It has been reported that a rapid elevation in the intracranial pressure is associated with increased arterial pressure, reduced heart rate and irregular respiration. In the present study an effort was directed to observe the possible blocking effect of dibenzyline, an alpha-sympathetic blocking agent, administered prior to the intracranial pressure elevation. Alhino rabbits were divided into two experimental groups: in one group, the intracranial pressure was raised by infusing normal saline into the extradural space and was sustained for 30 minutes, while in the other group, dibenzyline(12mg/kg B.W.) was administered 16 hours prior to the intracanial pressure elevation. In both groups, the arterial pressure, heart rate and respiratory rate were measured for 30 minutes at 5 minuteintervals. In the intracranial pressure elevated group, the arterial pressure increased to 99 mmHg at 10 minutes in comparison with 88mmHg in the beginning. At 25 minutes, it returned to or near its initial level. The slowing of the heart rate was seen toward the end of the response, i.e. in the beginning, 269 rate/min, at the end, 214 rate/min. The respiratory rate did not show any significant change. In the dibenzyline pretreated group, the arterial pressure and heart rate did not change markedly from the initial levels. From the above result, it can be stated that dibenzyline has blocking effects on the increased arterial pressure and reduced heart rate in rabbits during increased intracranial pressure.
Arterial Pressure ; Blood Pressure* ; Heart Rate* ; Heart* ; Intracranial Pressure ; Phenoxybenzamine* ; Rabbits* ; Respiration ; Respiratory Rate*

OBJECTIVE: Perfusion-computed tomography (CT) is useful and quick diagnostic tool for evaluating ischemic stroke patients. We evaluated three measurement maps, cerebral blood flow (CBF), cerebral blood volume (CBV) and time to peak (TTP) for their usefulness in deciding on revascularization surgery using CT parameters after single photon emission computed tomography (SPECT) findings in chronic steno-occlusive disease patients. METHODS: We retrospectively investigated 47 patients with unilateral internal carotid artery (ICA) or middle cerebral artery (MCA) steno-occlusive disease . All patients underwent digital subtraction angiography (DSA) as well as an acetazolamide challenge with SPECT and perfusion CT. Patients who showed decreased reserve capacity with a Diamox challenge were classified in the positive group, whereas patients who had no difference in reserve capacity were placed in the negative group. RESULTS: Thirty-one patients were positive and the remaining 16 were negative. Differences in rCBV and rCBF parameters between normal cerebral hemispheres and cerebral hemispheres with steno-occlusive disease did not correlate with SPECT results, but TTP values did. SPECT results seemed relevant when TTP differences between hemispheres with normal and steno-occlusive disease were more than 1.55 times. CONCLUSION: Perfusion CT is a useful tool for the rapid, adequate diagnosis of large territorial infarcts, and the TTP map of perfusion CT is a sensitive and reliable parameter to show the status of collateral circulation in chronic cerebrovascular ischemic disease.
Acetazolamide ; Angiography, Digital Subtraction ; Blood Volume ; Carotid Artery, Internal ; Cerebrum ; Collateral Circulation ; Hemodynamics ; Humans ; Middle Cerebral Artery ; Perfusion ; Retrospective Studies ; Stroke ; Thymine Nucleotides ; Tomography, Emission-Computed, Single-Photon

To evaluate the biomechanical changes and cerebral blood flow in hydrocephalic brain, this study was designed to determine the regional cerebral blood flow(rCBF; frontal cortex and periventricular area), the pressure volume index(PVI) and the resistance to the absorption of cerebrospinal fluid(Ro) in different stages of the kaolin-induced hydrocephalus. Fifty five 8 week-old cats, weighing 900g to 1300g were used in this experiment. The experimental animals were divided into 2 groups ; a normal control(5 cats), and kaolin-induced hydrocephalic groups(50 cats). The kaolin-induced 1,2,4,6 and 8 weeks hydrocephalic groups after intracisternal injection of the kaolin. The rCBF was measured by hydrogen clearance technique and the PVI and Ro were determined by the technique of bolus manipulation of CSF. A significant elevation of the intracranial pressure(ICP) was observed in 2 weeks after kaolin injection and peak value(ICP=10.2+/-0.9mmhg) was obtained in 4 weeks after Kaolin injection. The significant decrease in rCBF were revealed in both frontal cortex and periventricular area of kaolin-induced hydrocephalic cats. The PVI was significantly increased from the normal value 0.77+/-0.02ml to 1.60+/-0.16ml at 4 weeks after kaolin injection and increased to 2.12+/-0.34ml at 6 weeks after kaolin injection. Ro was significantly decreased from the normal value 90.6+/-1.3mmHg/ml/min to 36.8+/-4.3mmHg/ml/min at 4 weeks after kaolin injection and further decreased to 6.2+/-1.9mmHg/ml/min at 8 weeks after kaolin injection. In Hydrocephalic cats, the size of the ventricle(septum pellucidum-caudate nucleus distance) continued to increase in size up to 9.40+/-0.7mm at the 4th week. However, there was no further increase in ventricular size after the 4th week. This study indicated that kaolin-induced hydrocephalic cats led to dramatic changes in volume-buffering capacity expressed as PVI, coupled a reduction in the Ro. The absorptive defect and also loss of volume-buffering capacity are not sufficient to cause progressive ventricular enlargement. It is assuming that some microcirculatory impairment in the brain parenchyma is playing an important role which facilitates ventricular expansion with changes of biomechanical property of the brain.
Absorption ; Animals ; Brain ; Cats ; Hydrocephalus* ; Hydrogen ; Kaolin ; Reference Values