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Biomedical subjects

S W Miller

Publications and source records attributed to S W Miller.

At least 37 records · Page 2Linked to original sources
PubMed1995

Malfunction of implantable cardioverter defibrillators placed by a nonthoracotomy approach: frequency of malfunction and value of chest radiography in determining cause.

OBJECTIVE: The purpose of this study was to determine the frequency of system malfunction in patients with nonthoracotomy implantable cardioverter defibrillators and to assess the role of chest radiography in detecting and determining the cause of malfunction. MATERIALS AND METHODS: The study population consisted of 300 consecutive patients in whom implantable cardioverter defibrillators were implanted using an initial nonthoracotomy approach between September 1990 and October 1994. Transvenous electrodes were placed via the subclavian or cephalic vein under local anesthetic. Intraoperative testing, pulse generator implantation, and, if necessary, subcutaneous patch or extrapericardial patch placement via thoracotomy were done in the operating room under general anesthetic. Follow-up consisted of routine device interrogation every 2-3 months and annual chest radiography. Chest radiographs were obtained more often if patients were symptomatic or if results of device interrogation were abnormal. RESULTS: Patients were followed up for a mean +/- SD of 19 +/- 14 months following implantation. Implantable cardioverter-defibrillator malfunction occurred in 17 patients (6%) during the follow-up period. Of these, 12 (71%) had component abnormalities on chest radiographs. Patients with radiographically apparent implantable cardioverter-defibrillator abnormalities presented in two discrete time periods after device implantation, early (mean, 35 +/- 14 days) and late (mean, 18 +/- 5 months). CONCLUSION: Malfunction of nonthoracotomy implantable cardioverter-defibrillator systems develops infrequently after device implantation. In most cases, the cause can be identified on chest radiographs.

Adolescent↗
PubMed1994

Recovery of medial gastrocnemius muscle grafts in rats: implications for the plantar flexor group.

Medial gastrocnemius (MGN) muscles were grafted in 18 rats and evaluated at 60, 90, and 120 days after the operation. Our purpose was to investigate the degree of recovery of the vascularized MGN grafts and the entire plantar flexor muscle group. Compared with control values, muscle mass and maximum force of MGN grafts were decreased by 33 and 38% at 60 days, 22 and 32% at 90 days, and 13 and 15% at 120 days. At 60 and 90 days, the deficits in maximum force for the entire plantar flexor muscle group, including the graft, were 29 and 17%, respectively. No difference was observed at 120 days. At 60 days, the deficit in the total mass of the plantar flexor group was 14% compared with control values, but by 90 days no deficit was observed. The restoration of normal plantar flexor group structure and function indicates that the degree of recovery attained by MGN grafts, although not complete, was sufficient to ensure that the performance of the total muscle group was not compromised.

Adaptation, Physiological↗
PubMed1993

Differentiation of slow flow from thrombus in thoracic magnetic resonance imaging, emphasizing phase images.

Magnetic resonance (MR) examinations are used with increasing frequency to augment and replace other imaging modalities when a cardiovascular abnormality or thrombosis is suspected clinically. Because the signal intensity of flowing blood can vary greatly and can suggest the diagnosis of an intravascular mass, different pulse sequences and other imaging strategies may be needed to differentiate between flowing blood and intravascular thrombus. Some techniques image flowing blood as a signal void (black blood), whereas other methods enhance its signal intensity (white blood). Phase reconstruction, MR cine angiography, and related techniques that are sensitive to flow are assuming more importance in clinical MR diagnosis and are now replacing cardiac and thoracic angiography in selected clinical situations.

Blood Flow Velocity↗
PubMed1993

New high-resolution teleradiology system: prospective study of diagnostic accuracy in 685 transmitted clinical cases.

To compare the accuracy of interpretation of digitized radiographs with that of plain films, the authors prospectively evaluated the first 685 plain film cases (530 adult and 155 pediatric cases, each of which consisted of one or more images) transmitted from an outpatient center 18 miles (approximately 29 km) to a hospital radiology department by means of a high-speed teleradiology system. Plain films were digitized and transmitted via a T-1 (1.544 Mbit/sec) data link for display on high-resolution (2,560 x 2,048-pixel) workstations. Radiologists at the hospital used a copy of the radiology requisition that had been faxed from the remote center. Interpretation of the digital images was followed by review of the original plain radiographs within 1 working day. Discrepant interpretations occurred in 18 cases (2.6%) (sensitivity, 96%; specificity, 99%); an arbitration panel decided that they were associated with observer performance more than with the fidelity of the digital display. It is concluded that primary diagnosis without review of the original plain radiographs is feasible with state-of-the-art teleradiology systems.

Prospective Studies↗
PubMed1992

Therapeutic frontiers in Alzheimer's disease.

Alzheimer's disease (AD), the most common type of primary degenerative dementia, is the leading cause of cognitive impairment in the geriatric population. It is a devastating illness, both to the patients and the families involved. Although much research continues to be conducted, the etiology and effective treatment for the disease remain to be found. One of the primary hypotheses of the disease is that the cognitive decline of AD involves the loss of related cholinergic neurons. Although the cholinergic theory is still valid, efforts aimed at increasing levels of acetylcholine have yielded disappointing results. Currently, in the United States, several drugs are in various stages of development for the treatment of AD. The mechanisms of these agents include cerebral protectants, enhancers of neuronal signal amplification, tonic stimulation, and nerve growth factors. Other avenues being investigated include the development of novel drug delivery systems to enhance CNS concentrations of therapeutic agents.

Aged↗
PubMed1991

Stability and compatibility of methylprednisolone sodium succinate and cimetidine hydrochloride in 5% dextrose injection.

The stability and compatibility of methylprednisolone sodium succinate in admixtures with cimetidine hydrochloride in 5% dextrose injection were determined. Admixtures containing methylprednisolone sodium succinate, in concentrations equivalent to methylprednisolone 0.4 or 1.25 mg/mL, and cimetidine 3 mg/mL (as the hydrochloride salt) were prepared in 5% dextrose injection 100 mL. Control solutions containing each drug alone at the same concentrations were also prepared. The admixtures were prepared in triplicate and were kept in polyvinyl chloride infusion containers at controlled room temperature (24 degrees C). Immediately after mixing and at 2, 4, 8, 12, and 24 hours, samples were removed and visually inspected, measured for pH, and assayed by stability-indicating high-performance liquid chromatography to determine the concentrations of methylprednisolone 21-succinate ester and cimetidine. No visual evidence of incompatibility was noted either with the unaided eye or a microscope. No substantial changes in pH occurred over the study period. The addition of cimetidine decreased the pH of the methylprednisolone sodium succinate control solutions from about 7.3 to about 5.6. The concentrations of methylprednisolone 21-succinate ester and cimetidine in both test and control solutions did not change significantly over the 24-hour study period. Methylprednisolone sodium succinate, in concentrations equivalent to methylprednisolone 0.4 and 1.25 mg/mL, was chemically stable and visually compatible in admixtures with cimetidine 3 mg/mL (as the hydrochloride salt) in 5% dextrose injection 100 mL at 24 degrees C for 24 hours.

Cimetidine↗
PubMed1990

Stability of drugs with enteral nutrient formulas.

Experiments were performed to determine the chemical stability and compatibility of cephalexin, cimetidine, diazepam, or propranolol with full-strength and half-strength Isocal, Sustacal, and Sustacal HC (Mead Johnson). The enteral nutrient formulas (ENFs) containing the solid or liquid dosage forms were stored at 24 degrees C and samples were taken at times 0, 1.5, 3, 6, 8, 10, and 24 hours. At each sampling time, the mixtures were visually examined for signs of incompatibilities such as precipitation, viscosity changes, and phase separation. Samples from each time period were analyzed by a stability-indicating high-performance liquid chromatography (HPLC) method. The drugs mixed with half-strength ENFs were also passed through ultrafiltration membranes to separate complexed from uncomplexed drug. Neither visual changes nor variations in pH were observed in any formula. With the exception of cephalexin suspension in half-strength ENFs, none of the drug concentrations changed appreciably throughout the study period. The assays performed for undecomposed drug at each sampling time for the various full- or half-strength ENF-solid drug mixtures stored at 24 degrees C for 24 hours ranged from 92.3 to 103.4 percent for cephalexin, 96.2 to 103.0 percent for cimetidine, 93.9 to 106.2 percent for diazepam, and 95.5 to 102.2 percent for propranolol. For the liquid drugs, the concentration ranged from 86.5 to 102.0 percent for cephalexin, 97.0 to 101.1 percent for cimetidine, 98.2 to 103.0 percent for diazepam, and 97.4 to 104.8 percent for propranolol. Ultrafiltration studies showed varying percent binding dependent on the drug studied.

Chromatography, High Pressure Liquid↗
PubMed1990

Nursing theory. Nightingale & Roy--a comparison of nursing models.

1. Today, in an effort to develop the profession of nursing, nurses are working to base nursing actions on a theoretical model. 2. There are four reemerging themes evidenced in both the Nightingale and Roy models, including environment, person, health, and nursing. 3. The Roy and Nightingale models share more similarities than differences: both describe their metaparadigm (ie, environment, person, health, and nursing) in relation to their models.

Humans↗
PubMed1989

Coronary artery calcifications: significance of incidental detection on CT scans.

A scoring system was devised for the assessment of coronary artery calcifications apparent on computed tomographic (CT) scans, with width and length used to assess severity. The degree of calcification was compared with the presence of stenoses of 70% or greater at cardiac catheterization in 46 patients who underwent both studies. Although many significantly stenosed vessels showed no calcification, heavy calcifications had a high positive predictive value for significant disease. In a separate branch of the study, the perioperative cardiac morbidity and mortality were compared in 30 age- and sex-matched pairs of patients undergoing thoracotomy who did and did not have coronary calcifications on CT scans obtained before surgery. Patients with calcifications had a higher frequency of cardiac complications, including arrhythmias, ischemia, hypotension, myocardial infarction, and death.

Adult↗
PubMed1989

Imaging pericardial disease.

Pericardial disease has a variety of presentations depending upon whether the pericardium is absent, is thickened from inflammation or tumor, or constrains fluid under pressure, thereby restricting cardiac filling and output. The choice of an imaging modality is influenced by a number of factors: the anticipated presence of calcium, cardiac motion, spatial and contrast resolution required, adequate imaging window into the mediastinum, contrast media requirements, and clinical situation. Although many of the imaging modalities discussed herein have common features, some offer unique attributes, namely motion analysis, fat and water discrimination, and calcium detection. The complexity of many pericardial problems plus the risk of pericardial surgery not uncommonly require a multimodality imaging approach for complete definition.

Heart Diseases↗
PubMed1987

The complications of surgical treatment of displaced fractures of the olecranon.

Forty-eight patients who had undergone internal fixation of a displaced fracture of the olecranon by either a tension band technique (34 patients) or screwing (14 patients) were reviewed. The functional results after at least 2 years were equally good with both methods, but there was a considerably higher rate of separation at the fracture after screwing than after inserting a tension band. The technical quality of the fixation was open to criticism in half the cases in each group, and the implications of this are discussed.

Adult↗
PubMed1987

Intratympanic injection of sodium arsanilate (atoxyl) solution results in postural changes consistent with changes described for labyrinthectomized rats.

Intratympanic injections of sodium arsanilate (atoxyl) have been shown to produce vestibular dysfunction in the rat. Unilateral and bilateral dysfunction can be distinguished by changes in the animals' postures. These changes are consistent with changes described for unilateral or bilateral labyrinthectomized rats. The intratympanic injection technique offers a simple yet effective alternative to labyrinthectomy.

Animals↗
PubMed1987

Gallium-67 and magnetic resonance imaging in aortic root abscess.

Perivascular abscess in the aortic root is a serious complication of infective endocarditis and is recognized infrequently with noninvasive techniques. This report describes a patient with sepsis who was imaged with 67Ga and magnetic resonance (MR) in order to locate a site of infection. The 67Ga image showed increased activity in the substernal region. Magnetic resonance correctly detected the multilocular aortic root abscess, which had extended into the interatrial septum. The combination of the sensitive 67Ga with the high-resolution MR image provided a useful method to locate aortic root abscesses and to identify contiguous spread.

Abscess↗
PubMed1986

Static and sequential dynamic scintigraphy of the tibia following fracture.

Eighty patients who had sustained a fracture of the tibial shaft were studied by scintigraphy using technetium-99m labelled methylene diphosphonate (99Tcm MDP) and a gamma camera. Static scintigrams were obtained in the early stages following injury and examined for the presence of 'cold spots' which may indicate loss of blood supply to fracture fragments; these were found in 10 per cent of cases but did not bear any definite relationship to the normal progression of union. Sequential dynamic scintigrams were obtained at intervals up to 20 weeks after fracture to determine whether a pattern of uptake of tracer could be identified which correlated with the subsequent progression of union, but no significant difference was observed between fractures healing promptly (less than 20 weeks) and those in which healing was delayed (greater than 20 weeks).

Adolescent↗
PubMed1986

Ejection fraction determination by MR imaging: comparison with left ventricular angiography.

To determine the accuracy of left ventricular ejection fractions (EFs) calculated from magnetic resonance (MR) images, 22 patients who underwent coronary angiography and left ventriculography were studied within 1-3 days by MR imaging. ECG-gated spin-echo 30-msec echo-delay images were obtained in end systole and end diastole in a plane through the long axis of the left ventricle perpendicular to the septum at a level through the aortic valve and apex. The area-length method was then used to calculate the EF from left ventriculograms and MR images. Angiographic EF correlated linearly with MR determinations. The mean differences in EF calculation between two observers were 5.0 +/- 6.9 for ventriculography and 2.7 +/- 7.8 for MR imaging. MR imaging, using image planes oriented to the left ventricular axes, can allow accurate EF calculation. This has the potential to be clinically useful in noninvasive evaluation of cardiac function.

Adult↗