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I & M > Monitoring ICP and Neurologic Status > Flashcards

Monitoring ICP and Neurologic Status Flashcards

1
Q

What are normal ICP values?

A

1 - 15 mmHg

2 - 20 cmH2O

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2
Q

What are the intracranial contents with associated volumes? (4)

A

Brain parenchyma (actual brain tissue): 1.2 - 1.6 L

ECF: 100 - 150 mL

Blood: 100 - 150 mL

CSF: 100 - 150 mL

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3
Q

What is a late sign of increased intracranial pressure in an infant?

A

Setting-sun sign (rim of sclera above the irises from CN 3, 4, 6 compression)

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4
Q

Identify the heriations:

A
  1. Herniation of cingulate gyrus under the falx
  2. Transtentorial herniation of temporal lobe
  3. Cerebellar tonsils through foramen
  4. Transcalvarial heriation

Need to keep pressures down except for (4) unless brain protrudes out and acts like a bung keeping pressures high.

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5
Q

What factors will increase ICP? (3)

A

Increased intrathoracic pressure (valsalva)

Increased PaCO2

Decreased PaO2

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6
Q

What factors will cause cerebral vasodilation resulting in increased ICP? (3)

A
  • Increased PaCO2
  • Decreased HCO3
  • Increased metabolic acid (lactic, pyruvic)

Note: These factors will decrease pH → vasodilation → increased ICP.

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7
Q

What is depicted?

Explain the points on the curve.

A

Compliance within the cranial vault

The pressure-volume curve can compensate to a point.

1 → 2: Shifts fluid into the spinal space.
3: No longer to compensate and ICP begins to increase.

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8
Q

What is this curve telling us?

What is the x-axis?

A

A real compliance curve rises very quickly due to being within a rigid space. A skull is not truly rigid. Thus, a slowly growing mass lesion would be indicated by the rightmost curve.

X-axis: “Volume of growing mass”

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9
Q

If within cranial vault limits, small changes in volume will result in _____ changes in pressure.

If cranial vault limits are met, what happens to small changes in volume?

A

small

exponential increase in pressures seen

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10
Q

What percent of total body oxygen consumption does the brain receive?

What percent of CO does cerebral blood flow receive?

A

20%

15%

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11
Q

What’s depicted?

What is it used for?

What frequency is used?

A

Transcranial Doppler

Detect cerebral blood flow

2 MHz probes

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12
Q

What is transcranial doppler CBFV?

PI?

A

Cerebral blood flow velocity

Pulsatility index

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13
Q

Transcranial doppler measures the flow of what artery?

A

Middle cerebral artery

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14
Q

What is important to note on this image? (4)

A
  • Transcranial doppler image looks like an arterial waveform
  • Middle cerebral artery monitoring
  • 50 mm depth
  • 2 Hz
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15
Q

What is depicted?

Label.

A

Cerebral blood flow autoregulation curve

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16
Q

At what perfusion pressures does augoregulation occur?

How do you calculate perfusion pressure?

A

50 - 150 mmHg

MAP - ICP (or CVP)

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17
Q

What occurs when perfusion pressure falls below 50 mmHg?

A

Vessel dilation to increase blood flow, thus increased ICP to increase O2 content to brain

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18
Q

Normocapnia (paCO2) occurs at _____ mmHg.

What occurs as paCO2 increases?

What occurs as paCO2 decreases?

A

40

Blood flow increases thus ICP increases

Blood flow decreases thus ICP decreases (hyperventilation)

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19
Q

What occurs to pts with chronic untreated HTN regarding autoregulation of cerebral blood flow?

A

Rightward shift in autoregulatory curve

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20
Q

Label the curves:

A

Black: Cerebral blood flow

Gray: ICP curve (note the spike increase as vasodilation occurs)

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21
Q

Label the curves:

What does the dashed curve represent?

A

The dashed “absent” curve indicates when CBF varies in proportion to cerebral perfusion pressure.

This absent curve occurs under anesthesia (a linear response).

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22
Q

Label the curves:

A

There is a dose-dependent depression of cerebral autoregulation by the volatile anesthetics.

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23
Q

When paCO2 = 30mmHg, how much is CBF decreased (%)?

When paCO2 = 20 mmHg, how much is CBF decreased?

A

25%

50%

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24
Q

With prolonged hyperventilation, CBF returns to normal over a period of ___-___ hours.

A

8 - 12

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25
Q

In awake humans, hyperventilation initially reduces CBF, but after ____ hours of sustained hyperventilation, CBF returns almost to baseline.

A

4

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26
Q

There are cardiac and respiratory affects on ICP, but are considered negligible since ICP is generally represented only by its mean pressure. True or false?

27
Q

Label:

A

Low pressure wave, compliant cranium

High pressure wave, noncompliant cranium (right)

Poorly compliant cranium (bottom)

28
Q

What is depicted?

A

ICP “A” waves

It means that the pt. is not able to recover well from increased pressures. Hyperventilation/osmotics will not help this situation. Only a drain or surgery will correct.

Note: VFP is ventricular fluid pressure. The A waves are accompanied by increases in CBV.

29
Q

Label:

A

ICP “A” and “B” waves

Note: More commonly see B waves.

30
Q

What does the ECG illustrate besides the appearance of cardiac ischemia?

What is the cause of ECG changes?

What lab results do you expect if it is not cardiac ischemia?

A

Increased ICP from subarachnoid hemorrhage perhaps.

Increased norepi levels and increased sympathetic nerve activity

No change in creatine kinase isoenzymes

31
Q

What Ca channel blocker greatly increase ICP?

What Ca channel blocker does not?

A

Nicardipine

Nimodipine has NO effect on ICP.

32
Q

What NMB drugs increases ICP?

A

Sux, so give defasciculating dose of Roc to prevent such increase in ICP.

Others cause no change in ICP.

33
Q

What vasodilators increase ICP? (3)

A

SNP
Hydralazine
NTG

34
Q

What drugs decrease ICP? (7)

A

Propofol
Etomidate
Lidocaine
Mannitol
Furosemide
Benzos (slight)
Barbiturates (not really used anymore)

35
Q

What effect do beta blockers have on ICP?

36
Q

What effect does nitrous have on ICP?

A

slightly increases

37
Q

What volatile agents increase ICP? (3)

A

Desflurane (++)
Sevoflurane (++)
Halothane (++)
Isoflurane (+) is agent of choice in neuro.

Note: N2O increases ICP (+)

38
Q

How does ketamine affect ICP?

Opioids?

A

increases (++)

negligible change

39
Q

What anesthetic agents decrease CBF? (5)

(Place in order of greatest to least.)

A

Propofol
Barbiturates
Etomidate
Lidocaine
Benzodiazipines

40
Q

How do volatile agents affect cerebral metabolic rate?

A

All decrease significantly except N2O.

41
Q

How does propofol and etomidate affect CMR?

A

decreases significantly

42
Q

What effect does ketamine have on CMR?

What effect do opioids have on CMR?

A

negligible

negligible

43
Q

What effect does lidocaine have on CMR?

What effect do benzos have on CMR?

A

Decreases , but less than propofol

Same decrease as lidocaine.

44
Q

For accuracy, where should MAP be measured for CPP calculations?

A

external auditory meatus

45
Q

When can we use CVP values instead of ICP?

A

If CVP higher than ICP, CVP measured at the level of the external auditory meatus may be used in place of ICP.

46
Q

Label:

A

MAP = 150 mmHg (top)
MAP = 100 (right)
MAP = 50 (bottom)

As perfusion pressure declines, the response of the cerebral vasculature to carbon dioxide is attenuated (weakened).

Sigmoid response diminishes

47
Q

What drug can you give while the Mayfield is being applied to a neuro patient?

A

Esmolol, to prevent the transient increase in ICP.

48
Q

Where should the transducer be positioned for correct CPP determination?

A

at the level of the ear

49
Q

What are ways to decrease intracranial pressure? (6)

A
  • Elevate the head to improve cerebral venous outflow
  • Hyperventilation
  • CSF drainage
  • Osmotic and other diuretic drugs
  • Administration of drugs like propofol, barbs
  • Avoid cerebral vasodilating drugs like volatile agents
50
Q

At what level does the Accudrain (a CSF draining device) need to be?

A

Keep 20cm above the level of the ear.

51
Q

With patients in the sitting position, what is likely to occur?

What can correct this problem?

A

Venous air embolism, since when vessels are exposed to the atmosphere, air will enter. The veins will not collapse like peripheral veins since they adhere to the cranial walls.

Mulit-lumen CV catheter into the right atrium

52
Q

What size emboli will cause a significant change on the pt’s cardiovascular signs?

53
Q

What changes will occur where the pt has an air embolism?

A

CO2 falls rapidly

PA pressures increase

Note: Air embolism is best detected by a transesophageal doppler.

54
Q

Which methods are the most sensitive at detecting air embolism when there is:

no physiological changes
modest physiological changes
clinically apparent changes
cardiovascular collapse

A

No changes: Transesophageal echo, Doppler

Modest changes : Pulmonary pressure , EtCO2

Clinically apparent: CO, CVP

CV collapse: BP, ECG, Stethoscope

55
Q

What examination is used to evaluate the neuro status of brain injury patients?

A pt with no neurological function is assigned ____.

A normal patient is assigned ______.

A

Glasgow Coma Scale (GCS)

3

15

56
Q

What does the FOUR Score assess?

A

Eye opening
Motor response
Brainstem reflexes (pupil, corneal reflexes)
Respiration

57
Q

What is the gold standard for monitoring intracranial pressure?

What are the downsides?

A

Intraventricular

Highest infection rate
Risk of hemorrhage

58
Q

What ICP monitor does not allow recalibration after placement, but risk of infection and hemorrhage rate is low?

A

Intraparenchymal

59
Q

What ICP monitor has a lower risk of infection and hemorrhage than intraventricular and intraparenchymal methods?

A

Subarachnoid/epidural

60
Q

What is depicted?

A

Subdural bolt

61
Q

What ICP monitoring catheter utilizes dual fiber optic light fibers and a moving diaphragm that reflects light to calculate pressure?

A

Camino fiberoptic transducer

62
Q

What is HHH therapy for managing pts with intracranial aneurysms?

A

Hypervolemia
HTN
Hemodilution

63
Q

What is cerebral oxygen consumption?

A

3.5 ml/100g/min

50 ml/min

I & M (37 decks)

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