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Biomedical subjects

M J Lysaght

Publications and source records attributed to M J Lysaght.

52 records · Page 3Linked to original sources
PubMed1975

Kinetics of hemodiafiltration. I. In vitro transport characteristics of a hollow-fiber blood ultrafilter.

The transport characteristics of a hollow-fiber blood ultrafilter were studied in vitro to provide an understanding of the factors which control solute removal rate and to permit design of a full-scale clinical device. The dependence of ultrafiltrate flux on transmembrane pressure difference, protein concentration, flow rate, and fiber geometry was correlated in terms of available theoretical analyses. Solute rejection was 1.0 for albumin and decreased to nearly zero for solutes of several thousand molecular weight. An analysis of overall hemodiafilter behavior showed that blood and ultrafiltrate flow rates of 200 ml. per minute can be attained with a device of reasonable size which would provide an inulin whole blood clearance of about 100 ml. per minute.

Blood Proteins↗
PubMedDate not supplied

The case for financial incentives to encourage organ donation.

The existing system of organ procurement has failed in its mission of providing an adequate number of organs for transplantation. The organ shortfall results in diminished life expectancy and quality of life for dialysis patients and in increased mortality for patients with end-stage cardiac disease and liver failure who are unable to obtain transplants. Oft-repeated arguments against sale of human organs do not stand up to careful examination, and seem anachronistic in the context of widespread current acceptance of financial incentives for tissue donation in analogous fields, such as reproductive medicine. This essay advocates the staged introduction of a reward-based system of organ donation, initially for cadaveric harvesting and, possibly, later for living donation. Although imperfect, the proposed approach would represent a significant improvement over the status quo.

Europe↗
PubMedDate not supplied

Demographic scope and economic magnitude of contemporary organ replacement therapies.

This analysis draws upon a variety of sources to provide a tally of the number of patients receiving organ replacement therapies and the costs associated with the provision of such therapies. Constituent data were available from treatment-specific patient registries, peer reviewed reports in scientific literature, business publications, and industry sources. The magnitude and economic scope of the contemporary organ replacement enterprise were found to be much larger than is generally recognized. In the year 2000, the lives of over 20 million patients will be sustained, supported, or significantly improved by functional organ replacement. The impacted population grows at over 10% per year. Worldwide, first year and follow-up costs of organ prosthesis exceeds $300 billion US dollars per year and represents between 7 and 8% of total worldwide health care spending. Remarkably, in the United States, the costs of therapies enabled by organ replacement technology exceed 1% of the Gross Domestic Product. These findings constitute an incontestable tribute to the scientific significance and medical impact of the still nascent field of substitutive medicine. At the same time, the enormous magnitude of resources dedicated to organ replacement raises several issues related to overall cost effectiveness of current modalities and raises challenges and opportunities for future technical developments.

Arthroplasty, Replacement↗
PubMedDate not supplied

Plasma water filtration and lymphatic uptake during peritoneal dialysis.

To clarify further the extent, pathways, and significance of convective transport during peritoneal dialysis, acute transport studies were conducted in which five continuous ambulatory peritoneal dialysis (CAPD) patients underwent 6 hr dialyses (2 L infusate with 2.25% dextrose) on 2 successive days, with multiple sampling of both blood and peritoneal dialysate. Concentrations of permeants (urea, creatinine, uric acid, beta 2 microglobulin, and apolipoprotein A) and a radiolabeled marker (125I-polyvinyl pyrollidone [PVP]) were determined at 20-30 min intervals in dialysate and every 90 min in plasma. Intraperitoneal volumes and lymphatic flows were calculated from rates of dilution and disappearance of 125I-PVP. Intratreatment lymphatic flow rate averaged 76 +/- 15 ml/hr. Although lower than observed in small animal models and reported by some clinical groups, this level of lymphatic drainage was still sufficient to decrease net patient weight loss by approximately 50% and to resorb approximately 15% of metabolites in the peritoneal cavity, independent of molecular weight. Transcapillary ultrafiltration ranged from 7.4 +/- 1.5 ml/min at 10 min into the exchange to 1.3 +/- 1.5 ml/min at 345 min. Reverse ultrafiltration, from the peritoneal cavity back through capillary vasculature to the patient, was not observed in any patient in this study.

Ascitic Fluid↗
PubMedDate not supplied

The influence of dialysis treatment modality on the decline of remaining renal function.

A retrospective investigation was undertaken in which the rate of decline of residual renal function (RRF), estimated from creatinine clearance, was compared in 55 continuous ambulatory peritoneal dialysis (CAPD) and 57 hemodialysis (HD) patients for whom a minimum of four (mean of 7.6) well-spaced historic measurements of residual clearance were available. Because of the intrinsic variability that attends such data, specialized nonlinear, growth curve statistical methods were employed. Residual function was found to decline exponentially after the onset of therapy in both cohorts. The rate of decline in the HD group was twice that of the CAPD group (5.8% +/- 0.4% per month for HD vs 2.9% +/- 0.3% per month for CAPD; difference significant at p less than 0.0001). This difference remained highly significant (p less than 0.01) when corrected for other potential risk factors such as age, gender, hypertensive status, and use of angiotensin converting enzyme inhibitors in patients with diabetic or other forms of glomerular nephropathy. Differences between cohorts were not significant for patients with other diagnoses (p greater than 0.1) although the size of some of these subsets was very small. The physiologic mechanism for the more rapid fall-off of RRF on HD remains speculative, but could be related to renal ischemia secondary to intratreatment hypovolemia and/or to nephrotoxic effects of the inflammatory mediators of extracorporeal circulation.

Female↗
PubMedDate not supplied

Apheresis without substitution fluid: devices, directions and limitations.

Significant economic and medical drawbacks attend the requirement for infusion of large quantities of exogenous substitution fluid during therapeutic plasma exchange. A variety of physicochemical processes are available for the fractionation of plasma (ultrafiltration, fractional precipitation, adsorption, electrophoresis, selective enzymatic degradation) and we review here their application to 'closed loop' apheresis, a format in which the patient's own plasma is returned after the pathogenic species are removed. The different separation processes vary significantly in their method of action, their specificity, and their status of development. Disposables and hardware for two specific protocols, cascade filtration and cryofiltration, are already commercially available and appropriate for routine clinical use in limited subsets of diseases considered treatable by therapeutic apheresis.

Adsorption↗