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).
Highlights
One of the most important goals of general anesthesia is to ensure the patient’s unconsciousness and unresponsiveness during induction and maintenance [1] as well as to achieve post-operative amnesia, usually detected by the absence of an explicit recall [2].A popular assessment tool to evaluate responsiveness during anesthesia is the Observer’s Assessment of Alertness/Sedation Scale (OAA/S) [3]
While anesthesia awareness has an incidence of only 0.1–0.2% [1], connected consciousness, as detected by the isolated forearm technique, has a higher incidence, up to 34.8% [4]
We performed a systematic review and meta-analysis of previously published studies that investigated the occurrence of implicit memory after deep sedation or general anesthesia
Summary
One of the most important goals of general anesthesia is to ensure the patient’s unconsciousness and unresponsiveness during induction and maintenance [1] as well as to achieve post-operative amnesia, usually detected by the absence of an explicit recall [2].A popular assessment tool to evaluate responsiveness during anesthesia is the Observer’s Assessment of Alertness/Sedation Scale (OAA/S) [3]. One of the most important goals of general anesthesia is to ensure the patient’s unconsciousness and unresponsiveness during induction and maintenance [1] as well as to achieve post-operative amnesia, usually detected by the absence of an explicit recall [2]. While anesthesia awareness has an incidence of only 0.1–0.2% [1], connected consciousness, as detected by the isolated forearm technique, has a higher incidence, up to 34.8% [4]. The experience of such conscious episodes can lead to an increased risk of post-traumatic stress disorders [5,6]
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