A comparison study of haemolysis production in three contemporary centrifugal pumps

The Impact of Rotor Axial Displacement Variation on Simulation Accuracy of Fully Magnetic Levitation Centrifugal Blood Pump

The rotor axial displacement of the full magnetic levitation blood pump varies with the operating conditions. The effect of rotor axial displacement on simulation results is unclear. This study aimed to evaluate the effect of rotor axial displacement on the predicted blood pump flow field, hydraulic performance, and hemocompatibility through simulation. This study used the CentriMag blood pump as a model, and conducted computational fluid dynamics simulations to assess the impact of rotor displacement. Considering rotor axial displacement leads to opposite results regarding predicted residence time and thrombotic risk compared with not considering rotor axial displacement. Not considering rotor axial displacement leads to deviations in the predicted values, where the effects on the flow field within the blood pump, ratio of secondary flow, and amount of shear stress >150 Pa are significant. The variation in the back clearance of the blood pump caused by the ideal and actual rotor displacements is the main cause of the above phenomena. Given that the rotor axial displacement significantly impacts the simulation accuracy, the effect of rotor axial displacement must be considered in the simulation.

A comprehensive comparison of the in vitro hemocompatibility of extracorporeal centrifugal blood pumps

Purpose: Blood damage has been associated with patients under temporary continuous-flow mechanical circulatory support. To evaluate the side effects caused by transit blood pumping, in vitro hemocompatibility testing for blood damage in pumps is considered a necessary reference before clinical trials. Methods: The hemocompatibility of five extracorporeal centrifugal blood pumps was investigated comprehensively, including four commercial pumps (the Abbott CentriMag, the Terumo Capiox, the Medos DP3, and the Medtronic BPX-80) and a pump in development (the magAssist MoyoAssist^®). In vitro, hemolysis was tested with heparinized porcine blood at nominal operating conditions (5 L/min, 160 mmHg) and extreme operating conditions (1 L/min, 290 mmHg) using a circulation flow loop. Hematology analyses concerning the blood cell counts and the degradation of high-molecular-weight von Willebrand factor (VWF) during 6-h circulation were also evaluated. Results: Comparing the in vitro hemocompatibility of blood pumps at different operations, the blood damage was significantly more severe at extreme operating conditions than that at nominal operating conditions. The performance of the five blood pumps was arranged in different orders at these two operating conditions. The results also demonstrated superior hemocompatibility of CentriMag and MoyoAssist^® at two operating conditions, with overall low blood damage at hemolysis level, blood cell counts, and degradation of high-molecular-weight VWF. It suggested that magnetic bearings have an advantage in hemocompatibility compared to the mechanical bearing of blood pumps. Conclusion: Involving multiple operating conditions of blood pumps in in vitro hemocompatibility evaluation will be helpful for clinical application. In addition, the magnetically levitated centrifugal blood pump MoyoAssist^® shows great potential in the future as it demonstrated good in vitro hemocompatibility.

The Disconnect Between Extracorporeal Circulation and the Microcirculation: A Review

Extracorporeal circulation (ECC) procedures, such as cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO), take over the function of one or more organs, providing clinicians time to treat underlying pathophysiological conditions. ECMO and CPB carry significant mortality rates for patients, despite prior decades of research focused on the resulting failure of critical organs. Since the focus of these procedures is to support blood flow and provide oxygen-rich blood to tissues, a shift in research toward the effects of ECMO and CPB on the microcirculation is warranted. Along with provoking systemic responses, both procedures disrupt the integrity of red blood cells, causing release of hemoglobin (Hb) from excessive foreign surface contact and mechanical stresses. The effects of hemolysis are especially pronounced in the microcirculation, where plasma Hb leads to nitric oxide scavenging, oxidization, formation of reactive oxygen species, and inflammatory responses. A limited number of studies have investigated the implications of ECMO in the microcirculation, but more work is needed to minimize ECMO-induced reduction of microcirculatory perfusion and consequently oxygenation. The following review presents existing information on the implications of ECMO and CPB on microvascular function and proposes future studies to understand and leverage key mechanisms to improve patient outcomes.

Magnetic levitation pump versus constrained vortex pump: a pilot study on the hemolysis effect during minimal invasive extracorporeal circulation

BACKGROUND

Elevated plasma free hemoglobin is associated with multi-organ injury. In this context, minimally invasive extracorporeal technologies represent a way to reduce this complication following cardiac surgery.

METHODS

We present a pilot study focused on plasma free hemoglobin levels in 40 patients undergoing isolated coronary artery bypass grafting (CABG). The same circuits for minimally invasive extracorporeal circulation (MiECC) were used in all patients. The ECMOLIFE magnetic levitation pump was used in the study group (n = 20), and the AP40 Affinity CP centrifugal blood pump was used in the control group (n = 20).

RESULTS

In the immediate postoperative period, plasma free hemoglobin (PFH) and lactate dehydrogenase (LDH) were significantly lower in the study group than in the control group (10.6 ± 0.7 vs 19.9 ± 0.3 mg/dL, p = 0.034; and 99.16 ± 1.7 vs 139.17 ± 1.5 IU/L, p = 0.027, respectively). Moreover, patients treated with the magnetic levitation pump showed lower creatinine and indirect bilirubin (0.92 vs 1.29 mg/dL, p = 0.030 and 0.6 ± 0.4 vs 1.5 ± 0.9 mg/dL, p = 0.022, respectively) at 24 h after the procedure, and received fewer transfusions during the whole postoperative period (3 vs 9 red blood cell units (RBC), p = 0.017).

CONCLUSION

Our pilot study suggests that the use of magnetically levitated centrifugal pumps for extracorporeal circulation support is associated with a lower risk of hemolysis, though larger studies are warranted to confirm our results.

Platelet, Red Cell, and Endothelial Activation and Injury During Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) can be lifesaving but suffers from high rates of bleeding and repeated transfusions. Current monitoring of blood cell damage during ECMO is limited to platelet counts, hematocrit, and plasma hemoglobin levels. Extracelluar vesicles (EV) are small cell fragments released when cells are activated/injured. The objective was to evaluate flow cytometric measurements of EV during ECMO as an indication of platelet, red cell, and endothelial activation/injury. Samples were collected from 55 patients (1 day to 19 years) during 58 ECMO runs. ECMO activated or injured blood cells, but the extent was highly variable and patient dependent. On average platelet activation was increased sevenfold during ECMO with up to 60-fold increased activation during the first 24 hours in some patients. EV associated with platelet and red-cell injury were increased eightfold on average but up to 200-fold in patients with disseminated intravascular coagulation, severe hemolysis, or massive transfusion. Approximately 9% of ECMO patients showed a red-cell and endothelial activation pattern that was associated with poor prognosis. Extracellular vesicles with autofluorescence similar to bilirubin appeared to come from monocytes processing hemoglobin. ECMO is associated with a highly variable, sustained increase in platelet, red-cell, and endothelial activation and injury that is a combination of circuit and transfusion related events, the patients underlying condition and possibly genetic influences on blood cell activation and injury. Extracellular vesicle measurements may improve our understanding of cellular activation and injury during ECMO as we work to improve the biocompatibility of these systems.

Hemocompatibility of new magnetically-levitated centrifugal pump technology compared to the CentriMag adult pump

The specific hemocompatibility properties of mechanical-circulatory-support (MCS)-pump technologies have not previously been described in a comparable manner. We thus investigated the hemocompatibility-indicating marker of a new magnetically-levitated (MagLev) centrifugal pump (MT-Mag) in a human, whole-blood mock-loop for 360 min using the MCS devices as a driving component. We compared those results with the CentriMag adult (C-Mag) device under the same conditions according to ISO10993-4. Blood samples were analyzed via enzyme-linked-immunosorbent-assay (ELISA) for markers of coagulation, complement system, and the inflammatory response. The time-dependent activation of the coagulation system was measured by detecting thrombin-anti-thrombin complexes (TAT). The activation of the complement system was determined by increased SC5b-9 levels in both groups. A significant activation of neutrophils (PMN-elastase) was detected within the C-Mag group, but not in the MT-Mag group. However, the amount of PMN-elastase at 360 min did not differ significantly between groups. The activation of the complement and coagulation system was found to be significantly time-dependent in both devices. However, coagulation activation as determined by the TAT level was lower in the MT-Mag group than in the C-Mag group. This slight disparity could have been achieved by the optimized secondary flow paths and surface coating, which reduces the interaction of the surface with blood.

Transapical ProtekDuo Rapid Deployment Cannula as Temporary Left Ventricular Assist Device in a Jehovah's Witness Patient

Temporary left ventricular support aims to decompress the left ventricle and provide adequate forward flow into the arterial circulation. This can be accomplished with endovascular devices such as the Impella with an internal motor, or with the implementation of cannulae to drain the left ventricle or left atrium and then return to the arterial circulation using an external pump. In this report, the authors describe the transesophageal echocardiography-guided placement of a single-cannula system with the Protek Duo RD (TandemLife, LivaNova) via a left ventricular apical approach to provide minimally invasive left ventricular support in a high-risk Jehovah's Witness patient.

Efficacy of Plasma free Hemoglobin for detecting centrifugal pump thrombosis

INTRODUCTION

Lactate dehydrogenase (LDH) is widely used as an indicator of pump thrombosis in a centrifugal pump. However, due to the low specificity of LDH, pump thrombosis is difficult to detect in the clinical environment. We measured plasma free hemoglobin (pfHb) with the portable device in ICU. The goal of this investigation is to evaluate its diagnostic ability for pump thrombosis.

METHODS

We enrolled 31 consecutive patients who needed Extracorporeal Membrane Oxygenation (ECMO) therapy and pfHb was determined with HemoCue^® plasma/Low Hb photometer. Pump thrombosis was analyzed macroscopically at the timing of pump explantation or exchange. Also, we divided the pump thrombosis into a grading scale by the place of thrombosis.

RESULTS

The median of peak pfHb was significantly lower in the none thrombus group (0.03 g/dL) than that of in the thrombus group (0.05g/dL) (p = 0.01). In our grading criteria, pfHb was significantly higher when the thrombus is existing near the shaft (p = 0.015). Contrary, no significant difference was found for LDH.The ROC analysis of pfHb revealed an AUC of 0.77 for detecting pump thrombosis with the best statistical cutoff value at 0.05 g/dL (specificity, 78%; sensitivity, 77%). Also, ROC analysis of LDH was performed (AUC, 0.44; cutoff value, 1200 IU/L; specificity, 59%; sensitivity, 54%) and compared with pfHb. AUC was significantly higher in pfHb (p = 0.04).

CONCLUSION

Our results showed the efficacy of pfHb for detecting centrifugal pump thrombosis.

Haemolysis induced by mechanical circulatory support devices: unsolved problems

Since the use of continuous flow blood pumps as ventricular assist devices is standard, the problems with haemolysis have increased. It is mainly induced by shear stress affecting the erythrocyte membrane. There are many investigations about haemolysis in laminar and turbulent blood flow. The results defined as threshold levels for the damage of erythrocytes depend on the exposure time of the shear stress, but they are very different, depending on the used experimental methods or the calculation strategy. Here, the results are resumed and shown in curves. Different models for the calculation of the strengths of erythrocytes are discussed. There are few results reported about tests of haemolysis in blood pumps, but some theoretical approaches for the design of continuous flow blood pumps according to low haemolysis have been investigated within the last years.

Hemolysis and methemoglobinemia in a child with left ventricular assist Levitronix PediMag

A 5-month-old male was treated with left ventricular assist device due to cardiac failure secondary to dilated cardiomyopathy. The patient developed acute severe intravascular hemolysis with methemoglobinemia and renal failure, related to a mechanical problem due to pump cylinder misalignment. Secondary severe methemoglobinemia has not been previously described in patients undergoing ventricular assist device. Early detection of the signs and symptoms of hemolysis is crucial to prevent further complications.

Factors associated with hemolysis during extracorporeal membrane oxygenation (ECMO)-Comparison of VA- versus VV ECMO

Venovenous (VV) and venoarterial (VA) extracorporeal membrane oxygenation (ECMO) are effective support modalities to treat critically ill patients. ECMO-associated hemolysis remains a serious complication. The aim was to disclose similarities and differences in VA- and VV ECMO-associated hemolysis. This is a retrospective single-center analysis (January 2012 to September 2018) including 1,063 adult consecutive patients (VA, n = 606; VV, n = 457). Severe hemolysis (free plasma hemoglobin, fHb > 500 mg/l) during therapy occurred in 4% (VA) and 2% (VV) (p≤0.001). VV ECMO showed significantly more hemolysis by pump head thrombosis (PHT) compared to VA ECMO (9% vs. 2%; p≤0.001). Pretreatments (ECPR, cardiac surgery) of patients who required VA ECMO caused high fHb pre levels which aggravates the proof of ECMO-induced hemolysis (median (interquartile range), VA: fHb pre: 225.0 (89.3–458.0); VV: fHb pre: 72.0 (42.0–138.0); p≤0.001). The survival rate to discharge from hospital differed depending on ECMO type (40% (VA) vs. 63% (VV); p≤0.001). Hemolysis was dominant in VA ECMO patients, mainly caused by different indications and not by the ECMO support itself. PHT was the most severe form of ECMO-induced hemolysis that occurs in both therapies with low frequency, but more commonly in VV ECMO due to prolonged support time.

Impact of cannula size and line length on venous line pressure in pediatric VA-/VV-ECLS circuits

The objective of this study was to do an in vitro evaluation of venous line pressure using different venous line lengths and venous cannula sizes in pediatric venoarterial extracorporeal life support (VA-ECLS) and venovenous ECLS (VV-ECLS) circuits. The pediatric VA-ECLS circuit consisted of a Xenios i-cor diagonal pump, a Maquet Quadrox-i pediatric oxygenator, a Medtronic Biomedicus arterial cannula, a Biomedicus venous cannula, and 1/4″ ID arterial and venous tubing. The pediatric VV-ECLS circuit was similar, except it included a Maquet Avalon ELITE bi-caval dual lumen cannula. Circuits were primed with lactated Ringer's solution and packed red blood cells (hematocrit 40%). Trials were conducted at various flow rates (VA-ECLS: 250-1250 mL/min, VV-ECLS: 250-2000 mL/min) using different venous tubing lengths (2, 4, and 6 feet) and cannula sizes (VA-ECLS: A8Fr/V10Fr, A10Fr/V12Fr and A12Fr/V14Fr, VV-ECLS: 13Fr, 16Fr, 19Fr, 20Fr and 23Fr) at 36°C. Real-time pressure and flow data were recorded for analysis. The use of a small-caliber venous cannula significantly increased the venous line pressure in the 2 pediatric circuits (P < 0.01). Shorter venous tubing lengths significantly reduced the venous line pressure at high flow rates (P < 0.01). The VV-ECLS circuit had larger negative pre-pump pressure drops (7.2 to -102.2 mm Hg) when compared to the VA-ECLS circuit (0.7 to -60.7 mm Hg). Selecting an appropriate venous cannula and a shorter venous tubing when feasible may significantly reduce the pressure drop of the venous line in pediatric VA-ECLS and VV-ECLS circuits and improve venous drainage.

Extracellular vesicles: biomarkers and regulators of vascular function during extracorporeal circulation

Extracellular vesicles (EVs) are generated at increased rates from parenchymal and circulating blood cells during exposure of the circulation to abnormal flow conditions and foreign materials associated with extracorporeal circuits (ExCors). This review describes types of EVs produced in different ExCors and extracorporeal life support (ECLS) systems including cardiopulmonary bypass circuits, extracorporeal membrane oxygenation (ECMO), extracorporeal carbon dioxide removal (ECCO₂R), apheresis, dialysis and ventricular assist devices. Roles of EVs not only as biomarkers of adverse events during ExCor/ECLS use, but also as mediators of vascular dysfunction are explored. Manipulation of the number or subtypes of circulating EVs may prove a means of improving vascular function for individuals requiring ExCor/ECLS support. Strategies for therapeutic manipulation of EVs during ExCor/ECLS use are discussed such as accelerating their clearance, preventing their genesis or pharmacologic options to reduce or select which and how many EVs circulate. Strategies to reduce or select for specific types of EVs may prove beneficial in preventing or treating other EV-related diseases such as cancer.

Current trends in neonatal ECMO

Extracorporeal membrane oxygenation (ECMO) is a life-saving therapy for patients with respiratory and cardiac failure refractory to maximal medical management. The extracorporeal life support organization registry is the largest available resource for describing the population and outcomes of patients treated with this therapy. The use of ECMO for neonatal patients is decreasing in proportion to the total annual ECMO runs most likely due to advancements in medical management. Although the overall survival for neonatal ECMO has decreased, this is likely a reflection of the increasingly complex neonatal patients treated with this therapy. Although many patient and mechanical complications are decreasing over time, there remains a high percentage of morbidities and risks associated with ECMO. Continued refinements in management strategies are important to improving overall patient outcomes.

Extracorporeal techniques in acute respiratory distress syndrome

Extracorporeal membrane oxygenation (ECMO) was first introduced for patients with acute respiratory distress syndrome (ARDS) in the 1970s. However, enthusiasm was tempered due to the high mortality seen at that time. The use of ECMO has grown considerably in recent years due to technological advances and the evidence suggesting potential benefit. While the efficacy of ECMO has yet to be rigorously demonstrated with high-quality evidence, it has the potential not only to have a substantial impact on outcomes, including mortality, but also to change the paradigm of ARDS management.

In Vitro Evaluation of an Alternative Neonatal Extracorporeal Life Support Circuit on Hemodynamic Performance and Bubble Trap

The objective of this study was to evaluate an alternative neonatal extracorporeal life support (ECLS) circuit with a RotaFlow centrifugal pump and Better-Bladder (BB) for hemodynamic performance and gaseous microemboli (GME) capture in a simulated neonatal ECLS system. The circuit consisted of a Maquet RotaFlow centrifugal pump, a Quadrox-iD Pediatric diffusion membrane oxygenator, 8 Fr arterial cannula, and 10 Fr venous cannula. A "Y" connector was inserted into the venous line to allow for comparison between BB and no BB. The circuit and pseudopatient were primed with lactated Ringer's solution and packed human red blood cells (hematocrit 35%). All hemodynamic trials were conducted at flow rates ranging from 100 to 600 mL/min at 36°C. Real-time pressure and flow data were recorded using a data acquisition system. For GME testing, 0.5 cc of air was injected via syringe into the venous line. GME were detected and characterized with or without the BB using the Emboli Detection and Classification Quantifier (EDAC) System. Trials were conducted at flow rates ranging from 200 to 500 mL/min. The hemodynamic energy data showed that up to 75.2% of the total hemodynamic energy was lost from the circuit. The greatest pressure drops occurred across the arterial cannula and increased with increasing flow rate from 10.1 mm Hg at 100 mL/min to 114.3 mm Hg at 600 mL/min. The EDAC results showed that the BB trapped a significant amount of the GME in the circuit. When the bladder was removed, GME passed through the pump head and the oxygenator to the arterial line. This study showed that a RotaFlow centrifugal pump combined with a BB can help to significantly decrease the number of GME in a neonatal ECLS circuit. Even with this optimized alternative circuit, a large percentage of the total hemodynamic energy was lost. The arterial cannula was the main source of resistance in the circuit.

A single center’s conversion from roller pump to centrifugal pump technology in extracorporeal membrane oxygenation

Overview:

Recent advances in blood pump technology have led to an increased use of centrifugal pumps for prolonged extracorporeal membrane oxygenation (ECMO). Data from the Extracorporeal Life Support Organization confirms that many institutions have converted to centrifugal pumps after prior experience with roller pump technology. Centrifugal pump technology is more compact and may generate less heat and hemolysis than a conventional roller pump. Based on the potential advantages of centrifugal pumps, a decision was made institution-wide to convert to centrifugal pump technology in pediatric implementation of ECMO. Based on limited prior experience with centrifugal pumps, a multidisciplinary approach was used to implement this new technology. The new centrifugal pump (Sorin Revolution, Arvada, CO) was intended for ECMO support in the cardiac intensive care unit (CICU), the pediatric intensive care unit (PICU) and the neonatal intensive care unit (NICU).

Description:

The perfusion team used their knowledge and expertise with centrifugal pumps to create the necessary teaching tools and interactive training sessions for the technical specialists who consisted primarily of registered nurses and respiratory therapists. The first phase consisted of educating all personnel involved in the care of the ECMO patient, followed by patient implementation in the CICU, followed by the PICU and NICU.

Conclusion:

The institution-wide conversion took several months to complete and was well received among all disciplines in the CICU and PICU. The NICU personnel did use the centrifugal pump circuit, but decided to revert back to using the roller pump technology. A systematic transition from roller pump to centrifugal pump technology with a multidisciplinary team can ensure a safe and successful implementation.

Thrombosis in Centrifugal Pumps: Location and Composition in Clinical and in Vitro Circuits

Purpose

Extracorporeal membrane oxygenation (ECMO) is a form of cardiopulmonary mechanical life support for critically ill patients. ECMO is burdened by both thrombotic and hemorrhagic complications. Recently there has been a clinical shift from roller pumps to centrifugal pumps. In this study, we report on bulk thrombus formation within pumps recovered from clinical use. We then replicate this thrombus formation in vitro.

Methods

Clinical pediatric ECMO circuits driven with the Sorin Revolution were collected from 16 patients. The location and extent of thrombus formation in the pumps were recorded. Pump heads were also tested in a laboratory circulatory loop. The location, extent, and appearance of the thrombi were recorded. Thrombi were examined histologically using Carstairs' stain.

Results

Gross thrombus was observed in all pump heads at the stainless steel bearing at the inlet. In 19% of the pumps larger thrombi grew into the head over the cone and along the vanes. The thrombi were adherent and cohesive upon extraction. The thrombus formation was strikingly similar between the clinical pump heads and in vitro pump heads. Histology of both clinical and experimental samples exhibited a platelet-rich thrombus.

Conclusions

Our studies have revealed platelet-rich thrombus in clinical and in vitro circuits. The location and composition of the thrombi suggest that the exposed metal shaft was initially covered by contact activated coagulation followed by large-scale growth by rapid platelet accumulation from high shear rates at the inlet. The in vitro system may be used to further identify the mechanisms for pump thrombus and test new designs.

Improved Outcome of Cardiac Extracorporeal Membrane Oxygenation in Infants and Children Using Magnetic Levitation Centrifugal Pumps

Extracorporeal membrane oxygenation (ECMO) has traditionally been and, for the most part, still is being performed using roller pumps. Use of first-generation centrifugal pumps has yielded controversial outcomes, perhaps due to mechanical properties of the same and the ensuing risk of hemolysis and renal morbidity. Latest-generation centrifugal pumps, using magnetic levitation (ML), exhibit mechanical properties which may have overcome limitations of first-generation devices. This retrospective study aimed to assess the safety and efficacy of veno-arterial (V-A) ECMO for cardiac indications in neonates, infants, and children, using standard (SP) and latest-generation ML centrifugal pumps. Between 2002 and 2014, 33 consecutive neonates, infants, and young children were supported using V-A ECMO for cardiac indications. There were 21 males and 12 females, with median age of 29 days (4 days-5 years) and a median body weight of 3.2 kg (1.9-18 kg). Indication for V-A ECMO were acute circulatory collapse in ICU or ward after cardiac repair in 16 (49%) patients, failure to wean after repair of complex congenital heart disease in 9 (27%), fulminant myocarditis in 4 (12%), preoperative sepsis in 2 (6%), and refractory tachy-arrhythmias in 2 (6%). Central cannulation was used in 27 (81%) patients and peripheral in 6. Seven (21%) patients were supported with SP and 26 (79%) with ML centrifugal pumps. Median duration of support was 82 h (range 24-672 h), with 26 (79%) patients weaned from support. Three patients required a second ECMO run but died on support. Seventeen (51%) patients required peritoneal dialysis for acute renal failure. Overall survival to discharge was 39% (13/33 patients). All patients with fulminant myocarditis and with refractory arrhythmias were weaned, and five (83%) survived, whereas no patient supported for sepsis survived. Risk factors for hospital mortality included lower (<2.5 kg) body weight (P = 0.02) and rescue ECMO after cardiac repair (P = 0.03). During a median follow-up of 34 months (range 4-62 months), there were three (23%) late deaths and two late survivors with neurological sequelae. Weaning rate (5/7 vs. 21/26, P = NS) and prevalence of renal failure requiring dialysis (4/7 vs. 13/26, P = NS) were comparable between SP and ML ECMO groups. Patients supported with ML had a trend toward higher hospital survival (1/7 vs. 12/26, P = 0.07) and significantly higher late survival (0/7 vs. 10/26, P = 0.05). The present experience shows that V-A ECMO for cardiac indications using centrifugal pumps in infants and children yields outcomes absolutely comparable to international registry (ELSO) data using mostly roller pumps. Although changes in practice may have contributed to these results, use of ML centrifugal pumps appears to further improve end-organ recovery and hospital and late survival.

Plasma Free Hemoglobin Is an Independent Predictor of Mortality among Patients on Extracorporeal Membrane Oxygenation Support

Background

Hemolysis is common in all extracorporeal circuits as evident by the elevated plasma free hemoglobin (PFHb) level. We investigated whether increased hemolysis during extracorporeal membrane oxygenation (ECMO) is an independent mortality predictor.

Methods

We performed a retrospective observational study of consecutive subjects who received ECMO at a tertiary care facility from 2007-2013 to investigate independent predictors of in-hospital mortality. We examined variables related to patient demographics, comorbidities, markers of hemolysis, ECMO characteristics, transfusion requirements, and complications. 24-hour PFHb> 50 mg/dL was used as a marker of severe hemolysis.

Results

154 patients received ECMO for cardiac (n= 115) or pulmonary (n=39) indications. Patients’ mean age was 51 years and 75.3% were males. Compared to nonsurvivors, survivors had lower pre-ECMO lactic acid (p=0.026), lower 24-hour lactic acid (p=0.023), shorter ECMO duration (P=0.01), fewer RBC transfusions on ECMO (p=0.008) and lower level of PFHb 24-hours post ECMO implantation (p=0.029). 24-hour PFHb> 50 mg/dL occurred in 3.9 % versus 15.5% of survivors and nonsurvivors, respectively, p=0.002. A Cox proportional hazard analysis identified PFHb> 50 mg/dL 24-hours post ECMO as an independent predictor of mortality (OR= 3.4, 95% confidence interval: 1.3 – 8.8, p= 0.011).

Conclusion

PFHb> 50 mg/dL checked 24-hour post ECMO implantation is a useful tool to predict mortality. We propose the routine checking of PFHb 24-hours after ECMO initiation for early identification and treatment of the cause of hemolysis.

Extracorporeal circulatory approaches to treat acute respiratory distress syndrome

The early history of extracorporeal membrane oxygenation (ECMO) for adult patients with the acute respiratory distress syndrome (ARDS) evolved slowly over decades, a consequence of extracorporeal technology with high risk and unclear benefit. However, advances in component technology, accumulating evidence, and growing experience in recent years have resulted in a resurgence of interest in ECMO. Extracorporeal support, though currently lacking high-level evidence, has the potential to improve outcomes, including survival, in ARDS. In the near future, novel extracorporeal management strategies may, in fact, lead to a new paradigm in the approach to certain patients with ARDS.

Veno-venous ECMO: a synopsis of nine key potential challenges, considerations, and controversies

Background

Following the 2009 H1N1 Influenza pandemic, extracorporeal membrane oxygenation (ECMO) emerged as a viable alternative in selected, severe cases of ARDS. Acute Respiratory Distress Syndrome (ARDS) is a major public health problem. Average medical costs for ARDS survivors on an annual basis are multiple times those dedicated to a healthy individual. Advances in medical and ventilatory management of severe lung injury and ARDS have improved outcomes in some patients, but these advances fail to consistently “rescue” a significant proportion of those affected.

Discussion

Here we present a synopsis of the challenges, considerations, and potential controversies regarding veno-venous ECMO that will be of benefit to anesthesiologists, surgeons, and intensivists, especially those newly confronted with care of the ECMO patient. We outline a number of points related to ECMO, particularly regarding cannulation, pump/oxygenator design, anticoagulation, and intravascular fluid management of patients. We then address these challenges/considerations/controversies in the context of their potential future implications on clinical approaches to ECMO patients, focusing on the development and advancement of standardized ECMO clinical practices.

Summary

Since the 2009 H1N1 pandemic ECMO has gained a wider acceptance. There are challenges that still must be overcome. Further investigations of the benefits and effects of ECMO need to be undertaken in order to facilitate the implementation of this technology on a larger scale.

Centrifugal pump performance during low-flow extracorporeal CO2 removal; safety considerations

AIM

The aim of this study was to examine the hydrodynamic performance and gaseous microemboli (GME) activity of two centrifugal pumps for possible use in low-flow extracorporeal CO2 removal.

MATERIALS & METHODS

The performance of a Rotassist 2.8 and a Rotaflow 32 centrifugal pump (Maquet Cardiopulmonary AG, Hirrlingen, Germany) was evaluated in a water-glycerine mixture-filled in vitro circuit that enabled measurement of pressures and GME at the pump inlet and pump outlet. Pressure-flow curves were acquired in a 1,000 to 5,000 rpm range while increasing drainage resistance in one series and outlet resistance in another.

RESULTS

Respective minimum pump inlet and maximum pump outlet pressures were -539 mmHg and 754 mmHg for the Rotassist 2.8 and -606 mmHg and 806 mmHg for the Rotaflow 32. Maximum standard deviations on pump pressures and flow amounted to 3.0 mmHg and 0.03 L/min, respectively, regardless of pump type and drainage or outlet resistance. The GME at the pump outlet were detectable at pump inlet pressures below -156 mmHg at 0.2 L/min and 2,500 rpm for the Rotassist 2.8 and below -224 mmHg at 0.9 L/min and 3,000 rpm for the Rotaflow 32.

CONCLUSION

Both the Rotassist 2.8 and Rotaflow 32 centrifugal pumps show a comparably high hydrodynamic stability, but potential GME formation with decreasing pump inlet pressures should be taken into account to ensure safe centrifugal pump-based low-flow extracorporeal CO2 removal.