Cerebral Blood Volume Responses Research Articles

CEREBRAL HAEMODYNAMICS DURING FAILURE OF OXIDATIVE PHOSPHORYLATION FOLLOWING BIRTH ASPHYXIA

Twelve infants born at 36-42 weeks of gestation who had suffered severe birth asphyxia were studied repeatedly in the first week of life by near infrared spectroscopy (NIRS) and magnetic resonance spectroscopy (MRS). Six infants with normal brains were also studied by NIRS to provide control data. Phosphocreatine/inorganic orthophosphate (PCr/Pi) concentration ratios determined by MRS following asphyxia were frequently normal in the first 48 hours, but subsequently low ratios were always seen. In the first 48 hours mean cerebral blood volume (CBV) was elevated (4.40±SEM 0.38ml.100g−1) compared with the control infants (1.98±0.26ml.100g−1, p<0.001), and CBV response to changes in arterial carbon dioxide tension (PaCO2) was reduced (0.10±0.06 compared with 0.53±0.06ml.100g−1.kPa−1, p<0.001). Cerebral haemodynamics in the asphyxiated infants subsequently returned towards normal. Thus, following birth asphyxia, elevated blood volume and reduced response to changes in PaCO2 may be detected prior to impairment of oxidative phosphorylation. Supported by the MRC, Wellcome Trust and Hamamatsu Photonics KK.

The response of cerebral blood volume to changes in arterial carbon dioxide tension measured by near infrared spectroscopy in newborn infants

The response of cerebral blood volume to changes in arterial carbon dioxide tension measured by near infrared spectroscopy in newborn infants

The response of cerebral blood volume to changes in arterial carbon dioxide tension measured by near infrared spectroscopy in newborn infants

The response of cerebral blood volume to changes in arterial carbon dioxide tension measured by near infrared spectroscopy in newborn infants

Local cerebral blood volume response to carbon dioxide in man.

We used an emission tomographic brain scanner to investigate the relationship between local cerebral blood volume (LCBV) and arterial blood carbon dioxide tension (PaCO2) in normal awake man. Measurements were made separately in three dimensions in various regions of grey and white matter, and the resting LCBV as well as the difference in sensitivity among these regions were compared. Over the range of PaCO2 studied (20-42 torr), the response of both the grey matter and the white matter to carbon dioxide was linear. The LCBV sensitivity of the grey matter to changes in PaCO2 was 0.053 ml/100 g per torr PaCO2 and in the white matter this sensitivity was 0.046 ml/100 g per torr PaCO2. These sensitivities were found not to be significantly different, yielding a slope of 0.049 ml/100 g per torr PaCO2 for the LCBV-PaCO2 curve for the entire brain. This is in excellent agreement with the other data for the whole brain. The resting cerebral blood volume of the grey matter at a PaCO2 of 34.4 torr, which was the average resting arterial carbon dioxide tension of the subjects, was 5.0 ml/100 g and was significantly higher than for white matter, which was 3.6 ml/100 g. At the local level, the cerebral blood volume of the frontal cortex is significantly less than that of the thalamus, whereas the frontoparietal cortex in the region of the sylvian fissure has a local cerebral blood volume significantly greater than that of the thalamus.

Local cerebral blood volume response to carbon dioxide in man

We used an emission tomographic brain scanner to investigate the relationship between local cerebral blood volume (LCBV) and arterial blood carbon dioxide tension (PaCO2) in normal awake man. Measurements were made separately in three dimensions in various regions of grey and white matter, and the resting LCBV as well as the difference in sensitivity among these regions were compared. Over the range of PaCO2 studied (20-42 torr), the response of both the grey matter and the white matter to carbon dioxide was linear. The LCBV sensitivity of the grey matter to changes in PaCO2 was 0.053 ml/100 g per torr PaCO2 and in the white matter this sensitivity was 0.046 ml/100 g per torr PaCO2. These sensitivities were found not to be significantly different, yielding a slope of 0.049 ml/100 g per torr PaCO2 for the LCBV-PaCO2 curve for the entire brain. This is in excellent agreement with the other data for the whole brain. The resting cerebral blood volume of the grey matter at a PaCO2 of 34.4 torr, which was the average resting arterial carbon dioxide tension of the subjects, was 5.0 ml/100 g and was significantly higher than for white matter, which was 3.6 ml/100 g. At the local level, the cerebral blood volume of the frontal cortex is significantly less than that of the thalamus, whereas the frontoparietal cortex in the region of the sylvian fissure has a local cerebral blood volume significantly greater than that of the thalamus.

The effects of iodinated contrast agents on autoregulation of cerebral blood flow.

The effects of an iodinated contrast agent, Renografin-76® upon cerebral autoregulation was studied in rhesus monkeys. This was done by measuring the effects of an intravenous injection of Renografin-76 upon: (1) the response of baseline CBF as measured by the washout of a carotid bolus of H 2 15 O during and after the injection of Renografin-76, (2) the response of CBF monitored continuously by a Doppler flow probe technique to changes in the mean arterial blood pressure (MABP) before and after an injection of Renografin-76, and (3) the response of the regional cerebral blood volume (rCBV) as measured by stimulated x-ray fluorescence. An intravenous injection of Renografin-76 can disturb cerebral autoregulation in the rhesus monkey for as long as 15 minutes after the beginning of the injection. After the intravenous in jection of Renografin-76, transient rises in both CBF and MABP lasting from 2 to 12 minutes occurred on an average of 23% and 16%, respectively, over control values.