Intraoperative unconsciousness and amnesia are main goals of general anesthesia. Although these objectives are achieved in the vast majority of cases, in very rare circumstances they are not “completely” obtained, or maintained, and in turn, accidental consciousness and subsequent memorization of sensorial information may occur during intended anesthesia. This failure of anesthesia is termed as general anesthesia awareness (or accidental awareness during general anesthesia, or simply awareness). While the incidence of this complication is rare, the clinical features and its potentially devastating psychological sequelae impose a thorough knowledge of the phenomenon. During anesthesia, the patient may be occasionally cognizant responding to commands or may wake up. This intraoperative awakening, termed as “wakefulness,” must be not confused with the awareness. The discriminating element for a proper definition of awareness, indeed, is the concomitant presence of two elements that correspond to higher cognitive functions: consciousness and memory processing of the intraoperative experience. Although not all wakefulness episodes complete the memory processing (encoding, storing through consolidation, and retrieval), consolidated unexpected experiences can be expressed as explicit-spontaneous, or induced, reports. The pathways of this declarative, or explicit, memory produce, in turn, the awareness with recall phenomenon. Alternatively, the intraoperative experience can be processed without requiring conscious memory content and expressed as inexplicable changes in behaviors, or performances, or through the mechanism of priming, in which exposure to one stimulus influences a response to a subsequent stimulus, without conscious guidance, or intention. The processing of information via nondeclarative, or implicit, memory system, leads to the other awareness subtype: the awareness without explicit recall. Referring to the state of the art of research, the aim of this chapter is to dissect the multiple aspects of this anesthesia-induced complication. Although in recent years research has allowed us to understand many aspects of the phenomenon, its complete characterization still seems far away, and several controversies and dark sides remain. In particular, the chapter addresses topics related to definitions and classification, epidemiology, clinical features, risk factors, management, and strategies useful for prevention. Finally, the interest in the subject is justified as it represents a fascinating matter of investigation which intersects study areas in the contexts of the “general anesthesia research” and neuroscience. Mechanisms of anesthesia, and impact of anesthetics on consciousness and memory, represent an attractive way for studying brain and mind through an “experimental model” (general anesthesia) that is carried out on several tens of millions of patients, every year.
The Challenge of Accidental Awareness During General Anesthesia
Cascella M.
2020
Abstract
Intraoperative unconsciousness and amnesia are main goals of general anesthesia. Although these objectives are achieved in the vast majority of cases, in very rare circumstances they are not “completely” obtained, or maintained, and in turn, accidental consciousness and subsequent memorization of sensorial information may occur during intended anesthesia. This failure of anesthesia is termed as general anesthesia awareness (or accidental awareness during general anesthesia, or simply awareness). While the incidence of this complication is rare, the clinical features and its potentially devastating psychological sequelae impose a thorough knowledge of the phenomenon. During anesthesia, the patient may be occasionally cognizant responding to commands or may wake up. This intraoperative awakening, termed as “wakefulness,” must be not confused with the awareness. The discriminating element for a proper definition of awareness, indeed, is the concomitant presence of two elements that correspond to higher cognitive functions: consciousness and memory processing of the intraoperative experience. Although not all wakefulness episodes complete the memory processing (encoding, storing through consolidation, and retrieval), consolidated unexpected experiences can be expressed as explicit-spontaneous, or induced, reports. The pathways of this declarative, or explicit, memory produce, in turn, the awareness with recall phenomenon. Alternatively, the intraoperative experience can be processed without requiring conscious memory content and expressed as inexplicable changes in behaviors, or performances, or through the mechanism of priming, in which exposure to one stimulus influences a response to a subsequent stimulus, without conscious guidance, or intention. The processing of information via nondeclarative, or implicit, memory system, leads to the other awareness subtype: the awareness without explicit recall. Referring to the state of the art of research, the aim of this chapter is to dissect the multiple aspects of this anesthesia-induced complication. Although in recent years research has allowed us to understand many aspects of the phenomenon, its complete characterization still seems far away, and several controversies and dark sides remain. In particular, the chapter addresses topics related to definitions and classification, epidemiology, clinical features, risk factors, management, and strategies useful for prevention. Finally, the interest in the subject is justified as it represents a fascinating matter of investigation which intersects study areas in the contexts of the “general anesthesia research” and neuroscience. Mechanisms of anesthesia, and impact of anesthetics on consciousness and memory, represent an attractive way for studying brain and mind through an “experimental model” (general anesthesia) that is carried out on several tens of millions of patients, every year.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
