Neuro Flashcards
Glutamate neurotransmitter target are?
AMPA, kainate, NMDA
It is an excitatory neurotransmitter leads to membrane depolarization
Which brain processes has the greatest amount of energy consumption thus more O2 consumption
Neuronal electrical activity
So drugs that decrease neuronal activity will decrease O2 delivery (blood flow) e.g barbiturates, propofol, etomidate
The arterial BP in relation to CBF in a chronic hypertensive patients, the plot will shift to …. and the clinical relevance of this is to avoid …
Right
Global ischemic stroke following GA (with low MAPs)
So in chronic HTN, their baseline MAPs are higher than normal ptn
Volatile effect on CBF
It increases it (iso> des > sevo) by direct cerebral arterial vasodilation, the relationship btw MAP and CBF become linear
Because it increases CBF it will increase ICP (des > iso > sevo)
Methods to decrease CBF?
- IV anesthetic
- Decrease CMRO2 (prop, thiopental)
- Hyperventilating
- Avoid cerebral vasodilation and extreme HTN
Methods to decrease CBF by increasing venous outflow
Elevate head
Avoid construction of the neck
Avoid PEEP and excessive airway pressure
Methods to decrease CBF by reduction in CSF
- External ventricular drain.
- Lumber drain.
- Head elevation
- Acetazolamide
Methods to decrease CBF by reduction of cerebral edema?
- Osmotic therapy (mannitol, hypertonic saline).
- Furosemide.
- Dexamethasone (vasogenic edema)
Methods to decrease ICP?
1) decreasing Cerebral blood volume (decreasing CBF, increasing venous outflow)
2) Decreasing CSF
3) Reducing cerebral edema
4) Resection of space-occupying lesions
5) Decompression craiectomy.
Whats the normal CBF?
50 mL/ 100g/min = 12-15% of CO
Factors regulates CBF?
- CMRO2 via nerovascular coupling
- CPP via autoregulation
- PaCO2 & PaO2 via cerebrovascular reactivity.
- SNS
- CO
- Some anesthetics.
What is neurovascular coupling?
defined a proportional change in CBF to change in CMRO2 (increase/decrease in CMRO2 results in increase/decrease in CBF).
2 common causes decreasing CMRO2 and therefore decrease CBF?
Hypothermia (7% CBF for every 1 C below 37C)
IV anesthestics.
CMRO2 increased by …
seizure activity
CPP = … - …
MAP - ICP
What is the cerebral auto regulation?
is the CPP range btw upper and lower limits where CBF remains stable (~ 50mL/100g/min)
Conditions impairs cerebral autoregulation, and therefore resulting in a liner change between CPP and CBF
TBI, intracranial surgery, sever hypercapnia, inhaled anesthetics. ( so any changes in CPP will change the CBF due to the loss of autoregulation).
relation between PaCO2 & CBF
directional change (increase/decrease in PaCO2 will increase/decrease CBF)
a change of 1 mmHg of PaCO2 from 40 mmHg will change 1 mL/100g/min in CBF
How long the PaCO2-related changes in CBF lasts?
until the compensatory change in HCO3 concentration occur ~ 6-8 hours
Relation between PaO2 & CBF
inversely related (decrease in PaO2 less than threshold ~50 mmHg, result in increase CBF).
Effect of propofol and thiopental on CBF? and ICP?
decreases CMRO2 -> CBF via coupling effect.
decreases ICP
Why ketamine is avoided in patients with known intracranial disease?
because of its controversial effect (it increases PaCO2, CBF, & ICP if used solely, but it has no effect if used with other sedatives).
Effect of opoids and BZDs on CBF? ICP?
it decreases CMRO2 and CBF therefore decrease ICP. however the depression in respiration drive leads to increase in PaCO2 which may produce the opposite effect.
why opiods should be carefully administered in patients with intracranial disease?
it depresses consciousness, causes miosis, and the depression effect on respiratory drive causes increase PaCO2 which leads to increase ICP.
Effect of alpha agonist on CBF?
decreases arterial pressure -> decrease CPP & CBF with minimal effect on ICP
Effect of volitle on CBF at > 0.5 MAC? and ICP?
potent cerebral vasodilation and increase CBF & ICP even though they decrease CMRO2 (except N2O, it increases CBF & CMRO2 but often attenuated by co-administration of other anesthetics).
What defines ICP? and effect?
a sustained increase of >15 mmHg in cerebral pressure leading to decrease in CPP and CBF therefore resulting in cerebral ischemia.
What IV anesthetic causes Increases EEG frequency and therefore it is avoided in patients with seizures?
Etomidate. to prevent increase in ICP.
Can NMBs increases ICP?
it has no effect, but if they induce histamine release and hypotention then cerebral vasodilation occur which increases CBF and ICP (Succinlycholine increases ICP through increasing CBF for unknown mechanism).
Where do you place the A-line transducer to reflect CPP?
Tragus level
At what volume of CBF ischemia is detectable by EEG?
15 mL/100g/min
DI vs SIADH vs cerebral salt wasting after brain injury in terms of plasma Na?
DI: High serum Na
SIADH: low
CSW: low
Parasympathetic effect ?
SLUDD
Salivation
Lacrimation
Urination
Digestion, Defecation
Only opioid increases CBF?
Sufentanil
BBB prevents passing off ….
Glucose, electrolytes, mannitol, dextrose, amino acids, protein.
Allows lipid soluble, volatiles, water, CO2 and O2
2 medications decreases CSF production
Acetozolmide and furosemide
Only opioid increases CBF?
Sufentanil
BBB prevents passing off ….
Glucose, electrolytes, mannitol, dextrose, amino acids, protein.
Allows lipid soluble, volatiles, water, CO2 and O2
2 medications decreases CSF production
Acetozolmide and furosemide
Contralateral upper limb paralysis or sensory loss
- /+ aphasia (if dominant hemisphere)
- /+ hemineglect (if non-dominant hemisphere)
MCA lesion
Contralateral sensory/motor upper limbs or face
Temporal lobe- wernicke’s
Frontal lobe-Brock
Contralateral lower limb sensory loss or paralysis
ACA
Contralateral hemianopia with macular sparing a symptom of which lesion ? And what vessel effected?
Occipital or visual cortex
Supplied by PCA
Symptoms of lesion in;
Lateral medulla-vestibular nuclei
Lateral SPinothelamic
spinal trigeminal nucleus
Nucleus ambiguous
Sympathetic fibers
Inf cerebellar peduncle
Vomiting vertigo nystagmus
Ipsilateral face pain and sensation loss
Contralateral body pain and sensation loss
Dysphagia and horeseness, decrease gag reflex
Ipsilateral horner’s
Ataxia, dysmetria
These are supplied by PICA
Decreased lacrimation, salivation, taste, corneal reflex, and hearing
Differentiates a lesion supplied by … from PICA
AICA
Lesion supplied by …. will manifest as lock in syndrome, quadriplegic and loss of facial,mouth and tongue movements (with preservation of consciousness and blinking)
Basilar artery