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Biomedical subjects

P S Malchesky

Publications and source records attributed to P S Malchesky.

At least 19 recordsLinked to original sources
PubMed2001

Artificial organs and vanishing boundaries.

With the first clinical use of the artificial kidney over 5 decades ago, we entered into a new era of medicine-that of substitutive and replacement therapy. Yet it took nearly another 15 years until chronic treatment was possible and nearly another 15 years until widespread treatment was possible due to government support. The history of development and clinical use of other artificial organ technologies such as the artificial heart and heart valves, the artificial lung, artificial blood, joint replacements, the artificial liver, the artificial pancreas, immunologic, metabolic, and neurologic support, neurocontrol, and tissue substitutes have followed similar long development paths. Despite their relatively long time to be put into clinical use, the contributions of artificial organ technologies to the betterment of mankind have been unquestionably a major success. For example, modern day surgery would not be possible without heart-lung support, and the technologies for heart support have led to the development of various minimally invasive technologies. The powerful impact that artificial organ technologies presently has on our lives is seen through the statistic that in the U.S.A. nearly 1 in 10 persons is living with an implanted medical device. With the aging of our population and the improvements in technologies, these numbers will only increase.

Animals↗
PubMed2001

Membrane processes for plasma separation and plasma fractionation: guiding principles for clinical use.

The use of membranes in blood processing range from the use of large-pore structures for filtration of blood for the removal of large particles (>20 microm transfusion filters) to membranes for the dialysis of blood for the removal of low molecular weight solutes in the treatment of renal failure. Within the past 20 years, membranes have been applied in the separation of plasma from whole blood. Compared to centrifugal plasma separation membrane, plasma separation is preferred when used with online plasma fractionation since the plasma is free of cells. In addition, membranes have also been applied in the online treatment of plasma for the selective removal of macromolecules in selected disease states obviating the need for plasma replacement products. The membranes used for plasma separation and fractionation may be distinguished from conventional dialysis membranes and high-flux membranes used in hemofiltration by their very high or select passage of plasma proteins. Membrane techniques are simple and safe to apply and can be competitive to other plasma separation and treatment technologies.

Blood Component Removal↗
PubMed2001

Apheresis technologies and clinical applications: the 2000 International Apheresis Registry.

The developments in apheresis technologies and techniques and their clinical applications worldwide are technologically, sociologically, and economically driven. In the past, apheresis survey statistics have highlighted both the differences by geographical region in clinical practices and in the types of technologies utilized. While a national view of apheresis is critically important, an international view of apheresis may be more representative overall of this therapeutic modality than national results that are highly dependent on the local economics and the available technologies. These regional differences have provided a basis for the scientific and clinical assessments of these apheresis technologies and their clinical outcomes and have impacted the marketing and business developments of new technologies worldwide. The results of the International Apheresis Registry for 2000 reporting on 39 centers on 4 continents are presented. This survey collected data on 1,080 patients for a total of 15,257 treatments. Information gathered included patient demographics, medical history, treatment diagnoses, treatment specifics (type, methodology, access type, anticoagulants, drugs, equipment usage), side effects, clinical response, and payment provider. As in the prior International Apheresis Registry for 1983, the survey results highlighted the regional differences in apheresis usage and treatment specifics, indicating that an international overview of apheresis may be more representative of the impact of this therapeutic modality.

Adult↗
PubMed1998

A mechanistic model of plasma filtration.

A model describing the sieving and transmembrane pressure behavior of plasma filtration is developed and numerically simulated. The model assumes a mechanistic criteria for particle passage through a membrane with cylindrical pores. The initial pore diameter distribution and porosity are assumed to be known. Model inputs include the particle diameter distribution, concentration and total flow rate of the permeate plasma solution. Outputs of the model include transmembrane pressure, the time-averaged sieving coefficients, and size distributions of the deposited particles and accumulated filtrate particles. Optimal filtration is characterized by high, stable sieving coefficients for desired particles, high retention of larger particles and relatively small increases in transmembrane pressure. These characteristics are realized for membranes with mean pore diameters equal to or slightly larger than mean permeate particle diameters. Simulations demonstrate that the incorporation of membrane properties into models of plasma filtration is both significant and readily possible.

Biophysical Phenomena↗
PubMed1997

Technical and economic feasibility of reusing disposable perfusion cannulas.

OBJECTIVE(S): The reuse of disposable devices is a potential source of significant cost savings to hospitals. Venous and arterial perfusion cannulas under new and reused conditions were selected to identify the clinical, safety, technical, logistic, and economic issues that must be addressed to realize these savings. METHODS: Single- and dual-stage venous and arterial cannulas from two manufacturers were tested when new, after initial clinical use, and after a single clinical use plus up to nine simulated reuses. Reuse was simulated by end-to-end bending, coupling and uncoupling of the connectors, and by two 1-hour soaks in plasma at 4 degrees and 40 degrees C, respectively. Cannulas were decontaminated and then processed by a peracetic acid-based liquid chemical sterilization system after each use/reuse. Sterilization was validated by eliminating Bacillus subtilis spores from the cannulas on each of five consecutive cycles. Cannulas were tested for physical changes, functional integrity, biocompatibility, and in vivo performance in sheep. A cost analysis was also performed. RESULTS: Sterilization was successfully achieved. Mechanical changes were less than 20% on all variables studied and were undetectable by experienced cardiac surgeons in selective evaluation. No clinically important differences were found between new and reused cannulas, even after nine simulated reuses. Reusing cannulas four times would reduce the cost per procedure from $53 to $19 (64%). CONCLUSIONS: Preliminary data suggest that the perfusion cannulas tested can be safely and efficaciously used five times. Limited reuse of these disposable cannulas is technically feasible and cost-effective. Cannula reuse would result in a small incremental savings; however, with more expensive devices and higher-volume sterilization procedures, the savings could be considerably greater. This program provides a model for evaluation of other single-use medical devices for reuse.

Animals↗
PubMed1996

Low-density lipoprotein removal methods by membranes and future perspectives.

Since the application by Thompson et al. in 1975 of plasma exchange for the treatment of 2 patients with familial hyperlipidemia, plasma purification techniques for selective low-density lipoprotein (LDL) removal (i.e., LDL apheresis) have been developed and adopted for the management of this disease. Thermofiltration is one of the LDL apheresis systems that utilizes membrane techniques developed by Nose and Malchesky's group in 1985. This article reviews its rationale, in vitro studies, animal studies, and clinical investigation. Thermofiltration effectively and selectively removes LDL cholesterol while retaining in the plasma physiologically important macromolecules such as albumin and high-density lipoprotein (HDL) cholesterol. Based on the global view of the treatment of atherosclerosis by LDL apheresis, membrane techniques are as effective, safe, and simpler to apply than other methods. Additionally, these methods are effective for the removal of lipoprotein (a) and fibrinogen; thus, they can address the needs in these application areas.

Animals↗
PubMed1995

Monoethylglycinexylidide formation as an independent measure of warm hepatic ischemia and reperfusion injury.

An accurate serologic measure of hepatic function would be clinically useful in selecting donors for liver transplantation. An experimental model that incorporates varying lengths of total hepatic warm ischemia with reperfusion injury was utilized to compare serologic parameters and mitochondrial performance of oxidative phosphorylation in predicting hepatocellular injury. Monoethylglycinexylidide (MEGX) formation following bolus intravenous lidocaine injection was found to be significantly decreased (P < 0.0001) at all periods of ischemia when compared to that in nonischemic controls. A serum MEGX level of < 50 micrograms/liter suggested severe hepatic damage. No correlation was found between MEGX level and liver viability as measured by animal survival. Serum transaminase (AST and ALT) levels demonstrated progressive, nonsignificant elevations with increasing length of ischemia (P = 0.0779 at the maximum ischemic time). Polarographic measurements of mitochondrial oxidative phosphorylation did not reveal a significant alteration in subcellular metabolism with prolonged ischemic time. These data highlight the comparative sensitivity of MEGX formation as an early quantitative measurement of hepatocellular injury during warm ischemia, although it was not predictive of organ viability.

Adenosine Triphosphate↗
PubMed1995

Extracorporeal techniques of endotoxin removal: a review of the art and science.

The incidence of sepsis in the United States has risen in the past few years, and mortality from sepsis has risen over the past several decades. These increases have occurred despite the progress made in antibiotic therapy. The high mortality rate may not be related to the bacteria themselves but rather to the host's response. Of particular concern is the bacterial release of endotoxins, the development of endotoxic shock, and the resulting multiorgan failure, which has a high fatality rate and is the leading cause of death in patients admitted to intensive care units. Removing or neutralizing endotoxins are the two major therapeutic approaches to treating sepsis. To date, pharmacological methods have not been successful. Extracorporeal techniques are based on filtration, sorption, or both. Results with hemofiltration have not been definitive, in part because endotoxin levels have not been measured. Sorption devices, based on polymyxin B and anion exchange matrices, do remove endotoxins. Clinical studies in Japan on septic shock or multiorgan failure with polymyxin-B-bound fibers in direct hemoperfusion continue to suggest the utility of extracorporeal techniques for endotoxin removal. Continued effort is required and warranted to assess the clinical efficacy of these techniques.

Endotoxins↗
PubMed1995

Apheresis technologies: an international perspective.

The developments in apheresis techniques and their clinical applications world-wide are technologically driven. In the past, apheresis survey statistics have high-lighted both the differences by region in clinical practice and in the types of technologies utilized. Such differences have provided a basis for the scientific and clinical assessments of these apheresis technologies and their clinical outcomes and have stimulated the marketing and business development of new technologies world-wide. A review of the regional practices and technologies utilized provides a perspective on the future role of apheresis and its developments in clinical practice. While technology is a driving force for the development of new techniques for clinical practice, it is not the only market force. For technology introduction, several other important issues need to be considered. Regulations at the local and, most importantly, the federal level impact the timing for new technology introduction. Reimbursement by healthcare payers is critically important from the initiation of the development of a technology through its clinical use. Clinical trials are critically important to show the safety and clinical- and cost-effectiveness of the technology in order for payers to provide reimbursement for its use, but these trials are sometimes long and costly. Research funding availability at the governmental and commercial levels critically impacts new technology investigation and its introduction. Apheresis technology developments offer new hopes and promises for the clinical team; however, their development, introduction, and utilization will be influenced by the prevailing market forces.

Blood Component Removal↗