that is a tricky question to answer but gettting it right can either make or break your back .....literally. If we are talking critical emergency i would pull the call light out of the wall first and shout "help Help HELP!! in our facility the call light being yanked sends a loud shrill bell alarm that can be heard up and down the corridor. Do this so you do not have to leave the pt to call into the hall for help. If nobody comes than its time to start looking for another place to work. Plus letting the bells and whistles do the calling out for help allows you to be removed from the "asking" scenario and those who continue and refuse to help will be obvious to all of  the rest of us who do run in to help you and the patient.  Confrontation of those who run the other way does nothing usually except make those who don't really want to be nurses in the first place get defensive and nasty . This does nothing for you and all of us already pretty much know who is a wanna be and who isn't . Confrontation though can be quite satisfying temporarily .... but that's pretty  much it . I doubt you will see much change about their poor performance in a critical emergency.