Depth of Anesthesia on Implicit Memory

Purpose of this study is to see if different levels of anesthesia have an effect on hearing spoken words without awareness of having heard them or anxiety after surgery.

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 (Spielberg's 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).

• Anesthesia, General
• Memory

• Behavioral: Mini-mental state exam
  For subjects > 60, this exam will be administered pre-operatively.
• Behavioral: Spielberg's State-Trait anxiety test
  Operative phase of study: Spielberg test just before being taken to the operating room.
  Other Name: SPS test
• Behavioral: Spoken word-stem completion test
  After discharge from recovery but within 24 hrs. post surgery, this test along with the anxiety test will be administered.
• Device: Bispectral Index Monitor
  The physiologic monitor is used intraoperatively to assess surgical anesthesia
  Other Name: BIS Monitor
• Other: Audio File
  Playing an audio file (a list of spoken words) via headphones under general anesthesia during the surgical procedure.

• Experimental: 1
  Target BIS 40
  Interventions:

  • Behavioral: Mini-mental state exam
  • Behavioral: Spielberg's State-Trait anxiety test
  • Behavioral: Spoken word-stem completion test
  • Device: Bispectral Index Monitor
  • Other: Audio File
• Experimental: 2
  Target BIS 60
  Interventions:

  • Behavioral: Mini-mental state exam
  • Behavioral: Spielberg's State-Trait anxiety test
  • Behavioral: Spoken word-stem completion test
  • Device: Bispectral Index Monitor
  • Other: Audio File

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