I think that it has to be said very carefully with the right tone, choice of words and context. Saying somethign to the effect of "well I have other patients too" or "I have 4 other patients besides you that I need to take care of" is completely inapproapraite and out of line. But I think that there are subtle, professional ways of reminding patients and families that you have multiple people to care for and you want to make sure that everyone gets the best quality of care.
However, I have said to patients before "Now that we have gotten you some pain medication let's see if that helps you to feel more comfortable. I'm just going to check on a few of my other patients to make sure that we don't have any emergencies going on but I will be back to check on you. If there is anything that you need before I get back please press your call bell and one of the staff will be right in ASAP."
I find that usually is usually sufficient for most people but if someone requires a lot of assistance or is requesting frequent updates on what is going on then I might change the script a little bit.... In the ED a lot of patients and families want to know the result of every single test exactly as it comes in (and we all know that many of the labs or diagnostic imaging tests result at different times) so what I tend to say is this
"Right now we are waiting on the results of a few of your tests. I'm going to step out to round on all of my patients to make sure that everyone is doing ok at the moment and there aren't any emergencies that need my attention. Once all of your test results have come back or we have an update in your plan of care for today then I will come back and we can talk about it. If you need me for any reason before that time please hit your call light and one of us will be right in to help you."