[2][3] After receiving his bachelor's degree, he joined a psychoanalytic study club, which became the Chicago Institute for Psychoanalysis and underwent his own analysis.
[3] Kroger demonstrated the use of hypnosis on a breast surgery procedure on closed-circuit television for a national meeting of anesthesiologists in the removal of a benign growth and on another occasion in 1956 in Edgewater Hospital.
Kroger carried out the "hypnoanesthesia" at Edgewater Hospital, where the patient's thyroid was removed in an hour-long operation.
Following the surgery and after being de-hypnotized, the patient stood up from the gurney, asked for a sip of water and walked to her wheelchair to return to her room.
Kroger also participated in anesthetizing an expectant mother in Hypnosis in Obstetrics, which was also the first occasion on which hypnotism's use in delivery was filmed.
Both educational movies were intended as teaching aids at medical schools, hospitals and scientific meetings[3] and were produced by Wexler Films (now out of business).
Through the text and his own seminars put on by the ASCH, he changed the perception of hypnosis as being a novelty to a legitimate and respected medical option.
The integration of his research and experience led to a collaboration with co-author S. Charles Freed in Psychosomatic Gynecology, Including Problems of Obstetrical Care, a textbook which argued that hypnosis had a place and merit in the medical field.
He also consulted for the Los Angeles Police Department and other law enforcement agencies in the investigation of major crimes.
[6] Kroger maintained a private practice in Beverly Hills and Palm Springs, California from 1960 until his retirement in 1986.