Search PubMed⌕ Search

Biomedical subjects

A Stewart

Publications and source records attributed to A Stewart.

At least 109 records · Page 6Linked to original sources
PubMed1999

The relevance of occupational epidemiology to radiation protection standards.

Large-scale epidemiological studies of U.S. Department of Energy workers have been underway since the 1960s. Despite the increasing availability of information about long-term follow-up of badge-monitored nuclear workers, standard-setting bodies continue to rely on the Life Span Study (LSS) of A-bomb survivors as the primary epidemiological basis for making judgments about hazards of low-level radiation. Additionally, faith in the internal and external validity of studies of A-bomb survivors has influenced decisions about the design, analysis, and interpretation of many worker studies. A systematic comparison of the LSS and worker studies in terms of population characteristics, types of radiation exposures, selection factors, and dosimetry errors suggests that the priority given to dose response findings from the LSS is no longer warranted. Evidence from worker studies suggests that excess radiation-related cancer deaths occur at doses below the current occupational limits; low-dose effects have also been seen in studies of childhood cancers in relation to fetal irradiation. These findings should be considered in revising current radiation protection standards.

Journal Article↗
PubMed1999

Bone density and bone turnover in patients with osteoarthritis and osteoporosis.

OBJECTIVE: Osteoarthritis (OA) and osteoporosis (OP) are reported to be rare in the same patient. We examined bone mass, bone turnover, and radiological presence of OA in a group of patients with OA with previous hip fractures and age matched controls. METHODS: Bone mass was assessed by bone mineral density (BMD), using dual energy x-ray absorptiometry (DEXA) of the hip and total body, and quantitative ultrasound of the os calcis, measuring broadband ultrasound attenuation and velocity of sound. Bone turnover was assessed by measuring urinary pyridinium crosslinks and serum osteocalcin. RESULTS: There were differences in bone density, the patients with OP having lower bone density, while patients with OA had similar or increased bone density compared to controls, Serum osteocalcin showed no significant differences among the 3 groups of patients. Urinary pyridinium crosslinks excretion was significantly elevated in the OA group but not in the OP group compared with controls. CONCLUSION: Increased bone turnover was restricted to the OA group.

Absorptiometry, Photon↗
PubMed1999

Early brain proton magnetic resonance spectroscopy and neonatal neurology related to neurodevelopmental outcome at 1 year in term infants after presumed hypoxic-ischaemic brain injury.

This study investigated the accuracy of prediction of neurodevelopmental outcome at 1 year using cerebral proton magnetic resonance spectroscopy (MRS) and structured neonatal neurological assessment in term infants after presumed hypoxic-ischaemic brain injury. Eighteen control infants and 28 infants with presumed hypoxic-ischaemic brain injury underwent proton MRS investigation. Studies were carried out as soon as possible after the cerebral insult, most within 48 hours. Infants had an early structured neurological assessment at a median of 19 hours (range 0 hours to 9 days) from the presumed hypoxic-ischaemic insult and a late assessment at a median of 7 days (range 3 to 25 days) during recovery. The maximum cerebral peak-area ratio lactate:N-acetylaspartate measured by proton MRS accurately predicted adverse outcome at 1 year with a specificity of 93% and positive predictive value of 92%. Neurological assessment had a tendency for false-positive predictions. However, both early and late neurological examination can be used as a reliable indicator for a favourable outcome at 1 year having negative predictive values of 100% and 91% respectively.

Brain Ischemia↗
PubMed1999

Pharmacokinetics of calcium absorption from two commercial calcium supplements.

This study was conducted to compare pharmacokinetic indices of calcium absorption after a single oral (500 mg calcium) load of Citracal (calcium citrate) and Os-Cal (calcium carbonate). In 18 postmenopausal normal women, venous blood samples were obtained for the measurement of calcium before and hourly for 6 hours after an oral ingestion of Citracal, Os-Cal, or placebo with a breakfast meal. The change in area under the curve (delta AUC) in serum calcium from preload was 2.5-fold greater for Citracal than Os-Cal, and the peak-basal variation in serum calcium was 76% higher for Citracal than Os-Cal. The increment in serum calcium from preload after Citracal administration was significantly higher than that obtained after placebo load during most time periods and significantly higher than that of Os-Cal at 1, 4, and 5 hours after load. In contrast, delta AUC and peak basal variation of Os-Cal did not differ significantly from placebo and increment in serum calcium was significantly increased from placebo only at 6 hours. In conclusion, Citracal is much more bioavailable than Os-Cal.

Absorption↗
PubMed1999

Implementing a nurse information system in a nurse-managed primary care practice: a process in progress.

As part of a larger project, a nurse-managed primary care clinic (Valencia Pediatric and Family Practice) sought to implement a nursing information system for the purposes of (1) patient record keeping, (2) capturing advanced practice nursing interventions and outcomes and transforming them into standardized language, (3) project data management, and (4) evaluating advanced practice nursing care thereby improving and standardizing quality of care. This article represents the background information for selection of a data management system and early experiences of implementation.

Database Management Systems↗
PubMed1998

Pharmacotherapy for people with Alzheimer's disease: a Markov-cycle evaluation of five years' therapy using donepezil.

This article combines data from a clinical trial of donepezil with costing figures to evaluate expected direct costs of care over 5 years after diagnosis of Alzheimer's disease (AD) for patients aged 75 years and over at diagnosis. A Markov model simulates the progression of elderly persons through changing levels of severity. The model compares three treatment regimes for each of two patient groups; mild AD at start of treatment; moderate AD at start of treatment. Patients are followed until 5 years after the start of the treatment. Despite the acquisition costs, use of donepezil is approximately cost-neutral for both 5 mg and 10 mg treatment groups and for patients initially at either mild or moderate states of illness. Expected costs are slightly higher than for the placebo group, but higher expenditure on drugs is partly offset by lower costs of care consequent on treated patients not declining as rapidly as those untreated. The model showed that donepezil patients spent less time in the state of severe dementia, where costs of care are higher. Sensitivity analysis on key assumptions demonstrated that expected costs were highly dependent on discount rate and, more significantly, on the mortality rate.

Aged↗
PubMed1998

Optimal selection of antiemetics in children receiving cancer chemotherapy.

Only a few studies have been carried out specifically on the prevention of nausea and vomiting in children receiving chemotherapy. In these patients older antiemetic drugs such as metoclopramide and phenothiazines had moderate efficacy and induced significant side effects, especially marked sedation and extrapyramidal reactions. In comparative trials the 5-HT3 receptor antagonists have shown better efficacy and tolerability than chlorpromazine or metoclopramide combined with dexamethasone. The combination of a 5-HT3 receptor antagonist plus dexamethasone is superior to a 5-HT3 receptor antagonist alone and should be the standard antiemetic prophylaxis in all paediatric patients receiving highly or moderately emetogenic chemotherapy. The optimal dose and scheduling of these antiemetic drugs need to be studied, as well as the antiemetic efficacy, in the prevention of chemotherapy-induced delayed and anticipatory emesis in children.

Antiemetics↗
PubMed1998

Choosing an antidepressant: effectiveness based pharmacoeconomics.

BACKGROUND: SSRIs have been one of the major innovations in psychopharmacology in recent years. The debate over the competing claims of SSRIs and the older, cheaper TCAs has implications for clinical practice and prescribing expenditure. Several reviewers have focused on acquisition costs and stressed the higher costs associated with using SSRIs. METHODS: Recently there have been several applications of economics to the issue of whether to use SSRIs or TCAs as first-line antidepressants. Most have argued that there is an economic case for using SSRIs. Several previous papers have used modelling techniques and decision analysis to generate economic evaluations from clinical trials. This paper examines some recent studies based on retrospective evaluations of real patients and real practices. Their methods and results are summarised and discussed. RESULTS: They all suggest that in practice, where concerns are with effectiveness rather than efficacy, there are advantages to be gained from using SSRIs. CONCLUSIONS: There are important questions about how to perform such economic evaluations. Clinical practice has long viewed the RCT as a 'gold standard' for evaluation. Some SSRI/TCA comparisons, incorporating economic studies, are under way and will be reported on eventually. When they appear, these studies should be examined carefully for their implications for antidepressant prescribing.

Antidepressive Agents, Second-Generation↗
PubMed1998

Hodgkin's lymphoma of the nasopharynx.

The lymphoid tissues of Waldeyer's ring, including the nasopharynx, are very rare sites for Hodgkin's disease and are considered to be relatively resistant to it. This report of a case of Hodgkin's disease of the post-nasal space demonstrates the difficulty of making the diagnosis histologically and the characteristic immunohistochemical features of this disease. Before immunohistochemistry became so widely available, some authors speculated it might be underdiagnosed (Eavey and Goodman, 1982; O'Reilly and Kershaw, 1987). Judging by its continued rarity, this appears not to be the case.

Cell Membrane↗
PubMed1998

Influence of prenatal mercury exposure upon scholastic and psychological test performance: benchmark analysis of a New Zealand cohort.

This paper presents benchmark (BMD) calculations and additional regression analyses of data from a study in which scores from 26 scholastic and psychological tests administered to 237 6- and 7-year-old New Zealand children were correlated with the mercury concentration in their mothers' hair during pregnancy. The original analyses of five test scores found an association between high prenatal mercury exposure and decreased test performance, using category variables for mercury exposure. Our regression analyses, which utilized the actual hair mercury level, did not find significant associations between mercury and children's test scores. However, this finding was highly influenced by a single child whose mother's mercury hair level (86 mg/kg) was more than four times that of any other mother. When that child was omitted, results were more indicative of a mercury effect and scores on six tests were significantly associated with the mothers' hair mercury level. BMDs calculated from five tests ranged from 32 to 73 mg/kg hair mercury, and corresponding BMDLs (95% lower limits on BMDs) ranged from 17 to 24 mg/kg. When the child with the highest mercury level was omitted, BMDs ranged from 13 to 21 mg/kg, and corresponding BMDLs ranged from 7.4 to 10 mg/kg.

Achievement↗
PubMed1998

Epilepsy in very preterm infants: neonatal cranial ultrasound reveals a high-risk subcategory.

The aim of this study was to investigate the association between epilepsy and perinatal brain injury in a cohort of 610 infants born preterm at <33 weeks' gestation. The prevalence of epilepsy in this cohort was 4.3% as determined by a postal questionnaire survey. Most children with epilepsy (16 of 24) had high-risk cranial ultrasound lesions including haemorrhagic parenchymal infarction (HPI), posthaemorrhagic hydrocephalus, and cystic periventricular leukomalacia (PVL). Of all the children in our cohort with high-risk brain lesions, those with epilepsy were more likely to have HPI and significantly less likely to have cystic PVL, although it is possible that PVL was not noticed in some cases. Children with epilepsy and high-risk cranial ultrasound lesions also showed more cognitive impairment than children with high-risk lesions but no epilepsy, which suggested more cortical grey-matter damage. We suggest that brain injury has occurred outside the confines of the periventricular white matter in this group of preterm infants with epilepsy.

Brain↗
PubMed1998

Barbados Low Dose Aspirin Study in Pregnancy (BLASP): a randomised trial for the prevention of pre-eclampsia and its complications.

OBJECTIVE: To determine whether prophylactic, low dose controlled-release aspirin improves outcome for pregnant women and their babies in Barbados. DESIGN: Randomised placebo-controlled trial. SETTING: The Queen Elizabeth Hospital, Barbados. POPULATION: All women attending antenatal clinics between 12 and 32 weeks of gestation were eligible, if without specific contraindications to aspirin and unlikely to deliver immediately. METHODS: Randomisation was computer-generated in the antenatal clinic; 1822 women were allocated to receive 75 mg controlled-release aspirin and 1825 matching placebo. MAIN OUTCOME MEASURES: Proteinuric pre-eclampsia, other pregnancy-induced hypertension, pregnancy duration, birthweight, stillbirths and neonatal deaths, major neonatal events. RESULTS: All but three women from each group were followed up successfully. Forty-four percent were primigravid, and 8% had previous obstetric complications. There were no significant differences between the allocated treatment groups in the incidence of proteinuric pre-eclampsia (40 [2.2%] of those allocated aspirin, compared with 46 [2.5%] allocated placebo), of preterm delivery (255 [14.0%] vs 270 [14.8%]), of birthweight < 1500 g (32 [1.7%] vs 33 [1.8%]) or of stillbirth and neonatal death (44 [2.4%] vs 38 [2.1%]). Aspirin was not associated with excess risk of maternal or fetal bleeding. CONCLUSIONS: The results of this study in Barbados do not support the routine use of low dose aspirin for prevention of pre-eclampsia or its complications, confirming results of previous large trials in other settings.

Adult↗