Human learning during general anaesthesia and surgery.
R I Block, M M Ghoneim, S T Sum Ping, M A Ali
British Journal of Anaesthesia February 1991 DOI: 10.1093/bja/66.2.170 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational study Peer reviewed |
|---|---|
| Sample size | 72 |
| Population | Women undergoing surgery under general anaesthesia |
| Measures | Behavioural Suggestions tests, World Completion tests, Nonsense Word tests |
| Key findings | Three postoperative implicit memory tests showed apparent unconscious retention of auditory information presented during general anaesthesia, with suggested body parts touched longer (2.5 vs 0.2 s), more words from a played list (0.48 vs 0.27), and greater preference and recognition of frequently played nonsense words (56% vs 46% and 62% vs 48%). Retention did not vary with anaesthetic method, which the authors say suggests some information processing continues during adequate general anaesthesia. |
Abstract
To determine if learning occurs during general anaesthesia, 72 women undergoing surgery were given postoperative implicit memory tests in which performance could be influenced by auditory information presented during general anaesthesia. Two methods of anaesthesia were used: nitrous oxide and opioids (n = 24) or nitrous oxide and isoflurane (1, 1.3 and 1.5 MAC for n = 12, 24 and 12, respectively). Three tests showed some retention, apparently unconscious, of information presented during anaesthesia: in Behavioural Suggestions tests, patients who were instructed during anaesthesia to touch a particular body part (ear or nose) during later questioning touched the "correct" (suggested) body part longer than the "incorrect" (not suggested) body part during a postoperative interview on the day of surgery (means 2.5 vs 0.2 s); in World Completion tests, patients shown a page containing the first three letters of words and asked to give words beginning with those letters gave more words from a list that had been played during anaesthesia than from a list not played (means 0.48 vs 0.27 words); in Nonsense Word tests, patients who were played different nonsense words between two and 16 times during anaesthesia preferred and guessed more accurately those that had been played most often (16 times) relative to those played less often in subsequent preference and recognition tests (means 56% vs 46% for preference and 62% vs 48% for recognition), while showing no such patterns in additional control tests. Learning did not vary with the method of anaesthesia, as might have been expected if learning was a monotonic function of brain depression. Some information processing functions of the brain evidently continue to function during adequate general anaesthesia.