Biomedical subjects

W G Henderson

Publications and source records attributed to W G Henderson.

At least 19 recordsLinked to original sources

PubMed1995

A comparison of transurethral surgery with watchful waiting for moderate symptoms of benign prostatic hyperplasia. The Veterans Affairs Cooperative Study Group on Transurethral Resection of the Prostate.

BACKGROUND: Transurethral resection of the prostate is the most common surgical treatment for benign prostatic hyperplasia. We conducted a multicenter randomized trial to compare this surgery with watchful waiting in men with moderate symptoms of benign prostatic hyperplasia. METHODS: Of 800 men over the age of 54 years who were screened between July 1986 and July 1989, 556 (mean [+/- SD] age, 66 +/- 5 years) were studied (280 in the surgery group and 276 in the watchful-waiting group). Patients' symptoms and the degree to which they were bothered by urinary difficulties were measured with standardized questionnaires and medical evaluations. The primary outcome measure was treatment failure, which was defined as the occurrence of any of the following: death, repeated or intractable urinary retention, a residual urinary volume over 350 ml, the development of bladder calculus, new and persistent incontinence, a high symptom score, or a doubling of the serum creatinine concentration. Patients were followed for three years. RESULTS: Of the men randomly assigned to the surgery group, 249 underwent surgery within two weeks after the assignment. Surgery was not associated with impotence or urinary incontinence. The average follow-up period was 2.8 years. In an intention-to-treat analysis, there were 23 treatment failures in the surgery group, as compared with 47 in the watchful-waiting group (relative risk, 0.48; 95 percent confidence interval, 0.30 to 0.77). Of the men assigned to the watchful-waiting group, 65 (24 percent) underwent surgery within three years after the assignment. Surgery was associated with improvement in symptoms and in scores for urinary difficulties and interference with activities of daily living (P < 0.001 for all comparisons). The outcomes of surgery were best for the men who were most bothered by urinary symptoms at base line. CONCLUSIONS: For men with moderate symptoms of benign prostatic hyperplasia, surgery is more effective than watchful waiting in reducing the rate of treatment failure and improving genitourinary symptoms. Watchful waiting is usually a safe alternative for men who are less bothered by urinary difficulty or who wish to delay surgery.

Aged↗

PubMed1995

A twin study of the association of post-traumatic stress disorder and combat exposure with long-term socioeconomic status in Vietnam veterans.

This study examines the association between post-traumatic stress disorder (PTSD) and combat exposure with the socioeconomic status of 2210 male monozygotic veteran twin pairs in 1987. In the unadjusted analysis on individuals, modest correlations indicated that those with PTSD were more likely to have been divorced, and less likely to be currently employed or to achieve high status in income, education or occupation. In the crude analysis of veterans not suffering from PTSD, there were small positive correlations between combat level experienced and the likelihood of ever being married, ever being divorced, and the number of years employed at the current job. However, when we examined identical twins discordant for PTSD, and adjusted for pre-military and military service factors, only unemployment remained significant. Likewise, in combat-discordant twins, no significant effects on the socioeconomic indicators were seen. We conclude that PTSD and combat experience in Southeast Asia have not had a major impact on the socioeconomic status of veterans.

Adaptation, Psychological↗

PubMed1995

The Processes, Structures, and Outcomes of Care in Cardiac Surgery study protocol.

Recently, a growing interest has arisen in defining and measuring health care outcomes. Although outcome measures may be used as potential quality-of-care screens, outcomes cannot indicate directly how care might be improved. Thus, the Processes, Structures, and Outcomes of Care in Cardiac Surgery (PSOCS) study was designed to investigate the linkages between the processes and structures of care with risk-adjusted outcomes for cardiac surgery care. Data are being collected on a comprehensive array of risk factors, processes, structures, and outcomes of care at 14 Veterans Affairs Medical Centers for this prospective, observational study. Approximately 6,000 cardiac surgery patients will be enrolled in this study over a 4.5-year period. Patient selection is based on a 6 workday rotating sampling frame with an oversampling of emergent patients. During the study, a register of all patients undergoing cardiac surgery at these centers is being maintained to assess the overall context of patient recruitment. The study will continue to enroll patients through December 1996. Major study end points extend beyond traditional measures of 30-day mortality and morbidity to encompass more innovative intermediate outcome measures, including changes in physical functional status and health-related quality of life.

Aged↗

PubMed1995

Statistical methods and strategies for working with large data bases.

This article describes the statistical methods and strategies to be used in establishing the linkages between processes and structures of care with risk-adjusted outcomes in a large multicenter Veterans Affairs cooperative study in health services of patients undergoing cardiac surgery. The statistical analyses consist of test involving nine specific hypotheses related to the effect of processes and structures of care on risk-adjusted outcomes. From the statistical point of view, the major obstacles of this study are the need for data reduction and imputation of missing data. The former obstacle is addressed through the use of data-reduction techniques, such as principal components and cluster of variables. The latter is addressed through the use of classic and new techniques for imputation of missing data, such as MISSGEN, principal components for qualitative data, and the expectation and maximization algorithm. Data reduction and imputation of missing data are done with clinically derived variable groups called "dimensions" or "subdimensions." The effect of processes and structures of care is assessed by a two-step process. First, outcomes are modeled using only patient risk factors. The selection of risk factors in the modeling process is discussed in detail. Second, these risk-adjusted outcomes are modeled using one of the nine process or structure subhypotheses. The relationship of the processes and structures of care dimensions and/or subdimensions that are linked to risk-adjusted outcomes are identified.

Cardiac Surgical Procedures↗

PubMed1995

Variations in processes and structures of cardiac surgery practice.

It is hypothesized that variations in the processes and structures of the selection of patients and the conduct of the surgical procedure may influence risk-adjusted outcome in patients undergoing cardiac surgery. For this reason, the results of the pilot phase of this Veterans Affairs cooperative study were reviewed to determine the variation in the operative practices at six pilot institutions. There were large variations in the percentage of elective, urgent, and emergent cases at each institution, ranging from 58% to 96% elective, 3% to 31% urgent, and 1% to 8% emergent. There was also a tenfold increase in the preoperative use of intra-aortic balloon pump for control of unstable angina, varying from 0.8% to 10.6%. Five of the six centers had accredited thoracic surgical residency programs. There was large variation in the preoperative participation of attending surgeons, from 100% participation at three centers to less than 5% in one. The operation was performed by the attending surgeon in 28% of cases, but this varied from 0% to 100%, depending on the hospital. Cold cardioplegia was used almost uniformly (99%) for myocardial protection; the use of retrograde cardioplegia varied from 2% to 89% among hospitals, and the use of blood cardioplegia ranged from 0% to 100%, with an average of 54% of cases. The use of myocardial temperature monitoring varied between hospitals, from 25% to 99%. The use of the cell saving devices to scavenge shed blood varied from 5% to 99%, and the frequency of the use of banked blood varied from 25% to 65%, depending on the institution. The internal mammary artery was used for 67% patients undergoing coronary artery bypass graft, with a variation between hospitals of 39% to 83%. One hospital used a single cross-clamping technique for the performance of proximal anastomoses in 95% of cases, as opposed to all other hospitals, who used this technique in less than 10% of cases. Aortic venting varied from 58% to 98% and left ventricular venting from 1% to 38%. The use of porcine valves varied approximately 15% in three hospitals to 30% to 40% in the other three hospitals. There were tremendous variations in the duration of operative procedure (5.2-7.3 hours), actual operating time (4.0-5.6 hours), total cardiopulmonary bypass duration (102-146 minutes), and ischemic time (50-87 minutes). The use of inotropic support varied from 41% to 91% between hospitals.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗

PubMed1995

Evaluating anesthesia health care delivery for cardiac surgery. The role of process and structure variables.

Anesthesia care is an integral component of cardiac surgery. Emphasis on cost-effectiveness and decreased hospital stay has prompted reevaluation of anesthesia practice. However, the role of anesthesia process and structure variables in relation to patient outcomes is largely unknown. Processes, Structures and Outcomes of Care in Cardiac Surgery is the first epidemiologic study to collect data on anesthesia processes, such as the pharmacologic components of anesthesia and types of cardiovascular monitors used. Structures of care, such as resident staffing, supervision, completeness of documentation, and training and experience of care providers, are also being assessed. Pilot data collected from September 1992 to September 1993 demonstrate substantial variation between the six study sites in selected processes and structures. Despite the near-universal use of narcotic anesthesia as the primary anesthetic technique, variation in the type of opioid and adjuvant benzodiazepine used was observed. Regarding invasive hemodynamic monitoring, most centers used only one type of catheter. Intraoperative transesophageal echocardiography was used commonly at several centers for valve surgery, whereas other centers did not use it at all. Its use during coronary artery bypass grafting was less common. Assessment of the preoperative anesthesia note revealed that coronary anatomy and ventricular function were noted in nearly all instances. However, a clear notation that risks and benefits of anesthesia were discussed was less frequent. Structures related to anesthesia attending staffing, board certification, and experience revealed variation. Some sites had smaller and/or more experienced attending staffs, whereas others had larger and/or less experienced staffs. These pilot findings appear to validate the authors' hypotheses that variations in anesthesia practice are present within the Veterans Affairs system. They suggest that the variable set is robust enough to relate processes and structures of anesthesia care to patient outcome.

Anesthesiology↗

PubMed1995

Self-report measures for assessing treatment outcomes in cardiac surgery patients.

Patient self-report measures are increasingly valued as outcome variables in health services research studies. In this article, the authors describe the Functional Status, Health Related Quality of Life, Life Satisfaction, and Patient Satisfaction scales included in the Processes, Structures, and Outcomes of Cardiac Surgery (PSOCS) cooperative study underway within the Department of Veterans Affairs health care system. In addition to reporting on the baseline psychometric characteristics of these instruments, the authors compared preoperative Medical Outcomes Study SF-36 data from the study patients with survey data from a probability sample of the US population and with preoperative data on cardiac surgery patients from a high volume private sector surgical practice. Descriptive analyses indicate that the SF-36 profiles for all of the cardiac patients are highly similar. The Veterans Affairs and private sector patients report diminished physical functioning, physical role functioning, and emotional role functioning as well as reduced energy relative to an age-matched comparison sample. At the same time, however, the Veterans Affairs patients evidenced lower levels of capacity on most of the SF-36 dimensions relative to the private sector patients.

Cardiac Surgical Procedures↗

PubMed1995

An analysis of interobserver reliability and representativeness of data from the Veterans Affairs Cooperative Study on Processes, Structures, and Outcomes in Cardiac Surgery.

The authors made some preliminary judgments regarding the reliability and representativeness of the data in the early stages of the Veterans Affairs Cooperative Study entitled Processes, Structures, and Outcomes of Care in Cardiac Surgery (PSOCS). Preliminary PSOCS interobserver reliability and potential patient and site selection bias reported were based on comparisons with identical risk, procedure, and outcome data items collected independently in the Continuous Improvement in Cardiac Surgery Study. PSOCS interobserver reliability for this limited set of variables was good to excellent. At the six pilot centers, there were few important differences between patients entered into PSOCS and those not entered. The 14 Veterans Affairs medical centers that will participate in the full-scale PSOCS study and the 29 nonparticipating centers exhibited similar patient populations. will be valuable.

Cardiac Surgical Procedures↗

PubMed1995

Development of an interactive data base management system for capturing large volumes of data.

Accurate collection and successful management of data are problems common to all scientific studies. For studies in which large quantities of data are collected by means of questionnaires and/or forms, data base management becomes quite laborious and time consuming. Data base management comprises data collection, data entry, data editing, and data base maintenance. In this article, the authors describe the development of an interactive data base management (IDM) system for the collection of more than 1,400 variables from a targeted population of 6,000 patients undergoing heart surgery requiring cardiopulmonary bypass. The goals of the IDM system are to increase the accuracy and efficiency with which this large amount of data is collected and processed, to reduce research nurse work load through automation of certain administrative and clerical activities, and to improve the process for implementing a uniform study protocol, standardized forms, and definitions across sites.

Cardiac Surgical Procedures↗

PubMed1994

Mutagenicity of ethanolic extracts of used acrylic dentures.

The in vivo physicochemical sorption of mutagenic substances onto acrylic polymers was investigated in worn acrylic dentures. Thus, ethanolic extracts of acrylic dentures from 41 of a total of 69 human donors (60%), were found mutagenic in the standard plate incorporation Salmonella mutagenicity test against either TA98 or TA100 strains. Denture extracts from smokers produced mutagenicity more often than the ones from non-smokers (75% vs. 45%, P 0.01). Mutagenicity was preferentially directed against TA98 (TA98:TA100 = 2.9:1, P < 0.0005). Predilection for TA98 was more pronounced in denture extracts from non-smokers (4.7:1) than from smokers (2.0:1). When direct mutagenicity was observed, it was reduced by the rat-liver S9. Induced mutant yields were 6.1 +/- 3.9 and 7.0 +/- 8.9 times higher than the spontaneous for TA98 and TA100 respectively (smokers, 50-cm2 denture surface area eq./plate+S9). Denture extracts from smokers induced higher levels of mutation than the ones from non-smokers (TA98 + S9, smoker:non-smoker = 2:1, P < 0.01). Mutagenicity was associated with longer periods of denture usage (P 0.007). Thus, denture poly(methyl methacrylate) base material can adsorb mutagenic substances, possibly from diet and tobacco, which are extractable by ethanol. Theoretically, the in situ alcoholic desorption and recirculation of carcinogenic mutagens may have a contributory role in certain cases of intra-oral and upper alimentary tract carcinogenesis.

Acrylic Resins↗

PubMed1992

Implications of third heart sounds in patients with valvular heart disease. The Veterans Affairs Cooperative Study on Valvular Heart Disease.

BACKGROUND: The presence of third heart sounds in patients with valvular heart disease is often regarded as a sign of heart failure, but it may also depend on the type of valvular disease. METHODS: We assessed the prevalence of third heart sounds and the relation between third heart sounds and cardiac function in 1281 patients with six types of valvular heart disease. RESULTS: The prevalence of third heart sounds was higher in patients with mitral regurgitation (46 percent) or aortic regurgitation (28 percent) than in those with aortic stenosis (11 percent) or mitral stenosis (8 percent). The left ventricular ejection fraction was significantly lower (P less than 0.001) when a third heart sound was detected in patients with aortic stenosis (0.38, vs. 0.56 in those without third heart sounds) or mixed aortic valve disease (0.40 vs. 0.55). However, the ejection fraction was only slightly lower in patients with mitral regurgitation and third heart sounds (0.51 vs. 0.57, P = 0.03). The pulmonary-capillary wedge pressure was higher (P less than 0.001) when a third heart sound was detected in patients with aortic stenosis (18.6 mm Hg, vs. 12.1 mm Hg in those without third heart sounds). There was no association between the wedge pressure and third heart sounds in patients with mitral regurgitation. The prevalence of third heart sounds increased with the severity of mitral regurgitation. CONCLUSIONS: In patients with mitral regurgitation, third heart sounds are common but do not necessarily reflect left ventricular systolic dysfunction or increased filling pressure. In patients with aortic stenosis, third heart sounds are uncommon but usually indicate the presence of systolic dysfunction and elevated filling pressure.

Adult↗

PubMed1992

Elementary methods for the analysis of dichotomous outcomes in unselected samples of twins.

This paper presents an elementary statistical method for analyzing dichotomous outcomes in unselected samples of twin pairs using stratified estimators of the odds ratio. The methodology begins by first randomly designating one member of each twin pair as an "index" twin and the other member as the "co-twin." Stratifying on zygosity, odds ratios are used to measure the association between disease in the index twin and disease in the co-twin. From these zygosity-specific tables we calculate the Woolf-Haldane estimator of the common odds ratio (psi F, the weighted average of the zygosity-specific odds ratios), the Mantel-Haenszel test statistic (chi 2M-H) for the common odds ratio, and a test (chi 2G) for the difference in the zygosity-specific odds ratios. In this application, psi F provides an estimate of the familial association for disease and the accompanying chi 2M-H provides a test of the null hypothesis, psi F = 1 (i.e., there is no evidence for a familial influence on disease). The chi 2G is a test of the null hypothesis that psi MZ = psi DZ; a significant value for chi 2G suggests a genetic influence on disease (assuming that the observed odds ratios follow a pattern where psi MZ greater than psi DZ). A new test statistic (chi 2c) is proposed that incorporates the expectation that psi MZ = psi 2DZ under a purely additive genetic model with no common environmental effects. A significant value of chi c2 indicates that the different odds ratios across zygosity are partly due to common environmental influences. Conversely, a nonsignificant value of chi 2c is an indication that the zygosity-specific odds ratios are due solely to additive genetic effects and not to common environment. This basic approach is extended to examine the effects of measured indicators of the specific environment and the assessment of certain forms of gene by environment interaction. All of the methods are easily understood, highly flexible, readily computed using a hand calculator, and incorporate the inherent genetic information contained within twin samples.

Data Interpretation, Statistical↗

PubMed1992

Health effects of military service. Lessons learned from the Vietnam experience.

This article examines the methodologic difficulties encountered in studies of the long-term effects of the Vietnam War on the psychological and physical health of veterans. Alternate study designs and exposure and outcome measurements are examined in relation to psychological (post-traumatic stress disorder and alcohol use or abuse) and physical (mortality and birth defects in children) health outcomes. All major epidemiologic studies of post-traumatic stress disorder and alcohol use or abuse utilize cross-sectional research designs. Mortality and birth defect studies use cohort, case-control, or proportionate mortality strategies. Exposure is measured using either definitive dichotomous indicators of service in Southeast Asia or more complex indicators of the Vietnam experience (i.e., combat, herbicide exposure, atrocities, abusive violence) that are of suspect validity. In studies of psychological health, outcomes are based exclusively on self-reported symptoms, while investigations of mortality and birth defects use death certificates and hospital records. Epidemiologic research on the effects of the Vietnam conflict has been hampered by problems in research design and the inherent difficulties of measuring wartime exposures and long-term health outcomes.

Alcoholism↗

PubMed1992

Influence of age, performance status, body weight, and tumor type in individuals with cancer on the disposition of warfarin and its enantiomers: Department of Veterans Affairs cooperative study number 75.

Plasma warfarin and its R,S enantiomer concentrations, one-stage prothrombin times, and mean daily warfarin doses were analyzed in 196 patients given warfarin. These individuals were part of a controlled clinical trial that examined the effect of warfarin as an adjuvant to "standard" treatment in a variety of malignancies. Neither the plasma warfarin concentration nor the daily warfarin dose required to produce a given degree of prothrombin-time prolongation was influenced by age or body weight in these subjects. When the data were analyzed by performance status, we noted several variations of interest. Individuals with different tumor types demonstrated disparities in warfarin disposition. Patients with colorectal cancer, for example, required lower mean daily warfarin doses to achieve a given degree of one-stage prothrombin time prolongation. Analysis of warfarin enantiomers (R,S) in a selected group of patients demonstrated a lower-than-normal ratio (2:1) for the colorectal cancer group (1.42:1) because of an apparent decrease in the plasma R component. In contrast, patients with head and neck cancer demonstrated a ratio of 2.85:1, and the R component was elevated. Warfarin disposition and the effect of warfarin on vitamin K-dependent clotting factor production were altered in the patients with cancer reported in this study. The mechanisms for these alterations are complex and not completely understood.

Aging↗

PubMed1991

A co-twin control study of the effects of the Vietnam War on the self-reported physical health of veterans.

This study examines the impact of military service on 13 categories of self-reported physical health problems by using a sample of 2,260 American male-male monozygotic twin pairs who served on active duty during the Vietnam War. Data were collected in 1987 by using mail and/or telephone interviews. Twins who served in Southeast Asia reported an increased prevalence of currently having hearing problems (odds ratio (OR) = 1.9, 95% confidence interval (Cl) 1.3-2.7) and persistent skin conditions (OR = 2.1, 95% Cl 1.4-3.2). Odds ratios for these health problems increased with increasing combat exposure and could not be explained by confounding due to posttraumatic stress disorder or demographic or military service factors. Significantly increased odds ratios were also demonstrated for ever having hearing problems (OR = 1.8, 95% Cl 1.3-2.5), ever having persistent skin conditions (OR = 2.1, 95% Cl 1.5-3.0), and having been hospitalized for stomach conditions (OR = 2.6, 95% Cl 1.4-4.9). Marginally increased odds ratios were demonstrated for ever having stomach conditions (OR = 1.4, 95% Cl 1.0-1.9) and urinary conditions (OR = 1.5, 95% Cl 1.0-2.1). Service in Southeast Asia was not associated with any of the remaining categories of physical health problems. Thus, although the past health of veterans who served in Southeast Asia may have been somewhat worse than that of their siblings who did not serve in southeast Asia, no major differences in current health are detected.

Adult↗

PubMed1991

Conditional power for arbitrary survival curves to decide whether to extend a clinical trial.

This article describes a computer simulation methodology to calculate conditional power for comparing two arbitrary survival curves as an aid in deciding whether or not to extend a clinical trial. The method is a modification of that by Halpern and Brown, which computes unconditional power for comparing arbitrary survival curves at the beginning of a study. The advantage of this method is that it permits conditional power calculations for comparisons of distribution-free survival curves. Power is computed for two commonly used statistical tests, the log-rank test and Gehan's generalization of the Wilcoxon test, and for a modified Kolmogorov-Smirnov test, which is particularly sensitive to crossing survival curves. This method for estimating conditional power should be useful in the situation in which a decision must be made regarding the benefit of continuing a clinical trial. The application of this method is shown using VA Cooperative Study No. 90, "Prognosis and Outcome Following Heart Valve Replacement."

Aortic Valve↗

PubMed1990

A twin study of the effects of the Vietnam War on posttraumatic stress disorder.

This study evaluates the impact of military service during the Vietnam era (1965 to 1975) on posttraumatic stress disorder using a sample of 2092 male-male, monozygotic, veteran twin pairs. Data were collected in 1987 using mail and telephone interviews. In 715 monozygotic twin pairs who were discordant for military service in southeast Asia (SEA), posttraumatic stress disorder was found to be strongly associated with military service in SEA. The prevalence of posttraumatic stress disorder was 16.8% in twins who served in SEA compared with 5.0% in co-twins who did not serve in SEA. There was a ninefold increase in the prevalence of posttraumatic stress disorder (95% confidence interval, 4.8 to 17.6), comparing twins who experienced high levels of combat with their co-twin who did not serve in SEA. Our results demonstrate that nearly 15 years following the end of the Vietnam War, there remains a substantially increased prevalence of posttraumatic stress disorder among veterans who served in SEA.

Adult↗

PubMed1990

Use of principal components analysis to develop a composite score as a primary outcome variable in a clinical trial. The VA Cooperative Study Group on Cochlear Implantation.

This article describes the use of principal components analysis to derive a composite score from a battery of 24 audiologic tests. The composite score is being used as the primary outcome variable in a clinical trial comparing the efficacy of three cochlear implant devices for people with bilateral, profound hearing loss. The first principal component from the within-class pooled variance-covariance matrix over four time periods was chosen to establish the coefficients for the composite score. This component accounted for 61% of the total variance of the 24 audiologic tests. The first principal component had its largest coefficients associated with the most difficult audiologic tests. The mean composite score of all patients improved over time; some patients showed dramatic improvement. The changes in the composite score over time were also closely related to subjective impressions of implant performance by the patient, audiologist, and otolaryngologist.

Analysis of Variance↗