2. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Welcome to ALARIS AEP session Kaare Jevnaker Alaris Medical

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5. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 The patient The patient has 2 worries: 1: Will he sleep during the operation? 2. Will he wake up after the operation?

6. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 History 1965: First article about different levels of anaesthesia. (States of awareness during general anaesthesia) –Explicit and implicit memory. Different cognitive stages. Awareness today is related to Explicit recall

7. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Incidence of explicit recall Hutchinson19601.2% 656 Harris19711.6% 120 McKenna19731.5% 200 Wilson19750.8% 490 Flier19861.4% 140 Liu19910.2% (0.3)1000 (684) Nordström19970.2% (0.2)1000 (1000) Ranta19980.4 - 0.7%2612 Myles20000.11% 10811 Sandin20000.15% (0.18) 11785 (7757) Number of patients With kind permission from Dr Rolf Sandin, Kalmar, Sweden Remember being awake and recall things that were said or done during operation YearIncidence The first half is not relevant today because the anaesthesia technique has changes a lot.

8. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 The implications of undersedation –Patient remains immobilized but feels pain –Although it is occurs in only 0.1% - 0.2% of all surgeries, 23 million surgeries are performed in the U.S. each year –Resulting in 35,000 cases of surgical awareness The implications of oversedation –To avoid the possibility of surgical awareness too much hypnotics and analgesics may be administered –The patient’s recovery time is extended: higher room cost –More drugs than necessary are used: higher drug cost Why monitor sleep? It is important to think about this.

9. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Auditory Evoked Potentials

10. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Basic basic basic basic basic basic The hearing is the last sense that leaves and the first that returns during anaesthesia. AEP is just the brain response to a click stimuli through the hearing nerve AEP is a very weak electrical signal wrapped in the EEG background actvity. Let’s look at how tiny tiny this signal is.

11. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Burst Suppression We look at spikes < 3,5 uV. In contrast: An awake Pa amplitude is typically 0.7 uV. And, an asleep amplitude is typically 0.4 uV

12. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 ECG signal has approx. 400 x amplitude than the AEP signals. EEG signal has approx. 40 x amplitude than the AEP signal 400 x 40 x

13. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Extracting the evoked response Before A-Line it took too long to ”detect and present” (extract) this weak signal, because it requires advanced signal processing 1 click 128 clicks 256 clicks 1024 clicks 100 msclick

14. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 But, lets make this more visible Let’s see what happens when we send a click through the ear.

15. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 A deviation in the positioning of the electrodes up to 2 cm does not have significant influence on the ARX-index.

16. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 To Monitor Some prefer to wait with the headphones until electrodes are connected

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18. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 2 The auditory Pathway

19. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Acoustic nerve and brainstem Medial geniculate and primary auditory cortex Frontal cortex and association areas

20. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 What does the AEP Look Like? + 0.1µV 100 msec Pa Nb Pa latency Pa amplitude

21. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Basic knowledge The early cortical AEP waves called Pa and Nb, which occurs between 20 and 80 ms reflects the activity in the temporal lobe/primary auditory cortex ( the site of sound registration) Changes in the latency of these waves ( in particular the Nb wave) are highly correlated with a transition from awake to loss of consciousness Changes in the amplitude of these waves reflects the interplay of general anaesthetics,surgical stimulation and the obtunding of the latter by analgesics!

22. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 And, this is what happens

23. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Acoustic nerve and brainstem Medial geniculate and primary auditory cortex Frontal cortex and association areas

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28. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Pa Nb

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37. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Pa Nb And, of the opposite during awakening

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43. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Pa Nb

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45. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 -0.2 02 10152025 Pa Nb 0 101520 Pa Nb

46. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 NN 11 NN 11

47. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Desflurane 1.5% Pa Nb 3% 6% The AEP during Anaesthesia With kind permission from Dr Christine Thornton, Northwick Park, London, UK.

48. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Pre-intubation 100ms 0.1µV + Pa Nb Post-intubation Effect of intubation on the AEP With kind permission from Dr Christine Thornton, Northwick Park, London, UK.

49. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 The Effect of Midazolam on the AEP 010050 Time (ms) Awake Nb Loss of eyelash response With kind permission from Dr Christine Thornton, Northwick Park, London, UK.

50. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 The effect of propofol on the AEP 010050 Response to command No response to command Nb Time (ms) With kind permission from Dr Christine Thornton, Northwick Park, London, UK.

51. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Effects of opioids on the AEP Controversy exists as to whether opioids affect the AEP directly or indirectly. A study of 2 groups: –1 group was given an Opioid –1 group got normal saline prior to tracheal intubation under general anaesthesia With kind permission from Dr Christine Thornton, Northwick Park, London, UK.

52. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Opioids With kind permission from Dr Christine Thornton, Northwick Park, London, UK.

53. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Conclusions The saline group had statistically significant 50% higher increase in Pa amplitude! But, is it a direct or indirect effect? The Opioid group results could be because the pain of intubation was blunted rather than a direct effect on AEP itself. However: It demonstrates that the AEP meets the clinical expectations of a signal which monitors depth of anaesthesia. With kind permission from Dr Christine Thornton, Northwick Park, London, UK.

54. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Drawbacks of AER It will not work in deaf people. The extent to which the AEP changes are affected needs to be explored A large amount of information is produced and before the ALARIS AEP  Monitor you got the feedback too late. It took 2-3 minutes to collect an average response.

55. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Conclusions Graded changes with depth of anaesthesia Similar changes for different anaesthetics Shows response to noxious stimulation AEP indicates level of consciousness Technology has been studied since early 1980’s

56. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 AEP signal processing? How can it be so fast?

57. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 ALARIS AEP ™ signal processing v. 1.4 Bandpass filter EMG 65-85 Hz Bandpass filter Burst Suppr. 1-35 Hz Signal OK? ARX MODEL Yes AAI Calc. BS% Calc. EMG Calc. MTA 256 sweeps MTA 18 sweeps Bandpass filter AEP 25-65 Hz A/D Converter 900 x Sec. No Reject EEG + AEP + Artifact AEP MTA 256 AMP A-line Electrodes Signal OK? No Yes

58. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 1 2 3 4 5 6 7 8. 239. 256 MTA 256 sweeps MTA 18 sweeps Moving time Averaging and ARX ARX -model 257

59. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Index calculation?

60. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 AEP window = 20-80 ms x i x i+1 Index calculation? mv0,1 mv0,2 mv0,3 mv0,4 Total3,7x factor = 100

61. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Index calculation So, then you have a real curve, the index is high And, an almost flat curve gives a low index = 93 = 16

62. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 What it is AAI is typically higher than 60 when the patient is awake and decreases when the patient is anaesthetised; loss of consciousness typically occurs when the AAI is below 30

63. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Induction EMG Burst Suppression Intubation Start of surgery Utter boredom End of operation Awake A typical case

64. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Fentanyl 0,15 + Pentothal 250mg Tracrium 15mg Intubation. + Sevo FI 0,2 Moved Patient on table Start surgery. Gyn. Lap. procedure. FI 1,0 + MAC 1,0 Induction started with normal doses Index dropped and NMB was given to prepare intubation Intubation too soon. Fentanyl had not reached peak effect. Penthotal dose was small for this patient. Gas conc. too low TIVA with induction and Maintenance would have prevented this Patient was not deep enough to be moved on table. Dose of gas too low. Patient still not deep enough and reacts. Remember: 50% sleep at 1 MAC

65. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Put in trocar (insertion tube for scope) FI 1,8 + MAC 1,4 Sevo stopped FI 0,7 + MAC 0,9 At MAC 1,4 the patient is deep enough and all problems stops

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80. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Induction is given

81. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 EMG starts to drop

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85. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Burst Suppression appears

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94. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Starting to wake up

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96. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Observe Alarm and EMG

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102. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Operation over

103. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Exit

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105. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 Check and transfer DATA

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115. Document Control NRClinical Department, ALARIS Medical Systems International. 2002 A good case Just to illustrate how important it is. Customer couldn’t understand why the index was high? Complained that “something was wrong” All details captured by our man After downloading and descriptions the clinicians agreed the anaesthesia was not optimal. They could actually see things they never seen before

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