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Awareness and Dreaming during Anaesthesia: Incidence and Importance
Linköping University, Department of Medicine and Health Sciences. Linköping University, Faculty of Health Sciences.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The definition of awareness used consistently in this thesis is: Explicit recall of intraoperative events during general anaesthesia. Since there is no objective method to detect awareness, the patients must be interviewed after anaesthesia. The form and timing of the interview is crucial. To rely on spontaneous disclosure of awareness episodes is not sufficient. The total number of awareness-victims is considerable although the incidence may seem modest. A number of these patients look upon the awareness experience as the worst experience in their life. Suffering can include pain, mental distress and delayed psychological symptoms. However, the experience of awareness is not uniform and not all patients suffer.

A comprehensible definition for dreaming during anaesthesia is: Any recalled experience, excluding awareness, which occurred between induction of anaesthesia and the first moment of consciousness upon emergence. Some findings point in the direction that dreaming during anaesthesia may be related to light or insufficient anaesthesia, but other findings do not. Some patients find dreaming during anaesthesia distressing, but generally the overall impression is that consequences of dreaming during anaesthesia seem to be small and of minor importance to the majority of patients.

In this thesis I have found the following:The incidence of awareness is approximately 0.2% when neuromuscular blocking drugs are used and awareness also exists without these drugs, albeit to a lesser extent. These findings represent standard practice in an adult population at normal risk. 50% of awareness cases may have delayed recall of awareness.

Using a consecutive inclusion design we found initial awareness suffering comparable to previous studies, but a lower incidence and less pronounced severity of late psychological symptoms. The incidences found among the awareness-victims in our study were; experience of pain 46%, immediate mental distress 65%, any late psychological symptom 33%, and PTSD below 10%.

A memory of an intraoperative dream after general anaesthesia is not an early interpretation of delayed awareness, indicating that no routine follow up of dreaming-only patients is indicated.

Dreams reported after anesthesia are generally not related to insufficient anesthesia defined as high BIS, and should not be regarded as near awareness.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2008. , 53 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1082
National Category
Anesthesiology and Intensive Care
Identifiers
URN: urn:nbn:se:liu:diva-15408ISBN: 978‐91‐7393‐786‐3 OAI: oai:DiVA.org:liu-15408DiVA: diva2:114126
Public defence
2008-12-06, Eken, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 11:00 (Swedish)
Opponent
Supervisors
Available from: 2008-11-06 Created: 2008-11-06 Last updated: 2009-08-21Bibliographically approved
List of papers
1. Awareness during anaesthesia: a prospective case study
Open this publication in new window or tab >>Awareness during anaesthesia: a prospective case study
2000 (English)In: The Lancet, ISSN 0140-6736, Vol. 355, no 9205, 707-711 p.Article in journal (Refereed) Published
Abstract [en]

Background

Patients who are given general anaesthesia are not guaranteed to remain unconscious during surgery. Knowledge about the effectiveness of current protective measures is scarce, as is our understanding of patients' responses to this complication. We did a prospective case study to assess conscious awareness during anaesthesia.

Methods

11 785 patients who had undergone general anaesthesia were interviewed for awareness on three occasions: before they left the post-anaesthesia care unit, and 1–3 days and 7–14 days after the operation.

Findings

We identified 18 cases of awareness and one case of inadvertent muscle blockade that had occurred before unconsciousness. Incidence of awareness was 0·18% in cases in which neuromuscular blocking drugs were used, and 0·10% in the absence of such drugs. 17 cases of awareness were identified at the final interview, but no more than 11 would have been detected if an interview had been done only when the patients left the post-anaesthesia care unit. Four non-paralysed patients recalled intraoperative events, but none had anxiety during wakefulness or had delayed neurotic symptoms. This finding contrasts with anaesthesia with muscle relaxants, during which 11 of 14 patients had pain, anxiety, or delayed neurotic symptoms. After repeated discussion and information, the delayed neurotic symptoms resolved within 3 weeks in all patients. Analysis of individual cases suggests that a reduced incidence of recall of intraoperative events would not be achieved by monitoring of end-tidal anaesthetic gas concentration or by more frequent use of benzodiazepines.

Interpretation

The inability to prevent awareness by conventional measures may advocate monitoring of cerebral activity by neurophysiological techniques. However, the sensitivity of such techniques is not known, and in the light of our findings, at least 861 patients would need to be monitored to avoid one patient from suffering due to awareness during relaxant anaesthesia.

Place, publisher, year, edition, pages
Lancet, 2000
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:liu:diva-15402 (URN)10.1016/S0140-6736(99)11010-9 (DOI)
Available from: 2008-11-06 Created: 2008-11-06 Last updated: 2009-06-03Bibliographically approved
2. Late Psychological Symptoms after Awareness among Consecutively Included Surgical Patients
Open this publication in new window or tab >>Late Psychological Symptoms after Awareness among Consecutively Included Surgical Patients
2007 (English)In: Anesthesiology, ISSN 0003-3022, E-ISSN 1528-1175, Vol. 106, no 1, 26-32 p.Article in journal (Refereed) Published
Abstract [en]

Background: Awareness during general anesthesia can cause late psychological symptoms. Selection bias may have affected the results in previous retrospective studies. The authors used prospective consecutive collection to recruit patients with previous awareness.

Methods: In a cohort of 2,681 consecutive patients scheduled to undergo general anesthesia, 98 considered themselves to have been aware during previous surgery. Six patients died before inclusion, and another 13 were excluded (4 cases of stoke or dementia, 7 declined to participate, and 2 could not be located). Seventy-nine patients were interviewed by telephone, and medical records were checked in uncertain cases. The interview followed a structured protocol, including seven late symptoms (anxiety, chronic fear, nightmares, flashbacks, indifference, loneliness, and lack of confidence in future life). Three persons independently assessed the interviews for classification, to determine whether awareness had occurred.

Results: Four cases were performed using regional anesthesia, and another 29 were not considered as awareness by the assessors. Therefore, the final analyses included 46 patients. Twenty (43%) had experienced pain, and 30 (65%) described acute emotional reactions during the awareness episode. Fifteen (33%) patients had experienced late psychological symptoms afterward. In 6 of those cases, the symptoms lasted for more than 2 months, and 1 patient had a diagnosis of post-traumatic stress disorder. Acute emotional reactions were significantly related to late psychological symptoms (P < 0.05).

Conclusion: The method for recruiting awareness cases in studies on late psychological symptoms may affect the result. The authors found fewer and milder problems, despite a similar degree of initial problems as in previous studies.

National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:liu:diva-15404 (URN)10.1097/00000542-200701000-00009 (DOI)
Available from: 2008-11-06 Created: 2008-11-06 Last updated: 2014-01-21Bibliographically approved
3. Intraoperative dreams reported after general anaesthesia are not early interpretations of delayed awareness
Open this publication in new window or tab >>Intraoperative dreams reported after general anaesthesia are not early interpretations of delayed awareness
2008 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 52, no 6, 805-809 p.Article in journal (Refereed) Published
Abstract [en]

Background: Dreams are more frequently reported than awareness after surgery. We define awareness as explicit recall of real intraoperative events during anaesthesia. The importance of intraoperative dreaming is poorly understood. This study was performed to evaluate whether intraoperative dreams can be associated with, or precede, awareness. We also studied whether dreams can be related to case-specific parameters.

Methods: A cohort of 6991 prospectively included patients given inhalational anaesthesia were interviewed for dreams and awareness at three occasions; before they left the post-anaesthesia care unit, days 1–3 and days 7–14 after the operation. Uni- and multivariate statistical relations between dreams, awareness and case-specific parameters were assessed.

Results: Two hundred and thirty-two of 6991 patients (3.3%) reported a dream. Four of those also reported awareness and remembered real events that were distinguishable from their dream. Awareness was 19 times more common among patients who after surgery reported a dream [1.7% vs. 0.09%; odds ratio (OR) 18.7; P=0.000007], but memories of dreams did not precede memories of awareness in any of the 232 patients reporting a dream. Unpleasant dreams were significantly more common when thiopentone was used compared with propofol (OR 2.22; P=0.005). Neutral or pleasant dreams were related to lower body mass index, female gender and shorter duration of anaesthesia.

Conclusions: We found a statistically significant association between dreams reported after general anaesthesia and awareness, although intraoperative dreams were not an early interpretation of delayed awareness in any case. A typical dreamer in this study is a lean female having a short procedure.

Place, publisher, year, edition, pages
Malden, MA United States: Wiley-Blackwell, 2008
Keyword
Intraoperative dreams, awareness, consciousness
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:liu:diva-15405 (URN)10.1111/j.1399-6576.2008.01634.x (DOI)000256683700012 ()
Available from: 2008-11-06 Created: 2008-11-06 Last updated: 2014-01-21Bibliographically approved
4. BIS does not predict dreams reported after anaesthesia
Open this publication in new window or tab >>BIS does not predict dreams reported after anaesthesia
2008 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 52, no 6, 810-814 p.Article in journal (Refereed) Published
Abstract [en]

Background: In earlier studies, between 1% and 57% of patients have been reported to dream during anaesthesia. Thus, dreaming is much more common than definite memories of real events. We wanted to examine whether dreaming during anaesthesia is related to insufficient hypnotic action, as indicated by BIS levels and, thus, may constitute a risk for awareness.

Methods: After IRB approval, 2653 consecutive surgical patients were included. BIS registrations were recorded continuously during the anaesthetic procedure. The patients were interviewed on three occasions after anaesthesia. Standard questions, according to Brice, to evaluate awareness and dreaming during anaesthesia were asked. The dreams were categorized as either pleasant/neutral or unpleasant without any further evaluation of the dream content. Episodes with a mean BIS below 40, above 60 and above 70 were identified and subdivided according to duration (1, 2, 4 and 6 min, respectively). The total time as well as number and duration of episodes for the three BIS-levels were used to analyze any relation to reported dreaming. The mean BIS was also analyzed.

Results: Dreaming during anaesthesia was reported by 211 of patients (8.0%) on at least one of the post-operative interviews. BIS data did not show any significant correlation with dreaming, and neither did any of the tested case-specific parameters (gender, age, ASA group, BMI, use of relaxants, induction agent, maintenance agent, length of procedure, omitting N2O and concomitant regional anaesthesia).

Conclusion: Dreaming during anaesthesia seems to be a separate phenomenon, not in general related to insufficient anaesthesia as indicated by high BIS levels.

Place, publisher, year, edition, pages
Malden, MA, USA: Wiley-Blackwell, 2008
Keyword
Dreams, general anaesthesia, BIS
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:liu:diva-15407 (URN)10.1111/j.1399-6576.2008.01633.x (DOI)000256683700013 ()
Available from: 2008-11-06 Created: 2008-11-06 Last updated: 2014-01-21Bibliographically approved

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