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?