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Awareness with recall during general anesthesia PDF

101 Pages·2002·0.73 MB·English
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Department of Anaesthesia and Intensive Care Medicine University of Helsinki, Finland Awareness with recall during general anesthesia Seppo Ranta Academic Dissertation To be publicly discussed by permission of the Medical Faculty of the University of Helsinki, in Auditorium 2, Biomedicum Helsinki, Haartmaninkatu 8, on September 21, 2002, at 12 o’clock noon Helsinki 2002 Supervised by: Docent Markku Hynynen, MD Department of Anaesthesia and Intensive Care Medicine, Helsinki University Central Hospital, Jorvi Hospital, Espoo, Finland Reviewed by: Professor Harry Scheinin, MD Turku PET Centre, Turku University Hospital Turku, Finland Docent Arvi Yli-Hankala, MD Department of Anaesthesia, Tampere University Hospital Tampere, Finland Official opponent: Professor Rolf Sandin, MD The Karolinska Institute, Stockholm, and Department for Anesthesia and Intensive Care, Länssjukhuset, Kalmar, Sweden ISBN 952-91-4981-6 (nid.) ISBN 952-10-0642-0 (PDF) Hakapaino Oy Helsinki 2002 http://ethesis.helsinki.fi/ Contents Abstract .............................................................................................. 7 List of original publications................................................................ 9 Abbreviations.................................................................................... 10 1. Introduction ................................................................................. 11 2. Review of the literature................................................................. 12 2.1. Definitions...............................................................................12 2.1.1. General anesthesia..............................................................................12 2.1.2. Consciousness ....................................................................................12 2.1.3. Awareness...........................................................................................12 2.1.4. Memory and Recall............................................................................13 2.1.5. Awareness with recall during general anesthesia..................................13 2.2. The nature of the experience of awareness during general anesthe- sia ...................................................................................................14 2.3. Methods of detecting awareness during general anesthesia........14 2.4. Incidence of awareness and recall during general anesthesia ......15 2.4.1. General surgery..................................................................................15 2.4.2. Cardiac surgery ..................................................................................18 2.4.3. Other types of surgery........................................................................18 2.5. Reasons for awareness with recall during general anesthesia ......22 2.5.1. General considerations .......................................................................22 2.5.2. Anesthetics.........................................................................................23 2.5.2.1. The concepts of minimum alveolar concentration and effective concentration.23 2.5.2.2. Potent volatile anesthetic agents........................................................................23 2.5.2.3. Intravenous anesthetics.....................................................................................24 2.5.2.4. Opioids.............................................................................................................24 2.5.2.5. Benzodiazepines................................................................................................24 2.5.2.6. Nitrous oxide....................................................................................................25 2.5.2.7. Neuromuscular blocking agents........................................................................25 2.6. Prevention of awareness with recall...........................................25 2.6.1. General recommendations..................................................................25 2.6.2. Methods of monitoring consciousness during general anesthesia ........26 2.6.2.1. Clinical signs.....................................................................................................26 2.6.2.2. The isolated forearm technique.........................................................................26 2.6.2.3. Electroencephalography ....................................................................................27 2.7. After-effects of awareness with recall during general anesthesia .28 2.7.1. Mental after-effects.............................................................................28 2.7.2. Medico-legal after-effects....................................................................29 3. Aims of the study.......................................................................... 30 4. Patients and methods.................................................................... 31 4.1. Patients ....................................................................................31 4.2. Interviews and classification .....................................................33 4.3. Medications .............................................................................33 4.4. Artificial neural networks .........................................................34 4.5. Feedback information ..............................................................36 4.6. Psychiatric interview and testing...............................................37 4.7. Statistical methods ...................................................................37 5. Results.......................................................................................... 38 5.1. The nature of the experience of awareness during general anesthe- sia ...................................................................................................38 5.2. Incidence of awareness with recall during general surgery .........38 5.3. Incidence of awareness with recall during open heart surgery....38 5.4. Differences in anesthetic drug dosing between patients with and without awareness ...........................................................................39 5.5. Conventional statistical methods and artificial neural networks in detecting awareness from monitored physiologic variables ...............39 5.6. The possibility of reducing the incidence of awareness by giving feedback information to the anesthesiologists ..................................40 5.7. Psychiatric consequences of awareness during anesthesia...........41 5.8. Medico-legal consequences of awareness with recall in Finland .42 6. Discussion .................................................................................... 46 6.1. Patients’ experiences during the episode of intra-anesthetic aware- ness.................................................................................................46 6.2. Methods used in the present studies.........................................46 6.2.1. Interviews .............................................................................46 6.2.2. Anesthetic records.................................................................47 6.3. Incidence of awareness with recall during general surgery .........47 6.4. Incidence of awareness with recall during cardiac surgery .........48 6.5. Differences in anesthetic drug dosing between patients with and without awareness ...........................................................................49 6.6. Conventional statistical methods and artificial neural networks in detecting awareness from monitored physiologic parameters............49 6.7. The possibility of reducing the incidence of awareness by giving feedback information to the anesthesiologists ..................................50 6.8. Psychiatric consequences of awareness during anesthesia...........51 6.9. Medico-legal consequences of awareness with recall in Finland .52 7. Conclusions.................................................................................. 53 8. Practical considerations ................................................................ 55 9. Future implications....................................................................... 57 Acknowledgements ........................................................................... 58 References......................................................................................... 60 Appendix .......................................................................................... 65 Abstract Awareness with recall is a rare but serious com- In the present studies, the incidence of plication of general anesthesia with potentially undisputed intraoperative awareness was 0.2- very disabling psychiatric consequences. Pre- 0.4 % of all general anesthetics given for gen- requisites for the phenomenon of awareness eral surgery procedures, while the incidence and recall are (1) consciousness with the abil- was about 0.3 % during cardiac anesthesia. ity to receive and process sensory information, Both incidences are 6 to 7 fold higher if cases (2) storage of the processed information in of possible awareness and recall are included. memory, and (3) recollection of the stored Lower doses of primary anesthetic agents were information at some later time. given to patients with awareness and recall The present study examines incidence of when compared to controls (isoflurane 0.42 awareness with recall during general anesthe- Fi% vs. 0.65 Fi% [p<0.005] and propofol 73 sia, the effects of anesthetic agents on it, meth- µg/kg/min vs. 228 µg/kg/min [p<0.05], dur- ods of detecting and preventing it, and its psy- ing general surgery respectively; midazolam chiatric and medico-legal after-effects. A total 0.8 µg/kg/min vs. 1.1 µg/kg/min [p<0.05] of 3,868 cases (1,485 male and 2,383 female) during cardiac surgery respectively). Standard were included in this study. Structured inter- physiologic monitoring used during general views were conducted after general anesthesia anesthesia did not reliably detect inadequate for cardiac or general surgery to find patients depth of anesthesia, even when analyzed with who had experienced awareness during anes- computer-based artificial intelligence. Infor- thesia and were able later to recall their expe- mation given to anesthesiologists about in- rience. Additional cases were identified from traoperative awareness lead to a decreasing insurance claims based on awareness with re- trend in its incidence with simultaneous in- call filed with the Patient Insurance Associa- crease in the use of anesthetics and decrease tion in Finland. Psychiatric interview and test- in the use of muscle relaxants. ing were used to evaluate after-effects of The psychiatric studies revealed anxiety in awareness and recall. Feedback information one patient after awareness and recall. In ad- was given to cardiac anesthesiologists in order dition, a case of pre-existing depression was to study the possibility of reducing incidence exacerbated after an episode of awareness and of awareness with recall by educational means. recall. Awareness during general anesthesia has Artificial neural networks were used to evalu- triggered a small number of Patient Insurance ate the likelihood of detecting intraoperative claims in Finland (about 1 % of anesthesia- awareness on the basis of conventional moni- related claims). Seventy percent of the patients toring information. who filed insurance claims received compen- 7 sations for pain; the average amount of com- would decrease it further Awareness cannot pensation was EUR 1,000. be detected by standard monitoring; better Awareness with recall is a rare complica- monitoring tools need to be developed. The tion of general anesthesia and its incidence is incidence of psychiatric after-effects of intra- on the decline. Insufficient dosing of general operative awareness is not known. In Finland, anesthetics contributes significantly to the a small number of Patient Insurance claims present incidence and it is likely that inform- has been the only medico-legal after-effect of ing anesthesiologists about this complication this complication. 8 List of original publications 1.Ranta S., Laurila R., Saario J., Ali-Melkkilä T., Hynynen M.: Awareness with recall during general anesthesia - Incidence and risk factors. Anesth Analg 86: 1084-1089, 1998. 2.Ranta S., Jussila J., Hynynen M.: Recall of awareness during cardiac anaesthesia: influence of feedback information to the anaesthesiologist. Acta Anaesthesiol Scand 40:554-560, 1996. 3.Ranta S., Herranen P, Hynynen M.: Patients’ conscious recollections from cardiac anesthe- sia. J Cardiothorac Vasc Anesth 16:426-430, 2002. 4.Ranta S., Hynynen M., Räsänen J: Application of artificial neural networks as an indicator of awareness with recall during general anaesthesia. J Clin Monit Comput 17:53-60, 2002. 5.Ranta S., Ranta V., Aromaa U.: The claims of compensation for awareness with recall during general anaesthesia in Finland. Acta Anaesthesiol Scand 41:356-359, 1997. 9 Abbreviations AA Anesthetic agent AEP Auditory evoked potential AER Auditory evoked response ANOVA Analysis of variance ASA American Society of Anesthesiologists BIS Bispectral index BP Blood pressure CABG Coronary artery bypass grafting CI Confidence interval CO Carbon dioxide 2 D&C Dilatation and curettage DSM-III Diagnostic and Statistical Manual of Mental Disorders, 3rd edition DSM-IV Diagnostic and Statistical Manual of Mental Disorders, 4th edition EBT Endobronchial tube EC Effective concentration in 50 percent of the subjects 50 ECG Electrocardiogram EEG Electroencephalogram ET End-tidal ETAGC End-tidal anesthetic gas concentration ETT Endotracheal tube EUR Euro Fi Inspiratory fraction FIM Finnish Mark GBP Pound sterling i.v. Intravenous ICU Intensive care unit IFT Isolated forearm technique MAC Minimum alveolar concentration MLAEP Mid-latency auditory evoked potential MVR Mitral valve replacement N.A. Not assessed NO Nitrous oxide 2 NMB Neuro-muscular blocker ns. non-significant PACU Post-anesthesia care unit PIA Patient Insurance Association P Prediction probability k PTSD Post-traumatic stress disorder SaO Arterial blood oxygen saturation 2 SE Standard error Tx Transplantation USD United States Dollar 10

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Department of Anaesthesia and Intensive Care Medicine University of Helsinki, Finland Awareness with recall during general anesthesia Seppo Ranta
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