Which operation for lumbosacral root compression?
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Humans↗
Biomedical subjects
B Weir
Publications and source records attributed to B Weir.
On the Gaseous Exchange of Ammonia between Leaves and the Environment: Determination of the Ammonia Compensation Point.
Whole shoots of Phaseolus vulgaris L. and other species were exposed to a range of partial pressures of gaseous ammonia in air and the resulting fluxes were measured. Net uptake is linear with partial pressure in the range 5 to 50 nanobars and is zero at a finite partial pressure, termed the ammonia compensation point. Below the compensation point, ammonia (or possibly other volatile amines) is evolved by the leaves. The compensation points in several species are near the low partial pressures found in unpolluted air and approximate to the K(m) of glutamine synthetase in vitro. In P. vulgaris L., the compensation point increases with temperature.
Journal Article↗
Experimental subarachnoid hemorrhage in the cynomolgus monkey: evaluation of treatment with hypertension, volume expansion, and ventilation.
We evaluated the treatment regime of dopamine-induced hypertension in association with volume expansion and ventilatory support in an experimental subarachnoid hemorrhage (SAH) model using the cynomolgus monkey. Regional cerebral blood flow, vessel caliber, intracranial pressure, and other pertinent physiological parameters were monitored throughout each study. We report the results for nine animals receiving treatment after an induced SAH and compare them with results obtained in a group of five animals not treated after SAH. Improvements in cerebral blood flow, vessel caliber, and morbidity and mortality rates were seen with this treatment. Seven of nine animals were alive at 20 hours after SAH in the treatment group, whereas all five animals in the untreated group died before this time. The mechanisms of action of this treatment are discussed. (Neurosurgery, 6: 57--62, 1980)
Animals↗
Responses to experimental subarachnoid hemorrhage in the spontaneously breathing primate.
The pathophysiological responses to experimental subarachnoid hemorrhage (SAH) were investigated in 20 spontaneously breathing cynomolgus monkeys. Four different volumes of fresh autogenous blood were used: 1.0, 1.33, 1.67, and 2.0 cc/kg. Five other animals had injection of 1.67 cc/kg of mock cerebrospinal fluid. Cerebral blood flow (CBF) was measured using the xenon-133 clearance technique. Respiratory rate and tidal volume were monitored by way of a Vertek pneumotach. The reduction of CBF after the SAH became more pronounced with increasing volumes of subarachnoid blood. The CBF remained reduced despite a return to normal of the cerebral perfusion pressure. Increasing SAH volumes were associated with greater abnormalities in the respiratory pattern, consisting of apnea and hyperventilation. These larger volumes were also associated with hypoxemia. Morbidity and mortality increased with increasing volumes of SAH, and are believed to be the result of a combination of decreased CBF, respiratory center disturbances, and pulmonary diffusion defects.
Animals↗
Oncotic pressure of subdural fluids.
The oncotic pressure of fluid from subdural hematomas and subdural hygromas was compared to that of simultaneously drawn venous blood in 20 patients. There was no significant difference in the oncotic pressure of fluid from subdural hematomas and venous blood; however, the oncotic pressure of fluid from subdural hygromas was significantly less than that of blood. This finding fails to support the Zollinger and Gross modification of Gardner's that chronic subdural hematomas grow and produce symptoms after a latent interval because they attract fluid from the blood via dural vessels.
Hematoma, Subdural↗
Evaluation of cerebral blood flow in arteriovenous malformations by the xenon 133 inhalation method.
Fifteen regional cerebral blood flow studies (rCBF) were conducted on 14 patients with arteriovenous malformations (AVM). Only one patient was studied at the time of a hemorrhage. None of the patients were operated upon. All patients had angiographically demonstrated lesions. All the CT scans performed demonstrated the lesions. rCBF was increased in the involved hemisphere compared to the non-involved hemisphere and the difference was greater when the malformations were superficial. There was a higher incidence of high flow regions in the involved hemisphere of patients with AVMs compared to our normal control group and patients with subarachnoid hemorrhage (SAH) from aneurysms. Flow rates within the involved hemisphere demonstrated abnormal distributions and greater variability than normals. Some peaks previously demonstrated in the intra-arterial flow studies are not apparent using the inhalation method. This non-invasive technique has a potential to provide additional useful information on the natural history of this disorder.
Adult↗
Medical aspects of the preoperative management of aneurysms: a review.
The aim of medical management of a patient with a recently ruptured intracranial aneurysm is to preserve residual brain function and prevent systemic complications. Surgery should be performed as soon as the patient is in good neurological condition. Most fatalities result from the destructive effects of the initial hemorrhage, but delayed ischemic neurologic deficit can result from vasospasm and rebleeding. Systemic complications of the brain damaged state result in a smaller proportion of deaths. Common medical problems are reviewed as well as their medical management. In particular, some special problems related to subarachnoid hemorrhage such as cerebral edema and herniations, rebleeding, and vasospasm are also considered. Major recent advances have been the introduction of antifibrinolytic therapy, the realization of the importance of maintaining blood volume and pressure, as well as general advances in respiratory care.
Bacterial Infections↗
Treatment of subarachnoid hemorrhage with sodium nitroprusside and phenylephrine: an experimental study.
The effectiveness of simultaneous intravenous sodium nitroprusside and phenylephrine in improving the cerebrovascular disturbances and survival rate after induced subarachnoid hemorrhage (SAH) was studied in the cynomolgus monkey. We measured regional cerebral blood flow (rCBF) using the intra-arterial xenon-133 clearance technique. In our experimental animal model, SAH was associated with a persistent reduction in rCBF, elevation of cerebrovascular resistance (CVR), cerebral vasospasm for the duration of the study (150 minutes), and poor survival. For animals receiving the treatment regime (administered approximately 25 minutes after the induced SAH), rCBF remained low, CVR was high, and cerebral vasospasm was persistent. Survival in this group was the same as that observed for the untreated animals. Simultaneous administration of sodium nitroprusside and phenylephrine was ineffective in improving rCBF, CVR, cerebral vasospasm, or survival after SAH. In the control group (receiving only the treatment and not an intracranial insult), rCBF was below resting levels both during and after therapy, indicating impaired cerebral autoregulation. (Neurosurgery, 5: 688--595, 1979).
Animals↗
Regional cerebral blood flow in patients with aneurysms: estimation by Xenon 133 inhalation.
Seventy six regional cerebral blood flow (rCBF) studies were conducted on 32 patients who had a total of 39 aneurysms. Twenty three of these patients were studied pre- and post-operatively. Normal values were obtained from a control group of 33 subjects, each of whom underwent one rCBF study. Flow was reduced following subarachnoid hemorrhage (SAH); it increased significantly post-operatively. Lower flows were associated with poorer clinical grades. There was a greater variation in regional distribution of flow immediately following SAH than in normals or in patients who had recovered from the acute phase. rCBF studies correlated with CT scans demonstrated that a progressive increase in ventricular size was accompanied by a progressive reduction in flow. In addition, intraventricular hemorrhage (IVH) was associated with a significant reduction in cerebral blood flow (CBF). No significant correlation between CBF and spasm was demonstrable.
Adult↗
Time course of vasospasm in man.
Measurements were made at eight predetermined positions on 627 sets of angiograms from 293 patients with aneurysms. A ratio between the sum of the vessel diameters in the subarachnoid space to the sum in the base of skull and neck was calculated and plotted against time. Vasospasm has its onset in man about Day 3 after subarachnoid hemorrhage, is maximal at Days 6 to 8, and is gone by Day 12. There is a tendency for patients in poor clinical grades to have more vasospasm. The patients with most vasospasm have a significantly higher mortality than those with the least.
Carotid Artery, Internal↗
Cerebral arterial responses to induced hypertension following subarachnoid hemorrhage in the monkey.
Regional cerebral blood flow (rCBF), angiographic cerebral arterial caliber, and cerebrospinal fluid (CSF) pressure were measured in rhesus monkeys to determine the effect of experimentally induced subarachnoid hemorrhage (SAH) on cerebral arterial responses to graded increases in blood pressure. These measurements were also performed in a control group of monkeys subjected to a mock SAH by injection of artificial CSF into the cerebral space. Before subarachnoid injection of blood or artificial CSF, graded increases in mean arterial blood pressure (MABP) to a level 40% to 50% above baseline values had no effect on rCBF. The major cerebral arteries constricted and CSF pressure remained unchanged. Similar responses were observed after injections of artificial CSF. When MABP was increased in animals that had been subjected to subarachnoid injection of blood, rCBF increased and was associated with dilatation of the major cerebral arteries and moderate increases in CSF pressure. These results demonstrate that cerebral arterial responses to increases in blood pressure may be abnormal in the presence of subarachnoid blood. The manner in which abnormal cerebral arterial reactivity, changes in blood pressure, and vasospasm combine to determine the level of cerebral perfusion following SAH is postulated.
Animals↗
Intracranial aneurysms: a clinical, angiographic and computerized tomographic study.
Fifty-six patients with 63 aneurysms were selected from a larger group of patients because they had at least one angiographic and one CT scan study. A total of 102 CT scans and 136 angiograms were analyzed. In five patients the aneurysm was visualized on the CT scan. There was a tendency for the location of the subarachnoid hemorrhage and intracerebral hematomas visualized on the CT scans to correlate with the site of the aneurysm as seen on the angiogram. The CT scan was useful in demonstrating the evolution of hydrocephalus and in differentiating hematoma from edema. The patients with normal CT scans were more likely to have good neurological grades. No single angiographic or CT scan feature correlated significantly with survival at lower than the 5 percent level.
Angiography↗
Safety and efficacy of combining obstetric and noninfectious gynecologic hospital patients.
Unoccupied obstetric beds and unused delivery rooms represent inefficient use of hospital facilities and loss of revenue, both of which adversely affect the quality of care rendered patients. Hartford Hospital has permitted the admission of obstetric and noninfectious gynecologic patients to the same patient care areas of the hospital as well as use of delivery rooms by both groups of patients. Elaborate surveillance of these patients by the epidemiology section for a 1-year period (July 1974-July 1975) demonstrated no increase in the incidence of hospital-acquired infections associated with this combined approach as compared with the more traditional separation system of maternity and nonmaternity patients.
Connecticut↗
Clinical, epidemiologic and bacteriologic observations of an outbreak of methicillin-resistant Staphylococcus aureus at a large community hospital.
Over a 12 month period, 61 isolates of methicillin-resistant Staphylococcus aureus (MR-SA) were obtained in 23 hospitalized patients. Eight-six per cent of the patients were over 50 years of age, and 91 per cent were in the postoperative period. In 10 patients (42 per cent), MR-SA was the major pathogen, producing either pneumonia, empyema, osteomyelitis, lung abscess, enterocolitis, wound infection or bacteremia with sepsis. Three patients in this group died despite therapy with antibiotics with in vitro activity against these organisms. All the patients probably acquired their MR-SA in the hospital, and five carriers of the organism were identified among hospital personnel. This outbreak demonstrates the ability of MR-SA not only to colonize many patients in a relatively brief period of time, but also to produce serious disease.
Adult↗
The relative significance of factors affecting postoperative survival in astrocytomas, grades one and two.
The records of 107 patients with supratentorial astrocytomas, Grades 1 and 2 treated surgically between 1960 and 1970 were analyzed. Abstracted clinical data was retrospectively analyzed with respect to the relative significance of different factors affecting survival. Twenty-eight patients were alive at the time of follow-up in 1974. Age, clinical grade at surgery and radiation therapy were the most important determinants of prolonged postoperative survival. The more malignant astrocytomas occurring in the Province of Alberta had previously been reviewed. The present study was carried out to demonstrate the relative influence of histologic grade of astrocytomas and to analyze the factors affecting postoperative survival in the low grade, supratentorial astrocytomas.
Age Factors↗
Radiotherapy and CCNU in the treatment of high-grade supratentorial astrocytomas.
Forty-one consecutive patients with supratentorial primary brain tumors (38 Grade III and IV astrocytomas, one giant-cell astrocytoma, and two cases with insufficient tissue for diagnosis) were randomly allocated within 2 weeks of surgery to one of three therapeutic groups. Group 1 (15 patients) received radiation therapy totaling 4000 to 4500 rads in 4 to 5 weeks. Group 2 (13 patients) received 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea CCNU) 130 mg/sq m orally every 6 weeks. Group 3 (13 patients) received radiation therapy plus CCNU as for Groups 1 and 2. When the disease progressed, patients in Groups 1 and 2 were crossed over to receive CCNU and irradiation respectively. The median survival time in these groups was 188, 259, and 252 days, and the mean survival 263, 262, and 329 days. The median time from diagnosis to crossover (Groups 1 and 2) or to progression (Group 3) was 163, 99, and 220 days, and the mean time was 172, 108, and 231 days. There was no statistically significant difference between the means or medians in any of these situations.
Astrocytoma↗
Relative prognostic significance of vasospasm following subarachnoid hemorrhage.
A retrospective analysis of 274 patients with intracranial aneurysms, diagnosed either angiographically or at autopsy between 1968 and 1973 at the University of Alberta, was carried out. One hundred and forty-six patients had intracranial clipping of the aneurysm. Clinical and radiologic data were abstracted from the chart and the angiographic studies. Probability of survival curves were constructed. Associations between various clinical factors and survival at two months were demonstrated. The most important prognostic factors were the clinical grade at angiography or surgery, followed by the presence of preoperative spasm, hematoma or focal edema, elevated blood pressure on admission, time of interval from hemorrhage to surgery and age. The data lends some support to the policy of operating on patients in good neurological condition, even if their pre-operative angiogram shows spasm.
Age Factors↗
The relative significance of factors affecting postoperative survival in astrocytomas, grades 3 and 4.
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Astrocytoma↗