Roller and Centrifugal Pumps: A Retrospective Comparison of Bleeding Complications in Extracorporeal Membrane Oxygenation

Blood trauma in veno-venous extracorporeal membrane oxygenation: low pump pressures and low circuit resistance matter

BACKGROUND

Veno-venous extracorporeal membrane oxygenation (VV ECMO) has become standard of care in patients with the most severe forms of acute respiratory distress syndrome. However, hemolysis and bleeding are one of the most frequent side effects, affecting mortality. Despite the widespread use of VV ECMO, current protocols lack detailed, in-vivo data-based recommendations for safe ECMO pump operating conditions. This study aims to comprehensively analyze the impact of VV ECMO pump operating conditions on hemolysis by combining in-silico modeling and clinical data analysis.

METHODS

We combined data from 580 patients treated with VV ECMO in conjunction with numerical predictions of hemolysis using computational fluid dynamics and reduced order modeling of the Rotaflow (Getinge) and DP3 (Xenios) pumps. Blood trauma parameters across 94,779 pump operating points were associated with numerical predictions of shear induced hemolysis.

RESULTS

Minimal hemolysis was observed at low pump pressures and low circuit resistance across all flow rates, whereas high pump pressures and circuit resistance consistently precipitated substantial hemolysis, irrespective of flow rate. However, the lower the flow rate, the more pronounced the influence of circuit resistance on hemolysis became. Numerical models validated against clinical data demonstrated a strong association (Spearman's r = 0.8) between simulated and observed hemolysis, irrespective of the pump type.

CONCLUSIONS

Integrating in-silico predictions with clinical data provided a novel approach in understanding and potentially reducing blood trauma in VV ECMO. This study further demonstrated that a key factor in lowering side effects of ECMO support is the maintenance of low circuit resistance, including oxygenators with the lowest possible resistance, the shortest feasible circuit tubing, and cannulae with an optimal diameter.

Hemolysis performance analysis and a novel estimation model of roller pump system

OBJECTIVE

Hemolysis performance is a crucial criterion for roller pumps utilized in life supporting system. In this study, the factor of hemolysis for roller pumps was selected as the target, and an estimation formulation was built to evaluate its hemolysis.

METHODS

Several models were proposed and then simulated with the assistant of Computational fluid dynamics (CFD) framework. The hemolysis performance was calculated using the power law model based on CFD and the estimation model in accordance with geometry parameters proposed in this study. The results of the in vitro experiments were compared with the simulation results. Power law model with the lowest error was utilized in following analysis.

RESULTS

As indicated by the simulation result, the rotary speed most significantly affected the hemolysis performance of roller blood pumps, followed by roller number and diameter of tube. The index of hemolysis (IH) for roller blood pumps at a rotary speed of 20-100 rpm ranged from 8.73E-7 to 8.07E-5. The relative error of the estimation model (4.93%) was lower than of the power law model (6.78%).

CONCLUSION

The IH led by pumps shows a significant, nonlinear relationship with the rotary speed. The design of multiple rollers design is harmful for hemolysis performance and larger diameter of tube exhibits decreased hemolysis at constant flow rate. An estimation formula was proposed with lower relative error for roller pump with the same shell set, which exhibited reduced computation and elevated convenience. And it can be utilized in hemolysis estimation of roller pumps potentially.

The effects of ECMO on neurological function recovery of critical patients: A double-edged sword

Extracorporeal membrane oxygenation (ECMO) played an important role in the treatment of patients with critical care such as cardiac arrest (CA) and acute respiratory distress syndrome. ECMO is gradually showing its advantages in terms of speed and effectiveness of circulatory support, as it provides adequate cerebral blood flow (CBF) to the patient and ensures the perfusion of organs. ECMO enhances patient survival and improves their neurological prognosis. However, ECMO-related brain complications are also important because of the high risk of death and the associated poor outcomes. We summarized the reported complications related to ECMO for patients with CA, such as north–south syndrome, hypoxic–ischemic brain injury, cerebral ischemia–reperfusion injury, impaired intracranial vascular autoregulation, embolic stroke, intracranial hemorrhage, and brain death. The exact mechanism of ECMO on the role of brain function is unclear. Here we review the pathophysiological mechanisms associated with ECMO in the protection of neurologic function in recent years, as well as the ECMO-related complications in brain and the means to improve it, to provide ideas for the treatment of brain function protection in CA patients.

Computational fluid dynamics analysis and experimental hemolytic performance of three clinical centrifugal blood pumps: Revolution, Rotaflow and CentriMag

Centrifugal blood pumps have become popular for adult extracorporeal membrane oxygenation (ECMO) due to their superior blood handling and reduced thrombosis risk featured by their secondary flow paths that avoid stagnant areas. However, the high rotational speed within a centrifugal blood pump can introduce high shear stress, causing a significant shear-induced hemolysis rate. The Revolution pump, the Rotaflow pump, and the CentriMag pump are three of the leading centrifugal blood pumps on the market. Although many experimental and computational studies have focused on evaluating the hydraulic and hemolytic performances of the Rotaflow and CentriMag pumps, there are few on the Revolution pump. Furthermore, a thorough direct comparison of these three pumps' flow characteristics and hemolysis is not available. In this study, we conducted a computational and experimental analysis to compare the hemolytic performances of the Revolution, Rotaflow, and CentriMag pumps operating under a clinically relevant condition, i.e., the blood flow rate of 5 L/min and pump pressure head of 350 mmHg, for adult ECMO support. In silico simulations were used to characterize the shear stress distributions and predict the hemolysis index, while in vitro blood loop studies experimentally determined hemolysis performance. Comparative simulation results and experimental data demonstrated that the CentriMag pump caused the lowest hemolysis while the Revolution pump generated the highest hemolysis.

Carboxyhemoglobin (CO-Hb) Correlates with Hemolysis and Hospital Mortality in Extracorporeal Membrane Oxygenation: A Retrospective Registry

Background: Patients supported with extracorporeal membrane oxygenation (ECMO) may develop elevated carboxyhemoglobin (CO-Hb), a finding described in the context of hemolysis. Clinical relevance of elevated CO-Hb in ECMO is unclear. We therefore investigated the prognostic relevance of CO-Hb during ECMO support. Methods: Data derives from a retrospective single-center registry study. All ECMO patients in a medical ICU from October 2010 through December 2019 were considered. Peak arterial CO-Hb value during ECMO support and median CO-Hb values determined by point-of-care testing for distinct time intervals were determined. Groups were divided by CO-Hb (<2% or ≥2%). The primary endpoint was hospital survival. Results: A total of 729 patients with 59,694 CO-Hb values met the inclusion criteria. Median age (IQR) was 59 (48−68) years, 221/729 (30.3%) were female, and 278/729 (38.1%) survived until hospital discharge. Initial ECMO configuration was veno-arterial in 431/729 (59.1%) patients and veno-venous in 298/729 (40.9%) patients. Markers for hemolysis (lactate dehydrogenase, bilirubin, hemolysis index, and haptoglobin) all correlated significantly with higher CO-Hb (p < 0.001, respectively). Hospital survival was significantly higher in patients with CO-Hb < 2% compared to CO-Hb ≥ 2%, evaluating time periods 24−48 h (48.6% vs. 35.2%, p = 0.003), 48−72 h (51.5% vs. 36.8%, p = 0.003), or >72 h (56.9% vs. 31.1%, p < 0.001) after ECMO cannulation. Peak CO-Hb was independently associated with lower hospital survival after adjustment for confounders. Conclusions: In ECMO, CO-Hb correlates with hemolysis and hospital survival. If high CO-Hb measured should trigger a therapeutic intervention in order to reduce hemolysis has to be investigated in prospective trials.

The Role of Excessive Anticoagulation and Missing Hyperinflammation in ECMO-Associated Bleeding

Extracorporeal membrane oxygenation (ECMO) is increasingly used in carefully selected patients with cardiac or respiratory failure. However, complications are common and can be associated with worse outcomes, while data on risk factors and outcomes are inconsistent and sparse. Therefore, we sought to investigate potential risk factors and predictors of haemorrhage and adverse events during ECMO and its influence on mortality. We retrospectively reviewed all patients on ECMO support admitted to intensive care units of a tertiary university centre in Austria. In a period of ten years, ECMO support was used in 613 patients, with 321 patients meeting the inclusion criteria of this study. Haemorrhage, occurring in more than one third of the included patients (123, 38%), represented the most common and serious ECMO complication, being associated with an increased one year mortality (51% vs. 35%, p = 0.005). The main risk factors for haemorrhage were severity of the disease (hazard ratio (HR) = 1.01, p = 0.047), a prolonged activated partial thromboplastin time (HR = 1.01, p = 0.007), and lower values of C-reactive protein (HR = 0.96, p = 0.005) and procalcitonin (HR = 0.99, p = 0.029). In summary, haemorrhage remained the main ECMO complication with increased mortality. Moreover, we reported a possible association of lower inflammation and bleeding during ECMO support for the first time. This generated a new hypothesis that warrants further research. Finally, we recommend stricter monitoring of anticoagulation especially in patients without hyperinflammation.

Coagulation complications after conversion from roller to centrifugal pump in neonatal and pediatric extracorporeal membrane oxygenation

BACKGROUND/PURPOSE

Coagulation complications are frequent, unwanted occurrences in extracorporeal membrane oxygenation (ECMO) treatment, possibly influenced by the pump in the ECMO-circuit. We hypothesized that fewer complications would occur with a smaller, heparin-coated ECMO system with a centrifugal pump (CP) than with one with a roller pump (RP) and that after conversion, complication rates would decrease over time.

METHODS

This single-center, retrospective chart study included all first neonatal and pediatric ECMO runs between 2009 and 2015. Differences between groups were assessed with Mann-Whitney U tests and Kruskal-Wallis tests. Determinants of complication rates were evaluated through Poisson regression models. The CP group was divided into three consecutive groups to assess whether complication rates decreased over time.

RESULTS

The RP group comprised 90 ECMO runs and the CP group 82. Hemorrhagic complication rates were significantly higher with the CP than with the RP, without serious therapeutic consequences, while thrombotic complications rates were unaffected. Intracranial hemorrhage rates and coagulation-related mortality rates were similar. Gained experience with the CP did not improve complication rates or survival over time.

CONCLUSIONS

Although the CP seems safe, it does not seem beneficial over the RP. Further research is warranted on how pump type affects coagulation, taking into account the severity and implications of coagulation complications.

LEVEL OF EVIDENCE

Level III.

A Systematic Literature Review of Packed Red Cell Transfusion Usage in Adult Extracorporeal Membrane Oxygenation

Background: Blood product administration plays a major role in the management of patients treated with extracorporeal membrane oxygenation (ECMO) and may be a contributor to morbidity and mortality. Methods: We performed a systematic review of the published literature to determine the current usage of packed red cell transfusions. Predefined search criteria were used to identify journal articles reporting transfusion practice in ECMO by interrogating EMBASE and Medline databases and following the PRISMA statement. Results: Out of 1579 abstracts screened, articles reporting ECMO usage in a minimum of 10 adult patients were included. Full texts of 331 articles were obtained, and 54 were included in the final analysis. All studies were observational (2 were designed prospectively, and two were multicentre). A total of 3808 patients were reported (range 10–517). Mean exposure to ECMO was 8.2 days (95% confidence interval (CI) 7.0–9.4). A median of 5.6% was not transfused (interquartile range (IQR) 0–11.3%, 19 studies). The mean red cell transfusion per ECMO run was 17.7 units (CI 14.2–21.2, from 52 studies) or 2.60 units per day (CI 1.93–3.27, from 49 studies). The median survival to discharge was 50.8% (IQR 40.0–64.9%). Conclusion: Current evidence on transfusion practice in ECMO is mainly drawn from single-centre observational trials and varies widely. The need for transfusions is highly variable. Confounding factors influencing transfusion practice need to be identified in prospective multicentre studies to mitigate potential harmful effects and generate hypotheses for interventional trials.

Hemolysis at low blood flow rates: in-vitro and in-silico evaluation of a centrifugal blood pump

Background

Treating severe forms of the acute respiratory distress syndrome and cardiac failure, extracorporeal membrane oxygenation (ECMO) has become an established therapeutic option. Neonatal or pediatric patients receiving ECMO, and patients undergoing extracorporeal CO₂ removal (ECCO₂R) represent low-flow applications of the technology, requiring lower blood flow than conventional ECMO. Centrifugal blood pumps as a core element of modern ECMO therapy present favorable operating characteristics in the high blood flow range (4 L/min–8 L/min). However, during low-flow applications in the range of 0.5 L/min–2 L/min, adverse events such as increased hemolysis, platelet activation and bleeding complications are reported frequently.

Methods

In this study, the hemolysis of the centrifugal pump DP3 is evaluated both in vitro and in silico, comparing the low-flow operation at 1 L/min to the high-flow operation at 4 L/min.

Results

Increased hemolysis occurs at low-flow, both in vitro and in silico. The in-vitro experiments present a sixfold higher relative increased hemolysis at low-flow. Compared to high-flow operation, a more than 3.5-fold increase in blood recirculation within the pump head can be observed in the low-flow range in silico.

Conclusions

This study highlights the underappreciated hemolysis in centrifugal pumps within the low-flow range, i.e. during pediatric ECMO or ECCO₂R treatment. The in-vitro results of hemolysis and the in-silico computational fluid dynamic simulations of flow paths within the pumps raise awareness about blood damage that occurs when using centrifugal pumps at low-flow operating points. These findings underline the urgent need for a specific pump optimized for low-flow treatment. Due to the inherent problems of available centrifugal pumps in the low-flow range, clinicians should use the current centrifugal pumps with caution, alternatively other pumping principles such as positive displacement pumps may be discussed in the future.

Research of flow dynamics and occlusion condition in roller pump systems used for ventricular assist

Roller pumps have been widely used in the ventricular assist field for many years, while the significant hemolysis caused by its mechanical stress is still a fundamental problem. Although the usual under-occlusion setting was considered as an effective method to reduce the hemolysis rate, its nonocclusive condition of the whole process may cause serious backflow results, which exactly places many restrictions on this method. In this study, the simulation experiments based on computational fluid dynamics (CFD) is conducted, and the occlusion angle is proposed and used to explore a more reliable adjustment form of the occlusion condition. The parameterized geometry of a roller pump is established based on the occlusion angle and other parameters. In order to simulate the motion of the roller, the dynamic mesh mode is introduced to the CFD model, and the analytic formulations used to determine the boundary position are derived. In the whole operation process of the roller pump, four feature positions of the rollers were focused and extracted, and the flow characteristics and the shear stress distribution at these positions were demonstrated. It was found that the entry and exit of the rollers could cause clear shear stress peak, especially when one roller entered, the peak got extremely high. Furthermore, the roller pumps with different occlusion angles were compared, and the results showed that decreasing the occlusion angle could lead to a notable decrease in the amplitude and range of high shear stress and the hemolysis index with a small loss of the occlusion duration. It can be concluded that appropriately decreasing the occlusion angle may be an effective method to alleviate the hemolysis which should be given more attention.

Extracorporeal Membrane Oxygenation for Respiratory Failure

This review focuses on the use of veno-venous extracorporeal membrane oxygenation for respiratory failure across all blood flow ranges. Starting with a short overview of historical development, aspects of the physiology of gas exchange (i.e., oxygenation and decarboxylation) during extracorporeal circulation are discussed. The mechanisms of phenomena such as recirculation and shunt playing an important role in daily clinical practice are explained.Treatment of refractory and symptomatic hypoxemic respiratory failure (e.g., acute respiratory distress syndrome [ARDS]) currently represents the main indication for high-flow veno-venous-extracorporeal membrane oxygenation. On the other hand, lower-flow extracorporeal carbon dioxide removal might potentially help to avoid or attenuate ventilator-induced lung injury by allowing reduction of the energy load (i.e., driving pressure, mechanical power) transmitted to the lungs during mechanical ventilation or spontaneous ventilation. In the latter context, extracorporeal carbon dioxide removal plays an emerging role in the treatment of chronic obstructive pulmonary disease patients during acute exacerbations. Both applications of extracorporeal lung support raise important ethical considerations, such as likelihood of ultimate futility and end-of-life decision-making. The review concludes with a brief overview of potential technical developments and persistent challenges.

The effect of roller head pump on platelet deterioration during the simulated extracorporeal circulation

Roller pumping results in hemolysis and adverse effects on coagulation, but there are few reports on the influence of roller heads on platelets. Here, we evaluate the interaction between roller pumping and platelet function using a simulated extracorporeal circuit incorporating a vinyl chloride tube and roller head pump with 30 min recirculation. Platelet aggregation, platelet count, microparticle, P-selectin, Phosphatidylserine (PS) exposure and Ricinus Communis Agglutinin 1 (RCA-1) were measured before, 5, 10, 20, and 30 min after the recirculation using 100 ml of fresh human blood that had obtained from healthy volunteers (n = 9). Platelet aggregation and platelet count gradually decreased but microparticles significantly increased after the recirculation (P < 0.05). P-selectin, PS exposure and RCA-1 were measured using flow cytometry. There were no significant differences in the P-selectin and PS exposure expression during recirculation. RCA-1, a platelet apoptosis markers, significantly increased 30 min after recirculation (P < 0.05). We thus conclude that roller pumping induced platelet apoptosis and caused decreases in platelet count and aggregation after the recirculation.

Hematologic concerns in extracorporeal membrane oxygenation

This ISTH "State of the Art" review aims to critically evaluate the hematologic considerations and complications in extracorporeal membrane oxygenation (ECMO). ECMO is experiencing a rapid increase in clinical use, but many questions remain unanswered. The existing literature does not address or explicitly state many pertinent details that may influence hematologic complications and, ultimately, patient outcomes. This review aims to broadly introduce modern ECMO practices, circuit designs, circuit materials, hematologic complications, transfusion-related considerations, age- and size-related differences, and considerations for choosing outcome measures. Relevant studies from the 2019 ISTH Congress in Melbourne, which further advanced our understanding of these processes, will also be highlighted.

Lung-kidney interactions in critically ill patients: consensus report of the Acute Disease Quality Initiative (ADQI) 21 Workgroup

BACKGROUND

Multi-organ dysfunction in critical illness is common and frequently involves the lungs and kidneys, often requiring organ support such as invasive mechanical ventilation (IMV), renal replacement therapy (RRT) and/or extracorporeal membrane oxygenation (ECMO).

METHODS

A consensus conference on the spectrum of lung-kidney interactions in critical illness was held under the auspices of the Acute Disease Quality Initiative (ADQI) in Innsbruck, Austria, in June 2018. Through review and critical appraisal of the available evidence, the current state of research, and both clinical and research recommendations were described on the following topics: epidemiology, pathophysiology and strategies to mitigate pulmonary dysfunction among patients with acute kidney injury and/or kidney dysfunction among patients with acute respiratory failure/acute respiratory distress syndrome. Furthermore, emphasis was put on patients receiving organ support (RRT, IMV and/or ECMO) and its impact on lung and kidney function.

CONCLUSION

The ADQI 21 conference found significant knowledge gaps about organ crosstalk between lung and kidney and its relevance for critically ill patients. Lung protective ventilation, conservative fluid management and early recognition and treatment of pulmonary infections were the only clinical recommendations with higher quality of evidence. Recommendations for research were formulated, targeting lung-kidney interactions to improve care processes and outcomes in critical illness.

Outcomes of Infants Supported With Extracorporeal Membrane Oxygenation Using Centrifugal Versus Roller Pumps: An Analysis From the Extracorporeal Life Support Organization Registry

OBJECTIVES

To determine whether mortality differs between roller and centrifugal pumps used during extracorporeal membrane oxygenation in infants weighing less than 10 kg.

DESIGN

Retrospective propensity-matched cohort study.

SETTING

All extracorporeal membrane oxygenation centers reporting to the Extracorporeal Life Support Organization.

PATIENTS

All patients less than 10 kg supported on extracorporeal membrane oxygenation during 2011-2016 within Extracorporeal Life Support Organization Registry.

INTERVENTIONS

Centrifugal and roller pump recipients were propensity matched (1:1) based on predicted probability of receiving a centrifugal pump using demographic variables, indication for extracorporeal membrane oxygenation, central versus peripheral cannulation, and pre-extracorporeal membrane oxygenation patient management.

MEASUREMENTS AND MAIN RESULTS

A total of 12,890 patients less than 10 kg were supported with extracorporeal membrane oxygenation within the Extracorporeal Life Support Organization registry during 2011-2016. Patients were propensity matched into a cohort of 8,366. Venoarterial and venovenous extracorporeal membrane oxygenation runs were propensity matched separately. The propensity-matched cohorts were similar except earlier year of extracorporeal membrane oxygenation (standardized mean difference, 0.49) in the roller pump group. Within the propensity-matched cohort, survival to discharge was lower in the centrifugal pump group (57% vs 59%; odds ratio, 0.91; 95% CI, 0.83-0.99; p = 0.04). Hemolytic, infectious, limb injury, mechanical, metabolic, neurologic, pulmonary, and renal complications were more frequent in the centrifugal pump group. Hemorrhagic complications were similar between groups. Hemolysis mediated the relationship between centrifugal pumps and mortality (indirect effect, 0.023; p < 0.001).

CONCLUSIONS

In this propensity score-matched cohort study of 8,366 extracorporeal membrane oxygenation recipients weighing less than 10 kg, those supported with centrifugal pumps had increased mortality and extracorporeal membrane oxygenation complications. Hemolysis was evaluated as a potential mediator of the relationship between centrifugal pump use and mortality and met criteria for full mediation.

Current Understanding of How Extracorporeal Membrane Oxygenators Activate Haemostasis and Other Blood Components

Extracorporeal membrane oxygenators are used in critical care for the management of severe respiratory and cardiac failure. Activation of the coagulation system is initiated by the exposure of blood to synthetic surfaces and the shear stresses of the circuit, especially from device pumps. Initial fibrinogen deposition and subsequent activation of coagulation factors and complement allow platelets and leucocytes to adhere to oxygenator surfaces and enhance thrombin generation. These changes and others contribute to higher rates of thrombosis seen in these patients. In addition, bleeding rates are also high. Primary haemostasis is impaired by platelet dysfunction and loss of their key adhesive molecules and shear stress causes an acquired von Willebrand defect. In addition, there is also altered fibrinolysis and lastly, administration of systemic anticoagulation is required to maintain circuit patency. Further research is required to fulyl establish the complexities of the haemostatic changes with these devices, and to elucidate the mechanistic changes that are mainly responsible so that plans can be made to reduce their complications and improve management.

Incidence, Outcome, and Predictors of Intracranial Hemorrhage in Adult Patients on Extracorporeal Membrane Oxygenation: A Systematic and Narrative Review

Background: Intracranial hemorrhage (ICH) is a common complication in adults treated with extracorporeal membrane oxygenation (ECMO).

Objectives: The aim of this study was to conduct a systematic review of the literature on the incidence, outcome and predictors of ECMO-associated ICH in adult patients, supplemented by a narrative review of its pathophysiology, management and future perspectives.

Methods: MEDLINE, EMBASE, Cochrane Database of Systematic Reviews and www.clinicaltrials.gov were systematically searched. Studies that reported incidence, outcome or predictors of ECMO-associated ICH in adults (≥18 years) were eligible for inclusion.

Results: Twenty five articles were included in the systematic review. The incidence of ECMO-associated ICH varied between 1.8 and 21 %. Mortality rates in ICH-cohorts varied between 32 and 100 %, with a relative risk of mortality of 1.27–4.43 compared to non-ICH cohorts. An increased risk of ICH was associated with ECMO-duration, antithrombotic therapy, altered intrinsic coagulation, renal failure, need of blood products, rapid hypercapnia at ECMO initiation, and even pre-ECMO morbidity.

Conclusions: ICH is a common complication in adults treated with ECMO and associated with increased mortality. Treating an ICH during ECMO represents a balance between pro- and anticoagulatory demands. Neurosurgical treatment is associated with severe morbidity, but has been successful in selected cases. Future studies should aim at investigating the validity and feasibility of non-invasive monitoring in early detection of ECMO-associated ICH.

Therapeutic Interventions and Risk Factors of Bleeding During Extracorporeal Membrane Oxygenation

Bleeding is the most common complication during extracorporeal membrane oxygenation (ECMO). It is associated with an increased mortality and represents the most frequent cause of preliminary ECMO termination. We performed a retrospective analysis in a single ECMO referral center delineating the risk factors and therapeutic interventions of bleeding during adult ECMO in a total of 59 patients. The median length of ECMO support was 158 hours, with an all-cause mortality of 41%. Bleeding occurred on 40% of the days. On multivariate analysis, fungal pneumonia was the only significant factor associated with the occurrence of a bleeding event. The most common bleeding locations were the ECMO cannulation sites. Termination of ECMO support was the most successful therapeutic intervention, followed by the administration of tranexamic acid, replacement of the membrane oxygenator or the ECMO system, administration of factor VIIa, and repositioning of at least one ECMO cannula. Moreover, the transfusion of platelets was a successful mean, as well as the utilization of desmopressin to enhance platelet function. As such, further delineation of the coagulation disorders during ECMO support to provide a sophisticated pharmacotherapy may stop this serious adverse event.

Factors Associated with Bleeding and Thrombosis in Children Receiving Extracorporeal Membrane Oxygenation

RATIONALE

Extracorporeal membrane oxygenation (ECMO) is used for respiratory and cardiac failure in children but is complicated by bleeding and thrombosis.

OBJECTIVES

(1) To measure the incidence of bleeding (blood loss requiring transfusion or intracranial hemorrhage) and thrombosis during ECMO support; (2) to identify factors associated with these complications; and (3) to determine the impact of these complications on patient outcome.

METHODS

This was a prospective, observational cohort study in pediatric, cardiac, and neonatal intensive care units in eight hospitals, carried out from December 2012 to September 2014.

MEASUREMENTS AND MAIN RESULTS

ECMO was used on 514 consecutive patients under age 19 years. Demographics, anticoagulation practices, severity of illness, circuitry components, bleeding, thrombotic events, and outcome were recorded. Survival was 54.9%. Bleeding occurred in 70.2%, including intracranial hemorrhage in 16%, and was independently associated with higher daily risk of mortality. Circuit component changes were required in 31.1%, and patient-related clots occurred in 12.8%. Laboratory sampling contributed to transfusion requirement in 56.6%, and was the sole reason for at least one transfusion in 42.2% of patients. Pump type was not associated with bleeding, thrombosis, hemolysis, or mortality. Hemolysis was predictive of subsequent thrombotic events. Neither hemolysis nor thrombotic events increased the risk of mortality.

CONCLUSIONS

The incidences of bleeding and thrombosis are high during ECMO support. Laboratory sampling is a major contributor to transfusion during ECMO. Strategies to reduce the daily risk of bleeding and thrombosis, and different thresholds for transfusion, may be appropriate subjects of future trials to improve outcomes of children requiring this supportive therapy.

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.