Membrane Oxygenation Research Articles

A rabbit model of antegrade selective cerebral perfusion with cardioplegic arrest.

Due to the weak ascending aorta, it is extremely challenging to establish an anterograde selective cerebral perfusion (ASCP) model in rabbits, especially when cardioplegic arrest is required. Herein, the aim of this study was to establish a rabbit ASCP model with cardiac arrest being easily performed and being similar to the clinical scenario. Twenty-two adult New Zealand white rabbits were selected for ASCP model establishment and another 22 rabbits were utilized for blood donation. The cardiopulmonary bypass (CPB) circuit consisted of a roller pump, a membrane oxygenator, a heat-cooler system and a blood reservoir, which were connected by silicone tubing. The total priming volume of the circuit was 70 ml. Cannulations on the right and left subclavian arteries were used for arterial inflow and cardioplegia perfusion, respectively. Venous drainage was conducted through the right atrial appendage. ASCP was initiated by clamping the innominate artery; the flow rate was maintained 10 ml/kg/minute and sustained for 60 minutes. After 120 minutes of reperfusion, the rabbits were sacrificed. The mean arterial pressure, heart rate, electrocardiogram and urine output were monitored. Arterial blood samples were analyzed at the following time points: after anesthesia, immediately after CPB, after aorta cross-clamping and cardioplegia perfusion, 5 min after the re-opening of the aorta and at CPB termination. ASCP modeling was performed successfully on 18 rabbits and 4 rabbits unsuccessfully. Vital signs and blood gas indictors changed in an acceptable range throughout the experiments. One rabbit had ventricular fibrillation after re-opening of the ascending aorta. Obvious hemodilution occurred after the perfusion of cardioplegia, but the hematocrit improved after CPB termination. By using cannulation of the subclavian artery rather than the aorta and with a low priming volume, we established a modified rabbit model of ASCP with cardioplegic arrest. The model has excellent repeatability and operability, which is similar to the clinic process and is suitable for the study of cerebral, cardiac and renal protection.

Right ventricular assist device with membrane oxygenator support for right ventricular failure following implantable left ventricular assist device placement.

Cardiogenic shock from refractory right ventricular (RV) failure during left ventricular assist device placement is associated with high morbidity and mortality. The addition of extracorporeal membrane oxygenation to RV mechanical assistance may help RV recovery and lead to improved outcomes. We retrospectively reviewed all implanted continuous-flow left ventricular assist devices from April 2009 to June 2013. RV mechanical support was utilized for RV failure defined as haemodynamic instability despite vasopressors, pulmonary vascular dilators and inotropic therapy. RV assist devices were utilized with and without in-line membrane oxygenation. During the study period, 267 continuous-flow left ventricular assist devices were implanted. RV mechanical support was utilized in 27 (10%) patients; 12 (46%) had the addition of in-line extracorporeal membrane oxygenation. The mean age of patients with a right ventricular assist device with membrane oxygenation was lower than that in patients with a right ventricular assist device alone (45.6 ± 15.9 vs 64.6 ± 6.5, P = 0.001). Support was weaned in 66% (10 of 15) of patients with right ventricular assist device (RVAD) alone vs 83% (10 of 12) of those with RVAD with membrane oxygenation (P = 0.42). The RVAD was removed after 10.4 ± 9.4 vs 5 ± 2.99 days for patients with a RVAD with membrane oxygenation (P = 0.1). Patients with RVAD with membrane oxygenation had a 30-day mortality rate of 8 vs 47% for those with RVAD alone (P = 0.04). The survival rate after discharge was 86, 63 and 54% at 3, 6 and 12 months for both groups combined. Patients with a RVAD with membrane oxygenation support for acute RV failure after continuous-flow left ventricular assist device implantation had a lower 30-day mortality than those with a RVAD alone. Patients who survive to discharge have a reasonable 1-year survival. Combining membrane oxygenation with RVAD support appears to offer a short-term survival benefit in patients with RV failure after continuous-flow left ventricular assist device implantation.

D-dimers Are a Predictor of Clot Volume Inside Membrane Oxygenators During Extracorporeal Membrane Oxygenation.

Thrombosis inside the membrane oxygenator (MO) is a critical complication during venovenous extracorporeal membrane oxygenation (ECMO). The aim of this study was to prove if thrombotic clots manifest within the MO when D-dimer levels are elevated over a long-term period. Heparin-coated polymethylpentene MOs (n = 13) were exchanged due to high plasma D-dimer levels. Clot volume was calculated using multidetector computed tomography (MDCT). Coagulation parameters and MO function were analyzed before and after MO exchange. Before MO exchange, D-dimer levels increased significantly in each patient (11.5 [6.5-15.5] mg/L to 35.0 [34-35] mg/L, P ≤ 0.001). High levels of D-dimers were tolerated for 1 to 6 days. Additionally, fibrinogen concentration (n = 8) and platelet count decreased (n = 8). Within 48 h after exchange, D-dimer levels decreased significantly (n = 11, 12 [8-16] mg/L, P = 0.004). Fibrinogen concentration and platelet counts increased. Clots were found in all MOs in the inlet part of the device. Clot volume (16-106 cm(3) ) did not correlate with MO support time but increased significantly when high D-dimer levels were accepted for >2 days. An increase or high levels of D-dimers in absence of other explaining pathology during ECMO therapy reflected coagulation activity within the MO. Evidence of clots within the MO at high D-dimer levels and decrease after exchange underline the relevance of D-dimer testing during ECMO treatment. Besides, surveillance of MOs during ongoing ECMO therapy will help to predict clot formation, and to avoid system-induced coagulation disorders as well as critical situations.

Anesthetic management during cardiopulmonary bypass: a systematic review.

Cardiopulmonary bypass (CPB) required for cardiac surgery presents unique challenges to the cardiac anesthesiologist responsible for providing the 3 most basic facets of any anesthetic: amnesia, analgesia, and muscle relaxation. Unique pathophysiologic changes during CPB result in pharmacokinetic alterations that impact the serum and tissue concentrations of IV and volatile anesthetics. Similarly, CPB causes pharmacodynamic alterations that impact anesthetic efficacy. The clinical significance of these alterations represents a "moving target" as practice evolves and the technology of CPB circuitry advances. In addition, perfusionists choose, modify, and maintain the CPB circuitry and membrane oxygenator. Thus, their significance may not be fully appreciated by the anesthesiologist. These issues have a profound impact on the anesthetic state of the patient. The delivery and maintenance of anesthesia during CPB present unique challenges. The perfusionist may be directly responsible for the delivery of anesthetic during CPB, a situation unique to the cardiac suite. In addition, monitors of anesthetic depth-assessment of clinical signs, hemodynamic indicators, the bispectral index monitor, end-tidal anesthetic concentration, or twitch monitoring-are often absent, unreliable, or directly impacted by the unique pathophysiology associated with CPB. The magnitude of these challenges is reflected in the higher incidence of intraoperative awareness during cardiac surgery. Further complicating matters are the lack of specific clinical guidelines and varying international policies regarding medical device specifications that add further layers of complexity and introduce practice variability both within institutions and among nations. We performed a systematic survey of the literature to identify where anesthetic practice during CPB is evidence based (or not), identify gaps in the literature to guide future investigations, and explore the implications of evolving surgical practice, perfusion techniques, and national policies that impact amnesia, analgesia, and muscle relaxation during CPB.

A fetal goat model of the veno-venous extracorporeal life support

Objective To establish a fetal goat model of the veno-venous artificial placenta support.Methods Five pregnant goats with 100 to 140 days gestation underwent cesarean deliver.Veno-venous artificial placentas were established to support fetal goats.The fetal blood drained from right jugular vein was pumped to an umbilical vein via artificial placenta.Fetuses were incubated in the warm saline at 40 ℃.The artificial placenta circuit consisted of a centrifugal pump,a neonatal membrane oxygenator,an uhrafilter,et al.Fetal echocardiography was performed to access fetal cardiac output of two ventricles before support and 3 hours and 6 hours during support.Fetal hemodynamics were monitored and blood gase were assayed during support.Results During support,fetal hemodynamics were stable.The level of Lac increased remarkably [(5.26 ± 1.57) mmol/L vs.(14.04 ± 2.74) mmol/L,P ＜ 0.01] with a slight increase of the potassium.Fetal cardiac output of left ventricle decreased without significant differences.Fetal cardiac output of right ventricle tended to decrease without significant difference at the 6th hour compared with that before support [(264.81 ± 163.57) ml/(kg· min) vs.(208.94 ± 125.99) ml/(kg* min)].Conclusion The veno-venous artificial placenta might be a practicable experimental model for supporting the premature fetuses.However,we were supposed to be careful with the tender and vulnerable tissues. Key words: Extracorporeal life support; Artificial placenta; Fetal goat; Cardiac output

Analysis of thrombotic deposits in extracorporeal membrane oxygenators by multidetector computed tomography.

Oxygenator thrombosis is a serious complication in extracorporeal membrane oxygenation (ECMO) and may necessitate a system exchange. Coagulation and fibrinolysis parameters, flow dynamics, and gas transfer performance are currently used to evaluate the degree of oxygenator thrombosis, but there is no technical approach for direct visualization and quantification of thrombotic deposits within the membrane oxygenator (MO). We used multidetector computed tomography (MDCT) with three-dimensional postprocessing to assess the incidence of oxygenator thrombosis, to quantify thrombus extent, and to localize clot distribution. Twenty heparin-coated MOs after successful weaning were analyzed. Mean ECMO support time was 7 ± 4 days, mean activated partial thromboplastin time (aPTT) during ECMO was 59 ± 20 seconds. Thrombotic deposits were detected in all MOs. The mean clot volume was 51.7 ± 22.3 cm. All thrombotic deposits were located in the venous, i.e., inlet part of the device, without apparent evidence of embolization in patients. There was no correlation between clot volume and ECMO support time or aPTT. Clot formation within the MO is a common finding in ECMO despite adequate systemic anticoagulation. The clinical significance of thrombus formation and its influence on gas exchange capacity and hemostatic complications have to be addressed in further studies.

Numerical analysis of the effects of a high gradient magnetic field on flowing erythrocytes in a membrane oxygenator

Abstract This study was carried out to clarify the effect of a high gradient magnetic field on pressure characteristics of blood in a hollow fiber membrane oxygenator in a solenoid coil by means of numerical analysis. Deoxygenated erythrocytes are paramagnetic, and oxygenated erythrocytes are diamagnetic. Blood changes its magnetic susceptibility depending on whether it is carrying oxygen or not. Motion of blood was analyzed by solving the continuous equation and the Navier–Stokes equation. It was confirmed that oxygenation of deoxygenated blood in the downstream side of the applied magnetic field was effective for pressure rise in a non-uniform magnetic field. The pressure rise was enhanced greatly by an increase in magnetic field intensity. The results suggest that a membrane oxygenator works as an actuator and there is a possibility of self-circulation of blood through an oxygenator in a non-uniform magnetic field.

Contemporary Oxygenator Design Relative to Hemolysis

Hemolysis is a well-known phenomenon during cardiovascular surgery and generally attributed to cardiopulmonary bypass, particularly when using high-resistant oxygenators. This study aimed at investigating whether transoxygenator pressure drop can be considered an independent factor of hemolysis. Additionally, intraoxygenator blood distribution and shear stress were assessed. A low-resistant (LR, n = 3), a moderate-resistant (MR, n = 3), and a high-resistant (HR, n = 3) clinically used membrane oxygenator were tested in vitro using a roller pump and freshly drawn heparinized porcine blood. Flow rates were set to 2 and 4 L/min and maximum flow compliant to the oxygenator type for 1 hour each. As a control, the oxygenator was excluded from the system. Blood samples were taken every 30 minutes for plasma-free hemoglobin assay and transoxygenator pressure was measured inline. Intraoxygenator blood distribution was assessed using an ultrasound dilution technique. Despite the relatively broad spectrum of pressure drop and resultant transoxygenator pressure drops (LR: 14–41 mmHg, MR: 29–115 mmHg, HR: 77–284 mmHg, respectively), no significant association (R2 = .074, p = .22) was found with the normalized index of hemolysis. The shear stress of each oxygenator at maximum flow rate amounted to 3.0 N/m2 (LR), 5.7 N/m2 (MR), and 8.4 N/m2 (HR), respectively. Analysis of blood flow distribution curves (kurtosis and skewness) revealed intraoxygenator blood flow distribution to become more homogeneous when blood flow rates increased. Contemporary oxygenators were shown not to be a predominant factor for red blood cell damage.

A severe case of pneumopathy in a duck breeder due to Chlamydia psittaci diagnosed by 16S rDNA sequencing

Introduction: Psittacosis is a zoonotic infectious disease contracted from birds and caused by Chlamydia psittaci, an obligate intracellular pathogen. In humans, the symptoms of the disease range from inapparent illness to systemic illness with severe pneumonia. Case presentation: A severe case of atypical pneumonia requiring extra‐corporeal membrane oxygenation in a duck breeder is described. Because of the critical urgency of the case described here, and without any clear identification of the pathogen during the first days of hospitalization, treatment had to be adjusted daily. While conventional clinical methods failed to identify the causative agent, C. psittaci was finally identified using broad‐range 16S rDNA PCR analysis performed on a sample of broncho‐alveolar fluid. Conclusion: Owing to the non‐specific clinical signs of psittacosis, early identification of cases of the disease remains a challenge. C. psittaci should be sought in patients presenting severe acute respiratory distress syndrome without any evidence of other infectious causes and especially when exposure to birds or bird products is reported. PCR is a very useful method to help identify fastidious organisms of this kind.

An experimental model of myocardial infarction and controlled reperfusion using a miniaturized cardiopulmonary bypass in rats.

Different revascularization strategies for patients with acute myocardial infarction (AMI) exist. It remains unclear whether ventricular unloading using cardiopulmonary bypass (CPB) or extracorporeal life support (ECLS) has an impact on early postischaemic ventricular function. Here, we report on the results of an approach using a miniaturized CPB in a well-established animal model of AMI. In a randomized fashion, 30 male Wistar rats were assigned to temporary left anterior descending (LAD) ligation (30 min) followed by 180 min of reperfusion either with or without 60 min of CPB (70 ml/min, 36°C). The CPB circuit consisted of a venous reservoir, a peristaltic roller pump and a membrane oxygenator with heat exchanger. Cardiac function was measured at 60 and 120 min after reperfusion (F60, F120) using a conductance catheter. The mortality rate was 37% (11/30). Thus, 19 animals could be included into the analysis (8 CPB). The mean cardiac output did not differ between the groups at F60 [63 ± 29 vs 54 ± 25 ml/min (CPB), P = 0.56] and F120 [73 ± 27 vs 53 ± 24 ml/min (CPB), P = 0.21]. During reperfusion, the mean left ventricular ejection fraction (LVEF) was stable in both the control (F60 37 ± 5% vs F120 33 ± 8%, P = 0.42) and the CPB groups (F60 52 ± 11% vs F120 51 ± 13%, P = 0.71). CPB animals had a significantly better LVEF after reperfusion (F60 P = 0.007, F120 P = 0.01). In this animal model of AMI, the establishment of CPB resulted in a significantly better LVEF in comparison with conventional reperfusion only. This beneficial effect may have an impact on revascularization strategies and timing in patients presenting with AMI in the future.

What Is The Evidence For Oxygenated Hypothermic Machine Perfusion in Kidney Transplantation? A Systematic Review*.

As the increasing demand for organs continues high risk donors represent an additional supply of organs to the donor pool. We systematically reviewed the evidence of ex-vivo hypothermic OMP in kidney donors. We searched Medline, Embase, Cochrane's CENTRAL and Transplant Library for human and animal studies on OMP alone or OMP compared with machine perfusion (MP) in kidney transplantation. Studies had to report patient/animal survival, discard rate, technical complications or renal function. Data were extracted regarding donors/recipients, oxygenation method, preservation time, perfusion temperature/pressure/flow, and outcomes. The search identified 2820 references of which 35 (18 case series, 11 cohort studies, 6 randomised controlled trials) met our inclusion criteria. Four studies were in humans and 31 in animals of which 20 were studies of auto-transplantation. Twelve animal studies in pigs (4), dogs (3), rats (4), and rabbits (1) compared OMP with MP and 23 studies in humans (4), pigs (5), dogs (11) and rats (3) reported on OMP alone. Seven methods of oxygenation were reported: ultrabaric oxygenation, membrane oxygenation, air pump oxygenation, retrograde persufflation, oxygenated persufflation, oxygenated machine perfusion and hyperbaric oxygenation/chamber. OMP was applied either continuously (8 studies) or at the end of the perfusion (27 studies). Perfusion temperature ranged 2-32°C and perfusion time 1-72 hours. There was one direct comparison of OMP and MP in pigs that reported on animal survival which showed rates of 100% for OMP versus 43% for MP. Two other studies (dogs, rats) showed survival rates of 0-100% for OMP and 0-80% for MP. Studies comparing OMP with MP showed conflicting results for renal function. There were no human trials comparing OMP with MP. Studies on OMP alone in humans showed patient survival rates of 50-100% (3 studies). OMP in animals led to survival rates of 0-100% (15 studies) with porcine studies showing survival rates of 33-100% (4 studies). The available evidence for oxygenated hypothermic machine perfusion is poor. There is inconclusive evidence that supplemental oxygenation during HMP improves early renal function. There is very little information from human studies. Thus good quality randomised controlled trials are essential to establish the role of oxygenation with machine perfusion. *Conducted as part of the Consortium for Organ Preservation in Europe (COPE), which is funded by an EU FP7 grant.

The Role of the Contact Pathway in Thrombus Propagation

The continued search for the ideal antithrombotic agent that would prevent or reduce thrombus growth inside blood vessels without an effect on the essential hemostatic functions of blood, including extraluminal thrombin generation and platelet activation, has been going in new directions in the past decade. These directions include studies suggesting that activation of the intrinsic coagulation cascade through contact activation of factor XII, and the resultant thrombin generation is a pathologic event that leads to undesirable consequences. Recent animal studies of contact pathway inhibitors in experimental thrombogenesis suggest that the contact activation pathway of blood coagulation may play a pathogenic role in thrombosis, and pharmacologic inhibition of contact activation may have antithrombotic effects. Development of reasonably potent selective inhibitors of contact activation pathway components or activities now allow for the conduct of studies in various animal species, including primates. These studies have generated interesting data that now support the hypothesis that thrombogenesis in humans may also involve the pathological activation of the intrinsic coagulation cascade. Moreover, baboons, mice, and rabbits, pretreated with antibodies that selectively inhibit factor XII activation, procoagulant factor XIIa activity, or all enzymatic activities of factor XIIa show significantly reduced propensity for occlusive thrombus propagation in various models of acute thrombogenesis on vascular grafts, membrane oxygenators, and even on injured arteries. Since contact activation of blood does not play a demonstrable role in normal hemostasis, and there has been no evidence generated to date suggesting that activation of factor XII has a physiologic function, current research now supports the original concept, developed over 2 decades ago, that temporal pharmacologic inhibition of thrombin generation through the contact pathway may have therapeutic potential and could produce beneficial antithrombotic activities without hemostasis impairment.

Ex‐vivo testing and preclinical heterotopic thoracic cardiac xenotransplantation of multi‐transgenic organs

The heterotopic thoracic pig‐to‐baboon heart transplantation has been established by our group as a safe preclinical model. Since the recipient's own heart remains in place, it is possible to evaluate immunological reactions of various types and the symptoms of the thrombotic microangiopathy under working heart conditions. However, these experiments are complex and costly. In order to limit the number of transplants, we tested our multi‐transgenic porcine donor hearts in an ex‐vivo perfusion model first.Ex‐vivo model: Both beating ventricles were perfused with heparinized freshly drawn human whole blood using a centrifugal pump and a membrane oxygenator. During 3 h of observation, cardiac function parameters were obtained continuously; specimens from the perfusate, coronary sinus blood, and myocardial biopsies were assessed. Various genetically modified porcine donor hearts were tested; we are currently evaluating the impact of human thrombomodulin on the porcine microcirculation; the efficacy of complement regulation is another work package.Pig‐to‐baboon heterotopic cardiac xenotransplantation: In our latest group, seven baboons received five double (Gal‐KO/hCD46), and two triple (Gal‐KO/hCD46/hTM resp./HLA‐E) transgenic pig hearts. Our immunosuppressive regimen included preoperative anti‐CD20‐antibody, bortezomib, dexamethasone and cyclophosphamide; postoperatively, ATG, tacrolimus, MMF, anti‐CD20‐antibody, bortezomib and dexamethasone were administered. Total lymph node irradiation (6 Gy) was applied on postoperative day five.The triple transgenic hearts survived 35 and 37 days respectively. Both hearts maintained function throughout the experiment. Both recipients succumbed to fungal infections. Humoral rejection was seen only once. The next barrier appears to be the complex event of thrombotic microangiopathy that needs to be addressed with the additional expression of human thrombomodulin strategies.

D-dimers as an early marker for oxygenator exchange in extracorporeal membrane oxygenation

PurposeEarly markers of oxygenator dysfunction during prolonged use of extracorporeal membrane oxygenation (ECMO) are important for timely exchange to avoid sudden loss of function due to clot formation within the system. The measurement of d-dimers (DDs) in plasma might be a marker for early diagnosis of thrombus formation and dysfunction of heparin-coated membrane oxygenators (MOs). MethodsThis is a retrospective study on prospectively collected data of 24 adult acute respiratory distress syndrome patients requiring long-term veno-venous ECMO with at least 1 MO exchange. Kinetics of coagulation, inflammation, and oxygenator function were analyzed before and after MO exchange. ResultsMedian (interquartile range) support duration is 20 (15-29) days. Thirty-four MOs had to be replaced. Exchange occurred due to visible thrombus formation in the MO (n = 16), worsening gas exchange (n = 11), increased blood flow resistance (n = 1), and activation of coagulation with diffuse bleeding (n = 6). In 15 cases, DDs were continuously elevated and, therefore, not suitable as marker for MO exchange. In the remaining 19 cases, DDs increased significantly within 3 days before exchange from 15 (9-20) to 30 (21-35) mg/dL (P = .002) and declined significantly within 1 day thereafter to 13 (7-17) mg/dL (P = .003). ConclusionsAn increase in plasma DD concentration in absence of other explaining pathology can be helpful in predicting an MO exchange in miniaturized heparin-coated ECMO systems.

Continuous Renal Replacement Therapy With an Automated Monitor Is Superior to a Free-Flow System During Extracorporeal Life Support*

To determine whether integrated continuous renal replacement therapy provides more accurate fluid management than IV pump free-flow ultrafiltration in pediatric patients on extracorporeal life support. Retrospective study. PICU and neonatal ICU in a tertiary academic center. Infants and children less than 18 years old. Extracorporeal membrane oxygenation and continuous renal replacement therapy. Clinical data collected on patients who received free-flow or integrated renal replacement therapy while on extracorporeal life support. Normalized ultrafiltration error was calculated as: (physician specified fluid loss per 24-hr period - actual fluid loss per 24-hr period) divided by patient body weight (kg). Mixed linear regression analyses were used to model longitudinal ultrafiltration error trajectories within each mode of ultrafiltration. Based on an analysis of 458 serial ultrafiltration fluid balance measurements, integrated ultrafiltration was significantly more accurate than free-flow ultrafiltration (normalized ultrafiltration error of 1.2 vs 13.1 mL; p < 0.001). After adjusting for patient factors and time, integrated ultrafiltration was associated with a significantly lower normalized ultrafiltration error (variable estimate, -24 ± 6; p < 0.001). The use of integrated ultrafiltration was associated with shorter duration of extracorporeal life support (384 vs 583 hr, p < 0.001) and renal replacement therapy (185 vs 477 hr, p < 0.001) than free-flow patients. Overall ICU and hospital length of stay and in-hospital mortality were similar between the groups. While free-flow ultrafiltration has the advantages of simplicity and low cost, integrated renal replacement therapy provides more accurate fluid management during extracorporeal life support. Better fluid status management with integrated renal replacement therapy may contribute to shorter duration of extracorporeal life support.

Flow Dynamics of Different Adult ECMO Systems: A Clinical Evaluation

Membrane oxygenator (MO) failure is a known hazard during venovenous extracorporeal membrane oxygenation (v-v ECMO) therapy. Knowledge about technical and performance details of different ECMO systems (Maquet, Rastatt, Germany; Medos, Stolberg, Germany; Sorin, Modena, Italy) licensed for adults with acute lung failure might improve their handling. This retrospective study comprises 186 adult patients (Regensburg ECMO Registry) treated with v-v ECMO. Flow dynamic data were used to analyze the performance of different blood pumps, cannula types, and MOs to maintain an adequate blood flow (1-5 L/min). Usage of the Medos ECMO system in critically ill patients required a higher pump speed and generated a higher pressure drop across the MO (dpMO), however, without an increase in free plasma hemoglobin. The dpMO depended on the type of MO and increased with blood flow as expected. Type-specific normal values are reported. A distinct increase in dpMO above normal values within 1 day required an immediate MO exchange. This was an infrequent technical complication (3%). Finally, pressure-flow performance of single dual-lumen cannulas (27 Fr) was comparable with small single-lumen cannulas (15 Fr), without an increased risk of technical-induced hemolysis. Despite different performances, all current commercially available adult v-v ECMO systems produce adequate blood flow without an increased risk in technical-induced hemolysis. Familiarity with the specific properties of individual systems allows early detection of technical complications. Additionally, the choice of an adequate cannula requires a closer consideration of the individual patient situation.

Effects of sevoflurane postconditioning on lung function after cardiopulmonary bypass in patients undergoing cardiac valve replacement

Objective To evaluate the effects of sevoflurane postconditioning on lung function after cardiopulmonary bypass (CPB) in patients undergoing cardiac valve replacement.Methods Thirty ASA physical status Ⅱ or Ⅲ patients,aged 33-64 yr,weighing 47-81kg,scheduled for cardiac valve replacement with CPB,were equally and randomly divided into control group (group C) or sevoflurane postconditioning group (group S).Anesthesia was induced with iv injection of midazolam,etomidate,fentanyl and rocuronium.The patients were endotracheally intubated and mechanically ventilated.Anesthesia was maintained with intermittent iv boluses of midazolam,fentanyl and pipecuronium.In group S,2％ sevoflurane was washed into the membrane oxygenator at 2 min before aortic unclamping and continuously washed into the membrane oxygenator for 15 min after aortic unclamping.Before anesthesia (T1),immediately after sternum splitting (T2),at 30 min after termination of CPB (T3),and at 6,12 and 24h after operation (T4-6),blood samples were taken from the radial artery for blood gas analysis and PaO2 and SaO2 were recorded.Oxygen index (OI),alveolar-arterial oxygen tension difference (DA-aO2),dynamic pulmonary compliance (Cdyn) and static pulmonary compliance (Cstat) were calculated.Arterial blood samples were collected at T1,T3,T4 and T6 for determination of serum concentrations of IL-17A,neutrophil elastase (NE) and matrix metalloproteinase-9 (MMP-9).The time of mechanical ventilation after surgery and development of dyspnea,re-intubation and pulmonary rales were recorded.Results Compared with group C,OI at T4T6,PaO2 at T4 and T5,SaO2 at T3 and T6,Cdyn at T3 and T4 and Cstat at T4 were significantly increased,DAaO2 at T5 and T6,serum concentrations of IL-17A,NE and MMP-9 at T3,T4 and T6,and the incidence of pulmonary rales were decreased,and the time of mechanical ventilation was shortened (P ＜ 0.05),and no significant change was found in the incidence of dyspnea in group S (P ＞ 0.05).No re-intubation was required in the two groups.Conclusion Sevoflurane postconditioning can improve the lung function after CPB in patients undergoing cardiac valve replacement and inhibition of inflammatory responses may be involved in the mechanism. Key words: Anesthetics, inhalation; Respiratory function tests; Cardiopulmonary bypass; Heart valve prosthesis implantation

The Dynamic Observation of Plasma Concentration of Antimicrobial Agents During Balanced Ultrafiltration In Vitro

Routine perioperative intravenous antimicrobial agents are administered as surgical prophylaxis. However, whether balanced ultrafiltration during extracorporeal circulation has substantial effect on the concentration of antimicrobial agents remains unclear. The concentrations of antimicrobial agents in plasma and ultrafiltrate samples were measured in this pseudo-extracorporeal circulation model. Extracorporeal circulation consisted of cardiotomy reservoir, membrane oxygenator, and pediatric arterial line filter. A hemoconcentrator was placed between the arterial purge line and oxygenator venous reservoir. Fresh donor human whole blood was added into the circuit and mixed with Ringer's solution to obtain a final hematocrit of 24-28%. Two kinds of antimicrobial agents, cefotiam (320 mg) and cefmetazole (160 mg), were bolus added into the circuit. After 30 min of extracorporeal circulation, zero-balanced ultrafiltration was initiated and arterial line pressure was maintained at approximately 100 mm Hg with a Hoffman clamp. The rate of ultrafiltration (12 mL/min) was controlled by ultrafiltrate outlet pressure. An identical volume of Plasmalyte A was dripped into the circuit to maintain stable hematocrit during 45 min of experiment. Plasma and ultrafiltrate samples were drawn every 5 min, and concentrations of antimicrobial agents (including cefotiam and cefmetazole) were measured with high performance liquid chromatography. Both antimicrobial agents were detected in ultrafiltrate, demonstrating hemoconcentration may remove antimicrobial agents. The concentrations of plasma antimicrobial agents decreased linearly with the increase of ultrafiltrate volume. At end of balanced ultrafiltration, the concentration of plasma cefotiam was 104.96 ± 44.36 mg/L, which is about 44.38% ± 7.42% of the initial concentration (238.95 ± 101.12 mg/L) (P < 0.001); the concentration of plasma cefmetazole decreased linearly to 25.76 ± 14.78 mg/L, which is about 49.69% ± 10.49% of the initial concentration (51.49 ± 28.03 mg/L) (P < 0.001). The total amount of cefotiam in ultrafiltrate is 27.16% ± 12.17% of the total dose administered, whereas cefmetazole in ultrafiltrate is 7.74% ± 4.17%. Balanced ultrafiltration may remove antimicrobial agents from plasma and has a prominent influence on plasma concentration of antimicrobial agent. The strategy of surgical prophylaxis should consider this unique technique during extracorporeal circulation.

Establishment of a novel rat model without blood priming during normothermic cardiopulmonary bypass

An effective animal model was needed for research on the pathophysiology of cardiopulmonary bypass (CPB). Rat models were considered suitable for research into CPB, recently. The aim of the article is to establish a simple and safe CPB model without blood priming in rats, containing the advantages of controlling temperature precisely, being similar to the clinical process and laying the foundation for the further study of a deep hypothermic circulatory arrest (DHCA) model. Ten Sprague-Dawley rats, divided into a CPB group (n=7) and a sham group (n=3), received sevoflurane inhalation anesthesia and were maintained in an anesthesia state by intubation. The entire CPB circuit consisted of a reservoir, a membrane oxygenator, a roller pump, a heat exchanger and a heat cooler, all of which were connected via silicon tubes. The volume of the priming solution, composed of 6% HES130/0.4 and 125 IU heparin, was less than 12 ml. In the CPB group, a 22G catheter was placed in the left femoral artery for monitoring arterial blood pressure, a 20G catheter was placed in a tail artery for arterial inflow and a homemade, multiorificed catheter was inserted into a right jugular vein for venous drainage. After 90 minutes, the CPB process was terminated when vital signs were stable. In the sham group, the same surgical process was conducted except for the venous drainage. Post-oxygenator blood gas and hemodynamic parameters were measured at each time point before CPB, during CPB and after CPB. All CPB processes were successfully achieved. Blood gas analysis and hemodynamic parameters of each time point were in accordance with normal ranges. The vital signs of all rats were stable. The establishment of CPB without blood priming in rats can be achieved successfully. The rat model could be used to study short-term or long-term organ injury mechanisms caused by CPB. Furthermore, on the basis of the precise control of temperature and the depth of anesthesia, the DHCA model in rats could be developed further to study pathophysiological changes of neurological and other organ functions in the future.

Pulsatile flow decreases gaseous micro-bubble filtering properties of oxygenators without integrated arterial filters during cardiopulmonary bypass

Cardiopulmonary bypass (CPB) has a risk of embolic injury with an important role of gaseous micro-bubbles (GMBs), coming from CPB-circuit. Pulsatile perfusion (PP) can provide specific conditions for supplementary GMB-activity with respect to non-pulsatile (NP). We aimed to test GMB-filtering properties of three modern oxygenators under pulsatile and non-pulsatile conditions. Seventy-eight patients undergoing on-pump myocardial revascularization were randomized prospectively into three equal groups according to the oxygenator model used during CPB. Terumo Capiox-FX25, Sorin Synthesis or Maquet Quadrox-i-Adult membrane oxygenators were tested. Each group was divided equally to undergo PP or NP. GMBs were counted by means of a GAMPT-BCC200 bubble-counter with two probes placed at preoxygenator and arterial post-filter positions. Results were evaluated in terms of GMB-volume, GMB-number, amount of large over-ranged GMBs, a series of filtering indices and major neurological outcomes. PP decreased GMB-filtering properties of the tested oxygenators. Those with integrated filters (CAPIOX-FX25 and SYNTHESIS) did not show significant differences between perfusion groups, while QUADROX-i oxygenator with external arterial filter showed significantly higher GMB-volume (P < 0.001), GMB-number (P < 0.001) and amount of over-ranged bubbles (P < 0.001) detected in arterial line during PP. Despite the differences in filtering capacity of all circuits with both types of perfusion, no important differences in clinical outcomes and major neurological events were observed. Pulsatile flow decreases gaseous micro-bubble filtering properties of oxygenators without integrated arterial filters during CPB. PP requires specially designed circuit components to avoid the risk of additional GMB delivery.