Practice Advisory for Intraoperative Awareness and Brain Function Monitoring

Abstract

PRACTICE advisories are systematically developed reports that are intended to assist decision making in areas of patient care. Advisories provide a synthesis and analysis of expert opinion, clinical feasibility data, open forum commentary, and consensus surveys. Advisories are not intended as standards, guidelines, or absolute requirements. They may be adopted, modified, or rejected according to clinical needs and constraints.The use of practice advisories cannot guarantee any specific outcome. Practice advisories summarize the state of the literature and report opinions derived from a synthesis of task force members, expert consultants, open forums, and public commentary. Practice advisories are not supported by scientific literature to the same degree as are standards or guidelines because sufficient numbers of adequately controlled studies are lacking. Practice advisories are subject to periodic revision as warranted by the evolution of medical knowledge, technology, and practice.Intraoperative awareness under general anesthesia is a rare occurrence, with a reported incidence of 0.1–0.2%.1–4Significant psychological sequelae (e.g. , post–traumatic stress disorder) may occur after an episode of intraoperative awareness, and affected patients may remain severely disabled for extended periods of time.5However, in some circumstances, intraoperative awareness may be unavoidable to achieve other critically important anesthetic goals.The following terms or concepts discussed in this Advisory include: consciousness, general anesthesia, depth of anesthesia or depth of hypnosis, recall, amnesia, intraoperative awareness, and brain function monitors. Consistent definitions for these terms are not available in the literature. For purposes of this Advisory, these terms are operationally defined or identified as follows:Consciousness is a state in which a patient is able to process information from his or her surroundings. Consciousness is assessed by observing a patient’s purposeful responses to various stimuli. Identifiers of purposeful responses include organized movements following voice commands or noxious/painful stimuli.*For example, opening of the eyes is one of several possible identifiers or markers of consciousness. Purposeful responses may be absent when paralysis is present as a consequence of neurologic disease or the administration of a neuromuscular blocking drug.General anesthesia is defined as a drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation.†The ability to maintain ventilatory function independently is often impaired. Patients often require assistance in maintaining a patent airway, and positive-pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function. Cardiovascular function may be impaired.Depth of anesthesia or depth of hypnosis refers to a continuum of progressive central nervous system depression and decreased responsiveness to stimulation.For the purpose of this Advisory, recall is the patient’s ability to retrieve stored memories. Recall is assessed by a patient’s report of previous events, in particular, events that occurred during general anesthesia. Explicit memory is assessed by the patient’s ability to recall specific events that took place during general anesthesia. Implicit memory is assessed by changes in performance or behavior without the ability to recall specific events that took place during general anesthesia that led to those changes.6A report of recall may be spontaneous or it may only be elicited in a structured interview or questionnaire. This Advisory does not address implicit memory.Amnesia is the absence of recall. Many anesthetic drugs produce amnesia at concentrations well below those necessary for suppression of consciousness. Anterograde amnesia is intended when a drug with amnestic properties is administered before induction of anesthesia. Retrograde amnesia is intended when a drug such as a benzodiazepine is administered after an event that may have caused or been associated with intraoperative consciousness in the hope that it will suppress memory formation and “rescue” from recall.Intraoperative awareness occurs when a patient becomes conscious during a procedure performed under general anesthesia and subsequently has recall of these events. For the purpose of this Advisory, recall is limited to explicit memory and does not include the time before general anesthesia is fully induced or the time of emergence from general anesthesia, when arousal and return of consciousness are intended. Dreaming is not considered intraoperative awareness.Brain function monitors are devices that record or process brain electrical activity and convert these signals mathematically into a continuous measure typically scaled from 0 to 100. In addition to monitoring spontaneous cortical electrical activity (electroencephalogram [EEG]), these devices may also record and process evoked cortical and subcortical activity (auditory evoked potentials [AEPs]) as well as electromyographic (EMG) activity from scalp muscles. For the purpose of this Advisory, only monitors purported to measure depth of anesthesia or hypnosis will be considered. Other, non-EEG, non-AEP, non-EMG devices are also available but are not addressed by this Advisory.Intraoperative awareness under general anesthesia is an important clinical problem that clearly is within the foundation of training and continuing medical education in anesthesiology. The purposes of this Advisory are to identify risk factors that may be associated with intraoperative awareness, provide decision tools that may enable the clinician to reduce the frequency of unintended intraoperative awareness, stimulate the pursuit and evaluation of strategies that may prevent or reduce the frequency of intraoperative awareness, and provide guidance for the intraoperative use of brain function monitors as they relate to intraoperative awareness.This Advisory focuses on the perioperative treatment of patients who are undergoing a procedure during which general anesthesia is administered. This Advisory is not intended for the perioperative management of minimal, moderate, or deep sedation in the operating room or intensive care unit; regional or local anesthesia without general anesthesia; monitored anesthesia care; tracheal intubation of patients or those undergoing resuscitation in after the administration of a neuromuscular or intraoperative (e.g. , for the purposes of intraoperative neurologic In this Advisory is not intended to address the perioperative treatment of Advisory is intended for use by other who the administration of general anesthesia, and other who general anesthesia. The Advisory may also as a for other and who are in the perioperative management of patients general of this of to and the available scientific literature on intraoperative awareness, expert consensus and public opinion, and a practice The is of from various areas of the an from The and from the on Practice the to the because of or in the medical of and the of practice The include but are not limited to with or in the of of the of from or a in a or brain function these have a in the use of such monitors. may also have from or have a in other such as or of that may be affected by the use of brain function monitors. The not for to such because they and to present of in from consultants, of who knowledge, in intraoperative awareness and brain function monitors. or is in in some on or by a or brain function monitors. of the of from or a in a or brain function monitors. also may have from or have a in other that may be affected by the use of brain function monitors. The not for to such because they and to present of a the consensus on the for of perioperative for the of intraoperative they in to this who or in intraoperative awareness and who or in (e.g. , in and to in on the of various perioperative management strategies and to and on a of the Advisory developed by the opinions from a of of the the open at and anesthesia to on the concepts of this available information to consensus within the on the available for on the and to considered by the in the advisories are developed by a to that of an practice a and evaluation of the literature. practice advisories the of a sufficient of adequately controlled studies to of with such as from reports and other studies are considered during the of the This literature often the of of clinical with a practice information is from and of the The following terms responses for any are on a from to with a of responses are on as of of the responses are of of the responses are or and of of the responses are or other or of at of the of of responses are or and of of responses are information is from open forum and other and public The in this a of the of clinical and evaluation a , medical patient or a patients at risk for intraoperative awareness (e.g. , of and patients of the of intraoperative studies and reports that patient may be associated with intraoperative awareness, and drug or studies and reports that (e.g. , well as anesthetic (e.g. , anesthetic with or without the of be associated with an risk of intraoperative studies that the clinical of the patient before of the of intraoperative and that a evaluation may be in patients at risk for intraoperative awareness In they that a evaluation to identify patients at risk of intraoperative awareness include of a patient’s medical a and a patient or They that patient that may place a patient at risk for intraoperative awareness include use or limited and of or The and the that a of intraoperative awareness may place a patient at The and the are patients be of the of intraoperative The and that only patients considered to be at risk of intraoperative awareness be of the of intraoperative the and the that the patient of the risk of intraoperative awareness the risk of intraoperative that some of the evaluation may be in a patient at risk for evaluation a of a patient’s medical for previous of awareness or other risk a patient interview to of or previous with anesthesia, and a risk factors to for patients undergoing general anesthesia include use or (e.g. , a of awareness, a of intubation or patients of and anesthetic in the of use of during the of general anesthesia, anesthesia, the use of anesthesia, of or and limited The consensus of the is that patients the clinician to be at risk of intraoperative awareness be of the of intraoperative awareness when the of anesthesia to the of intraoperative awareness include the of anesthesia and the administration of the of anesthesia is some of intraoperative awareness have from concentrations of or drug drug clinical the of the administration of as an anesthetic during under anesthesia and reported a frequency of intraoperative awareness in the with the clinical amnesia by as after administration of but before induction of general anesthesia. these studies reported recall in patients administered the of consciousness during general anesthesia and intraoperative awareness not and that the of anesthesia (e.g. , be to reduce the risk of intraoperative The and the are that a benzodiazepine or be as a of the anesthetic to reduce the risk of intraoperative awareness for The that a benzodiazepine or be for patients of patients undergoing and patients undergoing They are patients undergoing and anesthesia. The that a benzodiazepine or be for patients of and patients undergoing and anesthesia. They are patients undergoing intraoperative awareness may be caused by or the that be to a for anesthesia and to that the anesthetic drugs and will be be extended to include of the of and The consensus is that the decision to a benzodiazepine be on a for patients (e.g. , patients of The that emergence may the use of awareness cannot be during the intraoperative of general anesthesia, because the recall of awareness only be by information from the the intraoperative monitoring addressed by this Advisory is the use of clinical monitoring or brain function monitors the of intraoperative of literature during the and process not address these or monitors reduce the frequency of intraoperative studies that report intraoperative or from monitoring This not the of an on awareness, often reported or that occurred at during the perioperative with the of or in the depth of anesthesia. reported from this literature are literature for is in the following clinical studies (e.g. , studies (e.g. , of with concentrations of drugs or with in to reports of monitored at during a and reports of or unintended or during a monitoring studies often report a measure of continuous (e.g. , the and anesthetic drug include a that a measure of well a or clinical (e.g. , to of an and a clinical a of a to the clinical to intraoperative consciousness are for to responses or and monitoring include well as the anesthetic clinical or other studies that the of clinical or monitoring on the incidence of intraoperative studies reported from to for the or purposeful and for depth of reported a to and memory when continuous of as the induction for from to for a state from an state and from to for an state from emergence after anesthesia , for from to for a state from an state and from to for of and reported during various intraoperative reported of as before induction or at during at emergence or of and during reported as before induction or at during at emergence or of and during has been reported to occur in the absence of or and that clinical (e.g. , for purposeful or are and be to intraoperative consciousness. In the and that monitoring (e.g. , anesthetic are and be to intraoperative of the devices to brain electrical activity for the purpose of anesthetic record activity from on the be into those that process spontaneous and electromyographic activity and those that evoked responses to and of the to the various are to the derived from the or to a often to as an typically scaled 0 and 100. This the of clinical of consciousness with a of associated with the state and of 0 with an absent may be and in the public or of the various to may be intended to and are an important of the in electromyographic activity from scalp be considered an from the of it may be an important of of electromyographic activity to from and may of For this some monitors provide information on the of electromyographic The is a that a of into an of is available as a or under from in by various anesthesia the several derived from the time frequency are into a of are scaled from 0 to with specific (e.g. , reported to a of consciousness under general anesthesia. The factors for the various in the that the derived from a of The for the of activity by to the as the changes with concentrations of various in a in have available and as and to suppress have been of the and have been controlled have with anesthetic administration clinical practice without In one that patients at risk of intraoperative awareness, explicit recall occurred in of patients when monitors and in of patients by clinical practice , the to the monitoring with clinical during and reported one episode of recall in the clinical with in the other to or opening and of anesthetic drugs with the use of of the use of monitoring a of explicit recall in of the patients of the to the incidence of awareness with recall during general anesthesia and to associated with intraoperative awareness events reported when of with when not of studies reported on in the care and anesthetic use patients monitored with with patients not monitored with studies reported for from to for loss of after induction with or without and from to for reported a of for from electrical of have been reported during various intraoperative of as before induction or at or after during at emergence or of and during reports that intraoperative events to of anesthetic produce changes in (e.g. , or of anesthesia drug reports that intraoperative events (e.g. , administration of of or patient or may with reports that reported patients intraoperative awareness monitored an depth of other reports that patient may the or of a a from a The for of in the as in the is in the public and have been is of absolute such as the or the frequency of the The available time of and reports is an from 0 to the frequency from to the cortical state of the is an from 0 to a frequency from to the and will also to the electromyographic activity from clinical or other studies that the of monitoring on the incidence of intraoperative clinical reported to to and of anesthetic drugs with the use of studies report the following for loss of for for the following are for and for of and as before induction or and during and and at emergence or of and The is derived from a system developed for the of the associated with various of and the the according to the following anesthesia with deep anesthesia with The system a of in a of possible and the of the the has been into a the scaled from 0 to with the of a to the clinical or other studies that the of monitoring on the incidence of intraoperative has the use of controlled anesthetic administration and a time in the , after of for from to for loss of after induction with with an and from to for are as after induction of and at emergence or of state The is derived from a The of the is on the that are changes in of at loss and return of consciousness. The has a of with of consciousness or of to and The analysis on of derived after of the and to be to changes in the of clinical or other studies that the of monitoring on the incidence of intraoperative reported a of for to with a of and of reported a of the with are as before induction or during at emergence or of and during The a from a of The is on a analysis of activity in the 0 to and to frequency and a suppression are on the to the which is on a of and clinical or other studies that the of monitoring on the incidence of intraoperative that reported a of to be of a loss of consciousness in of The is a that a and a scaled from 0 to 100. In it also suppression and a measure of electromyographic activity literature that the of the on the incidence of intraoperative evoked potentials are the electrical responses of the the and the to The of on have been the is to cortical as the with concentrations of and The to anesthetic concentrations is and decreased of the various signals are from the spontaneous time have in an that record and a of from a analysis of the the an that a of anesthetic The or is scaled from 0 to 100. In to the with of consciousness is the associated with the other monitors. The is by the and but is not in controlled that monitoring (e.g. , to to clinical practice without reported to opening or of reported for loss of after induction with and an of and reported for responsiveness after of or reported a of for reported a of for awareness after studies reported of as before induction or at or after during at emergence or of and during who in this Advisory typically a or an in intraoperative awareness and brain function monitors. The of these of from or a in a or brain function monitors. not to with other that may be affected by the use of brain function monitors. from a of of the and that a brain electrical activity is and be to reduce the risk of intraoperative awareness for The and that a brain electrical activity is and be to reduce the risk of intraoperative awareness for The that a brain electrical activity be for patients with that may place at risk and patients of general and anesthesia. They are the use of brain electrical activity monitoring for and The with the use of such monitors for patients with that may place at patients of general and patients undergoing They are the use of these monitors for patients undergoing and and that a brain electrical activity is and be to intraoperative depth of anesthesia for The and with the that brain electrical activity is and be to intraoperative depth of anesthesia for The that a brain electrical activity be to intraoperative depth of anesthesia for The with the use of brain electrical activity monitors for patients with that may place at risk and patients of general They are the use of such monitors for patients undergoing and monitoring of depth of anesthesia, for the purpose of the of awareness, on clinical (e.g. , for clinical such as purposeful or and monitoring (e.g. , anesthetic The use of neuromuscular blocking drugs may purposeful or movements and to the use of monitoring that the of function monitors are to the of the of on the brain and provide information that with some depth of anesthesia such as concentrations of (e.g. , In the by these monitors in with other of depth of anesthesia, the by devices in any anesthetic state the various monitoring In the by devices in the of a depth of anesthesia by of anesthetic drugs (e.g. , with or without also In other a specific may not with a specific depth of anesthesia. the not have anesthetic drugs or of with other in the operating room may into the derived by these monitors (e.g. , general clinical of these monitors in the of intraoperative awareness has not been a clinical reported a in the frequency of awareness in is to a or absolute that these devices be to reduce the of intraoperative awareness in patients undergoing general anesthesia. In is to a or absolute that these devices be to reduce the of intraoperative awareness for any other of patients undergoing general is the consensus of the that brain function monitoring is not for patients undergoing general anesthesia, to reduce the frequency of intraoperative awareness or to depth of anesthesia. This consensus is in on the state of the literature and responses from the and who with the following function monitors are and be to reduce the risk of intraoperative awareness for patients under general and function monitors are and be when possible to intraoperative depth of anesthesia for patients under general is the consensus of the that the decision to use a brain function be on a by the for patients (e.g. , This consensus is in on the state of the literature and from and specific risk factors The that maintaining brain function in an to prevent intraoperative awareness may with other important anesthesia (e.g. , of the of is the of the that brain function monitors have the of the other monitoring that are in at the of and include the intraoperative administration of to patients who may have a structured interview to patients to the of the episode after an episode of intraoperative awareness has been a to patients to the of the and or psychological studies that the of the intraoperative administration of to patients who have conscious in the of clinical amnesia by as to patients before administration of and induction of general anesthesia. The studies reported of these studies not the of a benzodiazepine to patients after the of consciousness during general several studies have structured and to information reported of intraoperative studies that in patient or psychological state after such studies that on the of or psychological to patients who a incidence of intraoperative are and that or be administered to prevent awareness after a patient has The and the that an episode of intraoperative awareness has been a structured interview be to the of the the and are a be to the of the The and the that in of intraoperative awareness, patients be or psychological the and the that in of intraoperative awareness, an report the event be for the purpose of consensus is that the decision to a benzodiazepine after a patient becomes conscious be on a This consensus is in on the state of the literature and on responses from the and the following or be administered to prevent awareness after a patient has the that from the literature is not sufficient to provide guidance this the that the use of may in unintended (e.g. , emergence with patients who report recall of intraoperative events to of the event and to possible for or structured interview may be to a of the patient’s an episode of intraoperative awareness has been an report the event be for the purpose of the patient be or psychological this Advisory, a literature in with opinions from and other (e.g. , members, open forums, to provide guidance to intraoperative the literature and on , of specific perioperative and intraoperative The are or report that in the literature is in the of an the is to one of the reports a or of that be or (e.g. , that only are not and is the of an or report , or studies that summarize previous are not the literature studies identified and of the literature. The a from The a of time from a of that addressed to the and for of the studies not provide and subsequently of studies with and information to a analysis , and by a for as of of and literature for of and literature to of of this Advisory to studies with such as that the of an as a brain function on the or frequency of intraoperative only controlled that reported intraoperative awareness as the controlled will be necessary before from literature be to provide a for , other that reported other intraoperative awareness, emergence of anesthetic and In other studies to or For example, literature , reports of frequency or may provide an of the of the or provide information the and of of from patient monitoring devices with other intraoperative such as concentrations of anesthetic time to loss of and time to reports are typically as a forum for and or unintended or reports as well as or provide information that may stimulate of the of intraoperative studies on when that use of the following for the of for intraoperative awareness is studies the of one other to treatment with and of of and The because intraoperative awareness is a such studies may be and The required for a to the of an (e.g. , brain function on the incidence of intraoperative awareness is The also with data, a in the of one or of intraoperative awareness the of the to patient to have a risk for intraoperative awareness (e.g. , may for a and provide information these the that the of these to the of general anesthesia patients may be from from who on or in intraoperative awareness, opinions from a of of the from of open at anesthesia commentary, and and The of return of for and for the are in the of the and in and of the and of the that they a brain function in the of the that they use in practice of a brain function or of the that they use in practice of a brain function or also to of the clinical the Advisory The of return of The of associated with as patients of the of intraoperative anesthesia use of as use of clinical to for intraoperative use of monitoring to for intraoperative use of brain function monitors to for intraoperative intraoperative use of for use of a structured interview for patients who report recall of intraoperative use of a for patients who report recall of intraoperative and for patients who report recall of intraoperative of the that the Advisory have on the of time on a that be an in the of time they on a with the of this The of time by these from to