Bolus 25mL/hr

No.  If you have a bolus running at 999 mL/hour and Y-site an antibiotic at 200 mL/hour below the pump, then the hourly amount of fluid being delivered, while the antibiotic is infusing, is 1199 mL/hour. 

However, what is your question or concern?

The infusion rate of the combination would be 1199. The antibiotic will not complete in 10 minutes. The antibiotic will still be infusing at the 200 mls per hour. Theoretically the tiny drips that get combined at the Y site would infuse "faster" but only drip wise, not the whole content of the antibioic. 

20 minutes ago, CalicoKitty said:

The infusion rate of the combination would be 1199. ...

Thank you.  You stated this much clearer than I.

I usually attach the slower running med directly to the pt's IV. Then I connect the faster running med/fluids to the other line, at the port closest to the IV. That way the slower running drip does not cross paths with the faster and be possibly pushed in faster. For that small amount of tubing before the IV, the faster fluid is run at the slower rate. As long as the two things are compatible I've never had a problem. I get what you're saying that if you connected potassium that needs to be at 50ml/hr up high on the tubing of a bolus running 999, theoretically the K could be pushed in too fast. I've seen people do this and haven't seen an issue, but I am careful just in case.

15 minutes ago, LibraNurse27 said:

... I get what you're saying that if you connected potassium that needs to be at 50ml/hr up high on the tubing of a bolus running 999, theoretically the K could be pushed in too fast. I've seen people do this and haven't seen an issue, but I am careful just in case.

No, it isn't.  The potassium is being delivered at 50 mL/hour regardless of where it enters the IV line.

38 minutes ago, chare said:

No, it isn't.  The potassium is being delivered at 50 mL/hour regardless of where it enters the IV line.

hmm, makes sense! Because that IV channel is pushing that med in at that rate. Sometimes I get really confused about this topic, what I put above is what I do just in case, but what you are saying totally makes sense, and now I feel I don't have to stress over it so much ? thanks!

Let's say you had a 10 mEq/100 ml K+ bag. You program this on its own pump to go in over 1 hour (so, rate 100 ml/hr). That is how fast that pump is going to pump that medication, period. And it is going to take 1 hour.

If your potassium were somehow going at the bolus rate of 999 just because the fluid in the bolus line is being pumped at 999, then your K+ would be gone in roughly 6 minutes. ? And yet....it is not. ? Because it is  infusing (being pumped) at 100 ml/hr regardless what the other line is doing.

Thank you so much for y’all’s explanations!  It has helped a lot! You’re right.  The “secondary” or “add on” wouldn’t run out at a faster rate.  I do believe that once it enters into that primary line, it’s shoved into the vein with the IVF, much like an IV push would be. 

28 minutes ago, Leah8183 said:

it’s shoved into the vein with the IVF, much like an IV push would be. 

And just like you control the rate of administration of your IV push medication by controlling the rate at which you push medication from the syringe into the line, your IV pump with second med controls how fast that med goes into the line.

If you had a syringe of morphine that you pushed carefully over 2 minutes, then 2 minutes is how fast the patient got the dose of morphine whether you pushed it into a saline lock or a running IV line.

2 minutes ago, JKL33 said:

And just like you control the rate of administration of your IV push medication by controlling the rate at which you push medication from the syringe into the line, your IV pump with second med controls how fast that med goes into the line.

If you had a syringe of morphine that you pushed carefully over 2 minutes, then 2 minutes is how fast the patient got the dose of morphine whether you pushed it into a saline lock or a running IV line.

Right.  The pump is controlling the rate.  The flow of one line is 999, while the flow of the other is 200.  Once the 200 line gets into the 999 line, everything in the 999 line is, then, being pushed in at 999, from the Y site on.  CalicoKitty explained this concept well

Gotcha. Yes, relatively miniscule amounts. The bolus line is running at 16.65 ml/minute while drops are being added into it at a rate of 1.6 ml/min. The second pump is adding medication to the line 10x slower than what the primary is pumping. Not trying to tell you what you know...just writing it out in various ways for others to understand. This is not an uncommon misunderstanding so it's good that you brought it up. ??

And your title was very clever. See --- you got what you asked for with that. ?

Not to muddy the waters but I will point out that if a bolus is running via gravity (with or without a pressure bag), Y-siting anything critical into it isn't a great idea because the critical drip can back up into the bolus tubing (path of least resistance if the patient bends their arm or whatever) and thus your flow rate of the drip will be inconsistent. Sure, the pump controlling the critical gtt is running at a consistent rate, but it doesn't know where the fluid is going.  Imagine if 30mL of Levophed backed up into the bolus tubing due to a temporary occlusion and then all flowed in at once when the occlusion was removed...while the gtt isn't flowing in, you're tritrating it up because the BP is dropping, and then all of a sudden the BP spikes when flow is restored. 

 In addition to all the points made above, IV pump tubing tends to have check valves to prevent backflow, while bolus tubing does not. This might be part of why you've been told not to Y into a bolus.