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RVT Review > Chapter 20 > Flashcards

Chapter 20 Flashcards

1
Q

what are capabilities for transcranial doppler TCD?

A

detect intracranial stenoses, occlusions, and assess collateral circulation
evaluate onset, severity and time course of vasoconstriction from subarachnoid hemorrhage
evaluate intracranial AVMs
assess patients with suspected brain death

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2
Q

what are limitations for TCD?

A

recent eye surgery may eliminate transorbital approach
adequate penetration of temporal bone from hyperostosis
inaccurate vessel id with nonimaging techn

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3
Q

what is patient positioning for TCDs?

A

patient supine and avoids speaking during exam

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4
Q

what are the 3 acoustic windows for TCDs?

A

transtemporal, transorbital and transforaminal/suboccipital

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5
Q

what frq pulsed doppler used?

A

2MHz

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6
Q

what angle of insonation is assumed

A

zero

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7
Q

what does accurate vessel id reguires?

A
  • depth of sample volume
  • velocity of the blood flow
  • direction of the blood flow
  • relationship of flow patterns to one another
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8
Q

how is TCDs measured?

A

time average max velocity (TAMV) or mean velocity

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9
Q

which vessels can you evaluate with the transtemporal approach?

A

MCA, ACA, PCA, terminal ICA

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10
Q

with the transorbital approach what vessel do you identify?

A

ophthalmic artery and carotid siphon

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11
Q

what approach would you use to evaluate the vertebral and basilar arteries?

A

transforaminal / suboccipital / transocciptal

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12
Q

what is the depth used for a MCA?

A

30-60mm

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13
Q

what is the depth used for terminal ICA?

A

55-65mm

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14
Q

what is the depth for ACA

A

60-80mm

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15
Q

what is the depth for PCA?

A

60-70mm

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16
Q

what is the depth for ICA at siphon?

A

60-80mm

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17
Q

what is the depth for ophthamlic?

A

40-60mm

18
Q

what is the depth for vertebral

A

60-90mm

19
Q

what is the depth for BA?

A

80-120mm

20
Q

what is the direction, velocity, and angle for MCA?

A

antegrade, 55cm/s, anterior and superior

21
Q

what is the direction, velocity, and angle for terminal ICA?

A

bi-directional, 55cm/s, anterior and superior

22
Q

what is the direction, velocity, and angle for ACA?

A

retrograde, 50 cms/s, anterior and superior

23
Q

what is the direction, velocity, and angle for PCA?

A

antegrade, 39cm/s, posterior

24
Q

what is the direction, velocity, and angle for ICA at siphon

A

paraseller-antegrade
supraclinoid-retrograde
genu-both directions

47cm/s
varies with angle

25
Q

what is the direction, velocity, and angle for ophth

A

antegrade, 21cm/, medial

26
Q

what is the direction, velocity, and angle for VA?

A

retrograde, 38cm/s, right and left of midline

27
Q

what is the direction, velocity, and angle for BA

A

retrograde, 41cm/s, midline

28
Q

what is flow chara based on?

A 
direction 
velocity
turbulance 
pulsatlity 
systolic upstroke
29
Q

what are the 3 collateral pathways?

A

cross over
external to internal
posterior to anterior

30
Q

what is the cross over collateral?

A

antegrade flow in ACA from cross-over collateraliztion

e.g flow from contralateral ACA via Acomm

31
Q

what is the external to internal collateral?

A

retrograde flow in ophthalmic artery

32
Q

what is the posterior to anterior collateral?

A

increased flow in PCA reversing direction of flow in the PCom artery

33
Q

what are factors that may alter intracranial blood flow?

A

age, sex, hematocrit, blood gases, metabolism

34
Q

where are occlusion most accurate?

A

most accurate in ICA or MCA

35
Q

which vessels do vasospasms happen?

A

most accurate in MCA

36
Q

what is the mean velocity for a vasospasm?

A

> 120cm/s

37
Q

what is the velocity for a severe vasospasm?

A

> 200cm/s

38
Q

what will happen with a AVM?

A

increased systolic and diastolic flow velocities
very low pulsatility indices
reduced flow in adjacent arteries

39
Q

T/F id of flow abnormalities may warrant change in surgical technique e.g carotid endarterectomy or coronary artery bypass grafting

A

true

40
Q

what is the technique for intraoperative monitoring?

A

headset utilized for continuous monitoring

not working in sterile field

41
Q

what is the interpretation for intraoperative monitoring?

A

significant decrease in MCA flow velocities during cross clamping of vessel may indicate need for shunting
audible signal related to micro-emboli may alter surgical technq

RVT Review (30 decks)

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