Biomedical subjects

H Wasserman

Publications and source records attributed to H Wasserman.

7 recordsLinked to original sources

PubMed2000

QueryCat: automatic categorization of MEDLINE queries.

A searcher's inability to formulate an appropriate query can result in an overwhelming number of retrieved documents. Our approach to this problem is to use information about common types or categories of queries to (1) reformulate the user's initial query and (2) create an informative organization of the retrieved documents from the reformulated query. To achieve these goals, we first must identify which common categories or types of queries are the best abstraction of the user's specific query. In this paper, we describe a system that performs this first step of categorizing the user's query. Our system uses a two-phased approach: a lexical analysis phase, and a semantic analysis phase. An evaluation of our system demonstrates that its query categorization corresponds reasonably well to the query categorizations by medical librarians and physicians.

Algorithms↗

PubMed1998

Cost-effectiveness of coronary artery bypass surgery in octogenarians.

OBJECTIVE: The objective of this retrospective cohort study was to determine whether coronary artery bypass graft (CABG) surgery is effective and cost-effective relative to medical management of coronary artery disease (CAD) in the elderly. SUMMARY BACKGROUND DATA: The aging of the U.S population and the improvements in surgical techniques have resulted in increasing numbers of elderly patients who undergo this surgery. The three randomized, controlled trials (RCTs) that established the efficacy of CABG surgery completed patient enrollment from 19 to 24 years ago excluded patients older than 65 years. Although information regarding outcomes of CABG in this population is mainly available in case series, a major lacuna exists with respect to information on quality of life and cost effectiveness of surgery as compared with medical management. METHODS: The authors retrospectively formed surgical and medically managed cohorts of octogenarians with significant multivessel CAD. More than 600 medical records of patients older than 80 years who underwent angiography at our institution were reviewed to identify 48 patients who were considered reasonable surgical candidates but had not undergone surgery. This cohort was compared with 176 patients who underwent surgery. RESULTS: The cost per quality-adjusted life year saved was $10,424. At 3 years, survival in the surgical group was 80% as compared with 64% in the entire medical cohort and 50% in a smaller subset of the medical cohort. Quality of life in patients who underwent surgery was measurably better than that of the medical cohort with utility index scores, as measured by the EuroQoL, (a seven-item quality of life questionnaire) of 0.84, 0.61, and 0.74, respectively. CONCLUSIONS: Performing CABG surgery in octogenarians is highly cost-effective. The quality of life of the elderly who elect to undergo CABG surgery is greater than that of their cohorts and equal to that of an average 55-year-old person in the general population.

Age Factors↗

PubMed1995

Current spectrum of cardiogenic shock and effect of early revascularization on mortality. Results of an International Registry. SHOCK Registry Investigators.

BACKGROUND: Cardiogenic shock remains the leading cause of death of patients hospitalized with acute myocardial infarction (MI). This study was conducted to examine (1) the current spectrum of cardiogenic shock, (2) the proportion of patients who are potential candidates for a trial of early revascularization, and (3) the apparent impact of early revascularization on mortality. METHODS AND RESULTS: Nineteen participating centers in the United States and Belgium prospectively registered all patients diagnosed with cardiogenic shock. Two hundred fifty-one patients were registered. The mean age was 67.5 +/- 11.7 years, and 43% were women. Acute mitral regurgitation or ventricular septal rupture was the cause of shock in 8%. Concurrent conditions contributing to the development of shock were noted in 5%, and 2% had isolated right ventricular shock. Among the remaining 214 patients, nonspecific findings on the ECG associated with "nontransmural" MI were seen in 14%. The median time to shock diagnosis after MI was 8 hours. The overall in-hospital mortality was 66%. Patients clinically selected to undergo cardiac catheterization were significantly younger and had a lower mortality than those not selected (51% versus 85%, P < .0001) even if they were not revascularized (58%). Mortality for patients undergoing percutaneous transluminal coronary angioplasty (PTCA) was 60% (n = 55) and 19% (n = 16) for coronary artery bypass graft surgery (CABG). Sixty percent (n = 150) of registered patients were judged eligible for a trial of early revascularization. Trial-eligible patients were significantly younger (65.4 +/- 11.0 versus 70.6 +/- 11.9 years, P < .001), had an earlier median time to shock onset after MI (6.5 versus 17.5 hours, P = .003), and had lower mortality (62% versus 73%, P = .077) than ineligible patients. CONCLUSIONS: Patients diagnosed with cardiogenic shock complicating acute MI are a heterogeneous group. Those eligible for a trial of early revascularization tended to have lower mortality. Patients selected to undergo cardiac catheterization had lower mortality whether or not they were revascularized. Emergent PTCA and CABG are promising treatment modalities for cardiogenic shock, but biased case selection for treatment may confound the data. Whether PTCA and CABG reduce mortality and which patient subgroups benefit most remain to be determined in a randomized clinical trial.

Aged↗

PubMed1994

The excretion of radiopharmaceuticals in human breast milk: additional data and dosimetry.

The amount of radioactivity excreted in breast milk following administration of 11 different radiopharmaceuticals, including technetium-99m labelled microspheres, pyrophosphate, diisopropyl-iminodiacetic acid (DISIDA) and sestamibi, has been measured. This report summarises the data collected from 60 patients. An effective decay constant for the series of samples from each patient was calculated from exponential curves fitted by least squares to the data. It is difficult to compare values from individual patients, since times of expression, volumes of milk and the activity administered are not uniform. In order to formulate reliable guidelines, we therefore calculated the total activity theoretically excreted in milk until complete decay of the radionuclide, which is usually higher than that actually measured over the actual period of collection. Of the various 99mTc compounds, pertechnetate clearly reaches the highest concentrations in breast milk. The wide variability of data from different patients who received the same radiopharmaceutical despite identical methods of sample collection and data processing confirms the impression gained from literature that transfer of radionuclides into milk varies greatly between individuals. Although we have calculated average values for each compound, very large standard deviations were obtained, and we believe that for radiation protection purposes, a "worst case" approach is the most appropriate. With new data available and the revision of ICRP recommendations, the guidelines applicable when radiopharmaceuticals are administered to breast-feeding mothers are reviewed. The effective dose resulting from close contact between patient and infant was included in these calculations. Breast feeding need not be interrupted after administration of 99mTc-DISIDA, -sulphur colloid, -gluconate and -methoxyisobutylisonitrile (MIBI). However, after administration of 99mTc-MIBI, close contact should be restricted. 99mTc-pyrophosphate and -microspheres require interruption periods of several hours. High activities of 99mTc-pertechnetate may require interruption longer than 2 days. For pertechnetate and 99mTc-labelled red blood cells, interruption of breast feeding with measurement of activity in expressed milk samples is recommended. Breast feeding is contra-indicated after administration of 67Ga and 131I. General guidelines regarding breast feeding after administration of radiopharmaceuticals are summarised.

Female↗

PubMed1988

Air kerma rate constants for radionuclides.

Conversion to SI units requires that the exposure rate constant which was usually quoted in R.h-1.mCi-1.cm2 be replaced by the air kerma rate constant with units m2.Gy.Bq-1.s-1. The conversion factor is derived and air kerma rate constants for 30 radionuclides used in nuclear medicine and brachytherapy are listed. A table for calculation of air kerma rates for other radionuclides is also given. To calculate absorbed dose to tissue, the air kerma rate has to be multiplied by approximately 1.1. A dose equivalent rate constant is thus listed which allows direct calculation of dose equivalent rate to soft tissue without resorting to exposure rate constants tabulated in the special units R.m2.mCi-1.h-1 which should no longer be used.

Air↗

PubMed1984

Determination of the partition coefficient of 133xenon between oral tissues and blood in the dog.

Ostwald solubility coefficients for 133Xe in plasma (Sp), red blood cells (Sc), and selected oral tissue homogenates (St) obtained from the dog were determined at 4, 20, 27 and 37 degrees C by counting the 133Xe activity of the air phase and the sample (liquid, red cells or tissue) in the same tube following equilibration. The partition coefficient for xenon (lambda, in ml/g) between red cells and plasma (lambda cp) and that between tissues and plasma (lambda tp) were calculated from the measured Sp, Sc and St. The tissue-blood partition coefficients (lambda tb) of oral tissues for 133Xe were then calculated using lambda cp, lambda tp and the haematocrit value. The calculated values of lambda tb at 37 degrees C and 50 per cent haematocrit were 0.650 for the pulp, 0.674 for the tongue, 0.828 for the submandibular gland and 0.881 for the gingiva of the dog. lambda cp increased and lambda tp decreased as the temperature was reduced from 37 to 4 degrees C.

Animals↗

PubMed1980

Clinical trial of plasma exchange with a membrane filter in treatment of crescentic glomerulonephritis.

Four patients with rapidly progressive crescentic glomerulonephritis were treated with repeated plasma exchanges, using a disposable plasma filter (PLASMAFLO), combined with immunosuppression and anticoagulation. A definite improvement of renal function was observed in two patients and complete recovery of the severe lung changes of Goodpasture's syndrome was seen in one of them. In another patient rapid progression of renal insufficiency was arrested. One patient with anuria at the start of treatment remained anuric. The filter was capable of removing as large a molecule as IgM, and the plasma concentrations of immunoglobulins and complement factors declined successively after each treatment. Plasma exchange with the filter technique is readily accessible and safe in hands of the hemodialysis staff. Easy availability and simplicity are important advantages over the centrifuge methods, considering that prompt commencement of the treatment is a key issue in success.

Adolescent↗