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Mrinal K. Dewanjee - One of the best experts on this subject based on the ideXlab platform.
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In vitro and in vivo evaluation of the comparative thrombogenicity of cellulose acetate Hemodialyzers with radiolabeled platelets
Asaio Journal, 1994Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Aldo N. Serafini, Raymond Elson, Gaston Zilleruelo, Carlos F. Cavagnaro, George K. Panoutsopoulos, Cleide Suguihara, Shabbir Ezuddin, George N SfakianakisAbstract:: Platelet consumption and platelet kinetics during hemodialysis were quantified in Yorkshire pigs with In-111 labeled platelets. Six anesthetized pigs (20-25 kg) were hemodialyzed at 150 ml/min for 3 hr. All pigs were injected with autologous In-111 labeled platelets (300-420 microCi) 24 hr before dialysis and were systemically heparinized (ACT > 400 sec) before cannulation. Hemodialysis was instituted with a Drake-Willock hemodialysis machine and a hollow fiber dialyzer (Cobe4, 0.6 m2). In vitro sham dialysis was carried out at 150 ml/min for 3 hr with six more dialyzers in a flow-loop with the blood reservoir maintained at 37 degrees C. In vitro thrombogenicity over-estimates (10-fold) in vivo values. In both systems, platelet deposition on dialyzers reached a steady state, suggesting a constant rate of thrombus formation and embolization in the hollow fiber system. The relative thrombus distribution after 3 hr of dialysis was similar in both systems, with adherent thrombi in the entry and exit ports and highest numbers in the midsection of the Hemodialyzer. Biodistribution after 3 hr of dialysis indicated that thrombosis of the Hemodialyzer and arterial and venous traps as well as embolization reduced the platelet pool in the blood and increased platelet emboli in lung, brain, kidneys, and skeletal muscle, as measured by the In-111 labeled platelets.
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quantitation of thrombogenicity of Hemodialyzer with technetium 99m and indium 111 labeled platelets
Nuclear Medicine and Biology, 1993Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Aldo N. Serafini, Gaston Zilleruelo, Kees Ruzius, George N SfakianakisAbstract:Abstract The platelet thrombogenicity of a Hemodialyzer was quantified with 99m Tc- and 111 In-labeled platelets. The platelets collected from blood of Beagle dogs, Yorkshire pigs and human volunteers were labeled with 111 In-tropolone (detergent-free) and 99m Tc-HMPAO. Hemodialysis was performed with a hollow-fiber dialyzer (HFD) in a flow-loop, the temperature of which was maintained at 37 °C, with flow-rates of 7, 150 and 270 mL/min; after dialysis, the HFD radioactivity was measured with an ionization chamber and imaged with a γ-camera. The radioactivity of samples of hollow-fibers taken from the top, middle and bottom of the dialyzer was determined with a γ-counter. The mean values of Hemodialyzer-adherent platelet radioactivity were calculated for both radionuclides. The canine platelets were found to be more thrombogenic than porcine and human platelets. The adhesivity of porcine platelets to the biomaterial (cellulose-acetate) of the dialyzer approximated that of human platelets. The 99m Tc label underestimated the thrombus formation ( P 111 In- and 99m Tc-labeled platelets suggests that both radionuclides could be used for measurement of device-induced thrombogenicity and may provide an estimation of prosthesis-induced thrombogenicity of human platelets from animal studies.
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Quantitation of comparative thrombogenicity of dog, pig, and human platelets in a Hemodialyzer.
Asaio Journal, 1992Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Amaeury Sanchez, Aldo N. Serafini, Raymond Elson, Gaston Zilleruelo, George N SfakianakisAbstract:: Comparative platelet thrombogenicity was quantified with In111 labeled platelets. The platelets collected from the blood of Beagle dogs, Yorkshire pigs, and human volunteers were labeled with detergent free In111 tropolone, and sham hemodialysis (SHD) was performed with a hollow fiber dialyzer in a flow loop at 37 degrees C, with flow rates of 7, 150, and 270 ml/min. After SHD, Hemodialyzer radioactivity was measured with an ionization chamber, gamma counter, and it was imaged with a gamma camera. The mean values of Hemodialyzer-adherent platelet radioactivity were calculated. Canine platelets are more thrombogenic than porcine and human platelets. Quantitation of comparative thrombogenicity with In111 platelets may provide an estimation of prosthesis induced thrombogenicity of human platelets from animal studies.
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Evaluation of comparative thrombogenicity of cellulose-acetate Hemodialyzer in in vitro and in vivo system with radiolabeled platelets
1992 14th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1992Co-Authors: Mansoor Kapadvanjwala, Carlos F. Cavagnaro, George K. Panoutsopoulos, Loukia S. Tourkochoriti, Mrinal K. DewanjeeAbstract:Platelet thrombus in the Hemodialyzer, arterial and venous traps in the extracorporeal circuit was never quantified. Platelet consumption during hemodialysis was measured in Yorkshire pigs with In-111 labeled platelets. Six anesthetized pigs (20–25 kg) were hemodialyzed at 150 ml/min for 3 hours. All pigs were injected with autologous labeled platelets (300–420 μCi), 24 hours prior to dialysis and were systemically heparinized prior to cannulation. Hemodialysis was instituted with a dialyzer pump and hollow-fiber dialyzer (Cobe4,0.6 m2). In vitro sham-dialysis was carried out with 6 more dialyzers in a flow-loop using porcine blood at 150 ml/min. In vitro thrombogenicity was higher (10-fold) than in vivo values, thus overestimates in vivo values. In both systems platelet deposition on dialyzers reached a steady state, suggesting a constant rate of thrombus formation and embolization. The relative thrombus distribution in the dialyzer at 3 hours of dialysis was similar in both systems.
Claudio Ronco - One of the best experts on this subject based on the ideXlab platform.
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Blood and Dialysate Flow Distributions in Hollow-Fiber Hemodialyzers Analyzed by Computerized Helical Scanning Technique
Journal of The American Society of Nephrology, 2020Co-Authors: Claudio Ronco, Carlo Crepaldi, Alessandra Brendolan, Mariapia Rodighiero, Marco ScabardiAbstract:ABSTRACT. The efficiency of a Hemodialyzer is largely dependent on its ability to facilitate diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. This article describes the distribution of the blood and dialysate flows in hollow-fiber Hemodialyzers analyzed with a computerized scanning technique. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation using human blood with hematocrit (Hct) adjusted at 25 and 40%. Sequential images were obtained with a helical scanner in a 1-cm-thick fixed longitudinal section of the dialyzer. Average and regional blood flow velocity and wall shear rates were measured by using the reconstructed imaging sequence. The method allowed the calculation of single-fiber blood flow and single-fiber wall shear rate (SF wSh) in different regions of the Hemodialyzer. In 38 patients on chronic hemodialysis, creatinine and phosphate clearance displayed a significantly negative correlation with Hct ( P versus 301 s −1 ). A similar technique was used to study the flow distribution in the dialysate compartment in three different types of Hemodialyzers with characteristic dialysate compartment design: (A) standard configuration; (B) space yarns (spacing filaments preventing contact between fibers); and (C) Moire structure (wave-shaped fibers to prevent contact between adjacent fibers). Clinical sessions of hemodialysis were also carried out to measure blood- and dialysate-side urea clearances in the different Hemodialyzers. Macroscopic and densitometric analysis revealed that flow distribution was most homogeneous in the dialyzer with Moire structure (type C) and least homogeneous in the standard dialyzer (type A). Space yarns (type B) gave an intermediate dialysate flow distribution. Urea clearance ( P
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Blood and dialysate flow distributions in hollow-fiber Hemodialyzers analyzed by computerized helical scanning technique.
Journal of the American Society of Nephrology : JASN, 2020Co-Authors: Claudio Ronco, Carlo Crepaldi, Alessandra Brendolan, Mariapia Rodighiero, Marco ScabardiAbstract:The efficiency of a Hemodialyzer is largely dependent on its ability to facilitate diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. This article describes the distribution of the blood and dialysate flows in hollow-fiber Hemodialyzers analyzed with a computerized scanning technique. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation using human blood with hematocrit (Hct) adjusted at 25 and 40%. Sequential images were obtained with a helical scanner in a 1-cm-thick fixed longitudinal section of the dialyzer. Average and regional blood flow velocity and wall shear rates were measured by using the reconstructed imaging sequence. The method allowed the calculation of single-fiber blood flow and single-fiber wall shear rate (SF wSh) in different regions of the Hemodialyzer. In 38 patients on chronic hemodialysis, creatinine and phosphate clearance displayed a significantly negative correlation with Hct (P < 0.05), but this correlation was not found for urea, although a trend toward reduction could be observed. The suggested explanation of this phenomenon is the significant reduction in effective plasma water flow across the Hemodialyzer in presence of a progressive rise in Hct. The second explanation for this phenomenon may be found in the nonhomogeneous distribution of blood flow within the fibers observed at the sequential imaging. This, in fact, could also explain the negative trend observed for urea. At higher Hct levels, single-fiber blood flow velocity and SF wSh were significantly lower in the fibers situated at the periphery of the bundle. At the same time, SF wSh tended to decrease in peripheral fibers, showing a value near half of that observed in the central fibers of the bundle (165 versus 301 s(-1)). A similar technique was used to study the flow distribution in the dialysate compartment in three different types of Hemodialyzers with characteristic dialysate compartment design: (A) standard configuration; (B) space yarns (spacing filaments preventing contact between fibers); and (C) Moiré structure (wave-shaped fibers to prevent contact between adjacent fibers). Clinical sessions of hemodialysis were also carried out to measure blood- and dialysate-side urea clearances in the different Hemodialyzers. Macroscopic and densitometric analysis revealed that flow distribution was most homogeneous in the dialyzer with Moiré structure (type C) and least homogeneous in the standard dialyzer (type A). Space yarns (type B) gave an intermediate dialysate flow distribution. Urea clearance (P < 0.001) increased significantly with types B and C, compared with the standard dialyzer. Type C had the highest clearances, although they were not significantly greater than type B. In conclusion, a significant blood-to-dialysate flow mismatch may occur in hollow-fiber Hemodialyzers due to either uneven blood flow distribution or a dialysate channeling phenomenon external to the fiber bundle. Improvement in dialyzer design may overcome these problems, at least in part.
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Fluid mechanics and crossfiltration in hollow-fiber Hemodialyzers.
Contributions To Nephrology, 2020Co-Authors: Claudio RoncoAbstract:The effi ciency of a Hemodialyzer is largely dependent on its ability to facilitate diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch betwee
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Mechanisms of solute transport in extracorporeal therapies.
Contributions To Nephrology, 2020Co-Authors: Claudio Ronco, Nathan W. LevinAbstract:Diffusion and convection are the main mechanisms involved in the membrane separation processes occurring in extracorporeal hemodialysis. Operational parameters should be optimized in hollow fiber Hemodialyzers to achieve the maximal efficiency. The nature of blood which is a non Newtonian fluid, requires specific attention in the design of dialyzers to ensure that the blood compartment operates properly. Similar attention must be placed in the design of the dialysate compartment to ensure a homogeneous distribution of the fluid and to prevent blood to dialysate flow mismatch. Finally, the membrane represents the third component of the Hemodialyzer. Membrane performance depends on the used biomaterial, its biocompatibility, the thickness, the hydrophilic-hydrophobic mixture, the hydraulic permeability and the number and diameter of the pores. In this setting, diffusion and convection tend to reciprocally interfere, producing a final result that depends on the prevalence of one or the other mechanism for every specific solute.
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Effects of arterial port design on blood flow distribution in Hemodialyzers.
Blood Purification, 2009Co-Authors: Jaeyong Sung, Eungtaek Kang, Claudio RoncoAbstract:Background/Aims: Blood flow profiles in fiber bundles depend on the design of the arterial port and affects the biocompatibility of the Hemodialyzer. We analyzed the effects of arterial port design on blood flow distribution in fiber bundles using nonintrusive imaging techniques. Methods: The velocity fields in arterial ports and the hemodynamics in fiber bundles were analyzed for Hemodialyzers with different configurations using particle image velocimetry and perfusion computed tomography. Results: In a Hemodialyzer with standard arterial ports, high blood flow profiles in the central and peripheral regions and low blood profiles in the middle region were developed due to jet flow and vortices around the jet. In a Hemodialyzer with spiral arterial ports, higher flow profiles were developed due to the central vortices that decrease perfusion into the fiber bundles. Conclusion: The arterial port design of Hemodialyzers should be optimized such that jet flow and vortices do not impair dialysis efficiency and biocompatibility.
Mansoor Kapadvanjwala - One of the best experts on this subject based on the ideXlab platform.
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In vitro and in vivo evaluation of the comparative thrombogenicity of cellulose acetate Hemodialyzers with radiolabeled platelets
Asaio Journal, 1994Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Aldo N. Serafini, Raymond Elson, Gaston Zilleruelo, Carlos F. Cavagnaro, George K. Panoutsopoulos, Cleide Suguihara, Shabbir Ezuddin, George N SfakianakisAbstract:: Platelet consumption and platelet kinetics during hemodialysis were quantified in Yorkshire pigs with In-111 labeled platelets. Six anesthetized pigs (20-25 kg) were hemodialyzed at 150 ml/min for 3 hr. All pigs were injected with autologous In-111 labeled platelets (300-420 microCi) 24 hr before dialysis and were systemically heparinized (ACT > 400 sec) before cannulation. Hemodialysis was instituted with a Drake-Willock hemodialysis machine and a hollow fiber dialyzer (Cobe4, 0.6 m2). In vitro sham dialysis was carried out at 150 ml/min for 3 hr with six more dialyzers in a flow-loop with the blood reservoir maintained at 37 degrees C. In vitro thrombogenicity over-estimates (10-fold) in vivo values. In both systems, platelet deposition on dialyzers reached a steady state, suggesting a constant rate of thrombus formation and embolization in the hollow fiber system. The relative thrombus distribution after 3 hr of dialysis was similar in both systems, with adherent thrombi in the entry and exit ports and highest numbers in the midsection of the Hemodialyzer. Biodistribution after 3 hr of dialysis indicated that thrombosis of the Hemodialyzer and arterial and venous traps as well as embolization reduced the platelet pool in the blood and increased platelet emboli in lung, brain, kidneys, and skeletal muscle, as measured by the In-111 labeled platelets.
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quantitation of thrombogenicity of Hemodialyzer with technetium 99m and indium 111 labeled platelets
Nuclear Medicine and Biology, 1993Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Aldo N. Serafini, Gaston Zilleruelo, Kees Ruzius, George N SfakianakisAbstract:Abstract The platelet thrombogenicity of a Hemodialyzer was quantified with 99m Tc- and 111 In-labeled platelets. The platelets collected from blood of Beagle dogs, Yorkshire pigs and human volunteers were labeled with 111 In-tropolone (detergent-free) and 99m Tc-HMPAO. Hemodialysis was performed with a hollow-fiber dialyzer (HFD) in a flow-loop, the temperature of which was maintained at 37 °C, with flow-rates of 7, 150 and 270 mL/min; after dialysis, the HFD radioactivity was measured with an ionization chamber and imaged with a γ-camera. The radioactivity of samples of hollow-fibers taken from the top, middle and bottom of the dialyzer was determined with a γ-counter. The mean values of Hemodialyzer-adherent platelet radioactivity were calculated for both radionuclides. The canine platelets were found to be more thrombogenic than porcine and human platelets. The adhesivity of porcine platelets to the biomaterial (cellulose-acetate) of the dialyzer approximated that of human platelets. The 99m Tc label underestimated the thrombus formation ( P 111 In- and 99m Tc-labeled platelets suggests that both radionuclides could be used for measurement of device-induced thrombogenicity and may provide an estimation of prosthesis-induced thrombogenicity of human platelets from animal studies.
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Quantitation of comparative thrombogenicity of dog, pig, and human platelets in a Hemodialyzer.
Asaio Journal, 1992Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Amaeury Sanchez, Aldo N. Serafini, Raymond Elson, Gaston Zilleruelo, George N SfakianakisAbstract:: Comparative platelet thrombogenicity was quantified with In111 labeled platelets. The platelets collected from the blood of Beagle dogs, Yorkshire pigs, and human volunteers were labeled with detergent free In111 tropolone, and sham hemodialysis (SHD) was performed with a hollow fiber dialyzer in a flow loop at 37 degrees C, with flow rates of 7, 150, and 270 ml/min. After SHD, Hemodialyzer radioactivity was measured with an ionization chamber, gamma counter, and it was imaged with a gamma camera. The mean values of Hemodialyzer-adherent platelet radioactivity were calculated. Canine platelets are more thrombogenic than porcine and human platelets. Quantitation of comparative thrombogenicity with In111 platelets may provide an estimation of prosthesis induced thrombogenicity of human platelets from animal studies.
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Evaluation of comparative thrombogenicity of cellulose-acetate Hemodialyzer in in vitro and in vivo system with radiolabeled platelets
1992 14th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1992Co-Authors: Mansoor Kapadvanjwala, Carlos F. Cavagnaro, George K. Panoutsopoulos, Loukia S. Tourkochoriti, Mrinal K. DewanjeeAbstract:Platelet thrombus in the Hemodialyzer, arterial and venous traps in the extracorporeal circuit was never quantified. Platelet consumption during hemodialysis was measured in Yorkshire pigs with In-111 labeled platelets. Six anesthetized pigs (20–25 kg) were hemodialyzed at 150 ml/min for 3 hours. All pigs were injected with autologous labeled platelets (300–420 μCi), 24 hours prior to dialysis and were systemically heparinized prior to cannulation. Hemodialysis was instituted with a dialyzer pump and hollow-fiber dialyzer (Cobe4,0.6 m2). In vitro sham-dialysis was carried out with 6 more dialyzers in a flow-loop using porcine blood at 150 ml/min. In vitro thrombogenicity was higher (10-fold) than in vivo values, thus overestimates in vivo values. In both systems platelet deposition on dialyzers reached a steady state, suggesting a constant rate of thrombus formation and embolization. The relative thrombus distribution in the dialyzer at 3 hours of dialysis was similar in both systems.
George N Sfakianakis - One of the best experts on this subject based on the ideXlab platform.
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In vitro and in vivo evaluation of the comparative thrombogenicity of cellulose acetate Hemodialyzers with radiolabeled platelets
Asaio Journal, 1994Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Aldo N. Serafini, Raymond Elson, Gaston Zilleruelo, Carlos F. Cavagnaro, George K. Panoutsopoulos, Cleide Suguihara, Shabbir Ezuddin, George N SfakianakisAbstract:: Platelet consumption and platelet kinetics during hemodialysis were quantified in Yorkshire pigs with In-111 labeled platelets. Six anesthetized pigs (20-25 kg) were hemodialyzed at 150 ml/min for 3 hr. All pigs were injected with autologous In-111 labeled platelets (300-420 microCi) 24 hr before dialysis and were systemically heparinized (ACT > 400 sec) before cannulation. Hemodialysis was instituted with a Drake-Willock hemodialysis machine and a hollow fiber dialyzer (Cobe4, 0.6 m2). In vitro sham dialysis was carried out at 150 ml/min for 3 hr with six more dialyzers in a flow-loop with the blood reservoir maintained at 37 degrees C. In vitro thrombogenicity over-estimates (10-fold) in vivo values. In both systems, platelet deposition on dialyzers reached a steady state, suggesting a constant rate of thrombus formation and embolization in the hollow fiber system. The relative thrombus distribution after 3 hr of dialysis was similar in both systems, with adherent thrombi in the entry and exit ports and highest numbers in the midsection of the Hemodialyzer. Biodistribution after 3 hr of dialysis indicated that thrombosis of the Hemodialyzer and arterial and venous traps as well as embolization reduced the platelet pool in the blood and increased platelet emboli in lung, brain, kidneys, and skeletal muscle, as measured by the In-111 labeled platelets.
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quantitation of thrombogenicity of Hemodialyzer with technetium 99m and indium 111 labeled platelets
Nuclear Medicine and Biology, 1993Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Aldo N. Serafini, Gaston Zilleruelo, Kees Ruzius, George N SfakianakisAbstract:Abstract The platelet thrombogenicity of a Hemodialyzer was quantified with 99m Tc- and 111 In-labeled platelets. The platelets collected from blood of Beagle dogs, Yorkshire pigs and human volunteers were labeled with 111 In-tropolone (detergent-free) and 99m Tc-HMPAO. Hemodialysis was performed with a hollow-fiber dialyzer (HFD) in a flow-loop, the temperature of which was maintained at 37 °C, with flow-rates of 7, 150 and 270 mL/min; after dialysis, the HFD radioactivity was measured with an ionization chamber and imaged with a γ-camera. The radioactivity of samples of hollow-fibers taken from the top, middle and bottom of the dialyzer was determined with a γ-counter. The mean values of Hemodialyzer-adherent platelet radioactivity were calculated for both radionuclides. The canine platelets were found to be more thrombogenic than porcine and human platelets. The adhesivity of porcine platelets to the biomaterial (cellulose-acetate) of the dialyzer approximated that of human platelets. The 99m Tc label underestimated the thrombus formation ( P 111 In- and 99m Tc-labeled platelets suggests that both radionuclides could be used for measurement of device-induced thrombogenicity and may provide an estimation of prosthesis-induced thrombogenicity of human platelets from animal studies.
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Quantitation of comparative thrombogenicity of dog, pig, and human platelets in a Hemodialyzer.
Asaio Journal, 1992Co-Authors: Mrinal K. Dewanjee, Mansoor Kapadvanjwala, Amaeury Sanchez, Aldo N. Serafini, Raymond Elson, Gaston Zilleruelo, George N SfakianakisAbstract:: Comparative platelet thrombogenicity was quantified with In111 labeled platelets. The platelets collected from the blood of Beagle dogs, Yorkshire pigs, and human volunteers were labeled with detergent free In111 tropolone, and sham hemodialysis (SHD) was performed with a hollow fiber dialyzer in a flow loop at 37 degrees C, with flow rates of 7, 150, and 270 ml/min. After SHD, Hemodialyzer radioactivity was measured with an ionization chamber, gamma counter, and it was imaged with a gamma camera. The mean values of Hemodialyzer-adherent platelet radioactivity were calculated. Canine platelets are more thrombogenic than porcine and human platelets. Quantitation of comparative thrombogenicity with In111 platelets may provide an estimation of prosthesis induced thrombogenicity of human platelets from animal studies.
Carlo Crepaldi - One of the best experts on this subject based on the ideXlab platform.
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Blood and dialysate flow distributions in hollow-fiber Hemodialyzers analyzed by computerized helical scanning technique.
Journal of the American Society of Nephrology : JASN, 2020Co-Authors: Claudio Ronco, Carlo Crepaldi, Alessandra Brendolan, Mariapia Rodighiero, Marco ScabardiAbstract:The efficiency of a Hemodialyzer is largely dependent on its ability to facilitate diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. This article describes the distribution of the blood and dialysate flows in hollow-fiber Hemodialyzers analyzed with a computerized scanning technique. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation using human blood with hematocrit (Hct) adjusted at 25 and 40%. Sequential images were obtained with a helical scanner in a 1-cm-thick fixed longitudinal section of the dialyzer. Average and regional blood flow velocity and wall shear rates were measured by using the reconstructed imaging sequence. The method allowed the calculation of single-fiber blood flow and single-fiber wall shear rate (SF wSh) in different regions of the Hemodialyzer. In 38 patients on chronic hemodialysis, creatinine and phosphate clearance displayed a significantly negative correlation with Hct (P < 0.05), but this correlation was not found for urea, although a trend toward reduction could be observed. The suggested explanation of this phenomenon is the significant reduction in effective plasma water flow across the Hemodialyzer in presence of a progressive rise in Hct. The second explanation for this phenomenon may be found in the nonhomogeneous distribution of blood flow within the fibers observed at the sequential imaging. This, in fact, could also explain the negative trend observed for urea. At higher Hct levels, single-fiber blood flow velocity and SF wSh were significantly lower in the fibers situated at the periphery of the bundle. At the same time, SF wSh tended to decrease in peripheral fibers, showing a value near half of that observed in the central fibers of the bundle (165 versus 301 s(-1)). A similar technique was used to study the flow distribution in the dialysate compartment in three different types of Hemodialyzers with characteristic dialysate compartment design: (A) standard configuration; (B) space yarns (spacing filaments preventing contact between fibers); and (C) Moiré structure (wave-shaped fibers to prevent contact between adjacent fibers). Clinical sessions of hemodialysis were also carried out to measure blood- and dialysate-side urea clearances in the different Hemodialyzers. Macroscopic and densitometric analysis revealed that flow distribution was most homogeneous in the dialyzer with Moiré structure (type C) and least homogeneous in the standard dialyzer (type A). Space yarns (type B) gave an intermediate dialysate flow distribution. Urea clearance (P < 0.001) increased significantly with types B and C, compared with the standard dialyzer. Type C had the highest clearances, although they were not significantly greater than type B. In conclusion, a significant blood-to-dialysate flow mismatch may occur in hollow-fiber Hemodialyzers due to either uneven blood flow distribution or a dialysate channeling phenomenon external to the fiber bundle. Improvement in dialyzer design may overcome these problems, at least in part.
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Blood and Dialysate Flow Distributions in Hollow-Fiber Hemodialyzers Analyzed by Computerized Helical Scanning Technique
Journal of The American Society of Nephrology, 2020Co-Authors: Claudio Ronco, Carlo Crepaldi, Alessandra Brendolan, Mariapia Rodighiero, Marco ScabardiAbstract:ABSTRACT. The efficiency of a Hemodialyzer is largely dependent on its ability to facilitate diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. This article describes the distribution of the blood and dialysate flows in hollow-fiber Hemodialyzers analyzed with a computerized scanning technique. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation using human blood with hematocrit (Hct) adjusted at 25 and 40%. Sequential images were obtained with a helical scanner in a 1-cm-thick fixed longitudinal section of the dialyzer. Average and regional blood flow velocity and wall shear rates were measured by using the reconstructed imaging sequence. The method allowed the calculation of single-fiber blood flow and single-fiber wall shear rate (SF wSh) in different regions of the Hemodialyzer. In 38 patients on chronic hemodialysis, creatinine and phosphate clearance displayed a significantly negative correlation with Hct ( P versus 301 s −1 ). A similar technique was used to study the flow distribution in the dialysate compartment in three different types of Hemodialyzers with characteristic dialysate compartment design: (A) standard configuration; (B) space yarns (spacing filaments preventing contact between fibers); and (C) Moire structure (wave-shaped fibers to prevent contact between adjacent fibers). Clinical sessions of hemodialysis were also carried out to measure blood- and dialysate-side urea clearances in the different Hemodialyzers. Macroscopic and densitometric analysis revealed that flow distribution was most homogeneous in the dialyzer with Moire structure (type C) and least homogeneous in the standard dialyzer (type A). Space yarns (type B) gave an intermediate dialysate flow distribution. Urea clearance ( P
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effects of novel manufacturing technology on blood and dialysate flow distribution in a new low flux α polysulfone Hemodialyzer
International Journal of Artificial Organs, 2003Co-Authors: F Gastaldon, A Brendolan, Carlo Crepaldi, P Frisone, S Zamboni, Vincenzo Dintini, Sonya Poulin, R Hector, A Granziero, K MartinsAbstract:The main target for low flux Hemodialyzers is an efficient low molecular weight solutes clearance. Such efficiency is largely dependent on the optimization of diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. Thus optimized flow distribution both in the blood and dialysate compartment becomes quintessential for the maximal efficiency of the diffusion process within the Hemodialyzer. The present paper describes the distribution of the blood and dialysate flows in a new low flux polysulfone hollow fiber Hemodialyzer characterized by a specific undulation of the fibers and a new cutting technology of the fibers for an improved micro-flow condition in the blood compartment headers. Twelve Diacap α Polysulfone LO PS 15 (1.5 sqm) (B.Braun Medizintechnologie, Melsungen Germany) were employed for the study. Six were analyzed in vitro and six were studied in vivo. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation utilizing human blood with hematocrit adjusted at 33%. Sequential images were obtained with a helical scanner in a fixed longitudinal section of the dialyzer 1 cm thick. Average and regional blood flow velocities were measured utilizing the reconstructed imaging sequence. The method allowed the calculation of single fiber blood flow (SF Qb) and the mass transfer zone (MTR) definition in digitally subtracted images. The patterns 20- 10 and 40-30 were utilized. The same technology was used to evaluate flow distribution in the dialysate compartment after dye injection in the Hansen's connector. Regional dialysate flow was calculated in central and peripheral sample areas of 1 cm 2 . Six in vivo hemodialysis treatments on patients with end stage renal disease were performed at three different blood flow rates (250-350 and 450 ml/min) in order to measure urea, creatinine and phosphate clearance. Macroscopic and densitometrical analysis revealed that flow distribution was homogeneous in the blood compartment while in the dialysate compartment a slight difference between the peripheral and central regions in terms of flow velocity was observed. This however was not generating channeling phenomena. Urea creatinine and phosphate clearances were remarkably high and so were the Kt/V observed in all sessions, especially in relation to the studied blood flows. In conclusion, a significant blood to dialysate flow match with optimized countercurrent flow condition was observed in the studied hollow fiber Hemodialyzers. Such optimization might be due both to the improved dialyzer design at the level of the blood header and to the specific fiber undulation that prevents dialysate channeling. (Int J Artif Organs 2003; 26: 105-12)
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Hemodialyzer from macro design to membrane nanostructure the case of the fx class of Hemodialyzers
Kidney International, 2002Co-Authors: Claudio Ronco, Sudhir K Bowry, A Brendolan, Carlo Crepaldi, Giuliano Soffiati, Antonio Fortunato, Valeria Bordoni, Alessandro Granziero, Giuseppe Torsello, Giuseppe La GrecaAbstract:Hemodialyzer: From macro-design to membrane nanostructure; the case of the FX-class of Hemodialyzers. Very few innovations have characterized the different components of the Hemodialyzers in the past 20 years. Most improvements have concerned membrane biocompatibility. In this article, we focus our attention on the most recent advances in Hemodialyzer components from the macro design of the unit to the nanostructure of the membrane. For this purpose, we took as an example the FX class of Hemodialyzers (FMC, Bad Homburg, Germany). The studied devices were chosen as an example representing some of the most recent Hemodialyzers and are well suited to describe technical innovations occurring in the field of dialyzer technology. In vitro and in vivo studies were performed to characterize hemodynamic parameters of three models (1.4-1, 8, and 2.2 m 2 ) and to determine membrane permeability, sieving coefficients, and solute clearances. The units were characterized by a relatively high resistance of the blood and dialysate compartments, leading to an increased internal filtration if compared with similar Hemodialyzers of other series. Nevertheless, the flow distribution in both compartments was homogeneous and well balanced. This effect was obtained by the improved blood and dialysate ports design, the increased packing density of the fibers and a reduction of the inner diameter of the fibers from 200 to 180 μm. At the same time, the sieving coefficients for middle-large solutes such as β2 microglobulin and insulin were higher than those observed in standard high flux dialysers. The same effect was noted for the clearance values of these solutes. This was observed in the absence of significant albumin leakage. Theis results were obtained thanks to a new nano-controlled spinning technology applied to the fiber. The innermost layer of the membrane is in fact characterized by a homogeneous porosity, with increased number of pores of large dimension but a sharp cutoff of the membrane excluding albumin losses. In conclusion, new technologies and new diagnostic tools today allow for improvement in Hemodialyzer design from its macro-componets to its nano-structure. The application of nanotechnology to hemodialysis will probably contribute to further developments in Hemodialyzer manufacturing.