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I&M for Anesthesia - Fall 2013 > EEG and ICP > Flashcards

EEG and ICP Flashcards

0
Q

What is normal cerebral blood flow? How much O2 does this deliver?

A

50 ml/min/100g tissue

Delivers 150 ml O2/min

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1
Q

What is the energy requirement of the brain?

A

3-5 ml O2/min/100g tissue

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2
Q

How much O2 does the brain extract?

A

35-50%

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3
Q

What is the equation of cerebral perfusion pressure?

A

CPP = MAP - ICP

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4
Q

Cerebral blood flow is impaired

A

Post trauma

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5
Q

Auto regulation of cerebral blood flow

A

Increases at the lower limit

Graph - as MAP increases, so does CBF… But plateaus in the middle…?

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6
Q

CBF is reduced by

A 
Head injury
Intracranial hypertension
Hypotension
Vasospasm
Hyperventilation
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7
Q

Intracranial pressure can be directly monitored by

A

Subdural/subarachnoid bolts
Epidural transducers
Intraparenchymal fiber optic devices
Ventricular catheters

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8
Q

What is the Monroe-Kellie hypothesis?

A

The skull is a fixed volume and changes in one unit is balanced by the others.

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9
Q

What are the three components of the Monroe-Kellie hypothesis?

A

Blood, brain, cerebral spinal fluid

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10
Q

What are the percentages of the units that make up ICP?

A

Brain mass - 80%
Blood flow - 10%
CSF - 10%

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11
Q

T or F. ICP monitoring does not require a watertight fluid interface?

A

False

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12
Q

How is brain activity converted to a waveform?

A

Deformation of transducer membrane
Converted to electrical pulsations
Amplified
Displayed as a waveform

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13
Q

T or F. Catheter tip transducers need to be zeroed prior to insertion.

A

True

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14
Q

External transducers are zeroed

A

Anytime

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15
Q

Monitoring ICP is important in

A 
Head injury
Poor grade subarachnoid hemorrhage
Intracerebral hematoma
Meningitis
Stroke
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16
Q

What are normal ICP values? Abnormal?

A

Normal: 7-15 mmHg
Abnormal: >20 mmHg

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17
Q

Aggressive management of ICP is indicated at what value?

A

> 25 mmHg

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18
Q

Elevated ICP causes

A

Herniation of internal and external brain
Distortion of cranial nerves and vital neurological centers
Impeded cerebral perfusion
Loss of CSF
Reduced venous blood flow

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19
Q

What are the pros of intraventricular drain and transducer?

A

Gold standard
ICP control by CSF draining
External zeroing

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20
Q

What are the cons of intraventricular drain and transducer?

A

Bleeding
Blockage
Infection

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21
Q

What is the correct placement of intraventricular catheters?

A

Lateral ventricle (frontal horn)

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22
Q

What is the position of the transducer?

A

Level with the meatus of the ear

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23
Q

What are the pros of the intraparenchymal pressure monitor?

A

Less infection risk
Less risk of hemorrhage
Excellent metro logical properties (less drift)

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24
Q

What are the cons of the intraparenchymal pressure monitor?

A

Underestimates very high ICP

Drift becomes a problem after several days

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25
Q

What are contraindications for using intraparenchymal pressure monitoring?

A

Intracranial infections
Coagulopathies
Severe skull fracture
CSF drainage necessary

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26
Q

What are the three phases of ICP waveforms?

A

P1: percussion wave (arterial pulsations)
P2: rebound wave (intracranial compliance)
P3: dichrotic wave (venous pulsations)

27
Q

How is ICP managed?

A

Decrease brain water

Reduce CSF volume

28
Q

What are ways to decrease brain water?

A

Hyperosmolar diuretics: mannitol w/ intact BBB
Loop diuretics: Lasix
Corticosteroids

29
Q

What is the dosage of mannitol?

A

.25-1g per kg

30
Q

CSF can be reduced from drainage by

A

Ventricular
Lumbar subarachnoid
Head elevation

31
Q

Auto regulation is impaired by

A

Inhaled anesthetics

Direct acting vasodilators

32
Q

What are examples of direct acting vasodilators?

A 
Adenosine
Prostacyclin
Calcium channel blockers
Nitroglycerin
Nitroprusside
33
Q

Transcranial Doppler Ultrasonography

A

Continuous or intermittent monitoring of CBF velocity

34
Q

What is Transcranial Doppler Ultrasonography most useful for?

A

Vasospasm post subarachnoid hemorrhage

35
Q

Does vasospasm cause increased or decreased CBF velocity?

A

Increased (due to Posseiulle’s Law)

36
Q

For TCD, what allows for monitoring independent of rising ICP?

A

ICA:MCA flow

Ratio of internal carotid artery to middle cerebral artery flow

37
Q

What is electroencephalogram monitoring?

A

Summation and recording of postsynaptic potentials from the pyramidal cells of the cerebral cortex

Reflects the metabolic activity of the brain

38
Q

EEG was first used by

A

Hans Berger in 1924

39
Q

A tracing of voltage fluctuations versus time recorded from electrodes placed over scalp in a specific array

A

EEG

40
Q

EEG

A

Represents fluctuating dendritic potentials from superficial cortical layers

Required amplification

41
Q

Part of the brain not sampled well by EEG

A

Deep parts of the brain

42
Q

International 10-20 system of electrode placement

A

Electrodes spaces at ten or twenty percent of distances between specified anatomical landmarks

43
Q

More than 21 electrodes can be added on an EEG to

A

Increase spatial resolution

Record from specific areas

Monitor electrical activity

44
Q

Odd electrodes are placed

Even electrodes are placed

A

On the left

On the right hemisphere

45
Q

Disadvantages of EEG

A

Detects cortical dysfunction, but not etiology
Low sensitivity and low specificity
Subject to electrical and physiologic artifacts
Influenced by alertness, hypoglycemia, and drugs
Small or deep lesions might not produce EEG abnormality
Limited time sampling and spatial sampling

46
Q

Indications for EEG

A

Craniotomy for cerebral aneurysm clipping when a temporary clip is used
Carotid endarterectomy under GA
Cardiopulmonary bypass
Extra cranial intracranial bypass
Pharmacological depression of brain for “cerebral protection”

47
Q

Beta waves

A

13-30 Hz

Awake and alert

48
Q

Alpha waves

A

8-13 Hz

Closed eyes, relaxed

49
Q

Theta waves

A

4-7 Hz

Young children

Drowsiness in older children or adults

50
Q

Delta waves

A

0-4 Hz

Deep sleep, deep sedation

51
Q

Suppression event

A

Very deep sedation, hypothermia, and ischemia

52
Q

EEG artifact

A 
Eye induced - blinks, movement, extra ocular muscle activity
Gloss kinetic artifacts
Poor grounding
IV drips
Body movement
EKG artifact
53
Q

Relaxation with eyes closed

A

Alpha waves predominance

54
Q

Light anesthesia

A

Increase in beta

Decrease in alpha

55
Q

Deepening of anesthesia

A

Increase in slow wave activity, delta 5 and theta 8

56
Q

Cortical silence

A

Burst suppression

57
Q

EEG is not

A

An output of the spinal cord or predictor of movement

58
Q

Activation

A

High frequency
Low voltage
Light anesthesia
Surgical stimulation

59
Q

Depression

A

Low frequency
High voltage
Deep anesthesia
Cerebral compromise

60
Q

Most anesthetics produce

A

A biphasic pattern… Initial activation… Followed by dose dependent depression

61
Q

Agents that activate EEG

A 
Sub anesthetic inhalationals
Low dose barbs and benzos
Small doses of etomidate
N2O
Ketamine
62
Q

Agents that depress EEG

A

1-2 MAC gases
Barbs/propofol/etomidate
Narcotics - dose dependent

63
Q

Other things that influence - activate

A

Mild hypercapnia
Surgical stimulation
Early hypoxia

64
Q

Other things that depress

A

Hypocapnia
Hypothermia
Late hypoxia

I&M for Anesthesia - Fall 2013 (13 decks)

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