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Biomedical subjects

R M Crowell

Publications and source records attributed to R M Crowell.

100 records · Page 6Linked to original sources
PubMedDate not supplied

Intravenous nitroglycerin in experimental cerebral vasospasm. A preliminary report.

Cerebral arteriospasm is a common complication of subarachnoid hemorrhage and is responsible for much of the brain damage which accompanies it. No pharmacologic agent has been found which regularly alleviates arteriospasm. We have evaluated the effect of continuous intravenous nitroglycerin infusion on the diameter of the basilar artery in dogs with cerebral vasospasm experimentally induced by subarachnoid blood injection. In 6 consecutive dogs, 10 minutes after beginning intravenous nitroglycerin at 100 microgram/min and at other times during 120 minutes of infusion, the diameter of the basilar artery had increased from 75 +/- 2% of control value to 114 +/- 2% of control value (p less than 0.001). In all 6 dogs, the basilar artery diameter during infusion was greater than the control value prior to creating subarachnoid hemorrhage. Intravenous nitroglycerin caused only a moderate (8%) decrease in blood pressure. Further investigation of the effects of nitroglycerin on cerebral vasospasm is warranted.

Animals↗
PubMedDate not supplied

EEG monitoring for induced hypotension for surgery of intracranial aneurysms.

EEG was monitored at bilateral scalp sites outside the operative field during hypotensive aneurysm surgery in 21 patients. Mean arterial blood pressure at axillary level was 50-60 mm Hg (average 55 mm) for 1.9-5.3 hours (average 3.6). Four new deficits were noted immediately post-operatively, all related to the operated site: these were attributable to intra-operative rupture with forced vascular clipping, vasospasm, or edema. In no instance was hypotension solely responsible for a new deficit. EEG showed persistent slowing in relation to surgery in only 1 patient, where aneurysmal rupture led to severe hypotension, forced clipping of 1 posterior cerebral artery, and subsequent brain stem infarction. In the 3 other patients with fresh focal postoperative deficits, no persistent intraoperative EEG changes were observed. EEG monitoring did not detect ischemia in these 3 patients because 1) hypotension was moderate and did not per se cause new deficit, and 2) EEG electrodes did not survey the area at maximal risk, namely the operative field. EEG scalp electrodes near but outside the operative site do not seem useful for monitoring cerebral function in the region of aneurysm surgery. Epidural or cortical electrodes in the operative field may prove to be more useful.

Adult↗
PubMedDate not supplied

Comparison of local cerebral blood flow determined by thermal and hydrogen clearance.

Local cerebral blood flow (1CBF) was measured simultaneously in ten cats with (1) a large surface thermal diffusion probe resting on the cortex and (2) hydrogen clearance curves from implanted electrodes surrounding the thermal probe. A close correlation was found between 1CBF values obtained by the two methods. Since hydrogen clearance is accepted as quantitative, the data suggest that the thermal diffusion technique is a reliably quantitative means of measuring local cerebral blood flow.

Animals↗
PubMedDate not supplied

Cortical blood flow during extracranial-intracranial bypass surgery.

Cortical blood flow was evaluated at the time of surgery with a thermal diffusion flow probe in 25 extracranial-intracranial bypass operations. The procedures were performed 14 times for carotid occlusion, 6 times for inaccessible carotid stenosis, on 3 occasions for middle cerebral occlusion, once for basilar occlusion and once for middle cerebral stenosis. Fifty-seven different cortical regions were evaluated before and after completion of the anastomosis. During temporary occlusion of the cortical vessel, no significant changes in cortical blood flow were identified. The mean flow pre-bypass was 58 ml/100 g/min and postbypass was 66. This was a significant difference. When initial ischemic areas were evaluated, flows increased from 36 ml/100 g/min to 52 ml/100 g/min. These postbypass flows were statistically different than the flow values in the nonischemic areas of 75 ml/100 g/min. Blood pressure and arterial carbon dioxide tension did not vary significantly. Extracranial-intracranial bypass increases cortical flow in ischemic areas although this does not bring the flow into the normal range.

Cerebral Revascularization↗
PubMedDate not supplied

The anterior communicating artery has significant branches.

The anterior communicating artery was studied with the operating microscope in 10 autopsy cases. This vessel was present in all cases with reduplication in three. Arterial diameter ranged from 0.8 to 2.3 mm, with lengths of 5 to 10 mm. Branches of the anterior communicating artery were found in every case (range 3-13, average 5.4). Most branches were small (50-250 mu), but at least one large branch (250-1000 mu) was invariably present. Small ventral branches ramified on the optic chiasm. Small and large dorsal branches distributed themselves to lamina terminalis, hypothalamus, parolfactory areas, columns of fornix, and corpus callosum. Injury to these vessels caused by aneurysmal rupture or surgical manipulation may lead to serious clinical deficits.

Cerebral Arteries↗
PubMedDate not supplied

Giant intracranial aneurysms of the anterior circulation: clinical characteristics and diagnosis by computed tomography.

The computed tomography (CT) characteristics and clinical features of giant (globoid) aneurysms of the anterior circulation are reviewed. These lesions appear on the CT scan as smoothly encapsulated ovoid masses, within which a partially patent lumen is seen after the infusion of iodinated contrast material. With careful analysis of the CT scan it may be possible to differentiate giant internal carotid artery, anterior cerebral artery, and middle cerebral artery aneurysms from other parasellar and hemispheric lesions.

Adult↗
PubMedDate not supplied

Cavernous hemangioma of the retina. Genetic and central nervous system involvement.

A 1967 report described retinal "telangiectasia" in a brother and sister. The brother also had concurrent immune deficiency with hypogammaglobulinemia. Several reports have since been published on similar retinal vascular lesions, which have been termed "cavernous hemangioma of the retina." In retrospect, it is likely that this sibling pair also had cavernous hemangioma of the retina and brain, and that the hypogammaglobulinemia was an independent problem. Our report provides a 19-year follow-up on three generations of this family. The affected generations support the diagnosis of a phakomatosis having autosomal dominant inheritance. Cavernous hemangioma of the retina is usually a stable disease, but there is a potential risk of intracranial hemorrhage from cavernous hemangioma of the brain. Family members, with and without fundus findings, should therefore undergo computed tomography or magnetic resonance imaging of the brain, because neurosurgical prophylaxis or treatment may be indicated.

Adolescent↗