Implicit Memory and Anesthesia: A Systematic Review and Meta-Analysis

Abstract

General anesthesia should induce unconsciousness and provide amnesia. Amnesia refers to the absence of explicit and implicit memories. Unlike explicit memory, implicit memory is not consciously recalled, and it can affect behavior/performance at a later time. The impact of general anesthesia in preventing implicit memory formation is not well-established. We performed a systematic review with meta-analysis of studies reporting implicit memory occurrence in adult patients after deep sedation (Observer’s Assessment of Alertness/Sedation of 0–1 with spontaneous breathing) or general anesthesia. We also evaluated the impact of different anesthetic/analgesic regimens and the time point of auditory task delivery on implicit memory formation. The meta-analysis included the estimation of odds ratios (ORs) and 95% confidence intervals (CIs). We included a total of 61 studies with 3906 patients and 119 different cohorts. For 43 cohorts (36.1%), implicit memory events were reported. The American Society of Anesthesiologists (ASA) physical status III–IV was associated with a higher likelihood of implicit memory formation (OR:3.48; 95%CI:1.18–10.25, p < 0.05) than ASA physical status I–II. Further, there was a lower likelihood of implicit memory formation for deep sedation cases, compared to general anesthesia (OR:0.10; 95%CI:0.01–0.76, p < 0.05) and for patients receiving premedication with benzodiazepines compared to not premedicated patients before general anesthesia (OR:0.35; 95%CI:0.13–0.93, p = 0.05).

Connected consciousness after tracheal intubation in young adults: an international multicentre cohort study

“…We also did not observe implicit recall of the experience, as both responders and non-responders scored similarly on the word retrieval task. Still, implicit recall has been documented in certain conditions during general anaesthesia 28 and could The most significant limitations of this study were the limitations in assessing connected consciousness. Although we assessed IFT responses after tracheal intubation, connected consciousness might occur throughout an anaesthetic and might occur more frequently during maintenance of anaesthesia.…”

Therapeutic Suggestions During General Anesthesia Reduce Postoperative Nausea and Vomiting in High-Risk Patients – A Post hoc Analysis of a Randomized Controlled Trial

“…Moreover, the phenomenon of "intraoperative awareness" has been described regularly (Millar and Watkinson, 1983;Ghoneim and Block, 1992;Schwender et al, 1994). However, our results cannot be explained by a few patients reacting like in "intraoperative awareness" with an incidence of only 0.1-0.2% for explicit recall (Sanders et al, 2012) and a few percent for implicit memory (Fu et al, 2021;Linassi et al, 2021). Therefore, auditory impressions that a patient perceives under general anesthesia must be critically questioned, since conversations and noises in the operating room can have a negative influence on patients and should be avoided (Hansen and Zech, 2019).…”

Incidence of Bacteriobilia and the Correlation with Antibioticoprophylaxis in Low-Risk Patients Submitted to Elective Videolaparoscopic Cholecystectomy: A Randomized Clinical Trial

“…For the surgical risk classification, the anesthetic risk categories and the physical status classification according to the American Society of Anesthesiologists (ASA) were used, an important reference for the pre-anesthetic evaluation of the patient [28,29]. Thus, it is used in several studies due to its close relationship with anesthetic morbidity and mortality, as shown in Figure 1.…”