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cgordon05
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What is the primary energy source for brain function? (p.1)
- Glucose, which is converted to ATP (adenosine triphosphate).
- ATP essential for neuronal metabolism and conductive activities.
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Review cerebral blood flow.
What effect would increase or decrease in BP have on diameter of cerebral arteries? (p.6)
- 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.
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Review metabolic factors and pressure changes that affect brain’s ability to auto-regulate. (p.7)
- Increased PaCO2
- 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
- Decreased PaO2
- PaO2 <60 or O2 Sat <90 --> hyperemic flow state
- Head injuries
- 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
- Intracranial bleeds – 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
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Review metabolic factors and pressure changes that affect brain’s ability to auto-regulate. (p.7)
- Use of cerebral vasodilatory drugs
- Halothane
- Nitrous oxide
- Histamines
- Ketamines
- Anti-hypertensives like Nipride
Change in MAP
Prolonged ICP > 35mmHg lasting longer than 20-30 minutes
Changes in CPP
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Know how to calculate MAP. (p.8)
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Know how to calculate CPP. (p.8)
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What is CPP (cerebral perfusion pressure)? (p.8)
- 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
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