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Biomedical subjects

T M Sundt

Publications and source records attributed to T M Sundt.

At least 181 records · Page 10Linked to original sources
PubMed1982

Extracranial internal carotid artery aneurysms.

Extracranial internal carotid artery aneurysms are uncommon. The symptoms of these aneurysms vary according to their location and size. Larger aneurysms may present as cervical or parapharyngeal masses, which may or may not be pulsatile or tender; there may be an associated systolic bruit. Pharyngeal hemorrhage, epistaxis, or bleeding from the ear are rare manifestations. Ischemic symptoms are a frequent mode of presentation of these aneurysms. Arterial diseases, particularly atherosclerosis, may predispose the vessel to the formation of the aneurysm. Sometimes trauma is the cause. We report herein six cases of extracranial internal carotid artery aneurysms. The modes of presentation, the etiologic factors, the pathologic observations, and the methods of management are discussed, and the pertinent literature is reviewed.

Adult↗
PubMed1982

Aneurysmal subarachnoid hemorrhage: timing of surgery and mortality.

In contrast to the incidence of other types of stroke, the incidence of aneurysmal subarachnoid hemorrhage has not changed. It is highest in the oldest age groups, and this indicates that it is not due to a congenital lesion. The primary factors that affect survival after aneurysmal subarachnoid hemorrhage are the clinical grade of the patient and the duration of time from onset to the time the patient is seen for medical attention. Because of the very high early mortality from aneurysmal subarachnoid hemorrhage, surgeons generally wait until 10 to 14 days before undertaking surgery. This delay results in a lower surgical mortality but makes it difficult to show an effect on overall mortality. Increasing attention is being given to early surgery after aneurysmal subarachnoid hemorrhage.

Age Factors↗
PubMed1981

Correlation of brain blood flow, intracellular pH and metabolism in hypoglycemic cats under halothane and barbiturate anesthesia.

The neurophysiological alterations associated with transient insulin-induced hypoglycemia were compared in 14 cats anesthetized with halothane and 14 cats anesthetized with pentobarbital fasted for 18 h prior to the study. Each anesthetic group was further divided into acute and chronic preparations which in turn were prepared and studied in an identical manner except for the anesthetic agent employed. In the chronic animals there was no difference in survival between the two groups following a 2-h period of hypoglycemia. In these preparations there were no significant differences in: blood glucose levels, mean arterial blood pressure (MABP); arterial carbon dioxide tension (paCO2), arterial oxygen tensions (paO2), arterial pH (pHa), or acid-base balance during the period of hypoglycemia. Differences in the electroencephalograms were commensurate with the anesthetic used. In the acute preparations cerebral blood flow (CBF), xenon-133 clearance technique; brain pH, pH sensitive fluorescent indicator method; and cerebral metabolic rates of oxygen (CMRO2) and glucose consumption were determined at 15-min intervals in addition to the measurements recorded in the chronic group. During a 3-h period of regular insulin administration at a rate of 30 units/kg/h there were no significant differences in any of the systemic or brain measurements recorded except for CBF (halothane greater than barbiturate). EEGs in the acute group of animals paralleled the chronic group and improved but did not return to normal following glucose resuscitation at the end of the period of hypoglycemia. All the acute animals had a normal paCO2-CBF response curve prior to the insulin administration. CBF and brain pH remained constant during the period of hypoglycemia in both groups. However, following the administration of glucose there was a significant brain acidosis and EEG change without a change in CBF. We conclude that: the protective effects of barbiturates in states of hypoxemia or ischemia do not extend to hypoglycemia, brain pH and blood flow are not altered by moderate (as opposed to severe) hypoglycemia, and brain pH may not be the prime regulator in the CBF-metabolic blood flow couple.

Acid-Base Equilibrium↗
PubMed1981

Giant traumatic false aneurysm of the internal carotid artery associated with a carotid-cavernous fistula. Case report.

A case of giant traumatic false aneurysm of the intracranial internal carotid artery (ICA) with a concomitant carotid-cavernous fistula is reported. The fistula and the aneurysm persisted after ipsilateral cervical ICA ligation was performed elsewhere. Successful obliteration of the aneurysm and the fistula, with preservation of cross filling of the ipsilateral middle cerebral artery system, was accomplished by ligation of the intracranial ICA proximal to the origin of the posterior communicating artery with a 7-0 prolene suture, followed by transaneurysmal packing of the fistula.

Adolescent↗
PubMed1980

Intracellular brain pH and the pathway of a fat soluble pH indicator across the blood-brain barrier.

Umbelliferone, a pH sensitive fluorescent indicator, can be used to determine intracellular pH measurements and analyze the pathway of a fat soluble substance across the blood--brain barrier (BBB). The 'equivalent intracellular pH' determined by this technique corresponds closely with the calculated intracellular pH derived from mathematical abstractions. The pH of the indicator's environment along its pathway into and out of brain tissue can be determined from a ratio analysis of various points along the calibrated fluorescent tissue clearance curves from 340 and 370 nm excitation. This analysis indicates that immediately upon leaving the intravascular space the indicator enters an environment that is too acid to represent the extracellular space. This suggests that fat soluble substances follow an intracellular pathway across the BBB (capillary endothelium to glial cell to neuron).

Animals↗
PubMed1980

Correlation of intracellular redox states and pH with blood flow in primary and secondary seizure foci.

Epileptogenic foci were created by topical application of penicillin to the cerebral cortex in 40 paralyzed and artificially ventilated cats receiving halothane anesthesia. The animals were divided into two equal groups to compare primary and secondary foci. The following variables were recorded at normocapnia, hypocapnia, and hypercapnia prior to and during seizure activity: cerebral blood flow (CBF), determined by clearance of xenon 133; cortical redox states, measured by the fluorescence of reduced pyridine nucleotides (PN); brain pH, measured using a lipid-soluble, pH-sensitive fluorescent indicator; and electroencephalograms (EEG). Mean arterial blood pressure, arterial pH, arterial carbon dioxide tension (PaCO2), and arterial oxygen tension (PaO2) were monitored in each animal. All animals had a normal PaCO2-CBF response prior to the creation of a seizure focus, assuring the presence of autoregulation and normal metabolic function. CBF increased equally with seizures in the primary and secondary hemispheres. The relative increase was related to the PaCO2 but approximated 68% at normocapnia. There was an alteration in the PaCO2-CBF response with seizures, but the ability of the cerebral vasculature to constrict and dilate with hypocapnia and hypercapnia was retained. There was no significant difference in the reduced PN signal with variations in PaCO2 prior to seizures, but there was an apparent 10 to 15% fall with seizures. The "equivalent" intracellular pH fell to 6.94 at normocapnia in the primary focus but remained essentially unchanged from the control value of 7.10 in the secondary focus. These differences in pH were consistent with the greater degree of seizure activity observed in the primary focus. We conclude that a nonhypoxic acidosis existed in the primary focus and that changes in CBF were not related to it because the CBF changed equally in both hemispheres.

Animals↗
PubMed1980

Brain intracellular pH, blood flow, and blood--brain barrier differences with barbiturate and halothane anesthesia in the cat.

The effects of various depths of barbiturate and halothane anesthesia and different arterial blood carbon dioxide tensions (PaCO2) at uniform levels of anesthesia on brain pH, tissue indicator perfusion, and blood flow were studied in 40 cats. Brain pH was measured using a lipid-soluble, pH-sensitive fluorescent indicator (umbelliferone), and its clearance was determined from the slope of its washout curve. Cerebral blood flow (CBF) was determined from the clearance of intra-arterially injected xenon-133. Values for CBF were higher in the halothane-exposed group, and with deep anesthesia they did not decrease as much as did those seen with pentobarbital (47 vs. 27 ml/100 g/min). The barbiturate brain pH-arterial blood PaCO2 regression line had a steeper slope than the corresponding halothane line. The two lines crossed at PaCO2 42 torr and brain pH 7.15. Brain pH was directly related to both PaCO2 and depth of anesthesia in the halothane-exposed group but only to PaCO2 in the barbiturate-exposed group. If light halothane anesthesia (0.1 per cent) can be considered almost equivalent to the waking state, then both anesthetics produce relative brain alkalinity. The clearance of the pH indicator was only modestly sensitive to changes in PaCO2 at anesthetic levels of pentobarbital and halothane. It was not significantly changed by increasing the amount of pentobarbital. However, increasing levels of halothane produced a decrease of more than 50 per cent in its clearance (63 ml/100 g/min at 0.1 per cent vs. 29 ml/100 g/min at 3 per cent). It is concluded that umbelliferone provides a reliable method for the measurement of brain pH and possibly a useful tool for studies of the blood-brain barrier.

Anesthesia, General↗
PubMed1980

The unchanging pattern of subarachnoid hemorrhage in a community.

The average annual incidence of subarachnoid hemorrhage (SAH) from aneurysm rupture in Rochester, Minnesota, has remained remarkably constant at about 11 per 100,000 population. Age-specific incidence increased with age. Survival after SAH depended on: (1) clinical grade, (2) time after onset of SAH, and (3) presence of intracerebral hematoma. Among those who survived to receive medical attention, 48% were clinical grade 1 or 2, 20% were grade 3, and 32% were grade 4 or 5. Proved rebleeding occurred within 10 days of the first SAH in 20% of patients who survived until hospital admission.

Adolescent↗
PubMed1980

Treatment of intracavernous and giant carotid aneurysms by combined internal carotid ligation and extra- to intracranial bypass.

Ten patients with intracranial internal carotid artery (ICA) aneurysms were managed by combining ICA ligation with an extracranial to intracranial bypass procedure. Nine of these grafts were proven patient by angiogram. One patient was unable to return for postoperative angiograms; his graft ahd appeared patent on physical examination. Seven aneurysms were intracavernous, two were giant carotid-ophthalmic aneurysms, and one aneurysm was at the intracranial bifurcation of the ICA. Despite occlusion cerebral blood flow (CBF) measurements of 20 ml/100 gm/min or less in six patients, only one patient was unable to tolerate ICA ligation. Three patients developed transient aphasia, but there were no permanent neurological deficits associated with the carotid occlusion. Seven patients had improvement in pre-existing extraocular palsies or visual field defects. Others remained stable. The combination of an extracranial to intracranial microvascular bypass procedure with ICA ligation seems to be an effective method of treatment for aneurysms near the base of the skull that cannot be obliterated by a direct intracranial approach. The addition of the bypass procedure permits ICA ligation in patients who would not otherwise have tolerated occlusion of that vessel. Intraoperative xenon CBF measurements are an important adjunct to the operation.

Carotid Artery Diseases↗
PubMed1980

Relationship of cerebral blood flow to cardiac output, mean arterial pressure, blood volume, and alpha and beta blockade in cats.

The relationship among cerebral blood flow (CBF), blood volume, cardiac output (CO), and mean arterial blood pressure (MABP) at varying levels of arterial CO2 tensions (PaCO2) were studied in 70 normal cats. The CBF was measured from the clearance curve of xenon-133 and CO with a thermal dilution catheter placed in the pulmonary artery. The CBF, CO, and MABP values varied appropriately with changes in PaCO2, confirming the reliability of the preparations and the presence of normal autoregulatory responses. Moderate hypovolemia that did not change MABP did, nevertheless, significantly decrease CO and CBF. In an effort to determine if this decrease in CO and CBF were coupled responses, the effects of beta stimulation, hypervolemia, and alpha and beta blockade were investigated. Propranolol, in a dosage insufficient to change MABP, decreased both CO and CBF. This agent abolished the CO response to elevations in PaCO2 but not the CBF response, making it unlikely that this CBF reduction resulted from impaired cerebral autoregulation. Isoproterenol, which, in contrast to propranolol, does not cross the normal blood-brain barrier, alone or in combination with phenoxybenzamine, produced a 38% and 72% increase in CO, respectively, without a change in CBF. Alpha blockade (no major change in CO) and beta blockage (major decrease in CO) did not significantly effect cerebral autoregulation to changes in MABP from angiotensin. The ability of the brain to resist increases in MABP and CO and maintain normal CBF is explained by normal cerebral autoregulation. However, its vulnerability to modest decreases in blood volume, which cannot be attributed to variations in perfusion pressure, is unexplained but obviously has important therapeutic implications. This may be related to reduction in CO, changes in autonomic activity, or a decrease in the size of the perfused capillary bed.

Adrenergic alpha-Antagonists↗
PubMed1980

Transluminal angioplasty for basilar artery stenosis.

This report describes for the first time the successful use of transluminal balloon-catheter dilation (angioplasty) for high-grade basilar artery atherosclerotic stenotic lesions in two patients with frequent, severe, progressing symptoms that were unresponsive to anticoagulant therapy. Excellent angiographic and short-term clinical results have been obtained. These results and the relative frequency of these lesions justify further evaluation of this approach.

Arterial Occlusive Diseases↗
PubMed1979

Spontaneous internal carotid dissection, hemicrania, and Horner's syndrome.

We describe five patients with angiographic features of dissecting aneurysm of the cervical portion of the internal carotid artery who were seen initially with unilateral headaches and ipsilateral oculosympathetic paresis. This combination of symptoms is a rather common mode of manifestation of this entity.

Adult↗