Question: Our anesthesiologist provided anesthesia while another physician inserted a vertebral artery catheter. We thought the catheter insertion would be coded as 36100 and crossed that to anesthesia code 00350. We reported the 00350 with diagnosis Z99.11. The payer denied the claim; what did we do wrong? Utah Subscriber Answer: Sometimes surgical/procedure codes crosswalk to more than one anesthesia code because of the different scenarios that might be involved. That’s the case with 36100 (Introduction of needle or intracatheter, carotid or vertebral artery), which crosses to both 00350 (Anesthesia for procedures on major vessels of neck; not otherwise specified) and 01916 (Anesthesia for diagnostic arteriography/venography). Since the payer denied 00350, check with your anesthesiologist to see if 01916 might be more appropriate. Also take another look at your diagnosis assignment. The diagnosis you chose, Z99.11 (Dependence on respirator [ventilator] status) is not an adequate primary diagnosis for the procedure performed. ICD-10 lists Z99.11 as a secondary diagnosis, which means it supports another diagnosis that is more detailed. Talk with your anesthesiologist about this as well; he or she should have a more definitive diagnosis in the operative notes that you can assign as the primary diagnosis with Z99.11 as secondary.