For observation to be an option at all the physician must write an order to admit to observation otherwise Er codes are what you have and maybe critical care.When the Prolonged Services came out in the 90s it seemed to me that they made perfect sense for ED scenarios like Asthma treatment or Kidney Stone etc with lengthy time in the ED but not neccesarily CC. But as has been stated they can't be used since ED visits have no time component. However office visits are OK since they have the optional time component if counseling/coordination are greater than 50% of the vsit. It really seems that CPT got Emergency Medicine on a technicality since those codes seemed to apply to a lengthy ED non CC visit. I was surprised there wasn't more lobbying by ACEP about this.
Another option for a lengthy stay in the ED that is not CC are the Observation Codes. However there are a number of requirements to use them and they are not add on to the ED Visit code.
Jim