Dr. Oppenheim began the appendectomy on Mrs. Quinones when she began to bleed uncontrollably. He was able to stop the bleeding but decided to stop the procedure for the safety of the patient. What modifier is used?

Modifier Code 53.

Explanation:

When an unexpected circumstances or situations occurred ( after anaesthesia)   which  threatened the life of a patient during a surgical procedure,  so that the surgery which had started could not be completed by the surgeon in this case(Dr Oppenheim),the code usually employed to identify the particular surgery is called Modifier 53.

It can also  be used with diagnostic codes.