Mod10: Anesthesia for Spinal Surgery

Question 1

Indications for Spinal Surgery

Answer 1

Spinal cord injury / trauma

Spinal column deformities

Scoliosis

^{secondary to Tumor, Vascular Malformation, Abscess, Hematoma}

Nerve root/cord compression

Degenerative vertebral column

HNP (Herniated Nucleus Pulposus (“Herniated disk”)

^{usuallay seen at L4-L5 or C5-C6}

Spondylosis/Stenosis

^{Affect s Lower cervical > lumbar}

Question 2

_{Spinal Surgery - Acute Spinal Cord Injury - Consider in all trauma}

Head trauma

^{consider what type of injury?}

Answer 2

Cervical spine injury (most common)

_{Prompt examination to assess function above level of injury critical}

Question 3

_{Spinal Surgery - Acute Spinal Cord Injury - Consider in all trauma}

Which spinal cord injury should considered with all trauma, until rulled out?

Answer 3

Thoracic spine injury

_{Prompt examination to assess function above level of injury critical}

Question 4

_{Spinal Surgery - Acute Spinal Cord Injury - Consider in all trauma}

Abdominal/long bone trauma

^{consider what type of injury?​}

Answer 4

Lumbar spine injury

_{Prompt examination to assess function above level of injury critical}

Question 5

_{Spinal Surgery - Trauma with suspected spinal cord injury}

Advanced Trauma Life Support (ATLS) protocol

^components:

Answer 5

In-line stabilization

Strip

Full exam

CT Scan STAT if needed

_{Prompt examination to assess function above level of injury critical}

Question 6

_{Spinal Surgery - Acute Spinal Cord Injury}

Oberved damage depends on:

Answer 6

Level of injury or trauma

Question 7

_{Spinal Surgery - Acute Spinal Cord Injury}

Diaphragmatic paralysis

^{how does is relate to the level of injury? most common cause of death:}

Answer 7

C3-C5 injuries

C5 = partial (C5 stays alive)

C4 = complete (C4 breathes no more)

Requires immediate ventilatory support

Respiratory failure most common cause death

Question 8

_{Spinal Surgery - Acute Spinal Cord Injury}

C6-C7 injuries

^{manifestations:}

Answer 8

↓ respiratory function (↓ VC 60%)

Inability to cough/clear secretions => infections/pneumonia

Question 9

_{Spinal Surgery - Acute Spinal Cord Injury}

Quadriplegia a/w transection above:

Answer 9

T1

Question 10

_{Spinal Surgery - Acute Spinal Cord Injury}

Paraplegia a/w transection above:

Answer 10

L4

Question 11

_{Spinal Surgery - Acute Spinal Cord Injury}

All trauma patients are considered to have unstable cervical spine injuries until proven otherwise

^{How is cervical spine injury r/o?}

Answer 11

Imaging studies (MRI, CT scan)

^{May not be practical in unstable patient}

Plain radiographs (AP & lateral)

^{Sensitivity is <100%}

_{Imaging the spine does not take precedence over life-saving diagnostic and therapeutic procedures}

Question 12

_{Spinal Surgery - Acute Spinal Cord Injury}

The cervical spine may be cleared clinically if the following preconditions are met:

Answer 12

• Fully alert and orientated
• No head injury
• No drugs or alcohol
• No neck pain
• No abnormal neurology
• No significant other ‘distracting’ injury (another injury which may ‘distract’ the patient from complaining about a possible spinal injury).

Provided these preconditions are met, the neck may then be examined.

If there is no bruising or deformity, no tenderness and a pain free range of active movements, the cervical spine can be cleared.

Radiographic studies of the cervical spine are not indicated.

If any of the followings present (bruising or deformity, tenderness and a painful or compromised range of active movements), a good radigraphic study (e.g. MRI, CT) would be needed to Clear the cervical spine.

Question 13

_{Acute Spinal Cord Injury - Cervical spine Not yet cleared}

Airway Management options:

Answer 13

AFOI

Blind nasal

Intubating LMA

Glidescope

DL with manual in-line stabilization

Question 14

_{Acute Spinal Cord Injury - Cervical spine Not yet cleared - Airway Mgt}

Considerations for AFOI:

Answer 14

Cooperative patient

Hemodynamically stable

Airway trauma doesn’t prevent visualization

General induced after voluntary movement of extremities confirmed

Question 15

_{Acute Spinal Cord Injury - Cervical spine Not yet cleared - Airway Mgt}

Consider Blind nasal - but contraindicated with:

Answer 15

Some facial fractures

(LeFort fractures)

Question 16

_{Acute Spinal Cord Injury - Cervical spine Not yet cleared - Airway Mgt}

DL with manual in-line stabilization

^{considerations:}

Answer 16

Truly emergent

Minimizes flexion/extension

Question 17

_{Spinal surgery - Acute Spinal Cord Injury}

Spinal Cord Shock

^{what is it?}

Answer 17

ACUTE spinal cord transection

Loss of spinal reflexes & flaccid paralysis below level of injury

Duration → 1-3 weeks

Question 18

_{Spinal surgery - Acute Spinal Cord Injury}

Manifestations of Spinal Cord Shock:

Answer 18

Hypotension

^{Loss of sympathetic tone below injury}

Bradycardia

^{If damage above <strong>T1-T4 </strong>where cardioaccelerator fibers are located - The body is unable to mount a sympathetic response and increase HR}

Loss of compensatory changes (e.g. tachycardia) with blood loss, position changes, or PPV

^{HR remains 40-60 bpm, even with hypotension because the body is unable to compensate for the lack of fluid}

Question 19

_{Spinal surgery - Acute Spinal Cord Injury}

Management of Spinal Cord Shock:

Answer 19

Prevent further damage

^{during movement, positioning, & airway management}

High dose corticosteroids

^{Methylprednisolone first 24 hr to reduce swelling around the cord}

^{Improves neurologic function, especially below the areas of damage}

Question 20

_{Spinal surgery - Acute Spinal Cord Injury}

Induction of anesthesia in Spinal Cord Shock:

Answer 20

IV fluid bolus

^{They might be hypotensive purely from trauma, coupled with hypotension and bradycardia from the spinal shock - Prevents CV collapse on induction}

Ketamine

^{This where we could use the benefice of ketamine}

Vasopressors may be required

^{To maintain adequate perfusion to the cord}

Succinylcholine

^{Safely used within first 24 hrs of injury}

^{Can see succinylcholine induced hyperkalemia later (after the 1st 24 hrs)}

Adequate spinal cord perfusion pressures

^{Adequate volume - Normal level BP - <strong>Avoid hyperventilation**</strong>}

^{(Hyperventilation => Hypocarbia => vasodilation => <strong>↓ spinal cord blood flow</strong>)}

Question 21

_{Spinal surgery - Induction of anesthesia in Spinal Cord Shock}

Succinylcholine-Induced Hyperkalemia:

Answer 21

Proliferation of acetylcholine receptors outside neuromuscular synaptic cleft

Occurs 24 hrs after SCI

^{Max: 4 wks - 5 mos - Decreases: after 6 mos (unless the pt remains bedbound)}

V-fib/cardiac arrest

^{Giving Sux after the 1st 24 hrs could results in a huge release of K+ with all the the associated negative effects of Hyperkalemia}

NDMR do not prevent

Safe to administer Sux for the first 24 hrs after acute injury

^{If unsured, do no give Sux!!! Use a different NMB agent}

Avoid succinylcholine in SCI patients 24 hrs after injury and up to 5 months

Question 22

_{Spinal surgery - Acute Spinal Cord Injury}

Autonomic Hyperreflexia

Answer 22

Return of spinal reflexes

Follows period of spinal shock

Anytime from 4 wks to many years after injury

Occurs in 85% with lesion T5 or T6 & above

Question 23

_{Spinal surgery - Acute Spinal Cord Injury -<strong> Autonomic Hyperreflexia</strong>}

Pathophysiology:

Answer 23

Inhibition of normal descending inhibitory impulses in cord

Sympathetic discharge below lesion reacts to noxious stimulus unopposed

Question 24

_{Spinal surgery - Acute Spinal Cord Injury - Autonomic Hyperreflexia}

Precipitating factors:

Answer 24

Distention of the bladder & rectum (most typical)

Any noxious/painful stimulus

Question 25

_{Spinal surgery - Acute Spinal Cord Injury - <strong>Autonomic Hyperreflexia</strong>}

Clinical manifestations:

Answer 25

Severe HTN with bradycardia

^{Cutaneous vasoconstriction below the cord}

Vasodilation above the cord (nasal stuffiness)

^{Baroreceptor reflex}

Headache

Subarachnoid hemorrhage

Seizures

Cardiac dysrhythmias

Acute left ventricular failure (Pulmonary Edema)

Question 26

_{Spinal surgery}

Feared complication of spine surgery:

Answer 26

Paralysis

Intraoperative compromise of spinal cord function must be detected as early as possible & reversed immediately

Question 27

_{Spinal surgery - Spinal Cord Monitoring}

Two methods used to detect intraoperative compromise of spinal cord function:

Answer 27

“Wake-up test”

^{Intraoperative awakening of patient after completion of instrumentation}

Neurophysiologic monitoring

^{Somatosensory Evoked Potentials (SSEP’s)}

^{Motor Evoked Potentials (MEP’s)}

_{Poor prognosis if pt wakes up w/ paralysis and hasn’t been monitored for spine integrity — if find intraop, can adjust / remove instrumentation and try to get at least “some” function back. Need to detect ASAP}

Question 28

_{Spinal surgery - Spinal Cord Monitoring}

Intraoperative awakening of patient after completion of instrumentation:

Answer 28

“Wake-Up Test”

Surgical anesthesia and muscle relaxation are reversed

^{Balanced technique typically used}

^{Opioids important → analgesia while awake}

Pt asked to move both hands first followed by both feet

^{Unsatisfactory movement feet → release distraction rod one notch → repeat test}

Surgical anesthesia is reestablished

Question 29

_{Spinal surgery - Spinal Cord Monitoring}

“Wake-Up Test”

^{pt’s position - feasbility & drugs used to facilitate test:}

Answer 29

Prone w/ ETT in place, wake up test is very difficult

Usually use Remi and Prop infusions with 0.3-0.4 MAC inh agents for SSEP, MEP.

Question 30

_{Spinal surgery - Spinal Cord Monitoring}

Propofol vs Precedex gtt for wake up test?

Answer 30

We use precedex a lot for MRI for stereotactic guided placement of deep brain stimulator electrodes for parkinson’s pt’s.

Precedex (dexmedetomidine) – 1mcg/kg loading dose over 10 mins, then 0.2 – 1 mcg/kg/HR (usually start at 0.6mcg/kg/hr and TTE)

Question 31

_{Spinal surgery - Spinal Cord Monitoring}

Post-op concern of “Wake-Up Test”:

Answer 31

Recall!!!

Occurs in 0-20% of patients

Fully inform pt preoperatively of possibility

Question 32

_{Spinal surgery - Spinal Cord Monitoring}

Complications a/w “Wake-Up Test”:

Answer 32

Pain

Air embolism

Dislocation of instrumentation

Accidental extubation

Question 33

_{Spinal surgery - Spinal Cord Monitoring}

Which test noninvasively assesses neural function by measuring electrophysiological responses to sensory of motor pathway stimulation:

Answer 33

Neurophysiological Monitoring via Evoked potentials

Question 34

_{Spinal surgery - Spinal Cord Monitoring}

Evoked potentials waveform analysis

^{what to look for and analyze:}

Answer 34

Latency

^{Time between stimulation and potential detection}

^{↑ latency → damage pending}

Amplitude

^{Height of peak}

^{↓ amplitude → damage pending}

Inc latency or dec amplitude means LESS responsiveness to stimulation

Ascending sensory and descending motor pathways

Question 35

_{Spinal surgery - Spinal Cord Monitoring - Neurophysiological Monitoring}

Two types of Evoked potentials:

Answer 35

SSEP’s

MEP’s

Question 36

_{Spinal Cord Monitoring - Neurophysiological Monitoring - Evoked potentials}

SSEP’s:

Answer 36

Reflect dorsal (Posterior) columns of spinal cord

Supplied by posterior spinal artery

Proprioception and vibration (Sensory)

NOT MOTOR

_{AMPS: Anterior = Motor; Posterior = Sensory}

Question 37

_{Spinal Cord Monitoring - Neurophysiological Monitoring - Evoked potentials}

MEP’s:

Answer 37

Reflect anterior columns of spinal cord

Supplied by anterior spinal artery

Motor pathways

Technically more difficult to use

Question 38

_{Neurophysiological Monitoring - Evoked potentials - Effects of anesthetic agents}

Volatile anesthetics:

Answer 38

↑ latency & ↓amplitude (MEP > SSEP) by themselves

^{May get false reading when you get up to 1.0 MAC}

^{Keep pt on 0.5 MAC with some other agents}

Recordable during low dose & obliterated with high doses

Combined with N20 further compromises quality of the signal => Avoid N20!!!

Inhalational agents have greater depressant effects than intravenous agents

Question 39

_{Neurophysiological Monitoring - Evoked potentials - Effects of anesthetic agents}

Opioids & Benzodiazepines

Answer 39

Negligible effect on Latency and amplitude of these signals

Question 40

_{Neurophysiological Monitoring - Evoked potentials - Effects of anesthetic agents}

Propofol:

Answer 40

Excellent signal quality

^{Great drug to use!!!}

Question 41

_{Neurophysiological Monitoring - Evoked potentials - Effects of anesthetic agents}

Ketamine & Etomidate

Answer 41

Enhance the quality of signals

^{But not used as often as far as TIVA goes}

Question 42

_{Neurophysiological Monitoring - Evoked potentials - Effects of anesthetic agents}

Anesthetic technique’s commonly used during Neurophysiological Monitoring??

Answer 42

Ultra short acting opioid infusion (Remi) + Propofol + low dose inhaled anesthetic (< 0.5 MAC) with BIS monitoring

_{Why BIS monitoring?}

_{Supplement Neuro monitoring since we are using less than 0.7 MAC.}

_{The goal is normally <strong>ETMAC = 0.7</strong> to prevent recall}

TIVA w_ithout muscle relaxants_ for MEP

Question 43

_{Neurophysiological Monitoring - Evoked potentials}

Performed by:

Answer 43

Technician in the room

Continually monitors SSEPs and occasionally MEPs

Change of 50% or > is significant

Changes around 20% can be r/t anesthesia or surgeon

Question 44

_{Neurophysiological Monitoring - Evoked potentials}

Factors that could cause changes 50% of > in SSEP:

Answer 44

Hypercarbia

Hypoxia - Hypotension

Hypothermia

Changes d/t to these factors happen slowly overtime

Question 45

_{Neurophysiological Monitoring - Evoked potentials}

ACUTE alterations in SSEP amplitude/latency

^{could indicate:}

Answer 45

Spinal cord compromise

^from:

Direct trauma - Ischemia - Compression - Hematoma

Question 46

_{Neurophysiological Monitoring - Evoked potentials}

ACUTE alterations in SSEP amplitude/latency

^Management:

Answer 46

Stop surgery

Return BP to normal or 20% above

Decrease or D/C volatile agents

Draw ABG to r/o metabolic abnormality (?)

Release distraction on cord

“Wake-up test” to exclude neurologic deficits