Particulates formed in online prepared substitution fluid-Effect of acetic acid cleaning on endotoxin retentive filters.

INTRODUCTION: There is no standard for insoluble particulate matters in dialysate. We evaluated the insoluble particulate matters in online prepared substitution fluid. METHODS: We evaluated particle diameters and constituent elements of particles in online prepared substitution fluid and the final endotoxin retentive filter (ETRF). RESULTS: The measurement results with particles in the online prepared substitution fluid and particles attached to the final ETRF revealed that Ca-containing particles accounted for 11 particles and Si-containing particles accounted for 19 particles of 30 particles detected in the online prepared substitution fluid and the final ETRF. CONCLUSION: We presume that insoluble particulates in online prepared substitution fluid were Ca and Mg precipitated from dialysate and Si precipitated from dialysis water. Even if two ETRFs were connected in series, these particles were formed in the final ETRF.

Comparison of Blood Compatibility in Various Membrane Materials for Continuous Renal Replacement Therapy.

Because hemofilters used for continuous renal replacement therapy contact with blood over a prolonged period during treatments, platelet activation may occur stronger. The purpose of this study is to clarify the blood compatibility in three hemofilters mostly used in Japan. We compared the blood compatibility of the two polysulfone (AEF: Asahi Kasei Medical Co., Tokyo, Japan and SHG: Toray Medical Co., Ltd., Tokyo, Japan) and one polymethylmethacrylate membranes (CH: Toray Medical Co., Ltd.). First, test blood was collected from healthy volunteers. Subsequently, the blood was circulated by a roller pump at the rate of 100 mL/min. We measured the platelet counts and platelet factor 4 (PF4). The platelet counts at 48 h in polymethylmethacrylate membrane were significantly less than that in polysulfone membranes. Levels of the PF4 after the circulation were 978.5 ± 200.0 ng/dL with AEF, 863.0 ± 233.9 ng/dL with SHG and 1780.0 ± 465.1 ng/dL with CH, respectively. Hemofilters with polysulfone membranes showed less platelet activation. It was inferred that the amount of PVP, the smoothness of the membrane surface, and the inner diameter of the hollow fiber affect the blood compatibility in the hemofilter.

Comparison of biocompatibility in polysulfone dialysis membranes with different sterilization.

INTRODUCTION: Polysulfone (PSf) membrane has been widely used for hemodialysis. A few studies have been reported in which a method of sterilization may affect biocompatibility. In this study, the comparison was made between two PSf membranes in order to evaluate the effect of sterilization from the biocompatibility point of view. METHODS: We investigated the biocompatibility of the following two dialyzers, that is, APS-11SA (Asahi Kasei medical Co., Tokyo, Japan), sterilized by gamma-ray irradiation, and RENAK PS-1.0 (Kawasumi laboratories, Tokyo, Japan), sterilized by autoclave. Heparin of 40 units/mL was put in a syringe, and test blood was collected from healthy volunteers. Then, the dialyzer and blood circuit were filled with the test blood. Subsequently, the blood was circulated by a roller pump at the rate of 200 mL/min. We measured the platelet counts, CD41 and CD42b platelet surface markers, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) at 30, 120, and 240 minutes, respectively. FINDINGS: The platelet counts at 30, 120, and 240 minutes decreased significantly from the initiation of blood circulation in both dialyzers. The average beta-TG and PF4 increased from 61.3 ± 22.1 and 17.0 ± 6.4 ng/mL to 680.7 ± 217.1 and 550.7 ± 116.7 ng/mL with APS-11SA and to 454.3 ± 85.6 and 402.0 ± 58.0 ng/mL with RENAK PS-1.0, respectively. The average expression of CD41 and CD42b in APS-11SA and RENAK PS-1.0 was similar. DISCUSSION: There are some reports that the gamma-ray irradiation changes the membrane structure of the PSf membrane, crosslinking the polyvinylpyrrolidone (PVP), a hydrophilic agent, on to the membrane. On the other hand, excess amount of PVP may have been eluted during the rinsing procedure in RENAK PS-1.0 because it was sterilized with autoclave. Because both these factors influenced on our results, APS-11SA and RENAK PS-1.0 dialyzers showed excellent blood compatibility.

Optimal drainage cannula position in dual cannulation for veno-venous extracorporeal membrane oxygenation.

INTRODUCTION:: Recently, the use of veno-venous extracorporeal membrane oxygenation for adult patients with severe acute respiratory failure has increased. We previously investigated the optimal return cannula position; however, the optimal drainage cannula position has not yet been fully clarified. The aim of this study was to investigate the optimal drainage cannula position. METHODS:: Veno-venous extracorporeal membrane oxygenation was performed in four adult goats (mean body weight 59.6 ± 0.6 kg). The position of the drainage cannula was varied among the right atrium, the upper inferior vena cava, and the lower inferior vena cava, whereas the position of the return cannula was fixed in the superior vena cava. The recirculation fraction and arterial oxygen saturation and pressure (SaO2, PaO2) were measured in all drainage cannula positions. RESULTS:: In the lower inferior vena cava drainage cannula position, the recirculation fraction was the lowest. In the lower inferior vena cava, upper inferior vena cava, and right atrium drainage cannula positions at 3 L/min, SaO2 and PaO2 after 20 min were 92.9% ± 4.9% and 75.1 ± 26.0 mm Hg, 99.5% ± 0.5% and 113.8 ± 20.9 mm Hg, and 93.8% ± 6.2% and 91.9 ± 17.7 mm Hg, respectively. CONCLUSION:: With respect to blood oxygenation, the optimal position for the drainage cannula was the upper inferior vena cava. These findings suggested that blood from the superior vena cava, inferior vena cava, and hepatic vein was most efficiently drained in the upper inferior vena cava cannula position.

Novel temporary left ventricular assist system with hydrodynamically levitated bearing pump for bridge to decision: initial preclinical assessment in a goat model.

The management of heart failure patients presenting in a moribund state remains challenging, despite significant advances in the field of ventricular assist systems. Bridge to decision involves using temporary devices to stabilize the hemodynamic state of such patients while further assessment is performed and a decision can be made regarding patient management. We developed a new temporary left ventricular assist system employing a disposable centrifugal pump with a hydrodynamically levitated bearing. We used three adult goats (body weight, 58-68 kg) to investigate the 30-day performance and hemocompatibility of the newly developed left ventricular assist system, which included the pump, inflow and outflow cannulas, the extracorporeal circuit, and connectors. Hemodynamic, hematologic, and blood chemistry measurements were investigated as well as end-organ effect on necropsy. All goats survived for 30 days in good general condition. The blood pump was operated at a rotational speed of 3000-4500 rpm and a mean pump flow of 3.2 ± 0.6 L min. Excess hemolysis, observed in one goat, was due to the inadequate increase in pump rotational speed in response to drainage insufficiency caused by continuous contact of the inflow cannula tip with the left ventricular septal wall in the early days after surgery. At necropsy, no thrombus was noted in the pump, and no damage caused by mechanical contact was found on the bearing. The newly developed temporary left ventricular assist system using a disposable centrifugal pump with hydrodynamic bearing demonstrated consistent and satisfactory hemodynamic performance and hemocompatibility in the goat model.

Effects of feeding state on anticoagulation in adult goats treated with warfarin.

For the continued development of improved mechanical circulatory systems, longer term evaluation of new devices in animal model experiments may be critical. The effects of anticoagulants in adult goats have not been well studied. We assessed the effects of oral warfarin in three adult goats during fasting or after feeding. The goats [weighing 57.8 ± 8.1 kg (53.0-67.2 kg)] were administered warfarin orally beginning at a dose of 5 mg/day and then increasing to 10, 20, 40, and 60 mg every 2 weeks. One goat (receiving 10 mg/day warfarin) was killed on day 27 because of the inability to stand. After administration of 60 mg warfarin, the remaining goat received no warfarin for 4 days to return to coagulated state. The goats were then fasted and treated with 40 mg warfarin. During warfarin administration, both goats required a dose of 60 mg/day to achieve International Normalized Ratios (INRs) of approximately 2.5; however, when, the animals were in the fasted condition, precipitous extension of INR was observed in 5 days. After resuming feeding, the INR was reduced to the proper range. We showed the tendency that warfarin therapy in goats required higher doses than the doses administered to human patients and that the effects of therapy were related to the feeding state. The results of this study provide important information for development of anticoagulation protocols to assess mechanical circulatory support devices for long-term use in preclinical examination.

Impact of bypass flow rate and catheter position in veno-venous extracorporeal membrane oxygenation on gas exchange in vivo.

The clinical use of veno-venous extracorporeal membrane oxygenation (VVECMO) in adult patients with respiratory failure is rapidly increasing. However, recirculation of blood oxygenated by ECMO back into the circuit may occur in VVECMO, resulting in insufficient oxygenation. The cannula position and bypass flow rate are two major factors influencing recirculation, but the relationship and ideal configuration of these factors are not fully understood. In the present study, we attempted to clarify these parameters for effective gas exchange. VVECMO was performed in eight adult goats under general anesthesia. The position of the drainage cannula was fixed in the inferior vena cava (IVC), but the return cannula position was varied between the IVC, right atrium (RA), and superior vena cava (SVC). At each position, the recirculation rates calculated, and the adequacy of oxygen delivery by ECMO in supplying systemic oxygen demand was assessed by measuring the arterial oxygen saturation (SaO2) and pressure (PaO2). Although the recirculation rates increased as the bypass flow rates increased, SaO2 and PaO2 also increased in any position of return cannula. The recirculation rates and PaO2 were 27 ± 2% and 162 ± 16 mmHg, 36 ± 6% and 139 ± 11 mmHg, and 63 ± 6% and 77 ± 9 mmHg in the SVC, RA and IVC position at 4 L/min respectively. In conclusion, the best return cannula position was the SVC, and a high bypass flow rate was advantageous for effective oxygenation. Both the bypass flow rates and cannula position must be considered to achieve effective oxygenation.