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Biomedical subjects

J Calhoun

Publications and source records attributed to J Calhoun.

At least 19 recordsLinked to original sources
PubMed2001

Binding personal and peripersonal space: evidence from tactile extinction.

Behavioral and neurophysiological studies suggest that the brain constructs different representations of space. Among these representations are personal and peripersonal space. Personal space refers to the space occupied by our bodies. Peripersonal space refers to the space surrounding our bodies, which can be reached by our limbs. How these two representations are bound to give a unified sense of space in which humans act is not clear. We tested 10 patients with tactile extinction to investigate this issue. Tactile extinction is an attentional disorder in which patients are unaware of being touched on their contralesional limb if they are also touched simultaneously on their ipsilesional limb. We hypothesized that mechanisms that bind personal and peripersonal representations would improve these patients' awareness of being touched on their contralesional limbs. Visual--tactile integration and intentional movements were considered candidate mechanisms. Patients were more likely to be aware of contralesional touch when looking towards their contralesional limb than when looking towards their ipsilesional limb, and when actively moving on tactile probes than when receiving tactile stimuli passively. The improved awareness of being touched on the contralesional limb under these conditions suggests that cross-sensory and sensorimotor integration help bind personal and peripersonal space.

Aged↗
PubMed2000

Orientation bias in unilateral neglect: representational contributions.

Left-neglect patients bisect horizontal lines to the right of true center. Longer lines are bisected further to the right than shorter lines. This line-length effect might be explained by an increase in the rightward bias of attention because longer lines extend further ipsilesionally. Alternatively, neglect patients might be limited in their abilities to internally represent horizontal magnitudes. Patients might orient further rightward with longer lines because these lines have longer representations. If the line-length effect occurs on lines of identical objective length but they are represented differently, then central mechanisms must contribute to the orientation bias. We constructed two types of lines that were perceived by normal subjects as having different lengths, but were of identical extents. Three neglect patients bisected lines perceived as longer, further to the right than lines perceived as shorter. These results demonstrate that relative magnitudes of internal representations contribute to the degree of bias in neglect patients.

Adult↗
PubMed2000

Sensory and response interference by ipsilesional stimuli in tactile extinction.

Extinction is thought to be due to a pathologically limited attentional capacity in which multiple stimuli cannot be processed simultaneously to conscious awareness. Patients with tactile extinction are aware of being touched on a contralesional limb, but seem unaware of similar contralesional touch if touched simultaneously on their ipsilesional limb. The ipsilesional stimulus interferes and competes with the processing of the contralesional stimulus. Most theorists assume that the ipsilesional stimulus affects the sensory processing of the contralesional stimulus, although the precise functional level at which this interference occurs is not clear. We report a series of experiments using signal detection analyses to investigate tactile extinction in one patient (DC). These analyses revealed that ipsilesional stimuli, in addition to interfering with processing of contralateral sensations, also interfere with verbal reports of those sensations. This influence on responses suggests that interference in tactile extinction can occur at a post-perceptual level, further 'downstream' than previously thought.

Aged↗
PubMed2000

Weighing the evidence for cross over in neglect.

When patients with left-sided neglect are asked to bisect horizontal lines, they tend to place their marks to the right of the line's objective mid-point. However, when asked to bisect short lines they are either more accurate or paradoxically cross over and place their marks to the left of the objective mid-point. Previous explanations of the cross over phenomenon have considered specific aberrations of spatial attention. However, these explanations make no predictions about judgments of non-spatial stimuli. Two patients with right brain damage were asked to judge weights placed on both hands simultaneously. They were biased in reporting weights on the right as being heavier than those on the left. This rightward bias changed with lighter pairs of weights presented in the context of equal reference weights. In one patient the directional bias was eliminated and in the other the bias was reversed so that she was more likely to report the left weight as heavier than the right. These data suggest that a phenomenon analogous to cross over in line bisections also occurs with judgments of non-spatial stimuli. Representations of stimuli appear to be influenced by features of the stimuli encountered on-line and by memory traces of similar stimuli encountered previously. With an attentional deficit, memory traces influence the magnitude of the representation derived on-line disproportionately.

Aged↗
PubMed2000

The art and science of chart review.

BACKGROUND: Explicit chart review was an integral part of an ongoing national cooperative project, "Using Achievable Benchmarks of Care to Improve Quality of Care for Outpatients with Depression," conducted by a large managed care organization (MCO) and an academic medical center. Many investigators overlook the complexities involved in obtaining high-quality data. Given a scarcity of advice in the quality improvement (QI) literature on how to conduct chart review, the process of chart review was examined and specific techniques for improving data quality were proposed. METHODS: The abstraction tool was developed and tested in a prepilot phase; perhaps the greatest problem detected was abstractor assumption and interpretation. The need for a clear distinction between symptoms of depression or anxiety and physician diagnosis of major depression or anxiety disorder also became apparent. In designing the variables for the chart review module, four key aspects were considered: classification, format, definition, and presentation. For example, issues in format include use of free-text versus numeric variables, categoric variables, and medication variables (which can be especially challenging for abstraction projects). Quantitative measures of reliability and validity were used to improve and maintain the quality of chart review data. Measuring reliability and validity offers assistance with development of the chart review tool, continuous maintenance of data quality throughout the production phase of chart review, and final documentation of data quality. For projects that require ongoing abstraction of large numbers of clinical records, data quality may be monitored with control charts and the principles of statistical process control. RESULTS: The chart review module, which contained 140 variables, was built using MedQuest software, a suite of tools designed for customized data collection. The overall interrater reliability increased from 80% in the prepilot phase to greater than 96% in the final phase (which included three abstractors and 465 unique charts). The mean time per chart was calculated for each abstractor, and the maximum value was 13.7 +/- 13 minutes. CONCLUSIONS: In general, chart review is more difficult than it appears on the surface. It is also project specific, making a "cookbook" approach difficult. Many factors, such as imprecisely worded research questions, vague specification of variables, poorly designed abstraction tools, inappropriate interpretation by abstractors, and poor or missing recording of data in the chart, may compromise data quality.

Data Collection↗
PubMed2000

Globalization of U.S. health care services: assessment and implementation.

Globalization has become a commonly used term to describe the manner in which organizations in many industries have spread their operations and management to foreign countries. As the trend toward a global economy progresses, more and more industries, including health care, are looking to capitalize on its possible benefits. This article examines globalization in other industries and applies the tools used elsewhere to U.S. health care organizations.

Decision Making↗
PubMed1999

Crossmodal and sensorimotor integration in tactile awareness.

We investigated tactile awareness in three patients with tactile extinction of stimuli located on contralesional somatotopic space. Contralesional tactile awareness was enhanced when they gazed to the left and when they moved their limbs. We suggest that personal somatotopic and peripersonal space are integrated by polymodal and sensorimotor links, which allow us to be aware of and act effectively on stimuli in space.

Aged↗
PubMed1999

Oral rifampin plus azithromycin or clarithromycin to treat osteomyelitis in rabbits.

A rabbit model for Staphylococcus aureus osteomyelitis was used to compare 28-day combination antibiotic therapy using oral rifampin (40 mg/kg, twice daily) plus oral azithromycin (50 mg/kg, once per day), oral clarithromycin (80 mg/kg, twice daily), or parenteral nafcillin (30 mg/kg, four times daily). The left tibial metaphysis of New Zealand White rabbits was infected with Staphylococcus aureus. Grades 3 to 4 osteomyelitis (according to the Cierny-Mader classification system) development in the rabbits was confirmed radiographically. After antibiotic therapy regimens of 28 days, all tibias from controls that were infected but left untreated (n = 10) revealed positive cultures for Staphylococcus aureus at a mean concentration of 2.8 x 10(4) colony forming units/g bone. The rifampin plus clarithromycin (n = 15) and rifampin plus azithromycin (n = 15) groups showed significantly lower percentages of positive Staphylococcus aureus infection (20% and 13.3%, respectively) and bacterial concentrations (3.5 x 10(1) and 1.75 x 10(1) colony forming units/g bone, respectively). The osteomyelitic tibias of the nafcillin plus rifampin treated group (n = 7) showed no detectable Staphylococcus aureus infection (significantly lower than controls). The differences observed for bone bacterial concentrations and sterilization percentages between the antibiotic treated groups were not statistically significant. Although fluoroquinolones (including ofloxacin and ciprofloxacin) are the agents usually prescribed with rifampin, increasing resistance has been observed. Although macrolides traditionally are not used in the treatment of osteomyelitis, the results of this study indicate that azithromycin and clarithromycin may be attractive partners for rifampin for the treatment of Staphylococcus aureus osteomyelitis in humans.

Administration, Oral↗
PubMed1999

Antimicrobial treatment of chronic osteomyelitis.

Chronic osteomyelitis has been a difficult problem for patients and the treating physicians. Appropriate antibiotic therapy is necessary to arrest osteomyelitis along with adequate surgical therapy. Factors involved in choosing the appropriate antibiotic(s) include infection type, infecting organism, sensitivity results, host factors, and antibiotic characteristics. Initially, antibiotics are chosen on the basis of the organisms that are suspected to be causing the infection. Once the infecting organism(s) is isolated and sensitivities are established, the initial antibiotic(s) may be modified. In selecting specific antibiotics for the treatment of osteomyelitis, the type of infection, current hospital sensitivity resistance patterns, and the risk of adverse reactions must be strongly appraised. Antibiotic classes used in the treatment of osteomyelitis include penicillins, beta-lactamase inhibitors, cephalosporins, other beta-lactams (aztreonam and imipenem), vancomycin, clindamycin, rifampin, aminoglycosides, fluoroquinolones, trimethoprim-sulfamethoxazole, metronidazole, and new investigational agents including teicoplanin, quinupristin/dalfopristin, and oxazolidinones. Traditional treatments have used operative procedures followed by 4 to 6 weeks of parenteral antibiotics. Adjunctive therapy for treating chronic osteomyelitis may be achieved by using beads, spacers, or coated implants to deliver local antibiotic therapy and/or by using hyperbaric oxygen therapy (once per day for 90-120 minutes at two to three atmospheres at 100% oxygen).

Anti-Infective Agents↗
PubMed1997

In vitro evaluation of antibiotic diffusion from antibiotic-impregnated biodegradable beads and polymethylmethacrylate beads.

Antibiotic-impregnated beads are used in the dead bone space following debridement surgery to deliver local, high concentrations of antibiotics. Polymethylmethacrylate (PMMA), 2,000-molecular-weight (MW) polylactic acid (PLA), Poly(DL-lactide)-coglycolide (PL:CG; 90:10, 80:20, and 70:30), and the combination 2,000-MW PLA-70:20 PL:CG were individually mixed with clindamycin, tobramycin, or vancomycin. Beads were placed in 1 ml of phosphate-buffered saline (PBS) and incubated at 37 degrees C. The PBS was changed daily, and the removed PBS samples were stored at -70 degrees C until the antibiotic in each sample was determined by microbiological disk diffusion assay. Nondissolving PMMA beads with tobramycin and clindamycin had concentrations well above breakpoint sensitivity concentrations (i.e., the antibiotic concentrations at the transition point between bacterial killing and resistance to the antibiotic) for more than 90 days, but vancomycin concentrations dropped by day 12. ALl PLA, PL:CG, and the 2,000-MW PLA-70:30 PL:CG biodegradable beads release high concentrations of all the antibiotics in vitro for the period of time needed to treat bone infections (i.e., 4 to 8 weeks). Antibiotic-loaded PLA and PL:CG beads have the advantage of better antibiotic elution and the ability to biodegradable (thereby averting the need for secondary surgery for bead removal) compared to the PMMA beads presently used in the clinical setting.

Anti-Bacterial Agents↗
PubMed1997

A practical guide to the diagnosis and management of bone and joint infections.

Infectious arthritis arises from haematogenous spread of organisms through the synovial membrane or from the direct extension of a contiguous infection. The diagnosis rests on the isolation of the pathogen(s) from joint fluid obtained by aspiration or from debridement. Synovial fluid analysis and Gram stains provide clues to the aetiology. The treatment of septic arthritis includes appropriate antimicrobial therapy and joint drainage. Bone infections are currently classified by the Waldvogel or Cierny-Mader classification. Cierny-Mader staging allows stratification and development of comprehensive treatment guidelines for each stage. Osteomyelitis therapy emphasises early diagnosis and aggressive treatment. Radiographs and bone cultures are the mainstays of diagnosis. Radionuclide scans, computerised tomography or magnetic resonance imaging may be obtained when the diagnosis of osteomyelitis is equivocal or to help gauge the extent of the infection. Medical therapy includes improving any host deficiencies, initial antibiotic selection and antibiotic modification based on culture results. Surgical treatment involves debridement of necrotic bone and tissue, obtaining appropriate cultures, managing dead space and, when necessary, obtaining bone stability.

Arthritis, Infectious↗
PubMed1994

Long-bone osteomyelitis diagnosis and management.

The pathogen may proliferate years after seemingly successful treatment. The authors describe a classification system to evaluate both the disease and the patient's capacity to undergo the rigors of therapy. Two cases illustrate the clinical issues.

Adolescent↗
PubMed1993

Diagnoses and staging. Osteomyelitis and prosthetic joint infections.

The diagnoses of osteomyelitis and prosthetic joint infections are usually made on the basis of clinical, laboratory, and radiographic examination. The diagnostic studies presently employed to diagnosis and assess osteomyelitis and prosthetic joint infections are described. A universally applied classification system for stratifying osteomyelitis and prosthetic joint infection would provide a framework for the evaluation of medical and surgical treatment efficacy. Such a system would enable treatment results to be compared among institutions. Staging systems currently being used are described.

Blood Sedimentation↗
PubMed1993

Antimicrobial treatment of osteomyelitis.

Parenteral antibiotic therapy remains the mainstay of antimicrobial therapy for osteomyelitis. In acute cases, empirical treatment may be used initially, but antibiotic selection should ideally be based on deep aspiration or bone cultures with corresponding in vitro sensitivity testing. The drug exhibiting the highest bacteriocidal activity with the least toxicity and lowest cost should be chosen. Antibiotic treatment will not substitute for surgical debridement of infected devitalized bone. The length of treatment with parenteral therapy remains controversial. The six-week benchmark, which was determined largely by experience with childhood hematogenous osteomyelitis, may not be applicable to contiguous focus osteomyelitis after trauma in adults. The goal of surgical treatment is to convert an infection with dead bone to a situation with well-vascularized tissues that are readily penetrated by blood-borne antibiotics, making prolonged drug treatment unnecessary.

Aminoglycosides↗
PubMed1993

A comparison of gentamicin-impregnated polymethylmethacrylate bead implantation to conventional parenteral antibiotic therapy in infected total hip and knee arthroplasty.

A multicenter study of infected total knee and total hip arthroplasties was conducted from 1985 until 1990. Twenty-eight patients (22 total hip arthroplasties and six total knee arthroplasties) who had periprosthetic infections were treated according to a prospective, randomized protocol. After initial debridement for their infections, patients were randomized into one of the two following groups: Group I, debridement and the implantation of gentamicin-polymethylmethacrylate (PMMA) beads; and Group 2, debridement and conventional parenteral systemic antibiotic therapy. After initial treatment, the patients were then scheduled for a delayed reconstruction total joint arthroplasty. Of the 28 patients, 25 subsequently had delayed total arthroplasty, and if acrylic bone cement was used for fixation at the time of reimplantation, antibiotics were not added to the cement. The average follow-up period was three years (range, six months to 5.6 years). Infection recurred in two patients treated by debridement and the implantation of gentamicin-PMMA beads (15%) and in four patients treated with debridement and conventional systemic antibiotic therapy (30%). All recurrences occurred in patients who had infected total hip arthroplasties; none occurred in patients with total knee arthroplasties. The conditions that were common in patients with recurrent infection were (1) multiple previous surgeries, (2) host compromise and malnutrition, (3) extensive infection, and (4) inadequate debridement. The recurrence of infection was not statistically significantly more common in either treatment group. The outcome of treatment in patients with infected total joint arthroplasties using debridement, gentamicin-PMMA bead implantation,and a two-stage delayed reconstruction was similar to that of patients treated with debridement combined with conventional parenteral systemic arthroplasty and two-stage reconstruction.

Adult↗
PubMed1992

In vitro and in vivo evaluation of antibiotic diffusion from antibiotic-impregnated polymethylmethacrylate beads.

The elution of antibiotics from antibiotic-impregnated polymethylmethacrylate (PMMA) beads was measured in mongrel dogs. The antibiotics, used in mixture with Simplex cement, included cefazolin (Ancef; 4.5 g/40 g cement powder), ciprofloxacin (Cipro; 6 g/40 g powder), clindamycin (Cleocin; 6 g/40 g powder), ticarcillin (Ticar; 12 g/40 g powder), tobramycin (Nebcin; 9.8 g/40 g powder), and vancomycin (Vancocin; 4 g/40 g powder). After a pneumatic drill was used to dredge a trough in the tibia, five beads were implanted. During the next 28 days, seroma samples and serum samples were taken for antibiotic measurements. On Day 28, the dogs were killed, beads removed, and the seroma, serum, bone, and granulation tissue sampled. The results of the study showed that clindamycin, vancomycin, and tobramycin exhibited good elution characteristics and had consistently high levels in bone and granulation tissue.

Animals↗