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Biomedical subjects

T M Sundt

Publications and source records attributed to T M Sundt.

At least 217 records · Page 12Linked to original sources
PubMed1977

Idiopathic regressing arteriopathy.

Three patients had nonatheromatous occlusive cervicocephalic arterial disease which on follow-up showed resolution of the occlusive or stenosing abnormalities. The patients' relatively young age (middle thirties to middle forties) and severe unilateral headache or focal head, neck, or mastoid pain were prominent common clinical features. The dominant arteriographic features were intimal irregularities, multiple vessel involvement, tendency to arterial dissection and aneurysm formation, sparing of intracranial arteries, and tendency to partial or complete resolution of the abnormalities and regression toward normal. We have called this presumed entity "idiopathic regressing arteriopathy" pending appropriate histopathological studies.

Adult↗
PubMed1977

Thrombus formation and endothelial alterations in microarterial anastomoses.

The sequential hematological and endothelial responses in the postoperative period after end-to-side arterial anastomosis in 1- to 1.3-mm vessels were assessed by scanning electron microscopy. Two minutes after restoration of flow, an amorphous coating covered the vessel lumen around the suture line, and oozing of blood from the suture line ceased. Within 15 minutes, a partially occluding thrombus was present, which was maximal at the anastomotic bifurcation point. The thrombus underwent partial lysis or embolization within 30 minutes, and gross intraluminal thrombi did not recur. The initial thrombi that formed within 2 minutes were composed of platelets and erythrocytes in a loose reticular fibrin network, but the intraluminal thrombi present at the branch point 15 minutes after flow restoration appeared to be composed solely of platelets. Thrombi that did not undergo complete dissolution had a loss of distinct cellular elements at later time intervals. The fibrin-platelet matrix coating the lumen remained unchanged during the initial 24 hours. When examined at 9 days, normal endothelium was present throughout the vessel with the exception of the suture line, which remained covered by a smooth coagulum. This sequence of events suggest that if surgical manipulation is to result in complete occlusion of the anastomosis, it will likely occur in the initial 30 minutes after resumption of blood flow. Anticoagulant regimens were evaluated. Pretreatment with aspirin and intraoperative heparin irrigation of the vessel lumen were not beneficial in altering the quantity of thrombus. All systemic heparin regimes tested resulted in a quantitative decrease of thrombotic material. Five minutes of intravenous heparin therapy after resumption of blood flow was as effective as long-term heparin in decreasing the transient intraluminal thrombotic response.

Animals↗
PubMed1977

An automated cerebral blood flow analyzer: concise communication.

We present an automated cerebral blood-flow (CBF) analyzer can be used as an intermittent CBF monitor during carotid endarterectomies. Given a 1-min sample of an intracarotid injection of xenon-133, this device will display a CBF value with a range from zero to 200 ml/100 g per min. Results from this CBF analyzer were compared with those from manual computations in 181 separate determinations during 51 surgical procedures. The analyzer is effective, accurate, and reliable.

Carotid Arteries↗
PubMed1977

Physiological considerations important for the management of vasospasm.

The physiological mechanisms of known importance in the control of cerebral blood flow (CBF) and smooth muscle contraction and relaxation are reviewed. The pathophysiology of vasospasm following subarachnoid hemorrhage (SAH) is correlated with an alteration of these mechanisms. It is emphasized that smooth muscle relaxation is an energy-dependent process and that vasodilators require a functional smooth muscle membrane that may be severely impaired in ischemia or subarachnoid hemorrhage. The temporal profile of ischemia from spasm is correlated with the pathophysiology of altered metabolism of smooth muscle. The relevance of this complication to the timing of aneurysm surgery in 337 cases operated by one surgeon is considered along with various drug regimens suggested for its management.

Albuterol↗
PubMed1977

Carotid endarterectomy: results, complications, and monitoring techniques.

A system of grouping patients according to preoperative evaluation of risk of carotid endaterectomy is presented. The primary complications of this surgical procedure were myocardial infarction and residual mild to severe neurologic deficit. Neurologically stable patients without medical or angiographically determined risk factors (group 1) have a risk of 1%. Neurologically stable patients without medical risk but with angiographically determined risks (group 2) have a risk of 2%. Neurologically stable patients with significant medical illness and with or without angiographically determined risks (group 3) have a risk of 7%, primarily related to cardiac disease. Neurologically unstable patients (group 4) have a 6% risk for a neurologic deficit. Current monitoring techniques using continuous electroencephalograms, cerebral blood flow measurements, and arterial stump pressure are considered. The prevention and management of complications are presented in some detail.

Adenosine Triphosphate↗
PubMed1976

Cerebral protection by barbiturate anesthesia. Use after middle cerebral artery occlusion in Java monkeys.

Regional cerebral ischemia was produced in 18 Java monkeys by permanent middle cerebral artery (MCA) occlusion. All monkeys were thereafter paralyzed (pancuronium bromide, 0.05 mg/kg/hr) and sedated (diazepam, 0.1 mg/kg/hr) for a 48-hour period. Thirty minutes after MCA occlusion, pentobarbital sodium anesthesia was induced in nine of the monkeys (14 mg/kg) and maintained for 48 hours (7 mg/kg every two hours), with continuous supportive care. After 48 hours, all drugs were discontinued; the monkeys were observed for five days, and then killed. Seven of the control monkeys developed a cerebral infarction, three did not survive past the 48 hours of intensive care, and the other four had a notable neurologic deficit. All pentobarbital monkeys survived the seven days, but four had a cerebral infarction and two of these had a notable neurologic deficit. These differences were statistically significant.

Anesthesia, Inhalation↗
PubMed1976

Rapid resolution of venous stasis retinopathy after carotid endarterectomy.

A 60-year-old woman with ocular hypertension developed unilateral venous stasis retinopathy and neovascularization of the optic disk as the first signs of carotid occlusive disease. The retinopathy and the neovascularization disappeared rapidly and dramatically after carotid endarterectomy. Neovascularization in venous stasis retinopathy must be maintained by hypoxia or hypoperfusion, possibly through some intermediate substance such as a vasoproliferative factor.

Carotid Artery Thrombosis↗
PubMed1976

Internal carotid artery stump pressure and cerebral blood flow during carotid endarterectomy: modification by halothane, enflurane, and innovar.

Carotid endarterectomy requires temporary surgical occlusion of the involved carotid artery. During occlusion, the minimally acceptable (critical) internal carotid artery stump pressure is reported to be 50 torr, whereas for regional cerebral blood flow (rCBF), a critical range is reported to be 18-24 ml/100 g/min. During 90 carotid endarterectomies, rCBF and stump pressure were measured and the EEG continuously monitored. A positive correlation between rCBF and stump pressure (i.e., when both were either above or below their respective critical values) was observed in only 58 per cent of the cases. In 28 per cent stump pressures of less than 50 torr were observed despite rCBF's above 24 ml/100 g/min and normal EEG's. In 8 per cent stump pressures were more than 50 torr but rCBF's were less than 18 ml/100 g/min and EEG changes of ischemia were commonly observed. In the remaining 6 per cent rCBF's were marginal (18-24 ml/100 g/min) while stump pressures were more than 50 torr and EEG changes were not observed. The relationship between stump pressure and rCBF was influenced by the anesthetic. In the absence of transient ischemia during occlusion (that is, rCBF greater than 18 ml/100 g/min), halothane and enflurane anesthesia were associated with significantly higher rCBF's and lower stump pressures than was neuroleptanesthesia. Pre-occlusion and post-occlusion rCBF measurements also demonstrated cerebral vasodilation by halothane and enflurane (halothane greater than enflurane) and vasoconstriction by neuroleptanesthesia. It is concluded that stump pressure is an unreliable index of CBF during carotid occlusion and that its relationship to CBF is considerably influenced by the anesthetic.

Blood Flow Velocity↗
PubMed1976

Clinical and laboratory experience with heparin-impregnated silicone shunts for carotid endarterectomy.

Our experience with use of a Silastic shunt for carotid endarterectomy is reviewed briefly, and the complication of shunt thrombosis despite intraoperative administration of heparin is noted. Of obvious importance are the reduction of blood flow and the possibility of embolization caused by accumulating thrombus. Shunt thrombosis has been abolished by the use of heparin-impregnated Silastic shunts. In experiments in dogs, such heparin-treated shunts showed greater thromboresistance than did untreated shunts.

Aged↗
PubMed1976

Effect of hypocapnia, hypercapnia, and blood pressure on NADH fluorescence, electrical activity, and blood flow in normal and partially ischemic monkey cortex.

Nicotinamide adenine dinucleotide fluorescence, cortical reflectance, cortical blood flow, and electroencephalograms were recorded from squirrel monkey brains before, during, and after focal transient cerebral ischemia produced by the temporary clipping of the middle cerebral artery. After release of the occluding clip, the monkeys were followed through an N2-breathing cycle and then to death from anoxia. The effects of controlled variations in arterial carbon dioxide tensions (PaCO2) and mean arterial blood pressures (MABP) were investigated in normal and in ischemic brain. In normal brain, with preserved autoregulation, NADH fluorescence was constant through a wide range in Paco2, MABP, and cortical blood flow. In ischemic brain, NADH levels increased, correlated closely with decreased cortical blood flow and EEG abnormalities, and became dependent on MABP. Artifacts in fluorescent measurements 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.

Animals↗
PubMed1976

The relevance of peripheral baroreceptors and chemoreceptors to regulation of cerebral blood flow in the cat.

The contribution of neural vasomotor reflexes to the control of cerebral blood flow (CBF) was investigated in 30 cats lightly anesthetized with pentobarbital. CBF was measured both by kinetic analysis and by the intial slope technique of the washout curve of a bolus of 133Xe. Autoregulation (10 cats) and responsiveness to alteration in arterial PCO2 (PaCO2) (10 cats) and arterial PO2 (Pao2) (five cats) were assessed both before and after bilateral intracranial division of the 9th and 10th nerves. In an additional group (five cats), related changes in CBF to alteration of PaCO2 were recorded before and after unilateral section of the 7th and 8th nerves. Autoregulation was preserve after division of the 9th and 10th nerves and there was no significant change in the PaCO2 response curves. Section of the 7th and 8th cranial nerves did not produce conclusive results in the small number of cats studied. A conclusion that the facial nerves are not dominant in responses to hypercapnia seems justified, but a modulating role for these nerves is possible. These studies do not exclude a physiological role for these nerves in the autoregulation of CBF, but do indicate that the cerebral vascular bed apparently is capable of functioning normally after their division.

Animals↗
PubMed1976

Neurovascular microsurgery: a model for laboratory investigation and the development of technical skills.

An inexpensive and reproducible model to help in developing the technical skills for, and to investigate experimentally, a microvascular anastomosis resembling the superficial temporal-middle cerebral artery bypass is described. The model is used to illustrate the important principles of microvascular surgery. Using a standardized operative technique, we evaluated 50 successive preparations by perfusion; the patency rate was 100%.

Anesthesia, General↗
PubMed1976

Progressing stroke. Angiographic aspects.

Progressing strokes were noted in 17 of 256 patients who underwent surgery for atheromatous disease involving the internal carotid artery. This disorder was characterized by an active increase in the neurologic deficit during an 18- to 24-hour period. Although angiographic findings were neither specific for this type of cerebrovascular disease nor uniformly present, the angiography did indicate that not only embolization of the cerebral leptomeningeal conducting vessels but also collaterization through them was a pertinent mechanism.

Aged↗
PubMed1976

Bypass surgery for vascular disease of the carotid system.

A series of 58 operations on 56 patients, in whom a branch of the superficial temporal artery was anastomosed to a branch of the middle cerebral artery (STA-MCA bypass or Yasargil procedure), is reviewed. These operations were performed chiefly for occlussions or for inaccessible stenotic lesions of the internal carotid or middle cerebral arteries. Patency in eight patients operated on from April 1971 through November 1973 was low (25%). Patency in patients operated on since July 1974 has been high (95%). There have been no deaths and no major ischemic strokes attributable to the surgery. The rationale for this procedure is considered in relationship to the anatomy and physiology of the cerebral circulation and the pathogenesis of syndromes of cerebral ischemia. The operation appears to have a low morbidity in good-risk patients. The role of this operation in managing common manifestations of cerebral vascular disease such as focal transient cerebral ischemic attacks (TIAs) and amaurosis fugax, although not fully established, appears encouraging. The procedure seems useful for orthostatic cerebral ischemia caused by multiple occlusions of major extracranial (and intracranial) vessels and, occasionally, for progressing strokes related to internal carotid artery occlusion, both of which are relatively uncommon manifestations of cerebral vascular occlusive disease. It may have application in the rare "slow stroke." The procedure is probably of limited value, if any, in the management of large completed infarcts but may be indicated in selected patients with small infarctions who have preserved most of their cerebral function and who have had evidence of subsequent focal ischemic events. The procedure is useful for bypassing giant aneurysms or basofrontal tumors invading major vessels. It may have a role in the management of fibromuscular disease of the internal carotid artery.

Adult↗