Search results for "Blood flow"
showing 10 items of 568 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…
Relationship of Cerebral Blood Flow Disturbances with Brain Oedema Formation
1993
Brain oedema is an important factor which compromises maintenance of the cerebral blood flow. Conversely, primary blood flow disturbances are leading to brain oedema. The mechanisms underlying blood flow impairment by brain oedema are associated with an increased regional tissue pressure in proportion to the degree of water accumulation in the parenchyma. The release of vasoactive mediator compounds might be considered in addition. Primary disturbances of the cerebral blood flow, such as focal or global cerebral ischaemia are leading to an increased cerebral water content. A decrease of the cerebral blood flow to ca. 40% of normal or below has been found to result in the development of brai…
Role of Ischemia/Reperfusion Injury in Organ Transplantation
1997
Reperfusion of oxygenated blood into previously ischemic tissue is essential to prevent the progression of cellular injury due to the decreased nutritional blood flow, i.e., the decreased delivery of oxygen and metabolic substrates, as well as the removal of harmful metabolic byproducts. However, it has become obvious that reperfusion also initiates a complex series of pathologic events that contribute to, rather than prevent, further tissue damage. Moreover, a growing body of evidence indicates that ischemia/reperfusion injury is initiated by events that occur at the level of the microcirculation. In the first part of this overview, we will delineate the major components of the microcircul…
“Small Volume Resuscitation” as Treatment of Cerebral Blood Flow Disturbances and Increased ICP in Trauma and Ischemia
1996
“Small volume resuscitation” (SVR) is a promising concept for the treatment of shock and trauma patients. SVR utilizes the fast infusion of a small volume of hypertonic saline to mobilize intraendothelial and parenchymal water to expand and restitute intravascular volume. Therefore it seems warranted to also consider SVR for the treatment of disturbances of the cerebral circulation and of increased intracranial pressure (ICP). The current study uses a rabbit model of global cerebral ischemia combined with mild hemorrhage to test SVR. Somatosensory evoked potentials (SEPs) serve as a short-term outcome parameter. The data demonstrate a beneficial effect on ICP, a better reperfusion, and an i…
Normalwerterstellung von Blutströmungsgeschwindigkeiten an der Arteria mesenterica superior bei Früh- und Reifgeborenen mit der Duplexsonographie
1994
In a prospective study blood flow velocity measurements were performed in 110 "healthy" newborn with duplex Doppler sonography in the superior mesenteric artery to obtain standard values. In 49 of these neonates 15, 30, and 45 minutes following feeding examinations were performed. Peak systolic flow velocity, end systolic flow velocity, time average flow velocity and time average maximum flow velocity were determined, the resistance and Pourcelot index as well as the volume blood flow were calculated. The children's gestational age was 27-42 weeks, the postnatal age was 2-68 days and the body weight was 920-4190 g. All measured blood flow velocities showed a synchronous relation to feeding …