I'm doing a preceptorship in home health care. When using the CADD ambulatory pumps, my preceptor sets the reservoir volume above the volume of the infusion bag (i.e. if the bag is 250cc they will set the pump at 265cc). My preceptor's rationale is that then the pump won't start beeping as soon and will give the nurses more time to get to that client's house. However, what I am wondering is whether or not this poses a risk for the line to run dry and become air-filled? If the pump thinks there is more fluid in the bag then won't it pump the air into the line?
Regardless of what you set the volume to be, once air gets to the pump it's going to alarm, so I'm not sure how it really helps unless you're very sure that there really are at least 265mls in the bag and that you haven't lost any of that to priming volume.
The bigger issue is that for some home IV medications like remodulin or dobutamine or milrinone, it's extremely important that the infusion not be stopped for periods of time, so it doesn't help to just keep the pump from beeping for a longer period of time, the bag must be replaced before going dry.
But what I am saying is that if the bag is 250cc they set the reservoir volume at 265cc - a higher volume than what is actually even in the bag. I realize that there is no actual danger of an air embolus to the client as the pump will alarm. I'm thinking that air will be pumped into the line as far as the pump (at which point it will alarm), which just creates more work as then the air needs to be cleared from the line. The pump is designed to stop once its reservoir volume becomes zero, which is a feature that avoids air being pumped into the line. However, if the reservoir volume is being set higher than what is actually in the bag than this feature is being negated. That's my thought process anyhow. I guess I just feel like the way my preceptor approaches this is counter intuitive and illogical.
That’s not the way I would do it; I personally set the volume as the bag volume minus the priming volume.
That being said, you can just back prime the pump when you get the new bag hung. Many pumps have a back prime option; if not, you just manually back prime. It’s a slight pain, ergo, I would rather the pump stops before the distal line goes dry.
But if staffing with the agency is such that the bag is going to run dry regardless because there is no one there to change it, perhaps she is trying to give the patients a few extra minutes of not having the pump going nuts before someone gets there?
The other possibility is that she has to change to tubing at the start of the shift because it is expired regardless, so it doesn’t really matter if there is air distal to the pump? I don’t know. There’s not enough info to say if it’s truly bad practice...
I just wouldn’t do it on the off chance the next nurse doesn’t backprime or reprime, hangs a new bag, and the bad luck gremlins show up and the pump magically malfunctions and manages to mystically run by gravity and bolus the air. Obviously very unlikely, but that would just be my luck.
Ive been up since 3 AM so I’m hoping that made sense!!!
Last edit by PixieRN1 on Sep 24
That does not make any sense at all..What determines the time a bag will go dry is the total volume in the bag or cassette and the rate at which it is set and if applicable the small KVO rate between doses. If you have 250 ml and 250 mls is delivered the pump will alarm once it runs dry even though you have set the volume higher.Its best just to set the volume accurately and teach the patient or caregiver how to aseptically disconnect and flush whatever type of VAD they have to keep it patent until the nurse gets there or get there on time!
If anything, the bag volume should be HIGHER than the reservoir volume. I know my Pharmacy typically overfills bags by 100 mL.
And, CADD pumps, at least the Prizm model that I deal with, do not have built in air detectors. They have auxiliary ones that can be installed but in my experience these are rarely used. I did have an experience once where we provided a CADD pump to be used with a study drug. The study drug was mixed in the hospital's pharmacy, not our pharmacy, and they estimated the volume incorrectly and the pump was set to administer 1100 mL. The bag only contained something like 1014 mL, the Pharmacy did not remove the air from the bag when they mixed the study drug and when the bag ran dry, the pump continued to pump air.
The Infusion Pharmacy that provides these pumps doesn't set and lock them though? I currently work for an infusion pharmacy and all of our pumps are programmed and locked in the pharmacy prior to being delivered to the patient.
You do have to know if you have an air alarm on the ambulatory pump you are using. I have used CADD pumps but mostly I use Curlin pumps now.
I hated the Curlin pumps, we just switched to CADD and I love it. I don't understand the rationale for overstating the bag volume, either. The CADD pump works with its own tubing, so once you prime it, it will subtract the amount in the tubing from the total volume. Setting the bag volume at a higher than true value won't negate that. And this will also cause problems with bookkeeping. Once the bag does run dry, you're "wasting" an additional 15mL of narcotic.
Maybe it's because you'll get a "low reservoir" alarm later then it normally would and if a nurse is definitely due to arrive they can change it so it doesn't alarm at all. Assuming a person can actually be there in time to change the drug. Personally I think I'd just keep the pump to whatever volume is stated minus priming volume (assuming the pharmacy has filled the bag correctly/as stated on label).
Otherwise it depends on how your pumps work and the work setting. Ours in the hospital automatically subtract the priming volume. I wouldn't see the need to set the CADD for a higher or lower amount, since I'm there to hear the automatic "low reservoir" alarm then "empty" beep. I want it to be exactly the amount especially when dealing with narcs since I don't like wasting drugs or wasting drugs, if you know my meaning.
I don't really see setting our CADDs any higher as already stated, since there would probably be an "air in line alarm" but I don't know since I've never had to deal with a CADD with air in the line.
Short answer, it depends on your practice and how you do your work. That's how that nurse does it doesn't mean you have to do it that way (except during a preceptorship maybe). Nursing isn't an always one size fits all type of thing.
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