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BB Test 4 > Traumatic Brain Injury > Flashcards

Traumatic Brain Injury Flashcards

1
Q

Brain mass is what % of body weight?

A

2%

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2
Q

Cerebral blood flow is what % of cardiac output?

A

15%

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3
Q

What is the normal volume of cerebral blood flow?

A

750 ml/min

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4
Q

Describe O2 consumption by the brain as a % of total body available O2.

A

20% of total body available O2

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5
Q

Brain requires _________ for energy metabolism.

A

Glucose

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6
Q

Describe how glucose enters the brain.

A

Via non-energy dependent carrier-mediated transport across the blood-brain barrier.

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7
Q

__________ is necessary to oxidize glucose to _____ and _____, and _____ is produced via oxidative phosphorylation.

A
  • Oxygen is necessart to oxidize Glucose →
  • CO2 and H2O
  • ATP is produced via oxidative phosporylation
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8
Q

Besides glucose, what is the alternative energy source for the brain?

A
  • The brain can utilize ketones during starvation to produce 60-70% of the ATP requirement.
    • The remainder has to come from glucose via gluconeogenesis.
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9
Q

What causes “complete” or “global” cerebral ischemia?

A

Cardiac arrest

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10
Q

What causes “partial” cerebral ischemia?

A

Severe hypotension

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11
Q

What causes “focal” cerebral ischemia?

A

Embolic occlusion of a single cerebral artery.

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12
Q

What is the zone of injury surrounding an area of complete infarction called?

A

Penumbra

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13
Q

What are the characteristics of penumbra?

A
  • Partial ischemia and reperfusion
  • Delayed cell death vs. viability with or without altered cellular structure or function
  • Secondary damage due to inflammation
  • Potentially pharmacologically salvageable.
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14
Q

In neuronal injury (i.e. ischemia), sustained deenergization results in intracellular accumulation of what?

A
  • Na+
  • Ca2+
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15
Q

Intracellular accumulation of Ca<strong>2+</strong> leads to what?

A

Ca2+ mediated glutamate release (i.e. glutamate transporter is reversed, glutamate is released from cell to extracellular)

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16
Q

Increased extracellular glutamate results in what?

A

Increased cellular excitation and seizure activity

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17
Q

How is neuronal injury and glutamate a “vicious cycle”?

A

Glutamate excitotoxicity results in further Na+ and Ca2+ influx, and thus additional energy failure and cellular compromise.

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18
Q

Sustained deenergization (past neuronal injury) leads to what?

A

Necrotic cell death

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19
Q

What are the features of necrotic cell death?

A
  • Prolonged elevation of intracellular Ca2+ and Na+
  • Early loss of membrane integrity
  • Cellular swelling
  • Lysosomal rupture
  • Cell death within a few hours
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20
Q

What is the “pathway” from ischemia to necrotic cell death?

A
  1. Ischemia
  2. Respiratory inhibition
  3. ATP depletion
  4. Glutamate release/Calcium influx
  5. Elevated cytosolic calcium
  6. Damage from phospholipases/proteases
  7. Membrane disruption
  8. Necrotic cell death
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21
Q

Postischemic mitochondrial Ca2+ accumulation and oxidative stress result in a number of mitochondrial alterations that trigger a cascade of events resulting in what?

A

Apoptosis

22
Q

What are the major (general) features of programmed cell death?

A
  • Release of “apoptotic factors”
  • Disturbances in mitochondrial gene expression resulting in delayed metabolic failure.
23
Q

Ischemia/reperfusion results in the increased generation of what?

A

Free radicals

24
Q

What is the danger of free radicals produced by ischemia/reperfusion?

A
  • They damage lipids, proteins, and nucleic acids
  • They may inactivate key enzymes involved in catabolic and anabolic pathways
25
Q

Post-ischemic ______________ may promote free radical formation and oxidative stress.

A

Lactic acidosis

26
Q

10 minutes of complete ischemia can increase ________ by 500%.

A

Lactate

27
Q

After 2 hours of focal ischemia, lactate can increase by >1000% and by 500-700% within the _________.

A

Penumbra

28
Q

(T/F) Lactate elevations are increased by hypoglycemia.

A

False. Elevations in lactate are increased by HYPERglycemia.

29
Q

Describe neuroprotection as a combination therapy?

A

Drugs that target Ca2+ influx, Na+ influx, Glutamate efflux, and free radical generation would avoid cell death.

30
Q

What is the most common cause of death in people <45 years of age?

A

Trauma

31
Q

True/False: Severe head injury is associated with a 35% mortality rate.

A

True.

32
Q

What are the features of epidural hematoma?

A
  • The hematoma is external to the dura mater
  • Often associated with skull fracture
  • Fracture of the temporal bone and tearing of the middle meningeal artery results in a rapidly expanding hematoma
  • Emergency surgical evacuation is indicated.
33
Q

What are the features of subdural hematoma?

A
  • Layer of blood between the dura mater and arachnoid
  • Results from tearing of bridging veins
  • Common with deceleration or shaking injuries
  • Common in the elderly
34
Q

When is surgical evacuation indicated in a subdural hematoma?

A

If there is mass effect or midline shift.

35
Q

80% of patients with severe head injury develop what?

A

Seizures

36
Q

(T/F) Ongoing seizure activity may further compromise neurons.

A

True.

37
Q

What are the products of prolonged seizure activity?

A
  • Prolonged neuronal depolarization
  • Increased intracellular Na+ and Ca2+
  • Glutamate release
  • Oxidative failure and ATP depletion (sound familiar? same features as ischemia)
  • Cytoskeletal degeneration
  • Microtubule dysfunction
  • Protein aggregation
  • Clustering of procaspases promoting activating of caspases
  • Impairment of neuronal viability
38
Q

What results in cerebral edema or swelling?

A

Cerebral injury results in bleeding, vascular injury, cell death and lysis, and alterations in cerebral metabolism that result in edema.

39
Q

How is edema a “vicious cycle”?

A

Edema results in increased intracranial pressure causing a decrease in cerebral perfusion leading to more ischemic injury.

40
Q

How is Cerebral Perfusion Pressure calculated?

A

CPP = MAP - ICP

  • MAP = mean arterial pressure
  • ICP = Intracranial pressure
41
Q

What are the goals of therapy regarding cerebral perfusion therapy?

A

Keep ICP < 20 mmHg

Maintain CPP > 70 mmHg

42
Q

ICP > ____ and CPP < ____ are associated with a high morbidity and mortality rate.

A
  • ICP > 25 mmHg
  • CPP < 50 mmHg
43
Q

How is increased ICP treated?

A
  • Sedation and pharmacologic paralysis
  • Intubation and mechanical ventilation with modest hyperventilation
  • Maintenance of blood pressure
  • Osmotic diuretics (mannitol)
  • Barbituate coma to decrease cerebral metabolism
44
Q

Why is hyperventilation an effective treatment for increased intracranial pressure?

A

As pCO2 is lowered, vasoconstriction decreases diastolic blood flow and lowers ICP.

45
Q

Why is it important to only use modest hyperventilation to treat increased ICP?

A

Excessive hyperventilation will result in excessive vasoconstriction and thus result in decreased CBF.

46
Q

What happens when intracranial pressure reaches a critical point?

A
  • There is downward herniation of the cerebral peduncles through the tentorium cerebelli
  • Brainstem compression and loss of cerebral blood flow result in irreversible brain death.
47
Q

Describe the neurological exam assessment of brain death.

A
  • Absent Brainstem Reflexes:
    • Pupillary light reflex
    • Corneal reflex
    • Oculocephalic reflex
    • Oculovestibular reflex
    • Gag reflex
  • Apnea
  • Flaccid limbs
48
Q

What are the confimatory tests for brain death?

A

Negative CBF Studies:

  • Angiography
  • Radioisotope CBF study
  • TCD (transcranial doppler)

EEG (electrocerebral silence)

49
Q

What abnormality is shown in the following picture?

A
  • Chronic subdural hematomas
  • Common in alcoholics
50
Q

What abnormality is shown in the following picture?

A
  • Diffuse axonal injury (DAI)
  • Common with severe injuries
  • Often involves brainstem and corpus callosum
51
Q

What abnormality is shown in the following picture?

A
  • Epidural hematoma
  • Associated with skull fracture
  • Causes convex (lens) shape
  • Usually caused by tearing of the middle meningeal artery
52
Q

What abnormality is shown in the following picture?

A
  • Subdural hematoma
  • Common with deceleration or shaking injuries
  • Results from tearing of bridging veins
  • Causes concave (crescent) shape
  • Common in elderly

BB Test 4 (14 decks)

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