I don't mean to pick apart a vent, so I apologize for that, but I do have a couple of questions (maybe they'll help in the future?).
I know you may not know the answers to some of these, but...why was the trough drawn THAT long after the med went up? If it were, say, 10 minutes, I can understand that, since there is a 30 minute window for meds, and a 2000 dose can go up at 1930, for example. Where I work, troughs are scheduled (I believe) 15 minutes before the dose is scheduled to be given, so using that scenario (again, just an example):
Vanco is scheduled for 2000
Trough is ordered for 1945
Nurse hangs med at 1930
Trough drawn 15 minutes in to med infusion
The nurse SHOULD be aware of when the trough is scheduled for. It's common knowledge that troughs are drawn on that med in general, usually on the 3rd or 4th dose, and every x number of doses afterwards. I don't know how every facility provides the nurse with their info for the shift, but where I work, on our profiles, there is a heading for lab work, so it would not be hard to find. IMO, if someone is on Vanco, you make it a point to find out when the next trough is due, to know if it coincides with the dose you have to give. Conversely, our lab staff will usually give us a heads up when they're going to be drawing a trough, since they know a med might go up a little sooner than the scheduled time. In your scenario, it's the 40 minute window that really stumps me. Either the trough was drawn very late, or the med was hung really early. Or whoever scheduled it in the first place made an error (or, someone rescheduled the administration time, without changing the corrseponding lab draw times).
Anyway. Sorry to overanalyze (I tend to do that). Regardless of the situation, that nurse's reaction wasn't appropriate, and you should not have been asked to remove the value from the computer (I can't believe anyone would ask that about ANY lab value!). Even if they think a result is erroneous, it is what it is, and then steps need to be taken to fix it...whether it's, inform the doc and schedule another trough with the next dose, in a case like this, or whatever. No nurse, I don't think, can have the authority to say to remove a lab result...which, I take it, would be basically "discarding" it, and making it like it never existed. Not ok.