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Biomedical subjects

B D Snyder

Publications and source records attributed to B D Snyder.

At least 37 records · Page 2Linked to original sources
PubMed1987

Can embolic stroke be diagnosed on the basis of neurologic clinical criteria?

Diagnosis of embolic stroke is based on identification of a source of embolus (SOE) and on neurologic symptoms acknowledged as "clinical criteria." To test the validity of these criteria, we analyzed the symptoms at onset in 193 patients hospitalized after acute cerebral infarction. Patients were grouped according to identification of a cardiac SOE (106 patients), an arterial SOE (38 patients), or no SOE (49 patients). Cross-tabulations demonstrated that only rapidity and loss of consciousness at onset were associated with the presence of a cardiac SOE to a significant degree. Although these symptoms were highly specific for cardiac SOE, they were not sensitive. A distinct clinical neurologic profile from the symptoms and mode of onset was not identified.

Adult↗
PubMed1987

Trabecular bone remodeling around smooth and porous implants in an equine patellar model.

The objective of this investigation was to examine the stress-morphology relationships for trabecular bone around implants with different surface characteristics. Stainless steel spheres with either a polished surface or a sintered-bead porous coating were implanted unilaterally into equine patellae and maintained for a 6 month period. Stereological methods were used to quantify the trabecular bone morphology and finite element analyses were performed to predict the trabecular bone stresses. In general, the remodeling response around the smooth implants was greater than that around those porous implants that exhibited bone ingrowth. In accordance with these differences, the finite element models predicted greater changes in the stresses adjacent to the smooth implants due to the nonlinear boundary conditions. However, it did not appear that the trajectorial theory, in its simplest form, was applicable to the remodeling induced by the implants. A linear relationship between the change in bone areal density and the change in von Mises effective stress provides support for the hypothesis that the architecture of trabecular bone corresponds to an optimal structure. The results also demonstrated that, under certain circumstances, small changes in the stress state may result in large changes in the principal material orientation.

Animals↗
PubMed1987

Emergency carotid artery thrombectomy for postpartum hemiplegia.

The case of a 22-year-old patient who suffered from postpartum hemiplegia due to thrombosis of the internal carotid artery is reported. She was treated aggressively with pentobarbital coma, angiography, and thrombectomy and recovered with minimal deficit.

Adult↗
PubMed1987

Aneurysmal subarachnoid hemorrhage presenting as cardiorespiratory arrest.

Three cases of subarachnoid hemorrhage (SAH) due to ruptured developmental (berry) aneurysm are reported. Two patients presented with cardiac arrest and were successfully resuscitated, but the diagnosis of SAH was delayed and this most likely influenced poor final outcome. The third patient presented with irreversible respiratory arrest. The possible mechanisms responsible for SAH-triggered cardiac arrhythmia and/or respiratory arrest are discussed. Absence of previous cardiac history, persistent headache, focal neurologic findings (especially papilledema or subhyaloid hemorrhages) should warn the clinician of the possibility of SAH and warrant further neurologic investigation.

Arrhythmias, Cardiac↗
PubMed1986

Mannitol pharmacokinetics and serum osmolality in dogs and humans.

The relationship between mannitol pharmacokinetics and changes in serum osmolality were studied in dogs and humans. Four human subjects each received between 0.5 and 0.7 g/kg of mannitol as an i.v. infusion given over 15 min. Intravenous bolus doses of 0.5, 1.0 and 1.5 g/kg were given to each of five animals. Serial determinations of serum osmolality and serum mannitol concentrations were then performed. Mannitol disposition was best described using a biexponential equation and assuming a two-compartment, open model with elimination from the central compartment. For human subjects, the mean (+/- S.D.) distribution half-life was 2.11 +/- 2.67 min and the elimination half-life was 71.15 +/- 27.02 min. The volume of distribution was 0.47 +/- 0.50 liters/kg and total body clearance was 7.15 +/- 10.23 ml X min-1 X kg-1. The disposition of mannitol in dogs is similar to that observed in humans. Mannitol clearance was independent of dose whereas the central compartment volume was significantly larger (P less than .005) in animals receiving the 1.5-g/kg dose. The volume change is probably due to a rapid, uncompensated shift of water from intracellular to extracellular space. There was a strong positive correlation (r = 0.90) between mannitol concentration and serum osmolality changes. However, neither maximum serum mannitol concentration nor maximum serum osmolality increased proportionately with dose. Only the 1.5-g/kg dose produced a sustained elevation of serum osmolality, confirming that larger doses are more likely to result in prolonged hypertonic dehydration.

Adult↗
PubMed1985

Stress analysis of a condylar knee tibial component: influence of metaphyseal shell properties and cement injection depth.

We generated three-dimensional finite element models of the proximal tibia with an implanted tibial component. The component features a cobalt-chromium tray with four short vertical posts and a porous-coated surface for improved fixation to polymethylmethacrylate (PMMA). We examined the stresses after varying: the structural rigidity of the metaphyseal cortical shell; the surface area of the cobalt-chromium tray; and the depth of pressure-injected PMMA bone cement. Our results indicate that previous finite element models of prosthetic tibial components have overestimated the structural contribution of the metaphyseal cortical shell by a factor of approximately 6. A standard size tray, in contrast to a tray that extends to the cortical shell, does not significantly alter the axial load distribution but could result in bone resorption beyond the tray periphery. An important consequence of the component peg locations is that they direct the compressive stresses into dense regions of trabeculae that run from the subchondral articular surface to the metaphyseal-diaphyseal junction. The use of a modified von Mises failure criterion suggests that at excessive load levels the most likely location of material failure is at the bone cement-trabecular bone interface immediately distal to the fixation posts. Due to its added rigidity, injection of cement beyond the fixation posts results in slightly increased stresses in this region, but these stress increases are compensated for by an increased strength of the cement-bone composite.

Bone Cements↗
PubMed1983

Compressed spectral array patterns following cardiopulmonary arrest. A preliminary report.

Continuous taped EEG recordings were made following resuscitation in 18 survivors of cardiopulmonary arrest. These taped data were processed, using Bickford's method of compressed spectral array, and four distinctive patterns were recognized. These patterns correlated significantly with eventual outcome of these patients, suggesting that processed EEG information can provide important prognostic information for such patients.

Brain↗
PubMed1983

Posttraumatic intention myoclonus.

A patient with long-standing intention myoclonus was treated with oral clonazepam, which resulted in clinical and electrophysiologic improvement as manifested by dramatic reduction in intention myoclonus and diminished amplitude of somatosensory evoked potentials after treatment.

5-Hydroxytryptophan↗
PubMed1982

Medical complications of cardiopulmonary arrest.

The clinical courses of 63 survivors of cardiopulmonary arrest were reviewed to determine the incidence and temporal occurrence of noncardiac complications and their relationships to mortality. Complications were grouped as occurring within 48 hours or less, within 48 to 96 hours, or more than 96 hours after cardiopulmonary arrest. Pneumonia, electrolyte level disturbances, and gastrointestinal tract hemorrhage each occurred in more than 28 (45%) of the 63 patients. Resuscitation-related injuries, seizures, and liver function test abnormalities each occurred in at least 18 (28%) of the 63 patients. Pneumonia and liver function test abnormalities were each significantly correlated with increased mortality. Septicemia, acute renal failure, and adult respiratory distress syndrome each occurred in three (5%) to four (7%) of the 63 patients and were always associated with mortality.

Acute Kidney Injury↗
PubMed1981

ACTH-induced cortisol production in multiple sclerosis.

We measured the total daily urinary cortisol produced by each of 8 patients with multiple sclerosis during intravenous therapy with adrenocorticotropic hormone (ACTH). Results indicated marked daily variation from patient to patient as well as in the same patient, suggesting that ACTH infusions do not result in reliable, consistent, high-level production of cortisol. We attempted to express the quantity of cortisol produced as an equivalent amount or oral prednisone. This comparison is difficult to make; but, given certain assumptions, the figures suggest that 40 U or 80 U ACTH infusions do not elicit the quantities of steroid generally considered to be indicated for the therapy of major allergic, autoimmune, or neoplastic diseases.

Administration, Oral↗
PubMed1981

Improved enzymatic method for determining mannitol and its application to dog serum after mannitol infusion.

An enzymatic method for mannitol quantitation has been developed. Its application mannitol levels in serum samples from dogs after mannitol infusion is illustrated. The method is based on the spectrophotometric measurement of the initial rate of NADH formation in the reaction between mannitol and NAD catalyzed by mannitol dehydrogenase. A linear relationship between initial rates and mannitol concentration is seen between 17 mumol/l and 6.7 mmol/l mannitol. From the extent of dilution of the serum sample in the assay this corresponds to serum levels of 0.5 to 200 mmol/l. Because of the high degree of substrate specificity of mannitol dehydrogenase and the extensive dilution of the serum sample in the assay reaction mixture, serum proteins and glucose do not interfere with the reaction. As a result, pre-treatment of samples to remove glucose and deproteinization are necessary.

Animals↗
PubMed1980

Neurologic prognosis after cardiopulmonary arrest: III. Seizure activity.

Nineteen (30%) of 63 adult survivors of cardiopulmonary arrest had seizures after admission to the hospital. Eleven of 19 had more than one type of seizure. Myoclonic seizures began within 12 hours of the arrest in eight patients, and after 3 or more days in four patients. Only two (17%) patients with myoclonic seizures survived. Partial seizures usually began within 12 hours of the arrest and were controllable with anticonvulsants; 4 of 12 patients survived. Two of four patients with generalized tonic-clonic seizures survived; one of four with "shivering" lived. Overall, patients with seizures had a survival rate of 32% (6 of 19), compared with 43% for patients without seizures. None of the survivors had recurrent seizures within 6 months after hospital admission.

Adult↗
PubMed1979

Delayed meningitis following stapes surgery.

Perilymphatic fistulae, developing even years after stapedectomy, open a communication between the perilymph and middle ear. These fistulae constitute a potential pathway for flora of the middle ear to invade the subarachnoid space by way of the cochlear aqueduct. Our patient developed pneumococcal meningitis 14 months after stapedectomy. The history of stapedectomy in a patient with meningitis is an indication for reexploration+ion of the operative site. The appearance of fistula symptoms in patients who have had stapedectomy indicates a high risk for development of intracranial infection.

Ear, Middle↗