Neuroanesthesia Pt. 2 (Exam I) Flashcards
How much CSF do we typically have at any given moment?
150mls
Where does CSF typically “pool”?
Cisterns
Areas where arachnoid membrane and pia mater are further apart.
Don’t need to know specific cisterns.
What is normal CSF pressure for a horizontal patient?
10 mmHg
What type of tissue lines the cerebral ventricles?
What does this tissue do?
Choroid Plexus (produces CSF)
Which cells excrete CSF?
Ependymal (E = Excrete)
What absorbs CSF?
Arachnoid Villi (A = Absorb)
What is the path of CSF?
In which ventricles is the majority of CSF produced?
Lateral Ventricles
CSF Diagram (Flip)
What is idiopathic Intracranial HTN?
CSF Buildup causing ↑ICP with no obvious reason.
Who is idiopathic intracranial HTN common in?
- Obese women of reproductive age.
What is another name for idiopathic Intracranial HTN?
Pseudotumor Cerebri
What is normal ICP?
7 - 15 mmHg
When is ICP considered pathologic?
> 20 mmHg
Whats a normal CPP?
60 - 80 mmHg
What is the critical ischemic threshold for CPP?
30 - 40 mmhg
What would the following do to CBF?
- Hypoxia
- Hypercarbia
- ↑ CMRO₂
↑CBF
Where does aqueductal stenosis occur?
Aqueduct of Sylvius (between 3ʳᵈ & 4th ventricles)
What are the three components of Cushing’s Triad?
- Irregular Respirations
- Bradycardia
- Widened pulse pressure
How long might the effects of hyperventilation on PaCO₂ last?
6 - 12 hours
What dose of Mannitol is typical in neurosurgery?
0.5 - 1 mg/kg
What are the benefits of corticosteroids in neurosurgery?
What are the negatives?
- Pros: Lowers local cerebral swelling (around tumors typically)
- Cons: May ↑BG and ↓ elasticity of blood vessels
What is parenchyma?
Functional Brain Tissue (grey & white matter)
What are potential concerns associated with utilizing hyperventilation to induce brain relaxation?
- Potential ischemia in some areas
- Brain relaxation temporary (6 - 12 hours)
What dose of decadron is typical for cerebral edema reduction?
10mg Q6 hours
What drug is typically paired with mannitol? Why?
Furosemide
Prevents rebound effect of cellular swelling from mannitol by inhibiting chloride osmoles.
What is the MOA of levetiracetam?
Binds to synaptic vesicle protein 2A (SV2A)
Inhibits release of Ca⁺⁺ by inhibiting this vesicles release.
What is a typical dose of Keppra?
500mg BID over 15 min
Which factors are associated with ION?
- Prone position
- ↓BP
- ↓ H/H
- Long surgery
- Large volume administration
Between LR & NS, which should be used in neurosurgery? Why?
NS > LR
NS = 308 mOsm/L
LR = 274 mOsm/L
NS will reduce cerebral edema.
What can occur with Dextran?
Dilutional coagulopathy
Does Hypothermia provide brain protection? Is it used?
Yes
But, no demonstrated benefits, and can cause arrhythmias & coagulopathy.
What is the recommended BG level for neurosurgery?
150 - 200 mg/dL
What is a pressure transducer placed into the subdural space or the brain parenchyma?
Subdural bolt
What is a catheter placed in the ventricle allowing for the drainage of CSF?
Ventriculostomy
What catheter allows for drainage of CSF but can be inaccurate for measurement of ICP due to the area of its placement?
Lumbar subarachnoid catheter
What is normal ScO₂ (cerebral oximetry)?
70% (+/- 20 - 30%)
What are SSEPs?
Cutaneous electric stimulation peripherally resulting in EEG changes
Are latency readings more reliable with SSEP or MEPs?
SSEPs
What are MEPs?
Stimuli elicited via electrodes in the head that cause a muscle reaction peripherally.
A __% decrease of amplitude in SSEPs and MEPs is significant.
50%
Which type of stroke is more deadly? Hemorrhagic or Embolic?
Hemorrhagic
What is the most common comorbidity associated with embolic strokes?
Cardiovascular disease
Especially Cardiomyopathy (large ventricle = large clot)
What is more common, embolic or hemorrhagic strokes?
Embolic (80%)
tPA is effective if administered within ___ hours of embolic stroke onset.
2 hours
What is the characteristic symptom of a subarachnoid hemorrhage?
- Thunderclap headache
- N/V
- Visual Disturbances
How does tPA work?
Catalyzes conversion of plasminogen to plasmin
Where does blood accumulate in subarachnoid hemorrhages?
Between arachnoid space & pia mater
What are common causes of intracranial hemorrhage?
- HTN
- AVM
- Aneurysm
- Trauma
- Coagulopathy
Vasospasm is thought to be caused by the breakdown products of ____ and _____.
Hgb & NO
How is vasospasm typically treated?
CCBs
- Nimodipine
- Verapamil
- Nicardipine
What therapy is used to prevent vasospams?
Triple H Therapy
- Hypertension (20 - 30 above baseline)
- Hypervolemia (really euvolemia)
- Hemodilution (Hct 30ish)
What functions do statins have in neurosurgery?
- Improve endothelial function
- ↓ oxidative stress/ inflammation
What function does Mg⁺⁺ have in neurosurgery?
Inhibition of Ca⁺⁺ mediated smooth muscle contraction
What function does cilostazol have in neurosurgery?
Antiplatelet
Vasodilation
What type of neursurgery uses MRI/CT imaging and 3-D coordinate system to target precise areas deep in the brain?
Stereotactic Neurosurgery
What are the old and new ways to do stereotactic neurosurgery?
- Old: Full frame on head preoperatively
- New: Fiducial markers placed on head
What movement disorders are commonly treated with deep brain stimulators?
- Parkinson’s
- Essential Tremor
- Dystonia
- Tourettes
What region of the brain is typically targeted with deep brain stimulators
Subthalamic Nucleus
What is the 1st surgical stage of Deep Brain stimulator implantation?
Placement of electrodes under light sedation with stereotactic technique. Patient awake during procedure.
What is the 2ⁿᵈ surgical stage of Deep Brain stimulator implantation?
GETA, one week after DBS placement with leads tunneled from brain to generator.
What additional monitoring device is often used for DBS placement? Why?
Precordial Doppler (Risk for VAE)
Where are DBS generators typically placed?
Typically below clavicle
What drug class should be avoided when doing stereotactic ablations for seizures?
Benzos (and barbiturates)
70 - 95% of epidural hematomas are associated with?
Skull Fractures
Tear of the _______ artery is common with epidural hematomas.
Middle Meningeal Artery
A tear of the ______ veins is common with subdural hematomas.
Sagittal
Between epidural hematomas & subdural hematomas, which can be treated with simple burr hole surgery?
Subdural
Intubate a neurosurgical trauma patient if the GCS is ___ or less.
8
What is the target CPP for neuro trauma patients?
70 mmHg
What is the typical symptom triad of hydrocephalus w/ normal ICP?
- Dementia
- Gait changes
- Urinary incontinence
Common symptoms of hydrocephalus w/ ↑ICP are…
- N/V
- LOC changes
- Papilledema
- ↓HR
- HTN
- Respiratory changes
How would a lumbar puncture differ between a hydrocephalus w/ normal ICP and a hydrocephalus w/ elevated ICP?
The hydrocephalus w/ elevated ICP will have a high pressure Lumbar Puncture
Normal pressure hydrocephalus is a form of ________ hydrocephalus.
Communicating
What type of hydrocephalus is defined by “CSF can exit the ventricles but can’t be effectively absorbed by arachnoid villi”?
Communicating
What is the most common cause of non-communicating / obstructive hydrocephalus?
Aqueductal stenosis
Narrowing of aqueduct of sylvius between 3ʳᵈ & 4th ventricles.
What are the three types of primary brain tumors discussed in lecture?
- Meningioma
- Glioma
- Glioblastoma
Are meningiomas typically benign or malignant?
- Usually benign
What are meningiomas typically found? What is the monitoring consequence of this?
- Usually near sagittal sinus
- Precordial Doppler for VAE is suggested
What are the characteristics of gliomas?
- Non- aggressive typically
- Surgical resection usually successful
What types of cells do gliomas arise from typically?
- Astrocytes
- Ependymal cells
- Oligodendrocytes
What are the characteristics of glioblastomas?
- Very aggressive
- Short life expectancy
Of glioblastomas, gliomas, and meningiomas, which is most common?
Glioblastomas
Pituitary tumors typically arise from cells of the _____ pituitary gland and are almost always _______.
Anterior : Benign
What are the two types of pituitary tumors?
- Microadenomas
- Macroadenomas
What is MEN-1 ?
Mutliple Endocrine Neoplasia Type 1
- Combined pituitary, parathyroid, and pancreatic islet cell tumors.
What are the characteristics of microadenomas?
- Hormone-secreting
What are the characteristics of macroadenomas?
- Non-hormone secreting
- Symptoms related to mass effect
What functions are associated with prolactin?
- Lactation
- Infertility
- Breast development
What functions are associated with ACTH?
- Adrenal hyperplasia
What issues are associated with excess growth hormone?
- Acromegaly (especially face & hands).
What is usually the origin of an acoustic neuroma?
- Benign schwanoma involving CN VIII.
What type of evoked potentials are used with acoustic neuroma excision?
Auditory Evoked Potentials
Bilateral acoustic neuroma formation may occur as part of _________.
neurofibromatosis
Where do metastatic brain tumors most often originate from?
Primary sites like lungs or breast
A diagnosis of metastatic brain tumor is more likely when there is one tumor present. T/F?
False. Multiple brain tumors = more likely to be metastatic from other bodily region.
Are metastatic or primary brain tumors more likely to bleed? Why?
Metastatic due to abnormal angiogenesis
Can N₂O be utilized for neurosurgeries?
Not really, caution with potential for VAE.
Retraction of the dura mater over the parietal lobe can induce what?
Trigeminal cardiac reflex
What is the trigeminal cardiac reflex?
Sudden ↓BP & ↓HR
What are the cardinal symptoms associated with VAE?
- Mill-Wheel murmur
- Hemodynamic Instability
- Sudden drop in EtCO₂
Where is ADH synthesized?
Supraoptic nuclei of the hypothalamus
How is ADH transported from the hypothalamus to the neurohypophysis?
Via the supraoptic hypophyseal tract
What is the treatment of DI?
- ½ NS
- Hourly maintenance fluid + ⅔ previous hour UO
- Desmopressin (if UO > 400 mL/hr)
