Neuro

Question 1

What is the most sensitive monitor for detecting a venous air embolism?

Answer 1

echocardiography

Question 2

Why might hypothermia provide neuroprotection?

Answer 2

reduced release of excitatory neurotransmitters and catecholamines

Question 3

What are the components of the intracranial space?

Answer 3

85% parenchyma

10% CSF

5-10% blood

Question 4

What is the normal cerebral O2 requirement? Normal cerebral blood flow?

Answer 4

3.5 mL O₂/min/100 g brain tissue

50 mL/min/100 g brain tissue

Question 5

What is the relationship between PaCO₂ and CBF?

Answer 5

linear between PaCO₂ 20-80

2% change in CBF for every 1 mmHg change in PaCO₂

Question 6

What is cerebral steal? In what setting does it occur?

Answer 6

shunting of blood flow away from patholigic regions toward normal regions in the setting of hypercapnea (vasodilatation)

Question 7

What is inverse steal? In what setting does it occur?

Answer 7

shunting of blood flow toward patholigic regions away from normal regions in the setting of hypocapnea (vasoconstriction)

Question 8

When should embolization of an intracranial mass be done relative to resection?

Answer 8

< 48 hours before

Question 9

What are the primary concerns with operations in the posterior fossa?

Answer 9

small, noncompliant space

hemodynamic instability with traction on brainstem nuclei

risk to cranial nerve requiring NIOM

risk of VAE

Question 10

What are the positioning concerns particular to posterior fossa surgery?

Answer 10

VAE

neck rotation obstructing jugular outflow

brachial plexus injury

Question 11

What are the concerns for neurosurgery in the sitting position?

Answer 11

VAE and paradoxical embolus if a PFO is present

reduced preload causing bradycardia (Bezold-Jarisch reflex)

hypoperfusion of the brain or cervical spine

Question 12

What is the goal of indirect neuroprotection? What are its components?

Answer 12

Preventing ischemia:

maintain cerebral oxygen delivery

maintain brain relaxation to minimize retratction

maintain serum glucose

Question 13

What is the goal of direct neuroprotection? What are its components?

Answer 13

Tolerating ischemia:

reducing CMRO₂

preventing apoptosis in response to ischemia

Question 14

What is the optimal position of a multiorifice catheter for VAE aspiration? Success rate?

Answer 14

2 cm distal to the cavo-atrial junction

meh: 30-60%

Question 15

What is normal serum osmolality? What is the upper limit when using hyperosmolar therapy?

Answer 15

normal: 275-295 mmol/kg

upper limit: 320 mmol/kg (higher can cause ATN)

Question 16

What are the risks of mannitol?

Answer 16

leakage through a damaged BBB

hypovolemia leading to hypotension

serum osmolality >320 mosm/kg leading to ATN

expanding hematoma when tamponade effect is lost

Question 17

What can cause hyponatremia after TBI?

Answer 17

cerebral salt wasting

SIADH

HPA dysfunction

Question 18

What can cause hypernatremia after TBI?

Answer 18

mannitol or 3% saline use

diabetes insipidus (central)

Question 19

How is Mg neuroprotective?

Answer 19

limits Ca²⁺ influx through NMDA receptors (less excitotoxicity)

downregulates aquaporin 4 (less cerebral edema)

decreases p53 (less apoptosis)

Question 20

What is the role of gender in TBI?

Answer 20

death rate is significantly lower in women

(possible protection from estrogen/progesterone)

Question 21

What is the effect of decompressive hemicraniectomy on severe TBI?

Answer 21

better Glasgow Outcome Scales at 6 & 12 months (DECRA and RESCUEicp)

Question 22

How is severity of TBI categorized?

Answer 22

GCS 13-15: mild TBI

GCS 9-12: moderate TBI

GCS <9: severe TBI

Question 23

What is the ICP goal in patients with TBI? CPP goal? PbtO₂ goal?

Answer 23

ICP < 20 mmHg

CPP 50-70 mmHg

PbtO₂ > 20 mmHg

Question 24

Should patients with TBI be hyperventilated?

Answer 24

not routinely during the first 24 hours due to the risk of reduced CBF

Question 25

Should patients with TBI be given steroids?

Answer 25

no, increased mortality in CRASH trial

Question 26

How long should anti-seizure prophylaxis be given after TBI? Surgery?

Answer 26

typically 1 week for both (less effective for late-onset seizures)

Question 27

How is hemorrhage managed during interventional neuroradiology procedures?

Answer 27

attempt to "glue" the hole or embolize feeding vessels reverse heparin with protamine place ventriculostomy

Question 28

What is the usual timecourse of neurogenic LV dysfunction?

Answer 28

resolves in 4-5 days

Question 29

What are the methods to decrased aneurysm transmural pressure during clip placement?

Answer 29

temporary clip placement on feeding vessel(s) controlled hypotension adenosine-induced circulatory arrest deep hypothermic circulatory arrest

Question 30

Is hypothermia beneficial during aneurysm clipping?

Answer 30

no, the IHAST trial showed no benefit

Question 31

Besides the usual reasons for delayed emergence, what must be particularly considered in neurosurgery?

Answer 31

intra-operative seizure resulting in a post-ictal state

Question 32

What is the usual timecourse of vasospasm after SAH?

Answer 32

day 0-3: rare day 3-10: peak incidence day 10-14: resolving