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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

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

Document Control NRClinical Department, ALARIS Medical Systems International 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

Document Control NRClinical Department, ALARIS Medical Systems International Incidence of explicit recall Hutchinson % 656 Harris % 120 McKenna % 200 Wilson % 490 Flier % 140 Liu % (0.3)1000 (684) Nordström % (0.2)1000 (1000) Ranta %2612 Myles % Sandin % (0.18) (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.

Document Control NRClinical Department, ALARIS Medical Systems International 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.

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

Document Control NRClinical Department, ALARIS Medical Systems International 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.

Document Control NRClinical Department, ALARIS Medical Systems International 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

Document Control NRClinical Department, ALARIS Medical Systems International 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

Document Control NRClinical Department, ALARIS Medical Systems International 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

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

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

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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International The auditory Pathway

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

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

Document Control NRClinical Department, ALARIS Medical Systems International 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!

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

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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

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

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International Pa Nb Pa Nb

Document Control NRClinical Department, ALARIS Medical Systems International NN 11 NN 11

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

Document Control NRClinical Department, ALARIS Medical Systems International 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.

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

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

Document Control NRClinical Department, ALARIS Medical Systems International 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.

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

Document Control NRClinical Department, ALARIS Medical Systems International 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.

Document Control NRClinical Department, ALARIS Medical Systems International 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.

Document Control NRClinical Department, ALARIS Medical Systems International 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

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

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

Document Control NRClinical Department, ALARIS Medical Systems International MTA 256 sweeps MTA 18 sweeps Moving time Averaging and ARX ARX -model 257

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

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

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

Document Control NRClinical Department, ALARIS Medical Systems International 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

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

Document Control NRClinical Department, ALARIS Medical Systems International 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

Document Control NRClinical Department, ALARIS Medical Systems International 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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

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

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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International Operation over

Document Control NRClinical Department, ALARIS Medical Systems International Exit

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International. 2002

Document Control NRClinical Department, ALARIS Medical Systems International 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

Document Control NRClinical Department, ALARIS Medical Systems International. 2002