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Reactivity of propofol and isoflurance induced EEG burst suppression pattern
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Electroencephalography and clinical Neurophysiology 95 (1995) 95P-97P
Society proceedings
The Finnish Society of Clinical Neurophysiology Tampere, 3 February 1995
Secretary:
Dr. T. Salmi
Di~'. of Clinical Neurophysiology, Dept. of Neurology, Uni~,er~i~ Hospital. Helsinki 00290, Finland Received for publication: 29 March 1995
1. Changes in ECG T-wave amplitude during anaesthesia. - P. Annila (Tampere University Hospital, Tampere) Changes in the ECG T-wave amplitude during anaesthesia with different anaesthetic agents were studied in 75 patients and 10 vohmteers to ascertain whether T-wave amplitude changes have clinical significance in anaesthesia practice. ECG lead CB5 (central back lead) was monitored on-line during the anaesthesia studies and recorded on tape for later quantitative analysis. Laryngoscopy and intubation produced T-wave flattening together with sympathoadrenal response in both inhalation and intravenous anaesthesia. T-wave flattening correlated with heart rate increase. After skin incision the T-wave decreased in moderate deep 1 MAC (ET 1.15%) isoflurane anaesthesia but during light (ET 0.7%) isoflurane anaesthesia it either increased or decreased. Circulating plasma catecholamine levels did not correlate to T-wave changes after skin incision and plasma potassium levels did not change despite marked T-wave alterations. T-wave changes were very rapid, occurring within seconds. Atropine 20 m g / k g was found to produce total parasympathetic block in volunteers, abolishing respiratory sinus arrhythmia almost completely. T-wave flattened at deep burst suppression anaesthesia level after atropine. It was concluded that during parasympathetic block sympathetic tone takes over, flattening the T-wave amplitude. The T-wave may therefore reflect the balance of the entire autonomic nervous system, not only increased sympathetic tone. Alfentanil 30 m g / k g given 5 min after skin incision produced T-wave flattening in correlation to a decrease in diastolic arterial pressure. During laryngoscopy and intubation alfentanil prevented the sympathoadrenal response, and neither T-wave flattening nor cardiac arrhythmias were seen. T-wave changes can be easily followed by eye in ECG monitoring during anaesthesia. T-wave flattening may reveal excessive sympathoadrenal tone and predict arrhythmias, but also an excessive decrease in arterial pressure can be suspected from T-wave flattening.
2. The effect of nitrous oxide on EEG and median nerve somatosensory evoked potentials during isoflurane anaesthesia. - T. Porkkala (Dept. of Anaesthesiology, Tampere University Hospital, Tampere) Recent studies show that nitrous oxide activates EEG when combined to isofiurane in burst suppression level of anaesthesia. Somatosensory evoked potentials (SEPs) show a substantial decrease in cortical N20 amplitude, when nitrous oxide is combined with isoflurane. Earlier we have shown that N20 is recordable during isoflurane-induced suppression.
We studied 13 patients scheduled for orthopaedical and abdominal surgery, they were anaesthetised with isoflurane until burst suppression. Simultaneous EEG and SEP were obtained during randomly selected periods of isoflurane-air-oxygen and isoflurane-nitrous oxide-oxygen anaesthesia. Nitrous oxide caused a marked ( P < 0.05) decrease in proportion of EEG suppression by 21%. At the same time the amplitude of the N20 component decreased, and only in 5 out of 13 patients the N20 could be obtained reliably. The different effects of nitrous oxide on EEG and SEP shown in this study are interesting. The effect of nitrous oxide on brain-stem reticular centres has been proposed as a mechanism of activation of the EEG in earlier reports. These participate in the generation of SEP but other levels are involved as well and the decrease in SEP may be due to the effect of isoflurane and nitrous oxide at thalamic or cortical level.
3. Visual evoked potential mapping in propofol anaesthesia. - K. M~ikel~i, H. Heikkilii and K. Kailiovalkama (Dept. of Clinical Neurophysiology and Anaesthesia, Seiniijoki Central Hospital, Sein~ijoki) We have recorded the EEG of 8 patients during propofol anaesthesia with a 21-channel digital brain mapping system. The anaesthesia level was deepened to burst suppression stage, during which the patients underwent visual stimulation with a standard discharge-tube flash stimulator. The VEP response was obtained off-line by summation techniques after the termination of the recording. The VEP response obtained during burst activity was of a longer latency (P100 mean 150 msec) than during the awake state. No VEP responses were seen during the suppression stage. Preliminary results do not indicate significant differences in VEP topography between the awake and burst suppression stages for the VEP response. During anaesthesia, however, a very short latency (40-75 msec) response is occasionally evident. The nature of this short latency response is unclear but could be due to suppression of thalamic inhibitory mechanisms.
4. Reactivity of propofol and isoflurane induced EEG burst suppression pattern. - K. Hartikainen, M. Rorarius, G. Baer and V. Jiintti (Dept. of Clinical Neurophysiology, Tampere University Hospital, Tampere) In moderate and deep anaesthesia the EEG shows burst suppression pattern and high voltage activity alternating with suppressed background activity. We compared propofol and isoflurane induced burst suppression and its reactivity to visual and painful stimulL We anaesthetised 12
0013-4694/95/$09.50 © 1995 Elsevier Science Ireland Ltd. All rights reserved
SSDI 0 0 1 3 - 4 6 9 4 ( 9 5 ) 0 0 0 7 3 - 9
EEG 95549
96P
Society Proceedings/Electroencephalography
patients with continuous propofol infusion and another 12 patients with isoflurane until burst suppression occurred in the EEG. The EEG was recorded for 0.5 h before the operation. The patients were given visual stimulation with flashes of red LED goggles or painful electric stimulation on the median nerve, both consisting of trains of 3 sec at a frequency of 20 Hz. Propofol induced burst suppression is characterised by lower amplitude and slower DC shifts at burst onset than isoflurane induced bursts. During propofol burst suppressions 13 Hz spindles, maximal in the frontocentral region, are seen both during bursts and suppressions, and during suppressions they are on the negative side of the positive suppression level. Both the onset and end of trains of visual and painful stimuli frequently evoked bursts in isoflurane induced burst suppression. In most patients there was no correlation between visual or painful stimulus and the occurrence of bursts in propofol induced burst suppression. The different EEG patterns and different reactivity in isoflurane and propofol induced burst suppression suggest different mechanisms of action, probably at the thalamic or cortical level.
5. Auditory event-related waveform to semantic congruency in children. - K. Juottonen, A. Revonsuo and H. Lang (Centre for Cognitive Neuroscience, University of Turku, Turku) Sixteen healthy children, 6 boys and 10 girls, ranging in age from 5.6 to 11.9 years, were presented with 160 naturally connected speech sentences as stimuli. 50% of the sentences ended with a semantically incongruous but syntactically correct word. The congruous and incongruous sentences appeared in random order. ERPs to both types of terminal words were separately averaged and analysed by ANOVA for repeated measures. The statistical analyses for the time windows of 400-600, 600-800, 800-1000, 1000-1200 and 1200-1700 msec revealed a significantly larger negative component to incongruous words than to congruous words, widely over the cortex in the time window of 400-1000 msec. The ERP waveform in children, probably related to the N400 in adults, displayed a right hemisphere predominance of long duration. The distinct long-duration N400-1ike wave elicited by semantic violation with naturally connected speech proves the acquisition and semantic organization of concepts in long-term memory in children.
6. The rationale of measuring the mismatch negativity (MMN) variables. - H. Mikola, H. Lang, T. Kiirki, S. Salo and P. Korpilahti (Dept. of Clinical Neurophysioiogy, University of Turku, Turku) There are no widely accepted rules to analyse the MMN variables. We used the Origin TM (Microcal Inc.) software with user defined macros to analyse amplitude, latency, duration and area variables. The variables were measured semi-automatically from the averaged individual MMN responses evoked with different auditive stimuli. In defining the MMN response we had two simple rules: the onset latency had to be over 45 msec and the peak latency between 100 and 200 msec. A total of 18 variables (e.g. peak, mean and half-area amplitude, onset, peak, offset and half-area latencies, rise time, total duration) based on either a straight baseline (from onset point) or a trend-fixed baseline (from onset to offset point) were calculated. Baseline corrected area and baseline corrected mean amplitude had the lowest variability between different test subjects (n = 140, 20-60 years). The correlation between experienced scorers varied from 0.56 (offset latency) to 0.97 (mean amplitude). To estimate the sensitivity of different variables we compared how the variables or the ratios of variables reflected the physical or physiological parameters: the characteristics of the stimulus, i.e., sound pressure or pitch difference, the maturity of the brain or the effect of ageing. The validity of the variables was tested by analysing whether they distinguished normal from dysphasic children. The methods described will contribute to rationalise and improve the signal analysis of MMN responses.
and clinical Neurophysiology 95 (1995) 95P-97P 7. Is there a late-latency mismatch negativity (MMN) component? P. Korpilahti, H. Lang and O. Aaltonen (Centre for Cognitive Neuroscience, University of Turku, Turku) We have registered a late-latency waveform following the MMN when using complex auditory stimuli. The waveforms were analysed in 2 age groups: adults (n = 13, age 21-32 years, stimulus pair consisted of prototypical and non-prototypical vowels i and y), and children (n = 15, age 5 - 1 0 years, stimulus pair consisted either of sine wave tones or words). In adults, the non-prototypical vowels especially elicited both an early negativity (the MMN) as well as a slightly smaller later negativity (latency about 400 msec) that were approximately the same in distribution (maximum at electrodes Fz or Cz). In children, the sine wave stimuli elicited only an early negativity ( - 1 3 + 9.4 /xV), whereas the verbal stimuli elicited an additional later ( - 21.1 + 10.9/zV) frontocentral negativity that was larger in amplitude, but of the same latency, in pre-school than in older children (mean 432 _+ 33 msec). The amplitudes of early and later negative wave forms are significantly correlated in the word paradigm (r = 0.685, P = 0.014). It is apparent that the later waveform reflects the automatic processing of complex auditory, possibly even linguistic, stimuli.
8. ERPs in impulsive violent offenders. - J. Karhu, J. Partanen, J. Tiihonen, J. Kuikka, A. PiiiikkOnen, K. Bergstrrm and P. Hakola (Dept. of Clinical Neurophysiology, University of Kuopio, Kuopio) We investigated habituation of N100, MMN and auditory P300 in violent offenders. Event-related potentials (ERPs) were compared with central serotoninergic and dopaminergic functions studied by /3-CIT SPECT. We studied 10 subjects (males; mean age 28 years; range 19-43 years) who had committed previous impulsive violent offences and were subjected to forensic psychiatric examination, and age-matched control subjects. For 21-channel auditory ERPs, 800 Hz tone pips were delivered in stimulus trains with a 12 sec intertrain interval. Each train consisted of 4 tones with an interstimulus interval of 1 sec. In auditory "oddball" paradigm 85% of standard 800 Hz and 15% of deviant 560 Hz tones were delivered in non-attended and attended conditions. The habituation of N100, MMN and P300 parameters were measured. An ~z31-1abelled cocaine congener, [123I]fl-CIT, was used for initial SPECT imaging of summed serotonin and dopamine re-uptake, subsequently separated by treatment with citalopram. Habituation of auditory N100 was significantly impaired in violent offenders and correlated positively (proportion of explained variance 60%) with a profound decrease in medial prefrontal cortex serotonin transporter visible in SPECT. The results suggest that frontal lobe serotonin system modulates automatic sensory responsiveness, which is impaired in violent offenders.
9. Recording of nasal breathing using the piezoelectric transducer. J. Siivola (Dept. of Clinical Neurophysiology, Kainuu Central Hospital, Kajaani) Recording of respiration is one of the most important physiological parameters in polysomnography. In this study a new method for recording of nasal breathing is presented. The detector for recording consists of a pad of polyvinylidenefluoride (PVDF) film of a size of 2 cm × 0.5 cm. The electrode wires are fixed with an electroconductive epoxy glue on both sides of the PVDF film surfaces and lead to the preamplifier filtering unit (bandpass of 0.1-1.0 c / s e c ) to detect nasal breathing. The transducer is located in front of the nose. The air flow of breathing causes little movement in the PVDF detector. The movement induces a voltage difference between the surfaces of the PVDF pad. This potential is passed through the filtering unit to the EEG recorder.
Electroencephalography and clinical Neurophysiology 95 (1995) 95P-97P
Society proceedings
The Finnish Society of Clinical Neurophysiology Tampere, 3 February 1995
Secretary:
Dr. T. Salmi
Di~'. of Clinical Neurophysiology, Dept. of Neurology, Uni~,er~i~ Hospital. Helsinki 00290, Finland Received for publication: 29 March 1995
1. Changes in ECG T-wave amplitude during anaesthesia. - P. Annila (Tampere University Hospital, Tampere) Changes in the ECG T-wave amplitude during anaesthesia with different anaesthetic agents were studied in 75 patients and 10 vohmteers to ascertain whether T-wave amplitude changes have clinical significance in anaesthesia practice. ECG lead CB5 (central back lead) was monitored on-line during the anaesthesia studies and recorded on tape for later quantitative analysis. Laryngoscopy and intubation produced T-wave flattening together with sympathoadrenal response in both inhalation and intravenous anaesthesia. T-wave flattening correlated with heart rate increase. After skin incision the T-wave decreased in moderate deep 1 MAC (ET 1.15%) isoflurane anaesthesia but during light (ET 0.7%) isoflurane anaesthesia it either increased or decreased. Circulating plasma catecholamine levels did not correlate to T-wave changes after skin incision and plasma potassium levels did not change despite marked T-wave alterations. T-wave changes were very rapid, occurring within seconds. Atropine 20 m g / k g was found to produce total parasympathetic block in volunteers, abolishing respiratory sinus arrhythmia almost completely. T-wave flattened at deep burst suppression anaesthesia level after atropine. It was concluded that during parasympathetic block sympathetic tone takes over, flattening the T-wave amplitude. The T-wave may therefore reflect the balance of the entire autonomic nervous system, not only increased sympathetic tone. Alfentanil 30 m g / k g given 5 min after skin incision produced T-wave flattening in correlation to a decrease in diastolic arterial pressure. During laryngoscopy and intubation alfentanil prevented the sympathoadrenal response, and neither T-wave flattening nor cardiac arrhythmias were seen. T-wave changes can be easily followed by eye in ECG monitoring during anaesthesia. T-wave flattening may reveal excessive sympathoadrenal tone and predict arrhythmias, but also an excessive decrease in arterial pressure can be suspected from T-wave flattening.
2. The effect of nitrous oxide on EEG and median nerve somatosensory evoked potentials during isoflurane anaesthesia. - T. Porkkala (Dept. of Anaesthesiology, Tampere University Hospital, Tampere) Recent studies show that nitrous oxide activates EEG when combined to isofiurane in burst suppression level of anaesthesia. Somatosensory evoked potentials (SEPs) show a substantial decrease in cortical N20 amplitude, when nitrous oxide is combined with isoflurane. Earlier we have shown that N20 is recordable during isoflurane-induced suppression.
We studied 13 patients scheduled for orthopaedical and abdominal surgery, they were anaesthetised with isoflurane until burst suppression. Simultaneous EEG and SEP were obtained during randomly selected periods of isoflurane-air-oxygen and isoflurane-nitrous oxide-oxygen anaesthesia. Nitrous oxide caused a marked ( P < 0.05) decrease in proportion of EEG suppression by 21%. At the same time the amplitude of the N20 component decreased, and only in 5 out of 13 patients the N20 could be obtained reliably. The different effects of nitrous oxide on EEG and SEP shown in this study are interesting. The effect of nitrous oxide on brain-stem reticular centres has been proposed as a mechanism of activation of the EEG in earlier reports. These participate in the generation of SEP but other levels are involved as well and the decrease in SEP may be due to the effect of isoflurane and nitrous oxide at thalamic or cortical level.
3. Visual evoked potential mapping in propofol anaesthesia. - K. M~ikel~i, H. Heikkilii and K. Kailiovalkama (Dept. of Clinical Neurophysiology and Anaesthesia, Seiniijoki Central Hospital, Sein~ijoki) We have recorded the EEG of 8 patients during propofol anaesthesia with a 21-channel digital brain mapping system. The anaesthesia level was deepened to burst suppression stage, during which the patients underwent visual stimulation with a standard discharge-tube flash stimulator. The VEP response was obtained off-line by summation techniques after the termination of the recording. The VEP response obtained during burst activity was of a longer latency (P100 mean 150 msec) than during the awake state. No VEP responses were seen during the suppression stage. Preliminary results do not indicate significant differences in VEP topography between the awake and burst suppression stages for the VEP response. During anaesthesia, however, a very short latency (40-75 msec) response is occasionally evident. The nature of this short latency response is unclear but could be due to suppression of thalamic inhibitory mechanisms.
4. Reactivity of propofol and isoflurane induced EEG burst suppression pattern. - K. Hartikainen, M. Rorarius, G. Baer and V. Jiintti (Dept. of Clinical Neurophysiology, Tampere University Hospital, Tampere) In moderate and deep anaesthesia the EEG shows burst suppression pattern and high voltage activity alternating with suppressed background activity. We compared propofol and isoflurane induced burst suppression and its reactivity to visual and painful stimulL We anaesthetised 12
0013-4694/95/$09.50 © 1995 Elsevier Science Ireland Ltd. All rights reserved
SSDI 0 0 1 3 - 4 6 9 4 ( 9 5 ) 0 0 0 7 3 - 9
EEG 95549
96P
Society Proceedings/Electroencephalography
patients with continuous propofol infusion and another 12 patients with isoflurane until burst suppression occurred in the EEG. The EEG was recorded for 0.5 h before the operation. The patients were given visual stimulation with flashes of red LED goggles or painful electric stimulation on the median nerve, both consisting of trains of 3 sec at a frequency of 20 Hz. Propofol induced burst suppression is characterised by lower amplitude and slower DC shifts at burst onset than isoflurane induced bursts. During propofol burst suppressions 13 Hz spindles, maximal in the frontocentral region, are seen both during bursts and suppressions, and during suppressions they are on the negative side of the positive suppression level. Both the onset and end of trains of visual and painful stimuli frequently evoked bursts in isoflurane induced burst suppression. In most patients there was no correlation between visual or painful stimulus and the occurrence of bursts in propofol induced burst suppression. The different EEG patterns and different reactivity in isoflurane and propofol induced burst suppression suggest different mechanisms of action, probably at the thalamic or cortical level.
5. Auditory event-related waveform to semantic congruency in children. - K. Juottonen, A. Revonsuo and H. Lang (Centre for Cognitive Neuroscience, University of Turku, Turku) Sixteen healthy children, 6 boys and 10 girls, ranging in age from 5.6 to 11.9 years, were presented with 160 naturally connected speech sentences as stimuli. 50% of the sentences ended with a semantically incongruous but syntactically correct word. The congruous and incongruous sentences appeared in random order. ERPs to both types of terminal words were separately averaged and analysed by ANOVA for repeated measures. The statistical analyses for the time windows of 400-600, 600-800, 800-1000, 1000-1200 and 1200-1700 msec revealed a significantly larger negative component to incongruous words than to congruous words, widely over the cortex in the time window of 400-1000 msec. The ERP waveform in children, probably related to the N400 in adults, displayed a right hemisphere predominance of long duration. The distinct long-duration N400-1ike wave elicited by semantic violation with naturally connected speech proves the acquisition and semantic organization of concepts in long-term memory in children.
6. The rationale of measuring the mismatch negativity (MMN) variables. - H. Mikola, H. Lang, T. Kiirki, S. Salo and P. Korpilahti (Dept. of Clinical Neurophysioiogy, University of Turku, Turku) There are no widely accepted rules to analyse the MMN variables. We used the Origin TM (Microcal Inc.) software with user defined macros to analyse amplitude, latency, duration and area variables. The variables were measured semi-automatically from the averaged individual MMN responses evoked with different auditive stimuli. In defining the MMN response we had two simple rules: the onset latency had to be over 45 msec and the peak latency between 100 and 200 msec. A total of 18 variables (e.g. peak, mean and half-area amplitude, onset, peak, offset and half-area latencies, rise time, total duration) based on either a straight baseline (from onset point) or a trend-fixed baseline (from onset to offset point) were calculated. Baseline corrected area and baseline corrected mean amplitude had the lowest variability between different test subjects (n = 140, 20-60 years). The correlation between experienced scorers varied from 0.56 (offset latency) to 0.97 (mean amplitude). To estimate the sensitivity of different variables we compared how the variables or the ratios of variables reflected the physical or physiological parameters: the characteristics of the stimulus, i.e., sound pressure or pitch difference, the maturity of the brain or the effect of ageing. The validity of the variables was tested by analysing whether they distinguished normal from dysphasic children. The methods described will contribute to rationalise and improve the signal analysis of MMN responses.
and clinical Neurophysiology 95 (1995) 95P-97P 7. Is there a late-latency mismatch negativity (MMN) component? P. Korpilahti, H. Lang and O. Aaltonen (Centre for Cognitive Neuroscience, University of Turku, Turku) We have registered a late-latency waveform following the MMN when using complex auditory stimuli. The waveforms were analysed in 2 age groups: adults (n = 13, age 21-32 years, stimulus pair consisted of prototypical and non-prototypical vowels i and y), and children (n = 15, age 5 - 1 0 years, stimulus pair consisted either of sine wave tones or words). In adults, the non-prototypical vowels especially elicited both an early negativity (the MMN) as well as a slightly smaller later negativity (latency about 400 msec) that were approximately the same in distribution (maximum at electrodes Fz or Cz). In children, the sine wave stimuli elicited only an early negativity ( - 1 3 + 9.4 /xV), whereas the verbal stimuli elicited an additional later ( - 21.1 + 10.9/zV) frontocentral negativity that was larger in amplitude, but of the same latency, in pre-school than in older children (mean 432 _+ 33 msec). The amplitudes of early and later negative wave forms are significantly correlated in the word paradigm (r = 0.685, P = 0.014). It is apparent that the later waveform reflects the automatic processing of complex auditory, possibly even linguistic, stimuli.
8. ERPs in impulsive violent offenders. - J. Karhu, J. Partanen, J. Tiihonen, J. Kuikka, A. PiiiikkOnen, K. Bergstrrm and P. Hakola (Dept. of Clinical Neurophysiology, University of Kuopio, Kuopio) We investigated habituation of N100, MMN and auditory P300 in violent offenders. Event-related potentials (ERPs) were compared with central serotoninergic and dopaminergic functions studied by /3-CIT SPECT. We studied 10 subjects (males; mean age 28 years; range 19-43 years) who had committed previous impulsive violent offences and were subjected to forensic psychiatric examination, and age-matched control subjects. For 21-channel auditory ERPs, 800 Hz tone pips were delivered in stimulus trains with a 12 sec intertrain interval. Each train consisted of 4 tones with an interstimulus interval of 1 sec. In auditory "oddball" paradigm 85% of standard 800 Hz and 15% of deviant 560 Hz tones were delivered in non-attended and attended conditions. The habituation of N100, MMN and P300 parameters were measured. An ~z31-1abelled cocaine congener, [123I]fl-CIT, was used for initial SPECT imaging of summed serotonin and dopamine re-uptake, subsequently separated by treatment with citalopram. Habituation of auditory N100 was significantly impaired in violent offenders and correlated positively (proportion of explained variance 60%) with a profound decrease in medial prefrontal cortex serotonin transporter visible in SPECT. The results suggest that frontal lobe serotonin system modulates automatic sensory responsiveness, which is impaired in violent offenders.
9. Recording of nasal breathing using the piezoelectric transducer. J. Siivola (Dept. of Clinical Neurophysiology, Kainuu Central Hospital, Kajaani) Recording of respiration is one of the most important physiological parameters in polysomnography. In this study a new method for recording of nasal breathing is presented. The detector for recording consists of a pad of polyvinylidenefluoride (PVDF) film of a size of 2 cm × 0.5 cm. The electrode wires are fixed with an electroconductive epoxy glue on both sides of the PVDF film surfaces and lead to the preamplifier filtering unit (bandpass of 0.1-1.0 c / s e c ) to detect nasal breathing. The transducer is located in front of the nose. The air flow of breathing causes little movement in the PVDF detector. The movement induces a voltage difference between the surfaces of the PVDF pad. This potential is passed through the filtering unit to the EEG recorder.