Class 1 Flashcards
What does TCD stand for?
Transcranial Doppler
What is TCD?
It is a non-invasive assessment of the cerebral blood flow in the basal cerebral arteries.
*Most of them will relate to the circle. of wilis*
What is TCD usually used for?
- Baseline
- Stroke patients
- Cerebral deficiency
What type of frequency does a TCD use?
- Low frequency lets you penetrate deeper.
- Skull bone attenuates 90% of your ultrasound beam.
What is the standard probe used for TCD?
2 MHZ probe
Ultrasound passes through many_______
Cranial “windows”
What type of information does TCD provide?
It provides information regarding velocity (mean velocity) and direction of cerebral blood flow.
Who introduced the first ultrasound transtemporal approach?
Dr. Rune Aaslid in 1982
Who first published the transorbital approach?
Dr. Merrill Spencer in 1984
Who first published the suboccipital approach?
Dr. M. Von Reutern in 1986
When was the first commerical TCD unit invented?
1983
What is the circle of wilis?
- It is a network of vessels at the base of the brain that distributes flow to all regions of the RT & LT hemispheres of the brain.
- Primarly from the anterior circulation: ICA supply
- Primarily from the posterior circulation: Vertebral supply
- Most important source of cerebral blood supply and collateral circulation.
Where is the circle of wilis located?
It is located at the base of the brain.
What percentage of people have a complete circle of wilis?
20%
What is the criteria for vessel identifcation?
- Depth of sample volume
- Direction of flow
- Traceability of the vessel
- Transducer angulation
- Spatial relationship of waveform spectra
What direction can the probe only go towards?
Towards the probe.
Usually 50 cm/s
Never reverses.
T/F
Every waveform has its own special type of spectral waveform.
True
What is the landmark for vessels?
MCA
What are some TCD characterisitics?
- Noninvasive
- Painless
- Inexpensive
- Povides instanteous and continuous cerebral blood flow info.
- Can be used in any hospital enviroment
- Safe
What are the main accepted clinical application uses for TCD’s?
TCD applications
-
Detect/monitor intracranial vasospasm
- main use
- Detect/monitor intracranial stenoses
- Confirm the diagnosis of brain death
- Assist in the detection and mangement of ASD
Other used for TCD include:
- Assess of collateral pathways
- Assess autoregulation and vasomotor reactivity
- ICU monitoring (effects of ICP)
- Surgical montitoring (CEA, CABG)
- Detecting of emboli (HITS)
What are some TCD intraoperative monitoring applications?
- Carotid endarectomy
- Carotid stenting
- Coronary artery bypass surgery
- Cardiac valve surgery
- Abdominall aortic aneurysm
- Liver transplants
What are some pitfalls and trouble spots of using TCD?
- Variations and incomplete circle of willis
- e.g. Missing ACA and PCA stemming directly from ICA
- Absent or small windows
- Approx. 90-95% of the population have a temporal window.
- Not identifying/finding best temporal window
- Improper doppler settings
- e.g. too low/too high gain, too large sample volume, low power
T/F
A TCD exam is extremely user dependent.
True.
How should you set up the equipment pior to beginning a TCD exam?
- Wipe down transducer and cable
- Label vessel, adjust depth, power and direction of flow before applying transducer on the patient.
How should you position the patient pior to beginning a TCD exam?
- Exam can be preformed in a supine or sitting position
- DO NOT reposition a patient with a EVD, without nursing assistance
- Know the status of the extracranial vessels.
What window is the MCA in?
Transtemporal