Cerebral Artery Flow Velocity Research Articles

Normal range for blood flow velocity in cerebral arteries of newly born term infants

A cross-sectional study of 128 healthy full term infants was made using duplex Doppler ultrasonography in order to establish a normal range for cerebral blood flow velocity (CBFV) in the first week of life. Recordings were made from both the anterior (ACA) and middle cerebral arteries (MCA). There was a statistically significant increase in CBFV in both the ACA and MCA over the first four days of life, which was particularly obvious in the first 24 h. There is a close relationship between measurement of CBFV from the ACA and the MCA, although the velocity tends to be higher in the MCA.

Cerebrovascular reserve capacity (CRC) in carotid artery disease: a routine test in selection for surgical treatment?

An increase of arterial carbon dioxide (CO2) partial pressure induces an increase of cerebral blood flow by dilatation of the resistance vessels. By the Transcranial Doppler sonographic technique (TCD) blood flow velocity as a correlate of flow volume can be measured within the great basal intracranial arteries. We investigated 8 patients with an internal carotid artery occlusion or high-grade stenosis and 5 cerebrovascular diseased patients without extracranial stenosis. 12 healthy volunteers and patients without vascular disease served as the control group. Blood flow velocities in the middle cerebral arteries were evaluated before and after 5 minutes of breathing a 5% CO2 gas mixture. In a prestudy the end tidal pCO2 was monitored during this procedure. As a result of the close parallelity of pCO2 increase in the prestudy group we planned to standardize the CO2 reactivity tests without consideration of the individual pCO2 values. The CO2 inhalation provoked a flow velocity increase of at least 20% in the control subjects (47.1 +/- 17.3%). The vascular diseased without extracranial stenosis responded with 34.8 +/- 17.4% (minimum: 23.5%, n. s.). The CO2 reactivity in cases of occlusion or greater than 50% stenosis was significantly decreased (p less than 0.001) both when considering only the affected sides (12.4 +/- 7.5%, maximum: 20%) and when including the non affected sides (22.6 +/- 15.0%). It is concluded that the CO2 reactivity test is a simple and valid method to evaluate the cerebrovascular reserve capacity in any case of uncertainty about the benefits of surgical treatment of a carotid stenosis. In future this technique might become one fundamental argument beside others in selecting adequate treatment.

Flow Velocity in Cerebral Arteries in the Newborn

Flow Velocity in Cerebral Arteries in the Newborn

Flow velocity in cerebral arteries in the newborn.

Flow velocity in cerebral arteries in the newborn.

Cerebral perfusion during major cardiac surgery in children.

Six children undergoing major cardiac surgery had extensive cerebral monitoring during cardiopulmonary bypass (CPB). The monitoring included continuous recording of arterial blood pressure (BP), central venous pressure (CVP), cerebral electrical activity by a cerebral function monitor (CFM), and middle cerebral artery (MCA) flow velocity by the transcranial pulsed Doppler (TCD) technique. Introduction of the precooled blood containing priming solution resulted in rapid fall in BP as well as MCA velocities in these children at the start of CPB. During steady-state CPB at 20 degrees C, MCA flow velocities were reduced in five of six children, range 45%-105% of pre-bypass value. These flow velocity values were recorded at cerebral perfusion pressures (CPP = BP - CVP) in the range of 14-26 mmHg. This reduced cerebral perfusion during steady-state CPB appears to be more than sufficient to meet the cerebral metabolic demands at the particular temperature. The reduced cerebral perfusion is in contrast to the enhanced perfusion found in adults during moderately hypothermic (28 degrees-30 degrees C) low-flow, low-pressure CPB previously reported. It was presumably due to the reduced temperature, reduced perfusion pressure, and less hemodilution. During periods of constant temperature, hematocrit, and partial pressure of carbon dioxide (PaCO2), MCA flow velocities varied passively with changes in CPP, demonstrating that cerebral autoregulation was not operative. Transcranial Doppler appears to be a suitable tool for investigating CPB techniques optimal with respect to cerebral circulation.

13 CEREBRAL CIRCULATION IN THE NEONATE: ASSESSMENT USING TRANSCEPHALIC IMPEDANCE AND DOPPLER ULTRASOUND

It has been suggested that fluctuations in arterial blood pressure and cerebral arterial flow velocity (CAFV) alter brain perfusion and lead to intraventricular haemorrhage (Perlman et al, New Eng J Med 309: 209, 1983). Although intermittent measurements of CAFU can be obtained by Doppler ultrasound, a major problem is the inability to monitor cerebral circulation continuously.Experimental design: A microprocessor based technique of transcephalic electrical impedance (dZc) was used to monitor the cerebral circulation continuously (Murphy et al, in “Electronics in Medicine and Biology”, IERE, London 1986). Average dZc, arterial blood pressure and heart rate were continuously displayed and stored. Measurements of avg dZc amplitude were compared with intermittent values of CAFV (Angioscan III) obtained from the anterior cerebral artery. Neonates with birth weight <1500g were studied for the first 48 hours. Those who received either indomethacin or aminophylline were studied before and for one hour after the dose.Results and comments: In the 48-hour studies (n=3) the r values for the intra-individual correlation between avg dZc and mean CAFV were 0.40, 0.70 and 0.74 (all p<0.05). In the 1-hour studies (n=5) indomethacin caused a decrease of 25-30% in both signals. CAFV is an estimate of blood flow in the anterior cerebral artery whereas dZc reflects global changes in instantaneous intracerebral pulsatile blood volume. Our preliminary results suggest a relationship between these signals.Financial support: The Medical Foundation - University of Sydney; the English Speaking Union and Nestle (PBC): The British Council, Turku University Foundation, and Academy of Finland (JATV).

Dependency of blood flow velocity in the middle cerebral artery on end-tidal carbon dioxide partial pressure--a transcranial ultrasound Doppler study.

The end-tidal carbon dioxide partial pressure (PCO2) response curves for the flow velocity in the middle cerebral artery were studied in 31 normal subjects with transcranial Doppler techniques. An exponential curve with an exponent of 0.034 mm Hg-1 was found to be a good fit to the recorded data. By means of this relationship, recordings of flow velocity in cerebral arteries can be normalized to a standard value of PCO2. Physiological aspects of cerebrovascular reactivity to PCO2 and the clinical implications of the PCO2 response curve are discussed. The normal material provides a reference for assessing pathological responses.