Absence of explicit and implicit memory in unconscious patients using a TCI of propofol

Abstract

In our group of young ASA I/II patients, in the absence of any noxious stimulus, no implicit or explicit memory was found when the calculated concentration of propofol using a Diprifusor was maintained at the level associated with LOC.

Is priming during anesthesia unconscious?

“…Category generation and word association tests did not reveal any implicit memory, regardless of whether the patient had been able to respond to command during surgery or not. Similar results were found by Lequeux, Cantraine, Levarlet, and Barvais (2003) who anesthetized patients to loss of response to verbal command prior to surgery, and then played a word list. There was no evidence for memory using a word stem completion task, forced choice recognition test and free recall test.…”

Absence of implicit and explicit memory during propofol/remifentanil anaesthesia

“…It is still unclear whether this implicit learning may occur when subjects are unconscious or whether short periods of awareness are responsible for this memory [1]. We have showed in a previous study [3] that implicit recollection was eliminated when young ASA I/II patients had lost consciousness when propofol was used alone in the absence of a surgical stimulus. However, when propofol is combined with an opiate, loss of consciousness may appear at a much lower concentration of propofol because of drug synergy [4].…”

“…A group of 20 patients from a previous study [3] was used as a control group. These patients answered the three memory tests after propofol anaesthesia without having previously heard the list of words.…”

“…Three different memory tests, as described by Light and Singh [10] and adapted to French [3], were used to study implicit and explicit memory under anaesthesia. These were the word stem completion test, the free recall test and the forced-choice recognition test.…”

“…It is still unclear whether this memory can be processed by unconscious patients or whether it is caused by short periods of awareness [1]. In a previous experiment, implicit or explicit memory could not be found when consciousness was lost using propofol as sole anaesthetic agent [3]. However, propofol is often administered with an opiate, e.g.…”