Neuro Anesthesia Flashcards
What are the three types of neurosurgery?
intracranial
functional
spine
What are types of intracranial surgery?
craniotomy
interventional radiology
trauma
What are types of functional neurosurgery?
epilepsy
movement
pain
What are types of spine surgery?
anterior
posterior
transoral
When are Motor evoked potentials motored?
used in surgeries where motor tract is at risk
How are motor evoked potentials measured?
direct and scalp electrodes
What potentials are more sensitive to ischemia?
motor evoked potentials by 15minutes and degree detection
Why are motor evoked potentials difficult to obtain?
due to pre-existing conditions or anesthetic conditions
What are somato-sensory evoked potentials?
most commonly motored potentials
stimulation of peripheral sensory nerve
mapping in spinal cord and sensory cortex
Where does somato-sensory potentials measure ischemia?
cortical tissue
What does SSEPs reduce?
risk of spinal cord/brainstel
mechanical or ischemic insults
What is EMG?
records muscle electrical activity using needle pairs
continuous recording
triggered responses
What does EMG detect?
detects nerve irritation
nerve mapping
assess nerve function
monitoring of cranial nerves
When is EMG commonly used?
spinal surgery involving instrumentation
How is EMG advantagous?
helps prevent postoperative radiculopathy by identifying nerve irritation before injury
Who is not usually involved in EMG monitoring?
IONM
How is EMG triggered?
stimulation of pedicle screws or pilot holes can be used to identify malpositioned screws that are too close to nerve roots
What is the purpose of a SSEP?
electrical stimulation of peripheral nerves using needle electrodes, stimulates both motor and sensory components producing visible muscle twitching
How do SSEPs work?
sensory activation of the electrodes results in responses that travel along the sensory pathway to the brain, which are monitored at the sensory cortex via EEG electrodes
What are the anesthetic implications for SSEPs in patients without neurologic pathology?
adequate SSEPs can be recorded at 0.5MAC
What are the anesthetic implications for SSEPs in patients with neurologic pathology?
low levels of inhalation agents may abolish potentials and make monitoring impossible
What anesthetic drugs have minimial effects on SSEPs?
propofool
barbiturates
opioids
midazolam
ketamine
NMDAs
What needs to be stopped during a TOF assessment?
SSEP monitoring
What is the purpose of MEP?
monitor the integrity of motor pathways by transcranial motor cortex stimulation
What are anesthetic implications for MEPs?
anesthetic agents attenute motor evoked potentials in a dose-dependent manner
Therefore, the depth of anesthesia should be monitored objectively (BIS) and maintained constant
- affected my low concentrations of VA, TIVAs are preferred
What should propofol be titrated to on the BIS for MEPs?
BIS >50
What is stereotactic neurosurgery?
applies the rules of geometry to radiologic images to allow for precise localization within the brain, providing up to 1mm of accuracy
What is an advantage of stereotactic neurosurgery?
allows surgeons to perform certain intracranial procedures less invasively
How does sterotactic neurosurgery work?
radiologically, small markers (fudicicals) are affixed to the scalp and forehead with adhesive, important that these fudicials do not move between the time of imaging and entry to the OR
What type of anesthesia is used for stereotactic neurosurgery?
smaller biopsies may be done under local/MAC
GETA for larger resections
What are the types of intracranial mass leisons?
congenital
neoplastic (bengin vs. malignant)
vascular (hematoma vs arteroivenous malformation)
What is the typical presentation of an intracranial mass leison?
Headache
seizures
focal neurological deficits
sensory loss
cognitive dysfunction
What comprises supratentorial intracranial mass leisons?
frontal, parietal, temporal, occipital
What are symptoms of intracranial mass leisons in the supratentorial region?
seizures, hemiplegia, aphasia
What are symptoms of intracranial mass leisons in the frontal region?
personality changes, increased risk taking, difficulty speaking (damage to broca’s area)
What are symptoms of intracranial mass lesions in the parietal region?
sensory problems
What are symptoms of intracranial mass lesions in the temporal region?
problems with memory, speech, perception and language skills
What are symptoms of intracranial mass lesions in the occipital region?
difficulty recognizing objects, an inability to identify colors, and trouble recognizing words
What are symptoms of intracranial mass lesions in the infratentorial/posterior fossa region?
cerebellar dysfunction
brainstem compression
What are symptoms of intracranial mass lesions causing cerebellar dysfunction?
ataxia/ poor balance, nystagmus, dysarthria, cannot perform rapid alternating movements, loss of muscle cooridination
What are symptoms of intracranial mass lesions causing brainstem compression?
cranial nerve palsy, altered LOC, abnormal respiration
What are types of cells are primary tumors?
glial cells
ependymal cells
supporting tissues
Glial cells break into what types?
astrocytoma
oligodendroglioma
glioblastoma
What are cancerous ependymal cells?
ependymomas
What are cancerous supporting tissues?
meningioma
schwannoma
choroidal papilloma
What are the major considerations for intracranial mass leison management?
tumor location
growth rate and size
ICP elevated
What are the anesthetic goals for intracranial mass lesion management?
control ICP
maintain CPP
Protect from position-related injuries
rapid emergency for neuro assessment
What does tumor location imply?
determines position, EBL, risk for hemodynamic changes intraoperative
What does growth rate ad size of the mass imply?
slow growing tumors are often asymptomatic
What are pre-operative considerations for intracranial mass leisons?
determine presence or absence of increased ICP
document LOC and neuro deficits
review PMH and general health status
Review medication regimen (pay special attention to anticonvulsants, diuretics, steroids)
Review lab findings (glucose levels, anticonvulsant drug levels, electrolyte disturbances, H/H)
Review radiological studies (evidence of edema, midline shift, change in ventricular size)
Pre-medication (avoid benzodiazepines/narcotics in pt with increase ICP)
continue corticosteroids and anticonvulsants
What is the crani bag at DUke?
cleviprex, keppra, mannitol, phenylepherine, precedex, epi
What are propofol, remifentanil, phenylephrine gtts rates?
-40-100mcg/kg/min ABW
-Max 40mg/kg/min for asleep motor mapping and awake craniotomy
-Remi 0.2mcg/kg/min IBW
-Phenylephrine 0.2mcg/kg/min
What medications reduce ICPs?
decadron 10mg
mannitol 50-100mg (0.25-0.5g/kg)
+/- lasix
What medications are anti-epileptics?
+/- keppra 1g
vimpat
What medications are antibiotics?
vancomycin
cefazolin
What are analgesic medications for neurosurgery?
tylenol
narcotic (hydropmorphone or fentanyl)
What are drugs specific to an awake crani?
caffeine
physostigmine
Caffeine
CNS stimulant
adenosine receptor antagonist
doesn’t allow adenosine to accumulate at receptor prohibiting drowsiness
What is the dose of caffiene?
60mg in 3mL
8-10 minutes after drips have been off or determination with attending of “slow wake up or caffeine headache?
Physostigimine
anticholinesterase
tertiary amine
crosses BBB
antagonizes CNS effects of (benzos, hyponotics) also commonly used for atropine poisoning, NMB reversal
What are monitoring considerations for intracranial mass leisons?
standard monitors
arterial line
foley catheter
+/- central line
PNS (do not monitor hemoplegic side b/c you may end up overdosing paralytics
+/- ventriculostomy for ICP monitoring (zero at external auditory meatus)
possible IONM monitoring
What are positioning considerations for intracranial mass leisons?
anticipate turning HOB 90-180 degrees
ensure ability to access all vital equipment
adequate IV line extensions
long breathing circuit
PNS often on LEs
HOP often elevated 10-15 degrees
patient may be supine, lateral, prone or sitting
anticipate sympathetic response with placement of Mayfield head pins
What are important anesthetic implications for maintenance of intraoperative intracranial mass leisons?
no preferred anesthestic technique
hyperventilation
avoid excessive PEEP
What are fluid management goals for intraoperative intracranial mass leisons?
glucose free crystalloid or colloids
replace blood loss with blood/colloids
What are ICP goals for intraoperative intracranial mass leisons?
EVD/ lumbar drain
increases in cerebral blood flow
What are PEARLs for emergence of an intraoperative intracranial mass leisons?
must be slow and controlled (straining or bucking can cause ICH or worsen cerebral edema)
aggressive BP management (SBP <140 or <160)– risk for hemorrhage or stroke
clevidipine, labetalol, esmolol
Surgical teams will do neuro exam immediately after extubation; prior to OR departure
What are post-operative considerations forintraoperative intracranial mass leisons?
admit to ICU for observation
transport with HOB elevated
manage hypertension
O2 transport
minimal pain post craniotomy
observe for seizures, neuro deficits, increase ICP
What is an awake awake craniotomy for a tumor?
no infusions until closing
propofol bolus for pins
What is asleep-awake for craniotomy for a tumor?
start under GA with LMA/ETT
wake the patient up once tumor is exposed
propofol gtt 40mcg/kg/min ABW
remi gtt 0.2-0.4mcg/kg/min IBW
Describe an anesthetic plan for an asleep craniotomy for a tumor?
TIVA
IONM
asleep motor mapping
GETA- no IONM
When are awake craniotomies used?
epilepsy surgery and resection of tumors in frontal lobes and temporal lobes when speech and motor are to be assessed intraoperatively
- allow for patient cooperative with functional testing of the cortex
- performed when “eloquent cortical tissue” (tissue that is involved in motor, visual, or language function) is in close proximity to resection
What are the advantages of awake cranis?
reduced size of resection
reduced surgical time
reduced post operative neurological deficits
What are patient considerations for awake craniotomies?
airway
temperature
anxiety
age and maturity
claustrophobia
psychiatric disorders
history of nausea, vomitting
Describe the process of an awake craniotomy?
patient considerations
asleep with LMA for exposure
awake for cortical mapping and tumor resection
sedated for MRI deployment
-evaluate resection
** MRI not always applicable
- when tumor resection complete use appropriate anesthetic to keep comfortable
What does monteris medical LITT provide interventions too?
epilepsy
glioblastomas
recurrent brain metastases
radiation necrosis
MR Thermography
uses phase change to calculate real time (8s delay) temperature data at and around probe
thermal dose confirmed in real time using bio-thermodynamic theory
White line- 43-60 min vaporized
blue line- 43C- 10min dead
yellow line- 43C 2 minute (recoverable)
What is LITT?
takes place with insertion of optical fibers carrying the laser energy that is absorbed by the tissue and converted into heat, causing irreversible tissue destruction and protein denaturation when using temperatures above 50C
What is the laser penetration into the tissues?
~2mm
What is a function of time and temperature with LITT?
cell death
What equation is used for temperature dependence of reaction rates in LITT?
arrhenius equation
What is an anesthetic plan for LITT?
GETA with prop and remi
preop- emend, ant-epileptics if needed
vanco+ ancef
induce with roc
closing: IV tylenol
When do you administer ancef in LITT?
after initial MRI
What is the dose of remi in LITT procedures?
0.2-0.4mcg/kg/min
What does deep brain stimulation treat?
treats several disabling neurological symptoms- essential tremor, dystonia, and focal epilepsy
What is awake DBS?
involves physiological localization while patients are awake
localization methods include: microelectrode recording and/or intraoperative test stimulation to assess for acute stimulation-induced adverse or therapeutic effects
What is alseep DBS?
used for to patient preference (anxiety/fear)
What is deep brain stimulation?
a surgically implanted, battery operated medical device, implantable pulse generator (IPG) that delivers electrical stimulation to specific areas in the brain that control movement, this blocking the abnormal nerve signals that cause symptoms
What are the three components of the DBS system?
lead
extension and IPG
What is the lead in DBS?
electrode
thin insulated wire- inserted through a small opening in the skull and implanted into the brain
tip of the electrode is positioned specific brain area
What is the extension in DBS?
insulated wire that is passed under the skin of the head, neck and shoulder, connecting the lead to the implantable pulse generator
What is the IPG
battery pack
implanted under the collarbone, lower chest or skin over the abdomen
What do patient have to take for ROSA DBS?
ROSA DBS patients need to take their epileptic medication
What is the intra-operative set up for DBS?
2 IVs
arterial line (rarely)
extension to bolus LR (regular tubing, green + purple + green_
existing bag: purple + green
What is the advantage of ROSA?
robot allows for greater accuracy in placing electrodes that show where seizures occur
used in epilepsy surgery and deep brain stimulation
What are the components of the posterior fossa?
cerebellum
brainstem
cranial nerves 1-XII
large venous sinuses
What is the function of the cerebellum?
movement and equilibrium
What are the functions of the brainstem?
autonomic nervous system
CV and respiratory centers
RAS
Motor and sensory pathways
What are brain stem injury symptoms?
bradycardia/ HTN
bradycardia and hypotension
How does bradycardia and hypertension occur?
trigeminal nerve stimulation (cushing’s reflex)
How does bradycardia and hypotension occur?
glossopharygneal or vagus nerve stimulation
What nerves can impair gag reflex and increase risk of aspiration if tumors are located near them?
glossopharyngeal and vagus
What are the cranial nerves that control the pharynx?
cranial nerves IX, X, XI
What are anesthetic considerations for posterior fossa tumors perioperatively?
no preferred anesthestic technique
hyperventilation
avoid excessive PEEP
What is positioning for posterior fossa tumors?
may be sitting, modified lateral or prone
Discuss the implications of sitting with posterior fossa tumors?
back is elevated 60 degrees while the legs are elevated with knees flexed
head is fixed in three point holder with neck flexed
arms remain at sides with hands resting on lap
When is the sitting position most commonly used?
tumors of the pineal region, 4th ventricle, or midline cerebellum
What are the advantages to the sitting position?
improved surgical exposure (more anatomically correct)
less retraction and tissue damage
less bleeding
less cranial nerve damage
better resection of lesion
access to airway chest and extremities
Disadvantages of Sitting position
CV compromise (postural hypotension, arrhythmias, venous pooling)
pneumocephalus
Nerve injuries
What are symptoms of pneumocephalus?
delayed awakening, HA, lethargy, confusio
How does a pneumocephalus occur?
(open dura-> CSF leak-> air enters)
after dural closure air can act as a mass lesion as CSF reaccumulates
How does a pneumocephalus resolve?
usually resolves spontaneously
tension pneumocephalus (burr hole to relieve)
What are common nerve injuries in the sitting position?
ulnar nerve compression (arms across abdomen, pad elbows)
sciatic nerve stretch (pillow under knee)
Lateral peroneal compression (pad knees)
Brachial plexus stretch
(pad under arms to support shoulders
When does a venous air embolism occur?
pressure in a vein is subatmospheric
level of incision is >5cm higher then the heart
patients with PFO can have air enter arterial circulation
What is a paradoxical air embolism?
air enters left side of heart and travels to systemic circulation
occurs when right heart pressure is greater than left
common in patients with PFO
Describe what physiologically occurs with slowly entrained air?
small bubbles enter and travel to the heart
air enters the pulmonary circulation and lodges in capillary beds, increasing PVR
gas eventually diffuses into alveoli and are excreted
when the amount of entrained air exceeds pulmonary clearance, PAP progressively rises
Cardiac output decreases in response to increase in RV afterload and RV failure ensuses
Describe what physiologically occurs with rapidly entrained air?
large bubbles enter and lodge in the SVC, RA or RV
impedes flow through the right heart
slow increase in PAP, cardiovascular collapse follows
Signs and Symptoms of VAE
decreased ETCO2
decreased PAO2
decreased SaO2
spontanous ventilation
mill wheel murmur
detection of ET nitrogen
increased PaCO2
hypotension
dysrhythmias
How do you monitor for a VAE?
capnography
CVP/PA line
precordial doppler
* do not rely on one monitor alone to diagnose VAE
What is the most sensitive to detecting a VAE?
TEE (5-10x more sensitive then doppler, detects 0.25ml of air)
what is the least sensitive at detecting a VAE?
MAP
Describe the trend of sensitivity of VAE montioring (most sensitive to least sensitive)
TEE-> precordial doppler-> ETCO2-> PAP-> CVP-> PaCO2-> MAP
How much air does it require for ETCO2 to decrease?
15-25ml of air
How much air does it require for PAP to increase?
increases with 20-25ml of air
What is the treatment for a VAE?
100% O2, discontinue N20
notify surgeon to flood field or pack wound
call for help
aspirate from CVP line (have stockcock close to insertion site; aspirate with 30-60mL syringe)
volume load
Jugular vein compression
inotropes/vasopressors
PEEP
position patient LLD with slight trendelenberg
CPR if needed
Craniocervical decompressions
cerebellum protrudes through foramen magnum (compresses brainstem and cervical spinal cord)
Types 1-4
syringomyelia
what is syringomyelia?
CSF is abnormally located in spinal cord
How do you position a chiari malformation?
prone or sitting
What is the EBL for a chiari malformation?
large venous sinuses
What are anesthetic considerations for a chiari malformation?
vital sign instability due to brain stem manipulation
postoperative pain management
What are the two types of pituitary tumors?
nonfunctioning and functioning
What is a nonfunctioning pituitary tumor?
non-secretory
-arises from growth of transformed cells of anterior pituitary
generally well tolerated until 90% of gland is non-functional
What is a functioning pituitary tumor?
secretory
cushing’s disease (ACTH)
acromegaly (GH)
prolactinomas (prolactin)
TSH adenomas (TSH)
What is the size of a macroadenoma?
> 1cm
What is the size of a microadenoma?
<1cm
What are intraoperative considerations for pituitary tumors?
transsphenoidal approach necessitates HOB elevated 10-20 degrees
ORAL RAE or reinforced ETT
avoid hyperventilation (reduction in ICP result in retraction of pituitary into the sella tursica, making surgical access difficult)
potential for mass hemorrhage as the carotid arteries lie adjacent to the suprasellar area
mouth and throat pack: placed to absorb glottic blood and minimize postoperative vomitting of blood
(document time of throat pack in and when it comes out) + OG Tube
avoid positive airway pressure upon extubation
What are pre-operative evalulations for pituitary tumors?
visual field evaluation
S/S increased ICP
endocrine labs
electrolytes
steroids?
What is postoperative management for pituitary tumors?
DI (usually self limiting)
-treat with vasopressin or desmopressin (DDVAP)
SIADH
What is the leading cause of non-traumatic intracranial hemorrhage?
cerebral aneurysm
Where are cerebral aneurysms commonly located?
anterior circle of willis
How is a subarachnoid hemorrhage caused by an aneurysm?
the aneurysm fills with blood and can rupture, spilling blood into the subarachnoid space, creating subarachnoid hemorrhage
What can a cerebral hemorrhage lead to?
permanent brain damage, disability or death
What are the two types of cerebral aneurysms?
unruptured and ruptured
What are symptoms of an unruptured aneurysm?
headache
unsteady gait
visual disturbances
facial numbness
pupil dilation
drooping eyelid
pain above or behind eye
What are symptoms of a rupture cerebral aneurysm?
sudden, extremely severe HA
N/V
LOC prolonged coma
focal neuro deficits
hydrocephalus
seizure
S/S of increased ICP
What is the Hess and Hunt grading system for aneurysms/SAH?
useful in evaluating the patient’s condition, prognosis and ultimate clinical outcome
Grade 1-5
What are complications of a rupture cerebral aneurysm after surgery?
vasospams and/or rebleed
What does a vasospasm cause?
ischemia or infaraction
exact mechanism unknown
What is the gold standard for diagnosis of a vasospasm?
digital subtraction angiography
What treats a vasospasm?
calcium channel blockers
When does re-bleeding following a SAH peak?
seven days post incident
WHat is the major threat to delaying a ruptured cerebral aneurysm surgery?
rebleeding
What is 80% of the M/M from ruptured cerebral aneurysms?
rebleeding
How are re-bleeds treated?
anti-fibrinolytic therapy
After an aneurysmal subarachnoid hemorrhage, what is utilized to prevent and treat cerebral vasospams?
triple H therapy
induced hypertension
hypervolemia
hemodilution
Describe triple H therapy?
goal is to treat ischemia with an increase in CPP
Hypertension (SBP 160-200mmHg)
hemodilution (HCt 33% provides balance between O2 carrying capacity and viscosity)
hypervolemia (aggressive IV infusion of colloids and crystalloids for CVP > 10mmHg or PCWP 12-20mmHg
What is the rationale behind triple H therapy?
intended to increase CBF in brain areas that become ischemic due to intense vascular narrowing
Normally, increase in CBF would not result from increased BF, but with vasospasm the vascular bed becomes passive
therefore increasign CPP by increasing volume or by systemic administration of vasoactive drugs may reverse symptoms of cerebral ischemia
Describe an anesthetic plan for endovascular coiling in IR
GETA with complete muscle paralysis
controll CPP
minimal narotic needs since minimally invasive
a line preferred
minimal to no blood loss
heparin may be used for ACT 200-250
same postop concerns as clipping
How is an endovascular aneurysm coiling performed?
standard arteriogram is performed to located anuerysm, catheter is passes, often through femoral vessels and coil is advanced
What are advantages to endovascular aneurysm coiling?
shorter stay, less anesthetic requirements, uncomplicated positioning, minimally invasive
What are complications to endovascular aneurysm coiling?
aneurysm rupture/ subarachnoid hemorrhage (rapid transfer to OR for clipping)
vasospasm
CVA
incomplete coiling
What does the coil do?
coiling prevents the flow of blood and prevents the rupture
How are cerebral aneurysms most commonly treated in the OR?
microsurgical clip ligation
What is the approach for How are cerebral aneurysms in the OR?
craniotomy approach, parent vessel giving rise to aneurysm is identifed
aneurysm neck is isolated, a clip is placed across the neck, excluding if from ciruclation
What may be neccessary with giant aneurysms (<2.5cm)
deep circulatory arrest
Describe anesthesia goals of a cerebral aneurysm?
maintain optimum CPP
Decrease CPP rapidly if rupture occurs during surgical clipping
maintain transmural pressure (MAP-ICP)
decrease intracranial volume (blood and tissue); provides slack brain
minimizes CMRO2
Describe pre-induction of a cerebral aneurysm?
limit sedation (hypercapnia)
A line
2 large bore PIVs
type and crosss 2-4 units PRBCs
Remember HOB will be turned 90-180 degrees
Describe induction of a cerebral aneurysm?
smooth induction (difficult airway, full stomach)
Aggressive BP and HR control (narcs, beta blockers, deepen anesthetic)
Describe maintenance of a cerebral aneurysm?
may use TIVA or anesthetic gases
temporary occulsion of a cerebral artery
Maintain BP 15-20% below baseline to prevent vasospasm, decrease EBL, and allow for better exposure and visualization
Employ methods for cerebral protection and to reduce ICP if neccessary
Describe intra-operative fluids management of a cerebral aneurysm?
normovolemic
expand blood volume wiht colloids
have PRBC available
NO GLUCOSE
Describe intra-operative BP management of a cerebral aneurysm?
control of BP is critical to successful outcome of case (remember increase BP increase TMP across anuerysmal wall= rupture of aneurysm)
surgeon may ask for temporary increase in MAP to 80-100mHg (20-30% of baseline) to provide for collateral flow if a feeder vessel is clamped for a short period to allow for clipping of aneurysm
post clipping MAP is kept at 80-100mmHg
When is an aneurysm likely to rupture?
dural incision
excessive brain retraction
aneurysm dissection
during clipping or releasing of clip
Describe the treatment of an aneurysm rupture?
immediate, aggressive fluid management and replacement of blood loss
propofol bolus for brain portection, to decrease MAP and decrease BL
decrease MAP to 40-50mmHG (clevidipine, labelatol, esmolol)
surgeon may apply temporary clip on parent vessel to control bleeding, restore BP after clipping to improve collateral flow
What is an arteriovenous malformation?
congenital abnormality that involves a direct connection form an artery to a vein “nidus” without a pressure modulating capillary bed
What is the most common presentation of an AVM
intracranial hemorrhage
What is the treatment for an AVM
intravascular embolization
surgical excision
radiation
What are preoperative considerations
limit sedation (hypercapnia)
A line
2 large bore PIVs
type and crosss 2-4 units PRBCs
Remember HOB will be turned 90-180 degrees
What is the potential blood loss in an AVM?
potential for significant BL (up to 3L)
What is cranial nerve decompression?
treats disorders of cranial nerves
trigeminal neuralgia, hemifacial spasm, glossopharyngeal neuralgia
unilateral
usually caused by compression of a vascular structure
Where is the incision of cranial nerve decompression?
retroauricular incision
What is the culprit for trigeminal neuralgia?
superior cerebellar artery
What is the positioning for cranial nerve decompression?
lateral (bump)
prone
supine
What monitors are needed for cranial nerve decompression?
facial nerve monitoring
brainstem auditory evoked response (BAER)
EMG
What is the anesthetic plan for cranial nerve decompression?
TIVA
brain relaxation
with multimodal PONV
What are the types of spinal cord surgeries?
spinal cord stimulators
intrathecal pumps
scoliosis
ALIF/TLIF
ACDF
Why are spinal surgeries performed?
performed for symptomatic nerve root or cord compression secondary to trauma or degenerative disorders
Compression, prolapse, spndylosis
What does the surgery correct?
correct deformities
decompress the cord
fuse the spine if disrupted by trauma or degenerative condition
reset a tumor or vascular malformation
drain an abcess or hematoma
Preoperative assessment of Spinal surgery
stability of ROM
comprehesive patient review of systems
potential difficult airway management (cervical and thoracic disease)
Neuro function (symptoms, deficits)
What monitoring for spinal surgery?
standard monitoring, BIS, quantative TOF
arterial line, cell saver, neuromuscular blockade
foley
2 PIVs
TIVA, SSEPs, MEP and/or EMG
bilateral molar and midline tongue bit blocks (MEP)
Airo CT
What is positioning for spinal surgery?
ensure ability to access all vital equipment
adequate IV line extension
pt may be supine, lateral, prone
anticipate sympathetic response with placement of Mayfield head pines
correct padding of bony areas, positioning of head, pressure off eyes
What is an ACDF?
anterior cervical discectomy and fusion
surgery to remove a herniated or degenerative disk in the neck
disc excised in a piecemeal fashion and bone graft placed in intervertebral space with fusion performed to maintain stability
What is EBL for an ACDF?
minimal EBL <200ml
corepectomy may have increased EBL with 100-400ml
What approach is preferred for ACDF?
left side
what is an corpectomy
removing the front parts of the vertebra, vertebral body
portion of bone that surrounds and protects the spinal cord is preserved
bone graft inserted into the open space and stimulates new bone growth to occur that eventually joins the upper and lower vertebrae together
Describe the anesthetic implications of an anterior spinal fusion
anterior lumbar interbody fusion
EBL 100-250ml per level
LE perfusion related to retractor iliac vessel compression
Lateral lumbar interbody fusion (LLIF) EBL and monitoring?
100ml per level EBL
EMG monitoring
Oblique lumbar interbody fusion monitoring
+/- EMG (mainly for dilator placement)
Describe the anesthetic implications of an posterior spinal fusion
fusion is facilitated and stability obtained through insertion of pedicle screw and a rod constructs and insertion of a structural graft to promote bony arthrodesis
- posterior lumbar interbody fusion (PLIF)
transforaminal lumbar interbody fusion (TLIF)
minimally invasive TLIF (MITLIF)
SSEPS monitored
What is the EBL for PLIF/TLIF?
200-500ml per level
What is the EBL for MITLIF?
100ml per level
laminectomy
Laminectomy provides decompression of the neural elements of the lumbar spine via a posterior approach
PLIF posterior lumbar interbody fusion
consists of a bilateral laminectomy and removal of the inferior facet and the medial portion of the superior facet followed by discectomy and fusion.
TLIF is a
unilateral approach via the intervertebral foramen with bilateral pedicle screws placed at the level to be fused. Foraminal nerve root decompression followed by discectomy is performed and a spacer is inserted into the disc space (i.e. “fusion cage”) to stabilize the anterior column. The posterior column is then stabilized by adding bone graft followed by rod or plate attachment to the pedicle screws.
When is bracing completed for scoliosis?
curves 20-40C
initiated to prevent further curvature
does not correct
When is surgical correction of scoliosis warranted?
curves > 40C
pulmonary function testing encouraged
VC < 40% may require post op ventilation
30-60 curves will require
VC decreased by 25% and TLC decrased by 27%
90 curve in spinal for pulmonary function
VC decreased by 70% and TLC <50%
Lung function abnormalities are detectable with what cobb angle and what lung dieasese?
50-60
restrictive lung disease
SPO
Posterior column osteotomy with posterior ligament and facet joint resection which provides up to 10-degrees of correction.
Can cause profuse bleeding from epidural space (100-250 mL per level)
PSO
Removes posterior ligament and pedicles with resection of a triangular wedge of the vertebral column and provides 30-60 degrees of correction. Pedicle screws are placed at least three levels above and below the osteotomy and laminectomies performed one level above and below.
VRO
Involves circumferential resection of the vertebral body with all bone anterior to the posterior longitudinal ligament resected and complete exposure of the spinal cord.
PSO/VRO
Anticipate rapid and significant blood loss (500 mL- 2 L per level)
What monitors are needed for scoliosis cases?
Standard ASA + continuous arterial BP, BIS, quantitative TOF
Monitor EBL continuously, record at least every 30minutes (there will be surgical field losses not captured by cell saver)
Labs at least every 1 hour (or 500 ml EBL): Shock Panel, ROTEM Extem and Fibtem14,15, Fibrinogen, and Platelet count
Ipsilateral SSEPs must be paused for accurate assessment of SV and SVV or PPV.
Quantitative TOF monitoring: ipsilateral SSEPs must be paused for accurate TOF assessment. Continuous SSEP stimulation of ulnar nerve results in increased acetylcholine with post-tetanic phenomenon. Wait at least 1 minute after SSEPs are paused to assess TOF recovery. IOM reported “baseline” MEP’s does NOT guarantee full recovery from neuromuscular blockade.
What are postoperative considerations for scoliosis?
Expect continued postoperative blood loss with typical Hgb decrease by 1-2g/dL in first 12 hours
If EBL >1.5L, discuss with surgical team postoperative continuation of TXA infusion at 1mg/kg/hr x 12 hours
Postoperative hypomagnesemia is a frequent occurrence with EBL >1L. Consider intraoperative magnesium infusion 1g/hr to prevent postoperative hypomagnesemia.
What is the case setup for scoliosis?
2 14-16-gauge PIVs
CVC minimum of 7.5 Fr double lumen catheter
if planned PSO or VCR—9.5Fr sheath introducer (a.k.a., MAC introducer)
Arterial line
BIS (secure with tegaderm prior to prone positioning)
Cell Saver with 2 suctions (125-mL bowl if EBL <1L; 225-mL bowl if EBL>1L)
+/- LiDCo and POC Hemoglobin (Hemocue)16
Belmont (with filter only- i.e. “mini” bowl) if planned PSO or VCR
Crossmatch PRBC x4-6 units
TIVA–Propofol + Analgesic infusions
Bilateral molar and midline tongue bite blocks to prevent tongue laceration with MEPs
