Intro to Neuro Anesthesia PPT Flashcards
How much does the adult brain weigh?
1350gm (2% of tbw)
What is CBF? (flow)
45-55 ml/100g/min
How do you calculate CBF?
CBF= CPP/CVR
How much of your cardiac output goes to the brain?
12-15%
what is the CMRO2 of the brain?
3/5ml/100g/min (20% of total O2 consumption)
How do you calculate CPP?
CPP=MAP-ICP
What is CVR? (flow)
1.5-2.1 mmHg/100g/min/ml
How do changes in the CBF change CMRO2?
They are directly coupled.
What happens to CMRO2 when you sleep?
it decreases
For every 1 degree celsius decrease in body temp below 37 how is CBF effected?
decreases 7%
How do volatile anesthetics effect CMRO2?
reduces it
Rank different induction medications in order of decreasing CMRO2….
thiopental>etomidate>propofol
What MAP is required to maintain CBF?
70-150
What is the Myogenic Hypothesis?
transient changes in CBF (3-4 min) due to rapid changes in MAP. Most likely due to direct changes in the tone of the vascular smooth muscle.
Neurogenic innervation includes
cholinergic, adrenergic, serotonin, and vasoactive intestinal peptide.
Neurogenic influence is greatest on?
large cerebral arteries.
How does HCT and viscosity effect CBF?
decreases CBF when HCT is >55%
What type of pt are we concerned with high HCT?
smokers
In case you didn’t do my Nag questions….
what is an astrocyte?
support, metabolic function, nutritive functions
ependymal cells
lines cavities of the CNS and makes up the walls of the ventricles
microglia cells
phagocytosis
oligodendrocytes
insulation for axons- myelin sheath in brain and spinal cord
schwann cells
insulation- myelin sheath in peripheral nervous system
Tell me about the BBB
effective isolation for the brain and spinal cord, tight junctions between cells.
What portions of the brain are exempt from the BBB?
area postrema, pituitary gland, pineal gland, choroid plexus, and parts of the the hypothalamus
VAAs and increased CBF rank em
halothane»enflurane>desflurane=idoflurane>sevoflurane
How does N2O effect the brain?
increases CBF, ICP, and CMRo2
How does Ketamine effect PaCO2, CBF and ICP without controlled ventilation?
increased!!!!
How do you minimize the effects of ketamine?
give it with another sedative or anesthetics and with controlled ventilation
What do benzos and barbs do to CMRO2 and CBF?
reduce them in a dose dependent fashion
Do narcs effect CBF and CRMO2?
NOPE
Why do NDMR matter for the brain?
only poor effect is from histamine release.
What does succs do for the brain?
increases ICP in light pts.
increases CBF for cerebral activation from muscle spindle apparatus
try and defasiculate if going to RSI
4 determinants of CBF
brain (12%), intracellular water (78%), CSF (~75ml), and blood (~50ml).
total is 1200-1500ml
What is the normal range of ICP?
5-15
What is considered intracranial HTN
sustained ICP >15-20
What happens when ICP is over 30?
CBF progressively decreases ->ischemia -> cerebral edema -> increased ICP-> CBF decreases-> more ischemia -> more edema….. vicious cycle.
In elevated ICP- what happens to the CSF?
CSF volume will decreases- or translocate to the spinal compartment.
What are some signs of ICP?
NV HTN Bradycardia Personality changes Altered LOC Altered patterns of breathing Papilledema
