Neuro & Anaes Flashcards
(27 cards)
NB Be able to label skull & brain anatomy ie. go look at diagram!
Be able to label Circle of Willis! They asked it last time! Go look at a diagram
Monro-Kellie doctrine:
If you have an enclosed / fixed space, and one of the contents increases, one of the others must decrease otherwise there will be an increase in intracranial pressur
Cerebral Perfusion Pressure formula
CPP = MABP – ICP
How does PaCO2 affect ICP
increases ICP
As it increases, you get intracerebral vasodilation which will cause an increase in the blood volume in your brain, and this will lead to an increase in ICP.
significance of 8kPa and O2
below 8kPa PaO2 vasodilatory effects start happening = more blood into brain . Brain wants more oxygen
Significant numbers of PaCO2 and cerebral blood flow
- 10.6kPa = 2x Cerebral blood flow
- 2.7kPa = half cerebral blood flow
The main factors that will increase the oxygen demand in the brain
- incr temp
- convulsions
- incr electrical activity
What is CaO2
CaO₂ stands for arterial oxygen content, which is the amount of oxygen carried in the blood per 100 mL of arterial blood
What is CMR(VO2)
CMR(VO₂) stands for Cerebral Metabolic Rate of Oxygen Consumption — it’s a measure of how much oxygen the brain is using per unit time
Units: mL O₂ / 100g brain tissue / min
indicates neuronal activity
The effect IAA has on CMR(VO2)
N₂O: ↑ increases
Isoflurane: ↓↓ significantly decreases
Sevoflurane: ↓↓ significantly decreases
Halothane: ↓↓ significantly decreases
Desflurane: ↓↓ significantly decreases
The effect IAA has on CBF
N₂O: ↑ increases
Isoflurane: ↑ increases
Sevoflurane: ↑ increases (only if >1 MAC)
Halothane: ↑↑ markedly increases
Desflurane: ↑ increases
The effect IAA has on ICP
N₂O: ↑ increases
Isoflurane: ↑ increases (if >1 MAC)
Sevoflurane: ↑ increases (if >1 MAC)
Halothane: ↑ increases
Desflurane: ↑ increases
The effect IAA has on CSF Vol
Only Isoflurane is noted to increase CSF volume
The effect IAA has on Convulsion Risk
Only noted for Halothane: maintained response to CO₂
The effect IAA has on Response to CO₂
Halothane: maintained
Others: not specifically mentioned
The effect IAA has on Autoregulation Disruption
N₂O: +
Isoflurane: +
Sevoflurane: +
Halothane: +++
Desflurane: ++
Best IAA for brain
Isoflurane and sevoflurane are the most beneficial for our brains
Effect of IVA on CMR(VO2)
Thiopentone: ↓ (decreases in an alpha dose-dependent manner)
Propofol: ↓ (decreases in an alpha dose-dependent manner)
Etomidate: ↓ decreases
Ketamine: ↑ increases
Effect of IVA on CBF
Thiopentone: ↓ decreases
Propofol: ↓ decreases
Etomidate: ↓ decreases
Ketamine: ↑ increases
Effect of IVA on ICP
Thiopentone: ↓ decreases
Propofol: ↓ decreases
Etomidate: ↓ decreases
Ketamine: ↑ increases
Effect of IVA on CSF vol
Thiopentone: ↓ decreases
Propofol: ↓ decreases
Etomidate: ↑ increases (especially in at-risk patients)
Ketamine: ↓ decreases
Effect of IVA on Response to CO2
All four agents: Response to CO₂ is maintained
Thiopentone and CNS
Low doses can cause disinhibition
Recovery phase may involve dreams or hallucinations
