Memory Under Anesthesia: An Update

Abstract

The memory process occurs when all of the dissimilar elements between a past and a present idea combine among themselves to form a special compound called a memory image, that directly refers to a past idea. Various classifications or types of memory are presented according to different criteria.. Early Atkinson and Shiffrin proposed a model of human memory which presented two distinct memory stores which are : short-term memory and long-term memory , later a third memory store was added : sensory memory Recent studies have demonstrated that memory can be divided into at least two general categories: Implicit memory (Non-declarative memory) and Explicit memory (Declarative memory) Intraoperative awareness is defined as a recalled event in which a patient becomes conscious during a procedure performed under general anesthesia. The term “awareness” is limited to ‘explicit memory’ during anesthesia and does not include the time before general anesthesia is fully induced or the time of emergence from general anesthesia. Recall is the ability to retrieve stored memories. Many risk factors may increase the incidence of awareness including Risk related to type of surgery(Obstetric anesthesia, Cardiac surgery, Emergency surgery in polytraumatized patients) Risk related to anesthetic technique (Inhalation anesthesia, Total intravenous anesthesia, light anesthesia) Risk related to muscle relaxation and Patient related risk factors(History of awareness, Difficult airways, Previous history of alcohol, amphetamines, opioids and other drugs use). Implicit memory is change in performance or behavior without the ability to recall specific events that took place during general anesthesia that led to those change and is assessed by indirect memory tests. Many methods are used to monitor the depth of anesthesia including clinical signs (blood pressure, heart rate, muscle tone, lacrimation and sweating), Many drugs may affect memory causing amnesia (benzodiazepines, inhalation anesthetics and ketamine in high doses) Awareness could be prevented by premedication with benzodiazepines, deep anesthesia and continous monitoring of depth state of anesthesia, Management includes reassurance, supportive care and psychological counceling.