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Relation between middle cerebral artery blood flow velocity and stump pressure during carotid endarterectomy
M P Spencer1, G I Thomas, M A Moehring
1Center for Stroke Research, Seattle, Wash.
Insights
Monitoring middle cerebral artery blood flow velocity changes during carotid endarterectomy is more reliable than stump pressure for detecting cerebral hypoperfusion and guiding shunting decisions.
Area of Science:
- Neurology
- Vascular Surgery
- Medical Monitoring
Background:
- Cerebral hypoperfusion during carotid endarterectomy is a significant concern.
- Various monitoring techniques exist, but their efficacy varies.
Purpose of the Study:
- To compare middle cerebral artery (MCA) blood flow velocities with carotid artery stump pressures.
- To evaluate their utility in indicating the need for shunting during carotid endarterectomy.
- To identify hemodynamic causes of cerebrovascular complications.
Main Methods:
- Transcranial Doppler ultrasound monitored MCA blood flow velocities.
- Carotid stump pressures were measured during common carotid artery cross-clamping in 97 patients.
- Correlation analysis between stump pressures and velocity changes was performed.
Main Results:
- MCA blood flow velocities typically decreased upon common carotid artery cross-clamping.
- Velocity decrease was influenced by collateral circulation and autoregulation.
- An exponential relationship showed zero velocity at 15 mm Hg stump pressure (r=0.85, p<0.001).
Conclusions:
- Percentage changes in MCA blood flow velocity offer a more precise measure than stump pressure.
- MCA velocity monitoring is a reliable parameter for assessing cerebral blood flow effects of carotid cross-clamping.
- This method serves as an excellent indicator for shunting necessity.
Background And Purpose:
Many patient monitoring techniques have been used for detecting cerebral hypoperfusion during carotid endarterectomy. We compared middle cerebral artery blood flow velocities with carotid artery stump pressures to evaluate the indications for common carotid artery cross-clamp shunting and the probable hemodynamic causes of cerebrovascular complications.
Methods:
Blood flow velocities were monitored with transcranial Doppler ultrasound and carotid stump pressures were measured at the time of common carotid artery cross-clamping during 97 carotid endarterectomy procedures. Stump pressures measured with the gauge zero reference at the common carotid artery level were correlated with the percentage change of velocities.
Results:
Middle cerebral artery blood flow velocities usually decreased upon common carotid artery cross-clamping, depending on collateral availability and the autoregulation response. The best fit of the data was to an exponential function concave to the pressure axis, with velocity as a percentage of the pre-cross-clamp value reaching zero at 15 mm Hg stump pressure (r = 0.85 and p less than 0.001).
Conclusions:
There is a less critical margin of error with percentage middle cerebral artery blood flow velocity decreases than with stump pressure measurements. This relation establishes changes in middle cerebral artery blood flow velocities as a reliable parameter for judging the effects of carotid cross-clamping on cerebral blood flow and providing an excellent indicator as to the necessity for shunting.