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Biomedical subjects

R Brown

Publications and source records attributed to R Brown.

At least 343 records · Page 19Linked to original sources
PubMed1996

Intramuscular rocuronium in infants and children. Dose-ranging and tracheal intubating conditions.

BACKGROUND: Rocuronium's rapid onset and intermediate duration of action with intravenous administration suggests that intramuscular administration might facilitate tracheal intubation without producing prolonged paralysis. Accordingly, in infants and children, the authors measured onset at the adductor pollicis and respiratory muscles to determine the optimal dose (phase I), then gave this optimal dose to determine the optimal time for tracheal intubation (phase II). METHODS: The authors studied 45 unpremedicated patients aged 3 months to 5 yr. In phase I, 25 patients were anesthetized with nitrous oxide and halothane and breathed spontaneously; twitch tension and minute ventilation were measured. Rocuronium (800-2,400 micrograms/kg) was injected into the quadriceps or deltoid muscle; doses varied, using an "up-down" technique, the goal being to bracket the dose depressing twitch 75-90% within 5 min. In phase II, deltoid injections of the optimal dose from phase I (infants: 1,000 micrograms/kg; children: 1,800 micrograms/kg) were given to 20 patients anesthetized with 0.82-1.0% halothane. Tracheal intubation was attempted 1.5-3.0 min later; time to tracheal intubation was varied, using an "up-down" technique. RESULTS: In phase I, 5 of 7 patients given quadriceps injections (1,200-2,200 micrograms/kg) had slow onset of twitch and ventilatory depression. With deltoid injections (800-2,400 micrograms/kg), all patients developed complete twitch depression; median time to 50% depression of minute ventilation was 3.2 min in infants and 2.8 min in children. In phase II, intubating conditions were consistently adequate or good-excellent at 2.5 min in infants and 3.0 min in children. Initial twitch recovery was at 57 +/- 13 min (mean +/- SD) in infants and 70 +/- 23 min in children. CONCLUSIONS: Deltoid injections of rocuronium, 1,000 micrograms/kg in infants and 1,800 micrograms/kg in children, rapidly permit tracheal intubation in infants and children, despite a light plane of anesthesia. Duration of action of these large doses might limit clinical utility.

Androstanols↗
PubMed1996

Nipple-areolar perfusion and reduction mammaplasty: correlation of laser Doppler readings with surgical complications.

Clinical assessment of nipple-areolar perfusion by color, capillary refill, and temperature during and after reduction mammaplasty is generally satisfactory. However, the estimation of vascular perfusion in patients with very large breasts or dark-skinned women is difficult. If marginal perfusion of the nipple-areolar areas is undetected, necrosis is likely. To this point, no studies have tested the ability of the laser Doppler perfusion monitor to give absolute alarm values that would suggest marginal perfusion in the nipple-areola following reduction mammaplasty. We therefore completed a prospective study of areolar perfusion during surgery and for up to 24 hours following reduction mammaplasty. Fifty-four patients were studied and data collected from 104 breasts. Laser Doppler perfusion was measured with a LASERFLO BPM2 Blood Perfusion Monitor (Vasamedics, St. Paul, Minn.). Perfusion values were recorded for each breast following anesthesia but prior to the incisions, at the end of surgery, and every 2 hours for 24 hours. Patients were divided into three groups according to their follow-up results: no complications (92 breasts), minor complications (9 breasts), and patients with tissue necrosis (3 breasts). The no complications group had a perfusion of 4.8 ml/min/100 gm following the reduction procedure, while the minor complications and tissue necrosis groups had average perfusions of 1.4 and 0.8, respectively, immediately after incision closure. The average tissue removed from each group was 811, 1171, and 2118 gm for the no complications, minor complications, and tissue necrosis groups, respectively. The results from this study suggest that a laser Doppler perfusion monitor could prove useful for monitoring areolar perfusion following reduction mammaplasty, especially in patients with extremely large breasts and/or dark skin. Our studies have shown that laser Doppler perfusion values that consistently are in the range of 1.0 to 2.0 ml/min/100 gm indicate marginal perfusion, and the recovery of these patients should be followed closely. Furthermore, patients with consistent perfusion values equal to or less than 1.0 coupled with other clinical signs of low perfusion should be considered for suture removal and/or free nipple graft.

Adult↗
PubMed1996

Obstacles and opportunities in designing cancer control communication research for farmworkers on the Delmarva Peninsula.

Little is known about the incidence of cancer among farmworker populations or about effective strategies for communicating with farmworkers about cancer prevention. Some studies suggest that farmworkers may have unusually high incidences of skin and cervical cancers. With these two cancers as the focus, a group of interviewers, researchers, and health communication specialists set out to create, implement, and evaluate a cancer control demonstration project geared toward farmworkers. In 1994, a situation analysis was conducted to identify constraints and opportunities for providing farmworkers with cancer control information and services. The situation analysis provided valuable information to aid in developing intervention and evaluation strategies. This paper outlines how and why the situation analysis was conducted and what was learned with regard to the farmworker population on the Delmarva Peninsula. Living conditions and the local availability of cancer control services are described. Obstacles to conducting research and interventions with farmworkers are highlighted. Based on what was learned, recommendations are made for designing cancer control research and intervention for farmworkers.

Agriculture↗
PubMed1996

A comparison of mixed integer programming and fast simulated annealing for optimizing beam weights in radiation therapy.

Two competing methods for assigning intensities to radiation treatment beams were tested. One method was derived from mixed integer programming and the other was based on simulated annealing. The methods faced a common objective and identical constraints. The goal was to maximize the minimum tumor dose while keeping the dose in required fractions of normal organ volumes below a threshold for damage. The minimum tumor doses of the two methods were compared when all the dose-volume constraints were satisfied. A mixed integer linear program gave a minimum tumor dose that was at least 1.8 Gy higher than that given by simulated annealing in 7 of 19 trials. The difference was > or = 5.4 Gy in 4 of 19 trials. In no case was the mixed integer solution one fraction size (1.8 Gy) worse than that of simulated annealing. The better solution provided by the mixed integer program allows tumor dose to increase without violating the dose-volume limits of normal tissues.

Abdominal Neoplasms↗
PubMed1996

A generic genetic algorithm for generating beam weights.

A genetic algorithm for generating beam weights is described. The algorithm improves an objective measure of the dose distribution while respecting dose volume constraints placed on critical structures. The algorithm was used to select beam weights for treatment of abdominal tumors. Weights were selected for up to 36 beams. Dose volume limits were placed on normal organs and a dose inhomogeneity limit was placed on tumor. Volumes were represented as sets of several hundred discrete points. The algorithm searched for the beam weights that would make the minimum tumor dose as high as the constraints would allow. The results were checked using dose volume histograms with standard sized grids. Nineteen trials were created using six patient cases by changing the required field margin or allowed beam position in each case. The sampling of points was sufficiently dense to yield solutions that strictly satisfied the constraints when the prescribed dose was renormalized by a factor of less than 6%. The genetic algorithm supplied solutions in 49 min on average, and in a maximum time of 87 min. The randomized search does not guarantee optimality, but high tumor doses were obtained. An example is shown for which the solution of the genetic algorithm gave a minimum tumor dose 7 Gy higher than the solution given by a simulated annealing algorithm under the same set of constraints. The genetic algorithm can be generalized to admit nonlinear functions of the beam intensities in the objective or in the constraints. These can include tumor control and normal tissue complication probabilities. The genetic algorithm is an attractive procedure for assigning beam weights in multifield plans. It improves the dose distribution while respecting specified rules for tissue tolerance.

Abdominal Neoplasms↗
PubMed1996

Decision making in resuscitation from out of hospital cardiac arrest.

OBJECTIVE: To determine which factors are perceived by senior house officers (SHOs), consultants, and medical registrars in accident and emergency (A&E) medicine as being important in decision making. METHODS: 132 SHOs in A&E medicine, of 172 attending an induction course at the start of their job (77%), completed a questionnaire relating to 20 factors of possible importance in decision making; 73 completed the questionnaire at six weeks and 55 at six months. Ten medical registrars and 31 consultants in A&E medicine also completed the questionnaire. RESULTS: The SHOs were able to recognise bystander cardiopulmonary resuscitation and early advanced I support, as well as the presence of ventricular fibrillation, as important prognostic factors. There was considerable variation in all three groups in their opinions on the importance of the other factors considered. There was no obvious change in SHO responses over the period of training. CONCLUSIONS: Lack of guidelines may result in more patients receiving resuscitation than are salvageable, as doctors maintain a low threshold for continuing resuscitation to avoid missing potential survivors. A decision making algorithm is recommended.

Attitude of Health Personnel↗
PubMed1996

Trends in the use of accident and emergency services by the homeless on the Wirral.

OBJECTIVE: To examine the use of accident and emergency (A&E) services by the homeless, with particular reference to the use of psychiatric services generated by this attendance. METHODS: A retrospective study of attendance registers at a large A&E department over an eight year period, during which there were 566 separate attendances by homeless patients out of a total of 421 237 adult attendances (1.3 per 1000). RESULTS: There was no significant change in rates of attendances over the eight year period (P = 0.41), in the broad demographic details of the groups, or in the use of psychiatric services. CONCLUSIONS: There has been no significant increase in the use of A&E services by homeless people in the population studied over the eight year period. Several possible explanations for this are given.

Adult↗
PubMed1996

Air hunger induced by acute increase in PCO2 adapts to chronic elevation of PCO2 in ventilated humans.

Brief increases in arterial PCO2 (PaCO2) (lasting several minutes) produce a sensation of respiratory discomfort (air hunger). It is not known whether air hunger adapts to chronic changes in PaCO2. This study tested whether the level of end-tidal PCO2 (PETCO2) required to evoke air hunger would increase with chronic elevation of PETCO2 (lasting several days). Four ventilator-dependent subjects participated in a 2-wk study during which they were ventilated with air (placebo) or air rich in CO2 (CO2 exposure). Average resting PETCO2 during control periods was 25 Torr (typical for such patients); PETCO2 was 15 Torr higher during CO2 exposure. Ventilation and arterial PO2 did not differ between conditions. Periodically, we performed tests in which subjects rated the intensity of air hunger induced by brief increases in PETCO2. The increase in PETCO2 required to elicit a given air hunger rating during CO2 exposure also increased by approximately 15 Torr. That is, subjects' sensation of air hunger fully adapted to the chronic increase in PETCO2. Arterial pH did not fully return to control values during CO2 exposure. Accommodation in the chemoreceptors and neural pathways that subserve air hunger sensation may explain the adaptation of air hunger.

Adaptation, Physiological↗
PubMed1996

A new decision model for cost-utility comparisons of chemotherapy in recurrent metastatic breast cancer.

In the absence of comparative clinical and pharmacoeconomic trial data for docetaxel versus paclitaxel as second-line therapy for patients with anthracycline-resistant metastatic breast cancer, a computer-based decision-analysis model was designed to evaluate the comparative utility to patients of these two taxoids. The model used the Markov process to analyse disease states (response, stable disease, progressive disease) and toxicities (acute, cumulative) for each treatment during the period from commencement of up to six 3-weekly cycles of chemotherapy, to death. A cost-utility analysis was carried out using the model, with a probability, a cost and a utility determined for each health state. Response rates were obtained from clinical trial data supplemented by expert clinical opinion. Costs were taken from UK national databases and published sources and the published UK prices of docetaxel and paclitaxel. Utilities for the various health states were established by use of standard gamble and visual analogue methods assessed by 30 oncology nurses in the UK who were acting as proxy patients. The results of the model showed that response rate is the key parameter determining the utility and cost utility of treatments for metastatic breast cancer. Although the total per-patient cost associated with docetaxel was marginally higher than that for paclitaxel (8233 pounds vs 8013 pounds), the higher response rate associated with docetaxel produced an improvement in utility to the patient at an incremental healthcare cost that is acceptable according to available defined limits. Sensitivity analyses revealed that, although the model was sensitive to changes in response rate and drug costs, the cost-utility ratio for docetaxel versus paclitaxel varied within acceptable limits in response to all likely changes in key parameters. In summary, in the base case used in this model, docetaxel produces a substantially larger utility benefit than paclitaxel, at a small additional cost per QALY gained (equivalent to 7 pounds per additional day of perfect health).

Breast Neoplasms↗
PubMed1996

Ergonomic data of elderly people and their application in rehabilitation design.

The population of the First World is ageing, and as it does so elderly people are becoming an increasingly significant consumer group. This process has important ramifications for the ergonomics and design professions. The demand for products that have been developed with consideration for the elderly consumer will require designers to develop new skills and ergonomists to supply new data. This paper highlights the inadequacy of current design data pertaining to the elderly. Anthropometric studies which have been carried out within the fields of ergonomics and rehabilitation are reviewed, and their usefulness to the product designer discussed. Recommendations are made regarding future needs for the collection and dissemination of further data.

Activities of Daily Living↗
PubMed1996

Learning and generating human natural behaviours for design evaluation using artificial neural networks.

Biomechanical consideration is becoming very important when designing a product. Animation and strength prediction tools are available to perform the necessary analysis. However with most of these tools, animation is achieved via a sequence of key frames constructed by manipulating the human model to the desired position in each key frame. The resulting motion is therefore unnatural. Most strength predictions are based on static strength measurements of a selected population. Existing prediction tools are not flexible so as to allow data from other populations and/or additional parameters such as dynamic strength to be included in the prediction equations. In this paper we present an approach using neural networks that will allow learning and generation of natural human behaviours. We also propose using neural networks for strength prediction because of the flexibility in specifying inputs and outputs and the ability to map non-linear relationships.

Behavior↗
PubMed1996

Innovative perspectives in youth health care.

A dedicated youth health service in an 'adolescent friendly' environment can provide a needed alternative to mainstream general practice for the large sub group of adolescents who require confidential management of their sexual health and psychological needs. Such a service has been operating in Melton, Victoria, since November 1993 under the name of the Backdoor Youth-Health Service.

Adolescent↗
PubMed1996

Occupational exposure to permethrin during its use as a public hygiene insecticide.

Permethrin is an active ingredient found in many public hygiene insecticide products and exposure to it was assessed in a survey of 45 professional users. The exposures measured were over a wide range, with more than a 100-fold difference between average levels and the highest levels. Dermal contamination was evident on 93% of the operators, the highest contamination resulting from the use of leaking application equipment, demonstrating that proper maintenance of equipment is vital. Where the insecticide was applied at ground level most contamination was on the legs, indicating the importance of appropriate footwear. Contamination of the hands occurred despite the use of protective gloves, higher levels of contamination occurring when liquids were used. Dermal contamination was not always the principle route of exposure, and high airborne concentrations were linked with use in confined areas. Airborne concentrations were also associated with the physical form of the product used and the treatment method. To help in assessing the effectiveness of protective clothing and control measures, biological monitoring was carried out. Monitoring of metabolites in urine showed that systemic uptake occurred but evidence from toxicological studies indicates that the levels found were well below those considered to cause harm.

Environmental Monitoring↗
PubMed1996

Granulocyte-macrophage colony-stimulating factor (GM-CSF) priming of high-dose etoposide and cyclophosphamide: a pilot trial.

Given the limitations of bone marrow transplantation (BMT), alternative approaches to deliver dose-intensive regimens without stem cell support are needed. Administration of hematopoietic growth factors before high-dose chemotherapy (priming) may reduce myelosuppression directly, delaying the onset of neutropenia by expanding the mature neutrophil compartment, and shortening the duration of neutropenia by expanding progenitor cell mass. Priming may also render progenitor populations mitotically quiescent after growth factors are withdrawn, thereby making them less sensitive to the cytotoxic effects of chemotherapy. It is also possible, however, that growth factor priming may worsen aplasia when used with dose-intensive regimens by either depleting early progenitor pools or recruiting progenitor populations into cycle. To determine the safety and hematopoietic efficacy of growth factor priming, 13 patients with hematologic malignancy or breast cancer were treated with granulocyte-macrophage colony-stimulating factor (GM-CSF) (250 micrograms/m2 twice daily subcutaneously) until the white blood cell (WBC) count reached either a plateau or 100,000 cells/microL. Forty-eight hours after the last dose of GM-CSF, chemotherapy was begun using high-dose etoposide and cyclophosphamide. All patients received GM-CSF after chemotherapy. Two patients were withdrawn during GM-CSF priming because they developed urticarial rashes. The maximum median increases in WBC and absolute neutrophil count (ANC) during GM-CSF priming were 7.1- and 4.4-fold, respectively. Only one patient achieved the original target WBC of 100,000/microL. The kinetics of leukocyte expansion were slow; a median of 13 days was needed to reach the maximum WBC. Furthermore, much of the leukocyte expansion was caused by an increase in eosinophils, which would not be expected to accelerate hematopoietic recovery. GM-CSF priming did not appear to have a significant impact on hematopoietic recovery after high-dose etoposide and cyclophosphamide, as there was no significant difference in 1) recovery to an ANC > 500/microL compared to a historical control group that received no growth factor (median of 29 and 30 days, respectively; p = 0.4), 2) number of days with an ANC < 500/microL (median of 19 and 20 days, respectively; p = 0.11), and 3) number of days to an untransfused platelet count > or = 50,000/microL (median 36 and 32 days, respectively; p = 0.23). The failure of GM-CSF priming may be a result of its modest stimulation of hematopoiesis or the expansion of a committed progenitor cell population that is exquisitely sensitive to this regimen.

Adult↗
PubMed1996

Cisplatin, camptothecin, and taxol sensitivities of cells with p53-associated multidrug resistance.

With the use of clonogenic survival assays, we show that wild-type p53-expressing A2780 human ovarian cell lines transfected with a dominant negative mutant p53 gene (codon 143, valine to alanine) acquired cross-resistance to ionizing radiation, cisplatin, doxorubicin, and 1-beta-D-arabinofuranosylcytosine. However, these mutant p53-transfected cell lines retained sensitivity to taxol and camptothecin. We also show that immature thymocytes from mice with the p53 gene genetically inactivated showed reduced ability to undergo apoptosis after treatment with ionizing radiation and cisplatin compared with wild-type mice. However, taxol-induced apoptosis in thymocytes does not seem to be dependent on p53 status. Camptothecin also induced apoptosis in a p53-independent manner in thymocytes at low doses but in a p53-dependent manner at high doses. These data suggest that taxoids and camptothecin analogs could have activity in tumors that have aberrant p53 function and provide a rationale for the clinical observations of responsiveness of refractory ovarian cancer to these drugs.

Animals↗
PubMed1996

Turnaround time of in-patient discharge letters: a simple system of audit.

This user-friendly audit system, successfully developed and implemented in a district general hospital for use across all clinical specialties, is able to calculate the turnaround time of final discharge letters and as a consequence identify any areas of delay between patients' discharge and the letter being mailed. By serially monitoring both individual consultant and specialty performance, the system can provide valuable information on the discharge letter process to Purchaser and Provider alike. A copy of the audit system together with details of audit design and methodology is available to interested clinicians, managers and audit facilitators.

Communication↗