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Biomedical subjects

C R Buncher

Publications and source records attributed to C R Buncher.

At least 37 records · Page 2Linked to original sources
PubMed1992

Length of time spent in seclusion and restraint by patients at 82 VA medical centers.

Analysis of data from 82 Veterans Affairs medical centers showed that during a one-year period in 1987-88, VA psychiatric inpatients spent about 240,000 hours in seclusion or restraint, with about half of that time in mechanical restraints. The median length of time patients in each medical center spent in seclusion and restraint was used to classify centers as having "higher" or "usual" rates of use of those techniques. In the 20 centers classified as higher users, patients spent two to three times longer in seclusion and restraint per incident than patients in the 62 centers classified as usual users. Time spent by patients in seclusion and restraint in centers with usual rates of use was consistent with reports from other U.S. studies. The longer time in seclusion and restraint per incident in higher-user centers may be due to characteristics of the medical center or of the patient population.

Data Collection↗
PubMed1992

Spinal muscular atrophy: new thoughts on the pathogenesis and classification schema.

We have established the first prospective, collaborative study of spinal muscular atrophy, the second most common neuromuscular disease of childhood. One hundred and forty-one patients have been evaluated on at least four occasions over a 3-year period. The patients have been grouped by age of onset, as well as by function at the time of initial evaluation. The muscle strength of 96 patients aged 5 years or older was evaluated at 6-month intervals using a fixed myometry system. The new observations made are: (1) The present classification schema is not valid; for example, 49 patients with onset of weakness before 6 months of age (type I or Werdnig-Hoffmann disease), whose life span is said to be only 2 to 4 years, participated in the study and are 4 months to 31 years of age. (2) Thirty-seven patients were evaluated over an 18-month period. None lost strength during this time but four lost function. Although the period of observation was short, the results suggest that the loss of function in patients with spinal muscular atrophy might be explained by a process other than cell death that allows patient strength to be maintained and simultaneously prevents the motor unit from achieving its normal adult potential.

Adolescent↗
PubMed1992

Latent period for malignant mesothelioma of occupational origin.

To estimate the minimal latent period for malignant mesothelioma of occupational origin, we reviewed 21 articles that documented latent periods for malignant mesothelioma, totaling 1690 cases. Of these, 1105 (65%) cases fulfilled the strict histologic and exposure criteria and were included in this analysis. Of these mesotheliomas, 99% had a latent period more than 15 years; 96% had a latent period of at least 20 years; and the observed probability of an occupational exposure within a decade of the first exposure was zero. The estimated median latent period was at least 32 years after the initial exposure. These epidemiologic conclusions are important in determining the source of a specific case of the disease, understanding the natural history of the disease, determining liability, and in aiding in the diagnosis of malignant mesotheliomas of occupational origin.

Cause of Death↗
PubMed1991

Therapeutic responses of spontaneous canine malignancies to combinations of radiotherapy and hyperthermia.

The goals of this ongoing Phase III study of adjuvant local hyperthermia with radiotherapy were to evaluate how tumor control and normal tissue complications were related to patient and treatment variables. Canine veterinary patients with localized malignancies were stratified by histology and anatomic site and randomized into three groups. All patients received radiotherapy (60CO) in 3.5 Gy fractions given Mon-Wed-Fri to 14 treatments (49 Gy). One group received radiotherapy alone while the others also received microwave-induced hyperthermia (44 degrees C) for 30 minutes once each week. Hyperthermia followed radiotherapy and was given to one group immediately and delayed 4-5 hours in the other. Adjuvant hyperthermia resulted in a significant (p less than .05) increase in complete response rate, reduction in the frequency of non-responders, and increased persistent local control relative to radiotherapy alone. Hyperthermia increased the complete response rate regardless of histology, site, or volume and with the current sample size control was significantly (p less than .05) greater for sarcomas, tumors of the trunk and extremities, and those with volumes less than 10 cc. Quantitative clinical assessment of the acute response of skin and oral mucosa indicated that hyperthermia significantly enhanced these acute reactions, which required roughly twice the healing time observed with radiotherapy alone. Quantitative histologic scoring of changes seen between pre- and post-therapy skin biopsies indicated that a treatment induced decline in the frequency of dermal blood vessels, sebaceous glands, and hair follicles was enhanced by adjuvant hyperthermia, particularly in the late response evaluation interval. The probability of tumor control and adverse normal tissue responses correlated with several measures of thermal dose. Thermal doses in excess of 120 equivalent minutes at 43 degrees C correlated positively with increased skin reactions and negatively with the complete response rate, and these trends were usually evident during the animals' first treatment.

Animals↗
PubMed1991

Structural equation modeling in environmental risk assessment.

Environmental epidemiology requires effective models that take individual observations of environmental factors and connect them into meaningful patterns. Single-factor relationships have given way to multivariable analyses; simple additive models have been augmented by multiplicative (logistic) models. Each of these steps has produced greater enlightenment and understanding. Models that allow for factors causing outputs that can affect later outputs with putative causation working at several different time points (e.g., linkage) are not commonly used in the environmental literature. Structural equation models are a class of covariance structure models that have been used extensively in economics/business and social science but are still little used in the realm of biostatistics. Path analysis in genetic studies is one simplified form of this class of models. We have been using these models in a study of the health and development of infants who have been exposed to lead in utero and in the postnatal home environment. These models require as input the directionality of the relationship and then produce fitted models for multiple inputs causing each factor and the opportunity to have outputs serve as input variables into the next phase of the simultaneously fitted model. Some examples of these models from our research are presented to increase familiarity with this class of models. Use of these models can provide insight into the effect of changing an environmental factor when assessing risk. The usual cautions concerning believing a model, believing causation has been proven, and the assumptions that are required for each model are operative.

Environmental Exposure↗
PubMed1991

Intestinal cadmium permeability in mature and immature rats.

To compare the intrinsic permeability properties of the small intestine in adult (average body wt 300 g) and 25- to 27-day-old (average body wt 50 g) male rats, the uptake rates of cycloleucine and of cadmium were measured in intestinal segments isolated in situ with their blood supply intact. Uptake rates were expressed on the basis of that of ethanol, a solute whose absorption depends primarily on the size, rather than the composition, of the available surface area and on the presence of unstirred layers. These layers may be concluded to affect movement of cycloleucine, cadmium, and ethanol to the same extent. The ratio of uptake rates, therefore, provides in arbitrary units a measure of the intrinsic permeability of the luminal surface area to cadmium and to cycloleucine. On this basis, no developmental change in cycloleucine permeability could be detected. In contrast, the rate of cadmium uptake relative to that for ethanol decreased with age by about 50%. Possible mechanisms are discussed for this significant change in the intrinsic cadmium permeability of the jejunum in post-"closure" animals.

Aging↗
PubMed1991

Possible progress and unresolved conflicts resulting from guidelines on good epidemiologic practices.

In summary, producing guidelines also produces conflict. The purpose of this paper was to delineate some of the conflicts that result from, or are involved in, having a set of guidelines for good epidemiologic practices. The goal was to present briefly both sides of the conflicts without trying to resolve them. The hope is that others will cogently argue one side or the other of these conflicts and convince the community to resolve the conflict, or alternatively, perhaps that the current guideline is somewhere in the middle of the beliefs in the community and thus is correctly positioned.

Clinical Protocols↗
PubMed1990

Lead exposure and neurobehavioral development in later infancy.

A prospective methodology was used to assess the neurobehavioral effects of fetal and postnatal lead exposure during the first 2 years of life. Lead was measured in whole blood prenatally in mothers and at quarterly intervals in the infant. Prenatal blood lead levels were low (mean = 8.0 micrograms/dL). However, approximately 25% of the study infants had at least one serial blood lead level of 25 micrograms/dL or higher during the second year of life. Multiple regression and structural equation analyses revealed statistically significant relationships between prenatal and neonatal blood lead level and 3- and 6-month Bayley Mental and/or Psychomotor Development Index. However, by 2 years of age, no statistically significant effects of prenatal or postnatal lead exposure on neurobehavioral development could be detected. Data consistent with the hypothesis that a postnatal neurobehavioral growth catch-up occurred in infants exposed fetally to higher levels of lead are presented.

Child Behavior↗
PubMed1989

Fetal and infant lead exposure: effects on growth in stature.

The growth of a cohort of 260 infants was prospectively followed up from birth. Blood lead and stature measurements were obtained every 3 months until 15 months of age. Fetal lead exposure was indexed by measuring lead in maternal blood during pregnancy. A longitudinal analysis revealed that covariate adjusted growth rates in stature were negatively related to the infants' postnatal blood lead concentration, as indexed by increase in average blood lead values from 3 to 15 months. However, this relationship between growth rate and change in blood lead concentration was evidenced only among those infants whose mothers had prenatal blood lead levels greater than the maternal cohort median of 7.7 micrograms/dL is about 2 cm shorter at 15 months of age if, postnatally, the infant incurred a 10-micrograms/dL blood lead increase during the 3- to 15-month interval of life, compared with an infant who has no increase.

Cohort Studies↗
PubMed1988

Cardiac tamponade: a comparison of right versus left heart compression.

It has been postulated that in cardiac tamponade, the hemodynamic effects of compression of the right heart chambers and great veins are more important than are the effects of left heart compression. In 10 anesthetized dogs with surgically compartmented pericardium, the hemodynamic effects of right atrial and right ventricular compression were compared with the hemodynamic effects of left atrial and left ventricular compression. The effects of right heart compression, left heart compression, and then effects of combined right and left heart compression, were compared at three levels of intrapericardial pressure: 10, 15 and 20 mm Hg. Aortic mean pressure decreased significantly at each level of intrapericardial pressure with right-sided tamponade but not with left-sided tamponade. Left atrial mean pressures decreased significantly with right-sided tamponade and increased with left-sided and combined tamponade. Right atrial mean pressures increased significantly with right-sided and combined tamponade, but not with left-sided tamponade. Heart rate increased significantly with each of the three varieties of tamponade. Cardiac output and stroke volume, which decreased with each variety of tamponade, were significantly lower during right-sided than during left-sided tamponade. Combined tamponade lowered stroke volume more than did right-sided tamponade, and lowered cardiac output more at 15 and 20 mm Hg intrapericardial pressure. It is concluded that, in this preparation, right-sided cardiac compression has more important hemodynamic effects than does left-sided compression. However, left-sided tamponade still makes a significant contribution to the total hemodynamic picture of cardiac tamponade.

Animals↗
PubMed1988

The medical aspects of soccer injury epidemiology.

In this article, the six major studies of soccer injury epidemiology are reviewed. Strengths and weaknesses of each epidemiologic design are critiqued and the crucial importance of the definition of injury is emphasized. The effect of age, sex, and intensity of play on injury rates is discussed. Our present knowledge of injury rate by anatomical site, player position, and the type of playing surface are reviewed. We examined the importance of player factors such as flexibility, joint laxity, weakness, and incomplete rehabilitation from other injuries. In addition, we reviewed the role played by inadequate equipment, field conditions, and rule violations. A successful program for soccer injury prevention is described, and guidelines for future soccer injury epidemiology research are proposed.

Adolescent↗
PubMed1987

Pulmonary embolism and lung scanning: cost-effectiveness and benefit:risk.

The cost-effectiveness of pulmonary imaging (lung scan) on the management of 2,023 patients was studied. Prior and postscan probabilities of pulmonary embolism (PE) were obtained from referring physicians. After the scan, anticoagulant therapy (ACT) was appropriately changed in 20% of the patients and confirmed in 67%. The incremental cost of scanning was $124 per patient when the prior probability was 0.01-9.99%, dropping to $38 when the probability was 10-25%. Hospitalization and ACT cost was reduced when the prior probability was 25.01-99.99%. The greatest benefit in lives saved was when the prior probability was 25-74.99%; 1.5% of this probability group would survive as a result of the change in management attributable to the scan, at a cost of $117 per life saved. The benefit:risk ratio, as measured by lives saved compared to estimates of lives lost due to radiation exposure, was of the order of 6,000:1.

Anticoagulants↗
PubMed1985

Determination of clinical efficacy: nuclear medicine as applied to lung scanning.

This paper describes a Society of Nuclear Medicine sponsored study of 2,023 patients which compares two methods, logistic regression (LR) and entropy minimax pattern detection (EMPD), to evaluate efficacy. Lung scans, used in determining or excluding a diagnosis of pulmonary embolism (PE), were utilized to create the data set. The LR analysis, presented here, shows that lung scan findings have significant influence on the referring physician's diagnostic thinking. Models were developed for the probability of a signout diagnosis of PE, and equal patient groups tested the validity of these regression equations. Individual models developed on each patient group yielded similar results. This analysis shows that the lung scan results affect the therapeutic management of the patients in a beneficial direction. A comparison of the sensitivity, specificity, and predictive values of EMPD and LR was done. EMPD predicts a signout diagnosis on only 41% of cases before lung scan and 71% after lung scan; LR provides a prediction of the signout diagnosis on 100% of cases. An advantage of EMPD is that it does not require prior probability estimates. However, LR uses this estimate, thus incorporating intuitive knowledge not evaluated by EMPD.

Adult↗
PubMed1984

Antibody responses to toxic-shock-syndrome (TSS) toxin by patients with TSS and by healthy staphylococcal carriers.

Serum samples taken from women with toxic-shock syndrome (TSS) and from women without a history of TSS were examined for the presence of antibodies to toxic-shock-syndrome toxin (TST). Serum samples from 38 women with TSS and from 70 women with no history of TSS were analyzed by radioimmunoassay (RIA) and by an enzyme-linked immunoadsorbent assay (ELISA). Antitoxin titers obtained by the assays were highly correlated. Antibody levels in sera of women with TSS, or a history of TSS, were significantly lower than levels in sera of women with no prior evidence of TSS. The mean level of antitoxin titers in the total sample of acute, convalescent, and recovered TSS groups was significantly lower than that of the control groups, which consisted of 31 carriers of genital Staphylococcus aureus and a similar number of age- and race-matched noncarriers. Although a trend toward elevated antitoxin titers was apparent after recovery, no vigorous immunologic response to TST was noted. In contrast, the majority of healthy women demonstrated measurable antitoxin titers, a finding indicative of current or prior colonization with TST-producing strains of S. aureus. The data suggest that absence of antibodies to the TSS toxin may be a predisposing factor in the development of clinical disease.

Antitoxins↗