Anesthesia awareness 667636 223693215 2008-07-05T08:30:18Z 76.91.90.112 /* The experience of anesthesia awareness */ Added link to term sequela '''Anesthesia awareness''', or "unintended intra-operative awareness" occurs during [[General anaesthetic|general anesthesia]], when a patient has not had enough general anesthetic or [[analgesic]] to prevent consciousness. ==Background== Awareness occurs in 20,000-40,000 patients out of every 20 million US annual surgeries every year<ref>Sebel PS: The incidence of awareness during anesthesia: A multicenter United States study. Anesth Analg 2004; 99:833-9</ref> when patients have anesthesia that is inadequate to keep them unconscious during an operation. In this situation, the patient may feel the pain or pressure of surgery, hear conversations, or feel as if they cannot breathe. The patient may be unable to communicate any distress because they have been given a paralytic/muscle relaxant. If anesthesia awareness does occur about 42% feel the pain of the operation, 94% experience panic/anxiety and 70% experience lasting psychological symptoms.<ref>N. Moerman et al,Anesthesiology;79:454-464, 1993</ref> In some cases, [[post traumatic stress disorder]] (PTSD) may arise after intraoperative awareness, causing the patient to require counseling for an extended period.<ref name="pmid11543846">{{cite journal |author=Osterman JE, Hopper J, Heran WJ, Keane TM, van der Kolk BA |title=Awareness under anesthesia and the development of posttraumatic stress disorder |journal=Gen Hosp Psychiatry |volume=23 |issue=4 |pages=198–204 |year=2001 |pmid=11543846|doi=10.1016/S0163-8343(01)00142-6}}</ref> ==Awareness and recall== There are two states of consciousness which may be present: *Awareness. When patients seem to be vigilant and cognizant responding to commands but with no postoperative recall or memory of the events. *Memorization and recall. When patients can recall events postoperatively but were not necessarily conscious enough for responding to commands. The incidence of a state with both responses in diverse degrees is also possible.<ref>{{cite book | last = Ghoneim| first = Mohamed M| title = Awareness during anesthesia| publisher = Butterworth Heinemann | date = 2001| pages = 2| isbn = 0-7506-7201-3}}</ref> ==The experience of anesthesia awareness== The most traumatic case of anesthesia awareness is full consciousness during surgery with pain and explicit recall of intraoperative events. In less severe cases, patients may have only poor recollection of conversations, events, pain, pressure or of difficulty in breathing. The experiences of patients with anesthesia awareness vary widely, and patient responses and [[sequela]]e vary widely as well. This experience may be extremely traumatic for the patient or not at all. Because the medical staff may not know if a person is unconscious or not, it has been suggested that the staff maintain the professional conduct that would be appropriate for a conscious patient.<ref name="pmid16801837">{{cite journal |author=Gajwani P, Muzina D, Gao K, Calabrese JR |title=Awareness under anesthesia during electroconvulsive therapy treatment |journal=J ECT |volume=22 |issue=2 |pages=158–9 |year=2006 |pmid=16801837 |doi= |url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?an=00124509-200606000-00018}}</ref> ==Conscious Sedation and Monitored Anesthesia Care== There are various levels of consciousness. Wakefulness and general anesthesia are two extremes of the spectrum. Conscious sedation and monitored anesthesia care (MAC) refer to an awareness somewhere in the middle of the spectrum depending on the degree to which a patient is sedated. It is important to note that awareness/wakefulness is not necessarily correlated with pain or discomfort. The aim of conscious sedation or minimal anesthetic care is to provide a safe and comfortable anesthetic while maintaining the patient's ability to follow commands. Under certain circumstances, a general anesthetic, whereby the patient is completely unconscious, may be unnecessary and/or undesirable. For instance, with a cesarean delivery, the goal is to provide comfort with neuroaxial anesthetic yet maintain consciousness so that the mother can participate in the birth of her child. Other circumstances may include, but are not limited to, procedures that are minimally invasive or purely diagnostic (and thus not uncomfortable). Sometimes, the patient's health may not tolerate the stress of general anesthesia. The decision to provide monitored anesthesia care versus general anesthesia can be complex involving careful consideration of individual circumstances. Patients who undergo conscious sedation or monitored anesthesia care are never meant to be without recall.<ref>Lekprasert, Varinee:"PreAnesthetic Assessment of the Patient Who Reports Previous Intraoperative Awareness", ''Anesthesiology News'', June 2008, pages 35-38, www.AnesthesiologyNews.com.</ref> Whether or not a patient remembers the procedure depends on the type of medications uses, the dosages used, patient physiology, and other factors. Many patients undergoing monitored anesthesia care do not remember the experience. ==Incidence== The [[incidence (epidemiology)|incidence]] of anesthesia awareness in the United States is believed to be 20,000 to 40,000 cases per year, which represents 0.1 percent and 0.2 percent of all patients undergoing general anesthesia.<ref>[[Joint Commission on Accreditation of Healthcare Organizations]] (JCAHO). ''Sentinel Event Alert'' 6 Oct 2004;32. Sebel PS: The incidence of awareness during anesthesia: A multicenter United States study. Anesth Analg 2004; 99:833-9[http://www.jcaho.org/about+us/news+letters/sentinel+event+alert/sea_32.htm Online version]</ref> The incidence of anesthesia awareness is higher when [[muscle relaxants]] are used.<ref name="pmid12557119">{{cite journal |author=Schneider G |title=[Intraoperative awareness] |language=German |journal=Anasthesiol Intensivmed Notfallmed Schmerzther |volume=38 |issue=2 |pages=75–84 |year=2003 |pmid=12557119 |doi=10.1055/s-2003-36993 |url=http://www.thieme-connect.com/DOI/DOI?10.1055/s-2003-36993}}</ref> A recent large-scale study reported a much lower rate (0.0068%).<ref name="pmid17264720">{{cite journal |author=Pollard RJ, Coyle JP, Gilbert RL, Beck JE |title=Intraoperative awareness in a regional medical system: a review of 3 years' data |journal=Anesthesiology |volume=106 |issue=2 |pages=269–74 |year=2007 |pmid=17264720 |doi=}}</ref> The modified patient interview used in this retrospective study did not specifically ask the patient if he/she had experienced awareness during the surgery. Prompt inspection of the anesthesia equipment and record is important and may help prevent future occurrences. It is also important that a case of suspected awareness be communicated to the patient's healthcare team, and that the event be scrutinised closely by senior anesthetic medical staff. For the most exhaustive unparalleled database on the incidence of Anesthesia Awareness, see a database developed by Doctor Evidence (a medical information company) and commissioned by Aspect.<ref>{{cite web |url=http://awareness.doctorevidence.com/IOAEvidence.aspx|title=Intraoperative Awareness- doctorevidence.com |accessdate=2008-06-06 |format= |work=}}</ref> ==Outcomes== Patients who experience full awareness with explicit recall may have suffered an enormous trauma. Some patients experience [[posttraumatic stress disorder]] (PTSD), leading to long-lasting after-effects such as nightmares, night terrors, flashbacks, [[insomnia]], and in some cases even suicide.<ref>{{cite web |url=http://www.boston.com/news/nation/articles/2007/04/10/lawsuit_wide_awake_surgery_led_to_death/ |title=Lawsuit: Wide-awake surgery led to death - Boston.com |accessdate=2007-11-11 |format= |work=}}</ref> There is evidence that early psychological counselling and support can reduce the amount of harm and chances of developing PTSD.{{Fact|date=April 2007}} The patient must be treated sympathetically and with compassion. ==Risk factors/Causes== ===Paralytics/muscle relaxant use=== A common risk factor is the use of a medication that induces muscle paralysis. Under [[general anesthesia]], the patient's muscles may be paralysed in order to facilitate tracheal intubation, surgical exposure, or mechanical [[Ventilation (physiology)|ventilation]]. The paralytic agent does not cause unconsciousness or take away the patient's ability to feel pain. A fully paralyzed patient is unable to move, speak, blink the eyes, or otherwise respond to the pain except through physiological signs such as increased heart rate ([[tachycardia]]), blood pressure ([[hypertension]]), dilation of the pupils ([[mydriasis]]), sweating ([[diaphoresis]]), and the formation of tears ([[lacrimation]]) in response to pain. This is because these paralytic drugs cause skeletal muscle paralysis but do not typically interfere with the functioning of the [[autonomic nervous system]]. Even though the patient cannot directly signal their distress, they may exhibit signs of awareness detectable by clinical vigilance. Many types of surgery do not require the patient to be paralysed. A patient who is anesthetised but not paralysed can move in response to a painful stimulus if the analgesia is inadequate. This '''can''' serve as a warning sign that the anesthetic depth is inadequate. However, "moving" under general anesthesia does not necessarily correlate with awareness, nor does "not moving" under general anesthesia necessarily correlate with amnesia. ===Light anesthesia=== For certain operations, such as [[Caesarean section]], or in hypovolemic patients or patients with minimal cardiac reserve, the anesthesia provider may aim to provide "light anesthesia." During such circumstances, consciousness and recall may occur because judgments of depth of anesthesia are not precise. The anesthesia provider must weigh the need to keep the patient safe and stable with the goal of preventing awareness. Sometimes, it is necessary to provide lighter anesthesia in order to preserve the life of the patients. ===Improper equipment maintenance/anesthetist error=== Human errors include inadequate drug dose, inadequate monitoring, and failure to refill the [[anesthetic machine]]'s [[anaesthetic vaporiser|vaporiser]]s with [[volatile anesthetic]]. Other causes of awareness include unfamiliarity with techniques used, e.g. intravenous anesthetic regimes, or inexperience. Poor anesthetic technique is a combination of any of the above, but also includes techniques which could be described as outside the boundaries of "normal" practice. The [[American Society of Anesthesiologists]] recently released a Practice Advisory outlining the steps that anesthesia professionals and hospitals should take to minimize these risks. Other societies have released their own versions of these guidelines, including the [[Australian and New Zealand College of Anaesthetists]].<ref name="titleANZCA — ANZCA">{{cite web |url=http://www.anzca.edu.au/publications/profdocs/profstandards/index.htm |title=ANZCA — ANZCA |accessdate=2007-11-26 |format= |work=}}</ref> Machine malfunction or misuse may result in an inadequate delivery of anesthetic. This may be caused by an empty vaporizer (or [[nitrous oxide]] [[gas cylinder|cylinder]]) or a malfunctioning intravenous pump or disconnection of its delivery tubing. To reduce the likelihood of awareness, anesthetists must be adequately trained and supervised while still in training. Equipment which monitors depth of anaesthesia, such as [[bispectral index|bispectral index monitoring]], should not be used in isolation. ===Patient physiology=== Possible causes of awareness include drug tolerance, or a tolerance induced by the interaction of other [[medication|drugs]]. Some patients may be more resistant to the effects of anesthetics than others. Younger age, overweight, tobacco smoking or long-term use of certain drugs ([[alcohol]], [[opiate]]s, or [[amphetamine]]s) may increase the anesthetic dose needed to produce unconsciousness. There may be genetic variations that cause differences in how quickly patients clear anesthetics, and there may be differences in how the sexes react to anesthetics as well. Anxiety prior to the surgery can increase the amount of anesthesia required to prevent recall. ==Prevention== The risk of awareness is reduced by simple steps and good clinical practice: well-trained personnel; avoidance of paralytics unless necessary; careful checking of drugs, doses and equipment; good monitoring, and careful vigilance during the case. ==Monitors== Recent advances have led to the manufacture of monitors of awareness. Typically these monitor the [[Electroencephalography|EEG]], which represents the electrical activity of the [[cerebral cortex]], which is active when awake but quiescent when anaesthetised (or in natural [[sleep]]). The monitors usually process the EEG signal down to a single number, where 100 corresponds to a patient who is fully alert, and zero corresponds to electrical silence. General anaesthesia is usually signified by a number between 60 and 40 (this varies with the specific system used). There are several monitors now commercially available. These newer technologies include the [[bispectral index]] (BIS),<ref>{{cite journal |author=Myles PS, Leslie K, McNeil J, Forbes A, Chan MT |title=Bispectral index monitoring to prevent awareness during anaesthesia: the B-Aware randomised controlled trial |journal=Lancet |volume=363 |issue=9423 |pages=1757–63 |year=2004 |pmid=15172773 |doi=10.1016/S0140-6736(04)16300-9 |url=http://www.thelancet.com/journal/vol363/iss9423/full/llan.363.9423.original_research.29716.1}}</ref> EEG [[entropy monitoring]], auditory [[evoked potentials]], and several other systems such as the SNAP monitor and the Narcotrend monitor. None of these systems are perfect. For example, they are unreliable at extremes of age (e.g. [[neonate]]s, infants or the very elderly). Secondly, certain agents, such as [[nitrous oxide]], [[ketamine]] or [[xenon]],{{Fact|date=April 2007}} may produce anesthesia without reducing the value of the depth monitor. This is because the molecular action of these agents ([[NMDA]] receptor antagonists) differs from that of more conventional agents, and they suppress cortical EEG activity less. Thirdly, they are prone to interference from other biological potentials (such as [[EMG]]), or external electrical signals (such as diathermy). This means that the technology does not yet exist which will reliably monitor depth of anaesthesia for every patient and every anaesthetic. ==Controversies== Currently, the anesthesia provider community accepts that anesthesia awareness occurs, however there is not much of a consensus on the incidence or on how often patients experience long term mental distress. A study from Sweden in 2002 attempted to follow up 18 patients approximately 2 years after previously diagnosed awareness under anesthesia.<ref>{{cite journal |author=Lennmarken C, Bildfors K, Enlund G, Samuelsson P, Sandin R |title=Victims of awareness |journal=Acta anaesthesiologica Scandinavica |volume=46 |issue=3 |pages=229–31 |year=2002 |pmid=11939910|doi=10.1034/j.1399-6576.2002.t01-1-460301.x}}</ref> Four of the nine interviewed patients were still severely disabled due to psychiatric/psychological sequelae. All of these patients had experienced anxiety during the period of awareness, but only one had complained about pain. Another three patients had less severe, transient mental symptoms, although they could cope with these in daily life. Two patients denied any sequelae from their awareness episode. ==Research== New research has been carried out to test what people can remember after a general anesthetic in an effort to more clearly understand anesthesia awareness and help to protect patients from experiencing it. A [[memory]] is not one simple entity; it is a system of many intricate details and networks. Memory is currently classified under two main subsections. * First there is '''explicit''' or conscious memory,<ref name="pmid17236646">{{cite journal |author=Sandin R |title=Outcome after awareness with explicit recall |journal=Acta Anaesthesiol Belg |volume=57 |issue=4 |pages=429–32 |year=2006 |pmid=17236646 |doi=}}</ref> which refers to the conscious recollection of previous experiences. An example of explicit memory is remembering what you did last weekend. When it comes to an anesthetized patient, a doctor may ask the patient after undergoing general anesthesia if he or she could remember hearing any distinct sounds or words while under anesthesia. This approach is called a "recall test" because patients are asked to recall any memories they had during surgery. * The second main type of memory is '''implicit''' memory or unconscious memory, which refers to the changes in performance or behavior that are produced by previous experiences but without any conscious recollection of those experiences. An example of this is a recognition test, where patients are asked which of the following words were played to you during your surgery. As a further example please note the following scenario. Patients were exposed during anesthesia to a list of words containing the word "pension". Postoperatively, when they were presented with the three-letter word stem PEN___ and were asked to supply the first word that came to their minds beginning with those letters, they gave the word "pension" more often than "penis" or "peninsula" or others.<ref name="pmid10691248">{{cite journal |author=Ghoneim MM |title=Awareness during anesthesia |journal=Anesthesiology |volume=92 |issue=2 |pages=597–602 |year=2000 |pmid=10691248 |doi=10.1097/00000542-200002000-00043|url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=0003-3022&volume=92&issue=2&spage=597}}</ref> Some researchers are now formally interviewing patients postoperatively to calculate the incidence of anesthesia awareness. Most patients who were not unduly disturbed by their experiences do not necessarily report cases of awareness unless directly asked. It has been found that some patients may not recall experiencing awareness until one to two weeks after undergoing surgery. It was also found that some patients require a more detailed interview to jog their memories for intraoperative experiences. ==Cultural references== * ''[[Awake (film)|Awake]]'', a 2007 film about anesthetic awareness * ''[[Anesthesia]]'', an award-winning horror film about anesthesia awareness.<ref name="titleAnesthesia (2006)">{{cite web |url=http://www.imdb.com/title/tt0810754 |title=Anesthesia (2006) |accessdate=2007-11-26 |format= |work=}}</ref> * ''Return'', a Korean thriller movie about anesthesia awareness.<ref name="titleReturn (2007) - 리턴 @ HanCinema :: The Korean Movie and Drama Database, discover the South Korean cinema and drama diversity">{{cite web |url=http://www.hancinema.net/korean_movie_Return.php |title=Return (2007) - 리턴 @ HanCinema :: The Korean Movie and Drama Database, discover the South Korean cinema and drama diversity |accessdate=2007-11-26 |format= |work=}}</ref> *In an episode of ''[[Nip/Tuck]]'' a woman experiences anesthesia awareness while having surgery to repair scarring on her face. ==See also== * [[Anaesthetic machine]] * [[Carol Weihrer]] * [[Iatrogenic]] ==References== {{reflist|2}} ==External links== * [http://www.asahq.org/ American Society of Anesthesiologists] at asahq.org * [http://www.nurse-anesthesia.org/ Resource for Student & Working Nurse Anesthetists] at nurse-anesthesia.org * [http://www.stanford.edu/group/maciverlab/research.html Resource for Physiology and Pharmacology] at [[Stanford University]] * [http://www.freshgasflow.com Rapid Anesthesia Scan] - Anesthesia website that describes a system where an anesthetist can [[Category:Anesthesia]] [[Category:Medical Controversies]]