Filtrate Circuit Research Articles

Mixed Mode Global Filtration System using VDIBA

By virtue of voltage differencing inverting buffer amplifier (VDIBA), in the above paper offers a mixed mode (MM) numerous source sole output global filtration system. Without changing its circuit configuration, all filtration system functions, including low-pass, band-pass, band-reject, high-pass, as well as all-pass filtration system features, could be accomplished. With the help of its trans-conductance parameter, the tuned rate could be separately adjusted. The filtration circuit has low sensitivity figures and doesn't have to match components. By demonstrating the modeling data achieved utilizing Tanner EDA tool as well as 180nm new tech settings, the functionality of the suggested filter is confirmed.

1340. The Effect of Continuous Renal Replacement Therapy on Body Temperature in Patients with and without Infection

BackgroundSepsis frequently leads to acute kidney injury. In severe cases, patients may require continuous renal replacement therapy (CRRT) which involves placement of a dialysis catheter and an extracorporeal blood filtration circuit. CRRT is commonly considered to “mask” fever, though this phenomenon has not been investigated.MethodsWe queried an institutional database of all patients on CRRT from 2007 to 2015 for inpatient temperature data and antibiotic administration records. Receipts of piperacillin–tazobactam, a carbapenem, or a third or fourth-generation cephalosporin, indicating a serious infection, were considered intervention arm. We analyzed temperatures recorded in the intensive care unit before, during, and after CRRT. Patients were divided into groups that did not receive antibiotics as well as those who did. Temperature data were Winsorized to correct for outliers. We also performed descriptive statistics for each group.ResultsThere were 237,988 temperature readings for 1,568 ICU patients on CRRT. 1,153 patients received broad-spectrum antibiotics in ICU. In patients who received antibiotics in ICU and were presumed to have an infection, the mean temperature was 37.2°C prior to initiation of CRRT, 36.8°C while on CRRT, and 37.2°C following discontinuation of CRRT. In the 415 patients who did not receive IV antibiotics, the mean temperature was 36.9°C prior to initiation of CRRT, 36.6°C while on CRRT, and 37.0°C following discontinuation of CRRT. During each of the periods before, during, and after CRRT, patients who received antibiotics had significantly higher temperatures than those who did not (P < 0.001). Patients receiving antibiotics were generally younger (mean 60 years vs. 64 years, P < 0.001), had longer ICU stays (mean 29 days vs. 12 days, P < 0.001) and spent more time being ventilated (mean 23 days vs. 7 days, P < 0.001). The mean SOFA score on day one was similar (mean 11.1 in the antibiotic group and 10.5 in the other group).ConclusionThis investigation suggests that patients have slightly lower temperatures while on CRRT, by on average less than half a degree. A similar effect is seen in both patients with infections as well as those without. Further work will be needed to determine what constitutes a true febrile response in this population.Disclosures All authors: No reported disclosures.

Complex Cardiac Surgery on Patients with a Body Weight of Less Than 5 kg without Donor Blood Transfusion

Performing safe cardiac surgery in neonates or infants whose parents are Jehovah's Witnesses is only possible in a coordinated team approach. An unconditional prerequisite is a cardiopulmonary bypass (CPB) circuit with a very low priming volume to minimize hemodilution. In the past decade, we have developed a functional blood-sparing approach at our institution. The extracorporeal circuit was miniaturized. This had to be recently adapted, faced with a challenge associated with the switch to high-volume crystalloid cardioplegia. A filtration circuit was added. Here, we report an open heart surgery on three consecutive children of Jehovah's Witness parents with a body weight of 2.7, 4.5, and 4.8 kg, respectively. Procedures consisted of one arterial switch operation and two repairs of complete atrioventricular septal defects. Our static priming volume of less than 90 mL resulted in a nadir hematocrit during CPB of 27.7% (Hb 8.9 g/dL) in a patient which happened to have the lowest body weight of 2.7 kg. The two other patients had their lowest hematocrit at 31.4% (Hb 10.2 g/dL). The three children could be treated without any kind of transfusion of blood which had left the circulation or its extensions, in accordance with the parents' wishes, and enjoy favorable outcomes without transfusion of blood products during their entire hospital stay.

An Observation of Very Low Frequency (VLF) Electromagnetic Waves Generated by Lightning Strikes via RockSat-X

In an attempt to observe how very low frequency (VLF) signals from lightning discharges vary as a function of altitude, a sounding rocket payload was built and launched via the Colorado Space Grant Consortium’s RockSat-X program. The main components of the payload consisted of three magnetic field antennas, two pairs of electric field plate antennas, an amplification and filtration circuit board, and two microSD cards interfaced with high performance multi-core microcontrollers for data storage. Despite a flight anomaly preventing the retrieval of the stored data, low resolution telemetry data from flight shows the expected presence power line interference.

A percutaneous aortic device for cerebral embolic protection during cardiovascular intervention

Embolic stroke is a major cause of morbidity in aortic and cardiac interventional procedures. Although cerebral embolic protection devices have been developed for carotid interventions and for open heart surgery, a percutaneous device for cerebral embolic protection during aortic and cardiac interventions would be desirable. The Embrella Embolic Deflector (Embrella Cardiovascular Inc, Wayne, Pa) is a percutaneously placed embolic protection device, inserted by a 6F access in the pig's right forelimb, and deployed in the aorta, covering the brachiocephalic vessel origins. The device functions by deflecting embolic debris downstream in the aortic circulation. A swine model (n = 3) was developed for testing the deployment, retrieval, and efficacy of the device using a carotid filtration circuit for collection of emboli. Human atheromatous material was prepared as embolization particles with diameters between 150 and 600 μm. Deflection efficiency of the device was calculated by comparing numbers of embolic particles in the carotid circulation during protected and unprotected injections. The device was reliably deployed, positioned, and retrieved (n = 24). There was no significant drop in blood pressure across the membrane of the device to suggest reduction of cerebral blood flow. The device did not become occluded by embolic debris despite an embolic load many times that encountered in the clinical situation. Particles entering the carotid circulation after aortic injection of emboli were reduced from 19% of total (unprotected) to 1.3% (protected, P < .0001), with 98.7% of all injected particles being deflected downstream. There was no evidence of arterial injury related to the device found at necropsy. The Embrella Embolic Deflector performs safely and reliably in the swine model of human atheroembolism. It effectively deflects almost all emboli downstream, away from the carotid circulation. The deflector shows promise as an aortic embolic protection device and merits further investigation.

Improved interval-fuzzy quadratic programming for management of filters in a fluid power system under uncertainty

An improved mathematic model of management of filters in a fluid power system (FPS) under uncertainty was developed in this article based on the former hybrid optimization method. The model integrated the interval-fuzzy quadratic programming model into an improved model of contaminant control for the selection of filters finenesses, the estimation of service life of pumps, and replacement strategies of filters in an FPS under uncertainty. The fuzzy quadratic optimization approach was used in the model to handle the uncertainties existing not only in the contaminant holding capacity, but also in the contamination level and contaminant sensitivity. The integrated model has been applied in a case of selecting filter fineness and planning allocation and replacement strategies under uncertainty for an FPS with bypass filtration circuit. All of the scenarios with available filter fineness have been examined. The generated decision alternatives can help decision makers to identify desired policies for contamination control under various total costs, satisfaction degrees, and system-failure risks under different contaminant ingression/generation rates.

Magnetic Fluorescent Microparticles as Markers for Particle Transfer in Extracorporeal Blood Purification

The microspheres-based detoxification system (MDS) is a combined membrane-adsorption system for extracorporeal blood purification in which adsorbent microparticles are recirculated in an extracorporeal filtrate circuit. Because the plasma filter represents the only barrier between the adsorbents and the patient's blood, there is the potential risk of particle entrance into the patient in case of a membrane rupture. To guarantee first fault safety of the system required for clinical application, magnetic fluorescent microparticles are added as markers to the adsorbent circuit. Detection of these particles in the venous blood line results in immediate shutdown of the pumps. Magnetic beads were functionalized with cresyl violet and tested with an in vitro setup of the particle detector to assess the detection limit in different matrices (water versus blood) as well as the influence of flow rate and particle size on the signal. In addition, biocompatibility and influence of sterilization on the performance of the particles were assessed. Functionalization of the magnetic particles with cresyl violet yielded fluorescent particles that were stable at 4 degrees C for at least 12 months. No leakage of dye was detectable, and the particles were neither cytotoxic nor mutagenic. The particles could be steam sterilized without significant loss in fluorescence intensity. With an in vitro setup of the particle detector, 0.1 mg and 5 mg of particles were reproducibly detectable in water and blood, respectively.

Efficient Adsorption of Tumor Necrosis Factor with an in vitro Set-Up of the Microspheres-Based Detoxification System

Background: The Microsperes-Based Detoxification System (MDS) represents a flexible therapeutic option for various diseases, depending on the specificity of the adsorbents applied. A potential application of the MDS is the supportive therapy of sepsis. Methods: Microadsorbents for tumor necrosis factor (TNF) were prepared by immobilization of anti-TNF antibodies on cellulose (1–10 µm) and applied in an experimental set-up using a pool of human plasma (1 liter) spiked with TNF (800 pg/ml) and its soluble receptors (1,000 pg/ml each). Removal of TNF was compared using a plasma filter and the albumin-permeable filter Albuflow. Results: Addition of 4 (2) g of adsorbent to the filtrate circuit reduced TNF concentrations in the pool by 80% (64%). Removal rates did not differ significantly for the different filters. TNF adsorption was not influenced by the presence of excess TNF receptors. Conclusions: Concentrations of mediators can be efficiently modulated with the MDS using small quantities of specific adsorbents.

New Methods for Hemoglobin Detection in a Microparticle-Plasma Suspension

In the extracorporeal adsorption system, MDS (Microspheres based Detoxification System), micro-adsorbent particles measuring 1-25 micrometers circulate in a filtrate circuit for highly specific blood purification/adsorption. The MDS circuit containing the adsorbent microparticles is linked to the patient's blood line by a hollow fiber plasma filter. When the transmembrane pressure or the shear forces due to the red blood cells in the hollow fiber filter are too high, they can be damaged and hemoglobin will be released. In order to detect free hemoglobin (fHb) by optical means, we have designed a new flow-dynamic filter system, placed in the microadsorbent circuit for continuous separation of microparticles from the filtrate. In the flow dynamic filter, we use a high velocity liquid vortex to remove sedimentation and particle plugs on the filter membrane. In our investigations, 3 and 8 micron cellulose nitrate filter membranes for particle separation are used. The obtained particle free bypass filtrate flow rates are typically 0.5 and 0.8 ml/min respectively. The typical sensitivity for fHb detection by the applied noninvasive optical method is 0.15 g/dL. Medical safety regulations require a fail-safe mechanism for fHb detection which monitors the bypass filtrate flow in the flowdynamic filter and shuts down the system in case of membrane occlusion. The bypass filtrate flow is monitored by periodically occluding and releasing the bypass line by means of a clamp. The resulting back pressure profile gives information about the actual filtration rate. This safety principle was proven by statistical analysis and shows its clear functionality.

Detection of Fluorescently Labeled Microparticles in Blood

Background: A microsphere-based detoxification system is an adsorption system, whereby microadsorbent particles having diameters of 1–20 µm circulate in an extracorporeal filtrate circle. A thin-wall hollow-fiber membrane filter separates the microparticle-plasma suspension from the bloodstream. For patient safety, it is necessary to have a means to detect membrane ruptures that could lead to a release of microparticles into the patient’s bloodstream. Methods: An optical detection system was developed to monitor the venous bloodstream for the presence of microparticles from the filtrate circuit. For detection purposes, cellulose microspheres, both ferromagnetic and fluorescence labeled, were included with the microsphere adsorbant particles. In the case of a membrane rupture, the labeled particles would also be released into the bloodstream. By illuminating a small volume of blood with an excitation wavelength (590 nm) of the fluorescence marker, the particles can be detected by their emission light at 620 nm. The detector sensitivity is increased by collecting the ferromagnetic and fluorescently labeled microparticles using a magnetic trap. The efficiency of magnetic trap arrangements was tested by adjusting the magnet placements. Results: In vitro experiments were performed by pumping whole blood and labeled microparticles through the fluorescence detector. The efficiency of a magnetic trap arrangement was determined. With an optimal trap setup, 5–10 µl of labeled microparticles can be clearly detected in streaming whole blood. Conclusion: An easy to handle microparticle detector was developed, ready for use in particle based blood detoxification systems. The microparticle detection system fulfills the medical and technical requirements to bring the MDS into clinical tests.

Keeping the Circuit Open: Lessons from the Lab

Background: Hemofiltration circuits generally require anticoagulation to prevent the membrane from clotting. Understanding the mechanisms involved in premature clotting of the filtration circuit is useful to optimize anticoagulation and maintain filter patency. Aims: To discuss research performed at our institution which throws light on the causes of premature clotting of the hemofilter, and to highlight our approach to anticoagulation. Discussion: Premature clotting of the circuit is related to low baseline levels of antithrombin III (AT-III), heparin co-factor II and tissue factor pathway inhibitor. Clotting is preceded by a precipitous rise in thrombin-antithrombin complexes, suggesting thrombin generation. Our standard anticoagulant is unfractionated heparin, where the primary mode of action is potentiation of endogenous AT-III. However, AT-III levels are diminished in sepsis and other causes of systemic inflammation. To supplement or prevent consumption of AT-III we use fresh frozen plasma or aprotinin (as cheaper alternatives to AT-III) in situations where filter life span is limited and mechanical obstruction has been excluded. Anticoagulation can be managed in heparin-induced thrombocytopenic patients with danaparoid, prostaglandins and/or predilution.