Awareness with recall during general anesthesia

101 Pages·2002·0.73 MB·English

by  Seppo Ranta

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