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Periodic variations in transcranial Doppler mean velocities
C A Giller1, M Lam, A Roseland
1Department of Neurosurgery, University of Texas, Southwestern Medical Center at Dallas 75235.
Summary
Serial transcranial Doppler (TCD) measurements reveal significant blood flow velocity variations in normal individuals and neurosurgical patients. These fluctuations, observed over short periods, can impact the accuracy of TCD studies.
Area of Science:
- Neurosonology
- Cerebrovascular Physiology
- Neurosurgical Monitoring
Background:
- Serial transcranial Doppler (TCD) measurements are clinically valuable for assessing blood flow velocity.
- Current clinical practice often assumes TCD signals remain stable during short measurement intervals.
Purpose of the Study:
- To investigate the stability of middle cerebral artery blood flow velocity signals over short durations.
- To determine the extent of velocity variations in both healthy subjects and neurosurgical patients.
Main Methods:
- Continuous transcranial Doppler signals were recorded for 5-10 minutes from the middle cerebral artery.
- Recordings were performed on 11 healthy volunteers and 18 neurosurgical patients (22 studies).
- Peak-to-trough differences within observed waves were quantified.
Main Results:
- Significant variations in mean velocity signals were observed in both normal subjects and patients.
- In normal subjects, the average peak-to-trough difference was 11% ± 4% (SEM); 5/11 showed >20% variation.
- In neurosurgical patients, the average peak-to-trough difference was 14% ± 13% (SEM); 13/22 studies showed >20% variation.
Conclusions:
- Blood flow velocity signals measured by transcranial Doppler are not stable over short periods.
- These inherent signal variations may be linked to fluctuations in blood pressure or intracranial pressure waves.
- Clinicians must acknowledge these variations for accurate interpretation of serial transcranial Doppler studies.