The effects of unilateral and multifocal lesions on the WAIS-R: a factor analytic study of stroke patients.

An exploratory maximum likelihood factor analysis of the inter-correlations among the 11 subtests of the WAIS-R was undertaken for 167 patients who had a primary diagnoses of cerebrovascular accident (right hemisphere, n = 79; left hemisphere, n = 55; diffuse or multifocal, n = 33). On the WAIS-R, this sample performed below normative standards (average scaled score = 7.1), but demonstrated a pattern of variability among subtests similar to the normative groups. Interestingly, VIQ-PIQ discrepancy analyses revealed V > P profiles for patients with lesions in either or both hemispheres. The best fit for the WAIS-R matrix was an oblique two-factor model comprised of the Verbal and Performance subtests. This factor solution, which was moderately correlated (.52), accounted for 58.8% of the total variance. The stability of a two-factor structure in this neurologic impaired population suggests that the WAIS-R is a robust measure, even when used within such a rehabilitation population. Only two of the eleven subtests (i.e., Comprehension and Picture Arrangement), however, were related to lesion site. Rehabilitation settings may need to rely more on neuropsychological procedures that measure the more "fluid" areas of neurocognitive ability, in contrast to the WAIS-R which appears less sensitive to the neurological impairment associated with stroke.     

Toward a research agenda for competency-based medical education

Competency-based medical education (CBME) is both an educational philosophy and an approach to educational design. CBME has already had a broad impact on medical schools, residency programs, and continuing professional development in health professions around the world. As the CBME movement evolves and CBME programs are implemented, a wide range of emerging research questions will warrant scholarly examination. In this paper, we describe a proposed CBME research agenda developed by the International CBME Collaborators. The resulting framework includes questions about the meaning of key concepts of CBME and their implications for learners, faculty members, and institutional structures. Other research questions relate to the learning process, the meaning of entrustment decisions, fundamental measurement issues, and the nature and definition of standards. The exploration of these questions will help to solidify the theoretical foundation of CBME, but many issues related to implementation also need to be addressed. These pertain to, among other things, nurturing independent learning, assembling and using assessment results to make decisions about competence, structuring feedback, supporting remediation, and how best to evaluate the longer-term outcomes of CBME. High-quality research on these questions will require rigorous outcome measures with strong validity evidence. The complexity of CBME necessitates theoretical and methodological diversity. It also requires multi-institutional studies that examine effects at multiple levels, from the learner to the team, the institution, and the health care system. Such a framework of research questions can guide and facilitate scholarly discourse on the theoretical and practical body of knowledge related to competency-based health professions education.     

Strength of cement-metal interfaces in fatigue: comparison of smooth, porous and precoated specimens

Radiographic follow-up studies of cemented total hip arthroplasty have shown that failure of the cement-metal interface of the femoral component is as high as 25% at 10 years. Recent analyses of clinically successful cemented femoral components obtained in toto with the surrounding cement and femurs after many years of in-vivo service have suggested that the mechanism of the initiation of failure of fixation of cemented femoral components is debonding at the cement-metal interface. Since this critical interface is subjected primarily to cyclic loading, the evaluation of different surface preparations should be studied in fatigue, not static testing. In the current study, several contemporary methods for increasing the strength of the cement-metal interface were evaluated by testing the interfacial fatigue pushout strength under varying conditions of cyclic loading. The effect of a smooth 'implant finish' surface, a surface coated with polymethylmethacrylate (PMMA precoated surface), a combination of a textured surface with PMMA precoat, and a porous titanium mesh coated surface were examined. Precoating the metal with a thin film of PMMA significantly increased the number of compressive fatigue loading cycles required for failure of the cement-metal interface under cyclic loading compared to a smooth, uncoated surface. Adding indentations to the surface and then precoating with PMMA further significantly increased the fatigue life of the cement-metal interface. The strongest interface in fatigue was the titanium fibermesh-cement interface.     

Molecular aspects of water transport

Due to its fundamental importance, the movement of water across cell membranes has been an active area of research for more than 100 years. This subject is central to consideration of normal water metabolism by terrestrial animals, as well as derangements in overall water balance that are frequently encountered by nephrologists in the care of their patients. The objective of this review is to discuss the most basic aspects of cell membrane water permeability and provide a framework for these data in the context of the care of pediatric patients with renal disease. While the water permeability of most cell membranes can be accounted for by the diffusion of water across the lipid bilayer, other cells, including the red blood cell and certain epithelial cells that line the proximal and collecting tubules of the kidney and the urinary bladder of amphibians, possess specialized water channels. Water channels are composed of specialized proteins that create aqueous pores across cell membrane. Currently, there are active research efforts to isolate and characterize water channel proteins from these cell types. Data concerning the distribution, permeability and function of these various water channels will greatly enhance our knowledge of how water is transported across cell membranes.     

Identification of aortic thrombus by magnetic resonance imaging

The unique properties of magnetic resonance imaging result in the potential to differentiate various components of the diseased arterial wall. In this article four cases are presented in which magnetic resonance imaging showed mural aortic thrombus and its anatomic relationship to the visceral and renal arteries. Once thrombus is identified and localized specific operative strategies can be undertaken to prevent recurrent embolic events and/or avoid perioperative thromboembolic complications.     

A retrospective review of basilic and cephalic vein-based fistulas

This study compares outcomes of basilic and cephalic vein fistulas for hemodialysis. A retrospective review of arteriovenous fistulas in a university hospital system was performed using charts and hemodialysis records. Patency and demographic data were assessed with life table analysis. One hundred fifty-six patients (88 males; 68 females) underwent creation of 172 autogenous fistulas (mean age 61 years; mean follow-up 78 weeks). There were 101 basilic vein transpositions and 71 cephalic vein fistulas. Primary patency did not differ significantly, while assisted primary patency was significantly better for basilic vein fistulas at one year (73% versus 53%: P = 0.024). Secondary patency was significantly better for basilic fistulas through three years (58% versus 52%; P = 0.027). Primary failure (thrombosis before access or failed maturation) was significantly higher for cephalic than basilic fistulas (28% versus 13%; P = 0.01). Maturation time, usage time and complications were not significantly significant. Thirty-three (33%) basilic vein-based fistulas and 12 (17%) cephalic vein fistulas required revision during follow-up. Basilic vein-based fistulas perform as well as or better than cephalic vein-based fistulas in terms of patency, maturation time, and usage time and complication rates, though requiring more re-interventions.     

Successful aortic surgery after renal transplantation without protection of the transplanted kidney

When renal transplant recipients undergo aortic surgery, blood supply to the renal graft is interrupted while the aorta is clamped. Several innovative ways of using shunts have been described to preserve blood flow to the transplanted kidney during such surgery on the assumption that temporary warm ischemia of the renal transplant is poorly tolerated. We have performed aortic surgery in four renal transplant recipients without the use of any form of graft protection. One patient underwent urgent operation to treat an expanding aortic aneurysm and the other three had elective surgery for aortoiliac occlusive disease. Ischemic times ranged from 30 to 45 minutes. Two of the four patients had a temporary rise in serum creatinine levels. No patient required hemodialysis. We conclude that in selected renal transplant recipients, aortic surgery can be safely undertaken without graft protection.