[Risks of too rapid normalization of hyponatremia: central pontine myelinolysis].
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Demyelinating Diseases↗
Biomedical subjects
S Vorstrup
Publications and source records attributed to S Vorstrup.
Hemodilution in acute ischemic stroke.
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Acute Disease↗
Cerebral blood flow during delirium tremens and related clinical states studied with xenon-133 inhalation tomography.
The regional cerebral blood flow of 12 patients with severe alcohol withdrawal reactions (delirium tremens or impending delirium tremens) was measured during the acute state before treatment and after recovery. Greater cerebral blood flow was significantly correlated with visual hallucinations and agitation during the acute withdrawal reaction. The results suggest that delirium tremens and related clinical states represent a type of acute brain syndrome mainly characterized by CNS hyperexcitability.
Adult↗
Tomographic cerebral blood flow measurements in patients with ischemic cerebrovascular disease and evaluation of the vasodilatory capacity by the acetazolamide test.
Cerebral blood flow (CBF) was measured in a series of patients with ischemic cerebrovascular disease using xenon-133 inhalation and single photon emission computer tomography. The spontaneous course of CBF changes in a consecutive series of stroke patients was evaluated. A quite heterogeneous pattern of flow changes was observed: In patients with large cortical/subcortical infarcts, extensive hypoperfused areas were observed, often significantly larger than the corresponding hypodense lesion on the CT scan. Smaller CT lesions caused relatively smaller flow changes. Patients with lacunar infarcts showed only a discrete reduction of CBF, but comprising most of the ipsilateral hemisphere. Repeated CBF studies in the chronic phase showed, that the clinical improvement commonly noted in stroke patients is not related to a CBF increase. On the contrary, the CBF lesions tended to become somewhat larger and more demarcated even in cases where the finding of a normal angiogram and a transient state of hyperemia suggested a dissolution of the intracerebral embolus. The pathogenetic mechanisms for these persisting low flow areas in CT intact structures was discussed. One possibility was a selective neuronal cell damage in the peri-infarct areas caused by the ischemic insult. Such lesions would leave the structures macroscopically intact, but decrease both the metabolic demands and CBF. However, this interpretation finds little support in recent microscopic neuropathological studies in man. A more likely possibility was then considered to be disconnection (diaschisis) where the reduced flow is due to a decreased neuronal function caused by undercutting of afferent or efferent nervefibers. A crossed cerebellar diaschisis was observed in all patients with major infarcts in the forebrain. These findings were observed already in the acute phase, but persisted quite unchanged throughout the subacute and chronic phases. The patients with lacunar infarcts showed cerebellar diaschisis in the acute phase only, suggesting that a transient suppression of remote areas is possible too. In order to differentiate between permanent flow changes caused by a functional impairment and a possible hemodynamic component, CBF was measured before and after administration of a potent cerebral vasodilator, acetazolamide (Diamox). In normal cases tested with Diamox, an even CBF increase is noted throughout the hemispheres, while the cerebral metabolic rate for oxygen remains stable. In patients having a severe stenosis or occlusion of the internal carotid artery, this vasodilatory stress test will identify the patients having poor collateral capacity via the circle of Willis.(ABSTRACT TRUNCATED AT 400 WORDS)
Acetazolamide↗
Role of angiotensin in autoregulation of cerebral blood flow.
The presence of the renin-angiotensin system (RAS) in extrarenal tissues, namely the vascular wall and brain tissue, is well established. The availability of effective blocking agents, converting-enzyme inhibitors, has made it possible to further elucidate important functions of the extrarenal RAS. We have found that the angiotensin converting-enzyme inhibitor captopril shifts the limits of cerebral blood flow autoregulation to lower blood pressure levels in normotensive and in spontaneously hypertensive rats. This effect may explain our finding of a remarkable preservation of cerebral blood flow, despite significant blood pressure reduction, in patients with chronic heart failure. We suggest that the effect of angiotensin converting-enzyme inhibition on autoregulation of cerebral blood flow is mediated by a dilatation of larger cerebral arteries, which results from inhibition of the vascular tone normally maintained by locally produced angiotensin II.
Angiotensin II↗
Evaluation of the regional cerebral vasodilatory capacity before carotid endarterectomy by the acetazolamide test.
To estimate the regional perfusion pressure and possibly the stump pressure during carotid endarterectomy, cerebral blood flow (CBF) measurements including a vasodilatory test were performed preoperatively. CBF was measured by 133Xe inhalation and emission tomography. An intravenous dose of 1g acetazolamide (Diamox) was used as cerebral vasodilator. Thirty-six patients with a clinical history of previous strokes (9 cases) or transient ischaemic attacks (27 cases) were studied. Nine of the patients showed occlusion of the contralateral internal carotid artery (ICA). The percent flow increase induced by Diamox in the ipsilateral hemisphere correlated to the ICA pressure was measured before clamping (n = 32, r = 0.55, p less than 0.001). In 12 of the 36 patients, Diamox caused a significant change in the flow distribution indicating a restricted regional vasodilatory capacity and a reduced regional perfusion pressure. In addition, these 12 patients showed a low stump pressure (less than 50 mmHg). However, 8 additional patients had uniform CBF increases at the Diamox test, but showed low stump pressures. It is concluded, that preoperative tests of the cerebral vasodilational capacity can be used to identify most patients with a low ICA pressure, and a substantial fraction of patients that will develop a low stump pressure upon ICA clamping during operation. In these patients with abnormal Diamox tests surgical reconstruction is particularly indicated, but, at the same time the perioperative risks are presumably highest in this group.
Acetazolamide↗
Cerebral blood flow in patients with normal-pressure hydrocephalus before and after shunting.
Cerebral blood flow (CBF) was measured by xenon-133 inhalation and single photon emission tomography in 17 demented patients with normal-pressure hydrocephalus before and after shunt treatment. All patients had a decreased conductance to outflow (C out) of cerebrospinal fluid as measured by lumboventricular perfusion (C out less than 0.12 ml X mm Hg-1 X min-1). Computerized tomography (CT) scanning, clinical assessment, and neuropsychological grading were performed pre- and postoperatively. The preoperative CBF studies revealed abnormal flow patterns in all patients. Fourteen patients showed moderate-sized, large, or very large central low-flow areas, and four patients had reduced flow bilaterally in the occipital and contiguous temporoparietal regions. After shunting, six patients had a significant reduction in the size of the central low-flow area on the CBF map, agreeing well with the changes of ventricular size on the CT scan. All six patients showed an improvement in either clinical or neuropsychological grading. In 10 of the remaining 11 patients flow patterns were essentially unchanged; one patient deteriorated further. Four of these 11 patients improved on postoperative clinical or neuropsychological testing. Thus, a positive correlation was found between the changes in CBF and the reduction of the ventricular size on the CT scan, but changes in CBF as measured by the present technique did not accompany improvement in the functional state in all patients.
Adult↗
Drugs in acute ischemic cerebrovascular lesion evaluated by regional blood flow measurements in the brain.
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Acute Disease↗
Carotid surgery, cognitive function, and cerebral blood flow in patients with transient ischemic attacks.
Psychological testing, cerebral blood flow (CBF) measurement, and computed tomographic scan were performed before and 3 months after operation in 31 patients subjected to endarterectomy of the internal carotid artery (ICA) because of transient ischemic attacks and in 11 control patients operated on for atherosclerosis of the lower extremities. In preoperative psychological testing both carotid surgery patients and controls performed somewhat below the normal level for their age group. Postoperatively, cognitive functions improved in the carotid surgery group but not in the control group. The improvement was related to the laterality of the operation, being more marked in verbal tests in patients with left ICA operation and in visuospatial tests in patients with right ICA operation. Postoperatively regional CBF improved in 2 patients only. Hence the intellectual improvement could not be related to changes in CBF. Intellectual deterioration in patients with internal carotid atherosclerosis may be delayed or terminated by surgical abolition of the source of multiple cerebral embolizations.
Adult↗
Noninvasive xenon-133 measurements of cerebral blood flow using stationary detectors compared with dynamic emission tomography.
Repeated bedside measurements of CBF have been made possible by the recent development of a mobile unit with 10 stationary detectors using the intravenous xenon-133 method. To evaluate this technique, comparative CBF studies at rest and following the application of a cerebral vasodilatory stimulus (acetazolamide, 1 g i.v.) were performed with the mobile equipment and with xenon-133 single-photon emission inhalation tomography in patients with cerebrovascular disease. The CBF level and the flow response to acetazolamide as determined with the two methods were well correlated, although at low flow levels the stationary detectors yielded somewhat lower CBF values than did emission tomography. Considering the side-to-side asymmetry, an excellent correlation was obtained. Using the initial slope index, the stationary detectors revealed quantitatively 83% of the interhemispheric asymmetry and 63% of the asymmetry in the middle cerebral artery territory shown with the tomograph. As illustrated by a case history, the nontomographic CBF unit used in this study may provide reliable and useful information in patients with occlusive cerebrovascular disease by performing repeated CBF studies and challenging the cerebral circulation with acetazolamide.
Adult↗
Calcium antagonist (PY 108-068) treatment may further decrease flow in ischemic areas in acute stroke.
The effect of the possible influence of a new calcium antagonist, PY 108-068, on regional CBF was studied in patients suffering acute ischemic stroke. The dosage was 1.5 + 2.5 mg intravenously in six patients (series 1) and 2.5 + 5.0 mg intravenously in five other patients (series 2). CBF was measured before and after treatment by xenon-133 inhalation and single-photon emission computed tomography (Tomomatic 64). In the first series, no changes in hemispheric CBF, MABP, or clinical symptoms were noted after treatment, but one patient showed an increase of CBF in part of the periinfarct area. In the second series, slight increases in mean hemispheric flow values were seen, but in three of the five patients CBF decreased even further in the ischemic area. MABP decreased by 13%, and the clinical symptoms were unchanged.
Acute Disease↗
Effect of captopril on the cerebral circulation in chronic heart failure.
Cerebral blood flow (CBF) was investigated in 8 patients with chronic heart failure (CHF) (functional class III) and in twelve controls before and after administration of 6.25 mg and 25 mg captopril, respectively. In four controls, CBF was measured by the intracarotid xenon-133 (133Xe) injection technique using stationary external detectors, while inhalation of 133Xe and single photon emission computer tomography was used in the remaining cases. In the control group, the cerebral metabolic rate for oxygen was calculated from measurements of the arterio-venous oxygen difference as well. Mean CBF was significantly (P less than 0.01) lower in the patients with CHF as compared to our controls. Following captopril administration the mean arterial blood pressure decreased in the CHF patients, ranging from 5 to 40%. Three patients showed decreases of blood pressure to values of 56, 65, and 76 mm Hg, but no symptoms of cerebral hypoperfusion were elicited. CBF was unchanged after captopril administration, even in the patients showing a marked reduction in blood pressure. In the control group, the blood pressure, CBF and the cerebral metabolic rate for oxygen remained essentially constant following captopril administration. It is concluded that the cerebral circulation is well preserved during captopril treatment of chronic heart failure. This might be explained by a shift of the lower limit of CBF autoregulation towards lower blood pressure levels.
Adult↗
Cerebral blood flow in acute and chronic ischemic stroke using xenon-133 inhalation tomography.
Serial measurements of cerebral blood flow (CBF) were performed in 12 patients with acute symptoms of ischemic cerebrovascular disease. CBF was measured by xenon-133 inhalation and single photon emission computer tomography. Six patients had severe strokes and large infarcts on the CT scan. They showed in the acute phase (Days 1-3) very large low-flow areas, larger than the hypodense areas seen on the CT scan. The cerebral vasoconstrictor and vasodilator capacity was tested in the acute phase following aminophylline and acetazolamide, respectively. A preserved but reduced reactivity was seen at both tests in all 6 cases in the infarct and the peri-infarct areas. On Days 5-25, 4 of the patients had transitory increases (59-108%) of CBF, probably corresponding to lysis of an intracerebral embolic occlusion. The other 2 patients showed on Days 7-15 only a moderate CBF increase (appr. 20%), both had occlusion of the relevant internal carotid artery. In all 6 patients, CBF studies at 2 and 6 months resembled the acute phase, showing large areas with reduced flow. At the 6 months follow-up, the vasodilatory stress test was repeated, and all but one showed a preserved but reduced vasoreactivity in the infarct and peri-infarct tissue. Of the remaining 6 patients, one had a pontine infarct and one had no lesions on the CT scan, both having normal angiograms and CBF maps. Four patients had small deep or subcortical CT lesions, and showed a slight, but persistent CBF reduction of about 6-8% in the parietal region on the affected side. No changes in the flow pattern were seen at the vasoreactive studies. A likely explanation for the finding of superjacent low-flow areas is an intrahemispheric uncrossed diaschisis. This interpretation is discussed in relation to the peri-infarct low-flow area seen in the 6 cases with large infarcts.
Adult↗
Intracranial pressure, conductance to cerebrospinal fluid outflow, and cerebral blood flow in patients with benign intracranial hypertension (pseudotumor cerebri).
Intracranial pressure, conductance to cerebrospinal fluid outflow, and cerebral blood flow were investigated in 14 patients with benign intracranial hypertension (pseudotumor cerebri). Intracranial pressure was increased in 9 patients (20 to 30 mm Hg), borderline in 4 patients (15 to 18 mm Hg), and normal in 1 patient (8 mm Hg). Six patients had plateau waves, and all had B waves in more than 50% of the monitored time. Conductance to cerebrospinal fluid outflow, measured by a lumbo-lumbar perfusion method, was significantly reduced: 0.042 ml X mm Hg-1 X min-1 (+/- 0.004 [SEM]; normal, more than 0.080 ml X mm Hg-1 X min-1). Cerebral blood flow was measured by xenon 133 inhalation and single photon emission computer tomography. Mean hemispheric flow was normal in all cases, averaging 59 +/- 9 ml X 100 gm-1 X min-1. Only 2 patients showed focal low-flow areas. Thus, a disturbance of cerebrospinal fluid circulation seems to be of pathogenetic significance in benign intracranial hypertension.
Adolescent↗
Tomographic cerebral blood flow calculation.
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Brain↗
rCBF after TIA and during migraine attacks.
TIA is usually caused by embolism from a carotid stenosis. The stenosis has no hemodynamic significance, but recent studies of regional cerebral blood flow have indicated that this occurs in a few cases. Traditionally, TIA are not considered to cause cerebral damage, but CT-studies have revealed a number of silent infarcts and rCBF measurements have shown even more persistent abnormalities of blood flow. In classic migraine, alterations of rCBF are completely different, indicating a mechanism progressing in the cerebral cortex, probably the spreading depression of Leao. Similar blood flow changes are not seen in common migraine, where tomographic rCBF determinations have been normal.
Cerebrovascular Circulation↗
Converting enzyme inhibition resets cerebral autoregulation at lower blood pressure.
The cerebrovascular effect of converting enzyme inhibition was investigated in normal volunteers, in hypertensive patients and in patients with severe chronic heart failure. Cerebral blood flow (CBF) was measured by single photon emission tomography of the uptake and wash-out of inhaled xenon-133. In some of the patients, CBF was also monitored by repeated determinations of the cerebral arterio-venous oxygen difference. In the normal volunteers and the hypertensive patients captopril (50 mg) caused a downward shift of the lower limit of CBF autoregulation of 10-15 mmHg. In some of the patients with chronic heart failure, captopril (6.25 mg) induced a marked decrease of the arterial blood pressure. Regional and average CBF, however, remained constant. These findings indicate that captopril treatment may protect the brain against ischaemia during sudden decreases of the blood pressure by a shift of the lower limit of CBF autoregulation.
Angiotensin-Converting Enzyme Inhibitors↗
Dynamic SPECT of the brain using a lipophilic technetium-99m complex, PnAO.
The lipophilic 99mTc-labeled oxime propylene amine oxime (PnAO) should, according to recent reports behave like 133Xe in the human brain. This study compares SPECT images of the two tracers in six subjects: four stroke cases, one transitory ischemic attack case and one normal subject. Technetium-99m PnAO was injected i.v. as a bolus of 15 to 25 mCi. The distribution was followed over 10-sec intervals using a highly sensitive, rapidly rotating SPECT (Tomomatic 64) and compared to 133Xe flow maps. Upon arrival of the PnAO bolus to the brain, a high uptake was found in brain tissue with high cerebral blood flow followed by rapid washout. In the stroke cases, low flow areas were equally well visualized by both tracers. Two dissimilarities were seen in the initial pictures: PnAO visualized the cerebral veins and showed a lesser contrast of gray:white matter uptake. The results suggest that PnAO has a high yet incomplete brain extraction yielding a flow dominated initial distribution with limitations mentioned.
Adult↗