EEG and ICP Flashcards Preview

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

Flashcards in EEG and ICP Deck (65):
0

What is the energy requirement of the brain?

3-5 ml O2/min/100g tissue

1

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

50 ml/min/100g tissue

Delivers 150 ml O2/min

2

How much O2 does the brain extract?

35-50%

3

What is the equation of cerebral perfusion pressure?

CPP = MAP - ICP

4

Cerebral blood flow is impaired

Post trauma

5

Auto regulation of cerebral blood flow

Increases at the lower limit

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

6

CBF is reduced by

Head injury
Intracranial hypertension
Hypotension
Vasospasm
Hyperventilation

7

Intracranial pressure can be directly monitored by

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

8

What is the Monroe-Kellie hypothesis?

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

9

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

Blood, brain, cerebral spinal fluid

10

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

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

11

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

False

12

How is brain activity converted to a waveform?

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

13

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

True

14

External transducers are zeroed

Anytime

15

Monitoring ICP is important in

Head injury
Poor grade subarachnoid hemorrhage
Intracerebral hematoma
Meningitis
Stroke

16

What are normal ICP values? Abnormal?

Normal: 7-15 mmHg
Abnormal: >20 mmHg

17

Aggressive management of ICP is indicated at what value?

>25 mmHg

18

Elevated ICP causes

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

19

What are the pros of intraventricular drain and transducer?

Gold standard
ICP control by CSF draining
External zeroing

20

What are the cons of intraventricular drain and transducer?

Bleeding
Blockage
Infection

21

What is the correct placement of intraventricular catheters?

Lateral ventricle (frontal horn)

22

What is the position of the transducer?

Level with the meatus of the ear

23

What are the pros of the intraparenchymal pressure monitor?

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

24

What are the cons of the intraparenchymal pressure monitor?

Underestimates very high ICP
Drift becomes a problem after several days

25

What are contraindications for using intraparenchymal pressure monitoring?

Intracranial infections
Coagulopathies
Severe skull fracture
CSF drainage necessary

26

What are the three phases of ICP waveforms?

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

27

How is ICP managed?

Decrease brain water
Reduce CSF volume

28

What are ways to decrease brain water?

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

29

What is the dosage of mannitol?

.25-1g per kg

30

CSF can be reduced from drainage by

Ventricular
Lumbar subarachnoid
Head elevation

31

Auto regulation is impaired by

Inhaled anesthetics
Direct acting vasodilators

32

What are examples of direct acting vasodilators?

Adenosine
Prostacyclin
Calcium channel blockers
Nitroglycerin
Nitroprusside

33

Transcranial Doppler Ultrasonography

Continuous or intermittent monitoring of CBF velocity

34

What is Transcranial Doppler Ultrasonography most useful for?

Vasospasm post subarachnoid hemorrhage

35

Does vasospasm cause increased or decreased CBF velocity?

Increased (due to Posseiulle's Law)

36

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

ICA:MCA flow

Ratio of internal carotid artery to middle cerebral artery flow

37

What is electroencephalogram monitoring?

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

Reflects the metabolic activity of the brain

38

EEG was first used by

Hans Berger in 1924

39

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

EEG

40

EEG

Represents fluctuating dendritic potentials from superficial cortical layers

Required amplification

41

Part of the brain not sampled well by EEG

Deep parts of the brain

42

International 10-20 system of electrode placement

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

43

More than 21 electrodes can be added on an EEG to

Increase spatial resolution

Record from specific areas

Monitor electrical activity

44

Odd electrodes are placed

Even electrodes are placed

On the left

On the right hemisphere

45

Disadvantages of EEG

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

Indications for EEG

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

Beta waves

13-30 Hz

Awake and alert

48

Alpha waves

8-13 Hz

Closed eyes, relaxed

49

Theta waves

4-7 Hz

Young children

Drowsiness in older children or adults

50

Delta waves

0-4 Hz

Deep sleep, deep sedation

51

Suppression event

Very deep sedation, hypothermia, and ischemia

52

EEG artifact

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

53

Relaxation with eyes closed

Alpha waves predominance

54

Light anesthesia

Increase in beta
Decrease in alpha

55

Deepening of anesthesia

Increase in slow wave activity, delta 5 and theta 8

56

Cortical silence

Burst suppression

57

EEG is not

An output of the spinal cord or predictor of movement

58

Activation

High frequency
Low voltage
Light anesthesia
Surgical stimulation

59

Depression

Low frequency
High voltage
Deep anesthesia
Cerebral compromise

60

Most anesthetics produce

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

61

Agents that activate EEG

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

62

Agents that depress EEG

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

63

Other things that influence - activate

Mild hypercapnia
Surgical stimulation
Early hypoxia

64

Other things that depress

Hypocapnia
Hypothermia
Late hypoxia