Fig. 1. Flow diagram of logical steps applied by the Anesthesia Billing Alert System (ABAS) for the placement of an epidural catheter. The appearance of a statement in the anesthesia record indicating the placement of an epidural catheter prompts a search by the ABAS for documentation by the staff anesthesiologist indicating that he either placed the catheter himself or medically directed its placement. If such documentation is not found by the end of anesthesia care, a documentation error has occurred.