Cerebral ischemia model using mongolian gerbils-comparison between unilateral and bilateral carotid occlusion models.

We permanently occluded unilaterally and/or bilaterally the carotid arteries of anesthetized Mongolian gerbils (60-80 g) and compared the two models. In the former, stroke-positive animals were selected by calculating the stroke index score of the conscious animals. Selection was not made in the latter. We measured the rCBF of the cerebral cortex, hippocampus, and diencephalon using the (3)H-nicotine scintillation method; analyzed the EEG using the wave-form recognition method (Fujimori); measured ATP, PCr (phosphocreatine), lactate, and glucose content in the cerebral hemisphere using the Lowry method; and measured infarct size on HE-stained coronal sections. All parameter values were uniform in the gerbils of the unilateral model, whereas great variation was observed in the right and left cerebral cortex, hippocampus, and diencephalon in the bilateral occlusion model. Therefore, we have discarded the bilateral model and used the stroke-positive unilateral model only.By changing the length of time of the unilateral carotid occlusions and intervals, we found that two 10-min unilateral carotid occlusions with a 5-h interval between them achieved a threshold ischemic insult in gerbils, which produced uniform cortical focal infarctions that evolved in the maturing DSNN on the coronal surface sectioned at the chiasmatic level (Face A). This model showed a marked reduction in the occurrence of ischemic epilepsy and death.

Intraoperative monitoring of depth-dependent hemoglobin concentration changes during carotid endarterectomy by time-resolved spectroscopy.

By measuring the adult human head during carotid endarterectomy, we investigate the depth sensitivity of two methods for deriving the absorption coefficient changes (Dmu(a)) from time-resolved reflectance data to absorption changes in inhomogeneous media: (1) the curve-fitting method based on the diffusion equation (DE-fit method) and (2) the time-independent calculation based on the modified Lambert-Beer law (MLB method). Remarkable differences in the determined values of Dmu(a) caused by clamping the external carotid artery and subsequently clamping the common carotid artery were observed between the methods. The DE-fit method was more sensitive to mu(a) changes in cerebral tissues, whereas the MLB method was rather sensitive to mu(a) changes in the extracerebral tissues. Our results indicated that the DE-fit was useful for monitoring the cerebral blood circulation and oxygenation during neurosurgical operations. In addition, the combined evaluation of mu(a) changes with the DE-fit and MLB methods will provide us with more available information about the hemodynamic changes in the depth direction.

Plasma concentrations of brain natriuretic peptide in patients with acute ischemic stroke.

BACKGROUND: Acute blood pressure (BP) elevation and cardiac abnormalities are known to follow ischemic stroke. Brain natriuretic peptide (BNP), which is produced in response to such cardiovascular alterations, is expected to play a hemodynamic role. We measured plasma BNP concentrations in patients with cerebral infarction (CI) to determine the implications of BNP in acute ischemic stroke. METHODS: Eighty-eight patients with CI, 59 with essential hypertension, 44 with spontaneous intracerebral hemorrhage, 22 with asymptomatic atrial fibrillation (Af), and 20 age- and sex-matched healthy volunteers were recruited in the study. CI patients were divided into 2 subgroups either having Af (27 patients) or not (61 patients). BNP levels were repeatedly measured in 58 patients with CI. BNP levels were compared between ischemic subgroups categorized by size of infarction. Correlation was investigated between BNP levels and hemodynamic parameters. RESULTS: BNP levels in CI patients were significantly higher, but they decreased in the subacute period. BNP levels in CI patients without Af were correlated with mean arterial blood pressure (MAP) on admission or the degree of reduction in MAP at day 1, while in CI patients with Af BNP levels showed negative correlation with MAP on admission. Follow-up serum sodium levels in CI patients with Af were negatively correlated with BNP levels on admission. CONCLUSIONS: This study suggests the hemodynamic implications of BNP in acute ischemic patients.

Plasma concentrations of atrial and brain natriuretic peptides in a case with hypertensive encephalopathy.

Hemodynamic mechanism for brain edema forrmation in patients with hypertensive encephalopathy is unclear. Potential roles of natriuretic peptides in the pathogenesis of hypertensive encephalopathy are discussed. A 32-year-old man presented with slight left hemiparesis. He was slightly confused, and his blood pressure was extremely high. Cranial plain computerized tomography scans revealed diffuse brain edema mainly in the supratentorial white matter region. Blood examination revealed that plasma concentrations of atrial and brain natriuretic peptides were significantly high. His left hemiparesis disappeared within a day, but he tended to be agitated. His altered mental status, however, resolved with control of blood pressure. Serial magnetic resonance imagings demonstrated that the magnitude of brain edema was attenuated in proportion to decline in plasma concentrations of natriuretic peptides. This case suggests that significant elevation of plasma concentrations of natriuretic peptides may contribute to an acute rise in blood pressure, and that these peptides potentially play an important role in development of brain edema in hypertensive encephalopathy.