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[Transcranial Doppler sonography and hemodynamics]
W Schregel1, M Sihle-Wissel, A Machraoui
1Abteilung für Anästhesie und operative Intensivtherapie, Knappschafts-Krankenhaus Bochum-Langendreer, Ruhr-Universität Bochum.
Insights
Transcranial Doppler (TCD) monitoring during cardiac catheterization in healthy patients revealed intact cerebral autoregulation, independent of carbon dioxide levels, during exercise-induced physiological changes.
Area of Science:
- Neurosonology
- Cerebrovascular Physiology
- Autoregulation
Context:
- Investigated 13 patients without neurological disease undergoing Swan-Ganz catheterization for cardiologic reasons.
- Utilized transcranial Doppler sonography (TCD) to assess middle cerebral artery blood flow.
- Monitored hemodynamic parameters including mean arterial pressure, heart rate, and cardiac index during exercise.
Purpose:
- To evaluate the functioning of cerebral autoregulation during physiological stress.
- To determine the influence of end-tidal carbon dioxide on cerebral blood flow velocity and pulsatility index.
- To assess the independence of cerebral autoregulation from carbon dioxide fluctuations.
Summary:
- During exercise, significant increases in mean arterial pressure, heart rate, and cardiac index were observed.
- Middle cerebral artery flow velocities increased proportionally to end-tidal carbon dioxide.
- Notably, the pulsatility index significantly increased (p < 0.01), contradicting expected changes due to CO2 accumulation, indicating intact autoregulation.
Impact:
- Demonstrates that cerebral autoregulation remains functional and independent of CO2 levels during acute hemodynamic changes.
- Provides crucial insights for interpreting TCD findings in patients with impaired autoregulation.
- Highlights the importance of considering autoregulation status in TCD-based clinical assessments.
Abstract:
13 patients without cerebral or cerebrovascular diseases were investigated by transcranial Doppler sonography during Swan-Ganz catheterisation for cardiologic purposes. Massive increases of mean arterial pressure, heart rate and cardiac index were observed during exercise; flow velocities in the middle cerebral artery increased only to the same extent as the endexpiratory carbon dioxide rose. However, the pulsatility index increased significantly (p less than 0.01) although a decrease should have been expected due to carbon dioxide accumulation. These results are indicative of a functioning autoregulation independent of carbon dioxide; they are relevant for interpretation of TCD results in patients with disturbed autoregulation.