摘要:

A variety of methods for measuring cerebral blood flow have been developed in the past 25 years since Kety and Schmidt developed their method based on the Fick principle. None of the currently used methods approaches the clinical ideal, since none of the techniques are accurate, reproducible and noninvasive. Most accurate techniques involve catheterization of internal carotid artery and/or jugular vein with those attendant risks. There has been considerable enhancement of our understanding of the pathophysiology of cerebral circulation, particularly in the areas of brain injury and disordered systemic metabolism, but the clinical usefulness of the test at the present time is limited.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Spinal cord ischemia is a rare complication of rupture of an abdominal aortic aneurysm or its emergency surgical treatment; only seven cases have been reported previously. A patient with this complication is described. It was characterized by postoperative total loss of all forms of sensation in the legs and partial sparing of motor function. The patient had been in shock, but the only other organ to suffer ischemic changes was the bowel. The condition, therefore, was attributed to local interference with the blood supply of the lumbosacral cord which is derived principally from the abdominal aorta through varying numbers of lumbar arteries. Recovery was virtually complete.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

The influence of infusion of hydralazine, isoxsuprine or nylidrin on blood flow in the basilar artery and on systemic blood pressure was investigated in anesthetized dogs. The drugs were administered individually in 1-mg and 2-mg doses and in various combinations of 1 mg each by injection just proximal to the formation of the basilar artery. Analysis of the data revealed significant increases in blood flow (P<0.05) immediately after injection and a statistically significant (P<0.05) interaction between time and drug. No statistical differences were found in comparisons of the effects of the 1-mg and 2-mg dose levels for any of the drugs. At either dosage isoxsuprine and nylidrin caused a 16% to 28% decrease in systemic blood pressure, while hydralazine effected a more moderate, approximately 5%, decrease. Basilar flow responded to 1-mg combinations of isoxsuprine/hydralazine and nylidrin/hydralazine with a consistent 25% to 30% increase. However, the flow response to nylidrin/isoxsuprine was unpredictable. The data indicate that these substances increased basilar arterial flow by inducing a transient local vasodilatation. The effects of the drug combinations on flow were in general synergistic and positive, and were similar to those after infusion of the individual drugs, except for a somewhat slower initial response and a longer duration.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Recent reports indicate that in cases of elevated plasma or blood viscosity, red cell velocity through the cerebral microcirculation is unimpaired while plasma transit is retarded. One explanation may be that plasma skimming is increased, with increased shunting of plasma into longer, less direct flow paths, while an increasing proportion of red cells take shorter paths. Such inhomogeneities of flow on a microvascular level can be directly demonstrated in cases of endothelial damage or anoxia, and may produce an altered regional hematocrit.Measurements of regional cerebral blood flow are dependent upon regional hematocrit because this affects the tissue:blood partition coefficient (λ) of diffusible indicators. Hence changes in regional HCT may produce errors in the calculation of regional blood flow unless the value of λ. is corrected to reflect altered HCT. Moreover, no matter what kind of indicator is used, our functional interpretation of regional blood flow measurements is dependent upon our assumption that the ‘blood’ in the region maintains a constant capacity to carry nutrients like oxygen. Thus the lack of a constant relationship between plasma flow and red cell flow may produce errors either in the measurement or interpretation of regional flow measurements. These errors will increase in importance as blood flow is measured in smaller and smaller volumes of brain.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

The critical Reynolds number, Rec, at which turbulence developed in glass model bifurcations was measured with an Evans blue indicator for bifurcations with a branch/trunk area ratio of unity, and bifurcation angles of 45°, 90°, 135°, and 180°. The Recdropped from 2,500 in a straight tube to 1,200 in the 180° bifurcation. Further drops occured with pulsatile flow (if the mean flow rate was used to calculate the velocity). Three sizes of aneurysms at the apex of the 90° bifurcation lowered the Recat small bifurcations, and less in the 180° ones. The curves for steady and pulsatile flow crossed at 135°. We did qualitative, but not quantitative, assessments of axial stream impingement on the apex of the bifurcation in the site of aneurysm formation, and of boundary layer separation and vortex shedding at the lateral angles. Both appeared to vary with the angle of the bifurcation and the Reynolds number. We also studied flow profiles in glass models of anterior cerebral-anterior communicating artery bifurcations and the posterior communicating artery origin from the internal carotid. The relevance of these studies to localization of intimal cushions, aneurysms, and atherosclerosis was discussed.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

In cats being subjected to surgical occlusion of the middle cerebral artery, regional oxygen availability (O2a) was monitored continuously from four open-tip platinum electrodes in the ischemic hemisphere and one in the control hemisphere. Extradural pressure over the convexity of the ischemic hemisphere was measured hourly. The animals were killed 24 hours after occlusion. Ten animals developing substantial increases in extradural pressure as a consequence of cerebral infarction were compared with ten which did not. The two groups did not differ in severity of the initial ischemic insult resulting from the arterial ligation, in blood pressure following occlusion, or in hematocrit, PCO2, or oxygen saturation.The most important difference between the two groups was in the course of regional O2a in the ischemic hemispheres following occlusion. In the animals which ultimately developed increased intracranial pressure the recovery of regional O2a was slower and less complete. After the ninth hour postocclusion O2a declined progressively, clearly related to rising intracranial pressure. In the animals which developed increased extradural pressure, it rose progressively to a mean of 40 mm Hg by 24 hours postocclusion. The intracranial pressure changes during the first few hours seemed insufficient to account for the early failure of recovery of regional O2a, unless they are viewed as averages which obscure important regional intracerebral pressure changes.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Average cerebral blood flow determinations were performed 26 times comparing argon desaturation curves measured by mass spectrometry to the krypton 85 desaturation technique of McHenry.1During 17 of these studies krypton 85 and argon desaturations were performed simultaneously. Mean cerebral blood flow difference was 7.2 ± 5.7% for simultaneous determinations and 7.9 ± 6.6% for the total, establishing that the two techniques are comparable. Some of the advantages of using argon in mass spectrometry include: no blood needs to be withdrawn, curves can be observed at the time they are obtained, radiation precautions are not required, multiple studies do not affect the patient, and partial pressures of oxygen and carbon dioxide can be observed constantly.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

In 30 patients with organic brain disorders, blood samples from both ear lobes were examined for their white cell contents. In nine of them, blood from the external and internal jugular veins also was examined. The total white cell, neutrophil, and eosinophil counts did not show any difference when the two sides of the head were compared; nor was there any difference in the average-of-sides values of these cells in cranial blood samples when compared with blood from a finger puncture, or when compared with ear lobe blood from ten healthy control subjects.Basophil values were lower in blood from the internal jugular veins than in blood from the external jugular veins, and basophils in ear lobe blood were at an intermediate level.In patients with one-sided cerebral lesions, fewer basophils were found on the focal side even when the lesions were remote in time. Monocyte levels were higher on the focal side during the first two months after a cerebrovascular attack.Patients with bilateral brain lesions had fewer basophils in ear lobe samples than normal controls but showed no side-related difference.A single intravenous injection of 5,000 units of heparin caused an existing bias in basophil and monocyte values between focal and opposite side to disappear and produced an increase in the cranial level of these cells. The side-related differences did not reappear for an average of three weeks.The findings with regard to the role of monocytes as precursors of cerebral macrophages and of basophils as carriers of heparin are discussed, and the examination of ear lobe blood is proposed as a noninvasive and simple method for hematological studies of cerebral disorders.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Values of total cerebral blood flow in man measured by the indicator dilution method are compared with values of total internal jugular venous flow measured by the thermal dilution method. Except in the case of an extremely labile cerebral hemodynamic state, the results agree within the accuracy of the two methods, suggesting that for the supine patient total internal jugular venous flow provides a good index of total cerebral flow.The relatively short measurement time associated with nondiffusible indicators (dye or thermal dilution) facilitates detection of transient changes in total CBF or differential jugular flow that would tend to be averaged out with diffusible indicator methods.A mathematical analysis of the potential errors in the computation of total flow using the average of bilateral jugular venous dilution curves from a unilateral internal carotid injection is presented. This error can be partially corrected if the ratio of flow in one internal jugular to total flow is known.An analysis of potential computational errors under nonsteady state flow conditions (change in flow during the period between alternate carotid injections) is presented. Such flow changes can effect substantial errors in the computation of individual hemispheric or internal jugular flow and smaller errors in the computation of total flow.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

An animal model has been developed for the continuous measurement of total cerebral blood flow in the unanesthetized, unrestrained goat. We selected the goat because each internal maxillary artery, a branch of the external carotid artery, provides the total blood flow to each hemisphere via the rete mirabile. After the occlusion of the extracerebral vessels of the internal maxillary artery with thrombin, an electromagnetic flow transducer was chronically implanted on this artery, distal to the temporal artery, to measure hemispheric blood flow. Reproducible measurements of cerebral blood flow were obtained in ten unanesthetized goats for periods ranging between two weeks and five months. The mean cerebral blood flow for the ten goats was 133 ± 5 ml/min/100 gm tissue at an average mean aortic pressure of 91 ± 3 mm Hg, heart rate of 79 ± 3 beats/min, arterial PCO2of 31.4 ± 1.0 mm Hg, P02of 76.6 ± 1.7 mm Hg, and pH of 7.48 ± 0.02. The present experimental preparation allows cerebrovascular hemodynamics to be evaluated under near-normal conditions and is suitable for physiological and pharmacological studies in normal and abnormal states.

ISSN:0039-2499    

出版商:OVID    

年代:1972

数据来源: OVID