http://www.aafp.org/fpm/2004/0100/p22.html
Emergency office services
Q:Can you explain the proper use of CPT code 99058, “Office services provided on an emergency basis”? Does it require the physician to be called out of a room in which he or she is seeing another patient?
A:Code 99058 involves the physician interrupting his or her care of another patient to deal with an emergency. The winter 1994 CPT Assistant states that “if a patient presents at the physician’s office and requires unscheduled emergency care, code 99058 is reported in addition to the other services provided. This is reported for those office patients whose condition, in the clinical judgment of the physician, warrants the physicians interrupting his/her care of another patient to deal with the ‘emergency.’ This code is not reported when the doctor’s practice is to have urgent care slots available in the schedule and patients are ‘fit in’ to the schedule.”
However, neither CPT nor CPT Assistant states that this interruption necessarily extends to being called out of the room in which the physician is currently caring for another patient. For example, a physician could “deal with” an office emergency by providing initial instructions to the clinical staff member who interrupts the physician’s care of another patient to advise him or her of the emergency. The physician could then treat the emergent patient after completing his or her care of the current patient. In this case, the intent of code 99058 would be met, even though the interruption of the physician’s care of another patient did not include leaving the exam room before the encounter was complete.
Note that since CPT considers 99058 to be an “adjunct to the basic services rendered,” it should not be submitted alone; rather, it should be submitted in addition to the other service(s) you rendered to the patient. And Medicare and many other payers consider 99058 bundled with the other service(s) you provided to that patient on that date, so they will not separately reimburse for 99058.