Patient Awareness During General Anaesthesia
By Dr. Adel Rizk Botros Prof of anaesthesia and Surgical ICU. Faculty of Medicine - Zagazig University.
Contents: - Introduction. - Definition of awareness during GA. - Incidence of awareness during GA.. - Types of awareness during GA. - Causes of awareness during GA. - Consequences of awareness during GA. - Measures to avoid awareness during GA : - Pre-operative measures. - Intra-operative measures. - Identification of patient with awareness postoperatively. - Management of patient with postoperative psychological disorders. - Conclusion.
Introduction: - Patient awareness during GA is a rare but very serious problem for both anesthetist and patient. - It is responsible for 2% of the legal claims against anesthetists. - Also it may have postoperative psychological sequelae for the patient as insomnia, depression, anxiety and post-traumatic stress disorder (PTSD).
Domino KB, Posner KL, Caplan RA, Cheney FW. Awareness during anesthesia: a closed claims analysis. Anesthesiology 1999; 90: 1053–61
Definitions: - Awareness during GA: It means patient sensation of some or all events that actually occurred during GA. - Dreaming: It means the train of thoughts or images that passing through the patient mind during GA. - Hallucination: It means patient perception of non-existent stimuli (visual, auditory or tactile) during GA.
Wilson S, Vaughan R, Stephen C. Awareness, dreams and hallucinations associated with general anesthesia. Anesthesia and Analgesia 1975;54:609-19.
Incidence of patient awareness during GA: - 0.2% in patients subjected to general surgery. - 0.4% in mothers subjected to CS. - 1-2% in patients subjected cardiac surgery. - 10-40% in traumatized patient subjected to general surgery. - 0.5-1% in pediatrics subjected to general surgery. - The incidence is halved in surgery without MR.
Sebles PS, Bowdie TA, Ghoneim MM. The incidence of awareness during anaesthesia: A multi centre united states study. Anesthesia and Analgesia, 2004,99:833-839.
Types of awareness: - Explicit awareness: It is awareness with recall of any event that took place during GA either spontaneously or by direct questioning after operation. - Implicit awareness: It is awareness without recall of any event that took place during GA, but it is discovered from the behavior or performance changes that will occur at a later time after operation.
Types of perceptions during awareness: Most common: - Sounds and conversation. - Sensation of paralysis. - Anxiety and panic. - Helplessness and powerlessness. - Pain.
Least common: - Visual perceptions. - Intubation or tube. - Feeling the operation without pain.
- 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. - Bischoff P, Rundshagen I: Awareness during general anesthesia. Dtsch Arztebl Int 2011; 108(1–2):
Causes of awareness: - The cause of awareness under GA is still unknown but it may be due to:
A- Inadequate blockade of normal extra-synaptic Alpha 5 GABA A receptors subunits. - These receptors subunits (mainly present in limbic system) are the responsible receptors for memory. - Inadequate blockade of these receptors during light GA (especially with masked its clinical signs) leads to awareness during surgery.
Figure shows the effect of anesthetics on neurotransmission in the brain. A: When γ-aminobutryic acid (GABA) binds to the GABAA receptor, a pentameric ion channel, it causes a conformational change that opens the channel pore and allows the flux of chloride ions across the cell membrane. Many general anesthetics, barbiturates and benzodiazepines increase the potency of GABA at the GABAA receptor and thereby increase chloride flux. Generally, this causes membrane hyperpolarization and a reduction in the excitability of neurons. B: Extrasynaptic alpha 5 GABAA receptors subunits (responsible for memory) are particularly sensitive to general anesthetics that lead to sustained inhibition via enhanced activation of these extrasynaptic receptors with subsequent memory-blocking . genetic variations or change the number of GABAA receptor among individuals account for variable sensitivity to anesthetics. Modified with permission from Elsevier (Pharmacol Biochem Behav). Bonin RP, Orser BA. GABAA receptor subtypes underlying general anesthesia. Pharm Biochem Behav. 2008;90:105– 112.
Causes of awareness (Cont.):
B- Genetic mutation or decrease the number of extrasynaptic Alpha 5 GABA A receptors subunits: - These abnormalities make patient more susceptible for awareness during GA even with deep anaesthesia level due to resistance to the memory-blocking properties of the anesthetics.
Figure shows the effect of anesthetics on neurotransmission in the brain. A: When Îł-aminobutryic acid (GABA) binds to the GABAA receptor, a pentameric ion channel, it causes a conformational change that opens the channel pore and allows the flux of chloride ions across the cell membrane. Many general anesthetics, barbiturates and benzodiazepines increase the potency of GABA at the GABAA receptor and thereby increase chloride flux. Generally, this causes membrane hyperpolarization and a reduction in the excitability of neurons. B: Extrasynaptic alpha 5 GABAA receptors subunits (responsible for memory) are particularly sensitive to general anesthetics that lead to sustained inhibition via enhanced activation of these extrasynaptic receptors with subsequent memory-blocking . genetic variations or change the number of GABAA receptor among individuals account for variable sensitivity to anesthetics. Modified with permission from Elsevier (Pharmacol Biochem Behav).
Causes of light GA: - Giving under-dose of anaesthetic agents which may be: I- Absolute under dose i.e. 1- Giving less than adequate anaesthetic doses. 2- Declining the induction dose before starting maintenance dose as happen during difficult intubation. 3- Withholding or decreasing the level of anaesthesia in some situations as: - Caesarean section to avoid fetal depression before delivery. - Hypotension episodes to avoid more hypotension. - Cardiac surgery to avoid more myocardiac depression. - Bloody surgical procedures to avoid more hypotension. - Wake-up test during spinal or neuro-surgery to test neurological effect.
Giving under-dose of anaesthetic agent (Cont.): Absolute under dose (Cont.):
4- Equipment malfunction: - Equipment deliver inadequate dose of anaesthetic in the following situations: - In case of using inhaltional anaesthesia: - Circuit leaks or disconnection. - An empty vaporizer. - Malfunctioning vaporizer.
- In case of using TIVA : - Blockage of an i.v. infusion pump or catheter. - Disconnection from the cannula. - Extravascular location of the cannula.
5- Premature discontinuation of anesthetic at end of operation.
Giving under-dose of anaesthetic agent (Cont.):
II- Relative under anaesthetic dose: - This can happen if the usual anaesthetic doses are given in conditions which need more than usual doses as in: - Pyrexia . - Uncontrolled hyperthyroidism. - Obesity. - Anxiety. - Young age. - Chronic tobacco smoking. - Chronic heavy alcohol use. - Chronic use of opioids, amphetamines, cocaine. - Chronic use of sedatives (e.g. temazepam). - Repeated exposure to anaesthetic agents.
Methods of masking (blocking) clinical signs of light anaesthesia: - Masking (blocking) clinical signs of light anaesthesia deprive patient from giving supplemental anaesthetic doses to increase the depth of anaesthesia.
Signs of light GA and the method of their blockade: - Movement: It is blocked by MR. - Tachycardia: It is blocked by B-blockers and by some conditions as heart block or autonomic neuropathy. - Hypertension: It is blocked by vasodilators, B-blockers and by some conditions as heart block, autonomic neuropathy, hypothyroidism. - Sweating: It is blocked by atropine, glycopyrolate etc. - Tears: It is blocked by atropine and glycopyrolate. - Pupilary dilatation: It is blocked by opioids, atropine (misleading), and eye pathology.
Consequences of awareness during GA: 1- Anaesthetist related consequences: - These are the following: a- Stress state. b- Medico legal implication: - ASA closed claims project reported that 2% of all claims against anaesthetists were related to awareness during anaesthesia. - This rate is similar to those for aspiration or myocardial infarction.
2- Patient related consequences: -These range from no effect, anxiety, fear of surgery and anaesthesia and sleep disturbances to flashbacks, nightmares and post-traumatic stress disorder (PTSD). Kent CD: Awareness during general anesthesia: ASA Closed Claims Database and Anesthesia Awareness Registry. ASA Newsletter 74(2): 14-16, 2010 Samuelsson P, Brudin L, Sandin RH. Late psychological symptoms after awareness among consecutively included surgical patients. Anesthesiology 2007;106:26-32
Diagnosis of PTSD: - There are 6 main diagnostic criteria for PTSD.
- These are presented in the following table. Table : Shows 6 main diagnostic criteria for PTSD.
The 6 main diagnostic criteria for PTSD are: 1- Intense fear, helplessness, horror. 2- Recurrent recollections of the traumatic event, including images, thoughts or dreams. 3- Persistent avoidance of thoughts, feelings, conversation, or activities associated with the event. 4- Persistent inability to sleep (not present before the trauma). 5- Duration of the disturbance is more than 1 month. 6- The symptoms cause significant social and occupational impairment.
Measure to avoid awareness during GA: Pre-operative measures: - Identification of risk factors that may be associated with awareness during anaesthesia. - These risk factors which are presented in the following table include: Table: The risk factors that may be associated with awareness during anaesthesia.
Patient-related
Anesthesia-related
Surgical-related
- Female. - Young age. - Obesity. - Limited hemodynamic reserve. - History of awareness. - Genetic resistance to anesthetic effects. - Increased anesthetic requirement. - Chronic usage of opioids.
- Light anesthesia. - History of difficult intubation. - Use of muscle relaxants. - Use of nitrous oxide-opioid GA - Defective anesthesia delivery system. - Insufficient knowledge of awareness. - Not available brain function Monitors.
- Obstetrics. - Cardiac procedures. - Trauma surgery. - Emergencies. - Extensive surgery. - Rigid bronchoscopy - Microlaryngeal endoscopic surgery using jet ventilation.
- ASA III & IV.
Measure to avoid awareness during GA (Cont.):
Intra-operative measures: - Give regional anaesthesia if possible. - But if f GA is indicated, the following should be done: a- Pre-induction check the function of anesthesia delivery system: In case of inhalational anaesthesia: - Chick vaporizers to ensure that they are full and low levels alarms if present are functioning. - Chick anaesthesia circuit to ensure that no leak. In case of TIVA: - Chick infusion pumps to ensure that it function will. - Chick Infusion circuit to ensure that no leak. - Chick intravenous cannulae to ensure that it is appropriately placed and functioning will. b- Prophylactic pre-induction administration of benzodiazepines (midazolam 5mg) in the anesthetic regimen to reduce the risk of awareness via anterograde amnesic effect.
Measure to avoid awareness during GA (Cont.): Intra-operative measures (Cont.):
c- Giving the optimal anaesthetic dose to achieve sensory, motor, reflex and mental block. - MAC should be given within 0.8-1.0 to reduce the risk of awareness. d- Rapid optimization of the depth of anaesthesia especially at times of increased noxious stimulation as during intubation and sternotomy. e- Muscle relaxants should be avoided if possible. f- Maintaining quiet operating room, or giving the patient acoustic protection. g- Monitoring depth of anaesthesia to avoid the consequences of a too light anaesthesia as intraoperative awareness and too deep anaesthesia as postoperative morbidity and mortality.
Methods of assessing depth of anaesthesia: - These are the following:
A- Subjective methods as: - Autonomic response. - Isolated forearm technique.
B- Objective methods (i.e. by specialized equipment): 1- Electroencephalogram and derived indices: • Compressed spectral array/ Spectral edge frequency/ Median frequency. • Bispectral index. • Entropy. • Narcotrend index. • Patient state index. • Snap index. • Cerebral state index.
2- Evoked potentials: • Somato-sensory evoked potentials (SEP). • Visual evoked potentials (VEP). • Auditory evoked potentials (AEP). • Auditory evoked potential index.
Methods of assessing depth of anaesthesia (Cont.):
Subjective methods: These rely on: - The movement and autonomic response to stimuli.
- The opinion and experience of an anaesthetist.
- Signs of light anaesthesia: - Without MR: Facial grimacing or movement - With muscle relaxants: of limbs. Hypertension, tachycardia, tearing and sweating.
- Signs of deep anesthesia: - In spontaneously breathing patient: Hypotension, bradycardia, hypoventilation or apnea. - In mechanically ventilated patients: Hypotension and bradycardia.
Methods of assessing depth of anaesthesia (Cont.):
Objective methods (by specialized equipment): - Theses rely on the sensitivity of the monitoring system. - The monitoring systems can be subdivided into two groups: a- Those that process spontaneous electroencephalographic (EEG) and electromyographic (EMG) activity. b- Those that acquire evoked responses to stimuli ( e.g. AEPs). - Both groups provide information about the hypnotic state of the patient. Bispectral index (BIS) monitoring: - It is commonly used method to measure the depth of anaesthesia. Bispectral Index Values and meaning: 100 Awake. <100 - 60 Sedation. <60 - 40 GA < 40 - 20 Deep hypnosis. <20 Burst suppression. 0 No electrical activity.
Identification of patient with awareness postoperatively: - Interview of surgical patients should be carried out on three occasions: - Before the postanesthesia care unit (PACU) discharge. - Then 1-3 days after operation. - Then 7-14 days after operation.
Identification of patient with awareness postoperatively (Cont.):
- The detection of awareness depends on: - The interview technique. - Timing and frequency. - Structure of the interview. - The most used structure of the interview for awareness detection is the one which introduced by Brice et al (1970) and then modified by Liu et al (1991) to includes 5 instead of 4 questions: - What is the last thing you remember before surgery? - What is the first thing you remember after surgery? - Do you remember anything happening during surgery? - Did you have any dreams during surgery? - What was the worst thing about your surgery? Brice DD, Hetherington RR, Utting JE. A simple study of awareness and dreaming during anaesthesia. British Journal of Anaesthesia 1970;42;535-542 Liu WHD, Throp TA, Graham SG, et al: Incidence of awareness with recall during general anaesthesia. Anaesth; 1991, 46:435-7.
Management of patient with postoperative psychological disorders: - Anaesthetist should take complaints about awareness seriously and discuss them with the patient. - Anaesthetist should give a general description about the symptoms of psychological disorders that associate with awareness especially those of post-traumatic stress disorder (PTSD): - Anxiety states. - Sleeplessness. - Nightmares. - Irritability. - Depression. - Suicidal thoughts. - Anaesthetist should explain the seriousness of PTSD. - Anaesthetist should explain that early treatment of PTSD gives good prognosis and avoid changing to chronic condition. - Anaesthetist
should provide professional help via psychologist, psychiatrist and psychotherapist.
Conclusion: - Patient awareness during GA is a rare but very serious problem for both anesthetist and patient. - Prevention may not be completely possible but the incidence can be reduced by training of staff to know about this problem, identification of patients at risk, usage regional anaesthesia if possible, equipment checks, use of benzodiazepines, avoidance of muscle relaxants if possible, administration of adequate anesthesia, shielding the patient from excessive noise and careful physiologic and brain function monitoring. - Should the complication occur, then it is appropriate to interview the patient, acknowledge the problem, attempt to determine the reason, provide professional psychological help and assure the patient that subsequent anesthesia may not necessarily have the same outcome.
Thank you
Limbic System: Structures and functions: Amygdala - almond shaped mass of nuclei involved in emotional responses, hormonal secretions, and memory. Cingulate Gyrus - a fold in the brain involved with sensory input concerning emotions and the regulation of aggressive behavior. Fornix - an arching, fibrous band of nerve fibers that connect the hippocampus to the hypothalamus. Hippocampus - a tiny nub that acts as a memory indexer -- sending memories out to the appropriate part of the cerebral hemisphere for long-term storage and retrieving them when necessary.
Hypothalamus - about the size of a pearl, this structure directs a multitude of important functions. It is responsible for waking up in the morning, and controlling adrenaline secretion. The hypothalamus is also an important emotional center, controlling the molecules that make one feel exhilarated, angry, or unhappy. Olfactory Cortex - receives sensory information from the olfactory bulb and is involved in the identification of odors.
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