29: Awareness During Anesthesia

CHAPTER 29 Awareness During Anesthesia



Aaron Murray, MD



1 Review the classifications of memory and awareness


The current classifications of memory include both implicit, or unconscious memory, and explicit, or conscious memory. Explicit memory refers to the conscious recollection of specific intraoperative events that took place during general anesthesia, also called anesthetic awareness. Recall can only be determined after surgery. These memories can occur with or without pain and can range from vivid recollections to vague memories. It was reported in 2008 that subjective auditory perceptions represented 50% of intraoperative awareness experiences. By contrast, implicit memory reflects changes in behavior or performance secondary to an anesthetic experience without the ability to specifically recall the event. The 2006 American Society of Anesthesiologists’ (ASA) practice advisory regarding intraoperative awareness excludes dreaming as anesthetic awareness.



2 What is the incidence of awareness?


Estimates of awareness during anesthesia in nonobstetric and noncardiac surgeries are approximately 0.1% to 0.2%. Whenever lighter anesthesia is provided, the incidence increases. During cardiac surgery the incidence ranges from 1.1% to 1.5%. A higher incidence is also seen in obstetric (0.4%) and trauma cases (11% to 43%). Interestingly, although the use of anesthetic techniques associated with increased awareness (e.g., nitrous-narcotic) has decreased, the claims against anesthesiologists for awareness are increasing, recently accounting for 2% of all claims. This claim rate rivals other common complications such as aspiration pneumonia and myocardial infarction.



3 Are certain techniques and clinical situations more likely to result in awareness?


Recognized risk factors for awareness include the following:


image Light levels of anesthesia, which are common in hypovolemic, injured, and obstetric patients

image Prior history of intraoperative awareness

image Patients undergoing cardiac surgery with cardiopulmonary bypass; a higher incidence of postoperative recall (about 1%) occurs because of the reliance on narcotic-based anesthesia, which minimizes myocardial depression but produces unreliable amnesia

image The use of muscle relaxants

image Machine malfunction such as empty vaporizers, intravenous anesthetic pump malfunction or disconnection, and syringe swaps

image Other patient risks implicated in awareness include: the very young, chronic substance-abusing patients, chronic pain patients, and patients with hypernatremia.


4 Describe clinical signs and symptoms of light anesthesia

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May 31, 2016 | Posted by in ANESTHESIA | Comments Off on 29: Awareness During Anesthesia

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