Pathophys Test 3
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What is the
primary energy source for brain function
Glucose, which is converted to ATP (adenosine triphosphate).
ATP essential for neuronal metabolism and conductive activities.
Review cerebral blood flow.
What effect would increase or decrease in BP have on diameter of cerebral arteries
When systemic arterial pressure or ICP increases, arterioles vasoconstrict to safeguard brain from hyperemic flow state.
Decrease in BP --> vasodilation, protecting brain from subflow states and subsequent infarction.
and pressure changes that affect brain’s ability to auto-regulate. (p.7)
Potent dilator as brain attempts to remove products of cellular breakdown as efficiently as possible
PaCO2 from 20-80 mmHg
CBF (cerebral blood flow) = ½ if PaCO2 = ½
CBF = double if PaCO2 = double
PaO2 <60 or O2 Sat <90 --> hyperemic flow state
90% of moderate-to-severe head-injured patients have ischemic brain tissue on postmortem
Within ischemic tissue is contained massive quantities of waste; majority = vasodilatory agents
– can result in loss of autoregulation (like SAH)
Blood contains many substances like calcium and free iron which are tolerated poorly in ventricular system and subarachnoid space of brain
Review metabolic factors and
that affect brain’s ability to auto-regulate. (p.7)
Use of cerebral vasodilatory drugs
Anti-hypertensives like Nipride
Change in MAP
Prolonged ICP > 35mmHg lasting longer than 20-30 minutes
Changes in CPP
Know how to calculate MAP
Know how to
cerebral perfusion pressure
Estimate of adequacy of cerebral circulation
Normal = 50-150 mmHg
Average = 80-100 mmHg
CPP <50 = ischemia
CPP >150 = hyperemia
CPP <30 = incompatible with life --> neuronal hypoxia and cell death
Pathophys Test 3