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Biomedical subjects

J R Stewart

Publications and source records attributed to J R Stewart.

At least 73 records · Page 4Linked to original sources
PubMed1992

Twenty years' experience with pulmonary metastasectomy.

From January 1969 through December 1989, 63 patients had 69 operations for pulmonary metastases. Patients ranged in age from 1 to 75 years; there were 36 men and 27 women. Metastasectomy was accomplished through a thoracotomy incision in 59 cases (5 staged, bilateral), and median sternotomy was used in 10 instances. Wedge resection was performed in 54 patients, with segmentectomy in 2, lobectomy in 12, and pneumonectomy in 1. There were no operative deaths. Multiple metastases were present in 29 patients, and a single metastasis in 34. Follow-up ranges from 2 to 204 months (mean = 42 months). Thirty-eight patients remain alive; thirty are free of disease and eight have developed other metastases. Actuarial survival at 5, 10, and 15 years is 40 (CL [confidence limits] 49,31), 36 (CL 44,26), and 24 (CL 35,13) per cent, respectively. Mean actuarial survival is 84 months, and median survival is 58 months. There is no difference in survival whether metastases were single or multiple. Survival is significantly less in groups with primary sarcoma and melanoma (P = .012). While pulmonary metastases may be a manifestation of terminal disease, metastasectomy has an important role in the multidisciplinary management of selected patients when metastatic disease is confined to the lung. Prolonged survival may be achieved in many patients.

Actuarial Analysis↗
PubMed1991

Change in injuries associated with safety belt laws.

Statewide crash data bases from nine states were subjected to time series analyses to detect changes in injuries associated with onset of seat belt laws in the respective states. In each of 18 analyses involving drivers covered by the law observed casualties were below the number forecast on the basis of prior experience and assuming that no law had been enacted. In the case of others, not covered by the law, observed injuries were equally often above or below forecast. Relative to covered drivers not only were the numbers below forecast, but in 12 of the 18 instances there was a statistically significant indication of an abrupt decrease the month the law began.

Accidents, Traffic↗
PubMed1991

The economy as a factor in motor vehicle fatalities, suicides, and homicides.

The effect of the economy as reflected by employment and unemployment rates on motor vehicle fatalities, suicides, and homicides is examined using several national databases. First, regression models are fit to these fatality data-overall as well as for a variety of age-race-gender subgroups. Then time series models-autoregressive integrated moving average (ARIMA) and structural time series analysis-were fit to the data, both with and without the economic indicators, to examine the relative ability of the models to forecast subsequent fatalities. No evidence was found using any of the modeling techniques that knowledge of yearly values of rates of employment, unemployment, and nonlabor force leads to improved forecasts of the level of motor vehicle fatalities, suicides, or homicides in the total U.S. population or within various subpopulations of interest.

Accidents, Traffic↗
PubMed1991

Pharmacokinetics and pharmacodynamics of oximes in unanesthetized pigs.

The pharmacokinetics and cardiovascular pharmacodynamics of two oximes were studied in unanesthetized pigs. Effects of 2-[(hydroxyimino)methyl]-1-methylpyridinium chloride (pralidoxime chloride; 2-PAM Cl; 50 mumol/kg) were compared with those of 1,1-methylene bis[4(hydroxyiminomethyl) pyridinium] dichloride (methoxime; MMB-4; 100 mumol/kg). Cardiopulmonary parameters were monitored and plasma concentrations of oximes were determined from arterial blood samples taken at intervals over a period of 5 hr postinjection. Plasma concentrations for both oximes were fitted to standard pharmacokinetic models using the computer program PCNONLIN. Average pharmacokinetic parameters were determined for each oxime. Only mild to moderate physiological side effects were detected following intramuscular administration. 2-PAM Cl was more rapidly absorbed and distributed in the blood than MMB-4. Although the latter had a slight lag time to attain detectable levels in the blood, retention time was longer than that of 2-PAM Cl.

Acetylcholinesterase↗
PubMed1991

Dose volume histogram analysis of lung radiation from chest wall treatment: comparison of electron arc and tangential photon beam techniques.

The technique of electron arc irradiation of the post-mastectomy chest wall was developed to improve dose uniformity and to reduce lung irradiation in comparison to that seen with standard chest wall tangent photon beam methods. Because of the cephalocaudal variation in chest wall shape and thickness, electron arc treatment planning requires anatomical detail provided by multiple axial CT images of the thorax. To compare the fixed beam and rotational techniques, computer simulated beams covering the chest wall and internal mammary lymphatics were retrospectively applied to the CT-derived contours obtained during treatment planning for 12 consecutive patients receiving adjuvant chest wall treatment by electron arc. The lung dose distribution for each technique was calculated using heterogeneity corrections. The multiplanar 2-dimensional isodose distributions were summed to provide estimated 3-dimensional dose distributions of integral histograms. These reveal that for most of these patients a modest to large improvement in volume-dose relationship occurs with the electron arc technique.

Breast Neoplasms↗
PubMed1991

Management of primary nonrenal parenchymal malignancies with vena caval thrombus.

We report our experience with the management of 7 primary nonrenal parenchymal malignancies with vena caval tumor thrombus. Included are 3 cases of adrenal cortical carcinoma and 1 each of transitional cell carcinoma, embryonal cell testicular carcinoma, pheochromocytoma and primary small cell carcinoma of the lung with metastases to the kidney. Surgical treatment and followup are presented, as well as a review of the literature. An aggressive surgical approach is warranted because prolonged survivals free of disease are possible.

Adrenal Cortex Neoplasms↗
PubMed1991

Operational evaluation of three commercial configurations of atropine/HI-6 wet/dry autoinjectors.

Commercially manufactured wet/dry autoinjectors containing atropine in solution and powdered HI-6 were evaluated using HPLC for consistency of drug delivery with various solvation times and stability of drugs postsolvation at a temperature of 40 degrees C. Three configurations of autoinjector were tested. System A (SYS A), with a specified mixing time of 5 sec, delivered a volume of 3.0 ml containing 1.86 mg of atropine sulfate and 443 mg of the bispyridinium oxime HI-6 dichloride. System B1 (SYS B1) and System B2 (SYS B2), with specified mixing times of 40 sec, delivered volumes of 2.3 ml containing 2.13 and 2.06 mg atropine citrate and 424 and 545 mg HI-6 dichloride, respectively. Average coefficients of variation for SYS A were 3.4% for atropine and 5.8% for HI-6 and for SYS B1 and B2 were 5.2% for atropine and 7.0% for HI-6 determinations. Stored from 3 to 14 days at 40 degrees C after the autoinjector contents were mixed, SYS A delivered 1.77 mg atropine sulfate and SYS B1 and B2 delivered 2.02 mg atropine citrate. The delivery of HI-6 dichloride decreased with a half-life of 34 days for SYS A, 39 days for SYS B1, and 32 days for SYS B2. This resulted in a decrease to 90% of the respective day 0 amount after 4 (SYS A) or 5 (SYS B1 or B2) days.

Atropine↗
PubMed1991

Heart transplantation in children.

Orthotopic cardiac transplantation has been performed in 15 consecutive neonates and children since 1987. Diagnoses include hypoplastic left heart syndrome (5 patients), critical aortic stenosis with small left ventricle (1 patient), complex cyanotic heart disease (6 patients), and cardiomyopathy (3 patients). Twelve patients survived operation and have been followed from 1 to 45 months. Patients less than 6 years of age are managed with cyclosporine +/- azathioprine; in older patients steroid weaning is attempted. Monitoring for rejection is performed with serial echocardiography in patients under 6 years of age; older patients undergo serial biopsies. Actuarial freedom from rejection was 26% 3 months after operation; 47% were free of infection 6 months after operation. There have been no late deaths. Actuarial survival at 3 years is 79%. Nine patients have undergone postoperative catheterization. Resting hemodynamics were normal in every patient. All long-term survivors are asymptomatic and fully active. It is concluded that cardiac transplantation in neonates and children is an effective treatment option for end-stage cardiomyopathy or otherwise incurable congenital heart disease. Long-term survivors have excellent potential for full rehabilitation.

Actuarial Analysis↗
PubMed1991

An unusual appearance of an aneurysmal bone cyst of the thoracic spine.

Aneurysmal bone cysts (ABCs) have been reported in essentially every bone of the human skeleton. This case report documents a very unusual clinical appearance for this entity: a superior mediastinal mass. Also, the patient underwent multiple imaging studies that demonstrated both common (absence of septations) and unusual (extensive involvement of vertebral body with little involvement of posterior elements) characteristics of ABCs.

Adult↗
PubMed1991

Cavoatrial tumor thrombectomy using cardiopulmonary bypass without circulatory arrest.

Of 29 patients with inferior vena caval tumor thrombus, 14 with supradiaphragmatic extension were deemed suitable for operation. Patients (age, 7.5 to 70 years) had renal cell carcinoma (n = 8), Wilms' tumor (n = 2), transitional cell carcinoma (n = 1), and adrenal carcinoma (n = 3). Seven patients had stage III disease, and 7 patients had stage IV disease. Two patients (group A) had unresectable disease at exploratory celiotomy, 4 patients (group B) underwent tumor thrombectomy without cardiopulmonary bypass, and cardiopulmonary bypass was employed in 8 patients (group C). Three of 8 group C patients had Budd-Chiari syndrome at diagnosis. Cardiopulmonary bypass with moderate hypothermia, and inferior vena caval interruption (clip or filter), was employed in all patients. There were no perioperative deaths. Transient neurological impairment was observed postoperatively in 2 patients. Coagulopathy developed in 1 patient who had hepatic encephalopathy and Budd-Chiari syndrome preoperatively and in another patient in whom protamine could not be administered. No patient had acute renal failure requiring hemodialysis. Median survival is 41 and 17 months in groups B and C, respectively. Some authors have advocated profound hypothermia and circulatory arrest in these patients. We find that satisfactory visualization and excision can be performed with cardiopulmonary bypass and moderate hypothermia, avoiding potential renal, hepatic, neurological, and septic complications associated with circulatory arrest.

Adolescent↗
PubMed1990

Evaluating the North Carolina safety belt wearing law.

The North Carolina Seat Belt Law required an evaluation of the effectiveness of the act with a report of the findings to the Legislature three years after the law went into effect. This paper addresses changes in statewide belt usage and in occupant injury associated with that law. Observational data collected bimonthly from a probability sample of 72 sites stratified by geographic region, rural/urban location, road type, and time of day show that belt use rose from a baseline rate of 25% to a warning ticket phase rate of 45%. Belt use then reached 78% upon enforcement and is now nearly 64%. Time series analysis showed that statistically significant reductions in percentages of moderate and serious injuries occurred at the beginning of both the warning ticket and the enforcement phases. Forecasts of injuries and deaths were also developed from the time series models and were compared with observed totals. Warning tickets brought about a modest 5.4% reduction in serious injuries; fatalities among occupants covered by the law showed no change. In contrast, the subsequent enforcement phase saw a reduction of 11.6% in fatalities and 14.6% in serious or worse injuries. This represents an estimated annual savings of 131 lives and over 2,300 serious injuries in North Carolina during the 18 months following onset of enforcement.

Accidents, Traffic↗
PubMed1990

Contribution of transesophageal echocardiography to patient diagnosis and treatment: a prospective analysis.

The capability of transesophageal (TEE) versus transthoracic (TTE) echocardiography as a diagnostic tool in clinical practice was prospectively examined in 86 consecutive cases. A conclusive diagnosis was possible in 95% with TEE, whereas the same result was achieved in 48% by TTE. Specifically, TEE provided a conclusive diagnosis in 14 of 16 cases of infective endocarditis, while TTE gave this result in 4 of the 16 cases (p less than 0.001). Similarly, TEE allowed a conclusive diagnosis in 11 of 11 instances of aortic dissection, while TTE gave this indication in two cases (p less than 0.001). TEE was similarly effective in eight of eight cases of atrial thrombi, whereas TTE gave the diagnosis in three of eight cases (p less than 0.01). In five subjects with intracardiac masses, TEE gave a conclusive diagnosis in all five, whereas TTE was able to diagnose conclusively in one subject (p less than 0.02). In seven patients with mitral regurgitation, TEE gave the conclusive diagnosis in all seven and TTE was able to provide this information in four (p = NS). TEE was able to provide a conclusive diagnosis in four patients with aortic insufficiency, and TTE gave the same information in two of the four (p = NS). In 14 patients with prosthetic valve dysfunction, TEE gave the diagnosis in 12 and TTE gave it in eight patients (p = NS). Both methods gave a conclusive diagnosis in 13 out of 13 cases of mitral stenosis (p = NS). Also, TEE provided a conclusive diagnosis in eight of eight patients with adult congenital heart disease and TTE gave this information in four (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Reappraisal of localized resection for subvalvar aortic stenosis.

Between June 1972 and August 1989, we operated on 45 patients with fixed subaortic stenosis. Discrete membranous stenosis was present in 28 patients and tunnel stenosis, in 13. Four patients had subvalvar stenosis complicating double-outlet right ventricle. There were 33 male and 12 female patients. Mean age at operation was 7.1 +/- 4.3 years (range, 6 months to 21 years). Local resection of the fibrous membrane was performed in 26 patients. Local resection was combined with myectomy in 18 patients. Aortoventriculoplasty (modified Konno procedure) was required at operation in 3 patients. There were three perioperative deaths at initial operation and two deaths at the time of reoperation. Follow-up ranges from 1 month to 17 years (average follow-up, 47.0 months). Reoperation for recurrent obstruction has been required in 12 patients (27%), and 3 patients have required a second reoperation. Mild to moderate aortic regurgitation was present in 17 patients. Subaortic stenosis is a spectrum of anatomical derangements ranging from a discrete fibrous membrane to a long, tortuous fibrous tunnel with aortic annulus hypoplasia. Successful removal of a discrete fibrous membrane can be followed later by recurrent stenosis necessitating myectomy or aortoventriculoplasty. Correction of subvalvar aortic stenosis can be followed by recurrent stenosis necessitating reoperation as long as 17 years after the initial procedure.

Cardiomyopathy, Hypertrophic↗
PubMed1990

Improved dose homogeneity in electron arc therapy achieved by a multiple-energy technique.

Improved dose homogeneity throughout the treatment volume defined for electron arc therapy is achieved through superposition of multiple arcs of different electron energy to the same treatment surface. The relative weights for each arc segment and energy are determined by computer optimization which minimizes the variation in radial depth dose across the treatment volume. In addition to the standard electron beam energies of 6 MeV, 9 MeV, 12 MeV, 16 MeV and 20 MeV, a new electron arc field is created by adding bolus to the treatment surface during an additional pass using 6 MeV electrons. This modified field, having maximum dose on the patient surface and a reduced range, supplements the dose delivered by the standard electron arc fields in the buildup region. Through use of this multiple-energy technique, depending on clinical indications, electron arc therapy can be planned and delivered to allow either skin sparing or a uniform dose from the patient's surface to the desired treatment depth.

Electrons↗
PubMed1990

Design and production of customized field shaping devices for electron arc therapy.

A key element in the implementation of electron arc therapy is the use of customized field shaping devices on or near the patient's surface to protect normal tissue surrounding the treatment surface. Techniques for design and production of field shaping devices have evolved to meet the requirements of improved efficiency, patient comfort and protection, and reproducibility of patient set-up. Techniques in current use at the University of Utah are described and illustrated.

Breast Neoplasms↗