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O66 Automatic EEG monitoring and stroke detection during carotid endarterectomy
Communications orales/Oral communications
23s
063
064
INTRA-OPERATIVE SPINAL CORD MONITORING : PRESENTATION OF A TECHNIQUE THAT ALLOWS BILATERAL ASSESSMENT OF BOTH SOM~TOSENSORY (ASCENDING) AND MOTOR (DESCENDING) PATHWAYS.
HEART RATE VARIABILITY DURING ANAESTHESIA V.J~ntti, A.Yli-Hankala, T.Porkkala, and V.H~kkinen Department of Clinical Neurophysiology Tampere University Central Hospital, SF-33520 Tampere,Finland
Ph. Nogl, P.Deltenre, J.Lamourenx*, V.Capouet*, M.Govaerts*. HSpital Brugmann & HSpital Universitaire des Enfants Reine Fabiola* - Brussels (Belgium). The aim of the present work was to obtain a technique to monitor continuously the functional integrity of the motor and sensory pathways independently, and from both sides, during spinal surgery. A user-friendly, semi-automated interactive dedicated software driving a multiprocessor electrodiagnostic system (NICOLET Pathfinder) was developed. Surface EMG and scalp recordings were preferred to epidural electrodes in order to provide independent right and left motor testing and to allow the monitoring to be performed up to the awakening. Electrical transcranial cortical stimulation was performed bipolarly with a capacitive discharge of 1500 V. The somatosensory monitoring was achieved by Tibialis Posterior nerve stimulation. The present technique gradually evolved from the experience built on 12 consecutive cases of spinal fusion for idiopathic scoliosis. The major problem encountered was due to the profound depression that most anaesthetic agents exert on MEPS. The best anaesthetic regimen identified up to now in order to allow reliable motor and sensory recordings is an analgesic anaesthesia combining Flunitrazepam and Fentanyl. At the present stage of development, this method has demonstrated its ability to monitor the main four spinal tracts. A fresh sampling of the four tracts functional s t a t e c a n be obtained every 3-4 minutes. The great versatility offered by interactive software control allows, at any moment, temporary focussing on a peculiar monitoring channel that might require special attention. Switching to MEP monitoring alone during the critical derotation phase allows feed-back information on the functional status of the motor pathways to be passed to the surgeon in less than 60 seconds. The method offers provision for the implementation of additional recording sites (spinal, epidural, periphera$-herves..;) for Research and Development purposes.
We have studied the beat-to-beat variations in heart rate during enflurane and isoflurane anaesthesia. We developed new averaging methods to study the correlation of h e a r t r a t e a n d E E G b u r s t suppression pattern or tracheal pressure during positive pressure ventilation. During burst suppression pattern of EEG the heart rate accelerates at burst onsets and decelerates at suppression onsets. We hypothesize t h a t t h i s is d u e to synchronous inhibition of heart rate and EEG during suppressions. We suggest that these inhibitory mechanisms a r e at l e a s t p a r t i a l l y the same which inhibit and limit epileptic discharges. We compared the magnitude of r e s p i r a t o r y sinus arrythmia at 1 MAC level and at the level of burst suppression p a t t e r n in E E G . R e s p i r a t o r y sinus a r r y t h m i a w a s l o w e r in d e e p a n a e s t h e s i a than at 1 M A C l e v e l a n d l o w e r in l o w e r d u r i n g e n f l u r a n e than isoflurane anaesthesia. Interindividual variability, is , h o w e v e r , considerable. Positive pressure ventilation caused a deceleration of heart rate during inpirium and acceleration in expirium. T h i s is o p p o s i t e in p h a s e c o m p a r e d w i t h the respiratory sinus arrythmia due to active respiration awake. An exception was a patient who developed a short epileptic discharge in E E G b u r s t suppression stage. His heart rate accelerated during inspiration. This shows the importance of c e n t r a l n e r v o u s s y s t e m c o n t r o l of r e s p i r a t o r y sinus arrythmia in a n a e s t h e s i a .
066
065
AUTO~9%TIC EEG ~9NITOR/NG AND STROKE DETECTION DURING CAROTID ~DARTERECTOMY R.G.A. Ackeretaff, J.M.J. Krul, B.C. Eikelboom, F.E.E. Vermeulen. DepardGr~nt of ClInical Neurophysiology, St.Antc~iasHospital, Nieuwegain (Utrecht), The Netherlands.
TOPOGRAPHIC BRAIN MAPPING DURING CAROTID ENDARTERECTOMY Mattelli L, Feleppa M, ° Gallai V, Cao PG*, Moggi L.* Cliffica ~ehlrologica, Perugia, Italy. °Divisione Neurologia POM, USL 05, Benevento, Italy. *Clinica Chirurgica, Perugia, Italy. A stenosed or ulcerated atheromatic plaque in the extracranial portion of the CA, which is hemodinamically significatire, can induce embolization and/or occlusion within the cerebral circulation. Carotid endarterectomy is a surgical procedure capable of reducing the incidence of such phenomena. The intraoperatory EEG-Maps can reveal minimal dysfunctions in cerebral bioelectric activity. We studied 21 pt who received carotid angiography, routine laboratory analysis, EEG and Neurological Examination. In this study we used a Brain Mapping (Neumoscience Inc., Ca. USA) equipped with 28 recording electrodes. The Neurophysiological study was based on baseline phase, anesthesia, induction and manteinance, pre-clamping, clamping, declamping, awakening and control phases. Our data are relative only to the time interval successive to clamping. Results show a decrease in amplitude in either single band frequencies or in all of them and an increase in amplitude and duration of delta and theta activity. In this study non significative COrrelatidn was found between stump pressure and changes in the CEA. These changes may be due to reduction in thehhem±spheric and/or regional bloodflow, microembolization and Varying concentrations of anesthesia, all of them leading to edema and subsequent reduction of oxygen availability to the neuron. In one case the EEG-Maps did demonstrate an acute impairment of the left hemisphere during declamping, showing, in real time, the insorgence and evolution of an acute vascular phenomenon, so demostrating the effectiveness of this method.
EEG recordings from 230 carotid endarterectomiesperformed with an automatic EEG monitoring system were reviewed with the purpose of establishing the specificity and sensitivity of this system in the identificationof intraoperatieve stroke. The monitoring system was based on procedures of artificial intelligenceand included an expert system which also calculated the effects of changing depth of anaesthesia, blood pressure, and arterial clamping. Patients were only operated for haemodynamically significant lesions and selectively shunted based on EEG changes during cross cl8~ping. Attention was paid to the degree of EEG asymmetry during surgery. A shLmt was used in 35 andarterectomies (15.2 %). Stroke resulting in disability interferingwith daily activities was regarded as major. Five major and 6 minor strokes were noticed in~ediately after surgery (4.8 %). All minor strokes were transient. Only persistant }~G asymmetry reflected iniraoperative stroke, expressedby a specificity of 0.99, a sensitivity of 0.80, and a diagnostic gain of 47.8 % of the EG. Transient EEG asymmetry was not associated with intraoperative stroke. Minor strokes could not be detected with the EEG monitoring system. Most of the false negative EEG's correspondedwith minor strokes caused by lactrmr, subcortical or small cortical infarcts. This explains why they can be missed by intraoperative EEG monitoring. In conclusion, this study clearly demonstrates that automatic EEG monitoring has several advantages. The first is the selection of proper patients in the need of shantthg. Secondly, it proved to have a good specificity and sensitivity regarding the detection of intraoperative stroke. This is also expressed by the diagnosticgain of 47.8 %, indicating that the EEG contributes with an additional 47.8 % to the diagnosis of intraoperative stroke. Therefore, it offers the possibility of taking apprepriats postoperative measures. Finally, it can be concluded that persisting EEG asymmetry developing during carotid endarterecto~y is directly related to intrasperative stroke while transient asynmetry proved to be of less significance. Analysis of the time course of the persisting asymmetry confirmed the thrombo-embolic origin of the majority of major strokes. To increase the reliability of the detection of intraoperativeminor strokes, transcramial Doppler monitoring will be incorporated in the expert system.
23s
063
064
INTRA-OPERATIVE SPINAL CORD MONITORING : PRESENTATION OF A TECHNIQUE THAT ALLOWS BILATERAL ASSESSMENT OF BOTH SOM~TOSENSORY (ASCENDING) AND MOTOR (DESCENDING) PATHWAYS.
HEART RATE VARIABILITY DURING ANAESTHESIA V.J~ntti, A.Yli-Hankala, T.Porkkala, and V.H~kkinen Department of Clinical Neurophysiology Tampere University Central Hospital, SF-33520 Tampere,Finland
Ph. Nogl, P.Deltenre, J.Lamourenx*, V.Capouet*, M.Govaerts*. HSpital Brugmann & HSpital Universitaire des Enfants Reine Fabiola* - Brussels (Belgium). The aim of the present work was to obtain a technique to monitor continuously the functional integrity of the motor and sensory pathways independently, and from both sides, during spinal surgery. A user-friendly, semi-automated interactive dedicated software driving a multiprocessor electrodiagnostic system (NICOLET Pathfinder) was developed. Surface EMG and scalp recordings were preferred to epidural electrodes in order to provide independent right and left motor testing and to allow the monitoring to be performed up to the awakening. Electrical transcranial cortical stimulation was performed bipolarly with a capacitive discharge of 1500 V. The somatosensory monitoring was achieved by Tibialis Posterior nerve stimulation. The present technique gradually evolved from the experience built on 12 consecutive cases of spinal fusion for idiopathic scoliosis. The major problem encountered was due to the profound depression that most anaesthetic agents exert on MEPS. The best anaesthetic regimen identified up to now in order to allow reliable motor and sensory recordings is an analgesic anaesthesia combining Flunitrazepam and Fentanyl. At the present stage of development, this method has demonstrated its ability to monitor the main four spinal tracts. A fresh sampling of the four tracts functional s t a t e c a n be obtained every 3-4 minutes. The great versatility offered by interactive software control allows, at any moment, temporary focussing on a peculiar monitoring channel that might require special attention. Switching to MEP monitoring alone during the critical derotation phase allows feed-back information on the functional status of the motor pathways to be passed to the surgeon in less than 60 seconds. The method offers provision for the implementation of additional recording sites (spinal, epidural, periphera$-herves..;) for Research and Development purposes.
We have studied the beat-to-beat variations in heart rate during enflurane and isoflurane anaesthesia. We developed new averaging methods to study the correlation of h e a r t r a t e a n d E E G b u r s t suppression pattern or tracheal pressure during positive pressure ventilation. During burst suppression pattern of EEG the heart rate accelerates at burst onsets and decelerates at suppression onsets. We hypothesize t h a t t h i s is d u e to synchronous inhibition of heart rate and EEG during suppressions. We suggest that these inhibitory mechanisms a r e at l e a s t p a r t i a l l y the same which inhibit and limit epileptic discharges. We compared the magnitude of r e s p i r a t o r y sinus arrythmia at 1 MAC level and at the level of burst suppression p a t t e r n in E E G . R e s p i r a t o r y sinus a r r y t h m i a w a s l o w e r in d e e p a n a e s t h e s i a than at 1 M A C l e v e l a n d l o w e r in l o w e r d u r i n g e n f l u r a n e than isoflurane anaesthesia. Interindividual variability, is , h o w e v e r , considerable. Positive pressure ventilation caused a deceleration of heart rate during inpirium and acceleration in expirium. T h i s is o p p o s i t e in p h a s e c o m p a r e d w i t h the respiratory sinus arrythmia due to active respiration awake. An exception was a patient who developed a short epileptic discharge in E E G b u r s t suppression stage. His heart rate accelerated during inspiration. This shows the importance of c e n t r a l n e r v o u s s y s t e m c o n t r o l of r e s p i r a t o r y sinus arrythmia in a n a e s t h e s i a .
066
065
AUTO~9%TIC EEG ~9NITOR/NG AND STROKE DETECTION DURING CAROTID ~DARTERECTOMY R.G.A. Ackeretaff, J.M.J. Krul, B.C. Eikelboom, F.E.E. Vermeulen. DepardGr~nt of ClInical Neurophysiology, St.Antc~iasHospital, Nieuwegain (Utrecht), The Netherlands.
TOPOGRAPHIC BRAIN MAPPING DURING CAROTID ENDARTERECTOMY Mattelli L, Feleppa M, ° Gallai V, Cao PG*, Moggi L.* Cliffica ~ehlrologica, Perugia, Italy. °Divisione Neurologia POM, USL 05, Benevento, Italy. *Clinica Chirurgica, Perugia, Italy. A stenosed or ulcerated atheromatic plaque in the extracranial portion of the CA, which is hemodinamically significatire, can induce embolization and/or occlusion within the cerebral circulation. Carotid endarterectomy is a surgical procedure capable of reducing the incidence of such phenomena. The intraoperatory EEG-Maps can reveal minimal dysfunctions in cerebral bioelectric activity. We studied 21 pt who received carotid angiography, routine laboratory analysis, EEG and Neurological Examination. In this study we used a Brain Mapping (Neumoscience Inc., Ca. USA) equipped with 28 recording electrodes. The Neurophysiological study was based on baseline phase, anesthesia, induction and manteinance, pre-clamping, clamping, declamping, awakening and control phases. Our data are relative only to the time interval successive to clamping. Results show a decrease in amplitude in either single band frequencies or in all of them and an increase in amplitude and duration of delta and theta activity. In this study non significative COrrelatidn was found between stump pressure and changes in the CEA. These changes may be due to reduction in thehhem±spheric and/or regional bloodflow, microembolization and Varying concentrations of anesthesia, all of them leading to edema and subsequent reduction of oxygen availability to the neuron. In one case the EEG-Maps did demonstrate an acute impairment of the left hemisphere during declamping, showing, in real time, the insorgence and evolution of an acute vascular phenomenon, so demostrating the effectiveness of this method.
EEG recordings from 230 carotid endarterectomiesperformed with an automatic EEG monitoring system were reviewed with the purpose of establishing the specificity and sensitivity of this system in the identificationof intraoperatieve stroke. The monitoring system was based on procedures of artificial intelligenceand included an expert system which also calculated the effects of changing depth of anaesthesia, blood pressure, and arterial clamping. Patients were only operated for haemodynamically significant lesions and selectively shunted based on EEG changes during cross cl8~ping. Attention was paid to the degree of EEG asymmetry during surgery. A shLmt was used in 35 andarterectomies (15.2 %). Stroke resulting in disability interferingwith daily activities was regarded as major. Five major and 6 minor strokes were noticed in~ediately after surgery (4.8 %). All minor strokes were transient. Only persistant }~G asymmetry reflected iniraoperative stroke, expressedby a specificity of 0.99, a sensitivity of 0.80, and a diagnostic gain of 47.8 % of the EG. Transient EEG asymmetry was not associated with intraoperative stroke. Minor strokes could not be detected with the EEG monitoring system. Most of the false negative EEG's correspondedwith minor strokes caused by lactrmr, subcortical or small cortical infarcts. This explains why they can be missed by intraoperative EEG monitoring. In conclusion, this study clearly demonstrates that automatic EEG monitoring has several advantages. The first is the selection of proper patients in the need of shantthg. Secondly, it proved to have a good specificity and sensitivity regarding the detection of intraoperative stroke. This is also expressed by the diagnosticgain of 47.8 %, indicating that the EEG contributes with an additional 47.8 % to the diagnosis of intraoperative stroke. Therefore, it offers the possibility of taking apprepriats postoperative measures. Finally, it can be concluded that persisting EEG asymmetry developing during carotid endarterecto~y is directly related to intrasperative stroke while transient asynmetry proved to be of less significance. Analysis of the time course of the persisting asymmetry confirmed the thrombo-embolic origin of the majority of major strokes. To increase the reliability of the detection of intraoperativeminor strokes, transcramial Doppler monitoring will be incorporated in the expert system.