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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?

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
Post-ischemic ______________ may promote free radical formation and oxidative stress.
Lactic acidosis
26
10 minutes of complete ischemia can increase ________ by 500%.
Lactate
27
After 2 hours of focal ischemia, lactate can increase by \>1000% and by 500-700% within the \_\_\_\_\_\_\_\_\_.
Penumbra
28
(T/F) Lactate elevations are increased by hypoglycemia.
False. **Elevations in lactate** are increased by **HYPERglycemia**.
29
Describe neuroprotection as a combination therapy?
Drugs that **target Ca2+ influx**, **Na+ influx**, **Glutamate efflux**, and **free radical generation** would avoid cell death.
30
What is the most common cause of death in people \<45 years of age?
Trauma
31
True/False: Severe head injury is associated with a 35% mortality rate.
True.
32
What are the features of **epidural hematoma**?
* 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
What are the features of **subdural hematoma**?
* 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
When is surgical evacuation indicated in a **subdural hematoma**?
If there is **mass effect** or **midline shift**.
35
80% of patients with severe head injury develop what?
Seizures
36
(T/F) Ongoing seizure activity may further compromise neurons.
True.
37
What are the products of **prolonged seizure activity**?
* 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
What results in cerebral edema or swelling?
**Cerebral injury** results in bleeding, vascular injury, cell death and lysis, and alterations in cerebral metabolism that result in edema.
39
How is edema a "vicious cycle"?
Edema results in **increased intracranial pressure** causing a **decrease** in **cerebral** **perfusion** leading to **more ischemic injury**.
40
How is Cerebral Perfusion Pressure calculated?
CPP = MAP - ICP * MAP = mean arterial pressure * ICP = Intracranial pressure
41
What are the goals of therapy regarding cerebral perfusion therapy?
Keep ICP \< 20 mmHg Maintain CPP \> 70 mmHg
42
ICP \> ____ and CPP \< ____ are associated with a high morbidity and mortality rate.
* ICP \> 25 mmHg * CPP \< 50 mmHg
43
How is increased ICP treated?
* 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
Why is hyperventilation an effective treatment for increased intracranial pressure?
As pCO2 is lowered, **vasoconstriction decreases** diastolic blood flow and **lowers ICP**.
45
Why is it important to only use modest hyperventilation to treat increased ICP?
**Excessive hyperventilation** will result in **excessive vasoconstriction** and thus result in **decreased CBF**.
46
What happens when intracranial pressure reaches a critical point?
* 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
Describe the neurological exam assessment of **brain death**.
* **Absent Brainstem Reflexes**: * Pupillary light reflex * Corneal reflex * Oculocephalic reflex * Oculovestibular reflex * Gag reflex * **Apnea** * **Flaccid limbs**
48
What are the **confimatory tests** for brain death?
**Negative CBF** Studies: * Angiography * Radioisotope CBF study * TCD (transcranial doppler) **EEG** (electrocerebral silence)
49
What abnormality is shown in the following picture?
* **Chronic subdural hematomas** * Common in **alcoholics**
50
What abnormality is shown in the following picture?
* **Diffuse axonal injury** (**DAI**) * Common with **severe injuries** * Often involves **brainstem** and **corpus callosum**
51
What abnormality is shown in the following picture?
* **Epidural hematoma** * Associated with **skull fracture** * Causes **convex (lens) shape** * Usually caused by **tearing** of the **middle meningeal artery**
52
What abnormality is shown in the following picture?
* **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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