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Biomedical subjects

Y Nosè

Publications and source records attributed to Y Nosè.

13 recordsLinked to original sources
PubMed2002

In vitro comparison of blood pump induced platelet microaggregates between a centrifugal and roller pump during cardiopulmonary bypass.

UNLABELLED: Platelets are consumed during cardiopulmonary bypass (CPB) and mechanical ventricular assistance, at least partly as a result of the formation of platelet microaggregates in the blood pump. There is no commonly accepted method currently available to detect platelet microaggregates during the use of CPB or left ventricular assist devices (LVAD). The purpose of this study was to develop a flow cytometric method for the quantification of platelet microaggregates generated in blood pumps, and to evaluate the effect of cellular fragments from hemolyzed erythrocytes on the perioperative assessment of platelet counts during CPB. METHOD: Fresh human anticoagulated blood (1IU heparin/mL, activated clotting time 250+/-24 sec.) was circulated for 120 minutes in an artificial circulatory system, containing either a centrifugal pump (CP) or roller pump (RP). Whole blood was used to quantify platelet consumption and to detect circulating platelet microaggregates in a flow cytometer. Platelet consumption was additionally analyzed using an automated "Coulter" blood cell counter. Hemolysis was analyzed by measurement of plasma free hemoglobin (fHb), as well a by flow cytometric detection of red blood cell (RBC) fragments. RESULTS: Flow cytometric analysis demonstrated significantly more circulating platelet aggregates and platelet consumption in the RP than in the CP (p<0.01). Quantification of RBC fragments and plasma free hemoglobin (fHb) levels also indicated significantly increased hemolysis in the RP than in the CP (p<0.01). In contrast, the Coulter count data indicated less platelet consumption in the PP compared to the CP. CONCLUSION: Fragments from hemolyzed erythrocytes have the same size distribution as intact platelets and the number of RBC fragments correlates with the extent of pump-induced hemolysis during CPB. Our data suggest that assessment of platelets by "Coulter counting" cannot distinguish platelets from RBC fragments and may underestimate platelet consumption in the presence of hemolysis during CPB. We conclude that flow cytometry is more accurate in the perioperative assessment of platelet count and platelet aggregation during CPB and LVAD support.

Cardiopulmonary Bypass↗
PubMed1996

Haemodynamic effects of differing blood transfusion rates in infants less than 1500 g.

OBJECTIVE: To investigate whether the haemodynamic effects of the standard 2-3 h blood transfusion increases the risk for intraventricular haemorrhage (IVH) and patent ductus arteriosus (PDA) in very low birthweight infants. METHODOLOGY: In a randomized controlled study, haemodynamic changes using slow and rapid transfusion were compared. Twenty-seven very low birthweight infants were divided between 12h (n = 14) and 3h (n = 13) transfusion groups. Blood pressure, ejection fraction (EF), anterior cerebral artery pulsatility index (PI), blood gases, serum electrolytes and haematocrit were measured pre- and post-transfusion. Infectious status was also monitored. RESULTS: Blood pressure (48.1/25.5 vs 55.7/30.2 mmHg) and EF (0.68 vs 0.73) increased significantly during rapid transfusion (P<0.01) but remained stable with slow transfusion. Serum potassium, base excess and incidence of infection did not increase in either group. CONCLUSIONS: Slow transfusion causes less haemodynamic disturbance than rapid transfusion, thereby preventing the potential risk for IVH and PDA.

Blood Transfusion↗
PubMed1990

Thermofiltration in hypercholesterolemia treatment: analysis of removal and posttreatment cholesterol recovery.

Thermofiltration, a system of membrane plasmapheresis for LDL apheresis, is used to treat patients with refractory hyperlipidemia. In this system, the separated plasma is warmed to or above physiologic temperature, filtered with a membrane filter, and returned to the patient on-line. Plasma infusion products are not required. In this study one calculated plasma volume was treated weekly, biweekly, or monthly in patients classified as type II hypercholesterolemic. Reduction and sieving of lipoproteins were evaluated. The reduction ratios of high-density lipoprotein cholesterol (HDLc) and low-density lipoprotein cholesterol (LDLc) were 0.30 +/- 0.06 and 0.58 +/- 0.05, respectively (mean +/- S.D.). Sieving coefficients of the plasma filter for HDLc and LDLc were 0.62 +/- 0.12 and 0.03 +/- 0.02, respectively (mean +/- S.D. of 31 treatments). To evaluate the posttreatment recovery the apparent fractional catabolic rates (FCRa) for total cholesterol and LDLc were calculated. FCRa was 0.151 +/- 0.06 and 0.148 +/- 0.06 day-1 for total cholesterol and LDLc, respectively. The ratio of the posttreatment concentration on the seventh day to the concentration immediately pretreatment was found to be significantly higher for HDLc than for LDLc, 0.92 +/- 0.8 vs. 0.77 +/- 0.1 (mean +/- S.D.), due to faster HDLc recovery. The ratio of LDLc/HDLc was lowered for up to 2 weeks after the treatments.

Adult↗
PubMed1990

Effect of anticoagulant on biocompatibility in membrane plasmapheresis.

The effect of heparin or citrate anticoagulation on blood cellular, complement pathway and coagulation pathway was investigated in a membrane plasma exchange procedure. Two membrane plasma separators constructed of cellulose di-acetate (CA) and polyvinyl chloride (PVC) were evaluated with heparin or citrate alone for anticoagulation in a 26 year old male with myasthenia gravis. Maximum white blood cell counts decrease was 21% at 30 min for the CA with heparin while no decrease was observed for the other schemes. Platelet counts changes were comparable between heparin and citrate, while the PVC groups showed less changes than the CA groups. The CA groups, regardless of the type of anticoagulant used, indicated that complement activation occurred via the classical pathway within the module in addition to the activation via alternative pathway for the CA with heparin. In the PVC groups, complement activation was noted to occur only when heparin was used for anticoagulation. PT and PTT showed slight increases with citrate, while they were remarkably prolonged with heparin. Citrate showed less changes in cellular and humoral factors compared to heparin. CA with heparin was the most activating combination of membrane material and anticoagulant, while the PVC with citrate was the least activating combination.

Adult↗
PubMed1989

Development of compliance chamber diaphragms with reduced permeability.

The implantable ventricular assist systems currently undergoing clinical readiness testing shuttle the displaced gas between the non-blood side of the pumping diaphragm and an elastic chamber generally called a "compliance chamber" or variable volume device. The movement of the stored gas allows the pump to fill and empty without compression or expansion of the gas behind the pump diaphragm. The material used for the construction of compliance chambers should be fatigue resistant to withstand the 63 million flexes per year of the blood pump. The material should also be biocompatible and highly impervious to gases. Significant diffusion of gases from the compliance system necessitates external make-up gases to somehow be added to the internal system. Material selection is complicated by the fact that most fatigue-resistant elastomers also have high gas permeability. In order to solve this problem, bilayer compliance chambers have been developed using biocompatible and fatigue-resistant polyolefin rubber comolded with relatively impervious butyl rubber.

Assisted Circulation↗
PubMed1989

Biomodulation effects of extracorporeal circulation in apheresis.

The association of biochemical and cellular abnormalities in various disease states provides the rationale for apheresis technologies. Plasmapheresis by plasma exchange has severe technical and clinical limitations due to the nonselective removal of plasma factors. Plasmapheresis methods for the more selective removal of plasma components include membrane filtration, sorption, and physico-chemical methods such as precipitation. These methods can also eliminate the need for plasma product replacement and be more specific to the clinical needs. While plasmapheresis technologies are designed primarily for solute removal, the methodology itself will have a biomodulating influence and will impact on the course of the disease state. Extracorporeal biomodulation is defined as the act of effecting changes either procedurally induced or procedurally associated in the cellular or biochemical milieu of the body. Factors to be considered in an extracorporeal procedure such as plasmapheresis include the duration of an individual treatment, the degree of solute removal selectivity, the prescribed frequency for the treatment, the type of equipment employed, the choice of anticoagulant, and the materials for blood and plasma contact. Thus, the modulatory effects of the methodology occur not only in the humoral system but also among the cells. The effects of the modulation will extend beyond the procedure time. The general direction in material research for extracorporeal circulation is to minimize the biological response. However, the modulating effects of the procedure, independent of the removal effects, suggest that the proper choice of materials in the extracorporeal circuit can benefit the patient. With the various techniques of solute removal and material availability, the clinician may chose the biomodulating system for the treatment of a given disease state.

Extracorporeal Circulation↗
PubMed1988

Titanium-nickel intravascular endoprosthesis: a 2-year study in dogs.

Twelve 5-mm-internal-diameter intravascular endoprostheses of noncorrosive, shape-memory titanium-nickel (TiNi) alloy were delivered transluminally by catheter and implanted in the iliac (n = 10) and femoral (n = 2) arteries of six normal dogs for either 1 or 2 years in order to evaluate the implantation technique and long-term effects. The patency rates were as follows: at 1 month, 92% (11/12); at 1 year, 100% 11/12 widely patent; 1/12 recanalized); and at 2 years, 100% (3/4 without stenosis; 1/4 with 20% stenosis). No migration, erosion, inflammation, surface thrombus, or stenosis of the side branches was seen; an absence of untoward angiographic and histopathologic effects was detected at 1 and 2 years. The neointima was completely endothelialized, without changes in thickness over time, 229.3 +/- 127.6 microns after 1 year and 223.3 +/- 216.7 microns after 2 years (p = not significant). The neointimal layer became thicker toward its distal aspect (p less than or equal to .05). Satisfactory delivery, long-term patency, and biocompatibility (manifested as a thin, stable neointima) were observed for the TiNi intravascular endoprosthesis at 1 and 2 years.

Animals↗
PubMed1988

Heat dissipation through the blood contacting surface of a thermally driven LVAS.

A heat exchanger for a totally implantable heat driven LVAD is an essential element in overall system thermal management. The heat exchange is accomplished by supplying cooling water from a pusher-plate driven water pump to the engine and then to the heat exchanger on the pump housing. The temperature of the interface between the blood and pump surface is of critical importance for clinically acceptable operation of the system. Temperatures were measured by instrumenting a pump housing with thermocouples and an electric heater on a mock circulatory loop. Flows were varied from 1 to 8 l/min and heat input was 20 watts. At 1.0 l/min pump flow the maximum inner surface temperature rise is 4.5 degrees C. In vitro tests were conducted to examine the effect of elevated temperature on platelete function. Both platelet aggregation and adhesion were reduced at elevated temperatures of 42 and 47 degrees C indicating a potential benefit of reduced thrombogenesis on the heated housing surface.

Assisted Circulation↗
PubMedDate not supplied

Operating point control system for a continuous flow artificial heart: in vitro study.

We proposed and developed a practical and effective servo control system for rotary blood pumps. A rotary blood pump for assisting the failing natural heart should be operated only in physiologically acceptable conditions. The operation of a rotary blood pump is based on the rotational speed of the impeller and pressure head. If the pump flow and the pressure head are set within an acceptable range, the driving condition is deemed normal condition, and this control system maintains the preset operating point by applying proportional and detective control (PD control). If the pump flow or pressure head is outside the acceptable range, the driving condition is determined to be abnormal condition, and this system operates the pump in a recovery fashion. If the driving condition is kept under abnormal conditions of sudden decrease of the flow, the condition is termed a suction condition. The controller releases the pump from the suction condition and later returns it to the normal condition. In this study, we evaluated these servo control modes of the centrifugal pump and confirmed whether the performance of this proposed operating point control system was practical.

Algorithms↗