Search PubMed⌕ Search

Biomedical subjects

D Norman

Publications and source records attributed to D Norman.

At least 73 records · Page 4Linked to original sources
PubMed1996

Gastrointestinal complications after orthotopic cardiac transplantation.

OBJECTIVE AND METHODS: A retrospective chart review was performed on all patients undergoing orthotopic cardiac allograft transplant at Oregon Health Sciences University. Our purpose was to evaluate the incidence of gastrointestinal complications in these patients, and to assess the effect of immunosuppression. RESULTS: From December, 1985, to June, 1994, 240 recipients underwent 250 orthotopic cardiac allograft transplants at Oregon Health Sciences University with a 30 day mortality of 15 patients (6.3 +/- 3.0%). Of the 225 operative survivors, the follow-up ranges from 1.0 month to 8.8 years with a mean of 39.9 +/- 1.9 months. In our population of late survivors, 21 recipients (9.3%) have had gastrointestinal complications (GIC). Hepatobiliary (29%), peptic ulcer (14%), and pancreatic (14%) complications were the most prevalent. Surgical intervention was required in 19 patients (90%). Twelve procedures (63%) were either emergently or urgently performed, and seven procedures (37%) carried out electively. Operative mortality was 33% in those patients with an emergent or urgent intervention. There was no operative mortality among those who had an elective procedure. CONCLUSION: Maintenance prednisone dose was higher in patients with GIC than in those patients without GIC, 16.1 +/- 2.5 mg versus 7.3 +/- 0.2 mg (P = 0.001), respectively. However, immunosuppression therapy for rejection episodes (i.e., Solumedrol megapulse or OKT3 therapy) was not related to an increased incidence of GIC. We present a review of our 21 cardiac transplant recipients to emphasize the potential for severe GIC and their corresponding perioperative morbidity and mortality.

Adolescent↗
PubMed1996

Alzheimer disease and subcortical ischemic vascular dementia: evaluation by combining MR imaging segmentation and H-1 MR spectroscopic imaging.

PURPOSE: To determine the association between H-1 magnetic resonance (MR) spectroscopic imaging and MR imaging differences in subjects with Alzheimer disease (AD) or subcortical ischemic vascular dementia (SIVD) versus control subjects and if both studies combined enable discrimination of AD from control subjects better than either study alone. MATERIALS AND METHODS: Measures were obtained in nine AD, eight SIVD, and 11 control subjects with MR imaging segmentation software. RESULTS: Statistically significantly lower N-acetylaspartate/choline-containing metabolites (Cho) and higher Cho/creatine-containing metabolites in posterior mesial gray matter in AD versus control subjects were independent of MR imagining differences. Combined measures allowed correct classification of AD and control subjects, but none of the MR measures allowed accurate discrimination between AD and SIVD subjects. CONCLUSION: Between-group differences in tissue-type contributions to H-1 MR spectroscopic imaging voxels must be accounted for when reporting H-1 MR spectroscopic imaging data in AD, SIVD, and control subjects. Combined studies allowed more accurate discrimination between AD and control subjects than either study alone.

Aged↗
PubMed1996

Reduced caliber of the internal carotid artery: a normal finding with ipsilateral absence or hypoplasia of the A1 segment.

PURPOSE: To determine whether a relationship exists between normal variations in anatomy of the circle of Willis and the size of the internal carotid arteries (ICA). METHODS: MR angiograms and axial MR images of the brains of 104 patients were reviewed. Included were 10 patients with unilateral absence of the A1 segment of the anterior cerebral artery, 10 with hypoplasia of one A1 segment, 28 with asymmetric A1 segments, nine with isolated unilateral fetal origin of the posterior cerebral artery, and 47 with balanced circulation. RESULTS: The mean ICA diameter measurement for the total population was 4.62 +/- 0.68 mm. In patients with absent A1, the mean ipsilateral and contralateral ICA diameters were 3.63 +/- 0.41 mm and 5.25 +/- 0.52 mm, respectively. The mean percentages of the difference between the diameters of the right and left ICA (31% in the group with absent A1 and 21% in the group with hypoplastic A1) varied significantly from the differences in the ICA diameters among the rest of the population. The diameter differences produced by other common variations (unilateral small A1 segment or fetal origin of the posterior cerebral artery) did not differ significantly from those of the 47 patients with balanced intracranial circulation. CONCLUSIONS: There is an association of unilaterally absent or hypoplastic A1 segments of the anterior cerebral artery with ipsilateral decrease in ICA caliber, and this can be seen on MR angiograms.

Adolescent↗
PubMed1995

A brief review of the history and use of the daresbury ;miyake' monochromator for surface science.

This paper celebrates the 21st anniversary of the plane-grating grazing-incidence monochromator, designed at Daresbury in 1974 and in almost continuous operation ever since. The order-sorting principles [Miyake, Kato & Yamashita (1969). Sci. Light (Tokyo), 18, 39-56] are described, along with the detail of the instrument's design, followed by the history of its use on three synchrotron radiation sources (NINA, TANTALUS and SRS). A selection of scientific highlights at the SRS is given, taken from some of the experimental programmes in which the author was involved, concentrating on tunable photon-energy photoemission studies of metallic alloys. Finally, the future prospects for vacuum UV spectroscopy for surface science are briefly discussed.

Journal Article↗
PubMed1995

1H and 31P magnetic resonance spectroscopic imaging of white matter signal hyperintensity areas in elderly subjects.

White matter signal hyperintensities (WMSH) are commonly seen on MRI of elderly subjects. The purpose of this study was to characterize metabolic changes in the white matter of elderly subjects with extensive WMSH. We used water-suppressed proton (1H) magnetic resonance spectroscopic imaging (MRSI) to compare six subjects with extensive WMSH with eight age-matched elderly subjects with minimal or absent WMSH, and phosphorus (31P) MRSI to compare nine subjects with extensive WMSH and seven age-matched elderly subjects without extensive WMSH. Relative to region-matched tissue in elderly controls, extensive WMSH were associated with increased signal from choline-containing metabolites, no significant change of signal from N-acetylaspartate, and a trend to a decreased phosphomonoester (PME) resonance. These findings suggest that WMSH may be associated with an alteration of brain myclin phospholipids in the absence of axonal damage. There were no differences in energy phosphates, consistent with lack of ongoing brain ischemia. Within the group with extensive WMSH, PME resonance measures were significantly lower in WMSH than in contralateral normal-appearing white matter. These results provide information on pathophysiology of WMSH and a basis for comparison with WMSH in Alzheimer's disease, vascular dementia, multiple sclerosis, and other diseases.

Aged↗
PubMed1995

Efficacy of unanesthetized spiral computed tomography scanning in initial evaluation of childhood leukocoria.

PURPOSE: To evaluate the use of spiral/helical computed tomography (CT) in the preoperative evaluation of pediatric leukocoria. METHODS: A total of 34 patient charts and imaging studies were reviewed from a consecutive series of children referred with the diagnosis of presumed retinoblastoma. Of these patients, 31 had a confirmed diagnosis of retinoblastoma. Three patients had simulating lesions, including one patient with persistent hyperplastic primary vitreous and two with Coats disease. RESULTS: In all patients, a diagnosis of intraocular retinoblastoma could be established or excluded at the same clinical level by spiral CT as by conventional CT. Spiral CT of the eye, orbit, and midline structures was performed without a requirement for patient anesthesia. This technique resulted in a reduced volume of contrast material required for evaluation of the central nervous system and a small decrease in total radiation exposure. There was an attendant reduction in the amount of monitoring equipment required and the necessity for attending anesthesia staff. CONCLUSIONS: The primary advantage of spiral CT is reduced anesthesia risk in small children. In addition, this technique provides necessary clinical information with a reduction in image acquisition time, monitoring equipment, and monitoring staff.

Anesthesia↗
PubMed1995

Effects of family history and comorbidity on the neuropsychological performance of children with ADHD: preliminary findings.

OBJECTIVE: Because ADHD is heterogeneous with respect to psychiatric comorbidity, familiality, and learning disabilities, it was hypothesized that such features might influence the severity and pattern of neuropsychological function in ADHD. METHOD: Subjects were 9- to 20-year-old males with DSM-III-R ADHD (n = 65) and normal controls (n = 45). Information on neuropsychological performance was obtained in a standardized manner, blind to the proband's clinical status. RESULTS: ADHD probands were significantly impaired on neuropsychological functions compared with controls irrespective of composite psychiatric comorbidity status, and those with a family history of ADHD were most impaired. ADHD probands with learning disabilities showed a pattern suggestive of reduced motor dominance and extremely slow reading speed. CONCLUSIONS: These results indicate that neuropsychological performance in ADHD is significantly affected by familial status and presence of learning disabilities. The similarity of findings between ADHD children with and without comorbid psychiatric disorders suggests that the neuropsychological impairments in our sample were associated with ADHD. These findings raise the possibility of alterations of cerebral dominance and of frontal networks in ADHD. Further research is needed to replicate these findings in larger samples, to clarify the role of specific comorbid psychiatric disorders, and to assess directly cerebral functioning in subjects with ADHD.

Adolescent↗
PubMed1995

Performance of children with ADHD on the Rey-Osterrieth complex figure: a pilot neuropsychological study.

This study evaluates the performance of boys with Attention Deficit Hyperactivity Disorder (ADHD) on the Rey-Osterrieth Complex Figure (ROCF) taking into consideration familiality and comorbid psychiatric and learning disorders (LD). Sixty-five children with ADHD performed at developmentally lower levels of Copy Organization and Recall Style than did 45 controls. ADHD children with LD scored significantly lower on Copy Organization than did ADHD children without LD, whereas psychiatric comorbidity and familiality had no effect. These results suggest that a developmental analysis of the ROCF identifies organizational difficulties associated with ADHD and that these impairments cannot simply be attributed to comorbidities associated with ADHD.

Adolescent↗
PubMed1995

H-1 MR spectroscopic imaging of white matter signal hyperintensities: Alzheimer disease and ischemic vascular dementia.

PURPOSE: To investigate the association of white matter signal hyperintensities (WMSHs) with changes in hydrogen-1 metabolites. MATERIALS AND METHODS: T2-weighted magnetic resonance (MR) imaging and H-1 MR spectroscopic imaging were performed in 21 elderly control subjects without or with minimal WMSHs, eight elderly subjects with substantial WMSHs, 11 probable Alzheimer disease patients with WMSHs, and eight ischemic vascular dementia (IVD) patients with WMSHs. N-acetylaspartate (NAA), choline-containing metabolites (Cho), and creatine-containing metabolites (Cr) were analyzed. RESULTS: Differences in regional metabolite levels were found within the supraventricular brain of elderly control subjects. In Alzheimer disease patients, extensive WMSHs showed a lower percentage of NAA and a higher percentage of Cho compared with contralateral normal-appearing white matter (NAWM); in IVD patients, extensive and large WMSHs were associated with a higher percentage of Cho and a lower percentage of Cr compared with contralateral NAWM. CONCLUSION: Regional metabolite variation and the presence of WMSHs are important covariants that must be accounted for in analysis of MR spectroscopic data.

Aged↗
PubMed1995

[External fixation of the lower limb in children].

18 children (13 boys, 5 girls) with displaced fractures of the femur (13 cases) and tibia (5) after road accidents were treated with Wagner external fixation. 5 fractures were open and 13 closed. 9 also had head injury and were unconscious. In 3 fractures the popliteal artery was torn, requiring arterial reconstruction. 15 were examined an average of 2.3 years after injury and there was full range of motion in 13. In 2 after severe injury, range of motion was 80% of normal. There was refracture after removal of external fixation in 1. We conclude that external fixation is stable and has minimal complications. We recommend it for children with comminuted fractures, multiple trauma and those in intensive care.

Accidents, Traffic↗
PubMed1994

Axonal injury and membrane alterations in Alzheimer's disease suggested by in vivo proton magnetic resonance spectroscopic imaging.

We used spin-echo magnetic resonance imaging and proton magnetic resonance spectroscopic imaging in 8 patients with probable Alzheimer's disease and in 10 age-matched elderly control subjects to assess the effects of Alzheimer's disease on the brain. On magnetic resonance images the patients showed significant ventricular enlargements relative to the control subjects. We measured the distribution and relative signal intensities of N-acetylaspartate (a putative neuronal marker), of choline residues representing lipid metabolites, and of creatine-containing metabolites in a large section of the centrum semiovale containing white and mesial gray matter. Throughout the white matter of the patients with Alzheimer's disease compared to elderly control subjects, N-acetylaspartate was decreased relative to choline (N-acetylaspartate-choline ratio) and creatine-containing metabolites (N-acetylaspartate-creatine ratio) with no changes in the choline-creatine ratio. The N-acetylaspartate-choline ratio was lower and choline-creatine higher in the mesial gray matter of AD patients relative to elderly controls. The posterior section of the centrum semiovale in the patients showed increased choline-creatine and choline-N-acetylaspartate ratios with the N-acetylaspartate-creatine ratio unchanged between the patients and control subjects. These spectroscopic findings give suggestive evidence of diffuse axonal injury and membrane alterations in gray and white matter of the centrum semiovale in patients with Alzheimer's disease.

Aged↗
PubMed1994

Cardiac allografts from high-risk donors: excellent clinical results.

Rising waiting list mortality and increasing demand for donor organs have led to extension of traditionally accepted criteria for evaluation of cardiac grafts. From December 1985 to June 1992, 188 cardiac grafts were orthotopically transplanted into 178 recipients. Of these grafts, 38.3% (72/188) were defined as high-risk donors. Risk criteria included prolonged cardiopulmonary resuscitation, age greater than 40 years, high inotrope requirements, undersizing by more than 20% body weight, significant wall motion impairment by echocardiography, elevation of myocardial enzyme levels, and cold ischemia time greater than 4 hours. There were no recipient deaths attributable to primary graft failure in the perioperative period. Operative (30-day), 1-year and 5-year survival was 95.5%, 86.1%, and 77.3%, respectively, in the high-risk group compared with 93.7%, 86.0%, and 67.2%, respectively, in the low-risk donor cohort (p = 0.94). Comparison of duration of postoperative inotrope use, intensive care unit stay, total hospital stay, and in-hospital costs revealed no significant trends favoring either group in postoperative morbidity. Among long-term survivors, development of graft coronary disease was noted in 47.1% (24/51) of the high-risk donor group and only 17.4% (12/69) of the remaining group (p = 0.0005). Left ventricular ejection fractions in the high risk donor group were 0.58 +/- 0.01 at 2 years. Review of this series suggests that selective use of apparently compromised cardiac donors is compatible with excellent cardiac function and survival. Higher incidence of graft vasculopathy may cause significant morbidity during late follow-up.

Adolescent↗
PubMed1994

Prospective risk stratification in renal transplant candidates for cardiac death.

In previous studies to predict future cardiac death of patients undergoing evaluation for renal transplantation, noninvasive or invasive testing of all, or nearly all, patients has been used. In an attempt to decrease the cost of cardiac risk assessment, we prospectively used a two-tiered cardiac risk assessment algorithm on 189 consecutive patients referred for renal transplant evaluation. First, patients were stratified by clinical characteristics of age > or = 50 years, history of angina, insulin-dependent diabetes, congestive heart failure, or abnormal electrocardiogram (excluding left ventricular hypertrophy). Patients having none of these risk factors (n = 94) were considered at low risk for cardiac events and underwent no further cardiac evaluation. Patients with one or more of the cardiac risk factors (n = 95) were considered to be in a high-risk group and were required to undergo further evaluation with thallium myocardial scintigraphy. Follow-up of patients was for 46 +/- 16 months. Cardiac mortality was significantly higher in the clinical high-risk group compared with the clinical low-risk group (17% v 1%, respectively; P < 0.001). Further cardiac risk stratification was evident by thallium myocardial scintigraphy. Patients with reversible thallium defects had significantly higher cardiac mortality rates than patients with no thallium defects (23% v 5%, respectively; P < 0.05). Fixed thallium defects also had predictive value for cardiac mortality (29%,; P < 0.05), but deaths in this fixed defect group tended to occur later in the follow-up period. The initial clinical stratification obviated the need for further noninvasive or invasive testing in nearly half of the renal transplant candidates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Aortic valve replacement with pulmonary homografts. Early experience.

The increasing use of the aortic homograft as aortic valve substitute and the limited availability of donor valves prompted us to consider the pulmonary homograft as an alternative substitute for aortic valve replacement. The aim of our study is to compare the ultrastructural and biomechanical properties of pulmonary homograft leaflets with those of their aortic counterpart and to present the early results of using the pulmonary homograft for aortic valve replacement. Light and transmission electron microscopy have shown that pulmonary homograft leaflets are thinner than the aortic with a lesser content of elastic tissue in the ventricularis layer. However there were no substantial differences in the ultrastructure. Uniaxial tensile tests were done on 69 cusps from human pulmonary and aortic valves using an Instron testing machine. The strain at 200 KPa was found to be similar for both pulmonary and aortic leaflets (8.20% +/- 2.87% versus 8.98% +/- 1.90%) cut circumferentially. Radial strips appear to be more extensible in pulmonary leaflets than in aortic (32.6% +/- 7.5% and 28.6% +/- 11.1%, respectively). The ultimate tensile strength for circumferential strips was found to be similar for both aortic and pulmonary valves (1460 +/- 857 kPa versus 1450 +/- 689 kPa), but there was relatively little difference between the radial strips (295 +/- 95 kPa versus 252 +/- 104 kPa). A total of 123 patients whose ages ranged between 13 and 78 years received either fresh antibiotic sterilized or cryopreserved pulmonary homografts for aortic valve replacement. The pulmonary homograft was inserted in place of the patient's diseased aortic valve by using one of two different techniques: freehand in the subcoronary position or as a "short cylinder" inside the aortic root. There was three hospital deaths (2.43%; 70% confidence limits = 1.08% to 4.83%). Cumulative follow-up was 184 patient-years (range 1 to 39 months). All surviving patients have been followed up with serial color flow Doppler echocardiography. There were no late deaths. Actuarial late survival was 97.5% (70% confidence limits = 95.7% to 98.6%) at 3 years. Four patients (2.2%/pt-yr) underwent reoperation because of severe aortic regurgitation (1, 4, 12, and 15 months after the operation) because of technical problems (mismatch in size between the pulmonary homograft and aortic anulus) in three patients and probably because of graft rejection in one patient. At 3 years the actuarial rate of freedom from reoperation was 95.5% (70% confidence limits = 92.7% to 97.3%). Mild aortic regurgitation has been detected in three patients (2.6%). No patients incurred thromboembolic episodes or infective endocarditis.(ABSTRACT TRUNCATED AT 400 WORDS)

Actuarial Analysis↗
PubMed1993

Comparison of the Accu-CulShure system and a swab placed in a B-D Port-a-Cul tube for specimen collection and transport.

We compared the Accu-CulShure guarded specimen collection device and a swab inserted into a B-D Port-a-Cul transport tube in terms of their efficacy under ideal conditions for recovery of bacteria from 10 decubitus ulcer specimens. Cultures yielded 57 aerobes and 21 anaerobes; 76 isolates were recovered with use of Accu-CulShure, and 72 isolates were recovered with use of Port-a-Cul. Both systems were comparable for recovery of organisms in terms of quantitative and qualitative results.

Adult↗