STUVIA 2024/2025
1. Science
2. Medicine
3. Surgery
CP II: Neuro Trauma
cbf =
cerebral perfusion pressure/cerebral vascular resistance
CBF global
45-55 cc/100 g tissue/min [15% of CO]
0:07
/
0:45
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CBF cortical
75-80 cc/100 g tissue/min
CBF subcortical
20 cc/100 g tissue/min
CBF ischemia
20 cc/100 g tissue/min
CBF complete cortical suppression
<15 cc/100 g tissue/min
%
membrane failure & cell death
CBF membrane failure and cell death
<15 cc/100 g tissue/min
baseline CMRO2
3-3.8 cc O2/100 g brain tissue/min
O2 utilization ____% electrical activity, _____% cellular integrity
60% electrical, 49% cellular integrity
what decreases CMRO2? (5)
hypothermia
halogenated agents
propofol
etomidate
barbituates
for ever 1 degree decreases, how much does CMRO2 decrease?
7%
what temperature does EEG suppression occur?
18-20 C
hypothermic protocols for CMRO2
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32-35degrees for 12-24 hr after hospital admission
what increases CMRO2? (4)
hyperthermia
seizures
ketamine
nitrous oxide
hyperthermia >_______C destroys neurons and will decrease CBF
42
CPP: brain autoregulated at ____-____ mmHg or a MAP of ____-____ mmHg
50-150 mmHg
60-160 mmHg
CPP =
MAP - ICP (or CVP), whatevers higher
when autoregulation is impaired, CPP is dependent on
BP
CPP is abolished by(3)
intracranial tumor
head trauma
volatile anesthetics
%
CPP less than 50 consequences
what's going on?
risk of (1)
vessels are maximally dilated
CBF become pressure dependent
risk of cerebral hypoperfusion
CPP 50-150
what's going on?
range of autoregulation
CBF is constant over a range of pressure
CBF >150
what's going on?
risk of (2)
vessels are maximally constricted
CBF becomes pressure dependent
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risk of cerebral edema
venous pressure impact on cerebral volume
high venous pressure decreases venous drainage and increases cerebral volume
creates a back pressure to the brain that can alter arterial/venous pressure gradient [MAP-CVP]
conditions that increases venous pressure (4)
jugular compression from positioning
increased intrathoracic pressure secondary to coughing/PEEP
vena cava thrombosis
vena cava syndrome
PaCO2 and CBF
linear relationship
in terms of PaCO2, what controls cerebral vascular resistance?
pH of the CSF around arterioles
PaCO2 of 40 mmHg = CBF of _____ mL/100g of brain tissue/min
50
for every 1 mmHg INCREASE/DECREASE in PaCO2 = ___-____ cc/100g brain tissue/min
INCREASE/DECREASE in CBF
1-2 cc
Maximal vasodilation occurs at PaCO2 of
%
80-100 mmHg
Maximal vasoconstriction occurs at PaCO2 of
25 mmHg
respiratory acidosis impact on CBF
increase
respiratory alkalosis impact on CBF
decrease
metabolic acidosis impact on CBF
no effect
H+ does NOT cross BBB
PaO2<50-60 mmHg impact on cerebral vasculature
cerebral vasodilation and increases CBF
PaO2 >60 mmHg
no effect on CBF
nL ICP
5-15 mmHg
cerebral HTN ICP
>20 mmHg
Monroe-Kellie Hypothesis
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