Download Awareness during general anaesthesia

European Review for Medical and Pharmacological Sciences
2011; 15: 1085-1089
Awareness during general anaesthesia –
implications of explicit intraoperative recall
D. RADOVANOVIC, Z. RADOVANOVIC
Oncology Institute of Vojvodina, Novi Sad (Serbia)
Abstract. – Anaesthesia awareness (AA)
is postoperative recall of events experienced under general anaesthesia. Most frequently patients remember an auditory perception, the feeling of motor function lost, pain, helplessness,
anxiety, panic, impending death. The prevalence
of awareness in nonobstetric and noncardiac
surgical cases is 0.1%-0.2%. The prevalence is
higher in cardiac surgery, obstetric and major
trauma cases. According to the results of many
studies light anaesthesia is the most common
cause of the AA. Posttraumatic stress disorder
appears in 33%-56% of patients who experienced awareness during general anaesthesia.
Extreme awareness experiences are very uncommon, but traumatic and can have lasting effects on patients. Several brain-function monitors based on the processed electroencephalogram or evoked potentials have been developed
to assess anaesthetic depth. Measures to prevent awareness include avoidance of light anesthesia, gaining more knowledge about patient
anaesthetic requirements and development of
methods to detect consciousness during anesthesia.
Key Words:
Anaesthesia general, Anaesthesia depth, Complications awareness, Explicit recall.
Introduction
Anaesthesia awareness (AA) is postoperative
recall of events experienced under general anaesthesia. This term refers to the situation when we
cannot assume, on the basis of usual clinical
signs (such as blood pressure increase, heart rate
frequency, muscular contractions, lacrimation,
etc.), that anaesthesia is not of adequate depth.
After operation patient could remember some or
all events during the surgery and it is possible
that he didn’t feel anything or might have felt
moderate or intense pain or pressure if the analgesics dose hadn’t been adequate.
It is believed that awareness occurs as a result
of auditory and verbal stimuli that are registered
by brain cortex during the anaesthesia of apparently adequate depth. Explicit awareness means
that patients are able to express their memories
postoperatively. It occurs spontaneously or after
being provoked by some questions or a postoperative event shortly after operation. With implicit
awareness patients are not able to express their
memories postoperatively and are not aware of
them, but there are changes in performance or
behavior that can be proved by hypnosis, specific
tests and other methods1,2. In 1985, Bennett3 carried out a double-blind study of implicit awareness, in which he randomized 33 patients to either suggestion or control group. Suggestion
group patients were called by their names while
they were under anaesthesia and asked to pull
their ear postoperatively. They received nitrous
oxide, halothane or enflurane. After the operation
none of the patients could recall the suggestion
but the patients who had received the message intraoperatively were recorded to pull their ears
more frequently than patients in the control
group.
What do Patients Most often Remember?
Most frequently they remember an auditory
perception (voices 66%, noises 17%), the feeling
of motor function lost (not being able to breath
48%, sensation of paralysis 17%), pain (38%),
feelings of helplessness, anxiety, panic, impending death, or catastrophe (34%)4,5. Depending of
what part of the operation they remember, the
pain can come from intubation, incision or the
following surgical procedure.
When do Patients Become Aware?
Sandin et al. 6 performed one of the largest
study on this topic which included 11785 pa-
Corresponding Author: Dragana Radovanović, MD; e-mail: [email protected]
1085
D. Radovanovic, Z. Radovanovic
tients. They identified 18 cases of awareness and
one case of inadvertent muscle blockade that had
occurred before unconsciousness. Prevalence of
awareness was 0.18% in cases in which neuromuscular blocking drugs were used, and 0.1% in
the absence of such drugs. Results showed that
39% of patients awareness was identified already
in post-anaesthesia care unit (PACU), in 33% of
the patients between the 1st and the 3rd day after
the operation and in 27% of the patients awareness was detected on the 7th day after the operation and anaesthesia. Significant percentage of
patients report awareness at PACU but they
negate it during the following checks and vice
versa. The detection of awareness depends on the
interview technique, timing of the interview and
structure of the interview7. Therefore, it is necessary to check the patients who are suspected of
being aware under anaesthesia minimum three
times, in three different time intervals.
Frequency
The prevalence of awareness in nonobstetric
and noncardiac surgical cases is 0.1%-0.2%2,4,6-8.
In a study from Australia, Myles et al8 reported a
frequency of awareness of 0.10%; it was the highest risk factor for patient dissatisfaction after anesthesia. However, in certain patient groups, such
those undergoing anesthesia for cardiac, emergency trauma, obstetric surgery or bronchoscopy,
an increased risk for awareness and recall has
been reported. The prevalence in cardiac surgery
ranges from 1.1-1.5%, in obstetric cases (0.4%)
and major trauma cases (11-43%)1,2,9-14.
Studies that have been performed recently
show that awareness is more common in children
than in adults, which causes a real problem15.
There are several reasons for that: it is believed
that the children up to third year don’t have ex-
plicit memory completely developed, so they are
not able to express their memories. Besides, the
EEG is changing during the children’s growth, so
there is some data showing that the methods for
monitoring awareness such as bispectral index
(BIS) and entropy, are less reliable in children
younger than one year old ones.
The frequency of AA is not high, but we
shouldn’t forget the great number of various interventions that are performed under general
anesthesia all over the world every day. At issue
here is a significant number of AA cases. We
should have in mind that the presence of awareness under general anesthesia falls within the
range of responsibilities of an anaesthesiologist,
thus a case of AA can turn into a law suit case
against an anaesthesiologist.
Risk Factors
Regarding the different kinds of surgical interventions, awareness is more frequent at major
traumas that are followed by hypovolemia and
hypotension, cardiac surgeries, C-sections, at intervention that are carried out at night, in operation of patient who undergo general anaesthesia
for the first time1,10.
A careful review of the literature reveals that
regarding the sex and age as risk factors, results
are very different4,7,16-18. So, in the study which
included 3843 patients in Finland16, awareness
was identified only in female patients, with incidence of awareness of 0.07% in outpatients and
0.13% in inpatients. On the other side, an American study on 177468 patients19 showed that the
prevalence of awareness was two times higher in
male patients of an older age.
The Table I shows the major and minor criteria
of awareness frequency during general anaesthesia. The patient with the higher risk for aware-
Table I. Major and minor criteria of awareness incidence during general anaesthesia.
Major criteria
• Preoperative long-term use of anticonvulsant agents,
opiates, benzodiazepines, or cocaine
• Heavy alcohol intake
• History of anaesthesia awareness and/or history of
difficult intubation
• ASA physical status class 4 or class 5
• Cardiac ejection fraction (EF) < 40%
• Aortic stenosis
• Pulmonary hypertension
1086
Minor criteria
• Use of beta-blockers
• Chronic obstructive pulmonary disease (COPD)
• Obesity BMI > 30
• Smoking two or more packs of cigarettes per day
Awareness during general anaesthesia – implications of explicit intraoperative recall
ness is the one with at least one major risk criterion or two minor risk criteria.
It has been suggested that there may be a higher frequency of awareness in obese patients for
several reasons, including often prolonged time
for endotracheal intubation, the use of higher
concentrations of oxygen in nitrous oxide-oxygen mixtures and the difficulty of giving appropriate doses of drugs without causing postoperative respiratory depression4,16,20.
Causes (Table II)
The light anaesthesia was the most common
cause of the AA according to results of many
studies2,4,10,13,17,18. Sometimes it is impossible to
avoid inadequate anaesthetic dose: some cases of
emergency procedures, procedures that are carried out at night, procedures followed by massive
blood loss and hemodynamic instability, in patients with low cardiac reserve. Some patients
need more anaesthetic that can be the cause of
this complication10. Routine administration of
muscle relaxants, especially if they are given before hypnotics as an introduction to anaesthesia,
poor connection between intravenous cannula
and extravascular parts of the aparatusses, empty
evaporators, evaporators that are not calibrated
and other causes that may consequently result in
an inadequate delivery of anaesthetic1,2,7.
Regarding the anaesthetic technique, it should
be considered wheather it affects the frequency
of awareness. The results of some studies show
that the frequency of awareness is higher when
total IV anesthesia (TIVA) technique is used
compared with balanced technique. However,
with TIVA, it’s impossible to monitor the concentration of i.v. agents in the blood. On the other hand, with inhalation anesthesia, it is possible
to monitor the N2O level and volatile anaesthetics
in expiratory air10,21.
Table II. Causes of anaesthesia awareness.
• Inadequate anaesthetic dose – emergency trauma,
hypovolemic patients, emergency C-section, cardiac
surgery
• Resistance to anaesthetics – hyperthyroidism, obesity,
anxiety, younger age, long-term use of certain drugs
(alcohol, opiates or amphetamines)
• Routine administration of muscle relaxants
• Mechanical malfunction or misuse of anaesthetic
machine
• Anaesthetic technique?
In particular, according to the results of the
research carried out in Spain with 4001 patients
included, the prevalence of awareness in elective
surgery was 0.6%. The patients were divided into
three groups on the basis of anaesthetic technique: the prevalence of awareness was significantly higher in patients where inhalation anaesthetics halogen-containing were not used, the
prevalence was 1% for TIVA propofol anaesthesia (which means 1% out of all patients who got
TIVA were aware), 0.59% for balanced anaesthesia, 5% for O2/N2O10.
Consequences
Posttraumatic stress disorder appears in 33%56% of patients who experienced awareness during general anaesthesia: depression, anxiety,
sleep disturbances, nightmares, panic attacks
may appear even after 2 years and more7,17,22-25.
Extreme awareness experiences are very uncommon, but traumatic and can have lasting effects
on patients.
Treatment
Includes the following: calming down the patient, open discussion about the risk factors for
awareness during general anaesthesia, why and
how often it happens, the necessity of informing
the anaesthesiologist about the problem before
the next anesthesia, offering an apology and explanation. In some institutions it is openly discussed with patients before surgical interventions
about the possible awareness episodes during the
anaesthesia. It hasn’t been proved if such discussions can psychologically influence the increased
number of cases of anaesthesia awareness reported by the patients1.
Modern Monitoring
Several brain-function monitors based on the
processed electroencephalogram or evoked potentials have been developed to assess anaesthetic depth. Results of few investigations suggested
that BIS reduced anaesthetic use, recovery times,
risk of awareness and cost9,26,27. Findings in study
by Avidan do not support routine BIS monitoring
as part of standard monitoring. According to results of this study AA occurred even when BIS
values and end-tidal anesthetic gas (ETAG) concentrations were within the target ranges; the use
of the BIS protocol was not associated with reduced administration of volatile anaesthetic gases. It is important to emphasize that the BIS
monitoring may be useful during total intra1087
D. Radovanovic, Z. Radovanovic
venous anaesthesia, since it is not presently possible to monitor the blood concentrations of
anaesthetic agents28.
We can conclude that the clinical monitoring
of patients is an irreplaceable and necessary procedure in interpretation of the results coming
with modern monitoring.
How to Avoid Anesthesia Awareness?
(Table III)
We should preoperatively consider if there is a
higher risk for anaesthesia awareness and inform
selected patients of the possibility of intraoperative awareness. The American Society of Anesthesiologists (ASA) has published guidelines recommended that stringent efforts must be made to
prevent AA1.
We should consider premedication with
amnestic agents. The results of some studies
show that the application of benzodiazepines reduces the incidence of awareness10,29. There was
no difference in the frequency of awareness and
recall in respect to premedication, according to
the results of Sandin et al. study6. This observation seems to agree with the suggestion of a minor role of benzodiazepine premedication in protection from awareness and recall during anaesthesia6,16. Any firm conclusion about the effect of
benzodiazepines on the frequency of awareness
and recall should be drawn cautiously, because
the timing of the administration in relation to the
operation is not standardized, and the duration of
surgery varied considerably.
Table III. How to avoid anaesthesia awareness?
•
•
•
•
•
•
•
•
•
•
•
Consider if there is a higher risk for AA preoperatively
Consider premedication with amnestic agents?
Ensure patient is asleep prior to intubation
Provide additional doses of hypnotic or volatile agent
for repeated intubation attempts
Avoid paralysis unless needed
Use an end-Tidal agent monitor
Give adequate doses of anaesthetic agents – administer
at least 0,8-1 minimum alveolar concentration (MAC)
when volatile agents are used alone
Check all anaesthesia equipment: anaesthesia machine,
vaporizer, infusion pumps
Pay more attention on possible awareness when use
β-blockers
Be careful about the discussion in the surgical room
Patients with high risk for awareness consider use of
brain function monitoring
1088
Consultants who participated in ASA Practice
advisory for intraoperative awareness strongly
agree that functioning of anaesthesia delivery
systems (e.g., vaporizers, infusion pumps, fresh
gas flow, intravenous lines) should be checked to
reduce the risk of intraoperative awareness. Monitoring of the concentrations of inspired and expired gases and inhalation agents; and general
vigilance should eliminate cases caused by inadequate anaesthetic delivery1,2. In high risk situations, monitoring of depth of anaesthesia is justified. Use of such monitoring may also be advisable in patients in whom clinical signs of light
anaesthesia may be masked (concurrent β-blockers, diabetes).
Awareness during anaesthesia is uncommon,
but well described adverse outcome that may result in serious emotional injury and post-traumatic stress disorder. A properly trained anaesthetist,
administering anaesthesia according to knowledge of pharmacology and patient and surgical
characteristics, assisted by clinical signs and
monitoring, can minimize the risk of awareness.
Measures to prevent awareness include avoidance of light anesthesia, gaining more knowledge
about anaesthetic requirements of patients and
development of methods to detect consciousness
during anesthesia.
References
1) Practice advisory for intraoperative awareness
and brain functioning monitoring: A report by the
American Society of Anesthesiologists Task
Force on Intraoperative Monitoring. Anesthesiology 2006; 104: 847-864.
2) G HONEIM MM. Awareness during anesthesia.
Anesthesiology 2000; 92: 597-602.
3) BENNETT HL. Non-verbal response to intraoperative
conversation. Br J Anaesth 1985; 57: 174-179.
4) GHONEIM MM, BLOCK RI, HAFFARNAN M, MATHEWS MJ.
Awareness during anesthesia: risk factors, causes and sequelae: A Review of reported cases in
the literature. Anesth Analg 2009; 108: 527-535.
5) SCHWENDER D, KUNZE-KRONAWITTER H, DIETRISH P, KLASING S, FORST H, MADLER C. Conscious awareness
during general anaesthesia: patients’ perceptions,
emotions, cognition and reactions. Br J Anaesth
1998; 80: 133-139.
6) SANDIN RH, ENLUND G, SAMUELSSON P, LENNMARKEN C.
Awareness during anaesthesia: a prospective
case study. Lancet 2000; 355: 707-711.
Awareness during general anaesthesia – implications of explicit intraoperative recall
7) S EBEL PS, B OWDLE TA, G HONEIM MM, R AMPIL IJ,
PADILLA RE, GAN TJ, DOMINO KB. The incidence of
awareness during anesthesia: a multicenter
United States study. Anesth Analg 2004; 99:
833-839.
8) MYLES PS, WILLIAMS DL, HENDRATA M, ANDERSON H,
WEEKS AM. Patient satisfaction after anaesthesia
and surgery: results of a prospective survey of
10,811 patients. Br J Anaesth 2000; 84: 6-10.
9) M YLES PS, L ESLIE K, M C N EIL J, F ORBES A, C HAN
MTV. Bispectral index monitoring to prevent
awareness during anaesthesia: The B Aware
randomised controlled trial. Lancet 2004; 363:
1757-1763.
18) DOMINO KB, POSNER KL, CAPLAN RA, CHENEY FW.
Awareness during anesthesia. Anesthesiology
1999; 90: 1053-1061.
19) POLLARD RJ, COYLE JP, GILLBERT RL, BECK JE. Intraoperative awareness in a regional medical system.
Anesthesiology 2007; 106: 269-274.
20) GHONEIM MM. Incidence of and risk factors for
awareness during anaesthesia. Best Pract Res
Clin Anaesthesiol 2007; 21: 327-343.
21) HARDMAN JG. Awareness during anaesthesia. Continuing education in anaesthesia. Critical Care
Pain 2005; 5: 183-186.
22) SAMUELSSON P, BRUDIN L, SANDIN RH. Late psychological symptoms after awareness among consecutively included surgical patients. Anesthesiology 2007; 106: 26-32.
10) ERRANDO CL, SIGL JC, ROBLES M, CALABUIG E, GARCÍA
J, AROCAS F, HIGUERAS R, DEL ROSARIO E, LÒPEZ D,
PEIRÒ CM, SORIANO JL, CHAVES S, GIL F, GARCIA-AGUADO R. Awareness with recall during general
anaesthesia: a prospective observational evaluation of 4001 patients. Br J Anaesth 2008; 101:
178-185.
23) OSTERMAN JE, HOPPER J, HERAN WJ, KEANE TM, VAN
DER KOLK BA. Awareness under anesthesia and
the development of posttraumatic stress disorder.
Gen Hosp Psychiatry 2001; 23: 198-204.
11) ROBINS K, LYONS G. Intraoperative awareness during general anesthesia for cesarean delivery.
Anesth Analg 2009; 109: 886-890.
24) LENNMARKEN C, BILDFORS K, ENLUND G, SAMUELSSON P,
SANDIN R. Victims of awareness. Acta Anaesthesiol
Scand 2002; 46: 229-231.
12) PHILLIPS AA, MCLEAN RF, DEVITT JH, HARRINGTON EM.
Recall of intraoperative events after general
anaesthesia and cardiopulmonary bypass. Can J
Anaesth 1993; 40: 922-926.
25) OSTERMAN JE, HOPPER J, HERAN WJ, KEANE TM, VAN
DER KOLK BA. Awareness under anesthesia and
the development of posttraumatic stress disorder.
Gen Hosp Psychiatry 2001; 23: 198-204.
13) RANTA S, JUSSILA J, HYNYNEN M. Recall of awareness
during cardiac anaesthesia: influence of feedback
infor mation to the anaesthesiologist. Acta
Anaesth Scand 1996; 40: 554-560.
26) EKMAN A, LINDHOLM ML, LENNMARKEN C, SANDIN R.
Reduction in the incidence of awareness using
BIS monitoring. Acta Anaesthesiol Scand 2004;
48: 20-26.
14) BOGETZ MS, KATZ JA. Recall of surgery for major
trauma. Anesthesiology 1984; 61: 6-9.
27) BRUHN J, MYLES PS, SNEYD R, STRUYS MM. Depth of
anaesthesia monitoring: what's available, what's
validated and what's next? Br J Anaesth 2006;
97: 85-94.
15) ANDRADE J, DEEPROSE C, BARKER I. Awareness and
memory function during paediatric anaesthesia.
Br J Anaesth 2008; 100: 389-396.
16) WENNERVIRTA J, RANTA SO, HYNYNEN M. Awareness
and recall in outpatient anesthesia. Anesth Analg
2002; 95: 72-77.
28) AVIDAN MS, ZHANG L, BURNSIDE BA, FINKEL KJ, SEARLEMAN AC, SELVIDGE JA, SAAGER L, TURNER MS, RAO S,
B OTTROS M, H ANTLER C, J ACOBSOHN E, E VERS AS.
Anesthesia awareness and the bispectral index. N
Engl J Med 2008; 358: 1097-1108.
17) RANTA SO, LAURILA R, SAARIO J, ALI-MELKKILÄ T, HYNYNEN M. Awareness with recall during general
anesthesia: incidence and risk factors. Anesth
Analg 1998; 86: 1084-1089.
29) MILLER DR, BLEW PG, MARTINEAU RJ, HULL KA. Midazolam and awareness with recall during total intravenous anaesthesia. Can J Anaesth 1996; 43:
946-953.
1089