Priming Volume Research Articles

Reducing the prime cardiopulmonary bypass volume during paediatric cardiac surgery.

Despite technological advances, the use of homologous blood to prime the cardiopulmonary bypass (CPB) circuits of infants under 10kg remains common. However, such rapid massive transfusion may increase post-CPB morbidity. We retrospectively included consecutive patients weighing 2.3-10kg who underwent cardiac surgery under CPB. Patients were divided into two groups based on their priming volumes: low priming volume (LPV) (below the median volume) or high priming volume (HPV) (the median volume or above). The study included 208 patients, of whom 104 had priming volumes below the median [37.9 (28.4-51.7) mL/kg] and 104 had at least the median volume. We recorded positive correlations between the priming volume, on the one hand, and the peak creatinine and CRP levels within 5days postoperatively, the duration of intensive care unit (ICU) stay, and the mechanical ventilation time, on the other. A relationship was also observed between a higher median priming volume and the need for renal replacement therapy in the ICU and mediastinitis. Although the differences in priming volume between the twogroups were small, they significantly influenced the postoperative complications. Perfusionists should seek to limit the priming volume to reduce the post-CPB inflammatory response, the duration of ICU stay, and possibly the risk of mediastinitis.

The influence of membrane fiber arrangement on gas exchange in blood oxygenators: A combined numerical and experimental analysis

Oxygenators take over lung function in the event of severe lung injuries by exchanging gas into the blood stream using hollow fiber membrane mats. A central limitation of oxygenators is their large foreign surface area and priming volume, which cause blood damage.Thus, gas exchange efficiency needs to be improved through an understanding of the interaction between fiber arrangement and blood flow directions. This has only been investigated in two dimensional or simplified non-realistic fiber bundles. The aim of this study was to quantify gas exchange in realistic 3D fiber bundles.We performed three dimensional micro scale CFD simulations of different realistic fiber arrangements and flow directions that we validated in corresponding test oxygenators using porcine blood.Fiber-configurations influence gas transfer by factor 2, with highest transfer rates for blood flowing in circumferential direction, and lowest for longitudinal direction in wound oxygenators. The CFD model correlates with the experiments with an R2 = 0.88.For the first time, the configuration of realistic 3D fiber bundles was proven to strongly influence gas transfer in oxygenators, in simulations and experiments. The CFD model serves for investigation of further configurations and to derive transfer coefficients for full scale oxygenators.

Development of a low priming volume hydrodynamic test bench for isolated ex vivo perfusion of small animal lungs

Development of a low priming volume hydrodynamic test bench for isolated ex vivo perfusion of small animal lungs

Can a low prime volume arterial filter be used as an alternative for a venous bubble trap in minimal extracorporeal circulation? An in vitro investigation.

During cardiac surgery the use of a minimal extracorporeal circulation (MiECC) system may reduce the adverse effects for the patient. This is probably caused by reduced inflammation and hemodilution. For the use of a MiECC circuit, a venous bubble trap (VBT) is warranted for safety reasons. The aim of this study was to assess if an arterial filter with a small prime volume has the same (or better) air removal capacities as a VBT in a MiECC circuit and subsequentially may be used as an alternative. In an in vitro study, air removal properties were compared between the arterial filter and three VBT's on the market, VBT160 (Getinge), VBT 8 (LivaNova and VARD (Medtronic). In a MiECC circuit, the filter devices were placed in a venous position and challenged with massive and micro air. Gaseous microemboli (GME) were measured with a bubble counter proximal and distal of the VBT device. More than 99.9 % of the air was removed after a bolus air challenge by all VBT's. Both the VARD and the AF100 showed better GME removal properties (not significant for the AF100) compared to the other devices. All filters showed GME generation after a challenge with massive air. Compared to the other filters, only the VARD showed no passing of larger bubbles when a volume of 50mL of air was present in the filter. The AF100 seems to be a safe and low prime alternative for use in a MiECC system as a venous air trap. A word of caution, placement of the AF100 arterial filter in the venous line is off label use.

The role of fetal hemoglobin in the artificial placenta: A premature ovine model.

A radical paradigm shift in the treatment of premature infants failing conventional treatment is to recreate fetal physiology using an extracorporeal Artificial Placenta (AP). The aim of this study is to evaluate the effects of changing fetal hemoglobin percent (HbF%) on physiology and circuit function during AP support in an ovine model. Extremely premature lambs (n = 5) were delivered by cesarean section at 117-121 d estimated gestational age (EGA) (term = 145d), weighing 2.5 ± 0.35kg. Lambs were cannulated using 10-14Fr cannulae for drainage via the right jugular vein and reinfusion via the umbilical vein. Lambs were intubated and lungs were filled with perfluorodecalin to a meniscus with a pressure of 5-8cm H2O. The first option for transfusion was fetal whole blood from twins followed by maternal red blood cells. Arterial blood gases were used to titrate AP support to maintain fetal blood gas values. The mean survival time on circuit was 119.6 ± 39.5h. Hemodynamic parameters and lactate were stable throughout. As more adult blood transfusions were given to maintain hemoglobin at 10mg/dL, the HbF% declined, reaching 40% by post operative day 7. The HbF% was inversely proportional to flow rates as higher flows were required to maintain adequate oxygen saturation and perfusion. Transfusion of adult blood led to decreased fetal hemoglobin concentration during AP support. The HbF% was inversely proportional to flow rates. Future directions include strategies to decrease the priming volume and establishing a fetal blood bank to have blood rich in HbF.

A novel approach to retrograde autologous priming for infant, pediatric and adult populations undergoing congenital heart surgery.

Retrograde Autologous Priming (RAP) of cardiopulmonary bypass (CPB) circuits is an effective way to reduce prime volume, commonly through the transfer of prime into separate reservoirs or circuit manipulation. We describe a simple and safe technique for RAP without the need for any circuit modifications or manipulations. For this technique, a separate roller pump for ultrafiltration (UF) is used. After adequate heparinization and arterial cannulation, the UF pump is initiated slowly, removing prime through the effluent of the UF, replacing with the patient's blood from the aortic cannula. Once the arterial line and UF circuit are autologous primed, the arterial head displaces reservoir crystalloid toward the UF circuit at a flow rate equal to the UF pump, displacing the crystalloid prime with blood from the UF circuit, autologous priming the boot and oxygenator with blood, crystalloid again being removed by the effluent. After venous cannulation, the venous line prime is replaced with autologous blood, the crystalloid removed by the effluent of the UF circuit via the arterial head. During RAP, if the patient becomes hypovolemic, either autologous volume is transfused back to the patient, or CPB is initiated, without the need for circuitry modifications. The patient population in this sample consisted of 63 patients ranging between 6.1kg and 115.6kg. The smaller the patient, the less blood volume available for RAP and therefore the less prime volume able to be removed. Overall percent removal increases as our patients size increases compared to total circuit volume. This RAP technique is a safe and effective way to achieve a standardized asanguinous prime for many regardless of patient or circuit size in the absence of contraindications such as low starting hematocrit, emergency surgery or physiologic instability. Most importantly, this potentially reduces the amount of hemodilution patients see from CPB initiation and therefore the lowest nadir hematocrit and consequently the amount of required homologous blood products needed during surgery.

MODIFIED ULTRAFILTRATION IMPROVES LUNG MECHANICS IN CONGENITAL CARDIAC SURGERY - A FACT OR FUTILE: A PROSPECTIVE, OBSERVATIONAL, SINGLE-CENTER STUDY

Objective: Cardiac surgeries involving cardiopulmonary bypass (CPB) can have adverse effects on patients, potentially increasing morbidity. In infants who possess lower blood volume and are exposed to the more artificial surface and larger prime volumes of the CPB, the harmful effects can be significant. Several studies have indicated that modified ultrafiltration (MUF) may yield beneficial effects in cardiac surgery by reducing inflammatory markers, improving hemodynamics, and decreasing excess body water. Our study seeks to evaluate the impact of MUF on pulmonary mechanics in infants undergoing cardiac surgeries on CPB. Methods: This prospective, observational, single-center study was conducted on 56 infants with congenital heart disease, who underwent cardiac surgery, followed by CPB, were included in this study. The primary outcomes were oxygen saturation (SPO2), hemoglobin (Hb), peak inspiratory pressure (Ppeak), and plateau pressure (Pplat). The secondary outcomes were systolic and diastolic invasive blood pressures (IBPs), mean arterial pressure (MAP), mean airway pressure (Pmean), static lung compliance (C-stat), dynamic lung compliance (C-dyn), expiratory resistance (Re), and work of breathing (WOB). Results: A statistically significant increase in SPO2 (98.7 vs. 99.1), Hb (8.3 vs. 13.3), IBPsystolic (85 vs. 90), IBPdiastolic (56 vs. 61.4), and MAP (66.4 vs. 73.2) was observed in congenital cardiac surgery and CPB patients after MUF (all p<0.05). A statistically significant post-procedural decline in Ppeak (18.8 vs. 18.3), Pplat (18.4 vs. 18.1), Re (79.8 vs. 78), and WOB (1.4 vs. 1.3) was also observed (all p<0.05). However, no significant pre-procedural versus post-procedural differences were observed in Pmean, C-stat, and C-dyn (all p>0.05). Conclusion: MUF effectively improved lung mechanics, oxygen saturation, myocardial contractility, hematocrit, and hemodynamics, and minimized the blood transfusion requirement after CPB in infants with congenital heart disease. Future studies should reinvestigate these outcomes with a larger sample size for an extended follow-up duration.

Impact of Hemoglobin Level in Ex Vivo Heart Perfusion on Donation After Circulatory Death Hearts: A Juvenile Porcine Experimental Model.

Ex vivo heart perfusion (EVHP) of donation after circulatory death (DCD) hearts has become an effective strategy in adults; however, the small circulating volume in pediatrics poses the challenge of a low-hemoglobin (Hb) perfusate. We aimed to determine the impact of perfusate Hb levels during EVHP on DCD hearts using a juvenile porcine model. Sixteen DCD piglet hearts (11-14 kg) were reperfused for 4 h in unloaded mode followed by working mode. Metabolism, cardiac function, and cell damage were compared between the low-Hb (Hb, 5.0-5.9 g/dL; n = 8) and control (Hb, 7.5-8.4 g/dL; n = 8) groups. Between-group differences were evaluated using 2-sample t -tests or Fisher's Exact tests. During unloaded mode, the low-Hb group showed lower myocardial oxygen consumption ( P < 0.001), a higher arterial lactate level ( P = 0.001), and worse systolic ventricular function ( P < 0.001). During working mode, the low-Hb group had a lower cardiac output (mean, 71% versus 106% of normal cardiac output, P = 0.010) and a higher arterial lactate level ( P = 0.031). Adjusted cardiac troponin-I ( P = 0.112) did not differ between the groups. Morphological myocyte injury in the left ventricle was more severe in the low-Hb group ( P = 0.028). Low-Hb perfusate with inadequate oxygen delivery induced anaerobic metabolism, resulting in suboptimal DCD heart recovery and declined cardiac function. Arranging an optimal perfusate is crucial to organ protection, and further endeavors to refine the priming volume of EVHP or the transfusion strategy are required.

Medical Mobile Application for The Management of Heart-Lung Machine during Cardiac Surgery

The goal of this work is to construct a mobile application device that has a wide variety of functions which has clinical planning and decision making for heart-lung machine controlling and to assess the users’ level of satisfaction. The app was constructed according to the steps of design, algorithm, and validation, which is based on the ionic framework. The levels of satisfaction with the developed mobile app among 20 perfusionists were assessed by a questionnaire. The project researchers have officially assigned this medical mobile application with the name is Perfusion Assistant app. that can be accessed and used effectively cross platform on iOS and Android. The application is comprised of 5 main categories which includes: a perfusion calculator, myocardial protection chart, drugs details, priming solution, and parameters values. This finding shown that all cardiovascular parameters did not significant differ from Perfusion Assistant app. when compared to manual calculation. User’s satisfaction was at 3.64 ± 0.76 in the first evaluation. After modification with feedback from experts, the satisfaction of this application was evaluated with a 4.13 ± 0.56. Thereby, Perfusion Assistant app. is an application designed in clinical planning and decision of heart-lung machine controlling for perfusionists and medical staff that work in an opened heart surgery arena. Perfusion Assistant app. offers a variety of calculations related to cardiopulmonary bypass including blood flow rate, systemic vascular resistant, priming volume, and predicted hematocrit. Furthermore, Perfusion Assistant app. provides a quick, easy access, and real-time application for cardiopulmonary bypass that user’s satisfaction was a good level.

Fine tuning for totally endoscopic mitral valve surgery: ERAS applications.

One of the philosophies of minimally invasive mitral surgery is to enhance recovery after surgery (ERAS). Beyond surgical applications, ERAS applications provide a complementary approach to optimize postoperative course and discharge. In this report, we aim to present institutional protocol for ERAS and its results in patients who underwent totally endoscopic mitral valve surgery (TEMVS). Between 2021 and 2023, totally 113 patients who underwent TEMVS were included in this study. TEMVS was performed by peripheral cannulation and 3D endoscopic technique. As a dedicated team, institutional ERAS protocols which are used are listed above: (1) Education; operative course, cessation of smoking and alcohol. (2) Anemia; diagnostic evaluation and its treatment by iv iron. (3) Optimization of blood glucose; checking of HbA1c and control of hyperglycemia. (4) Rehabilitation; Physical and pulmonary rehabilitation. (5) Anxiety and Analgesia treatment. (6) Blood Conservation techniques; Antifibrinolytic, acute normovolemic hemodilution, less priming volume, mini-incision, meticulous surgery by 3D endoscope. (7) Postoperative; early extubation, prevention of nausea, aggressive analgesia, early mobilization, early removal of tubes. (8) Restrictive transfusion strategy. (9) Early discharge. The mean age was 54.7 years, and 56% was female. The rate of iv iron therapy for anemia was 26.5%. Mitral repair was performed in 58.4% of the cases. The repair rate of degenerative mitral valve was 96.9%. Of all, 68.1% did not have any red packed cells and 15.9% had only one unit. Ninety-five patients (90.2%) did not have any unit of fresh frozen plasma. The median extubation time was 7 h. On the postoperative first day, 96% of foley catheters, 87% of all central venous catheter and 93% of all drainage tubes are removed. The rates of respiratory, infectious, and renal complications were 9%, 3.5%, 3.4% respectively. The median ICU, and hospital stays were 1 and 5 days respectively. There was only one mortality in the early postoperative period. Totally endoscopic mitral valve surgery provides minimal surgical trauma. By the addition of well-established and nurse-based ERAS protocols, complication and transfusion rates can be decreased, early recovery and discharge can be provided.

Gamma prime formation in nickel-based superalloy IN738LC manufactured by laser powder bed fusion

Complex components for high-temperature gas turbine applications require materials that offer a combination of excellent high-temperature strength and oxidation resistance. Nickel-based superalloys with high gamma prime (γ´) volume fractions are particularly suited for these applications, especially combined with additive manufacturing for intricate geometries. Despite the complex thermal history that these materials experience during laser powder bed fusion (LPBF) processing, γ´formation is suppressed when manufacturing IN738LC, which has a medium equilibrium γ´content of about 40–50 vol%. This study follows γ´formation in LPBF IN738LC during subsequent annealing treatments at temperatures ranging from 745 °C to 865 °C, creating an experimentally determined TTT (temperature-time-transformation) diagram. This diagram is largely based on scanning electron microscopy (SEM) imaging supported by Vickers hardness measurements and scanning transmission electron microscopy (STEM) bright field imaging. Atom probe tomography (APT) of the as-built material indicated nm-sized regions depleted in Cr and enriched in Ni, Al, and Ti, but show no characteristic superlattice patterns in TEM diffraction. APT and TEM diffraction analysis of material annealed at 850 °C for 3 min confirmed the presence of the γ´phase but indicated that γ´had formed through spinodal decomposition instead of precipitation.

Effect of Retrograde Autologous Priming on Coagulation Assessed by Rotation Thromboelastometry in Patients Undergoing Valvular Cardiac Surgery

ObjectivesTo investigate the effect of retrograde autologous priming (RAP) on coagulation function using rotation thromboelastometry (ROTEM) in patients undergoing valvular heart surgery. DesignProspective, randomized, patient- and outcome assessor-blinded study. SettingSingle-center university hospital. ParticipantsPatients aged 20 years or more undergoing valvular heart surgery. Interventions104 patients were allocated to the RAP or control group (1:1 ratio). In the RAP group, the prime was displaced into the collection bag before bypass initiation. ROTEM was performed at the induction of anesthesia, at the beginning of rewarming, and after the reversal of heparinization. Allogeneic plasma products and platelet concentrates were transfused according to ROTEM-based algorithms. Measurements and Main ResultsAn average volume of 635 ± 114 mL was removed using RAP (from the 1,600 mL initial prime volume). The hematocrit 10 min after CPB was 24.7 ± 3.5% in the control group and 26.1 ± 4.1% in the RAP group (P=0.330). ROTEM including EXTEM, INTEM, and FIBTEM showed prolonged clotting time and decreased maximal clot firmness after CPB in both groups, without intergroup differences. The number of patients who received intraoperative erythrocyte (27% vs. 25%, control vs. RAP, P=0.823), fresh frozen plasma (14% vs. 8%, control vs. RAP, P=0.339), cryoprecipitate (21% vs. 12%, control vs. RAP, P=0.185), or platelet concentrate transfusion (19% vs. 12%, control vs. RAP, P=0.277) did not differ between the groups. ConclusionsCPB induced impaired coagulation function on ROTEM. However, RAP did not improve coagulation function when compared with conventional priming in patients undergoing valvular heart surgery.

Engineering metal-covalent organic framework-based hybrid oxygenation membranes for facilitated blood-gas exchange

Oxygenation membranes operate as indirectly contacting barriers between blood and gas in extracorporeal membrane oxygenation (ECMO), improving oxygenation and removing carbon dioxide from blood. However, the low gas exchange efficiency of the current poly (4-methyl-1-pentene) (PMP) artificial lung membrane results in a high prime volume. Facilitated transport membrane is a fascinating strategy to construct high-performance membranes for blood-gas exchange. This study put forward hybrid strategy by using metal-covalent organic frameworks (MCOFs) to construct facilitated transport membrane of PMP flat membranes and hollow fiber membranes (HFMs) via thermally induced phase separation (TIPS) to achieve facilitated blood-gas exchange. Cu-TAPB-COF nanosheets (CuCON) with framework structure and abundant active metal sites were synthetized and introduced into PMP to construct hybrid oxygenation membranes, reducing the resistance of gas exchange channels and ensuring the high affinity toward CO2 and O2. Cu+ and benzene rings existed in aromatic skeleton as well as the tunable structure, that could ensure the stability of MCOF and the uniform distribution of facilitated transport sites. The prepared PMP-CuCON-1 HFMs exhibited O2 and CO2 exchange rate of ∼467.5 ml min−1 m−2 and ∼309.1 ml min−1 m−2 in blood gas exchange process, which was 143.1% and 261.3% higher than the commercial PMP HFM, respectively. Asymmetric structure ensured resistance to plasma leakage for more than two weeks, and Cu+ kept stable in CuCON and hybrid membranes. The hybrid membrane exhibited superior blood-gas exchange performance and good hemocompatibility, possessing great potential for application.

Design Optimization of a Phototherapy Extracorporeal Membrane Oxygenator for Treating Carbon Monoxide Poisoning.

We designed a photo-ECMO device to speed up the rate of carbon monoxide (CO) removal by using visible light to dissociate CO from hemoglobin (Hb). Using computational fluid dynamics, fillets of different radii (5 cm and 10 cm) were applied to the square shape of a photo-ECMO device to reduce stagnant blood flow regions and increase the treated blood volume while being constrained by full light penetration. The blood flow at different flow rates and the thermal load imposed by forty external light sources at 623 nm were modeled using the Navier-Stokes and convection-diffusion equations. The particle residence times were also analyzed to determine the time the blood remained in the device. There was a reduction in the blood flow stagnation as the fillet radii increased. The maximum temperature change for all the geometries was below 4 °C. The optimized device with a fillet radius of 5 cm and a blood priming volume of up to 208 cm3 should decrease the time needed to treat CO poisoning without exceeding the critical threshold for protein denaturation. This technology has the potential to decrease the time for CO removal when treating patients with CO poisoning and pulmonary gas exchange inhibition.

Device updates in pediatric and neonatal ECMO

Since the early use of extracorporeal life support (ECLS), new innovations and technological advancements have augmented the ability to use this technology in children and neonates. Cannulae have been re-designed to maintain structure and allow for single cannula venovenous (VV) ECLS in smaller patients. Circuit technology, including pumps and tubing, has evolved to permit smaller priming volumes and lower flow rates with fewer thrombotic or hemolytic complications. New oxygenator developments also improve efficiency of gas exchange. This paper serves as an overview of recent device developments in ECLS delivery to pediatric and neonatal patients.

Reduced Invasiveness of Cardiopulmonary Bypass: The Mini-Circuit and the Micro-Cardioplegia.

The aim of cardiopulmonary bypass is the maintenance of a sufficient whole body perfusion and gas exchange during open or closed heart surgery procedure (coronary artery bypass grafting, valve repair and replacement, surgical intervention on the ascending aorta and/or aortic arch, repair of congenital malformations, and finally implantation of ventricular assist devices or cardiac transplantation). The main components of cardiopulmonary bypass are the pump that supplies the circulation and the oxygenator that regulates gas exchange. However, even though this technology has been extensively developed and improved over the last decades, one of the major drawbacks-which is the fact that blood has to flow through tubing systems with foreign surfaces-persists so far. Nevertheless, interesting innovations have been made more recently in order to better control the side-effects that culminate into a major activation of the coagulation and inflammatory systems: among them, miniaturization of the circuits, together with reduction of the priming volume and a simplified cardioplegia concept. All of these lead to a significant decrease of hemodilution and thereby a significant reduction of volume overload during surgery. In this brief review we will present some of these most interesting topics around minimized circuits and the simplified low-volume cardioplegia and discuss their potential benefits on the clinical outcome.

Plasma-Free Strategy for Cardiac Surgery with Cardiopulmonary Bypass in Infants < 10 kg: A Retrospective, Propensity-Matched Study.

Infants < 10 kg undergoing cardiac surgery with cardiopulmonary bypass (CPB) may receive either fresh frozen plasma (FFP) or other solutions in the CPB priming volume. The existing comparative studies are controversial. No study addressed the possibility of total avoidance of FFP throughout the whole perioperative course in this patient population. This retrospective, non-inferiority, propensity-matched study investigates an FFP-free strategy compared to an FFP-based strategy. Among patients <10 kg with available viscoelastic measurements, 18 patients who received a total FFP-free strategy were compared to 27 patients (1:1.5 propensity matching) receiving an FFP-based strategy. The primary endpoint was chest drain blood loss in the first 24 postoperative hours. The level of non-inferiority was settled at a difference of 5 mL/kg. The 24-h chest drain blood loss difference between groups was -7.7 mL (95% confidence interval -20.8 to 5.3) in favor of the FFP-based group, and the non-inferiority hypothesis was rejected. The main difference in coagulation profile was a lower level of fibrinogen concentration and FIBTEM maximum clot firmness in the FFP-free group immediately after protamine, at the admission in the ICU and for 48 postoperative hours. No differences in transfusion of red blood cells or platelet concentrate were observed; patients in the FFP-free group did not receive FFP but required a larger dose of fibrinogen concentrate and prothrombin complex concentrate. An FFP-free strategy in infants < 10 kg operated with CPB is technically feasible but results in an early post-CPB coagulopathy that was not completely compensated with our bleeding management protocol.

BIO31: Novel Size-Variable Dedicated Rodent Oxygenator for ECLS Animal Models – Introduction of the “Ratox” Oxygenator and Preliminary In-Vitro Results

Introduction: Extracorporeal life support (ECLS) grows in relevance. However, the survival rate of ECLS remains low, overall at around 60 %, mostly due to hemocompatibility issues. Research and development in the field is slow due to several factors, including the lack of sophisticated experimental platforms and models. This publication introduces a rodent–sized oxygenator module (“RatOx”) to enable early and large–scale in–vitro and in–vivo studies, followed by preliminary in–vitro classification tests on gas transfer performance. The oxygenator is designed to allow extensive in–vitro testing with donated human blood as well as economic and reproducible in–vivo testing for fundamental research. Materials and Methods: The novel RatOx’ main feature is the adaptable fiber module size suitable for various rodents like mice, rats, or hamsters. The effective membrane surface area is variable between approximately 10 cm2 and 600 cm2. The priming volume, and hence the hemodilution of the supported small animal, is kept at a minimum. Any type of semipermeable hollow fiber with any surface modification or coating can be mounted. The housing is transparent, hemocompatible, sterilizable and reusable. Oxygen transfer and carbon dioxide transfer over the oxygenator membrane were tested for different blood flows and fiber module sizes according to DIN EN ISO 7199. Similar experiments were conducted by an independent laboratory to test the transferability of the system to other institutions. Results: At the maximum possible amount of effective fiber surface and a blood flow of 100 ml/min, the oxygenator performance has been tested to a maximum of 5.5 ml O2/min and –5.5 ml CO2/min, respectively. For the same operating point, results from the independent laboratory showed transfer rates of 6.27 ml O2/min and –8.2 ml CO2/min, respectively. The priming volume for this the largest fiber module is 5.4 ml, while the smallest possible configuration with a single fiber mat layer has 1.1 ml of priming volume. Discussion, conclusion and outlook: The novel RatOx ECLS system has been evaluated in–vitro to comply to a high degree with all predefined functionality criteria for rodent–sized animal models. The maximum gas transfer efficacy for full-support-scenarios was measured to be approximately 70–80 % of the intended value pre–defined as the demand of a resting Sprague–Dawley rat. The priming volume translates into an oxygenator–caused hemodilution of approximately 25 %. We intend for the RatOx to become a standard testing platform for scientific studies on ECLS therapy and technology. This presentation includes evidence that this system is variable, yet very robust, allowing cross–lab and cross–model testing.

CARD25: Development of a Minimally Invasive Single Port Pulsatile Ventricular Assist Device

Purpose: Our goal is to develop a compact, single port, pulsatile ventricular assist device (VAD) for total left ventricle (LV) support that only requires a minimally invasive single cannulation from apex to aorta. Methods: Standard diaphragm displacement pumps have 2 valved ports and inlet/outlet cannulas to alternate between blood infusion and withdrawal. By contrast, our compact single port pulsatile VAD consists of a valved single lumen cannula and a valveless single port diaphragm displacement pump. Via a small left thoracotomy, the valved single lumen cannula is inserted from apex to aorta (Fig). Four one-way inlet valves on the valved single lumen cannula wall allow blood withdrawal from LV, and a tri-leaflet outlet valve at the cannula tip allows blood delivery to aorta. The 28 Fr valved single lumen cannula prototype was made as one piece by polyurethane (PU) dip molding with memory alloy reinforcement. The two halves of the valveless single port diaphragm displacement pump prototype housing were made by polycarbonate vacuum thermoforming and assembled with a flexible PU membrane diaphragm in the middle to separate the blood and pneumatic chambers. This pump had a 60 cc stroke volume. A closed mock loop with 37% glycerin was used to mimic the LV-aortic valve-ascending aorta tract. Priming volume and reservoir height were adjusted to maintain 70 mm Hg diastolic aortic pressure and 16 mm Hg preload. Circuit flow and pressure in valved single lumen cannula were recorded. The catheter introducer with pressure transducer on tip was inserted through apex in adult sheep (n=5, 44-52 kg), with pressure wave form guiding tip into ascending aorta. The valved single lumen cannula slid along introducer through apex, crossing aortic valve, with its tip in ascending aorta. The valved single lumen cannula was connected to the single port diaphragm displacement pump. Pumping was increased for a normal cardiac output. The single port pulsatile VAD prototype performance was assessed for 6 hrs with hemodynamics/blood counts recorded. Results: The valved single lumen cannula and single port diaphragm displacement pump prototypes were fabricated as designed. The bench study showed that the single port pulsatile VAD achieved a pumping flow of up to 3.75 L/min. Valve regurgitation was <3%. In the sheep study, the valved single lumen cannula was easily installed within 1 min at first attempt. The single port pulsatile VAD achieved maximal 3.75 L/min pumping flow in a 52 kg sheep. The single port pulsatile VAD had consistent pumping flow through 6 hrs with stable hemodynamics (Table). Hemoglobin and platelet/white blood cell counts were unchanged. No obvious injury or thrombosis in heart or single port pulsatile VAD were observed at necropsy. Conclusions: Our single port pulsatile VAD only requires a single apex cannulation with valved single lumen cannula to achieve reliable LVAD performance, showing great promise for a short to mid-term minimally invasive LVAD.Figure 1. Our single port pulsatile ventricular assist device with a valved single lumen cannula and a valveless single port diaphragm displacement pump. Table 1. - Hemodynamics and Blood Count Results Sheep 1-5 Baseline Pump Run1 hr Pump Run3 hr Pump Run6 hr sABP (mm Hg) 111±15.5 138±19.5 122±16.4 113±16.2 CVP (mm Hg) 11±0.4 11±0.8 11±0.5 11±0.8 CO (L/min) 2.5±0.38 3.8±0.98 3.6±0.66 3.5±0.66 Pump Flow (L/min) 0±0 2.8±0.65* 2.7±0.65* 2.7±0.52* HR (bpm) 154±61.1 104±44.7 105±39.3 127±16 WBC (103/uL) 4.1±0.14 N/A N/A 4.8±2.57 PLT (103/uL) 467±93.3 N/A N/A 380±171 HgB (g/dL) 9.4±0.45 N/A N/A 9.1±0.38 * p<0.05 vs Baseline sABP=systolic arterial pressure, CVP=central venous pressure, CO=cardiac output, HR=heart rate, WBC=white blood cell count, PLT=platelet count, HgB=hemoglobin, and N/A=not applicable.

PEDS8: Continuous Renal Replacement Therapy In Pediatric Extracorporeal Membrane Oxygenation: Life Span And Cost Of Filter Changes With Bivalirudin.

Background: The utilization of additional extracorporeal support devices utilized in conjunction with Extracorporeal Membrane Oxygenation (ECMO) has increased with more complex and sicker patients. The use of Continuous Renal Replacement Therapy (CRRT) has increased five-fold over the past 3 years at our institution after implementing Pediatric Nephrology Stewardship (PNS) on ECMO. Bivalirudin is the primary anticoagulant used for ECMO and CRRT at our institution which has resulted in increased ECMO circuit and CRRT filter life. The Prismalflex HF1000 and HF20 filter has a prime volume of 165 ml and 58 ml, respectively, with prime components which include packed red blood cells (pRBC) and albumin. Manufacturer recommendations for changing the CRRT filter is defined as every 72 hours (3 days). We sought to extend the filter length by augmenting the indication for the CRRT filter change from manufacturer recommendation. Filter changes were determined based on monitoring the filter pressure, transmembrane pressure, and pressure drop to diagnosis clotting/clogging. CRRT filter was also changed out if disconnection from ECMO was warranted due to ECMO circuit change or travel. Methods: Retrospective ECMO and CRRT data was collected for pediatric veno-arterial or veno-venous ECMO patients at a tertiary care hospital from January 2021-December 2022. Results: CRRT was performed on 16% (7/44) of ECMO patients. 100% of the patients received bivalirudin as the anticoagulant. 71% (5/7) were supported by VA ECMO. 43% (3/7) were neonates. Mean ECMO duration was 14 days (3-133). Of the 7 ECMO patients on CRRT, 80% (265/332) of their time on ECMO included CRRT support. There was a total of 41 CRRT filter changes performed during 265 days on CRRT with an average filter change occurring every 6.46 days (table 1). Utilizing cost of CRRT filter set ($358.00) and approximate cost of 1 unit of pRBC ($200.00), there was a savings of $26,226 to the hospital ($22,878 vs. $49,104). Discussion: Utilization of an alternative indication versus manufacturer recommendation for CRRT filter change out prolonged filter length from 3 days to 6.46 days (110% decrease in filter change out). By reducing the number of CRRT filters and blood usage for a filter change, cost to the hospital and patients was significantly reduced even without considering labor for CRRT set up and blood preparation. With careful attention to detail and collaboration with Nephrology and Hematology services, it appears CRRT filter length can be safely extended past manufacturers recommendations.