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INTRAOPERATIVE NEUROPHYSIOLOGY AND NEUROMONITORING

INTRAOPERATIVE NEUROPHYSIOLOGY AND NEUROMONITORING. Ramsis F. Ghaly, MD, FACS and Todd Sloan MD MBA PhD University of Colorado Health Science Center. EEG MONITORING UNDER ANESTHESIA. VISUAL DIAGRAM (COMPRESSED SPECTRAL ARRAY) ANALYSE (SPECTRA) COMPRESS AND SPPRESS SMOOTH

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INTRAOPERATIVE NEUROPHYSIOLOGY AND NEUROMONITORING

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  1. INTRAOPERATIVE NEUROPHYSIOLOGY AND NEUROMONITORING Ramsis F. Ghaly, MD, FACS and Todd Sloan MD MBA PhD University of Colorado Health Science Center

  2. EEG MONITORING UNDER ANESTHESIA VISUAL DIAGRAM (COMPRESSED SPECTRAL ARRAY) ANALYSE (SPECTRA) COMPRESS AND SPPRESS SMOOTH (Delta Theta Alpha Beta in a diagram Time against Hz) NUMERICAL VALUES BIS

  3. Bispectral Index • Set of features on EEG(bispectrum, etal) combined and correlated with regression to clinical exam. • Bispectrum: A measure of the level of phase coupling in a signal, as well as the power in the signal

  4. BISPECTRAL INDEX (BIS) DIGITALIZE RAW SURFACE EEG (15-30SEC) AND PROCESS FREQUENCY AND AMPLITUDE AND CORRELATE TO DEPTH OF ANESTHESIA 70-75% RECALL OF WORDS OR PICTURES DEPRESSED <70% EXPLICIT RECALL SIGNIFICANTLY DEPRESSED 60-40% GENERAL ANESTHESIA 40-60% TARGET IF OPIODS USED AND 35% IF NO OPIODS TIVA, HEMODYNAMIC INSTABILITY TO REDUSE ANESTHETIC DOSAGES, SPEED RECOVERY, CLOSED-LOOP ANESTHESIA INTERFERENCE FROM EXTERNAL, MECHANICAL AND MUSCLE ACTIVITY SEIZURE SPIKE ERRONEOUS VALUES HYPNOTIC AGENTS MAY NOT HAVE LINEAR RELATIONSHIP e.g. N20, KETAMINE, OPIODS, ETOMIDATE

  5. ANESTHETIC EFFECTS ON EEG DRUG TYPE- DOSE-RELATED (DEPTH OF ANESTHESIA) AMPILTUDE-FREQUENCY-PATTERN- HEMISPHERIC SYMMETRY INTRAVENOUS AGENTS FAST ACTIVITY- SLOW & HIGH VOLTAGE EPILEPTIFORM ACTIVITY (KETAMINE-METHOHEXITAL) INHALATIONAL AGENT (FAST-LOW) SUB-MAC: FAST ACTIVITY (15-30Hz) 1 MAC 4-8 Hz - 1.5 MAC 1-4 Hz - 2-2.5MAC BURST SUPPRESSION SPIKE WAVE EEG (ENFLURANE) ISOLECTRIC EEG

  6. ANESTHETICS PRODUCING BURST SUPPRESSION BARBITURATE ETOMIDATE ISOFLURANE (2-2.5MAC) SEVOFLURANE DESFLURANE

  7. INTRAOPERATIVE EEG MONITORING BISPECTRAL ANALYSIS (BIS) BIS guided anesthesia demonstrated superiority in monitoring depth of anesthesia, minimize awareness under anesthesia, reduction in anesthetic utilization, guide delivery, fast awakening. Spectral Entropy, a measure of disorder in EEG activity, is being evaluated.

  8. FACTORS AFFECTING EEG HYPOXIA HYPOTENSION, ISCHEMIA (e.g.CEA) HYPOTHERMIA HYPO-AND HYPER-CARBIA BRAIN DEATH SURGERY:UNTOWARD EVENTS CEA- CARDIOPULMONARY BYPASS- CEREBRAL ANEURYSM CLIPPING

  9. EVOKED POTENTIALS SSEP/SEP ABR/BAEP VEPMEP

  10. EVOKED POTENTIAL EVOKED STIMULUS (AUDITORY ABR/BAER-VISUAL VEP-SOMATOSENSORY MN/ULNAR/PTN/CUTANEOUS SSEP) EEG IS SPONTANEOUS TRAVELLING PATHWAY RESPONSE (CORTICAL- SUBCORTICAL-SPINAL) (NEAR FIELD LATE LATENCY ABR/SEP- FAR-FIELD BAER/SSEP SHORT LATENCY) EP CHALLANGES MINUTE POTENTIALS IN MICROVOLTS COMPARED TO EEG IN MV ELECTRICAL ARTIFACTS LENGTHY AND MULTIPLE SYNAPTIC TRACTS AND VULNERABILITY TO ANESTHETICS AND EXTERNAL FACTORS TECHNIQUE FOR REPRODUCIBILITY AVERAGING AMPLIFIER

  11. Posterior Tibial N. SSEP Primary Sensory Cortex Med. Lemniscus Cervico-Medullary Junction Spinal Cord stimulus

  12. Auditory Brainstem Response

  13. VISUAL EVOKED POTENTIALS (VEPS) EYE GOGGLES AND OCCIPITAL ELECTRODES RETINA-OPTIC NERVE-OPTIC- MED. GENICULATE-OCCIPITAL CORTEX (VP 100) PITUITARY, SELLAR AND SUPRASELLAR SURGERIES VARIABLE AND VULNERABLE UNDER ANESTHESIA

  14. ANESTHETIC EFFECTS ON EPS LATENCY DELAY AMPLITUDE REDUCTION (EXCEPT ETOMIDATE AND KETAMINE) VARIABLE AMONG AGENTS WORSE IN INHALATIONAL AGENTS AND DOSE DEPENDANT ADDITIVE EFFECTS OF AGENTS VEP>SEP>BAER

  15. FACTORS AFFECTING EPS RECORDING UNDER ANESTHESIA HYPOTHERMIA HYPOXIA HYPOTENSION/ISCHEMIA ANESTHETIC AGENTS SURGICAL FACTORS: INJURY-COMPRESSION- RETRACTION

  16. INTRAOPERATIVE MEP & EMG INCLUDING CRANIAL NERVE MONITORING

  17. ElectroMyoGraphy SSEP cannot evaluate individual nerve roots • Operative Monitoring • Nerve irritation • Nerve identification (stimulation) • Pedicle screw testing • Reflex testing • (Motor evoked potentials)

  18. Methods for Cranial Nerve Monitoring II Optic sensory: VEP III Oculomotor motor:inferior rectus m IV Trochlear motor: superior oblique m V Trigeminal motor: masseter and/or temporalis m VI Abducens motor:lateral rectus m VII Facial motor: obicularis oculi and/or obicularis oris m VIII Auditory sensory: ABR IX Glossopharyngeal motor: posterior soft palate (stylopharygeus m) X Vagus motor: vocal folds, cricothyroid m XI Spinal Accessory motor: sternocleidomastoid m and/or trapezious m XII Hypoglossal motor: tongue, genioglossus m

  19. Facial Nerve Monitoring Bursts 100 msec Neurotonic 30 sec

  20. Muscle relaxation is usually avoided in monitoring spontaneous EMG (amplitude dec.) cn 9,10,11,12 cn 10 cn 9,12 cn 3,4,6

  21. Which Nerves? Cervical C2, C3, C4 Trapezius, Sternocleidomastoid Spinal portion of the spinal accessory n. C5, C6 Biceps, Deltoid C6, C7 Flexor Carpi Radialis C8, T1 Abductor Pollicis Brevis, Abductor Digiti Minimi Thoracic T5, T6 Upper Rectus Abdominis T7, T8 Middle Rectus Abdominis T9, T10, T11 Lower Rectus Abdominis T12 Inferior Rectus Abdominis Lumbosacral L2, L3, L4 Vastus Medialis L4, L5, S1 Tibialis Anterior L5, S1 Peroneus longus Sacral S1, S2 Gastrocnemius S2, S3, S4 External anal sphincter

  22. Stimulator

  23. ANESTHETIC REGIMEN FOR INTRAOPERATIVE NEUROPHYSIOLOGICAL MONITORING

  24. Anesthesia Components: Analgesia and Sedation/Amnesia • Opioids • Morphine • Demerol • Fentanyl • Alfentanil • Sufentanil • Remifentanil Ketamine Dexmeditomidine

  25. Fentanyl Excellent drug, blocks pain in pathways not used by IONM such that sedative drugs that do hamper IOM can be kept at lower level

  26. Sufentanil Fentanyl MEP SSEP

  27. Ketamine Perspective: • Provides amnesia and analgesia • Inexpensive as infusion in TIVA • Problem of hallucinations • Increases ICP with intracranial pathology • May inc seizures

  28. Anesthesia Components:Analgesia andSedation/Amnesia • Barbiturates (thiopental, methohexitol) • Benzodiazepines (midazolam) • Propofol • Etomidate • Droperidol • [Ketamine] • [Dexmeditomidine

  29. Propofol is the most common TIVA sedative

  30. Muscle Relaxation • Paralysis ok during intubation and some other times (e.g. back incision) • Full paralysis may be necessary to reduce EMG interference near recording electrodes ( e.g. SSEP cervical response, epidural or neural response) • Full or partial paralysis may reduce patient movement with stimulation • Partial paralysis may be acceptable for electrically stimulated pathways • Absence of paralysis may be necessary with mechanical stimulation or with pathology

  31. Motor Evoked Responses: Start with TIVA  - Induction with appropriate medications (limit barbiturates and benzodiazepines) Using short to intermediate acting relaxants Propofol 1-2 mg/kg Succinylcholine, vecuronium, rocuronium, etc. • Basic maintenance with TIVA Propofol 120-140 mg/kg/min Sufentanil 0.3-0.5 ug/kg/hr • Use EEG to guide propofol • No nitrous oxide, No potent inhalational • No muscle relaxation Desflurane 3% inhaled (1/2 MAC) may be tolerated in healthy patients

  32. Summary: Effective Anesthesia Work with monitoring to develop an anesthetic plan based on monitor techniques used Start the case with the best anesthesia possible and begin monitoring (use a bite block!) Review the responses Liberalize or improve anesthesia Hold the physiology and anesthesia steady Develop an anesthesia “protocol”

  33. THANK YOU FOR LISTENING QUESTIONS?

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