Neurological research
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Neurological research · Dec 1995
Early hemodynamic changes at the microcirculatory level and effects of mannitol following focal cryogenic injury.
Changes in cerebral blood flow due to infusion of hyperosmolar solutions are of considerable importance in states of raised intracranial pressure. The present study was aimed to evaluate the effects of mannitol on the cerebral microcirculation, in a model of vasogenic brain edema. A right fronto-parietal craniotomy was performed in 30 adult Sprague-Dawley rats. ⋯ There was not significant difference between groups 2 and 3; however, there was a significant difference between mannitol and control groups after 15 min. During the early phase of vasogenic edema, early use of mannitol did not increase the blood flow, but stabilized it, preventing further decrease. Laser-Doppler flowmetry is a valuable method for continuous estimation of hemodynamic changes in the cerebral microcirculation.
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Neurological research · Oct 1995
Correlation of jugular venous oxygen saturation to spontaneous fluctuations of cerebral perfusion pressure in patients with severe head injury.
Continuous measurements of mean arterial pressure (MAP), ICP, and jugular venous oxygen saturation (SjO2) were performed in 11 patients with severe head injury (GCS 3-7) to assess the dependence of SjO2 from the cerebral perfusion pressure (CPP), trying to establish an indirect measure of cerebrovascular autoregulation. Changes in CPP resulting from spontaneous fluctuations in MAP or ICP induced highly significant alterations in SjO2 in the range of 0.14-0.56% SjO2 mmHg-1 CPP in all patients and all periods after trauma. The analysis of the distribution of the SjO2:CPP-ratios showed the highest frequency of values in the range of 0.0-0.25% SjO2 mmHg-1 CPP in 9 of the 11 patients. ⋯ No predictable relationship of the SjO2:CPP-ratio to the level of ICP could be demonstrated in the patients. Because changes in SjO2 induced by alterations in CPP were found in all patients and throughout the acute phase of severe head injury, these changes more probably reflect physiological alterations in CBF with varying perfusion pressure rather than impaired autoregulation after head trauma. Although assessment of cerebral autoregulation by estimation of the SjO2:CPP-ratio offers new possibilities for monitoring of these patients, the high frequency of erroneous readings or irregular fluctuations of the SjO2-signal from the fibreoptic catheter limits the usefulness of the SjO2-dependency from CPP for practical use in the intensive care unit.
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Neurological research · Apr 1995
Noninvasive cerebral optical spectroscopy: depth-resolved measurements of cerebral haemodynamics using indocyanine green.
To investigate the feasibility of a newly developed, near-infrared optical spectroscopy device, we analysed measurements of the infrared tracer indocyanine green (ICG) using sensors with a single near infrared light source and multiple light detectors. Two ml of ICG dye, 1.0 mg ml-1 in concentration, were injected into the internal carotid artery during cerebral angiography in 14 adult patients. The resultant washout curves were measured bilaterally using sensors with 4 detectors spaced at 10, 20, 30 and 40 mm from the infrared light source on the right side, and 15, 25, 35 and 45 mm from the source for the left side, respectively. ⋯ No substantial difference in attenuation was observed in any of the detectors during external carotid injection of ICG. The resultant information related depth of penetration of the light with source-detector separation distances. The feasibility of the system for measuring cerebral oxygen saturation and haemodynamics noninvasively or monitoring at bedside is discussed.
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Neurological research · Dec 1994
Effects of topical methylene blue on cyclic GMP level, blood flow, and O2 consumption in focal cerebral ischaemia.
We hypothesized that a decrease in cyclic GMP, a second messenger in the glutamate-nitric oxide pathway, would reduce oxygen consumption and improve O2 balance in the ischaemic cerebral cortex. To test this hypothesis, a study was performed in unilateral middle cerebral artery occluded rats which were assigned to either a control or methylene blue (10(-3) M) group. Regional cerebral blood flow was determined using 14C-iodoantipyrine and regional arterial and venous O2 saturations were determined by microspectrophotometry (n = 6). ⋯ The regional cerebral blood flow and O2 consumption in the control group were 50% and 32% lower than those in corresponding contralateral cortex. Topical methylene blue did not alter regional cerebral blood flow and O2 consumption in the ischaemic cortex. Our data showed that cyclic GMP is not a major controller on O2 supply or O2 consumption in the ischaemic brain.
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Neurological research · Oct 1994
Comparative StudyRecordings from the facial motonucleus in rats with signs of hemifacial spasm.
We recorded evoked potentials from the facial motonucleus of rats in response to electrical stimulation of the temporal branch of the facial nerve in which chronic irritation from a blood vessel had caused the development of an abnormal muscle response. The abnormal muscle response that can be recorded from face muscles that are innervated by one branch of the facial nerve in response to electrical stimulation of a different branch is regarded to be a sign of hemifacial spasm. In the recordings from the motonucleus in rats that showed such an abnormal muscle response (model rats) there was a late component at a latency of about 5 msec, in addition to the early component with a latency of 1.5-2.5 msec that is also observed in normal rats. ⋯ This value is close to the sum of the conduction time from the motonucleus to the mentalis muscle (2 msec) and the latency of the late response from the motonucleus (5 msec). Similar results were obtained in rats in which the facial nerve had been chronically stimulated electrically and which had developed an abnormal muscle response. The results of this study further support the hypothesis that the hyperactivity of the facial motonucleus is the pathophysiology of hemifacial spasm.