BIS AND ENTROPY IN ANAESTHESIA MANAGEMENT

BIS AND ENTROPY MONITROING IN ANAESTHESIA

1. BIS & ENTROPY Nur Izzatul Afiqah Binti Mohd Shakri

2. CONTENTS DEPTH OF ANAESTHESIA ELECTROENCEPHALOGRAPHY (EEG) BIS ENTROPY

3. DEPTH OF ANAESTHESIA Before anesthetic monitors were developed, physical examinati on was the only way to assess a patient’s anesthetic depth. 1847, John Snow proposed a system of classification of the depth of anaesthesia that involved 5 stages of so called “ etherization ”. Few decades later, Dr Arthur Guedel developed a systemic approach to determine a patient’s anaesthetic depth which the called Guedel’s Stages of Anaesthesia

4. GUEDEL’S STAGES OF ANAESTHESIA

5. 1957- Dr. Philip D Woodbridge defined 4 components of anaesthesia Sensory Blockade of afferent impulses Motor Blockade of efferent impulse Reflex blockade of Resp , CVS, GI tract Unconsciousness 1987- Prys-Robert define anaesthesia as state in which patient neither perceive nor recall noxious stimuli as a result of drug induced unconsciousness

6. Why it is important to know the depth of anaesthesia?

7. INTRAOPERATIVE AWARENESS I ntraoperative awareness  with recall refers to intraoperative consciousness, in cases in which unconsciousness is expected , and postoperative explicit recall of operative events. 

8. IMPLICATIONS OF AWARENESS Psychological Sequale Sleep disturbance Nightmares Anxiety and panic attacks Flashbacks PTSD Avoidance of medical care

9. BRICE QUESTIONNAIRE Universally use to identify potential awareness event

10. HOW TO REDUCE THE INCIDENCE ???

11. METHODS OF MONITORING DEPTH OF ANAESTHESIA Clinical techniques and conventional monitoring Pharmacological eg inhalational agents (MAC) Brain electrical activity monitoring eg BIS, entropy, conox

12. ELECTROENCEPHALOGRAPHY Involves placement multiple electrodes on patient’s scalp to measure the electrical activity of the brain

13. Where are these electrodes placed International 10-20 system

14. HOW EEG WORKS

15. HOW EEG WORKS?? RESTING POTENTIAL

16. DEPOLARIZATION

17. HYPERPOLARIZATION

18. CREATION OF EEG SIGNAL

19. EEG FREQUENCY BANDS DELTA 0.5 TO 2HZ THETA 3 TO 7HZ ALPHA 8 TO 12 HZ BETA 13 TO 24HZ GAMMA 25 TO 55HZ

20. DELTA WAVES Frequency 0.5 to 2Hz Slowest frequency but high amplitude waves Found in frontocentral brain area Mainly can be seen in infants and young children, and in adults during deep sleep Delta waves are indicator of sleep pressure and are associated with restorative, healing sleep Delta waves are abnormal in awake adults and can be sign of brain injuries, learning problems, ADHD and brain disorders

21. THETA WAVES Frequency 3 to 7Hz High amplitude waves Found in parietal and temporal regions Prominent in children and adolescents Associated with light sleep and daydreaming Excessive theta waves in adult may suggest ADHD or stress

22. ALPHA WAVES Frequency 8 to 12Hz Smooth and sinusoidal Found in occipital regions Can be seen at the age of 3 years and does not decline until ninth decade of life Occur during wakeful rest, that it’s not processing a lot of information or solving big problem

23. BETA WAVES Frequency 13 to 24Hz Low amplitude Prominent in frontal and parietal region Most frequently seen rhythm in normal adults and children Can be detected when someone is awake, alert and actively processing information Excessive beta activity may indicate hypervigilance or restlessness.

24. GAMMA WAVES Frequency 25 to 55HZ Fastest brain waves Can be detected in many areas (visual, premotor, parietal, temporal and frontal cortical) Most prominent when alert and attentive Associated with c ognitive processing, learning, memory, and perception.

25. EEG DURING ANAESTHESIA

26. EEG is time consuming and impractical and requires expert interpretation to In its unprocessed form it is not practical tool for monitoring dept of anaesthesia

27. BISPECTRAL INDEX Developed by Aspect Medical System in 1987 in Massuchettes Is a complex mathematical algorithm that interprets raw EEG data gathered from frontal forehead electrodes Value ranging from 0 to 100

28. Calculation of BIS

29. EQUIPMENTS Sensor – disposable wet gel electrodes Cable Monitoring module

30. Placement of BIS electrodes https:// youtu.be / ydEYQ9Ncczs ? si =GamEIJEMwkAD2dQt

31. BIS Monitoring System Display BIS value EEG waveform BIS trend EMG Signal quality index (SQI)

32. Target range between 40 and 60 is the proposed range in which patients have lower risk of intraoperative awareness with recall during anaesthesia

33. Interpreting BIS values

34. Effects of Common Anaesthetics on BIS

35. BENEFITS OF BIS MONITORING Non invasive Enhance patient target approach to induction, maintenance and emergence. Decrease intraoperative awareness Decrease occurrence of delayed extubation, delirium

36. Limitations of BIS Unreliable with certain anaesthetic such as ketamine and nitrous oxide It is difficult to titrate anaesthetic agents in infants younger than 6 month of age Wide variation in BIS value in patient with hypothermia Not a reliable tool to assess the level of consciousness in neurological impaired patients Inaccurate placement or decrease adherence of EEG leads increase electrode impedance and may lead to falsely elevated BIS values.

37. ENTROPY

38. ENTROPY In thermodynamics it has been defined to describe the state of a gaseous or fluid system and the distribution probability of molecules Adapted by Claude E. Shannon in which measure the predictability of future amplitude values of EEG based on probability of amplitude values already observed in signal

39. HOW IS ENTROPY CALCULATED?? Measure of irregularity in any signal EEG changes from irregular pattern to more regular pattern when anaesthesia deepens Entropy measure these changes by quantifying the irregularity of EEG and FEMG signals

40. PARAMETERS OF ENTROPY RESPONSE ENTROPY (RE) STATE ENTROPY (SE)

41. Response Entropy (RE) Measures both EEG and high-frequency EMG signals ( 0.8 to 47 Hz). Sensitive to activation of facial muscles like FEMG Fast response time, less than 2 second Increase of RE value to painful stimuli may be interpreted as inadequate analgesia

42. STATE ENTROPY Calculated from EEG signal in the frequency range of 0.8 to 32Hz It is reflect the cortical brain activity in which it can estimate hypnotic effect of anaesthetic drug in the brain during GA Not affected by sudden reaction of facial muscle

43. SETTING UP ENTROPY MODULATOR

44. WIRE ELECTRODES MONITOR

45. PLACEMENT OF ELECTRODES FOREHEAD One electrode placed in the midline 2cm above the eyebrows, and the other is placed 2cm laterally from outer canthus of left eye

46. ENTROPY RANGE GUIDELINE

47. CLINICAL USE OF ENTROPY

48. COMPARISON BIS AND ENTROPY ASPECT BIS ENTROPY SIGNAL TYPE EEG EEG + EMG METRICS SINGLE BIS VALUE (0 TO 100) SE AND RE (0 TO 100) RESPONSE TIME SLOWER (CORTICAL ONLY) FASTER APPLICATIONS CORTICAL ANAESTHESIA DEPTH DEPTH + MUSCLE ACTIVITY

49. KEY TAKEAWAYS BIS and Entropy improve safety and precision in anaesthesia. Both reduce the risk of awareness and anaesthetic complications. Effective use requires understanding their strengths and limitations

50. REFERENCES

51. MORGAN & MIKHAIL’S CLINICAL ANAESTHESIOLOGY STOELTING’S American Society of Anaesthesiologist: Clinical Electroencephalography for Anaesthesiologist GE Healthcare quickguide : Entropy https:// resources.wfsahq.org / atotw / bispectral-index -monitoring-and- intraoperative -awareness/ https:// www.ncbi.nlm.nih.gov /books/NBK539805/ https:// www.openanesthesia.org /keywords/ stages-of-anesthesia/

52. ANY QUESTION?

53. THANK YOU