PubMed Health⌕ Search

Biomedical subjects

D K Walker

Publications and source records attributed to D K Walker.

At least 37 records · Page 2Linked to original sources

Monitoring and evaluating managed care for children with chronic illnesses and disabilities.

OBJECTIVE: Children with chronic illnesses and disabilities are increasingly enrolling in managed care arrangements. Yet, the rapid expansion of managed care has unknown consequences for children with chronic conditions and disabilities. As managed care is likely to become the predominant mode of medical practice for children with chronic health problems, information gained from a thorough assessment of existing managed care models could be helpful in indicating adjustments and modifications that could result in improved outcomes for this population. the purpose of this article is to outline a new strategy for collecting needed information on the effects of managed care on children with chronic health problems. METHODS: We reviewed the literature on the effects of managed care on children with chronic conditions and disabilities. We identified key domains relevant to monitoring and evaluating managed care for this population. RESULTS: Two research approaches can provide helpful information for assessing the effects of managed care on children with chronic conditions. First, a monitoring strategy could be pursued in which enrollment trends in managed care, enrollee perceptions of access and satisfaction with care, and other general indicators of outcomes would be tracked over time using inexpensive and rapid turnaround data sources. Second, an evaluative strategy could be pursued using experimental or quasiexperimental designs, in which outcomes across a variety of domains for children with chronic conditions in managed care are compared with: (a) outcomes for the same children before enrollment in managed care; or (b) outcomes for similar children remaining in traditional fee-for-service settings. Evaluation and monitoring strategies should focus on outcomes in a number of domains including: (1) access to care; (2) utilization of services; (3) quality of care; (4) satisfaction with care; (5) expenditures for care; (6) health outcomes; and (7) family impact. CONCLUSION: Assessing outcomes that result from enrollment in managed care for children with chronic health problems presents a formidable challenge. The research strategy outlined in this article presents one approach to meeting that challenge. The monitoring and evaluation strategies described here would require commitment of additional resources on the part of government, private foundations, and/or health plans. Given the paucity of existing information and the stakes for children with chronic conditions and their families, investment of added resources in a comprehensive monitoring and evaluation strategy is essential.

Child↗

Comparison of the disposition of two novel combined thromboxane synthase inhibitors/thromboxane A2 receptor antagonists in the isolated perfused rat liver.

1. The pharmacokinetics of two combined thromboxane synthase inhibitor/thromboxane A2 receptor antagonists were investigated in an isolated perfused rat liver preparation. 2. The clearance of both UK 101613 (15.4 +/- 1.9 ml/min) and UK 102333 (14.9 +/- 1.6 ml/min) was limited by hepatic bloodflow. Both hepatic uptake and biliary excretion of UK 101613 appeared to be active processes. The apparent biliary clearance of UK 101613 (10.3 +/- 2.3 ml/min) was less than perfusate clearance, indicating accumulation within the hepatocytes. 3. The efficiency of the active hepatic uptake of UK 101613 and UK 102333 explains the rapid removal of these compounds from the systemic circulation. The processes of biliary and/or metabolic clearance of UK 101613 and UK 102333 appear to be subsequent to and independent of perfusate clearance. 4. Although the compounds are of similar structure and have a similar hepatic extraction (> 0.9), UK 101613 had an apparent biliary clearance approximately twice that of UK 102333. This is due to the formation of a metabolite of UK 102333 which reduces the amount of parent compound available for biliary excretion. 5. Inhibition of this latter metabolism by ketoconazole (10 microM) resulted in the two compounds having comparable apparent biliary clearances.

Animals↗

Importance of metabolic stability and hepatic distribution to the pharmacokinetic profile of amlodipine.

1. In an isolated perfused rat liver (IPRL) model, the extensive hepatic uptake and subsequent slow redistribution of amlodipine into the perfusate have been demonstrated. The apparent liver volume for amlodipine was 920 ml compared with 38ml for nitrendipine. 2. Metabolism is the major clearance mechanism of amlodipine and nitrendipine in animals and man. In the IPRL, the intrinsic (metabolic) clearance and first-pass extraction values for amlodipine are similar to those of nitrendipine. This is in contrast with in vitro metabolic stability data in rat liver microsomes which indicate about 40-fold greater metabolic stability for amlodipine. 3. The discrepancy between relative clearance rates for the two preparations may be explained by consideration of the hepatic volume of the two compounds, with the higher liver volume of amlodipine amplifying the whole organ clearance.

Amlodipine↗

A database obtained from in vitro function testing of mechanical heart valves.

The in vitro function of the CarboMedics, Medtronic Hall, Omniscience, Starr-Edwards, St. Jude and Sorin (formerly Shiley) Monostrut heart valves have been compared using a pulsatile flow model left heart and load system. A wide range of flows and heart rates were used. The above valves in all sizes and in both aortic and mitral positions were tested. Results for transvalvular pressure, regurgitation and effective orifice area are presented. The small size St. Jude valves showed the least transvalvular pressure and largest effective orifice area. For large valves, the least regurgitation was exhibited by the Starr-Edwards valve. The data provides a reference for the range of normal performance that can be expected of mechanical prosthetic heart valves.

Aortic Valve↗

Relationship among bile tolerance, bile salt deconjugation, and assimilation of cholesterol by Lactobacillus acidophilus.

The relationships among growth in the presence of bile, deconjugation of sodium taurocholate, and assimilation of cholesterol by 19 cultures of Lactobacillus acidophilus were examined. Cultures of L. acidophilus were grown at 37 degrees C in lactobacilli MRS broth supplemented with sodium thioglycollate, sodium taurocholate, and cholesterol (cholesterol phosphatidyl choline micelles). Deconjugation activity was maximum in the late exponential phase of growth, which also coincided with maximum assimilation of cholesterol. Considerable variation existed among cultures in their ability to grow in the presence of bile, to deconjugate sodium taurocholate, and to assimilate cholesterol. However, statistical analyses revealed no significant correlations.

Bile↗

Issues involved in the definition and classification of chronic health conditions.

The need for a widely applicable definition of chronic conditions for research, policy, and program development has led to an extensive review of the development of such definitions, the considerations involved in their use, and some recommendations for a new approach. This paper examines some of the methodologic and conceptual issues related to defining and classifying chronic conditions and describes some consequences resulting from decisions made about these issues. While most examples are taken from child health applications, the basic concepts apply to all age groups. The dominant method for identifying and classifying children as having a chronic condition has relied on the presence of an individual health condition of lengthy duration. This condition-specific or "categorical" approach has increasingly seemed neither pragmatically nor conceptually sound. Thus, the development of a "generic" approach, which focuses on elements that are shared by many conditions, children, and families, is recommended. Such a definition might reflect the child's functional status or ongoing use of medical services over a specified time period. In addition, it is suggested that conditions be classified based on the experience of individual children, thus emphasizing the tremendous variability in expression of seemingly similar conditions.

Child↗

Pharmacokinetics and metabolism of dofetilide in mouse, rat, dog and man.

1. Pharmacokinetics of dofetilide were studied in man, dog, rat and mouse after single i.v. and oral doses of dofetilide or 14C-dofetilide. 2. Dofetilide was absorbed completely in all species. Low metabolic clearance in man resulted in complete bioavailability following oral administration. Higher metabolic clearance in rodents, and to a lesser extent dogs, resulted in decreased bioavailability because of first-pass metabolism. 3. Following i.v. administration, the volume of distribution showed only moderate variation in all species (2.8-6.3 l/kg). High plasma clearance in rodents resulted in short half-life values (mouse 0.32, male rat 0.5 and female rat 1.2 h), whilst lower clearance in dog and man gave longer terminal elimination half-lives (4.6 and 7.6 h respectively). 4. After single i.v. doses of 14C-dofetilide, unchanged drug was the major component excreted in urine of all species with several metabolites also present. 5. Metabolites identified in urine from all species were formed by N-oxidation or N-dealkylation of the tertiary nitrogen atom of dofetilide. 6. After oral and i.v. administration of 14C-dofetilide to man, parent compound was the only detectable component present in plasma and represented 75% of plasma radioactivity. No single metabolite accounted for greater than 5% of plasma radioactivity.

Administration, Oral↗

Liquid-liquid extraction and high-performance liquid chromatography for the determination of a novel antidysrhythmic agent (UK-68,798) in human urine.

A routine method for the determination of a novel class III antidysrhythmic agent, 1-(4-methanesulphonamidophenoxy)-2-[N-(4-methanesulponamidophen ethyl)- N-methylamino]ethane, in human urine has been developed. The method involves solvent extraction followed by high-performance liquid chromatography on an unmodified silica column with ultraviolet detection. Despite a low recovery of drug through the three-stage extraction procedure a reliable assay with high precision (coefficient of variation less than 6%) and a limit of determination of 2.5 ng/ml was achieved. The method has been applied to the analysis of samples following single oral and intravenous doses of 1-12.5 micrograms/kg of the drug to human volunteers.

Anti-Arrhythmia Agents↗

Discrimination in vitro between the acoustic emissions from Bjork-Shiley convexo-concave valves with and without a broken minor strut.

A statistical pattern recognition technique is used to learn and recognise the frequency spectra of the closing sounds emitted by Bjork-Shiley convexo-concave heart valves, with and without fractured minor struts, when operating in vitro. The sounds are generated with test valves operating under a variety of conditions in a model left ventricle. It is found in the learning stage that the discriminant functions generated correctly classified almost all of the cases within the learning set. When applied to cases outside the learning set, including a recording of a clinically implanted valve, the functions correctly classify the valves. These preliminary results, for a limited number of valves, lead us to believe that the discriminant analysis of heart valve sounds is a promising noninvasive method for screening patients with implanted Bjork-Shiley convexo-concave valves.

Heart Valve Prosthesis↗

Measurement of the class III antidysrhythmic drug, UK-68,798, in plasma by radioimmunoassay.

A sensitive radioimmunoassay (RIA) for the specific determination of 1-(4-methanesulphonamidophenoxy)-2-[N-(4-methanesulphonamido -phenethyl)-N- methylamino]ethane (UK-68,798), a novel class III antidysrhythmic agent, in human plasma is described. Specific antisera were raised in sheep using desmesyl-UK-68,798-succinate-ovalbumin conjugate as the antigenic hapten carrier protein. The antisera produced exhibited high specificity for UK-68,798 compared with known metabolites from animals, other antidysrhythmic agents and co-administered drugs. Good correlation was found in a comparison of the RIA method with a high-performance liquid chromatography (HPLC) method (r = 0.997) and a 10-fold lower limit of determination was observed for the RIA method compared with the HPLC method (0.05 and 0.5 ng ml-1, respectively). The RIA method was applied to the analysis of UK-68,798 in plasma obtained from human volunteers receiving the compound.

Animals↗

Technology's children: report of a statewide census of children dependent on medical supports.

In April 1987, a census of children dependent on medical technology was carried out in Massachusetts to determine the one-month point prevalence. All medical and educational providers in the state who were likely to interact with such children were contacted and asked to complete a two-sided data form on youngsters (aged 3 months to 18 years) with tracheostomies, supplementary oxygen, respirators, suctioning, gastric feeding, central venous lines, ostomies, ureteral diversion, urethral catheterization and dialysis. Nearly 1250 children were found meeting these criteria. Capture-recapture analysis set the lower bound for technology dependence at 0.08% of the state's children. An analysis of the organ systems involved showed that 57% of the children had neurologic involvement--13% multisystem, 7% gastrointestinal-metabolic, 4% renal-genitourinary, and 3% musculoskeletal. Less than 1% of the children were reported as having immunologic or "other" disorders. Review of putative etiologies indicated that 45% of the children had congenital anomalies, 33% chronic medical diseases, 9% perinatal conditions, 7% hereditary-genetic disorders, 5% injuries, 2% infections, and 3% "other." The substantial prevalence of technology dependency among children creates challenges at the social, economic, and policy-making levels. It will be important to carry out systematic reporting and monitoring activities throughout time and across sites. This census is an example of one such statewide effort.

Adolescent↗

Balloon dilatation of the stenosed aortic valve: how does it work? Why does it fail?

The hemodynamic changes that may occur in patients undergoing aortic balloon valvuloplasty were examined in the circulatory model. Four conclusions were reached. (1) Significant transvalvular pressure gradients appear only if the orifice is severely narrowed. (2) The magnitude of this gradient is highly flow dependent. (3) At critical narrowings, minute alterations in orifice size may induce most significant changes in the transvalvular gradient. (4) In low flow states significant gradients appear only if the stenosis is extreme. In patients with aortic stenosis, especially those with failing hearts and low cardiac output, the pressure gradient may be effectively decreased by minimal dilatation of the aortic orifice. These patients, however, remain in jeopardy because recurrent narrowing may cause a gradient incompatible with life.

Aortic Valve↗

Factors to consider when selecting a culture of Lactobacillus acidophilus as a dietary adjunct to produce a hypocholesterolemic effect in humans.

Significant variations in bile tolerance and ability to assimilate cholesterol were observed among 12 cultures of Lactobacillus acidophilus of human origin. The degree of bile tolerance as measured by rapidity of growth in MRS broth supplemented with .3% oxgall could not be predicted by the rapidity of growth in the broth without oxgall. There was no apparent direct relationship between bile tolerance and cholesterol assimilation. However, among the cultures that most actively assimilated cholesterol, there were significant differences in bile tolerance. The most active cholesterol-assimilating cultures also varied in the ability to produce bacteriocins. A culture of L. acidophilus of human origin, which assimilates cholesterol, grows well in presence of bile, and produces bacteriocins can be selected for use as a dietary adjunct for humans. A culture of L. acidophilus possessing all these characteristics should have an advantage over one that does not in establishing and functioning in the intestinal tract to assimilate cholesterol.

Bacteriocins↗

Providing therapeutic services to children in special educational placements: an analysis of the related services provisions of Public Law 94-142 in five urban school districts.

Using the sample of 1726 special education students from the Collaborative Study of Children With Special Needs, the authors describe the related services being provided to the children and then analyze the relationship between service provision and class placement. Related services are provided in all settings, with a concentration in special schools and special classes. For even the most severely involved children the trade-off with academics is no more than 1 hour per day. It is argued that schools now are major sites of therapeutic service provision for children with special needs.

Child↗

Chronic conditions, socioeconomic risks, and behavioral problems in children and adolescents.

Children with a chronic health condition have long been considered at excess risk for psychosocial morbidity. Despite an increasing prevalence of chronic childhood conditions and heightened concerns for the quality of life of the chronically ill, population-based studies of behavior problems among children with chronic physical conditions are rare. Findings on the epidemiology of behavior problems in a nationally representative sample of 11,699 children and adolescents aged 4 to 17 years in the United States are reported. Data included a 32-item parent-reported behavior problem index, measures of chronic childhood conditions, measures of school placement and performance, and sociodemographic variables. Analyses confirmed that chronic physical conditions were a significant risk factor for behavior problems, independent of sociodemographic variables. Among children these differences were observed across all subscales; among adolescents the largest differences were found for the Depression/Anxiety and Peer Conflict/Social Withdrawal subscales. Rates of extreme behavior problem scores (those in the top 10th percentile) were 1.55 times higher among children with a chronic health condition compared with children without a chronic condition (95% confidence interval 1.29 to 1.86). These independent odds were lowered to 1.44 when covariates for confounding were introduced via a multivariate logistic regression. Other independent risks included the absence of either biologic parent (odds ratio 2.05), male gender (1.53), low vs high family income (1.30), low vs high maternal education (1.51), and young vs old maternal age at childbirth (2.57). Chronic health conditions were also a major risk factor for placement in special education classes and having to repeat grades. Despite evidence for effective interventions, health services for children with chronic conditions--particularly mental health services--remain fragmented, signaling the need for increased attention to behavioral problems and their treatment among all health professionals caring for children.

Adolescent↗

Maternal smoking and childhood asthma.

According to a substantial literature, passive smoking by children is associated with an increased incidence of lower respiratory illness and diminished pulmonary function. The relationship between passive smoking and childhood asthma, however, is not clear. Data from the Child Health Supplement to the 1981 National Health Interview Survey were analyzed with information about 4331 children aged 0 to 5 years to study the relationship between maternal smoking and (1) the prevalence of childhood asthma, (1) the likelihood of taking asthma medication, (3) the age of onset of children's asthma, and (4) the number of hospitalizations among children with and without asthma. An odds ratio for asthma of 2.1 was shown by multivariate logistic regressions among children whose mothers smoke 0.5 packs of cigarettes or more per day compared with children of nonsmokers (P = .001). In similar analyses maternal smoking of 0.5 packs per day was identified as an independent risk for children's use of asthma medications (odds ratio 4.6, P = .0006) and for asthma developing in the first year of life (odds ratio 2.6, P = .0006). Maternal smoking is also associated with increased numbers of hospitalizations by its association with an increased risk of asthma as well as by contributing to hospitalizations independently of a child having asthma. Among children with asthma, however, maternal smoking is not associated with increased numbers of hospitalizations. It was concluded that maternal smoking is associated with higher rates of asthma, an increased likelihood of using asthma medications, and an earlier onset of the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Asthma↗

Assessing psychosocial adjustment of children with chronic illnesses: a review of the technical properties of PARS III.

Four groups of investigators in the Research Consortium on Chronic Illness in Childhood have used the Personal Adjustment and Role Skills Scale (PARS) III to assess the psychosocial adjustment of children with chronic physical illnesses and no mental impairment. The PARS III consists of 28 items that measure psychosocial functioning in six areas: peer relations, dependency, hostility, productivity, anxiety-depression, and withdrawal. Analyses of the measure's reliability and validity, using a total combined sample of 450 school-age children (ages 5-18 years) with a variety of chronic illnesses and three comparison samples of healthy children, provide evidence that the PARS III can be used successfully to assess psychosocial adjustment of children with chronic illnesses and no cognitive impairments.

Adolescent↗