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Specialized Circulations in Susceptible Tissues
Published in Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos, McDonald's Blood Flow in Arteries, 2022
Transcranial Doppler has also been used to measure flow waveforms in the cerebral veins and venous sinuses (Valdueza et al., 1996; Baumgartner et al., 1997; Stolz et al., 1999). These venous studies, supplemented more recently by MR studies (Bateman, 2002a; Bateman, 2002b; Bateman, 2003; Henry-Feugeas et al., 2005; Bateman, 2008) in small arteries and capillaries show persistence of pulsatile flow, and with PI (or resistance index) almost comparable to indices in the arterial tree, although the venous flow wave appears delayed compared to that in the arteries upstream (Figure 14.35). Bateman (Bateman, 2002a; Bateman, 2002b; Bateman, 2003) described a PI of 0.72–0.75 in the carotid artery and 0.41–0.47 in cortical veins and superior sagittal sinuses of normal subjects, with higher values (1.09 and 0.49–0.67), respectively, for arteries and veins in persons with dementia. Bateman considered that the high flow pulsations had been transmitted indirectly from artery to vein via extravascular pathways rather than through the capillaries and in the process had caused edema and white matter lesions (we cannot agree with this). In the lung, similar flow patterns are seen, but the relatively high pulmonary vein pulsations are known to have been transmitted directly through the pulmonary capillaries (Milnor et al., 1966). The same must apply within the human skull if the Monro–Kellie doctrine pertains (Mokri, 2001).
Head and Neck
Published in Bobby Krishnachetty, Abdul Syed, Harriet Scott, Applied Anatomy for the FRCA, 2020
Bobby Krishnachetty, Abdul Syed, Harriet Scott
Transcranial doppler Doppler probe is placed on the petrous temporal boneMeasures blood flow through the middle cerebral arteryDetects flow and emboliOperator dependent
Transcranial Doppler Technology: The Noninvasive Monitoring of Cerebral Perfusion During Cardiopulmonary Bypass
Published in Richard A. Jonas, Jane W. Newburger, Joseph J. Volpe, John W. Kirklin, Brain Injury and Pediatric Cardiac Surgery, 2019
The transcranial Doppler technique uses a range-gated, pulsed-wave, direction-sensitive Doppler probe (area= 1.5 cm2), with an emitting power of 100 mW and a resolution of 3 cm/s, to transmit low-frequency sound (1 to 2.5 MHz) through thin areas (windows) of the skull. For the purposes of monitoring cerebral perfusion during CPB, the CBFV is measured via the temporal window in the Ml segment of the middle cerebral artery (MCA), the largest of the basal cerebral arteries and the dominant one with regard to perfusion (70% of the ipsilateral hemispheric flow). The MCA is a direct continuation and the main branch of the internal carotid artery (ICA), coursing in a horizontal plane laterally and slightly anteriorly. The initial or precommunicating portion of the MCA is referred to as the Ml segment and gives rise to numerous lenticulostriate perforators. In adults the Ml segment has a mean length of 16.2 mm. To ensure a reproducible window for monitoring, the transducer probe is adjusted so that the Ml segment flow velocity is accompanied with retrograde anterior cerebral artery flow velocity (Figure 9-1). The frequency spectrum of Doppler signals is displayed on a frequency analyzer in real time and can be stored, digitized, and analyzed at a later date for research or archiving purposes.
Rescue version of a carotid micro-endarterectomy: an ACE-ICA anastomosis with proximal Ica and distal ACE hemoclip obliteration
Published in International Journal of Neuroscience, 2023
Robert Bartoš, Aleš Hejčl, Jan Lodin, Martin Sameš, Tomas Marek
After finishing the suture, the operating neurosurgeon (RB) suspected insufficient artery flow and performed Doppler sonography of the vessel, which suggested impeded blood flow. Transcranial Doppler ultrasound was attempted; however. the patient did not have a sufficient temporal window and clinical monitoring was not possible due to global anesthesia. Thus, in order to preserve patency of the vessel, the surgeon decided to perform a direct anastomosis of the internal and external carotid arteries (ACE) (Figure 1B, C). This solution had the advantage of restoring artery flow, straightened out distal kinking of the artery and was technically feasible due to matching diameters of the ACE and ACI. The proximal ACI and distal ACE stumps were occluded with hemoclips. Immediately after surgery the patient had severe right-sided hemiparesis, which completely resolved within 24 h. Follow-up CTA demonstrated patency of the anastomosis (Figure 2A) and diffusion weighted imaging (MR DWI) showed minor areas of acute ischemia in the precentral gyrus (Figure 2B). The patient was discharged home on the fourth postoperative day. She was followed up for a total of 7 years, during which she did not experience any episodes of TIA or stroke. She had a pacemaker implanted by her cardiologist two years after the surgery and remains in his care to this day.
Transcranial Doppler Velocities among Sickle Cell Disease Patients in Steady State
Published in Hemoglobin, 2020
Khaled Salama, Rasha Rady, Rania H. Hashem, Mona El-Ghamrawy
Transcranial Doppler studies were performed using the Multi-Dop T digital unit with a sector probe (2–4 MHz) manufactured by Compumedics Germany GmbH, Hohentwiel, Germany (the DWL® Doppler systems offer all possibilities for the examination of disorders in cerebral blood circulation and reliably support the diagnosis and treatment of vascular anomalies, constrictions and occlusions). Assessment was done in the diagnostic and interventional radiology department at Cairo University Children Hospital, Cairo, Egypt, by a single operator who did not know the patients’ disease status. Technique was as per the STOP trial [4]. If all velocities were less than 170 cm/sec, the results were considered to be normal. Velocities of at least 170 but less than 200 cm/sec were considered conditional. To be considered abnormal, blood-flow velocity had to be at least 200 cm/sec in either the ICA or the MCA [4]. Conditional velocities were confirmed by a second reading within 6 months if low conditional (i.e. 171–180 cm/sec), within 3 months if high conditional (i.e. 181–199 cm/sec) and within 1 week if abnormal (i.e. equal or more than 200 cm/sec).
Quality And Feasibility of Sonographic Measurement of the Optic Nerve Sheath Diameter to Estimate the Risk of Raised Intracranial Pressure After Traumatic Brain Injury in Prehospital Setting
Published in Prehospital Emergency Care, 2019
Charles-Henri Houzé-Cerfon, Vincent Bounes, Johanna Guemon, Thibault Le Gourrierec, Thomas Geeraerts
Transcranial Doppler pulsatility index has been shown to detect low cerebral perfusion pressure due to an increased ICP. However, transcranial Doppler can be difficult to perform, even in experienced hands (3). Bedside measurement of optic nerve sheath diameter (ONSD) using sonography has recently emerged as an noninvasive method allowing the estimation of the risk of raised ICP (4,5). Increased ICP is transmitted to the subarachnoid space surrounding the optic nerve, causing optic nerve sheath expansion, and the expansion of this cerebrospinal fluid space can easily be detected using ultrasound. The sonographic ONSD measurement has been recently used in emergency department settings. The measurement is reproducible and easy to learn (6–8). However, to our knowledge, no studies have evaluated the feasibility and quality of ONSD measurement in prehospital care of patients with TBI.