Search results for "Flow"
showing 10 items of 5185 documents
Possible Adverse Effects of Hyperventilation on rCBF during the Acute Phase of Total Proximal Occlusion of a Main Cerebral Artery
1969
Recent studies seem to favor a beneficial effect of hyperventilation (HV) in cases of cerebrovascular occlusion [1, 4] and brain trauma [2, 5]. On the other hand, it seems that, at least under certain circumstances, HV may exert an adverse effect upon cerebral blood flow and metabolism [3]. Since this question is not settled yet, it seems worthwhile to report briefly the present case of reversible total occlusion of the middle cerebral artery closely followed by successive rCBF studies (133Xe-gamma-clearance method), in which, during the acute phase, HV caused a latent ischemia to become manifest.
Cessation of Cerebral Blood Flow in Total Irreversible Loss of Brain Function
1969
After the demonstration, by our group [3, 4], that in cases of so-called “cerebral death” there is an absence of clearance from the brain of 133Xe selectively injected into the internal carotid artery, further attention was dedicated to establish possible sources of error in this technique.
Neuronal immunoreactivity for mannose-binding lectin after venous occlusion-induced focal cerebral ischemia in rats
2012
Abstract A recent research reveals that complement activation exacerbates cerebral infarction. However, involvement of the lectin pathway, (the third complement activation pathway) in cerebral ischemia is not well studied. In this study, we investigated the appearance of mannose-binding lectin (MBL) in ischemic brain tissue. Male Wistar rats ( n = 25) were divided into three groups: untreated control, sham, and vein occlusion (VO). Rats in the VO group had two adjacent photochemically occluded cortical veins. Regional cerebral blood flow (rCBF) was measured in the sham and VO groups. Rats were perfusion-fixed at 72 h in the sham group and at 3, 24, and 72 h after inducing ischemia in the V…
The effects of arterial CO2 on the injured brain: Two faces of the same coin
2021
Serum levels of carbon dioxide (CO2) closely regulate cerebral blood flow (CBF) and actively participate in different aspects of brain physiology such as hemodynamics, oxygenation, and metabolism. Fluctuations in the partial pressure of arterial CO2 (PaCO2) modify the aforementioned variables, and at the same time influence physiologic parameters in organs such as the lungs, heart, kidneys, and the gastrointestinal tract. In general, during acute brain injury (ABI), maintaining normal PaCO2 is the target to be achieved. Both hypercapnia and hypocapnia may comprise secondary insults and should be avoided during ABI. The risks of hypocapnia mostly outweigh the potential benefits. Therefore, i…
Vasomotor reactivity in dementia of alzheimer type
1994
The objective of this study was to examine the cerebral blood flow and the vasomotor function of CO2-responsive intracerebral vessels in Alzheimer's disease. Patients met DSM-III-R criteria for dementia of Alzheimer type and had neither symptoms nor signs of cardiovascular or cerebrovascular disease. Blood flow velocities in both middle cerebral arteries (MCA) were recorded using transcranial Doppler sonography during hypercapnia, normocapnia and hypocapnia. Several psychometric tests were performed. Patients' age, disease duration and severity of dementia did not correlate with vasomotor reactivity. Exploratory analysis revealed that mean flow velocities under hypercapnia correlated with s…
Precapillary Servo Control of Blood Pressure and Postcapillary Adjustment of Flow to Tissue Metabolic Status
1996
Background There are several shortcomings in current understanding of how the microvasculature maintains tissue homeostasis. Presently unresolved issues include (1) integration of the potentially conflicting needs for capillary perfusion and hydrostatic pressure regulation, (2) an understanding of signal transmission pathways for conveying information about tissue energetic status from undersupplied tissue sites to the arterioles, (3) accounting for the experimentally observed interrelations between precapillary and postcapillary resistances, and (4) an explanation of how precise local adjustment of perfusion to metabolic demands is achieved. Methods and Results A novel conceptualization o…
A Normal Fractional and Coronary Flow Reserve
2016
Fractional flow reserve (FFR) and coronary flow reserve (CFR) provide different and complementary information on vascular physiology. The two tests provide information, respectively, on the epicardial and total vascular resistances. Typically, a FFR <0.75 is also associated with an impaired CFR (<2); exceptions, however, exist.
87Non-invasive virtual prediction of site of origin in outflow tract ventricular arrhythmias with a patient-specific computational model
2017
A Complex Combination of Microvascular and Macrovascular Diseases
2016
When FFR is larger than 0.80, a PCI is not justified. Transient microvascular dysfunction may, however, be associated with impaired hyperemia and falsely negative FFR. This case also emphasizes the dynamic nature of microvascular disease, and provides an example of both “typical” syndrome X and “less conventional” syndrome slow flow associated with increased peripheral resistances (see Chap. 35).