Bypass Circuit Research Articles

Low Microcirculatory Perfused Vessel Density and High Heterogeneity are Associated With Increased Intensity and Duration of Lactic Acidosis After Cardiac Surgery with Cardiopulmonary Bypass.

Lactic acidosis after cardiac surgery with cardiopulmonary bypass is common and associated with an increase in postoperative morbidity and mortality. A number of potential causes for an elevated lactate after cardiopulmonary bypass include cellular hypoxia, impaired tissue perfusion, ischemic-reperfusion injury, aerobic glycolysis, catecholamine infusions, and systemic inflammatory response after exposure to the artificial cardiopulmonary bypass circuit. Our goal was to examine the relationship between early abnormalities in microcirculatory convective blood flow and diffusive capacity and lactate kinetics during early resuscitation in the intensive care unit. We hypothesized that patients with impaired microcirculation after cardiac surgery would have a more severe postoperative hyperlactatemia, represented by the lactate time-integral of an arterial blood lactate concentration greater than 2.0 mmol/L. We measured sublingual microcirculation using incident darkfield video microscopy in 50 subjects on intensive care unit admission after cardiac surgery. Serial measurements of systemic hemodynamics, blood gas, lactate, and catecholamine infusions were recorded each hour for the first 6 h after surgery. Lactate area under the curve (AUC) was calculated over the first 6 h. The lactate AUC was compared between subjects with normal and low perfused vessel density (PVD < 18 mm/mm2), high microcirculatory heterogeneity index (MHI > 0.4), and low vessel-by-vessel microvascular flow index (MFIv < 2.6). Thirteen (26%) patients had a low postoperative PVD, 20 patients (40%) had a high MHI, and 26 (52%) patients had a low MFIv. Patients with low perfused vessel density had higher lactate AUC compared with subjects with a normal PVD (22.3 [9.4-31.0] vs. 2.6 [0-8.8]; P < 0.0001). Patients with high microcirculatory heterogeneity had a higher lactate AUC compared with those with a normal MHI (2.5 [0.1-8.2] vs. 13.1 [3.7-31.1]; P < 0.001). We did not find a difference in lactate AUC when comparing high and low MFIv. Low perfused vessel density and high microcirculatory heterogeneity are associated with an increased intensity and duration of lactic acidosis after cardiac surgery with cardiopulmonary bypass.

Individualized, Intraoperative Dosing of Fibrinogen Concentrate for the Prevention of Bleeding in Neonatal and Infant Cardiac Surgery Using Cardiopulmonary Bypass (FIBCON)

Background:Mediastinal bleeding is common following pediatric cardiopulmonary bypass surgery for congenital heart disease. Fibrinogen concentrate (FC) represents a potential therapy for preventing bleeding.Methods:We performed a single-center, phase 1b/2a, randomized controlled trial on infants 2.5 to 12 kg undergoing cardiopulmonary bypass surgery, aimed at (1) demonstrating the feasibility of an intraoperative point-of-care test, rotational thromboelastometry, to screen out patients at low risk of postoperative bleeding and then guide individualized FC dosing in high-risk patients and (2) determining the dose, safety, and efficacy of intraoperative FC supplementation. Screening occurred intraoperatively 1-hour before bypass separation using the rotational thromboelastometry variable fibrinogen thromboelastometry maximum clot firmness (FibTEM-MCF; fibrinogen contribution to clot firmness). If FibTEM-MCF ≥7 mm, patients entered the monitoring cohort. If FibTEM-MCF ≤6 mm, patients were randomized to receive FC/placebo (2:1 ratio). Individualized FC dose calculation included weight, bypass circuit volume, hematocrit, and intraoperative measured and desired FibTEM-MCF. The coprimary outcomes, measured 5 minutes post-FC administration were FibTEM-MCF (desired range, 8–13 mm) and fibrinogen levels (desired range, 1.5–2.5 g/L). Secondary outcomes were thrombosis and thrombosis-related major complications and postoperative 24-hour mediastinal blood loss.Results:We enrolled 111 patients (cohort, n=21; FC, n=60; placebo, n=30); mean (SD) age, 6.4 months (5.8); weight, 5.9 kg (2.0). Intraoperative rotational thromboelastometry screening effectively excluded low-risk patients, in that none in the cohort arm (FibTEM-MCF, ≥7 mm) demonstrated clinically significant early postoperative bleeding (&gt;10 mL/kg per 4 hours). Among randomized patients, the median (range) FC administered dose was 114 mg/kg (51–218). Fibrinogen levels increased from a mean (SD) of 0.91 (0.22) to 1.7 g/L (0.41). The postdose fibrinogen range was 1.2 to 3.3 g/L (72% within the desired range). The corresponding FibTEM-MCF values were as follows: pre-dose, 5.3 mm (1.9); post-dose, 13 mm (3.2). Ten patients (8 FC and 2 placebo) exhibited 12 possible thromboses; none were clearly related to FC. There was an overall difference in mean (SD) 24-hour mediastinal drain loss: cohort, 12.6 mL/kg (6.4); FC, 11.6 mL/kg (5.2); placebo, 17.1 mL/kg (14.3; ANOVAP=0.02).Conclusions:Intraoperative, individualized dosing of FC appears feasible. The need for individualized dosing is supported by the finding that a 4-fold variation in FC dose is required to achieve therapeutic fibrinogen levels.Registration:URL:https://eudract.ema.europa.eu/; Unique identifier: 2013-003532-68. URL:https://www.isrctn.com/; Unique identifier: 50553029.

Abstract 13699: Cyclohexanone Contamination of Medical Plastics is Associated With Worse Congenital Heart Surgery Outcomes

Introduction: Cyclohexanone, an industrial medical plastic fabrication contaminant, can leach from medical plastics including the cardiopulmonary bypass (CPB) circuit. Effects of neonatal perioperative cyclohexanone exposure on hospital-based outcomes have not been explored. Hypothesis: We hypothesize that serum cyclohexanone during congenital heart surgery with CPB is associated with worse morbidity. Methods: The study was a secondary analysis of 107 neonates enrolled in the NHLBI-funded Corticosteroid Therapy in Neonates Undergoing Cardiopulmonary Bypass trial. Blood samples were collected preoperatively, post-CPB, and 12 hours postoperatively, and concentrations of cyclohexanone and its metabolites were quantified using mass spectrometry. Using the geometric mean of cyclohexanone concentrations, the effects of an interquartile range (IQR) increase in concentration on hospital-based outcomes was assessed using adjusted linear and Poisson regression, for continuous and dichotomous outcomes, respectively. Estimates were reported as % differences (linear regression) or relative risks (Poisson regression) with 95% confidence intervals. Results: In adjusted analyses, an IQR increase in mean cyclohexanone concentration was associated with greater time spent on mechanical ventilation (40.1%: 7.34%, 82.9%), in the ICU (20.1%: 1.36%, 42.2%), and in the hospital (20.8%: 3.28%, 41.3%), and less time spent alive and out of the hospital 90 days post-surgery (-17%: -30.9%, -0.36%). An IQR increase in mean cyclohexanone was associated with a 61% (RR: 1.61; 1.19, 2.17) greater risk of the trial primary morbidity-mortality composite outcome (death, cardiac arrest, ECMO, renal or hepatic insufficiencies, and lactic acidosis). An IQR increase in mean cyclohexanone metabolites was associated with a 29% (RR: 1.29; 1.07, 1.55) greater risk of developing low cardiac output syndrome. Conclusions: This study showed that in neonates, circulating cyclohexanone was associated with unfavorable hospital-based outcomes following cardiac surgery with CPB, suggesting that medical plastic contamination may contribute to morbidity. Therefore, reducing exposure to cyclohexanone perioperatively may improve congenital heart surgery outcomes.

Abstract 14857: Outcomes of Bloodless Congenital Cardiac Surgery on Cardiopulmonary Bypass

Introduction: Bloodless cardiac surgery defined as blood transfusion-free open-heart surgery, where cardiopulmonary bypass (CPB) circuits primed with crystalloid only and no intraoperative blood transfusion. Limited data have been published in this field. Hypothesis: We asked whether blood conservative surgery is feasible in congenital heart disease. Methods: We retrospectively reviewed patients who underwent bloodless cardiac surgery for congenital heart disease on CPB between January 2016 and December 2018. Our unique CPB system utilizes assisted venous drainage, bioactive coating, and reduced tubing size to decrease priming volume, and complement activation. Results: A total of 164 patients were reviewed (86 male and 78 female) at a median age of 9.6 years (range, 13 months-55 years), weight of 32 kg (IQR, 16-55), preoperative hemoglobin 13.7 g/dl (IQR, 12.6-14.9), and preoperative hematocrit of 40.3% (IQR, 37.2-44.3). Median CPB time was 81.5 minutes (IQR, 58-125), and median hematocrit coming off CPB was 26% (IQR, 23-29.7). Congenital Heart Surgery risk (STAT) category distributed in STAT 1 for 70 (43%), STAT 2 for 80 (49%), STAT 3 for 9 (5%), and STAT 4 for 5 (3%) of the patients. The majority (95%) of patients were extubated in the operating room with low complications rate during the hospital stay (7%). Only 6 (4%) patients needed a blood transfusion in the postoperative period with higher incidence of complications during the hospital course (LR 14.9; p&lt;0.001). The median length of hospital stay was 3.6 days (IQR 2.6-5.6). There was no in-hospital mortality or 30 days mortality after surgery. Conclusions: Bloodless congenital cardiac surgery has a high success rate in selected low to medium surgical risk and even higher risk patients (STAT 3 and 4). Our patients had a low rate of complications and short hospital course. The blood product transfusion correlated significantly with a higher rate of complications during the postoperative course.

Extension of cardiopulmonary bypass outside the operating room as a short-term bridge to recovery "the poor man's ECMO".

This report describes the use of conventional cardiopulmonary bypass (CPB) circuit beyond the operating room to the critical care unit to provide cardiopulmonary support for patients requiring emergent resuscitation as well as short-term support for rest and recovery of the heart. We modified the CPB circuit and created a closed extra corporeal membrane oxygenation (ECMO) circuit using a conventional oxygenator excluding the venous reservoir. We believe that this technique provides a short-term mechanical support and also acts as a bridge to recovery, or a bridge to decision, in very limited resource settings.

Impact of miniaturized cardiopulmonary bypass circuits on ultrafiltration during congenital heart surgery.

To investigate whether the miniaturized cardiopulmonary bypass (CPB) system decreased the usage of ultrafiltration (UF), and to explore whether the non-UF with miniaturized CPB strategy could get good clinical results during congenital heart surgery. We performed a retrospective analysis of all patients undergoing congenital heart surgery with CPB at Shenzhen Children's Hospital from 1 May 2015 to 30 September 2019. We classified patients to UF with miniaturized CPB group, non-UF with miniaturized CPB group, UF with conventional CPB group and non-UF with conventional CPB group. Of the 2145 patients, 721 (33.6%) were in the conventional CPB group, and 1424 (66.4%) were in the miniaturized CPB group. The UF rate was significantly lower in the miniaturized CPB group compared with that in the conventional CPB group (12.5% vs. 76.8%, p < 0.001). Compared with patients in the other groups, patients in the non-UF with miniaturized CPB group had a shorter postoperative MV time (p < 0.05), and a shorter length of stay in the ICU (p < 0.001) and hospital (p < 0.001). The age of children in the UF with miniaturized CPB group was relatively younger (median: 1.5 months, IQR: 0.3-4.6 months), and the preoperative weight was relatively lower (median: 3.9 kg, IQR: 3.2-5.4 kg). Moreover, this group of children had a relatively longer postoperative MV time and length of stay in the ICU and hospital. The miniaturized CPB system could decrease the usage of UF. Good results were achieved in children who did not use UF based on the miniaturized CPB circuit system during congenital heart surgery.

Strategies for bloodless priming of cardiopulmonary bypass circuits in pediatric cardiac surgery

Bloodless cardiopulmonary bypass in paediatric cardiac surgery in patients weighing more than 15 kg can be performed safely and effectively. Incorporating a low-prime volume oxygenator into a revised circuit reduced the need for blood transfusion and allowed us to achieve our desire flow rate of 2.6±0.21 L/min/m2 while maintaining a haematocrit ranging from 28% to 36%.

Adult cardiopulmonary bypass in Australian and New Zealand public hospitals: A survey of practice.

A telephone survey of cardiac anaesthetists and perfusionists at the 29 public hospitals providing adult cardiac surgical services in Australia and New Zealand was carried out between December 2019 and January 2020. The aim was to investigate current practice with regard to selected contentious elements of anaesthetic and perfusion management during cardiopulmonary bypass; primarily relating to bypass circuit priming, blood conservation methods and point-of-care coagulation testing. There was a 100% response rate. The average number of adult public cardiopulmonary bypass cases per hospital was 508 (160-1400). For cardiopulmonary bypass cases, ten hospitals (34%) routinely used a cell saver and the remainder used a cell saver selectively. Residual blood remaining in the cardiopulmonary bypass circuit was processed using a cell saver routinely in four hospitals (14%) and selectively in 23 (79%). Acute normovolaemic haemodilution was rarely used. Retrograde autologous priming was used routinely in seven hospitals (24%) and selectively in 16 (55%). All hospitals had access to point-of-care coagulation testing. The majority of hospitals targeted an activated clotting time of 480 s (range 400-500 s) prior to commencing cardiopulmonary bypass. There was marked geographic variation in access to fibrinogen concentrate. The cardiopulmonary bypass circuit prime solution was primarily a balanced crystalloid in most hospitals; however, there was significant variation regarding the addition of human albumin, mannitol, sodium bicarbonate and other medications. Many of the interventions examined were used on a case-by-case basis. These findings support the need for further research to define more evidence-based practice of these interventions.

Correlation between activated clotting time and anti-xa activity in patients undergoing cardiac surgery requiring cardiopulmonary bypass

Introduction Anticoagulation for cardiopulmonary bypass (CPB) has historically involved the use of heparin as the anticoagulant of choice. Activated clotting time (ACT) is considered the gold standard for determining adequate level of anticoagulation before and during CPB. Recent guidelines suggest ACT > 480 seconds during CPB; however, initial validation studies were done on much older generations of bypass circuits in animal models and results have not been replicated in more recent clinical studies. ACT is also a measure of whole blood clotting and does not necessarily reflect degree of heparin activity. Newer studies have shown poor correlation between ACT and anti-Xa activity levels, the latter considered the gold standard for monitoring heparin activity. We sought to quantify the correlation between two point-of-care ACT instruments with the laboratory based anti-Xa activity assay for patients undergoing cardiac surgery requiring CPB at various time points during surgery. Methods 50 patients undergoing cardiac surgery requiring CPB were consented and enrolled. Blood samples were taken from each patient to examine the correlation between two ACT point-of-care instruments, Hemochron and i-STAT, and that of anti-Xa activity at various points during surgery. These timepoints were at baseline, after initial heparin bolus prior to initiating bypass, during CPB, and after protamine reversal of heparin. Pearson's correlation coefficient (r) was calculated for each set of comparisons. Results We obtained a total of 542 comparisons between ACT values and anti-Xa activity. There was poor correlation between both ACT instruments and anti-Xa activity after the initial bolus of heparin prior to bypass (r = 0.27 and 0.15), with correlations worsening on bypass (r = 0.11 and 0.04). i-STAT generally correlated better with anti-Xa activity and the two ACT instruments generally correlated well with each other (r = 0.88, all timepoints), except while on CPB (r = 0.11, CPB only). There was greater than 16-fold difference seen in heparin activity between patient samples when ACT > 400, with anti-Xa activity ranging from 0.78 to 16.10 U/mL. The average ACT (i-STAT) after protamine reversal was 22 seconds lower than baseline; however, average post-protamine anti-Xa activity was 0.77 U/mL. Discussion Our results suggest perhaps excessive and/or suboptimal anticoagulation in some patients during CPB and inadequate reversal of heparin post-bypass despite ACT values normalizing. Using ACT alone as a point-of-care tool may be inadequate in determining the optimal level of anticoagulation during bypass and reversal of heparin in patients undergoing cardiac surgery requiring CPB.

Neonatal intra-atrial baffle repair for isolated ventricular inversion with left isomerism: a case report

BackgroundDiscordant atrioventricular connection with concordant ventriculoarterial connection, otherwise known as isolated ventricular inversion (IVI), is an extremely rare congenital cardiac malformation. Reports on the corrective surgery for this anomaly in neonates are few, and the procedure is difficult and complicated. Herein, we report our use of atrial septostomy as a palliative procedure followed by corrective surgery for the repair of neonatal IVI with situs ambiguous(inversus) morphology.Case presentationA 2-day-old girl weighing 3.5 kg was admitted to our hospital with a low oxygen saturation (SpO2) of 70% She was diagnosed with IVI [situs ambiguous(inversus), D-loop, and D-Spiral], atrial septal defect, patent ductus arteriosus (PDA), interrupted inferior vena cava with azygos continuation to the left superior vena cava (SVC), and polysplenia by transthoracic echocardiography and cardiac computed tomography. We planned to perform corrective surgery and decided to first increase interatrial mixing by performing surgical atrial septostomy and PDA ligation 7 days after birth. However, despite the surgical septostomy, pulmonary venous blood flowed toward the right ventricle via the tricuspid valve rather than toward the left-sided atrium and hypoxemia persisted. We decided to perform the intra-atrial switch procedure at the age of 17 days via a re-median sternotomy. The cardiopulmonary bypass (CPB) circuit was established with ascending aorta and venous drainage through the SVC and hepatic veins. Utilizing a left-sided atrium(l-A) approach, a bovine pericardial patch was used for the intra-atrial baffle, which was trimmed into a trouser-shaped patch. Continuous suture using the patch was lying from the front of the right-sided upper pulmonary vein and rerouted SVC, hepatic vein, and coronary sinus to the tricuspid valve. Overall, CPB weaning proceeded smoothly; however, direct current cardioversion was performed for junctional ectopic tachycardia. The postoperative course was uneventful. Her postoperative SpO2 improved (approximately 99–100%); overall, the patient showed clinical improvement. Discharge echocardiography showed normal biventricular function and an intact atrial baffle with no venoatrial or atrioventricular obstruction.ConclusionWe successfully performed an intra-atrial switch procedure for isolated ventricular inversion in a neonate. Long-term follow-up will be necessary to ensure the maintenance of optimal cardiac function.

Specific parameters of operation of the minimized system for cardioplegia in children. Bench test

It is very important to observe all the parameters of cardioplegia when protecting myocardium during cardiac surgery. To perform this task, it is necessary to have clear understanding of properties of the elements of the extracorporeal circuit of cardiopulmonary bypass. The objective : to develop a test model and using it to evaluate technical capabilities of blood cardioplegic system reducing the filling volume of the heat exchange chamber and the system supplying solution to the myocardium. Subjects and methods . A model of a neonatal cardiopulmonary bypass circuit was tested, it included an oxygenator and the cardioplegic system with a 7-ml heat exchange chamber; changes in the pressure and temperature in key nodes of the extracorporeal and cardioplegic circuits were assessed when the pump velocity, ambient temperature and fluid temperature in the main circuit were changed. Results . This modification provides a wide range of liquid volumetric velocities. Maintaining the selected variant of blood cardioplegia and safe pressure within the cardioplegic circuit is ensured at the perfusion rate of up to 350 ml/min. With normothermal circulation and air temperature in the operating room of 23°C, parameters of the cardioplegic circuit and solution delivery system allows maintaining the solution temperature within the range from 16 to 19°C. When the solution is cooled in a heat exchanger down to 4°C, the temperature of the final cardioplegic solution is maintained within 12-17°C; and with normothermal perfusion, air temperature in the operating room of 15°C and the solution temperature in the heat exchange chamber of 4°C, the temperature of the final cardioplegic solution can be within 6‒13°C. With perfusion in the mode of moderate hypothermia (32°C), air temperature in the operating room 15°C and temperature in the heat exchange chamber 4°C, the final cardioplegic solution can be delivered at the temperature from 5 to 9°C. Conclusions . The proposed test model allows investigating aimed to find out additional characteristics of the cardioplegic circuit. Ambient air temperature, cardioplegic pump velocity and main circuit fluid temperature are the main factors influencing the final cardioplegic solution temperature. When using the studied variant of the cardioplegic circuit assembly, the maintenance of the selected variant of blood cardioplegia and safe pressure inside the cardioplegic circuit are ensured at a perfusion rate of up to 350 ml/min.

High-Dose Dabigatran Is an Effective Anticoagulant for Simulated Cardiopulmonary Bypass Using Human Blood.

Currently no ideal alternative exists for heparin for cardiopulmonary bypass (CPB). Dabigatran is a direct thrombin inhibitor for which a reversal agent exists. The primary end point of the study was to explore whether Dabigatran was an effective anticoagulant for 120 minutes of simulated CPB. The study was designed in 2 sequential steps. Throughout, human blood from healthy donors was used for each experimental step. Initially, increasing concentrations of Dabigatran were added to aliquots of fresh whole blood, and the anticoagulant effect measured using kaolin/tissue factor-activated thromboelastography (rapidTEG). The dynamics of all thromboelastography (TEG) measurements were studied with repeated measures analysis of variance (ANOVA). Based on these data, aliquots of blood were treated with high-concentration Dabigatran and placed in a Chandler loop as a simple ex vivo bypass model to assess whether Dabigatran had sufficient anticoagulant effects to maintain blood fluidity for 2 hours of continuous contact with the artificial surface of the PVC tubing. Idarucizumab, humanized monoclonal antibody fragment, was used to verify the reversibility of Dabigatran effects. Finally, 3 doses of Dabigatran were tested in a simulated CPB setup using a heart-lung machine and a commercially available bypass circuit with an arteriovenous (A-V) loop. The primary outcome was the successful completion of 120 minutes of simulated CPB with dabigatran anticoagulation, defined as lack of visible thrombus. Thromboelastographic reaction (R) time was measured repeatedly in each bypass simulation, and the circuits were continuously observed for clot. Scanning Electron Microscopy (SEM) was used to visualize fibrin formation in the filters meshes during CPB. In in vitro blood samples, Dabigatran prolonged R time and reduced the dynamics of clot propagation (as measured by speed of clot formation [Angle], maximum rate of thrombus generation [MRTG], and time to maximum rate of thrombus generation [TMRTG]) in a dose-dependent manner. In the Chandler Loop, high doses of Dabigatran prevented clot formation for 120 minutes, but only at doses higher than expected. Idarucizumab decreased R time and reversed anticoagulation in both in vitro and Chandler Loops settings. In the A-V loop bypass simulation, Dabigatran prevented gross thrombus generation for 120 minutes of simulated CPB. Using sequential experimental approaches, we showed that direct thrombin inhibitor Dabigatran in high doses maintained anticoagulation of blood for simulated CPB. Idarucizumab reduced time for clot formation reversing the anticoagulation action of Dabigatran.

A novel technique for laser-assisted revascularization: an in vitro pilot study.

The common limitation of surgical revascularization procedures for severe tissue ischemia due to cardiovascular diseases is the need to interrupt blood flow during the intervention. We aim to introduce a new technique that allows a sutureless, non-occlusive revascularization. A 3-step technique was developed using rabbit's aorta to simulate a side-to-side anastomosis model. It enables the creation of a bypass circuit for revascularization. The first step was the soldering of 2 vessels in a side-to-side fashion based on the laser-assisted vascular anastomosis (LAVA) principle using a diode laser emitting irradiation at 810 nm with an albumin-based solder patch between them, followed by the creation of a channel within the patch using either a holmium-doped yttrium aluminum garnet laser (Ho:YAG) at λ = 2100 nm or a xenon-chloride excimer laser (XeCl) at λ = 308 nm. Thereby, a bypass circuit was created, thus allowing a non-ischemic revascularization. The system was deemed functional when a flow was observed across the anastomosis. The highest average tensile strength recorded after side-to-side LAVA using a diode laser power of 3.2 W for 60 s was 2278.6 ± 800 mN (n = 20). The Ho:YAG laser created the channels with less tension on the anastomosis than the excimer laser. Histological analysis showed limited thermal damage and good patch-tissue adaptation. The preliminary results of this feasibility study outline the foundations for an entirely sutureless laser-assisted revascularization procedure. The next studies will evaluate the rheological parameters across the bypass circuit to optimize the post-anastomotic flow.

Technical implementation of percutaneous thrombus aspiration using the AngioVac system.

The AngioVac system (AngioDynamics, Latham, NY, USA) provides a method for the minimally invasive, percutaneous aspiration of thrombus formations originating from the central venous system as well as solid matter such as lead vegetations and right atrial thrombi. This retrospective, observational study describes the initial experience in 52 adult patients with the AngioVac system, focusing mainly on the development of the extracorporeal circuit to improve usability and safety. The mean patient age was 62.9 years (range 23-86 years). 22 patients were female and 30 were male. Indications for percutaneous aspiration were lead vegetations (n = 36; 69.2%), right atrial thrombi (n = 9; 17.3%), central venous thrombi (n = 5; 9.6%) and pulmonary embolisms (n = 2; 3.8%). Successful aspiration was performed in 44 cases (84.6%) and partial success was achieved in five patients (9.6%), while failure to remove thrombi or vegetations occurred in three cases (5.8%). Our practical experience led to the installation of a shunt line for recirculation and the implementation of safety features concerning air handling, which are also employed in minimally invasive extracorporeal bypass circuits. Initial tests monitored the level of negative pressure according to differences in flow and access sites but these still have to be validated on a larger scale. In this initial experience, the AngioVac system appeared to be safe regarding the extracorporeal circulation and the elimination of thrombi and lead vegetations.

Fluid dynamics characterization and thrombogenicity assessment of a levitating centrifugal pump with different impeller designs

Technical guidelines nowadays recommend and regulate the use Computational Fluid Dynamics (CFD) to assess the performance of medical devices. CFD coupled to blood damage models has emerged as a powerful tool to evaluate the hemocompatibility of blood recirculating devices. The present study is aimed at evaluating the hydrodynamic performance and the thrombogenic potential of two prototypes of magnetically levitating centrifugal pumps. The two devices differ in the impeller configuration - 6-blades vs. 12-blades – and have been designed to be used in Cardiopulmonary Bypass (CPB) circuits during open heart surgery and in Extracorporeal Membrane Oxygenation (ECMO) to support patients with severe cardiac or respiratory failure. The pumps have been modelled using Direct Numerical Simulation coupled to Lagrangian analysis to predict platelet activation due to abnormal shear stress histories. Numerical results have been compared with experimental data in terms of head generation for different working points. Results show that the 6-blades pump has i) smaller stagnation areas, ii) lower stress levels and iii) higher strain rate, resulting in a lower thrombogenic potential, whereas the 12-blade impeller guarantees a more stable performance at high flow rates, suggesting its preferential use for more demanding applications, such as CPB.

Sterility and performance of open and closed extracorporeal circuits after long-term dry-wet setups.

The timeframe for safely using previously setup dry, crystalloid, and blood-primed extracorporeal circuits has long been debated. This study was undertaken to determine a safe deviation from standardized recommendations. Open (cardiopulmonary bypass) circuits and closed extracorporeal membrane oxygenation circuits were setup dry for up to 60 days and wet primed for up to 6 weeks with one control inoculated with Escherichia coli. Open circuits were cultured daily, closed circuits weekly. Circuits were primed with blood, albumin, heparin, NaHCO3, and CaCl2. Baseline pCO2, pO2, hemoglobin, lactate dehydrogenase, and plasma free hemoglobin were measured. Circuits were recirculated at a blood flow of 6 Liters/minute with a sweep gas of 1 Liter/minute at 100% FiO2 for 1 minute. Post oxygenator blood gases were collected at 8-, 16-, and 24-hour intervals. There was no observed compromise to the sterility of the circuits and no clinically significant gas exchange abnormalities observed over the duration of the study period. Statistical significance (p < 0.01) was seen in free hemoglobin and lactate dehydrogenase levels, most significant in between the 16- and 24-hour time point in the closed systems intentionally inoculated with E. coli. Open and closed circuits can be safely setup dry for up to 60 days. Open, wet-primed circuits can be used safely up to 5 days. Closed, wet-primed circuits can be used safely up to 6 weeks. Blood-primed circuits can be safely run up to 16 hours prior to patient use but should be validated in a randomized clinical study.

Modified cardiopulmonary bypass circuit for the use of the AngioVac® system in a case with high paradoxical embolization risk.

The AngioVac® is a vacuum-assisted percutaneous thrombectomy suction system. In critically ill patients, the sudden volume shift can result in abrupt hemodynamic changes thus leading to a cardiac right-left shunt with a high risk of paradoxical embolization. We describe a modified cardiopulmonary bypass circuit for the use of the AngioVac® system that enables full cardiopulmonary support and reduces paradoxical thromboembolic risk.

Nitric oxide delivery during cardiopulmonary bypass reduces acute kidney injury: A randomized trial

ObjectiveAcute kidney injury (AKI) is a serious complication of cardiac surgery with cardiopulmonary bypass (CPB). The aim of this study was to evaluate the effects of nitric oxide (NO) supplementation to the CPB circuit on the development of cardiac surgery–associated AKI. MethodsThis prospective randomized controlled study included 96 patients with moderate risk of renal complications who underwent elective cardiac surgery with CPB. The study protocol was registered at ClinicalTrials.gov (identifier NCT03527381). Patients were randomly allocated to either NO supplementation to the CPB bypass circuit (NO treatment group; n = 48) or usual care (control group; n = 48). In the NO treatment group, 40-ppm NO was administered during the entire CPB period. The primary outcome was the incidence of AKI. ResultsNO treatment was associated with a significant decrease in AKI incidence (10 cases [20.8%] vs 20 cases [41.6%] in the control group; relative risk, 0.5; 95% confidence interval, 0.26-0.95; P = .023) and a higher median urine output during CPB (2.6 mL/kg/h [interquartile range (IQR), 2.1-5.08 mL/kg/h] vs 1.7 mL/kg/h [IQR, 0.80-2.50 mL/kg/h]; P = .0002). The median urinary neutrophil gelatinase-associated lipocalin level at 4 hours after surgery was significantly lower in the NO treatment group (1.12 ng/mL [IQR, 0.75-5.8 ng/mL] vs 4.62 ng/mL [IQR, 2.02-34.55 ng/mL]; P = .005). In the NO treatment group, concentrations of NO metabolites were significantly increased at 5 minutes postclamping, at 5 minutes after declamping, and at the end of the operation. Concentrations of proinflammatory and anti-inflammatory mediators and free plasma hemoglobin did not differ significantly between the 2 groups. ConclusionsNO administration in patients at moderate risk of renal complications undergoing elective cardiac surgery with CPB was associated with a lower incidence of AKI.

On‐site detection of bypass circuit opening failure in photovoltaic array under power generation operation

AbstractTo ensure the long‐term reliability of photovoltaic systems (PVSs), periodical inspections are necessary. Despite the risk of severe temperature rise, bypass circuit open‐circuit (BPC‐OC) failure has attracted low research interest compared with other types of failure. This paper presents the pulsed light irradiation (PLI) method for robust BPC‐OC failure detection that eliminates the need to switch off the power generation operation of the PVS. The proposed method detects the BPC‐OC failure of the solar cell string by measuring the modulated current induced by local PLI. Electrical circuit simulations as well as indoor and outdoor experiments are performed to verify the performance of the proposed method. Results of the outdoor experiment show that the PLI method performs well in a real PVS under power generation operation. Finally, the advantages and disadvantages of the proposed method are summarized.

Comparison of three autotransfusion devices for utilization in the pediatric population.

A device that may help attenuate the amount of homologous blood product given to pediatric cardiac surgical patients is the autotransfusion device. Three separate autotransfusion devices were selected for evaluation. The Sorin Xtra, Fresenius Continuous Autotransfusion System Plus (CATS*plus), and the Fresenius Continuous Autotransfusion System Smart (CATSmart) were evaluated based on the mechanical processes of each device, hematocrit value of the salvaged packed red cell product, time of processing, and the advantageous accessories with each device. Each of the autotransfusion devices were used to collect salvageable blood from the surgical field as well as to process residual blood from the cardiopulmonary bypass circuit after decannulation. The cell salvage process was performed in accordance with the manufacturer's instructions for use and the recommended settings for processing and washing. The Sorin Xtra device had the 55 mL bowl set up for all cases, while the Fresenius continuous autotransfusion systems utilized the standard disposable for each device. Each cell salvage device was employed during 30 pediatric cardiac surgery procedures, and data for each device, was broken down into four groups based on patient weight (0-10, 10-20, 20-40, and >40 kg). For all patient sizes, the Sorin Xtra tended to produce the greatest volume of cell saver product (55-825 mL) as compared to the CATS*plus and CATSmart devices (7-550 mL and 0-860 mL, respectively). The Continuous Autotransfusion System Smart tended to produce the highest hematocrit product, ranging from 44 to 81%. Through this evaluation, it was determined the continuous autotransfusion systems provided the highest hematocrit with the lowest recovered packed red cell volume, while the Sorin Xtra packed red cell product showed to have a lower hematocrit with a larger packed red cell volume. Each device proved effective within our pediatric population.