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Biomedical subjects

M A Hamilton

Publications and source records attributed to M A Hamilton.

At least 73 records · Page 4Linked to original sources
PubMed1991

Ischemic cardiomyopathy. Criteria for coronary revascularization and cardiac transplantation.

Because of the shortage of donor hearts, 16 (33%) of 48 patients with ischemic cardiomyopathy died awaiting transplantation. Determining factors that predict effective coronary revascularization and identifying patients who may benefit from revascularization is crucial. From 1984 to 1990, 207 ischemic cardiomyopathy patients were evaluated for heart transplantation; 131 were accepted (83 transplanted), 54 were not accepted, and 22 were revascularized (19 underwent bypass graft surgery and three underwent percutaneous transluminal coronary angioplasty). Four bypass patients failed early (less than or equal to 30 days, three deaths and one urgent heart transplant) and two late deaths (greater than or equal to 1 year) occurred. Overall mortality was 27%. Three-year survival of revascularized and transplanted patients was 72 +/- 10% and 73 +/- 6%, respectively. Successfully revascularized patients had preoperative ejection fraction, left ventricular end-diastolic dimension, and New York Heart Association functional class of 26 +/- 9%, 68 +/- 3 mm, and 3.9 +/- 0.4, respectively, compared with 36 +/- 9% (p less than 0.05), 64 +/- 6 mm (p = NS), and 1.2 +/- 0.4 (p less than 0.05) after revascularization. Preoperative ejection fraction of patients failing revascularization was 15 +/- 4% (p = NS compared with successful revascularization), and left ventricular end-diastolic dimension was 81 +/- 4 mm (p less than 0.05). Preoperative positron emission tomography imaging myocardial blood flow and glucose metabolism was performed in 12 patients: 10 patients with scans predicting reversible ischemia were successfully revascularized, and two patients with negative scans had failed revascularization.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1990

Acute reduction of atrial overload during vasodilator and diuretic therapy in advanced congestive heart failure.

Although acute afterload reduction is known to improve cardiac output in patients with congestive heart failure (CHF), the effect of therapy on the atrial overload directly causing congestive symptoms has not been systematically studied. Atrial volumes and mitral and tricuspid regurgitation, in addition to left ventricular ejection fraction and indexes of left ventricular contractility (mean acceleration, ejection time and peak systolic pressure/end-systolic volume index), were measured using 2-dimensional and Doppler echocardiography and color flow imaging in 30 patients with advanced CHF, before and after acute vasodilator and diuretic therapy tailored to hemodynamic goals. Therapy increased stroke volume by 64% (36 +/- 10 to 55 +/- 14 cc), decreased right atrial pressure by 45% (15 +/- 5 to 8 +/- 4 mm Hg), systemic vascular resistance by 36% (1,700 +/- 400 to 1,030 +/- 300 dynes s cm-5) and pulmonary capillary wedge pressure by 37% (31 +/- 6 to 19 +/- 6 mm Hg) (all p less than 0.001). Echocardiography showed simultaneous reductions in left and right atrial volumes: 24 +/- 19 and 18 +/- 12%, respectively (p less than 0.001). Mitral and tricuspid regurgitation measured by color flow fraction both decreased by a mean of 44% (p less than 0.001). While ejection fraction increased from 15 +/- 5 to 19 +/- 7% (p less than 0.001), there were no changes in relatively load-independent indexes of contractility. Therefore, acute therapy with vasodilators and diuretics in advanced CHF causes reductions in atrial volumes and atrioventricular valve regurgitation that are evident from serial noninvasive studies and may play a major role in the improvement of congestive symptoms.

Adolescent↗
PubMed1990

Dentists' technical competence, communication, and personality as predictors of dental patient anxiety.

Previous research has found that many factors influence patients' dental anxiety, many of which are related to the practitioner's technical and interpersonal skill. Unfortunately, a confirmatory factor analysis of scales used in dental anxiety research revealed numerous problems with the measurement devices. The Spielberger State-Trait Anxiety Inventory (STAI) split into two subscales: calmness and anxiety. The Corah Dental Anxiety Scale (CDAS) was unidimensional but was unable to detect relationships between anxiety and interpersonal or communication factors. Interestingly, patient satisfaction, dentist behavior, and empathy items did not load on independent scales, as previously reported in the literature. Instead, five clusters were detected: positive and negative communication, positive and negative interpersonalness, and perceived technical competence.

Anxiety↗
PubMed1990

Altered thyroid hormone metabolism in advanced heart failure.

To determine the prevalence and significance of abnormal thyroid hormone metabolism in congestive heart failure, free thyroxine (T4) index, free triiodothyronine (T3) index, reverse T3 and thyrotropin levels were obtained in 84 hospitalized patients with chronic advanced heart failure. Free T4 index was normal in all patients. Free T3 index was reduced or reverse T3 elevated, or both, leading to a low free T3 index/reverse T3 ratio in 49 (58%) of the 84 patients. A low free T3 index/reverse T3 ratio was associated with higher right atrial, pulmonary artery and pulmonary capillary wedge pressures and lower ejection fraction, cardiac index, serum sodium, albumin and total lymphocyte count. In multivariate analysis, the free T3 index/reverse T3 ratio was the only independent predictor of poor 6 week outcome (p less than 0.001); the actuarial 1 year survival rate was 100% for patients with a normal ratio and only 37% for those with a low ratio (p less than 0.0001). A low free T3 index/reverse T3 ratio is associated with poor ventricular function and nutritional status and is the strongest predictor yet identified for short-term outcome in patients with advanced heart failure.

Adolescent↗
PubMed1990

Cardiac transplantation: the UCLA experience 1984 to 1990.

The international experience has documented the therapeutic value of cardiac transplantation in the management of carefully selected patients with endstage heart disease. The UCLA program's experience over the years 1984 to 1990 mirrors these results, establishing heart transplantation as an accepted form of therapy that offers extended survival and improved quality of life compared to alternative means of treatment. Criteria of eligibility for recipient candidates have become less restrictive, most notably the expansion of age limits to include increasingly older patients. Seventy-three patients over 55 years of age underwent heart transplantation in this series, with actuarial survival results comparable to that achieved in adult patients 55 years of age and under (68.5% vs 74.7% at 4 years, respectively). Twenty-one children between the ages of 7 months and 17 years have undergone cardiac transplantation at UCLA with survival results comparable to that of our adult population (74.3% vs 76.5% actuarial survival at 3 years, respectively). Continued efforts aimed at the development of improved means of immunosuppression as well as better methods for the detection of rejection are needed if these results are to be significantly improved.

Adult↗
PubMed1988

Descriptive statistical analyses of serial dilution data.

The serial dilution assay (for example, an in vitro antimicrobic susceptibility test or a serum antibody titer assay) is an important technique in biomedical research. The structure of the experiment forces grouping of the threshold concentrations into intervals. Statistical methods to analyse threshold concentrations from a batch of serial dilution assays should account for the grouping of the data. Many traditional subject area analyses, however, ignore the grouped nature of the data. This article discusses the discrepancy between the traditional subject area approach and the usual statistical approach for analysing such grouped data.

Antibodies↗
PubMed1988

Estimating the power of the two-sample Wilcoxon test for location shift.

Traditional methods for calculating the power of a statistical test for location shift require knowledge of the shape of the underlying probability distribution. The distribution shape, however, may be unknown. This paper describes a bootstrap method for using observed data (or pilot data) to approximate the power. No assumptions need be made about the shape of the underlying continuous probability distribution. Simulation evidence shows that, when applied to the Wilcoxon two-sample test for location shift, the suggested method is reliable. The evidence also shows that it is more accurate than a benchmark traditional approach. The bootstrap method is applied to a real-data example. The analysis demonstrates how the method can be used to determine sample sizes and how to choose the more powerful of two alternative tests for location shift.

Animals↗
PubMed1984

The health status of fourth form students in Northland.

A random sample of fourth form students throughout Northland was studied. Uncorrected visual defects were found in 4.5% and significant hearing loss in 9.1%. Appreciable numbers were overweight; 6.2% of boys and 22.5% of girls exceeded the desirable bulk index range. Levels of total cholesterol appear decreased compared to earlier New Zealand studies and were significantly lower than the Wairoa College survey levels. There was a strong correlation between total cholesterol and low density lipoprotein cholesterol. High density lipoprotein cholesterol was significantly higher in non-Maori than in Maori girls. Overall systolic blood pressure for boys at 114.3 mmHg (15.2 kPa) was significantly higher than for girls at 109.5 mm Hg (14.56 kPa). One-third of boys exceeded the adult uric acid reference range; a significantly higher proportion than for girls. Fifteen point one percent of boys and 23.5% of girls reported smoking seven or more cigarettes per week; 19.1% of boys and 9% of girls reported taking regular amounts of alcohol at least every weekend.

Adolescent↗
PubMed1984

Prospective payment's impact on ancillary services. Pastoral care, social services: role in reducing medical costs.

Under the prospective payment system, costs for medical social services, as well as for other inpatient services, are reimbursed at a fixed rate according to the patient's diagnosis. Thus hospitals, under the incentives to reduce costs by limiting services and increasing patient volume, will examine ancillary services to determine whether the services increase or decrease costs. Social and pastoral care workers will likely play an important role in hospitals' cost reduction efforts in several ways: Begin forming a discharge plan early in a patient's care, especially for patients who are at high risk for delayed discharge. Evaluate patients and their families to detect problems that may impede treatment and recovery and refer patients to community and hospital resources for help. In the emergency room, guide persons who do not need to be hospitalized to community resources. Record patient information that may help health professionals improve treatment and speed discharge. Such data include patients' financial status, use of community agencies, and rehabilitation. Counsel patients and families as they make treatment decisions.

Ancillary Services, Hospital↗
PubMed1984

Interval estimation of the density of organisms using a serial-dilution experiment.

The serial-dilution assay is a standard microbiological method for estimating the density of organisms in a solution. The commonly used interval-estimation procedures of Woodward and deMan are described and compared. A new method for the calculation of two-sided confidence intervals, which is superior to the standard procedures, is presented. The computations are illustrated for a decimal dilution assay with three samples at each of three dilutions.

Biometry↗
PubMed1983

Estimating proportionate changes in rates.

Quantitative measures are defined for use in health policy formulation. Consider a dichotomized risk factor for a specific disease or a protective factor known to promote health. A health policy that alters the prevalence of exposure to the factor will create corresponding proportionate changes in the disease rate and in the health rate. Statistical formulas are presented for estimating such proportionate changes. Formulas are given for cohort, case-control, and some hybrid study designs, but only for those studies where it is appropriate to present the data in a 2 X 2 table. It is assumed that the population is stable and that all subjects are observed over the same fixed time interval. Formulas for estimating the standard error of the estimate are also provided.

Craniocerebral Trauma↗
PubMed1981

Effect of neonatal intrahypothalamic testosterone implants on cyclicity and adult sexual behavior in the female hamster.

To localize the neural sites of hormone action for sexual differentiation in the hamster, pellets containing 3 microgram testosterone were implanted directly in the preoptic area-anterior hypothalamus (POA-AH) and the ventromedial hypothalamus-arcuate regions of the hypothalamus of 3-day-old female hamsters. The POA-AH implants strongly enhanced the potential for ectopic mounts, rear mounts, and intromission patterns after adult testosterone treatment. 50% of the females with neonatal POA-AH implants demonstrated vaginal acyclicity in adulthood, suggesting a significant disruption of normal gonadotropin release. Tests for female sexual behavior revealed that implants in both POA-AH and ventromedial arcuate had no significant effect on latency to lordosis or total lordosis duration with estrogen and progesterone priming, but did reduce the longest single bout of lordosis. In conjunction with other recent investigations, these findings suggest that in the hamster, as in other species, androgenization involves several independent processes in terms of both location and sensitivity to hormone exposure.

Animals↗
PubMed1980

Aural health in 227 Northland school and preschool children.

Two hundred and seventy-seven Northland school and preschool children were examined to determine the current incidence of chronic suppurative otitis media and middle ear effusion in the child population of one area. A reduction in incidence of CSOM from 10.5 percent in 1974 to 2.7 percent in 1978 is attributed to the successful mobile ear clinic's child health hearing conservation programme. The incidence of middle ear effusion would indicate that this condition may be less uncommon in Maori children than is generally believed. The value of impedance audiometry as a screening procedure is considered.

Acoustic Impedance Tests↗
PubMed1979

Statistical tests for recessive lethal-carriers.

This paper presents a statistical method for testing whether a male mouse is a recessive lethal-carrier. The analysis is based on a back-cross experiment in which the male mouse is mated with some of his daughters. The numbers of total implantations and intrauterine deaths in each litter are recorded. It is assumed that, conditional on the number of total implantations, the number of intrauterine deaths follows a binomial distribution. Using computer-simulated experimentation it is shown that the proposed statistical method, which is sensitive to the pattern of intrauterine death rates, is more powerful than a test based only on the total number of implant deaths. The proposed test requires relatively simple calculations and can be used for a wide range of values of total implantations and background implant mortality rates. For computer-simulated experiments, there was no practical difference between the empirical error rate and the nominal error rate.

Animals↗
PubMed1979

Choosing the parameter for a 2 x 2 table or a 2 x 2 x 2 table analysis.

Fourteen 2 x 2 table measures of association are compared and six 2 x 2 x 2 table measures of synergism are compared. The presentation is based on a conceptual population model for the true association between the disease and the risk factor(s). Each measure is judged as to potential use and identified with the study designs under which it can be estimated. It is shown that prior information about the correct population model is required to adequately measure synergism.

Abnormalities, Drug-Induced↗