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Biomedical subjects

T M Sundt

Publications and source records attributed to T M Sundt.

At least 199 records · Page 11Linked to original sources
PubMed1979

Intracellular redox states under halothane and barbiturate anesthesia in normal, ischemic, and anoxic monkey brain.

Cortical reflectance, mean arterial blood pressuees, electroencephalograms, and cortical blood flow were continuously recorded together with fluorescence of reduced pyridine nucleotides (PN) at various carbon dioxide tensions before, during, and following middle cerebral artery occlusion in 10 squirrel monkeys receiving halothane or babiturate anesthesia. Measurements were continued through a nitrogen breathing cycle and to death produced by anoxia. The anesthetic agent produced no detectable differences in PN fluorescence in cerebral tissue during ischemia and anoxia. The known cerebral protective action of barbiturates is apparently unrelated to the intracellular redox state.

Animals↗
PubMed1979

Surgical approach to giant intracranial aneurysms. Operative experience with 80 cases.

The authors report experience with the surgical management of 80 giant intracranial aneurysms (greater than 2.5 cm in diameter) during a 10-year period in which they performed 594 operations for aneurysms. The overall incidence of giant aneurysms was 13% but varied according to location: 20% of aneurysms of the internal carotid artery (ICA); 13% of middle cerebral artery (MCA) aneurysms; 1% of anterior cerebral artery (ACA) aneurysms; 15% of aneurysms of the basilar artery caput (BAC); and 18% of vertebrobasilar trunk (VB) aneurysms. Twenty-five patients had a subarachnoid hemorrhage (SAH), 49 had mass effect from the aneurysm, and six had ischemic events. There was no apparent difference in results related to the presence or absence of an SAH. Poor results were attributable to the operation except in the two cases of ACA aneurysm in which preexisting dementia persisted. Mortality was 4% and morbidity was 14%, varying from a combined low morbidity-mortality of 8% for ICA lesions to a high to 50% for BAC aneurysms. During the period of the study, different techniques were developed in an attempt to lower the risks of surgery. Ultimately ICA aneurysms were monitored with cerebral blood flow measurements and electroencephalography before and after temporary ICA ligation, then approached following resection of the anterior clinoid or treated with bypass in combination with ICA ligation. Aneurysms of the MCA were either opened during temporary MCA occlusion or resected in combination with a bypass procedure. Bypass grafts and circulatory arrest with extracorporeal circulation may have a role in giant aneurysms of the posterior circulation.

Brain Ischemia↗
PubMed1979

Arteriovenous malformation affecting the transverse dural venous sinus--an acquired lesion.

Dural arteriovenous malformations of the transverse sinus are relatively well localized to the occipitomastoid regions and occur predominantly in women who are more than 40 years of age. The signs and symptoms, except for pulsatile tinnitus, vary and apparently depend on the presence of impaired venous drainage, which may produce increased intracranial pressure, papilledema, and transient or persistent neurologic deficits. Eight of the 14 patients described had occlusion of one or both transverse or sigmoid sinuses. Two patients had angiographic demonstration of sigmoid or transverse sinus occlusion (one 1 year and the other 4 years) before the development of an arteriovenous malformation in the appropriate sinus. Dural sinus occlusion may precede the development of a dural arteriovenous malformation, and the pathogenesis may be partial recanalization of a thrombus.

Adult↗
PubMed1979

The ocular aspects of bypass surgery of the carotid artery.

A new neurosurgical procedure, anastomosis of the superficial temporal artery to the middle cerebral artery, is being performed with increasing frequency. Over a 7-year period (1971 through 1977), 121 patients have undergone this operation in our institution. Ophthalmodynamometry may be of great help in identifying occlusion of an internal carotid artery. Progressing venous stasis retinopathy and ischemic orbital pain are believed to be indications for bypass surgery of the carotid artery.

Arterial Occlusive Diseases↗
PubMed1978

Subarachnoid hemorrhage from intracranial aneurysms. Surgical management and natural history of disease.

We analyzed the management of 310 patients with acute subarachnoid hemorrhage from a ruptured intracranial aneurysm, 280 of whom survived to operation, according to preoperative neurologic function, location and size of the aneurysm and timing of operation. Severe initial bleeding, rebleeding (usually within two weeks) and delayed ischemia were major preoperative problems; 10 per cent died, and 13 per cent deteriorated before operation. Operative mortality was 5 per cent, ranging from 1.6 per cent of patients with normal preoperative neurologic function to 35 per cent of severely disabled patients. Intraoperative complications (5 per cent of cases) related chiefly to the size and location of the aneurysm, but postoperative delayed ischemia (minor and reversible in 10 per cent and severe in 5 per cent) related to timing of operation and occurred primarily in patients afflicted within the previous 10 days. The results of surgical treatment, including preoperative deaths, were better than the natural history of the illness, the difference being apparent after one month's observation.

Follow-Up Studies↗
PubMed1978

Intracranial arteriovenous malformations in childhood.

During the 13-year period 1964 through 1976, 37 patients less than 20 years with an intracranial, parenchymal arteriovenous fistula were seen at the Mayo Clinic. The most frequent mode of presentation was hemorrhage or seizure. Other than angiography, computed tomography with contrast enhancement was the most helpful diagnostic test. Surgery was restricted to patients with intraparenchymal hematomas, intractable seizures, or subarachnoid hemorrhage with accessible lesions and to 1 infant with a massive, sumptomatic malformation. Surgery generally was tolerated well, with reversal of most acute focal neurological deficits related to hematomas. In the nonsurgical group, follow-up revealed a fairly stable neurological status during the period of the study.

Adolescent↗
PubMed1978

Comparison of dark-field and bright-field incident illumination for in vivo measurements of reduced pyridine nucleotides.

Bright-field and dark-field illumination techniques for in vivo measurements of reduced pyridine nucleotide fluorescence were compared in 15 rats during periods of normocapnia, hypocapnia, hypercapnia, and anoxia. Parameters investigated included fluorescence, cortical reflectance, cortical blood flow, and electroencephalograms. In normal brain, with preserved autoregulation, reduced pyridine nucleotide fluorescence was constant through a wide range in Pa(CO2), cortical blood flow, and cerebral blood volume in animals studied using vertical illumination (bright-field) techniques. There was a marked increase in reduced pyridine nucleotide fluorescence at death from anoxia. Artifacts were reduced by monochromators for excitation, emission, and reflected light; low-intensity vertical excitation energy and high-sensitivity recording instrumentation; and a small avascular (123 microns) field. Potential sources of error include photodecomposition, hemoglobin interference from absorption and reflectance, and light scattering. Vertical excitation techniques using a small field appeared to give more reliable and reproducible results than circumferential techniques using a larger field of observation.

Animals↗
PubMed1978

Ultrastructural changes in feline arterial endothelium following subarachnoid hemorrhage.

Scanning electron microscopy of feline basilar arterial endothelium 4 hours, and 1, 3,5, and 7 days after subarachnoid hemorrhage (SAH) showed longitudinal furrows that correlated with angiographically demonstrated vasospasm. These ridges persisted after fixation at physiological pressure, and probably reflected medial contraction with undulation of the underlying elastic lamina. No change in endothelial cell morphology or thrombogenesis was observed as long as 7 days after SAH. There is no evidence from this study to suggest that ischemia from vasospasm is a product of thromboembolism from damaged endothelial surfaces.

Animals↗
PubMed1978

Carotid endarterectomy. Temporal profile of the healing process and effects of anticoagulation therapy.

The healing of the canine carotid endarterectomy was defined at intervals from 30 minutes to 3 months after surgery by means of angiography, light microscopy, and scanning electron microscopy. Immediately after flow was established, a fibrinplatelet carpet formed on the endarterectomized surface. A typical thrombus formed on this initial layer resulting in vessel occlusion in 52% of non-heparinized animals. By 48 hours after surgery, there was little evidence of active thrombus formation, and reendothelialization from existing endothelial cells was noted. One week later, most of the mural thrombus had disappeared and re-endothelialization was well underway; by 3 months after surgery, re-endothelialization was complete. Intraoperative heparinization resulted in a striking reduction in mural thrombus formation and 100% patency rate. Vessel closure with vein-patch grafts resulted in no improvement of vessel patency. However, the results of this aspect of the study cannot be totally extrapolated to human carotid endarterectomy for the reasons discussed. The survival of the vein-patch grafts was investigated.

Animals↗
PubMed1978

Occipital to posterior inferior cerebellar artery bypass surgery.

The results, complications, and technical aspects of occipital to posterior inferior cerebellar artery (PICA) bypass surgery are reviewed. Patients were divided into two groups: those considered to be a high risk for posterior circulation infarct but not disabled by the symptoms or deficits (eight patients), and those moderately or severely disabled at the time of admission (eight patients). Postoperative angiography revealed that 15 of the 16 grafts were patent. In 10 of the 15 patent grafts, the bypass graft served as a sole or major blood supply of the vertebral basilar system; in five patients, flow was limited to the distribution of the PICA. Eight patients achieved full employment or normal activity, six were improved but did not return to full employment, and two patients were unchanged. Ataxia was the major residual deficit in these patients.

Adult↗
PubMed1978

Interrelationship of aneurysm clips and vascular tissue.

Various straight-jawed aneurysm clips were tested for occluding capabilities on a vascular tissue model. Occluding pressures varied markedly among the clip styles and were altered by changes in the lumen and tissue composition of the model. Mechanical characteristics are highly variable between clip styles, but fall within a narrow range for clips of a similar style. The complex interplay of the unique aspects of clip design and force generated by the spring in conjunction with tissue characteristics and precise clip placement upon the tissue are major variables in the apparent ability of a particular clip to occlude the neck of an aneurysm.

Animals↗
PubMed1978

Guidelines for the management of transient ischemic attacks.

On the basis of a review of the literature on anticoagulant, antiplatelet, and surgical treatment, supplemented by our personal experience, we have developed guidelines for the management of patients with transient ischemic attacks (TIA). 1. The majority of patients with vertebral-basilar TIA are treated medically. 2. If a skilled surgeon and an experienced angiographer are available, patients with typical carotid TIA who are suitable medical risks should have angiography followed by carotid endarterectomy if an appropriate lesion is found. 3. Nonoperated patients with TIA of less than 2 months' duration are treated with 3 months of warfarin therapy (unless contraindicated) before treatment with aspirin is begun. 4. Nonoperated patients with continuing TIA of 2 or more months' duration are treated with aspirin unless there has been a recent increase in the frequency, duration, or severity of TIA. Under these circumstances, warfarin therapy is advised for 3 months before aspirin is started. Aspirin therapy should be continued until the patient has been free of TIA for 1 year. 5. No treatment is advised for nonoperated patients whose last episode of TIA was longer than 12 months ago.

Anticoagulants↗
PubMed1978

Intracranial bypass grafts for vertebral-basilar ischemia.

Fourteen operations in which an occipital branch of the external carotid artery was anastomosed to the posterior inferior cerebellar artery were performed for occlusions or inaccessible stenotic lesions of the vertebral arteries proximal to the site of origin of the posterior inferior cerebellar artery. Eight patients (group 1) had no major focal reurologic deficit but were considered to be at high risk for a posterior circulation infarct; six patients (group 2) had been severely or moderately disabled before the operation. Postoperative angiography revealed that 13 of the 14 grafts were patent. In 9 of the 13 patent grafts, the bypass graft served as the sole or major blood supply of the vertebral-basilar system; in 4, flow was limited to the distribution of the posterior inferior cerebellar artery. Five of the eight patients in group 1 have returned to full employment or normal retired life. Two of the six patients in group 2 have resumed normal activities with only minimal neurologic dysfunction. This procedure may have a role in the management of highly selected patients suffering from vertebral-basilar ischemia, and it may be useful in the management of selected aneurysms in the vertebral-basilar system.

Arteries↗
PubMed1978

The ocular aspects of carotid artery bypass surgery.

A new neurosurgical procedure, anastomosis of the superficial temporal artery to the middle cerebral artery, is being performed with increasing frequency. Over a 7-year period (1971 through 1977), 121 patients have undergone this operation in our institution. Ophthalmodynamometry may be of great help in identifying occlusion of an internal carotid artery. Progressing venous stasis retinopathy and ischemic orbital pain are believed to be indications for bypass surgery of the carotid artery.

Blood Pressure↗
PubMed1977

The effect of lesions in the locus coeruleus on the physiological responses of the cerebral blood vessels in cats.

The effects of cerebral blood flow (CBF) of lesions placed stereotactically in or near the locus coeruleus were studied in 15 lightly anesthetized cats; 5 control cats in which the electrode was placed but no lesion created, and 10 experimental cats in which a lesion was created. The response of CBF to changes in Paco2 and in mean arterial blood pressure was determined by 133Xe-washout studies 10 days after the stereotactic procedures. The sites of the lesions were studied histologically, and their effects on catecholamine concentrations in the paraventricular hypothalamic nucleus, anterior ventral nucleus of the thalamus, and parietal cortex were determined by radio-chemical assay. Control animals and those with lesions near, but not in, the locus coeruleus had normal Paco2--CBF response curves and normal catecholamine concentrations in the areas of biopsy. Bilateral destruction of the locus coeruleus was confirmed in 3 animals on histological examination and in these animals there were decreased levels of catecholamines in the areas of assay, higher resting CBFs at normocapnia, and significantly abnormal CBF--Paco2 response curves. The autoregulatory response to changes in perfusion pressure was preserved. Thus, noradrenergic neurons originating in the locus coeruleus may contribute to the control of intraparenchymal cerebral vessels and disturbance of this control may be important in the pathology of cerebral ischemia.

Animals↗