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Biomedical subjects

S Sideman

Publications and source records attributed to S Sideman.

At least 91 records · Page 5Linked to original sources
PubMed1984

A computer study of the left ventricular performance based on fiber structure, sarcomere dynamics, and transmural electrical propagation velocity.

A model of the left ventricle which combines a spheroidal geometry with a spatial fiber angle distribution is presented. The mechanics of each muscle fiber is described by its passive stress-strain relationship, active stress-strain relationship, and an activation function (half a sinusoid) which represents the time-dependent degree of activation of the fiber. A stress-strain rate relationship which characterizes the muscle fibers is used to calculate the mechanics of left ventricular contraction during ejection. Furthermore, a radial electrical signal propagation from the endocardium to the epicardium is used here as a first approximation to the actual depolarization sequence. The model is used to describe the process of contraction throughout the systole. The different calculated parameters and indices of left ventricular function are presented and discussed for different preloading, afterloading and contractility conditions. The maximum elastance is found to be an optimal macroscale parameter of contractility, as it is completely preload and afterload independent, and is a good reflection of the active microscale sarcomere stress-strain relationship.

Computers↗
PubMed1984

Controlling anticoagulation in extracorporeal blood circuits (hemoperfusion).

The study demonstrates that different individuals (monkeys) need different heparin doses so as to avoid either clotting or bleeding when an extracorporeal blood system is involved. The linear correlation between PT and WBPTT values enables to utilize the latter for monitoring the heparin level in the blood. One procedure is based on the application of the Gotch and Keen intravenous heparinization model in its steady state limit by utilizing the pre-treatment evaluation of k/S, the ratio of the elimination rate constant to the individual's sensitivity to heparin. A second procedure involves the direct heparinization of the extracorporeal system. The heparin infusion rate is monitored through the arterial WBPTT values after relating the individual's PT or WBPTT values to the in vitro heparin concentration in the blood. In vitro and in vivo study of the effect of hemoperfusion through a column containing anion exchange particles on the amount and rate of heparin administration indicates that only the in vivo results are meaningful. The sharp response of WBPTT to relatively small changes of citrate concentration in the blood precludes individual monitoring by WBPTT. Work on the advantage of utilizing heparin together with citrate is required.

Animals↗
PubMed1983

Preparation of a biocompatible albumin-coated ion exchange resin for bilirubin removal from the blood of jaundiced newborns.

Removal of bilirubin by hemoperfusion with ion exchange resin particles is suggested to replace exchange transfusion of blood of jaundiced infants in some cases of unconjugated hyperbilirubinemia. The hemoperfusion system developed here consists of a packed bed of a macroreticular resin which is made biocompatible by a coating of a monomolecular layer of albumin. The choice of the appropriate ionic form of the resin and the proper albumin coating and crosslinking procedure assures a high bilirubin adsorption capacity and excellent blood compatibility of the resin. The albumin coated resin removes in vitro 80-90% of the bilirubin initially present in the plasma. The results encourage in vivo clinical studies.

Adsorption↗
PubMed1983

Novel composite sorbent beads for paraquat removal by hemoperfusion.

The present report describes the development and performance of a column that is to be used for removal of paraquat from circulating blood in a hemoperfusion-type set-up. The key element of the system is a newly developed sorbent material containing fuller's earth entrapped in cross-linked agarose beads (Talosit). The technique produces a sorbent material exhibiting a very large active surface area while allowing for high mobility of paraquat molecules within the beads and favorable flow characteristics of packed column. Cross-linking of the agarose (by epichlorohydrin) also has a most beneficial effect on the mechanical strength of the beads as well as on their stability to sterilization in an autoclave. The composite beads exhibit good blood compatibility. A scanning electron microscope analysis of the beads showed no adherence of cellular blood components after contact with blood. Moreover, no significant changes in plasma composition had taken place when the beads were properly conditioned prior to contact with fresh human blood. A comparative study of paraquat removal from saline solution by the new beads and by cellulose-coated activated charcoal (Adsorba-300C) indicates a higher removal rate with the former. The results obtained so far with this new sorbent are very promising and extension of these studies to in vivo hemoperfusion is under way.

Adsorption↗
PubMed1983

Energy metabolism rate equation for fasting and postabsorptive subjects.

The energy metabolism rate, an important parameter in severe clinical polytrauma and burns, is evaluated here using mass conservation law and simple thermodynamic considerations. The expressions for the energy and fat metabolism rates are evaluated utilizing easily measurable quantities: oxygen consumption, CO2 production, and nitrogen excretion rates. The derived equations are identical for the fasting and postabsorptive states, independent of feed composition. A new criteria for distinguishing between the fasting and postabsorptive states is suggested. These equations should help in evaluating energy metabolism rate for patients receiving continuous parenteral nutrition.

Calorimetry↗
PubMed1982

Resin hemoperfusion for unconjugated bilirubin removal.

The application of an anionic macroreticular ion exchange resin, coated with a thin cross-linked albumin layer, as a hemoperfusion device for the removal of unconjugated bilirubin from the blood of hyperbilirubinemic newborn babies is reviewed. In vivo hemoperfusion runs with hyperbilirubinemic animal models - either by a choledocho-suprarenal vein shunt or by direct infusion of bilirubin into the vein - showed that a 40-ml resin column can remove some 20 mg bilirubin in 3 h. Hemoperfusion of female 8-14 kg baboons showed no significant effect of the column on blood chemistry and coagulation factors and repeated runs had no ill effects.

Adsorption↗
PubMed1981

Bilirubin removal from an hepatic failure patient by resin hemoperfusion.

An hemoperfusion (HP) column, packed with beads of a macroreticular MR ion exchange resin which were made biocompatible by coating with a fine layer of cross-linked human albumin, was applied to the removal of bilirubin (BIL) from a jaundiced 69-year old man with hepatic failure. The column was found most suitable for BIL removal. However, the high volumetric mass transfer coefficient of the unconjugated (UC) BIL indicates that this column could best be used for BIL removal from babies suffering from unconjugated hyperbilirubinemia.

Acute Disease↗
PubMed1981

In vivo hemoperfusion studies of bilirubin removal from jaundiced dogs.

Removal of bilirubin by hemoperfusion (HP) on a macroreticular ion-exchange resin is suggested as a novel clinical procedure for the treatment of jaundiced newborn babies. The efficiency and biocompatibility of the proposed macroreticular (MR) ion exchange column was tested in vivo with jaundiced dogs. An animal model with a choledocho-suprarenal vein shunting allowed to test the column capacity for the adsorption of conjugated and unconjugated bilirubin. A second animal model, based on infusing unconjugated bilirubin directly into the blood stream, enabled to test the column operation at desired unconjugated bilirubin concentrations. The results of the in vivo hemoperfusion tests are very encouraging and compare favorably with bilirubin removal from babies by exchange transfusion (ET). Operating a column containing 10 ml resin per kg body weight for 3 hours removed over 1.7 times the initial unconjugated bilirubin content. Furthermore, the animals seemed to be unaffected by the HP procedure; the changes due to hemoperfusion on blood chemistry, hematology and some hormone levels were practically insignificant.

Animals↗
PubMed1979

Removal of bilirubin by hemoperfusion with ion exchange resins.

Removal of bilirubin by hemoperfusion with macroporous resins is suggested to replace exchange transfusion of blood from jaundiced infants. Anion exchangers tested for BIL binding rate and the effects of various system parameters, i.e. particle size, temperature, bed volume, fluid flow rate and particle porosity are reported. The dissociation equilibrium constant K of the BIL-ALB (albumin) complex was determined from the equilibrium adsorption isotherms data, at different ALB concentrations. Increasing ALB concentration decreased the BIL adsorption rate. For a given ALB concentration, the ratio of unbound to total BIL was constant and the initial BIL adsorption rate was independent of total BIL concentration.

Adsorption↗
PubMed1977

Membrane permeability for inorganic phosphate ion.

The need for a more efficient removal of inorganic phosphate ions from the blood of uremic patients has led to the quest for blood-compatible semipermeable membranes with a high permeability for phosphate ions. Commercial hemodialysis membranes, various hydrogel-type membranes and a number of collodionbased charged membranes were compared. Positively charged collodion membranes were found most promising for future application in hemodialysis or hemoperfusion systems.

Acrylamides↗