AWARENESS IN GENERAL ANAESdTHESIA-1.pptx

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1. Presented By :- Dr. Simran Saroha Moderator :- Dr. Payal Jain No. of slides - 35 1 AWARENESS DURING ANAESTHESIA

2. INTRODUCTION Awareness Anesthesia is imbalance between depth of anesthesia and stimulus to which patient is exposed. Acc to Nap 5 awareness during GA is spontaneous respiration by a patient that he/she been aware at time during anesthesia and surgery when patient is expected to be unconscious. 2

3. Despite advances in physiological monitoring and an improved understanding of the neural mechanisms, the incidence of ADA has remained steady for several decades. At present, there is a disparity between reports of ADA from patients (1-2 in 1000 ) and from anaesthesia care providers (1 in 15,000). The 5th National Audit Project (NAP5) of the Royal College of Anaesthetists,examined more than 400 individual experiences of ADA and found considerable variation in the incidence of ADA across anaesthetic techniques . 3

4. Types of awareness E xplicit memories - recalled spontaneously, or may be provoked by postoperative events or questioning. I mplicit memories - affect behaviour or performance at a later time. 4

5. Incidence Higher in women , paediatric , obstetric , and cardiac anaesthesia . A review of litigations related to ADA in the UK showed that 117 out of 159 (74%) of ADA claims were from women , and two thirds were related to obstetric care . A secondary analysis of 26,490 patients in the B-Unaware trial, BAG-RECALL trial, and MACS trial revealed that patients with a history of ADA were five times more likely to experience ADA again (relative risk 5.0; 95% CI). 5

6. Risk F actors 10-fold increase - obstetric patients and a 2.5-fold increase in cardiothoracic patients . Obesity – increases incidence three times Use of anaesthetic drugs that are typically reserved for emergencies , increased the risk of ADA. Ketamine, Etomidate and Thiopental were used most often in the ADA activity survey cohort, with ratios of 17.2, 14.3, and 8.2 , respectively, whereas Propofol’s ratio of use was 0.9 . 6

7. Incidence of ADA increased from 1 out of 135,000 general anaesthetics to 1 out of 8200 general anaesthetics when neuromuscular blocking drugs were used. Monitoring and reversal of neuromuscular block were less frequent in those with ADA. 7

8. Causes Selection of inadequate anaesthetic dose Awareness is associated with poor anaesthetic technique . Errors include :- O mission or late commencement of a volatile agent I nadequate dosing or failure to recognize the signs of awareness. Under-dosing of anaesthetic agent may occur during hypotensive episodes , when anaesthetic is withheld in an attempt to maintain arterial pressure. 8

9. Resistance to anaesthetic agents Factors associated with a degree of resistance to anaesthetic agents include: pyrexia; hyperthyroidism; obesity; anxiety; young age; tobacco smoking; regular, heavy alcohol; recreational drugs ( O pioids , A mphetamines , C ocaine ); chronic use of sedatives (temazepam); Repeated exposure to anaesthetic agents. 9

10. Factors associated with a reduction in MAC include: hypocapnia, pregnancy, hypothyroidism, hypothermia, hypotension, increased atmospheric pressure and old age. Increased atmospheric pressure does not alter brain sensitivity to anaesthetic agents, but increases the inspired and brain partial pressures for given inspired concentration. Depth of anaesthesia is related to brain partial pressure of the agent. 10

11. Equipment malfunction Breathing system malfunctions and disconnections are associated with awareness. Vaporizers malfunction having potential to deliver an inadequate dose of anaesthetic . These include: - E mpty vaporizer - M iscalibration - I mpurities in the volatile agent (reducing its saturated vapour pressure) - D isconnection from the anaesthetic machine. Blockage of an I.V. infusion pump or catheter, disconnection from the cannula or extravascular location of the cannula may risk awareness during TIVA. 11

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13. Recommendations of the Practice Advisory for Intraoperative Awareness Preoperative evaluation Review patient medical records for risk factors like: – Substance abuse or use . – Previous history of intraoperative awareness . – History of difficult intubation . – Chronic pain patients using high doses of opioids . – ASA IV/V –Limited haemodynamic reserve . – Obtain history regarding previous experience with anaesthetic s . 13

14. Determine other potential risk factors – Cardiac surgery – Caesarean section – Trauma surgery – Emergency surgery – Decreased anaesthetic doses in the presence of paralysis . – Planned use of muscle relaxants during general anaesthesia . – Planned use of nitrous oxide- opioid anaesthesia – Patients at high risk should be informed . 14

15. Pre-induction phase of anaesthesia Adhere to checklist protocol for checking of anaesthesia machine and equipment Check proper functioning of intravenous access, infusion pumps, connections and backflow valves. A dminister benzodiazepines prophylactically Intra-operative monitoring Use multiple modalities to monitor depth of anaesthesia – Clinical techniques (e.g. purposeful or reflex movement) – Conventional monitoring systems (e.g. ECG, BP, EtCO2 etc.) – Brain function monitoring not routinely indicated for all general anaesthesia cases and should be used for s elected patients (e.g. light anaesthesia ) 15

16. Clinical techniques and conventional monitoring Clinical techniques - used to assess intraoperative consciousness include checking for movement, response to commands, eyelash reflex, pupillary responses, respiratory pattern, perspiration and tearing. Conventional monitoring systems - include ECG, blood pressure, heart rate, end tidal anaesthetic analyzer and capnography Task Force recommends that clinical techniques and conventional monitoring are valuable and should be used to assess intraoperative consciousness. 16

17. Brain electrical activity monitoring: I. Spontaneous electroencephalographic activity monitors: (1) Bispectral index: The BIS converts a single channel of frontal EEG into an index of hypnotic level. Targeting a range of BIS values 40-60 is advocated to prevent awareness during anaesthesia while allowing a reduction in the administration of anaesthetic agents . 17 (2) Entropy: Entropy describes the irregularity, complexity or unpredictability characteristics of a signal. A single sine wave represents a completely predictable signal (entropy=0) whereas noise from a random number generator represents entropy =1 .

18. (3) Narcotrend The Narcotrend is derived from a system developed for the visual classification of the EEG patterns associated with various stages of sleep . A (awake), B (sedated), C (light anaesthesia ), D (general anaesthesia ), E(general anaesthesia with deep hypnosis), F (general anaesthesia with increasing burst suppression). (4) Patient State Analyser Patient state index (PSI) is derived from a four channel electroencephalograph . Derivative of the Patient State Index is based on the observation that there are reversible spatial changes in power distribution of quantitative EEG at loss and return of consciousness. PSI - range of 0-100 with decreasing values indicates lower levels of consciousness and sedation 18

19. (5) SNAP index The SNAP II calculates a “SNAP index” from a single channel of EEG. The index calculation is based on a spectral analysis of EEG activity in the 0-18 Hz and 80-420 frequency ranges and a burst suppression algorithm. (6) Cerebral State Monitor This is a hand held device analyses a single channel EEG and presents a Cerebral State “Index” scaled from 0-100. It also provides EEG suppression percentage and a measure of electromyographic activity (75-85 Hz) 19

20. II. Evoked brain electrical activity monitors: Auditory evoked potentials are the electrical responses of brain stem , auditory radiation and auditory cortex to auditory sound stimuli delivered via headphones. The brainstem response is relatively insensitive to anaesthetics , whereas early cortical responses called midlatency auditory evoked potentials (MLAEPs) change in a predictable manner with increasing concentrations of volatile and intravenous anaesthetics . Increasing anaesthetic concentrations lead to an increased latency and reduced amplitude of the various waveform components. AEP index is scaled from 0-100 and corresponding with a low probability of consciousness is <25. 20

21. The patient’s experience of awareness during general anaesthesia Many patients first reported ADA during preparations for a subsequent procedure, as patients became understandably anxious about having general anaesthesia. These findings highlight the need to perform postoperative checks on patients and may explain the disparity between patients’ and anaesthetists’ reports of ADA. NAP5(5th National Audit Project) found that in 47% of ADA cases, the recall of ADA was described in a neutral way, involving few isolated aspects of the experience, such as auditory and tactile memory. 21

22. However, the other 53% of the ADA events were associated with distress . The primary causes of distress were paralysis and pain. Not surprising, all forms of distress were strongly associated with long-term psychological consequences, such as flashbacks , insomnia, fear of future surgery , and PTSD . 22

23. Psychological assessment and diagnosis Patients in the NAP5 study described feelings of panic , extreme fear , dissociation , suffocation , and fear of dying . Distress of ADA - emerge soon after the event , qualifying it as an acute stress disorder (ASD) . Presence of nine symptoms or more from the five categories of intrusion, negative mood, dissociation, avoidance, and arousal is required to make the diagnosis of ASD. 23

24. Diagnosis of ASD ranges between 3 days and 1 month after exposure to the traumatic event . Sleep disturbance, irritable behaviour, and angry outbursts that are typically expressed as verbal or physical aggression toward people or objects are seen in ASD. In addition, patients may display hypervigilance, concentration difficulties, and an exaggerated response. 24

25. Post-traumatic stress disorder is diagnosed when these symptoms last for more than 1 month after a traumatic event. The traumatic event is persistently re-experienced with upsetting memories, nightmares, flash backs, distress after traumatic reminders, and physical reactivity after exposure to trauma reminders. The Psychological Sequelae of Surgery Study (Psych SOS) ---The study confirmed that experiencing ADA substantially increased the risk of PTSD. 25

26. The risk factors for post-surgical PTSD included -Poor social support -History of PTSD -Prior mental health treatment -Dissociation related to the surgery -Perceiving that one’s life was in danger during surgery -Intraoperative awareness. Recognising these risk factors during patient screening can be useful for promoting early diagnosis and treatment referrals. 26

27. Management N o specific treatment guidelines for ADA. S elective serotonin reuptake inhibitors (SSRIs) are recommended as first-line medication for PTSD because they can reduce symptoms of re-experiencing, avoidance, numbing, and hyperarousal.They may reduce symptoms such as suicidality, impulsivity, and aggression that complicate the management of PTSD. Paroxetine  can be started at 20 mg/day orally. If minimal or no clinical response is seen after three to four weeks, we typically increase the dose in 10 to 20 mg/day increments with at least two weeks between dosing increases, up to 60 mg/day. Sertraline  can be started at 25 or 50 mg/day orally. If minimal or no clinical response is seen after three to four weeks, we typically increase doses in 25 to 50 mg/day increments with at least two weeks between dosing increases, up to 250 mg/day. 27

28. Benzodiazepines (potential for abuse) may reduce acute anxiety and help with sleep, but they have not been establised to prevent ASD or PTSD . Anticonvulsants such as divalproex, carbamazepine, topiramate, and lamotrigine may help treat re-experiencing symptoms of nightmares and flashbacks. Early supportive psychotherapeutic interventions, along with psychoeducation can be very beneficial after acute trauma . Cognitive behavioural therapy (CBT) with exposure component. Stress inoculation , imagery rehearsal , prolonged exposure reduce PTSD-associated anxiety and avoidance symptoms . 28

29. The NAP5 awareness support pathway emphasises the importance of: ( i ) face-to-face postoperative meeting with patients that experience ADA . (ii) early consultation with a psychiatrist or psychologist and early assessment of flash backs, nightmares, new level of anxiety, and depressed mood . (iii) active follow-up at 2 weeks to assess for new or ongoing needs for treatment referrals. 29

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33. Personal and medicolegal implications of awareness It is advisable that the anaesthetist always records the timing and dose of anaesthetic agents , and the timing of the start and end of surgery . The anaesthetist should establish the perioperative timing of the episode and distinguish between dreaming and awareness. The details of recalled events (e.g. hearing conversations, feeling the incision) should be noted in the patient’s records. A formal and detailed interview should take place with the patient and this must be summarized in the records. 33

34. Conclusions Awareness under general anaesthesia is associated with ASD and PTSD in patients who experience distress , such as paralysis and pain during the event. S ignificant depression affects 30 - 50% of patients diagnosed with PTSD, drug treatment with antidepressants in combination with cognitive behavioural therapy can be helpful. All reports of ADA should be taken very seriously and institutional guidelines should be in place to follow the NAP5 awareness support pathway. Anaesthetists should be aware of the risk factors for ADA and choose their anaesthetic plan carefully, especially regarding use of neuromuscular blocking drugs and TIVA . 34

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