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Biomedical subjects

R D Brown

Publications and source records attributed to R D Brown.

At least 73 records · Page 4Linked to original sources
PubMed1999

Surgical patent foramen ovale closure for prevention of paradoxical embolism-related cerebrovascular ischemic events.

BACKGROUND: The role of surgical closure of patent foramen ovale (PFO) for cerebral infarction (CI) or transient ischemic attack (TIA) resulting from paradoxical embolism is unclear, and its effect on recurrence is unknown. Our objective was to determine the outcome of surgical closure of PFO in patients with a prior ischemic neurological event, define the rate of CI or TIA recurrence after PFO closure, and identify risk factors for these recurrences. METHODS AND RESULTS: We retrospectively analyzed 91 patients (58 men, 33 women) with >/=1 previous cerebrovascular ischemic events who underwent surgical PFO closure between April 1982 and March 1998. The presence of a PFO with a right-to-left shunt was confirmed with transesophageal echocardiography. Mean age was 44.2+/-12.2 years. The index event was a CI in 59 and a TIA in 32; a Valsalva-like episode preceded the event in 15 patients. Deep venous thrombosis was documented in 9 patients, and a hypercoagulable state was identified in 10. Surgical closure was performed with extracorporeal circulation by either direct suture (n=82) or patch closure (n=9). Limited incisions were used in 18.7% of patients. There was no operative mortality. Morbidity included transient atrial fibrillation (n=11), pericardial drainage for effusion (n=4), exploration for bleeding (n=3), and superficial wound infection (n=1). Follow-up totaled 176.3 patient-years, and mean follow-up was 2.0 years. No one had a CI, and 8 had a TIA during follow-up, with 1 caused by temporal arteritis. Transesophageal echocardiography demonstrated all closures to be intact in these patients. The overall freedom from TIA recurrence during follow-up was 92.5+/-3.2% at 1 year and 83.4+/-6.0% at 4 years. Having multiple neurological events before PFO closure was the only significant risk factor for TIA or CI recurrence after closure by univariate analysis (P=0.05); the small number of post-PFO closure cerebral ischemic events precluded multivariate analysis. CONCLUSIONS: Surgical closure of PFO can be performed with minimal morbidity and mortality. PFO closure may decrease the risk of recurrent stroke or TIA and may avoid lifelong anticoagulation in the young adult if there is no other indication. Recurrent cerebrovascular ischemic events after surgery should prompt further evaluation to identify causes other than paradoxical embolism.

Adult↗
PubMed1999

Comparison of population-based models of risk factors for TIA and ischemic stroke.

OBJECTIVE: To determine whether there is a difference in the risk factors for ischemic stroke and for TIA. BACKGROUND: TIA is associated with a high risk for ischemic stroke, but some have considered TIA as mild ischemic stroke. Prevention of disabling stroke is sufficient reason to label TIA as a precursor for stroke, but some risk factors may be more or less associated with TIA than with ischemic stroke, suggesting differences in mechanism. METHODS: The medical records linkage system for the Rochester Epidemiology Project provided the means of identifying first episodes of TIA in the Rochester, MN population among those who had not had ischemic stroke. Control subjects were selected from an enumeration of the population through the medical records. The exposure to various risk factors was ascertained. The conditional likelihood approach to estimate the parameters of a multiple logistic model permitted estimation of the OR for TIA for each risk factor while adjusting for confounding variables. RESULTS: The multivariable logistic regression model for TIA shows that the estimates of the ORs for ischemic heart disease, hypertension, persistent atrial fibrillation, diabetes mellitus, and cigarette smoking are similar to the ORs for those variables in the ischemic stroke model. However, the OR for mitral valve disease in the TIA model is 0.4, suggesting that mitral valve disease is unlikely to be associated with cerebral ischemic episodes that are brief enough to be called TIA.

Brain Ischemia↗
PubMed1999

Frequency of major complications of aspirin, warfarin, and intravenous heparin for secondary stroke prevention. A population-based study.

BACKGROUND: Complication rates of medical therapy for secondary stroke prevention derived from clinical trials may or may not be applicable to patients with cerebrovascular disease in the general population. OBJECTIVE: To determine complication rates for aspirin, warfarin, and intravenous heparin administered for secondary stroke prevention after first episodes of ischemic stroke, transient ischemic attack, or amaurosis fugax in a community. DESIGN: Population-based historical cohort study. SETTING: Rochester, Minnesota. PATIENTS: All residents of Rochester who, between 1985 and 1989, received aspirin (n = 339) or warfarin (n = 145) within 2 years after first ischemic stroke, transient ischemic attack, or amaurosis fugax or received intravenous heparin (n = 201) within 2 weeks after first ischemic stroke, transient ischemic attack, or amaurosis fugax. MEASUREMENTS: Occurrence of major complications caused by therapy. RESULTS: Twenty aspirin-associated complications (1 fatal) occurred during an average 1.7 years of treatment, 8 warfarin-associated complications occurred during an average 0.7 years of treatment, and 3 heparin-associated complications (1 fatal) occurred during an average 5.1 days of treatment. Complication rates were 3.5 per 100 person-years (95% CI, 2.1 to 5.4) for aspirin, 7.9 per 100 person-years (CI, 3.4 to 15.6) for warfarin, and 0.30 (CI, 0.06 to 0.86) per 100 person-days for heparin. Rates of fatal complications were 0.2 per 100 person-years (CI, 0 to 1.0) for aspirin, 0 per 100 person-years (CI, 0 to 3.6) for warfarin, and 0.10 per 100 person-days (0 to 0.55) for heparin. CONCLUSIONS: Complication rates for warfarin and intravenous heparin given as therapy for secondary stroke prevention in Rochester, Minnesota, were lower than rates reported from earlier trials and observational studies. However, complication rates for warfarin were higher than in more recent referral-based studies and multicenter randomized trials. After adjustment for duration of therapy, complication rates for heparin were higher than those for aspirin or warfarin. These rates can be used to judge the applicability of complication rates derived from ongoing clinical trials.

Aged↗
PubMed1999

Subarachnoid Hemorrhage.

All patients who present with subarachnoid hemorrhage should be admitted to the intensive care unit for close neurologic and cardiorespiratory monitoring. Neurosurgical consultation should be obtained if external ventricular drain placement, arteriography, or surgical planning are considered. Seizure prophylaxis, antihypertensive treatment for mean arterial blood pressure greater than 130 mm Hg, pain control, and bed rest are important measures for the prevention of rebleeding, which is associated with a high mortality rate. Standard deep venous thrombosis and gastrointestinal prophylaxis are recommended to prevent medical complications associated with critical illness. In patients with good-grade subarachnoid hemorrhage, early arteriography and definitive aneurysm management are recommended. The location and neck size of the aneurysm and the medical condition of the patient are factors in the decision to proceed with surgical rather than interventional aneurysm management. Postoperatively, clinical examination and transcranial Doppler ultrasonography are recommended for surveillance of vasospasm. If clinical or arteriographic evidence of vasospasm is present, hemodilution, hypertension, and hypervolemia (triple H) therapy should be instituted. If vasospasm is resistant to conservative measures, balloon angioplasty or intra-arterial papaverine therapy should also be considered.

Journal Article↗
PubMed1999

Localization of alpha1B-adrenergic receptor in female rat brain regions involved in stress and neuroendocrine function.

Activation of alpha1-adrenergic receptors has been linked to the control of blood pressure, neuroendocrine secretion, reproductive behavior and mood. The present study describes the distribution of alpha1B-adrenergic receptor immunoreactivity in female rat brain regions involved in stress and neuroendocrine function. The pattern of immunolabeling seen resembles that obtained in previous in situ hybridization studies. Several hypothalamic areas that control pituitary function showed intense fiber and/or cell immunolabeling, including the paraventricular nucleus of the hypothalamus, the supraoptic nucleus, and the median eminence. Some regions such as the arcuate nucleus, the median eminence, and dorsal hypothalamus exhibit intense labeling of axonal varicosities, while other regions exhibit only perikarya immunolabeling. alpha1B-adrenergic receptor immunoreactivity was also observed in large pyramidal neurons of layer V of the cerebral cortex, the frontal cortex showing a particularly strong immunoreactivity. Virtually all thalamic regions were labeled, especially the lateral and ventral areas. In addition, labeled cells were present in hippocampus, the medial septum, the horizontal and vertical limbs of the diagonal band of Broca, and the caudate putamen. Finally, some midbrain and hindbrain regions important for motor function were immunoreactive. Because ligands specific for alpha1-adrenergic receptor subtypes are not available, the present immunocytochemical study not only addresses the subcellular and regional distribution of alpha1B-adrenergic receptors but may also provide clues about receptor subtype-specific function.

Animals↗
PubMed1999

The effect of ACTH on the GnRH-induced release of LH and testosterone in male white-tailed deer.

In order to investigate the possible link between stress and the impairment of the reproductive system, 12 yearling white-tailed bucks, born to mothers captured wild in southern Texas, were immobilized every 6 weeks over the period of 1 year. In half of experiments deer were injected i.m. with 20 i.u. of ACTH; in the second half, we used saline only. Simultaneously, in each experiment we also injected all deer i.m. with 100 micrograms of GnRH. Three blood samples were taken before and seven after treatment and plasma levels of cortisol, LH and testosterone (T) were later measured by RIA. Half of our yearlings were born to mothers which were fed high-protein-high-energy (HP-HE) diet during their pregnancy; the other half ws fed high-protein-low-energy diet (HP-LE). ACTH increased cortisol levels in both nutritional regimes. Cortisol levels in controls decreased with time but a more pronounced reduction was observed in HP-HE bucks as compared to HP-LE deer. GnRH significantly increased LH and T levels. However, only in summer, LH levels were higher in HP-LE fed deer than those fed HP-HE; in other seasons they were equal. Conversely, only in winter T levels were elevated in HP-HE fed deer as compared with HP-LE deer. We concluded that the pronounced suppression of reproductive hormones by ACTH or cortisol reported previously in domestic ungulates does not occur in white-tailed deer yearlings. Conversely, the low level of energy provided in food to mothers during their pregnancies significantly reduced peak levels of testosterone in their male offspring. This study further proved that white-tailed deer is a highly adaptable cervid species resistant to environmental stress.

Adrenocorticotropic Hormone↗
PubMed1999

Nonaneurysmal thunderclap headache with diffuse, multifocal, segmental, and reversible vasospasm.

OBJECTIVE: To highlight the clinical profiles and angiographic findings of two patients with recurrent thunderclap headache (TCH) without subarachnoid hemorrhage (SAH) and to present modified diagnostic criteria for this unusual syndrome. BACKGROUND: TCH may be a benign recurrent headache disorder or it may represent a serious underlying process such as SAH or venous sinus thrombosis. The pathophysiology of this disorder in the absence of underlying pathology is not well understood and its potential angiographic features are not well appreciated. METHODS: Two case descriptions with illustrative angiography. RESULTS: Both cases demonstrated the potential for reversible intracranial vasospasm without intracranial aneurysm or SAH and a benign clinical outcome. CONCLUSIONS: Primary TCH has a distinctive clinical and angiographic profile and must be distinguished from central nervous system vasculitis and SAH.

Headache↗
PubMed1999

Autoimmune pancreatitis, pancreatic mass, and lower gastrointestinal bleed.

Autoimmune pancreatitis (AIMP) is a recently described clinical entity causing chronic pancreatitis. It often presents with diffuse enlargement of the pancreas and/or a focal mass at the head of the pancreas causing common bile duct obstruction and jaundice. In most instances, AIMP is mistaken for pancreatic cancer. A number of laboratory abnormalities such as positive antinuclear antibody, hypergammaglobulinemia, and antibody to carbonic anhydrase are often present in these patients. Currently, pancreatic biopsy demonstrating characteristic histopathologic changes is essential to establish the diagnosis. We report the first case of AIMP presenting as a pancreatic tail mass and lower gastrointestinal bleed.

Adult↗
PubMed1999

Genetic determinants of blood pressure regulation.

Blood pressure homeostasis in humans reflects the coordinate interactions of cardiac output, peripheral vascular resistance, renal volume control, and CNS integration in response to short- and long-term environmental stimuli. Variations in mean arterial pressure within the population include a significant hereditary component. The clearest examples of this genetic contribution occur in rare forms of monogenic hypertension (glucocorticoid remediable aldosteronism, apparent mineralocoid excess, Liddle's syndrome) or hypotension (pseudohypoaldosteronism type I, Bartter's syndrome, Gitelman's syndrome). Primary hypertension, which comprises approximately 95% of hypertensives and is a major risk factor for coronary heart disease, stroke, and renal disease in the U.S., represents a multifactorial and polygenic disease with incremental contributions from genetic and environmental determinants. Efforts to date have identified several candidate genes involved in primary hypertension, including angiotensinogen (AGT), a vasoactive peptide; alpha-adducin, a protein that regulates sodium transport; and the G protein beta 3 subunit, a protein involved in intracellular signal transduction. Advances in knowledge and technology associated with the Human Genome Project, combined with continuing basic research on the physiologic and biochemical causes of hypertension, offer promise for improved diagnosis and therapy of this prevalent disease.

Angiotensinogen↗
PubMed1999

Ischemic stroke subtypes: a population-based study of incidence and risk factors.

BACKGROUND AND PURPOSE: There is scant population-based information on incidence and risk factors for ischemic stroke subtypes. METHODS: We identified all 454 residents of Rochester, Minn, with a first ischemic stroke between 1985 and 1989 from the Rochester Epidemiology Project medical records linkage system. We used Stroke Data Bank criteria to assign infarct subtypes after reviewing medical records and brain imaging. We adjusted average annual incidence rates by age and sex to the US 1990 population and compared the age-adjusted frequency of stroke risk factors across ischemic stroke subtypes. RESULTS: Age- and sex-adjusted incidence rates (per 100 000 population) were as follows: large-vessel cervical or intracranial atherosclerosis with >50% stenosis, 27; cardioembolic, 40; lacuna, 25; uncertain cause, 52; other or uncommon cause, 4. Sex differences in incidence rates were detected only for atherosclerosis with stenosis (47 [95% CI, 34 to 61] for men; 12 [95% CI, 7 to 17] for women). There was no difference in prior transient ischemic attack and hypertension among subtypes, and diabetes was not more common among patients with lacunar infarction than other common subtypes. CONCLUSIONS: The age-adjusted incidence rate of stroke due to stenosis of the large cervicocephalic vessels is nearly 4 times higher for men than for women. There is no association between preceding transient ischemic attack and stroke mechanism. Diabetes and hypertension are not more common among patients with lacunae. Age- and sex-adjusted incidence rates for ischemic stroke subtypes in this population can be compared with similarly determined rates from other populations.

Adult↗
PubMed1999

Use of nursing home after stroke and dependence on stroke severity: a population-based analysis.

BACKGROUND AND PURPOSE: There are few population-based data available regarding nursing home use after stroke. This study clarifies the use of a nursing home after stroke, as well as its dependence on stroke severity, in a defined population. METHODS: All first stroke events among residents of Rochester, Minn, during 1987-1989 were ascertained, subtyped, and assigned Rankin disability scores (RS) before the event, at maximal deficit, and at specified intervals after stroke. Persons were followed from the date of stroke event to death, emigration from Rochester, or December 31, 1994, in complete community-based medical records and Minnesota Case Mix Review Program data tapes to determine nursing home residency before stroke and at 90 days and 1 year after stroke, proportion of survival days in a nursing home, and cumulative risk of admission to a nursing home. RESULTS: There were 251 cases of first cerebral infarction, 24 intracerebral hemorrhages, and 15 subarachnoid hemorrhages among residents of Rochester during 1987-1989. The maximal deficit RS was 1 or 2 for 62 (25%), RS 3 for 72 (29%), and RS 4 or 5 for 117 (47%) of the cerebral infarct patients. Among patients surviving to 90 days or 1 year after cerebral infarction, 25% were in nursing home at 90 days and 22% at 1 year, respectively. Within these maximal deficit RS categories, the percentages of follow-up time spent in a nursing home during the first post-cerebral infarction year are as follows: RS 1 to 2, 4%; RS 3, 10%; and RS 4 to 5, 54%. Multivariate logistic regression revealed that increasing age and RS 4 to 5 at maximal deficit were independent predictors (P<0.0001) of nursing home residency at 90 days and 1 year after stroke, whereas stroke type was not an independent predictor. At 1 year after cerebral infarction, the Kaplan-Meier estimates of proportion of people with at least 1 nursing home admission were 11% for RS 1 to 2, 22% for RS 3, and 68% for RS 4 to 5. CONCLUSIONS: This study provides unique population-based data regarding the short- and long-term use of a nursing home after stroke and its dependence on stroke severity. More than 50% of people with a severe cerebral infarction are in a nursing home 90 days and 1 year after the stroke, and by 1 year, nearly 70% will have required some nursing home stay. Age and stroke severity are independent predictors of nursing home residency after stroke.

Aged↗
PubMed1999

Multiple cerebral infarctions from nonbacterial thrombotic endocarditis mimicking cerebral vasculitis.

Primary vasculitis of the central nervous system (PVCNS) is an uncommon disorder that can present with a variety of symptoms, making diagnosis and management difficult. We describe a case of cerebral infarction that occurred from nonbacterial thrombotic endocarditis (NBTE) and presented with clinical and radiologic imaging features that suggested PVCNS. The patient was a 58-year-old woman with left hemiparesis, aphasia, and episodic confusion. Magnetic resonance imaging of the brain demonstrated multifocal lesions consistent with infarction involving both cerebral hemispheres, and cerebral angiography showed changes consistent with vasculitis. Although brain biopsy findings were normal, the patient was treated for presumed vasculitis with cyclophosphamide and prednisone. Four months later respiratory failure secondary to polymicrobial pneumonia and adult respiratory distress syndrome developed, and she died. Autopsy revealed multiple infarcts in the heart, lungs, right kidney, spleen, and brain. Multiple thrombotic platelet-fibrin vegetations consistent with NBTE were found on all cardiac valves. Examination of the brain revealed no evidence of active or healed vasculitis. Cerebral angiography may show findings that suggest vasculitis, but it is not diagnostic, as several other conditions may cause similar changes. Nonbacterial thrombotic endocarditis may cause multiple cerebral infarctions and can be difficult to distinguish from vasculitis, as specific diagnostic tests for PVCNS are lacking.

Autopsy↗
PubMed1999

Carotid artery tandem lesions: frequency of angiographic detection and consequences for endarterectomy.

BACKGROUND AND PURPOSE: Several prospective trials have shown that ischemic stroke can be prevented by performing an endarterectomy in patients with high-grade carotid stenosis. Our purpose was to ascertain the frequency of carotid artery tandem lesions and to determine whether their presence alters the surgeon's decision to perform an endarterectomy. METHODS: We retrospectively reviewed the cerebral angiograms obtained between January 1994 and June 1996 in 853 patients with carotid occlusive disease. Studies were analyzed for the presence of internal carotid artery (ICA) stenosis as well as for tandem lesions (defined as > or = 50% diameter stenosis) within the common carotid artery, carotid siphon, or proximal intracranial arteries. The frequency of intracranial saccular aneurysms was determined. RESULTS: Six hundred seventy-two of the 853 patients had a carotid bifurcation stenosis of 70% or greater or underwent an endarterectomy. Of these, a carotid siphon stenosis of 50% or greater was noted in 65 patients (9.7%) and was ipsilateral to an ICA stenosis in 37 patients (5.5%). A common carotid stenosis was present in 29 patients (4.3%), ipsilateral to an ICA stenosis in 14 patients (2.1%). A stenosis of 50% or greater within the proximal intracranial circulation was present in 28 patients (4.2%), ipsilateral to an ICA stenosis in 15 patients (2.2 %). Four patients had tandem stenoses at more than one site. Tandem stenoses in the siphon or intracranial segments were noted in 13.5% with a bifurcation stenosis and in 8.8% of those with no bifurcation stenosis. Endarterectomy was performed in 48 of the 66 patients with tandem stenotic lesions. CONCLUSION: The presence of a tandem lesion infrequently alters the surgeon's decision to perform an endarterectomy. However, the importance of detecting tandem stenoses cannot be underestimated, since they may have important implications for long-term medical management in symptomatic patients.

Aged↗
PubMed1999

Quality assurance in the endoscopy unit: An emphasis on outcomes.

This article identifies and reviews key elements of quality improvement programs for an endoscopy unit. The new paradigm of quality improvement seeks to improve all performance, and does not simply focus on the low outliers as in the traditional "quality assurance" program. The organization and key elements are emphasized, including selection of key indicators and methodologies for the development of standards of practice and benchmarks. Examples of quality improvement initiatives are discussed, demonstrating their value in improved patient care and the process or function of an endoscopy unit.

Endoscopy, Gastrointestinal↗