Running maintenance and IVPB simultaneously

No, he isn't.

I thought so, crane! Had a co worker tell me that I had to slow down the maintenance to the same rate as the Secondary line so to avoid giving it too fast.

Since modern pumps use a single tube or line per pump channel you cannot run simultaneous infusions on a single channel. You can only run sequential or piggyback medications.

If you need to run a slow medication but still maintain a more rapid fluid replacement, the slow medication must run on a second channel and then be connected to the y-connector below the pump (which you did). The fluids now run in parallel and the primary fluid may need to be rate adjusted to compensate for the added secondary pump. For example if your overall rate of fluid replacement is 180 mls/ hr and you now add a second fluid at 50 ml/ hr you would slow the primary rate to 130 mls / hr until the secondary is complete.

Your coworker was wrong about adjusting the K rate. Imagine I'm the secondary K pump and I'm handing you blocks of wood that you are throwing into the pool. The rate that you throw them is the primary line rate. But regardless of how fast you throw them, I'm only giving you so many per minute. Therefore there are only so many entering the pool per minute regardless of whether you throw them fast or slow.

This is all explained here by Lippincott...

I.V. ROUNDS: Intermittent I.V. infusions in acute care: Special considerations