Quote from ktliz
I'm not sure what you mean by having the stopcocks open to both the CVP and the infusions. If you are getting a CVP reading, the stopcock should be turned "off" toward the infusion. If you are infusing, it is off toward transducer/pressure bag, and if you are zeroing the CVP it is off to the patient. The CVP will not be accurate while anything is infusing through it (other than the pressure bag).
There is a fourth option of having the stopcock turned off to nothing and all three ports open. This will allow you to infuse medications, while still obtaining a cvp number (which is inaccurate as the OP pointed out) with a crazy waveform sometimes. I agree, in that I just turn the CVP off when it's not in use accurately. Some say that it will help you trend the CVP if you leave it open all the time, but I disagree. And often, nurses forget that their number isn't accurate and pull over their inaccurate CVP numbers into the chart without thinking.
As far as meds traveling into the CVP... I'm almost certain this doesn't happen, although I don't have any research to back that up. Because the pressure pack is on the other end, it should prevent any backflow of medication. Also if there was a significant amount of backflow, it would reflect in your CVP number because the CVP would theoretically pick up that pressure and give you a number for it!
In my opinion, it's just best to leave it off like ktliz does, this ensures no backflow, and prevents anyone from treating inaccurate CVP numbers. What is the benefit of leaving the CVP open? There really isn't any.