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

3. 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

4. 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

5. 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

6. 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 MAC 1-4 Hz MAC BURST SUPPRESSION
SPIKE WAVE EEG (ENFLURANE)
ISOLECTRIC EEG

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

8. 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.

9. 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

10. EVOKED POTENTIALS SSEP/SEP ABR/BAEP VEP MEP

11. 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

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

15. Auditory Brainstem Response

16. 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

17. 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

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

19. INTRAOPERATIVE MEP & EMG INCLUDING CRANIAL NERVE MONITORING

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

23. 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

24. Facial Nerve Monitoring
Bursts msec
Neurotonic sec

25. 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

26. Which Nerves? Cervical Thoracic Lumbosacral Sacral
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

27. Stimulator

28. ANESTHETIC REGIMEN FOR INTRAOPERATIVE NEUROPHYSIOLOGICAL MONITORING

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

30. 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

31. Sufentanil Fentanyl
MEP
SSEP

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

33. Anesthesia Components: Analgesia and Sedation/Amnesia
Barbiturates (thiopental, methohexitol)
Benzodiazepines (midazolam)
Propofol
Etomidate
Droperidol
[Ketamine]
[Dexmeditomidine

34. Propofol is the most common TIVA sedative

35. 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

36. 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 mg/kg/min
Sufentanil 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

37. 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”

38. THANK YOU FOR LISTENING
QUESTIONS?