Biomedical subjects
Publications and source records attributed to F A Simeone.
A patient with a meningioma of the medial sphenoid wing underwent inadvertent intraoperative occlusion of the middle cerebral artery. Neurological deficit and infarction were presumably prevented by immediate administration of pentobarbital followed by extracranial-intracranial bypass.
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Under the auspices of the Belgian Surgical Society, a small group of American and European surgeons discussed in detail the place of lumbar sympathectomy in present day surgical practice. A consensus was reached concerning the physiologic effect, anatomical variations and indications for the operation. Conclusions included the questionable value of lumbar sympathectomy for treating intermittent claudication due to aortoiliac disease alone, its possible effectiveness when obliterative arterial disease is limited to the femoral popliteal segment, and its occasional beneficial effect when performed in conjunction with some reconstructive arterial operations.
Upper cervical spine injuries can be complicated by occlusion of the vertebral and carotid arteries. Injury to the former is more common. The arteries may be kinked or temporarily occluded, in which case the symptoms are transient. With more forceful trauma, damage to the intima and subsequent thrombosis or prolonged spasm may ensue. Early recognition of ischemic symptoms hastens the diagnosis. In most instances it is not possible to alter advanced neurologic deficits once they are established.
During the four year period from 1972 to 1975, eleven patients, eight with recurrent and three with first attacks of ventricular fibrillation, underwent aortocoronary bypass graft and/or resection of ventricular aneurysm. All patients had old myocardial infarction from seven weeks to six years. Left ventricular angiography demonstrated discrete aneurysm of the anterior wall of the left ventricle in nine of the patients and akinesis or hypokinesis of the anterior and posterior wall of the left ventricle in the remaining two. Coronary angiography was carried out in ten patients and revealed significant disease of the left anterior descending and right coronary arteries in ten and nine patients, respectively. There was no operative mortality, and there were two late deaths. Eight patients have improved significantly and have had no further sign of ventricular irritability. The present study indicates that aortocoronary bypass graft and/or resection of ventricular aneurysm is an effective method of therapy for patients with repeacted ventricular fibrillation who have ventricular aneurysm and ischemic heart disease.
The ganglionated lumbar sympathetic chains lie on the lateral aspects of the bodies of the lumbar vertebrae and not more laterally as in the thorax where the chain lies in relation to the heads and necks of the ribs. Lumbar ganglia vary in number. They are best numbered according to the spinal nerve to which the particular ganglion sends its postganglionic fibers, but, at operation, the surgeon is unable to obtain this kind of information. It is customary to mark the extent of resection by the application of a dura clip to the proximal and distal ends of the trunk. Roentgenographic visualization later can approximate the level of resection in relation to the vertebrae. Anomalies can lead to unsuccessful denervation of the lower extremities. These include extraganglionic connecting sympathetic nerve trunks, intermediate ganglia, and cross-over fibers connecting the right and left lumbar sympathetic trunks usually at the level of the fourth and fifth lumbar segments, but anatomically sometimes as high as the third and second. Specific complications of lumbar sympathectomy include failure of adequate denervation, brief paralytic ileus, hyperidrosis in parts of the body which remain normally innervated, sexual dysfunction, and post-sympathectomy neuralgia.
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The authors report and analyze the in vitro contractions of fresh bovine cerebral artery on exposure to blood. The vessel does not contract significantly until blood clots on its surfaces; the contraction begins at the moment of clotting and is maintained as long as extracellular calcium is available. Comparative studies with vasoconstrictor amines suggest that serotonin, liberated from platelets by the clotting process, is responsible for this contraction and that the adherent clot itself concentrates the serotonin of the surface of the vessel. This contraction persists throughout the"viability" of the in vitro preparation, approximately 10 hours. Serotonin is capable of producing this sustained contraction by increasing smooth muscle cell membrane permeability to extracellular calcium, which in turn activates native actinomycin.
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The effect of pentobarbital and hypothermia on the development of ischemic brain edema was studied in 23 rhesus monkeys undergoing transorbital middle cerebral artery occlusion. Fifteen additional animals served as unclipped controls. Regional cortical cerebral blood flow (rCBF), arteriovenous oxygen content difference (AVDO2), and regional cortical metabolic rate of O2 (rCMRO2) were measured hourly until sacrifie 11 hours postocclusion, at which time ischemic cerebral edema was measured. In 8 animals no treatment followed the occlusion, and these developed edema. In 7 animals pentobarbial 14 mg/kg was administered intravenously 30 min after occlusion and 7 mg/kg every 2 hours thereafter. In this group ischemic brain edema was negligible. In 8 animals, hypothermia to 25.9 +/- 0.5 degrees C was started 30 min after occlusion and maintained until sacrifice; ischemic brain edema was not significantly altered from untreated-clipped animals. On the basis that both pentobarbital and hypothermia produced similar changes in rCBF, AVDO2, and rCMRO2, but only pentobarbital prevented edema, it is postulated that the mode of action of barbiturates in preventing ischemic brain edema is not entirely related to their known effect on blood flow and metabolism.
Cerebral arteries have an abundant supply of adrenergic nerve fibers which are believed to release vasoactive substances responsible for the induction of cerebral vasospasm. To assess the importance of adrenergic nerves in this phenomenon, high doses (600 microgram/ml) of 6-hydroxydopamine (6-OHDA) were used to produce in vitro chemical sympathectomy in bovine middle cerebral artery. 6-OHDA reduced catecholamine fluorescence to undectable limits. H3-norepinephrine re-uptake was reduced to 1.5% of intact controls. Arterial norepinephrine content was reduced by 92%. Contractile responses to norepinephrine, serotonin, and fresh human whole blood were modestly reduced after denervation. This reduction was probably due to alpha receptor inactivation by 6-OHDA, because after protection of the alpha receptors with phentolamine the vessel response was the same as in untreated controls. Contractions in response to aged human whole blood were not affected by denervation. The results suggest that the endogenous release of catecholamines does not play a major role in the initiation or spread of blood-induced vasospasm in large cerebral arteries.