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[Value of transcranial Doppler sonography]
1Klinik für Anaesthesie und operative Intensivtherapie, Knappschaftskrankenhaus, Ruhr-Universität, Bochum.
Infusionstherapie Und Transfusionsmedizin
|October 1, 1993
Summary
Transcranial Doppler sonography (TCD) noninvasively measures cerebral blood flow velocities. It aids in diagnosing vasospasm, assessing CO2 reactivity, and monitoring during surgery, but requires cautious interpretation of intraoperative findings.
Area of Science:
- Neurology
- Medical Imaging
- Vascular Ultrasound
Background:
- Transcranial Doppler (TCD) sonography, introduced in 1982, noninvasively assesses cerebral blood flow.
- It analyzes ultrasound backscatter from basal cerebral arteries to determine flow velocities and pulsatility index.
Purpose of the Study:
- To review the applications and limitations of TCD in clinical neurovascular assessment.
- To highlight TCD's utility in detecting cerebral vasospasm, evaluating CO2 reactivity, and intraoperative monitoring.
Main Methods:
- Utilizes a 2-MHz ultrasound beam to insonate basal cerebral arteries.
- Employs Fast-Fourier transformation for analyzing backscattered ultrasound to derive flow parameters.
- Correlates changes in flow velocities and pulsatility index with physiological conditions.
Main Results:
- Elevated flow velocities and decreased pulsatility index indicate cerebral vasospasm post-subarachnoid hemorrhage.
- High pulsatility index suggests increased cerebrovascular resistance (e.g., hyperventilation, elevated intracranial pressure).
- TCD effectively monitors changes in cerebral blood flow (CBF) related to CO2 reactivity and during carotid cross-clamping.
Conclusions:
- TCD is valuable for analyzing CO2 reactivity in patients with brain injuries or carotid lesions.
- Intraoperative TCD aids in detecting emboli and guiding interventions like shunt insertion during carotid endarterectomy.
- Caution is advised when interpreting intraoperative TCD due to potential influences from blood pressure, intracranial pressure, and anesthetic agents.