Quote from kimber1985
ok, so to keep a line primed, i suck the air out of it and put in 45 mls? i am confused. you are saying that sucking the air out makes a vaccuum that will keep the pump from pushing out the last 5 mls? but the pump still knows not to suck out 5mls?
most of the time when i hang an ongoing piggyback the line is still primed and i just stab it. quick easy no fuss or muss. otherwise you are repriming and getting air bubbles out and losing med anyway. i've only back primed once with a nurse, but not sure i could do it alone. i think you just lower the line and let the primary fluid run in?
i think you are giving way too much credit to the "smart" iv pumps.
they really arn't that smart.
the pump determines what rate a fluid will run, and for how long. gravity and pressure determine the rest.
by hanging the secondary higher, you make the pressure in the secondary line higher than the pressure in the main line. it (the secondary) will run until the fluid level is low enough that the pressure in the primary is higher.
the pump is going to deliver the programd rate over the programmed volume. when that voume has been infused, it will switch to the "old" (primary) rate, for the duration of the primary volume. the pump has no idea what bag it is pulling from.
for example, say you have maintenance fluids running (the primary), lets say ns at 75 cc/hr. you hang ancef, a 50 cc piggyback, that is supposed to go in at 100 cc/hr (over 1/2 hour). so you plug the ancef in to the secondary port on the primary tubing. you program the pump for "secondary" at 100 cc/hr over 50 cc. you hang the ancef higher than the ns. the pump is goin to deliver 100 cc/hr for 50 cc, and is then going to revert to 75 cc/hr. this is true even if you forget to "undo" the roller clamp on the ancef, effectivly keeping it from infusing. in this case, the primary will infuse at a faster rate for 30 min, then go back to the original rate.
am i making any sense?
when i talk about "back priming," we mean spiking the ancef, connecting it to the "secodary" port on the main line, and lowering it. this will cause the maitenance fluids (ns) to flow into the secondary tubing, instead of into the patient. this will push all of the air out of the secondary tubing and into the piggyback bag.
when i talk about getting the air out of the piggyback bag, i mean one of two things. if i have "fresh" tubing, then i spike the bag "up-side down," and push the air (that is at the top of the bag) out first, and in to the tubing. the fluid then follows. this creates an "air-free" bag, so that air cannot be "sucked" into the tubing at the end of the infusion.
i have a feeling that this is difficult to follow -- it is much easier to show someone how this works than it is to describe it in writing. let me know if i can clarify anything. i hope i don't have you hopelessly confused. the main point that i want to get accross, though, is that the pumps are not as smart as they seem.