Cerebral Blood Flow and Transcranial Doppler Sonography Measurements of CO 2 -Reactivity in Acute Traumatic Brain Injure
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ORIGINAL ARTICLE
Cerebral Blood Flow and Transcranial Doppler Sonography Measurements of CO2-Reactivity in Acute Traumatic Brain Injured Patients Peter Reinstrup • Erik Ryding • Bogi Asgeirsson • Karin Hesselgard • Johan Unden • Bertil Romner
Ó Springer Science+Business Media, LLC 2012
Abstract Background Cerebral blood flow (CBF) measurements are helpful in managing patients with traumatic brain injury (TBI), and testing the cerebrovascular reactivity to CO2 provides information about injury severity and outcome. The complexity and potential hazard of performing CBF measurements limits routine clinical use. An alternative approach is to measure the CBF velocity using bedside, non-invasive, and transcranial Doppler (TCD) sonography. This study was performed to investigate if TCD is a useful alternative to CBF in patients with severe TBI. Method CBF and TCD flow velocity measurements and cerebrovascular reactivity to hypocapnia were simultaneously evaluated in 27 patients with acute TBI. Measurements were performed preoperatively during controlled normocapnia and hypocapnia in patients scheduled for hematoma evacuation under general anesthesia. Main Finding and Conclusion Although the lack of statistical correlation between the calculated reactivity indices, there was a significant decrease in TCD-mean flow
K. Hesselgard B. Romner Department of Neurosurgery, Lund University Hospital, Lund, Sweden P. Reinstrup B. Asgeirsson J. Unden Department of Neuroanesthesia, Lund University Hospital, Lund, Sweden E. Ryding Department of Neurophysiology, Lund University Hospital, Lund, Sweden P. Reinstrup (&) Department of Neurointensive Care, Lund University Hospital, S 221 85 Lund, Sweden e-mail: [email protected]
velocity and a decrease in CBF with hypocapnia. CBF and TCD do not seem to be directly interchangeable in determining CO2-reactivity in TBI, despite both methods demonstrating deviation in the same direction during hypocapnia. TCD and CBF measurements both provide useful information on cerebrovascular events which, although not interchangeable, may complement each other in clinical scenarios. Keywords Brain trauma CO2 reactivity Traumatic brain injury Cerebral blood flow (CBF) Transcranial Doppler sonography (TCD)
Introduction The cerebral circulation can be compared to a finely tuned instrument, with the primary function of dynamically meeting the ever-changing metabolic demand of the brain. This delicate mechanism is thought to be based on small changes in the milieu surrounding the arteries. The increased metabolism of the brain cells increases the CO2 concentration and thereby reduces the peri-vascular pH resulting in the relaxation of the cerebral vessels [1, 2]. This is the most potent physiological property modulating the tone of the brain vessels and can be measured as the CO2 reactivity by evaluating the cerebral blood flow (CBF) at different arterial pCO2 levels. Changing the pCO2 in the arterial system creates uniform changes in the flow throughout the brain [3]. Normally, the ch
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