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Vascular > TCD > Flashcards

TCD Flashcards

1
Q

Transcranial Doppler free hand method uses a

A

2MHz pulse wave Doppler with spectral analysis.

Angle of incination at 0 degrees.

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2
Q

TCD

A

Detects intracranial stenosis and occlusion.

Asses collateral circulation and arteriovenous malformation.

Evaluate onset, severity, and time course of vasoconstriction.

Provide info related to blood flow patterns in patients with sickle cell disease.

Evaluar patients with suspected patent foramen ovale, suspected brain death, suspected intracranial pressure.

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3
Q

Limitations

A

Hyperostosis (thickening or temporal bone) 10% of population

Recent eye surgery may r/o transorbital window.

Operator dependent. Vessel identification.

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4
Q

TCD used for

A

Micro emboli detection for carotid surgery, coronary bypass graft, and stenting.

Cerebral auto regulation- vasoreactivity to Co2

Monitoring of real time blood flow to brain during surgical procedures

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5
Q

Head gear for TCD bilateral monitoring

A

Records bilateral hemispheres, long periods of spectral Doppler info.

Receives signal from middle cerebral arteries

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6
Q

TCD access windows

A

Transorbital
Submandibular
Suboccipital / transforaminal
Transtemporal

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7
Q

Transtemporal

A

Probe placed ant to ear and sup to zygomatic arch in thinnest portion or skull.

Can see:
MCA
ACA 
PCA
TICA (terminal ica)
PcoA and AcoA only if functioning as collaterals

3 areas:
Anterior
Middle (preauricular)
Posterior

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8
Q

Transtemporal window

A

MCA. 3-6cm depth, toward, 55+|-12 cm/sec

MCA/ACA 5.5-6.5cm, bidirectional

ACA (A1) 6-8cm away 50 +|-11 cm/sec

PCA (P1) 6-7cm, towards, 39+|-10 cm/sec

TICA 5.5-6.5cm, towards, 39+|-9 cm/sec

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9
Q

Transforaminal/suboccipital window

A

Transducer placed at concave area at neck/back of head at the foramen magnum.

Rt and left vertebral, 6-9cm depth, away, 38+|-10cm/sec

Basilar 8-12cm depth, away, 41+|-10cm/sec

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10
Q

Transorbital window

A

Transducer placed over closed eyelid.

Carotid siphon can be imaged at specific depths and ranges.

Carotid siphon 6-8cm depth:
•supraclinoid: away, 41+|-11cm/sec
•genu: bidirectional
•parastellar: towards 47+|-14cm/sec

Ophthalmic artery: 4-6cm depth, toward, 21+|-5 cm/sec

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11
Q

Carotid siphon

A

Parastellar
Genu (bend)
Supraclinoid portion (distal)

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12
Q

Submandibular window

A

Under jawline. Evaluates distal extra cranial ICA to provide velocities to get the extra cranial to intracranial ratio.

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13
Q

Transcranial Imaging TCI

Aka

Color coded duplex sonography

A

Bigger transducer. 1.8-2.5MHz. Dec Doppler sensitivity. Higher failure rate than TCD

Visualize location and course of intracranial vessels.

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14
Q

TCI

A

Color, pulses, b mode

MCA not always identified with TCI compared to TCD.

Images vasculature and brain parenchyma

Access windows: transtemporal and suboccipital windows.

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15
Q

Collateral pathways occur through circle of Willis when

A

Proximal pressure drops from stenosis or occlusion of carotid or vertebral arteries.

Little to no flow seen in communicating arteries unless used as collateral pathways.

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16
Q

Cerebral aneurysm

A

Ruptures 28,000 people annually
Mortality rate >50%
Survivors face aneurysm clipping/coiling
At risk for subarachnoid hemorrhage SAH

17
Q

Vasospasm

A

Transient narrowing of intracranial arteries. Occurring and Resolving within 2 weeks of initial bleed.

Complication if subarachnoid hemorrhage related to rupture of an intracranial aneurysm, AV malformation, hypertensive bleed, or head trauma.

1/3 of permanent neurological deficits

Ipsilateral or contralateral to side of aneurysm or bilaterally

May involve any of the major intracranial arteries

If velocities increase in a TCD, patient will most likely be treated urgently to negate the development of neurologic events.

18
Q

Cerebral vasospasm symptoms

A 
Confusion
Dec level of consciousness 
Goofy 
Stroke 
Death
19
Q

Hemispheric ratio aka delindenguard ratio

Vasospasm criteria

A

Degree of vasospasm, Time Avg Mean Vel cm/sec, ratio

  • Normal, <120cm/sec, <3
  • Mild, 120-149, >|= 3
  • Moderate, 150-199, >3
  • Severe, >|=200, >|=6
  • Hyperdynamic flow >|=80, < 3 (secondary to low hematocrit, volume expansion, and HTN)

Rato = TAMV of MCA / ipsilateral distal extra cranial ICA TAMV. Both obtained with submandibular approach TCD.

20
Q

Patent foramen ovale

A

Hole between Rt atrium and Lt atrium. (Incomplete closure of foramen ovale)

TCDs pick up high intensity transient signals (HITS) from agitated saline (contrast agent) in patients with a PFO.

Pt wears headgear to evaluate bilateral MCA. Injected agitated saline into vein, either resting or valsalva maneuver performed. Evaluate for micro bubbles or microemboli, grading criteria based on number of hits.

Emboli shower.

21
Q

Cryptogenic Stroke

A

Stroke of unknown origin. 40%.

Suspicion of paradoxical brain emboli arising from venous circulation.

Emboli from venous system can pass to the arterial circulation through a PFO.

22
Q

Brain death

A

TCD can confirm cerebral circulatory arrest

Correlates well with electro encephalography

4 characteristic stages of brain death:
•inc pulsatility with end diastolic reaching zero
•oscillating flow (reverberatory flow). Forward and reverse flow that are equal.
•narrow, reduced velocity systolic spikes
•no flow signal (can be due to absence of temporal bone window, and requires confirmation by investigating extra cranial carotid and vertebrals. Study performed twice, 30 mins apart.

23
Q

Intraoperative monitoring with TCDs

A

Identifies flow abnormalities during cerebrovascular/ cardiovascular procedures.
(Examples: endarterectomy, carotid stenting, PFO closure, and cardiac surgery)

Continuous monitoring of MCA

24
Q

Cerebral emboli can be

A
  • Air bubbles
  • Particulate matter
  • Microemboli signals MES
  • High intensity transient signals HITS

Emboli shower

25
Q

Flow reversal in ophthalmic artery (away from transducer in TCD) would indicate

A

Stenosis or occlusion in ipsilateral ICA with ECA to ICA collateral flow

Vascular (21 decks)

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