggyback or a concurrent iv
Quote from purplemanacorrect me if i'm wrong but concurrent piggyback ivs are for when your secondary iv run for a lesser amt than the primary?today in my clinical my pt. had a piggyback of piperacillin 50 ml so VTBI/hr is 100ml/hrprimary i believe, sorry for my faulty memory is NaCl 9% w/Kcl 20meq/ 1000ml @ 20ml/hrmy pt's other iv piggyback was a Mag Rider @100ml/hrmy other question is when do you do or when is it advisable to do a piggyback or a concurrent iv

Huh?....?