Neuro Flashcards
What is the most sensitive monitor for detecting a venous air embolism?
echocardiography
Why might hypothermia provide neuroprotection?
reduced release of excitatory neurotransmitters and catecholamines
What are the components of the intracranial space?
85% parenchyma
10% CSF
5-10% blood
What is the normal cerebral O2 requirement? Normal cerebral blood flow?
3.5 mL O2/min/100 g brain tissue
50 mL/min/100 g brain tissue
What is the relationship between PaCO2 and CBF?
linear between PaCO2 20-80
2% change in CBF for every 1 mmHg change in PaCO2
What is cerebral steal? In what setting does it occur?
shunting of blood flow away from patholigic regions toward normal regions in the setting of hypercapnea (vasodilatation)
What is inverse steal? In what setting does it occur?
shunting of blood flow toward patholigic regions away from normal regions in the setting of hypocapnea (vasoconstriction)
When should embolization of an intracranial mass be done relative to resection?
< 48 hours before
What are the primary concerns with operations in the posterior fossa?
small, noncompliant space
hemodynamic instability with traction on brainstem nuclei
risk to cranial nerve requiring NIOM
risk of VAE
What are the positioning concerns particular to posterior fossa surgery?
VAE
neck rotation obstructing jugular outflow
brachial plexus injury
What are the concerns for neurosurgery in the sitting position?
VAE and paradoxical embolus if a PFO is present
reduced preload causing bradycardia (Bezold-Jarisch reflex)
hypoperfusion of the brain or cervical spine
What is the goal of indirect neuroprotection? What are its components?
Preventing ischemia:
maintain cerebral oxygen delivery
maintain brain relaxation to minimize retratction
maintain serum glucose
What is the goal of direct neuroprotection? What are its components?
Tolerating ischemia:
reducing CMRO2
preventing apoptosis in response to ischemia
What is the optimal position of a multiorifice catheter for VAE aspiration? Success rate?
2 cm distal to the cavo-atrial junction
meh: 30-60%
What is normal serum osmolality? What is the upper limit when using hyperosmolar therapy?
normal: 275-295 mmol/kg
upper limit: 320 mmol/kg (higher can cause ATN)
What are the risks of mannitol?
leakage through a damaged BBB
hypovolemia leading to hypotension
serum osmolality >320 mosm/kg leading to ATN
expanding hematoma when tamponade effect is lost
What can cause hyponatremia after TBI?
cerebral salt wasting
SIADH
HPA dysfunction
What can cause hypernatremia after TBI?
mannitol or 3% saline use
diabetes insipidus (central)
How is Mg neuroprotective?
limits Ca2+ influx through NMDA receptors (less excitotoxicity)
downregulates aquaporin 4 (less cerebral edema)
decreases p53 (less apoptosis)
What is the role of gender in TBI?
death rate is significantly lower in women
(possible protection from estrogen/progesterone)
What is the effect of decompressive hemicraniectomy on severe TBI?
better Glasgow Outcome Scales at 6 & 12 months (DECRA and RESCUEicp)
How is severity of TBI categorized?
GCS 13-15: mild TBI
GCS 9-12: moderate TBI
GCS <9: severe TBI
What is the ICP goal in patients with TBI? CPP goal? PbtO2 goal?
ICP < 20 mmHg
CPP 50-70 mmHg
PbtO2 > 20 mmHg
Should patients with TBI be hyperventilated?
not routinely during the first 24 hours due to the risk of reduced CBF
Should patients with TBI be given steroids?
no, increased mortality in CRASH trial
How long should anti-seizure prophylaxis be given after TBI? Surgery?
typically 1 week for both
(less effective for late-onset seizures)
How is hemorrhage managed during interventional neuroradiology procedures?
attempt to “glue” the hole or embolize feeding vessels
reverse heparin with protamine
place ventriculostomy
What is the usual timecourse of neurogenic LV dysfunction?
resolves in 4-5 days
What are the methods to decrased aneurysm transmural pressure during clip placement?
temporary clip placement on feeding vessel(s)
controlled hypotension
adenosine-induced circulatory arrest
deep hypothermic circulatory arrest
Is hypothermia beneficial during aneurysm clipping?
no, the IHAST trial showed no benefit
Besides the usual reasons for delayed emergence, what must be particularly considered in neurosurgery?
intra-operative seizure resulting in a post-ictal state
What is the usual timecourse of vasospasm after SAH?
day 0-3: rare
day 3-10: peak incidence
day 10-14: resolving
