Mary Costello founded the Cincinnati General Hospital School of Nurse Anesthesia (later the University of Cincinnati School of Nurse Anesthesia) in 1945 and served as its director for 27 years. Costello was one of the first nurse anesthetists to become adept at the administration of regional anesthesia and instructed nurse anesthetists from around the country in regional techniques.
Costello also dedicated a large part of her career to the AANA and the Ohio Association of Nurse Anesthetists. She served on the AANA Board of Trustees in 1949-1951 and 1953-1956, and she was AANA President in 1963-1964. She served on many AANA committees including the Curriculum Committee and the Government Relations Committee. She was awarded the AANA’s Helen Lamb Outstanding Educator Award in 1987. Costello was president of the Ohio Association of Nurse Anesthetists in 1947-1948 and was granted life membership in 1970.