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