Neuro Anesthesia Flashcards
3 major components of the IC contents:
- 1- brain
- 2 – CSF
- 3 – blood
insert circle of willis image
- know where it starts
- branches
- where it goes
Blood flow supplied by
4 large arteries -
2 carotid and 2 vertebral arteries - which merge to form the Circle of Willis at base of brain
the brain is enclosed by the skull except for the foramen magnum. hence, the Foramen magnum is a site of
herniation
Arteries arising from circle of Willis give rise to
pial arteries,
which branch out into smaller vessels called penetrating arteries and arterioles
Normal Rate of Cerebral Blood Flow
-50-65ml / 100 Gm of brain tissue / minute
o 750-900 ml/min for entire brain
Cerebral Blood flow is what % of CO?
15% of cardiac output
The most powerful factor of CBF:
CO2
Doubling CO2 does what to CBF?
doubles CBF
what does hypothermia do to CBF?
decreased CBF
hyperthermia does what to CBF?
increases CBF
CBF with age:
CBF decreases with age
Hypertension shifts autoregulation curve which direction? what happens to CBF?
- rightward shift
- increases CBF
High ICP. What is one of the first things we can do to help reduce it?
hyperventilate
CO2 combines w/ H2O to form carbonic acid, which forms H-
o The H-’s are what cause
the vasodilation of cerebral vessels (causing an increase in CBF)
Studies show electrical stimulation of excitatory glutaminergic neurons leads to increase in
intracellular calcium ion and vasodilation of nearby arterioles
The cerebral blood flow is maintained fairly stable for a MABP of
50-150/60-160.
Beyond MABP of 150 you will get an increase in cerebral blood flow and will be at risk in developing
hemorrhage…. < 50= hypoperfusion
Autoregulation of CBF is responsive to what two mechanisms?
o mean blood pressure changes
o pulsatile pressure (perfusion pressure– for example…decreased during Cardio Pulmonary Bypass)
• People with hypoperfusion/ cerebral ischemia, autoregulation is shifted
to the left
• People with chronic HTN, autoregulation is shifted to the
right
• Brain uses what at a near constant rate?
O2
Cerebral circulatory system has strong sympathetic innervation that passes upward from the superior cervical sympathetic ganglia and then into
the brain
transection of SNS or mild stimulation of SNS usually causes little change in CBF because the blood flow autoregulation overrides the
nervous effects
When MAP rises acutely during strenuous exercise, SNS constricts the large and intermediate-sized brain arteries enough to prevent the high pressure from reaching the smaller brain blood vessels. Thus, preventing
vascular hemorrhages
what area of the brain is most sensitive for hypoxia / ischemia?
hippocampus (area for recent memories)
