INTRAOPERATIVE INTRAOPERATIVE NEUROPHYSIOLOGY AND NEUROPHYSIOLOGY AND

NEUROMONITORINGNEUROMONITORINGRamsis F. Ghaly, MD, FACS

and

Todd Sloan MD MBA PhDTodd Sloan MD MBA PhDUniversity of Colorado Health Science CenterUniversity of Colorado Health Science Center

EEG MONITORING UNDER EEG MONITORING UNDER ANESTHESIAANESTHESIA

VISUAL DIAGRAM (COMPRESSED SPECTRAL ARRAY)

ANALYSE (SPECTRA) COMPRESS AND SPPRESS SMOOTH (Delta Theta Alpha Beta in a diagram Time against Hz)

NUMERICAL VALUES BIS

Bispectral IndexBispectral IndexSet 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

BISPECTRAL INDEX (BIS)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

ANESTHETIC EFFECTS ON ANESTHETIC EFFECTS ON EEGEEG

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

ANESTHETICS PRODUCING ANESTHETICS PRODUCING BURST SUPPRESSIONBURST SUPPRESSION

BARBITURATEETOMIDATEISOFLURANE (2-2.5MAC)SEVOFLURANEDESFLURANE

INTRAOPERATIVE EEG INTRAOPERATIVE EEG MONITORINGMONITORING

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.

FACTORS AFFECTING EEGFACTORS AFFECTING EEG

HYPOXIA HYPOTENSION, ISCHEMIA (e.g.CEA) HYPOTHERMIA HYPO-AND HYPER-CARBIA BRAIN DEATH SURGERY:UNTOWARD EVENTS

CEA- CARDIOPULMONARY BYPASS-

CEREBRAL ANEURYSM CLIPPING

EVOKED POTENTIALS EVOKED POTENTIALS SSEP/SEPSSEP/SEP ABR/BAEP ABR/BAEP

VEP VEPMEPMEP

EVOKED POTENTIALEVOKED 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

Posterior Tibial N. SSEP

stimulus

Primary Sensory Cortex

Med. Lemniscus

Cervico-Medullary Junction

Spinal Cord

Auditory Brainstem Response

VISUAL EVOKED VISUAL EVOKED POTENTIALS (VEPS)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

ANESTHETIC EFFECTS ON ANESTHETIC EFFECTS ON EPSEPS

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

FACTORS AFFECTING EPS FACTORS AFFECTING EPS RECORDING UNDER ANESTHESIARECORDING UNDER ANESTHESIA

HYPOTHERMIAHYPOXIAHYPOTENSION/ISCHEMIAANESTHETIC AGENTSSURGICAL FACTORS: INJURY-

COMPRESSION- RETRACTION

INTRAOPERATIVE MEP & INTRAOPERATIVE MEP & EMG INCLUDING CRANIAL EMG INCLUDING CRANIAL

NERVE MONITORINGNERVE MONITORING

ElectroMyoGraphy

SSEP cannot evaluate individual nerve roots

•Operative Monitoring

–Nerve irritation

–Nerve identification (stimulation)

–Pedicle screw testing

–Reflex testing

–(Motor evoked potentials)

Methods for Cranial Nerve MonitoringMethods for Cranial Nerve Monitoring

II Optic sensory: VEPIII Oculomotor motor:inferior rectus mIV Trochlear motor: superior oblique mV Trigeminal motor: masseter and/or

temporalis mVI Abducens motor: lateral rectus mVII Facial motor: obicularis oculi and/or

obicularis oris mVIII Auditory sensory: ABRIX Glossopharyngeal motor: posterior soft palate

(stylopharygeus m)X Vagus motor: vocal folds, cricothyroid mXI Spinal Accessory motor: sternocleidomastoid m

and/or trapezious mXII Hypoglossal motor: tongue, genioglossus m

Facial Nerve Monitoring

Bursts 100 msec

Neurotonic 30 sec

Muscle relaxation is usually avoided in

monitoring spontaneous EMG (amplitude dec.)

cn 3,4,6

cn 10

cn 9,12

cn 9,10,11,12

Which Nerves?Which Nerves?

CervicalC2, C3, C4 Trapezius, Sternocleidomastoid

Spinal portion of the spinal accessory n.C5, C6 Biceps, DeltoidC6, C7 Flexor Carpi RadialisC8, T1 Abductor Pollicis Brevis, Abductor

Digiti MinimiThoracic

T5, T6 Upper Rectus AbdominisT7, T8 Middle Rectus AbdominisT9, T10, T11 Lower Rectus AbdominisT12 Inferior Rectus Abdominis

LumbosacralL2, L3, L4 Vastus MedialisL4, L5, S1 Tibialis AnteriorL5, S1 Peroneus longus

SacralS1, S2 GastrocnemiusS2, S3, S4 External anal sphincter

Stimulator

ANESTHETIC REGIMEN ANESTHETIC REGIMEN FOR INTRAOPERATIVE FOR INTRAOPERATIVE

NEUROPHYSIOLOGICAL NEUROPHYSIOLOGICAL MONITORINGMONITORING

Opioids

•Morphine

•Demerol

•Fentanyl

•Alfentanil

•Sufentanil

•Remifentanil

Ketamine

Dexmeditomidine

Anesthesia Components: Analgesia and Sedation/Amnesia

Excellent drug, blocks pain in pathways not used by IONM such that sedative

drugs that do hamper IOM can be kept at lower level

Fentanyl

Sufentanil Fentanyl

MEP

SSEP

KetamineKetamine

Perspective: Provides amnesia and analgesia Inexpensive as infusion in TIVA Problem of hallucinations Increases ICP with

intracranial pathology May inc seizures

Anesthesia Components:Anesthesia Components:Analgesia andAnalgesia and

Sedation/AmnesiaSedation/AmnesiaBarbiturates (thiopental, methohexitol)Benzodiazepines (midazolam) Propofol Etomidate• Droperidol• [Ketamine]• [Dexmeditomidine

Propofol is the most common TIVA sedative

Muscle RelaxationMuscle 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

Motor Evoked Responses: Start Motor Evoked Responses: Start with TIVAwith TIVA

 - Induction with appropriate medications (limit barbiturates and benzodiazepines) Using short to intermediate acting relaxantsPropofol 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

Summary: Effective AnesthesiaSummary: 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 responsesLiberalize or improve anesthesia Hold the physiology and anesthesia steadyDevelop an anesthesia

“protocol”

THANK YOU FOR THANK YOU FOR LISTENINGLISTENING

QUESTIONS?