3.19.14 36 Trauma

Question 1

Brain stats:
% of body weight
% of cardiac output
% of O2 consumption

Answer 1

2%
15%
20%

Question 2

Describe basic cellular metabolism for energy production

Answer 2

O2 + glucose –> CO2 + H2O + ATP (+ lactate)

Question 3

Up to __% of the brain’s energy demands may be satisfied by ketones in times of hypoglycemia.

Answer 3

60-70%

Question 4

How does glucose cross the blood brain barrier?

Answer 4

Non-energy dependent carrier mediated transport

Question 5

What is describes the region surrounding an area of complete infarction that may be salvageable?

Answer 5

Penumbra

Question 6

Name the key players in neuronal injury following ischemic events

Answer 6

1. Increased Na+
2. Increased Ca2+
3. Decreased ATP

Question 7

How is intracellular sodium increased in ischemic events?

Answer 7

Voltage gated sodium channels

Question 8

How is intracellular calcium increased in ischemic events?

Answer 8

Depolarization due to increased Na+ opens voltage gated calcium channels

Question 9

How is the release of glutamate triggered in ischemic events? Why is this important?

Answer 9

Increased calcium –> release of glutamate vesicles

This leads to excitotoxicity (binding of NMDA and AMPA receptors) –> increased excitation and seizure activity

Question 10

What causes the ultimate energy failure in ischemic events?

Answer 10

Excitotoxicity from release of glutamate

Question 11

What are the major cellular processes leading to necrotic cell death?

Answer 11

Loss of energy creates an ionic imbalance, which leads to:
Loss of membrane integrity
Cellular swelling
Lysosomal rupture

Question 12

What is the major event that leads to release of apoptotic factors and eventually apoptosis?

Answer 12

Mitochondrial permeability

Question 13

What is the hallmark of reperfusion injury?

Answer 13

Free radical generation

Question 14

What is the percentage of lactic acid increase following 10 min of complete ischemia?

Answer 14

500%

Question 15

What is the percentage of lactic acid increase following 2 hr of focal ischemia? Within the penumbra?

Answer 15

1000%

500-700%

Question 16

Why would hypothermia be a favorable treatment for ischemic events following use of TPA?

Answer 16

Slow down cerebral metabolism

Allows for recovery and reduced production of free radicals

Question 17

Chronic subdural bleeds are typical of alcoholics because?

Answer 17

Brain atrophy loosens up spaces around the brain, increasing tears of bridging veins

Question 18

Seizures following severe head trauma are more common in _____.
They typically develop within _____ (time frame).

Answer 18

Children

The first week following injury

Question 19

Describe the vicious cycle of cerebral edema

Answer 19

Cerebral injury –> edema –> increased intracranial pressure –> decreased cerebral perfusion –> ischemia –> more injury

Question 20

What is the calculation for cerebral perfusion pressure?

Answer 20

= MAP - ICP

mean arterial pressure, intracranial pressure

Question 21

What is a good cerebral perfusion pressure?

What is a bad cerebral perfusion pressure?

Answer 21

Good: >70mmHg
Bad: <50mmHg

Question 22

What is a good intracranial pressure?

What is a bad intracranial pressure?

Answer 22

Good: 25mmHg

Question 23

What are treatments targeted at lowering intracranial pressure?

Answer 23

Sedation/pharmacological paralysis
Mechanical ventilation (hyper)
Maintenance of blood pressure (diuretics)

Question 24

How does one pharmacologically decrease cerebral metabolism (emergency: increased ICP)?

Answer 24

Barbiturate coma

Question 25

Why is hyperventilation used to treat ICP? What can go wrong with too much hyperventilation?

Answer 25

1. Low CO2 leads to vasoconstriction –> decreased diastolic blood flow
2. Decreased cerebral blood flow

Question 26

What occurs at the critical point of intracranial pressure?

Answer 26

Herniation through the cerebellar tentorium –> brainstem compression and loss of blood flow

Question 27

What are the neurological exam features of brain death?

Answer 27

Absent brainstem reflexes
Apnea
Flaccid limbs

Question 28

What are the confirmatory tests for brain death?

Answer 28

***EEG (electrocerebral silence = diagnostic)

Negative cerebral blood flow studies (angiography, radioisotope, transcranial doppler)