Depth of Anesthesia on Implicit Memory

Amnesia (lack of recall) is one of the most important goals of general anesthesia. Inadvertent free recall during a major surgical procedure is not only inhumane, but also predisposes the patient to morbidity such as post-traumatic stress disorder. Therefore, it is standard practice among anesthesiologists to inquire about free (explicit) recall during a post-anesthetic visit.

Free recall requires a functional long term memory. Historically, lack of free recall during general anesthesia has been regarded as complete absence of long term memory activity. However, recent evidence suggests that the relationship between general anesthesia and memory is more complex than previously thought.

Objectives of the proposed are twofold: (1) to test the presence of implicit memory under two different planes of surgical general anesthesia in elderly males (55-90 years old) during a uniform surgical procedure (urologic procedures via transurethral approach) (2) to compare the pre and postoperative anxiety levels as a marker of clinical significance of operational implicit memory function.

The study is divided into three phases: pre-operative, operative, and post-operative.

Pre-operative phase will consist of a cognitive function test (mini-mental state exam). This will be administered at the urology or pre-operative anesthesia clinic visit, after obtaining the informed consent of the patient.

Operative phase will start with a baseline anxiety test (Spielberger state-trait anxiety test) just before being taken to the operating room. This will be followed by playing an audio file (a list of spoken words) via headphones under general anesthesia during the surgical procedure.

Post-operative phase will have of a spoken word-stem completion test (just before discharge from the hospital) and a repeat of the anxiety test mentioned above (2 to 3 weeks post-operatively).

Inclusion criteria

• Persons signing informed consent
• Elective general surgery for orthopedics (external or internal fixation) or urologic (transurethral)
• Literate
• Native English speaking

Exclusion criteria

• Hearing impaired
• History of cognitive dysfunction
• Subjects requiring post-operative sedation for any indication