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T M Sundt

Publications and source records attributed to T M Sundt.

282 records · Page 16Linked to original sources
PubMedDate not supplied

Blood flow measurements and the "look through" artifact in focal cerebral ischemia.

Regional cerebral blood flow (CBF) was measured (intra-arterial injections of 133Xe) and electroencephalograms (EEG) were recorded periodically before, for two hours during, and for one and one-fourth hours after middle cerebral artery (MCA) occlusion in 20 squirrel monkeys (Saimiri sciureus). A CBF-Paco2 response curve for these animals under barbiturate anesthesia was created from CBF values prior to MCA occlusion and during the time a steady state was being achieved. The animals were subdivided into four groups (five monkeys in each) on the basis of Paco 2 values: 20, 36, 40, and 60 mm Hg. CBF values from this study were compared to previous results obtained with 85Kr. The phenomenon of "look through" and the importance of recognizing this artifact and its significance in analyzing CBF results in areas of focal ischemia are discussed. The present results were correlated with cerebral ATP and lactate concentrations in ischemic regions determined in previous studies using this preparation at these Paco2 values and at comparable time intervals before, during, and after MCA occlusion. The EEG appears to reflect the state of ischemic brain accurately. However, CBF measured by the 133Xe method can be misleading in regard to the true degree of ischemia resulting from occlusion of an intracranial vessel and cannot be relied on to demonstrate accurately "steal" or "reverse steal" due to changes in Paco2.

Acid-Base Equilibrium↗
PubMedDate not supplied

Reduced nicotinamide adenine dinucleotide fluorescence and cortical blood flow in ischemic and nonischemic squirrel monkey cortex. 1. animal preparation, instrumentation, and validity of model.

Reduce nicotinamide adenine dinucleotide (NADH) fluorescence was recorded from an avascular area on the squirrel monkey cortex prior to, during, and after focal incomplete ischemia. By using the instrumentation described, stable recordings were obtained free from hemoglobin artifact and with only minimal photodecomposition. Pentobarital was compared to urethane and halothane as the anesthetic agent and was found acceptable for these types of studies in the dosages used. NADH levels were constant prior to ischemia, increased during ischemia, returned to pre-ischemic levels after restoration of blood flow, and then increased greatly at death produced by anoxia. The use of the infrared microscope for semiquantitative measurements of cortical blood flow throughout the duration of these acute studies was investigated and found to the reliable.

Animals↗
PubMedDate not supplied

Reduced nicotinamide adenine dinucleotide fluorescence and cortical blood flow in ischemic and nonischemic squirrel monkey cortex. 2. effects of alterations in arterial carbon dioxide tension, blood pressure, and blood volume.

The fluorescence of reduced nicotinamide adenine dinucleotide (NADH) from cerebral cortex was measured before, during, and after middle cerebral artery (MCA) occlusion and then at death of the animal. In normal cortex, NADH remained constant throughout a wide range of variations in blood pressure and Paco2. In ischemic cortex, NADH levels were higher in hypovolemic hypotensive animals than in normotensive normovolemic animals. Neither hypercapnia nor hypocapnia was effective in decreasing NADH in regions of ischemia, but the latter was associated with a degree of hypotension that interfered with interpretation of data. NADH returned to normal with restoration of flow, supporting the reversibility of this degree of ischemia. The high levels of NADH at death, compared to those during ischemia, are consistent with incomplete ischemia in this model of cerebral infarction.

Animals↗
PubMedDate not supplied

Influence of cerebral vasoconstricting and vasodilating agents on blood flow in regions of focal ischemia.

Regional cerebral blood flow (rCBF) measurements with krypton-85 (100 separate determinations) were compared in squirrel monkeys anesthetized with sodium pentobarbital (a cerebral vasoconstrictor) and halothane (a cerebral vasodilator) before, during, and after middle cerebral artery (MCA) occlusion. Prior to MCA occlusion, a normal physiological response to alterations in arterial carbon dioxide tensions (Paco2) was demonstrated in both groups of monkeys; the cerebral vascular resistance was significantly lower in those anesthetized with halothane. During ischemia, there was loss of autoregulation and a failure to respond to alterations in Paco2 in both groups. Flow in the ischemic region remained uniform in the barbiturate group but decreased progressively in the halothane group, suggesting a "paradoxical response" to the dilating agent. Reactive hyperemia (luxury perfusion) was demonstrated in both groups after restoration of flow. The use of a beta-emitting isotope ensured that measurements in regions of ischemia accurately reflected rCBF and were free of the artifacts ("look through" and Compton scatter) related to use of a gamma-emitting indicator.

Animals↗
PubMedDate not supplied

XIII. Cerebral circulation and metabolism in stroke. Cerebral circulation and metabolism in stroke study group.

An understanding of the cerebral circulation is so fundamental to comprehension of the pathogenesis of stroke that cerebral blood flow and metabolism merit review in this series of reports. The authors recognize that the research described here is very technical in nature and may appear to have little practical application to clinical medicine. Nevertheless, these matters are basic to the development of precise methods for the measurement of regional cerebral blood flow in man which could be used to monitor the therapy of stroke with greater success than is possible at present.

Brain↗
PubMedDate not supplied

Effect of anticoagulants and inhibitors of platelet aggregation on thrombotic occlusion of endarterectomized cat carotid arteries.

Cat carotid arteries measuring 1.8 to 2 mm in diameter were endarterectomized under the operating microscope over a 1-cm segment and the arteriotomy was closed with a 9-0 monofilament nylon suture. Vessels exhibiting significant narrowing of the lumen due to faulty closure of the arteriotomy were excluded from the study. The vessels were divided into six groups according to the method of treatment of the animals: control, aspirin, Coumadin, Coumadin plus aspirin, heparin for less than four hours, and heparin for four to eight hours. All vessels in the untreated group subjected to simple arteriotomy and closure remained patent. Only heparin demonstrated an apparent beneficial effect after endarterectomy with 100% of the vessels treated more than four hours and 30% of those treated less than four hours remaining patent. This is contrasted to a 0% patency in other endarterectomized vessels.

Animals↗
PubMedDate not supplied

Ectopic internal carotid artery seen initially as middle ear tumor.

An ectopic carotid artery is rare. Its first symptoms may be neurological and could bring the patient to the neurologist during the initial evaluation. However, more often, the neurologist examines a patient in whom serious neurological deficit has occurred after transtympanic exploration of an undiagnosed vascular mass. Because diagnosis can be definitively established by angiography and the consequences of injury to an aberrant carotid artery are serious, operative exploration of vascular middle ear masses probably should be deferred until an ectopic carotid artery has been excluded by angiography.

Adult↗
PubMedDate not supplied

Spontaneous cervical cephalic arterial dissection and its residuum: angiographic spectrum.

Cervical cephalic dissections are uncommon acute disruptions of the arterial wall occurring predominantly in middle-aged women. Clinically, most patients present with unilateral headache, oculosympathetic palsy, or ischemic neurologic symptoms. Usually, a single internal carotid artery, predominantly the right, is affected, but simultaneous multivessel dissections are evident in about one-third of patients. Angiographically, the appearance of the dissection varies, depending on its severity, extent, and the interval between onset and angiography. In the patients reported, the disruption was manifested initially by eccentric tapered stenosis in 47%, tapered stenosis and a dissecting aneurysm in 28%, occlusion in 18%, or a dissecting aneurysm alone in 7%. Subsequently, stenotic dissections resolved in 60%, improved in 20%, and progressed in 15%, while dissecting aneurysms diminished in half and resolved in one-fourth of patients. An angiographic residuum, temporally remote to its onset, was evident in 25% of dissections. Hence, carotid arterial dissections tend to resolve, sometimes progress, but seldom recur.

Adult↗