Coagulation and anticoagulation in extracorporeal membrane oxygenation

Gaseous Nitric Oxide-Cangrelor Combination to Prevent Clots in Extracorporeal Life Support System

INTRODUCTION

The objective of this study was to investigate the potential synergistic utility of a combination of gaseous nitric oxide (gNO)-intravenous Cangrelor as an effective pharmacological option for the prevention of thrombosis in an animal model of extracorporeal life support (ECLS) circuits.

METHODS

10 newborn lambs were placed on ECLS. 5 of them were administered a combination of gNO and intravenous Cangrelor. The remaining 5 were not administered any anticoagulant. The primary end point was duration of ECLS without clot formation. The secondary outcome measure was the absolute maximum transmembrane pressure gradient.

RESULTS

The mean duration of ECLS were 168 min (standard deviation 224.98 min) in the control group and 402 min (standard deviation 287.5 min) in the experimental group (P = 0.17). The peak trans-oxygenator pressure difference was 43 mm Hg (standard deviation 23 mm Hg) in the control group and 62 mm Hg (standard deviation 71 mm Hg) in the experimental group(P = 0.64). Two animals in the experimental group were supported up to 12 h without clot formation. Clot formation in the experimental group occurred after placement of the cannulae but prior to initiation of ECLS flows after cannulation.

CONCLUSIONS

A combination of gNO and Cangrelor is prevents clot formation in an experimental animal model when administered through a clean clot-free circuit. However, the combination s ineffective when there are pre-existing clots in the circuit. A bolus of anticoagulation prior to cannulation is needed prior to testing this combination in future studies with a larger sample size.

Predictors of Mediastinal Exploration While on Extracorporeal Membrane Oxygenation After Pediatric Cardiac Surgery

Cardiac surgical patients requiring extracorporeal membrane oxygenation (ECMO) are at increased risk for hemorrhage due to necessary anticoagulation, in-situ cannulas, and disturbed hemostasis. We performed a retrospective, cross-sectional study of patients 0-18 years old in our cardiac intensive care unit (CICU) cannulated to ECMO within 48 h of cardiopulmonary bypass. The 69 patients included in the study were divided into three analysis groups based on serial chest tube output per hour: no bleeding (NB) on admission to the CICU (21/69, 30%), bleeding stopped (BS) with medical management (26/69, 38%), bleeding requiring emergent mediastinal exploration (BME) (22/69, 32%). The NB group had a more favorable coagulation profile upon admission to the CICU (PTT 53 s NB, 105 s BS, 83 s BME p < 0.001, ACT 169 s NB, 225 s BS, 211 s BME, p =0.013). Only chest tube output during the first three postcannulation hours remained associated with the need for mediastinal exploration by multivariable analysis. An average chest-tube output of 11.6 mL/kg/h during the first three hours had the highest percentage of patients classified correctly (84%) for requiring mediastinal exploration during their ECMO run (sensitivity 91%, specificity 81%).

Antithrombin III infusion improves anticoagulation in congenital diaphragmatic hernia patients on extracorporeal membrane oxygenation

PURPOSE

Achieving effective anticoagulation during neonatal extracorporeal membrane oxygenation (ECMO) without increasing the risk of hemorrhage remains challenging. The use of antithrombin III (AT-III) for this purpose has been examined, but studies have been limited to intermittent bolus dosing. We aimed to evaluate the efficacy and safety of an institutionally developed AT-III continuous infusion protocol in neonates receiving ECMO for the treatment of congenital diaphragmatic hernia (CDH).

METHODS

In this single center, retrospective study, all neonates with a CDH who received ECMO support during the study period were included. Data on anticoagulation labs and therapy, life-threatening bleeding, and circuit changes were analyzed.

RESULTS

Eleven patients were divided into two groups: patients with AT-III continuous infusion (n = 5) and without (n = 6). There were no differences in the gestational age (p = 0.29), sex (p = 1.00), ECMO duration (p = 0.59), or initial AT-III levels (p = 0.76) between groups. Patients in the AT-III infusion group had on average 18.5% higher AT-III levels (p < 0.0001). Patients receiving continuous AT-III infusions spent a significantly higher percentage of ECMO time within the therapeutic range, measured using anti-Factor Xa levels (64.9±4.2% vs. 29.1±8.57%, p = 0.008), and required fewer changes to the heparin infusion rate (6.48±0.88 vs 2.38±0.36 changes/day changes/day, p = 0.005). Multivariate analysis revealed continuous infusion of AT-III did not increase the rate of intracranial or surgical bleeding (p = 0.27).

CONCLUSION

AT-III as a continuous infusion in CDH neonates on ECMO provides a decreased need to modify heparin infusion and more consistent therapeutic anticoagulation without increasing the risk of life-threatening bleeding.

Management of Anticoagulation during Extracorporeal Membrane Oxygenation in Children

Extracorporeal Membrane Oxygenation (ECMO) is often used in critically ill children with severe cardiopulmonary failure. Worldwide, about 3600 children are supported by ECMO each year, with an increase of 10% in cases per year. Although anticoagulation is necessary to prevent circuit thrombosis during ECMO support, bleeding and thrombosis are associated with significantly increased mortality risk. In addition, maintaining balanced hemostasis is a challenging task during ECMO support. While heparin is a standard anticoagulation therapy in ECMO, recently, newer anticoagulant agents are also in use. Currently, there is a wide variation in anticoagulation management and diagnostic monitoring in children receiving ECMO. This review intends to describe the pathophysiology of coagulation during ECMO support, review of literature on current and newer anticoagulant agents, and outline various diagnostic tests used for anticoagulation monitoring. We will also discuss knowledge gaps and future areas of research.

The role of nafamostat mesilate as a regional anticoagulant during extracorporeal membrane oxygenation

Background

Anticoagulation during extracorporeal membrane oxygenation (ECMO) usually is required to prevent thrombosis. The aim of this study was to investigate the usefulness of nafamostat mesilate (NM) as a regional anticoagulant during veno-arterial ECMO (VA-ECMO) treatment.

Methods

We retrospectively reviewed the medical records of 16 patients receiving VA-ECMO and NM from January 2017 to June 2020 at Haeundae Paik Hospital. We compared clinical and laboratory data, including activated partial thromboplastin time (aPTT), which was measured simultaneously in patients and the ECMO site, to estimate the efficacy of regional anticoagulation.

Results

The median patient age was 68.5 years, and 56.3% of patients were men. Cardiovascular disease was the most common primary disease (75.0%) requiring ECMO treatment, followed by respiratory disease (12.5%). The median duration of ECMO treatment was 7.5 days. Among 16 patients, seven were switched to NM after first using heparin as an anticoagulation agent, and nine received only NM. When comparing aPTT values in the NM group between patients and the ECMO site, that in patients was significantly lower than that at the ECMO site (73.57 vs. 79.25 seconds; P=0.010); in contrast, no difference was observed in the heparin group.

Conclusions

NM showed efficacy as a regional anticoagulation method by sustaining a lower aPTT value compared to that measured at the ECMO site. NM should be considered as a safer regional anticoagulation method in VA-ECMO for patients at high risk of bleeding.

Outcomes of Extubated COVID and Non-COVID Patients Receiving Awake Venovenous Extracorporeal Membrane Oxygenation

Cessation of continuous analgesia and sedation in patients with acute respiratory distress syndrome (ARDS) receiving venovenous (VV) extracorporeal membrane oxygenation (ECMO) facilitates early extubation, family, patient and provider engagement, and mobility. Outcomes associated with an awake ECMO strategy have not been well described in the literature. The purpose of this study was to evaluate outcomes in patients receiving this strategy. This was a retrospective review of ARDS patients receiving awake VV ECMO. The primary outcome was survival to hospital discharge. Secondary outcomes included days requiring ECMO, time from cannulation to extubation, complications, patients requiring tracheostomy, hospital and intensive care unit (ICU) length of stay (LOS), and discharge disposition. In a subgroup analysis, outcomes were compared between non-COVID and COVID ECMO patients. Sixty-two patients were included with a survival to hospital discharge of 85.5%. Days requiring ECMO was 33.0 (0.0-75.0) and cannulation to extubation was 6.0 (4.0-11.0). Three patients received a tracheostomy (4.8%). Bleeding and infection were reported in 80.6% and 82.3% of patients, respectively. Intensive care unit length of stay was 46.0 days (29.0-90.0) and hospital LOS was 51.0 days (32.0-91.0). Over half of the patients (51.6%) were discharged to an acute rehabilitation facility and 27.4% were discharged home. There was similar survival to hospital discharge between the COVID and non-COVID awake ECMO patients (85% in both groups, p = 1.000). This study highlights the impact of an awake ECMO approach on survival to hospital discharge. Future studies are needed to evaluate this approach as compared to current practice to determine if this should become the standard.

Assessing Clinical Feasibility and Safety of Percutaneous Dilatational Tracheostomy During Extracorporeal Membrane Oxygenation Support in the Intensive Care Unit

Purpose: A tracheostomy is often used to wean patients off the ventilator, as it helps maintain extracorporeal membrane oxygenation (ECMO) without sedation. A percutaneous dilatational tracheostomy (PDT) performed in critically ill patients is widely accepted, however, its feasibility and safety in ECMO is unclear.Methods: This retrospective observational study included 78 patients who underwent a PDT and ECMO at the surgical intensive care unit (SICU) in a tertiary hospital between January 1, 2016 and December 31, 2019. We analyzed their medical records, including PDT-related complications and clinical variables.Results: The median values of hemoglobin, platelet count, international normalized ratio, partial thromboplastin time, and activated partial thromboplastin time before the tracheostomy were 9.2 (8.5-10.2) g/dL, 81 (56-103) × 103/dL, 1.22 (1.13-1.30), 15.2 (14.3-16.1) seconds, and 55.1 (47.4-61.1) seconds, respectively. No clotting was observed within the extracorporeal circuit, however, minimal bleeding was observed at the tracheostomy site in 10 (12.8%) patients. Of 4 patients with major bleeding, local hemorrhage was controlled in 3 patients, and intratracheal bleeding continued in 1 patient. The mortality rate was 60.9% and 57.1% in the complication and no-complication group, respectively. The durations of SICU stay, hospital stay, and mechanical ventilation were not statistically different between the groups.Conclusion: A PDT performed in critically ill patients was associated with a low rate of bleeding. Complications did not appear to significantly affect the patient outcome. PDT can be performed in patients who usually require a tracheostomy to maintain ECMO.

Reduction in blood product transfusion requirements with early on-ECMO repair of congenital diaphragmatic hernia

Background

For infants with severe congenital diaphragmatic hernia (CDH) stabilized with extracorporeal membrane oxygenation (ECMO), early repair on ECMO improves outcome; however when compared to operative repair after ECMO, repair on ECMO is associated with increase bleeding risk and need for blood product transfusions.

Methods

A retrospective review of 54 patients with CDH placed on ECMO prior to CDH repair was performed. For the subset of patients repaired on ECMO, analysis comparing those repaired early (within 48 h of cannulation) and late (beyond 48 h) on ECMO was performed. Outcomes of interest included survival to discharge, days on ECMO, and postoperative blood product utilization.

Results

When compared to those patients repaired prior to 48 h of ECMO initiation, 57.7% of patients survived versus 40.9% of late repair patients. For those repaired early, blood product utilization was significantly less. Early repair patients received a median of 72 mL/kg packed red blood cells (PRBC) and 75 mL/kg platelets compared to 151.9 mL/kg and 98.7 mL/kg, respectively (p < 0.05 respectively). There was no difference in median days on ECMO (p = 0.38).

Conclusion

Our data supports prior reports of improved outcome with repair with 48 h of ECMO initiation and suggests early repair on ECMO is associated with less bleeding and decreased blood product requirement in the postoperative period.

Intraoperative Management of Adult Patients on Extracorporeal Membrane Oxygenation: An Expert Consensus Statement From the Society of Cardiovascular Anesthesiologists-Part I, Technical Aspects of Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is used to support patients with refractory cardiopulmonary failure. Given ECMO's increased use in adults and the fact that many ECMO patients are cared for by anesthesiologists, the Society of Cardiovascular Anesthesiologists ECMO working group created an expert consensus statement that is intended to help anesthesiologists manage adult ECMO patients who are cared for in the operating room. In the first part of this 2-part series, technical aspects of ECMO are discussed, and related expert consensus statements are provided.

Intraoperative Management of Adult Patients on Extracorporeal Membrane Oxygenation: an Expert Consensus Statement From the Society of Cardiovascular Anesthesiologists-Part I, Technical Aspects of Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is used to support patients with refractory cardiopulmonary failure. Given ECMO's increased use in adults and the fact that many ECMO patients are cared for by anesthesiologists, the Society of Cardiovascular Anesthesiologists ECMO working group created an expert consensus statement that is intended to help anesthesiologists manage adult ECMO patients who are cared for in the operating room. In the first part of this 2-part series, technical aspects of ECMO are discussed, and related expert consensus statements are provided.

Context-Responsive Anticoagulation Reduces Complications in Pediatric Extracorporeal Membrane Oxygenation

Purpose: We sought to determine the impact of a comprehensive, context-responsive anticoagulation and transfusion guideline on bleeding and thrombotic complication rates and blood product utilization during extracorporeal membrane oxygenation (ECMO).

Design: Single-center, observational pre- and post-implementation cohort study.

Setting: Academic pediatric hospital.

Patients: Patients in the PICU, CICU, and NICU receiving ECMO support.

Interventions: Program-wide implementation of a context-responsive anticoagulation and transfusion guideline.

Measurements: Pre-implementation subjects consisted of all patients receiving ECMO between January 1 and December 31, 2012, and underwent retrospective chart review. Post-implementation subjects consisted of all ECMO patients between September 1, 2013, and December 31, 2014, and underwent prospective data collection. Data collection included standard demographic and admission data, ECMO technical specifications, non-ECMO therapies, coagulation parameters, and blood product administration. A novel grading scale was used to define hemorrhagic complications (major, intermediate, and minor) and major thromboembolic complications.

Main Results: Seventy-six ECMO patients were identified: 31 during the pre-implementation period and 45 in the post-implementation period. The overall observed mortality was 33% with no difference between groups. Compared to pre-implementation, the post-implementation group experienced fewer major hemorrhagic and major thrombotic complications and less severe hemorrhagic complications and received less RBC transfusion volume per kg.

Conclusions: Use of a context-responsive anticoagulation and transfusion guideline was associated with a reduction in hemorrhagic and thrombotic complications and reduced RBC transfusion requirements. Further evaluation of guideline content, compliance, performance, and sustainability is needed.

Tracheostomy Is Safe During Extracorporeal Membrane Oxygenation Support

Patients receiving extracorporeal membrane oxygenation (ECMO) often require prolonged mechanical ventilation. Providers may be reluctant to perform tracheostomies on patients during ECMO due to their tenuous clinical status and systemic anticoagulation. We report our experience with performing open and percutaneous tracheostomies on patients supported on ECMO from August 2009 to December 2017. Of the 127 patients who underwent tracheostomy during ECMO support, the median age was 42 years (interquartile range [IQR], 29-54), 99 (78%) patients had venovenous (VV) cannulation, 22 (17%) patients had venoarterial (VA) cannulation, and six (5%) patients had hybrid configurations. Percutaneous tracheostomy was performed in 110 (87%) patients. Median-activated partial thromboplastin time (aPTT) at the time of tracheostomy was 47.5 seconds (IQR, 41-57.6 seconds). The median time from ECMO initiation to tracheostomy was 7 days (IQR, 4-11 days). A total of 55 patients (43%) received packed red blood cell (pRBC) transfusions within 48 hours after tracheostomy with a median transfusion of 2 units (IQR, 1-3). There was no procedural mortality. Overall, 88 (69%) patients survived to decannulation and 74 (58%) survived to hospital discharge. Our experience with the largest published series of tracheostomies during ECMO demonstrates that excellent outcomes can be achieved without significant morbidity.

Venoarterial extra corporeal membrane oxygenation and blood component usage in pediatric patients undergoing cardiac surgery: Single centre experience

Background

Extra Corporeal Membrane Oxygenation (ECMO) is a well-known tool for providing life-saving support in patients developing post cardiotomy cardiogenic shock in post cardiac surgeries. The current study was designed to evaluate blood transfusion requirements and its relation to mortality in neonate and pediatric cardiac patients requiring venoarterial cardiac ECMO during post-operative period following cardiac surgery.

Materials and Methods

Overall 24 pediatric patients (including neonates) who underwent VA ECMO in post cardiac surgery at our institute from January 2016 to October 2017 were included in the study. The details of demographics, blood transfusion, ECMO, and morbidity and mortality were collected for all the patients.

Objective of the Study

The primary objective of our study was to assess the outcome of patients on ECMO in post pediatric cardiac surgery. The secondary objective of the study was to assess the effect of blood transfusion on the outcome of the patients.

Results

Overall mortality rate was 50% (n = 12). The overall transfusion rate of packed red blood cells was higher in patients who did not survive even after institution of VA ECMO. The transfusion of other blood products like platelets, cryoprecipitate, and fresh frozen plasma were also higher in this group of patients though it was statistically non-significant except for packed red cell transfusion. Though statistically non-significant, the patients who didn't survive even after institution of VA ECMO post-surgery had relatively higher mean age (703.88 ± 998.94 days) as compared to their counterparts (510.63 ± 384.36 days).

Conclusion

The use of ECMO is associated with considerable morbidity and mortality. Packed red cell transfusion is definitely higher in expired patients, indicative of deteriorated status of the patient. However, considering non-significant association of other blood components, except packed red cell it is recommended that patients' overall clinical condition should be taken into consideration for transfusion of blood products and not only targeting the transfusion triggers.

Oropharyngeal hemorrhage in patients with COVID-19: A multi-institutional case series

Background

Patients with COVID-19 who are intubated and require mechanical ventilation have been observed to have oropharyngeal bleeding necessitating otolaryngology intervention.

Methods

We report five cases of oropharyngeal hemorrhage in COVID-19 patients on mechanical ventilation requiring evaluation by otolaryngologists at George Washington University Hospital (GWUH) and Boston Medical Center (BMC) from March to April 2020. Institutional Review Board at both institutions exempted this study from informed consent because there were no identifiable patient characteristics, photographs, or imaging studies included.

Results

All five patients were managed conservatively; four required packing with Kerlix gauze by an otolaryngologist. Two patients had the additional requirement of extracorporeal membrane oxygenation (ECMO) and associated anticoagulation. Three patients improved with oropharyngeal packing; two had persistent bleeding. Three patients expired. Endotracheal tubes were repositioned less frequently due to the COVID-19 pandemic.

Conclusions

Intubated patients with COVID-19 may have an increased risk of oropharyngeal hemorrhage. This may be due to anticoagulation, prolonged intubation, or decreased frequency of endotracheal tube repositioning. Otolaryngologists should wear appropriate PPE when managing this hemorrhagic complication.

Successful resuscitation by using extracorporeal membrane oxygenation in a patient with amniotic fluid embolism: a case report

Amniotic fluid embolism (AFE) is a rare disease, but it is a potentially fatal condition, as well as a leading cause of unpredictable maternal death in developed countries. The typical clinical symptoms of AFE include hypoxia, hypotension, and coagulopathy, and with rapid progression, it may cause cardiac arrest and death. We report a case of sudden hemodynamic instability due to amniotic fluid embolism, which was successfully treated with veno-arterial extracorporeal membrane oxygenation (ECMO). A 39-year-old woman was scheduled for delivery at 38 weeks and 2 days of gestation. During labor, sudden generalized tonic-clonic seizures developed, followed by dyspnea and cyanosis. Despite immediate cesarean section being performed, she became hypoxemic and experienced cardiovascular collapse. ECMO was promptly applied, and the patient became stable 8 days after cesarean section. ECMO appears to be an appropriate treatment option for catastrophic amniotic fluid embolism.

Impact of high mechanical shear stress and oxygenator membrane surface on blood damage relevant to thrombosis and bleeding in a pediatric ECMO circuit

The roles of the large membrane surface of the oxygenator and the high mechanical shear stress (HMSS) of the pump in the extracorporeal membrane oxygenation (ECMO) circuit were examined under a pediatric support setting. A clinical centrifugal pump and a pediatric oxygenator were used to construct the ECMO circuit. An identical circuit without the oxygenator was constructed for comparison. Fresh human blood was circulated in the two circuits for 4 hours under the identical pump speed and flow. Blood samples were collected hourly for blood damage assessment, including platelet activation, generation of platelet-derived microparticles (PDMP), losses of key platelet hemostasis receptors (glycoprotein (GP) Ibα (GPIbα) and GPVI), and high molecular weight multimers (HMWM) of von Willebrand factor (VWF) and plasma free hemoglobin (PFH). Platelet adhesion on fibrinogen, VWF, and collagen was further examined. The levels of platelet activation and generation of PDMP and PFH exhibited an increasing trend with circulation time while the expression levels of GPIbα and GPVI receptors on the platelet surface decreased. Correspondingly, the platelets in the blood samples exhibited increased adhesion capacity to fibrinogen and decreased adhesion capacities on VWF and collagen with circulation time. Loss of HMWM of VWF occurred in both circuits. No statistically significant differences were found in all the measured parameters for blood damage and platelet adhesion function between the two circuits. The results indicate that HMSS from the pump played a dominant role in blood damage associated with ECMO and the impact of the large surface of the oxygenator on blood damage was insignificant.

Mortality and Factors Associated With Hemorrhage During Pediatric Extracorporeal Membrane Oxygenation

OBJECTIVES

To quantify and identify factors associated with bleeding events during pediatric extracorporeal membrane oxygenation.

DESIGN

Retrospective cohort study with primary outcome of bleeding days on extracorporeal membrane oxygenation.

SETTING

Single tertiary care children's hospital.

SUBJECTS

One-hundred twenty-two children supported with extracorporeal membrane oxygenation for greater than 12 hours during January 2015 through December 2016.

INTERVENTIONS

Bleeding days were identified if mediastinal or cannula site exploration, activated factor VII administration, gastrointestinal, pulmonary, or intracranial hemorrhages occurred. Logistic regression was used to assess factors associated with bleeding days.

MEASUREMENTS AND MAIN RESULTS

Study population was identified from institutional extracorporeal membrane oxygenation database. Clinical, laboratory, and survival data were obtained from medical records. Only data from patients' first extracorporeal membrane oxygenation run were used. One-hundred twenty-two patients with median age of 17 weeks (interquartile range, 1-148 wk) were analyzed. Congenital heart disease (n = 56, 46%) was the most common diagnosis. Bleeding days comprised 179 (16%) of the 1,121 observed extracorporeal membrane oxygenation-patient-days. By extracorporeal membrane oxygenation day 4, 50% of users had experienced a bleeding day. Central rather than peripheral cannulation (odds ratio, 2.58; 95% CI, 1.47-4.52; p < 0.001), older age (odds ratio, 1.31 per increased week; 95% CI, 1.14-1.52; p < 0.001), higher lactate (odds ratio, 1.08 per 1 mmol/L increase; 95% CI, 1.05-1.12; p < 0.001), and lower platelets (odds ratio, 0.87 per 25,000 cell/μL increase; 95% CI, 0.77-0.99; p = 0.005) were associated with bleeding days. Patients who experienced more frequent bleeding (> 75th percentile) had fewer ventilator-free and hospital-free days in the 60 days after cannulation (0 vs 31; p = 0.002 and 0 vs 0; p = 0.008) and higher in-hospital mortality (68 vs 34%; p < 0.001).

CONCLUSIONS

Central cannulation, older age, low platelets, and high lactate are associated with bleeding days during pediatric extracorporeal membrane oxygenation. Patients who bleed more frequently during extracorporeal membrane oxygenation have higher in-hospital mortality, longer technological dependence, and reduced hospital-free days.

Contemporary Comprehensive Monitoring of Veno-arterial Extracorporeal Membrane Oxygenation Patients

The use of veno-arterial extracorporeal membrane oxygenation (VA ECMO) has increased substantially over the past few decades. Today's clinicians now have a powerful means with which to salvage a growing population of patients at risk for cardiopulmonary collapse. At the same time, patients supported with VA ECMO have become increasingly more complex. The successful use of VA ECMO depends not only on selecting the appropriate patients, but also on effectively navigating a potential torrent of device- and patient-related complications until ECMO is no longer needed. A multitude of monitoring tools are now available to help the treatment team determine the adequacy of care, to detect problems, and to anticipate recovery. Monitoring with devices such as the Swan-Ganz catheter, transthoracic and transesophageal echocardiography, chest radiography, and near-infrared spectroscopy can provide useful information to complement routine clinical care. Leveraging data derived from the ECMO circuit itself also can be instrumental in both evaluating the sufficiency of support and troubleshooting complications. Each of these tools, however, has its own unique sets of limitations and liabilities. A thorough understanding of these risks and benefits is critical to the contemporary care of the individual managed with VA ECMO. In addition, more research is needed to establish optimal evidence-based care pathways and best-practice principles for using these devices to improve patient outcomes.

Antithrombin supplementation during extracorporeal membrane oxygenation: study protocol for a pilot randomized clinical trial

BACKGROUND

Normal levels of plasma antithrombin (AT) activity might decrease heparin requirements to achieve an adequate level of anticoagulation during treatment with extracorporeal membrane oxygenation (ECMO). Acquired AT deficiency during ECMO is common, but formal recommendations on target, timing, and rate of AT supplementation are lacking. Thus, we conceived a pilot trial to evaluate the feasibility and safety of prolonged AT supplementation in patients requiring veno-venous ECMO for respiratory failure.

METHODS

Grifols Antithrombin Research Awards (GATRA) is a prospective, randomized, single blinded, multicenter, controlled two-arm trial. Patients undergoing veno-venous ECMO will be randomized to either receive AT supplementation to maintain a functional AT level between 80 and 120% (AT supplementation group) or not (control group) for the entire ECMO course. In both study groups, anticoagulation will be provided with unfractionated heparin following a standardized protocol. The primary endpoint will be the dose of heparin required to maintain the ratio of activated partial thromboplastin time between 1.5 and 2. Secondary endpoints will be the adequacy of anticoagulation and the incidence of hemorrhagic and thrombotic complications.

DISCUSSION

GATRA is a pilot trial that will test the efficacy of a protocol of AT supplementation in decreasing the heparin dose and improving anticoagulation adequacy during ECMO. If positive, it might provide the basis for a future larger trial aimed at verifying the impact of AT supplementation on a composite outcome endpoint including hemorrhagic events, transfusion requirements, and mortality.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03208270 . Registered on 5 July 2017.

In Vitro Study on the Dynamics of Blood Flow Impelled by an Alternating Current Magnetohydrodynamic Blood Pump

Artificial hearts are effective devices to treat heart failure in clinical practice and can be divided into two categories: artificial hearts and ventricular assist devices. The goal of this work was to investigate the fluidity and biological changes of in vitro sheep blood using a novel alternating current (AC) magnetohydrodynamic blood pump (central magnetic intensity: 0.9 T, alternating current frequency of the electric motor: 0-80 Hz). Blood samples were collected from five sheep and were divided into two groups: the control group (no exposure to an external magnetic field) and the exposed group (3 h of exposure to an alternating magnetic field). The blood cell counts, changes in blood viscosity, and ultrastructural changes of the blood cells under transmission electron microscopy were investigated. This study demonstrated several findings: (i) Continuous sheep blood flow can be achieved; (ii) The blood cell counts remained unchanged after 3 h of exposure to an alternating magnetic field; (iii) Compared with the control group, the high- and low-shear viscosities of the whole blood from the sheep significantly decreased after 3 h of exposure to an alternating magnetic field (P < 0.05 and P < 0.01, respectively). Plasma viscosity was significantly reduced after exposure to high-intensity alternating magnetic fields (P < 0.001); (iv) The cytoplasm of blood cells (especially erythrocytes) became lighter in color in the exposure group compared to the control group, and "beads-on-string" aggregations of black particles appeared. This work provides detailed and reliable scientific research data for the development of this type of blood pump, which may serve as a transition to the clinical artificial heart.

A Successful Whole Body Therapeutic Hypothermia for Hypoxic Ischemic Encephalopathy During an ECMO Run in a Newborn

Data regarding the safety of using therapeutic hypothermia (TH) with extracorporeal membrane oxygenation (ECMO) in neonates with both hypoxic ischemic encephalopathy (HIE), and respiratory failure are lacking. TH is not associated with an increased incidence of hemostatic complications, but hypothermia may impair coagulation. Herein, we report a case of a newborn who had meconium aspiration syndrome and HIE and underwent both TH and ECMO. He did not have any bleeding or circuit complications, and mortality as short-term outcome along with well-neurodevelopmental outcome.

Prolonged use of eptifibatide as a bridge to maintain drug-eluting stent patency in a patient receiving extracorporeal membrane oxygenation

BACKGROUND

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) has been used as a bridge to cardiac recovery in patients following a major cardiac event. There is a lack of literature surrounding prolonged use of eptifibatide and optimal dosing during ECMO. This case report describes our experience with extended durations and standard dosing of eptifibatide in the setting of ECMO.

CASE

A 40-year-old male with a history of Marfan's syndrome, aortic root and ascending aortic aneurysm status post a modified Bentall with a St. Jude mechanical aortic valve conduit and hemi-Cabrol with a Dacron graft to the left main coronary artery presented with exertional chest pain and was found to have an anastomotic narrowing to the left main which occluded while awaiting surgical revision. A rescue percutaneous coronary intervention at the anastomotic site was performed. Due to hemodynamic instability, he was placed on femoral VA-ECMO. The patient was started on anticoagulation for the ECMO circuit and eptifibatide to maintain stent patency. The patient experienced several bleeding episodes for which he received supportive care, endoscopic intervention and left gastric artery embolization. Eptifibatide was maintained at standard dosing and the heparin infusion was withheld. A coronary angiogram revealed no thrombus within the Cabrol graft a patent stent previously placed at the site of the distal graft-coronary anastomosis. The patient was decannulated from ECMO and underwent coronary artery bypass grafting and division of the hemi-Cabrol graft.

CONCLUSION

While eptifibatide was effective in maintaining stent patency, our patient experienced several bleeding episodes during ECMO. Thus, the risks and benefits of concurrent antiplatelet and anticoagulant therapy must be appropriately weighed in this patient population. Additionally, as the need for dual antiplatelet therapy due to coronary stent implantation is increasing, further studies are needed to validate optimal dosing of eptifibatide in patients at a high risk of bleeding during ECMO.

Medication Complications in Extracorporeal Membrane Oxygenation

The need for extracorporeal membrane oxygenation (ECMO) therapy is a marker of disease severity for which multiple medications are required. The therapy causes physiologic changes that impact drug pharmacokinetics. These changes can lead to exposure-driven decreases in efficacy or increased incidence of side effects. The pharmacokinetic changes are drug specific and largely undefined for most drugs. We review available drug dosing data and provide guidance for use in the ECMO patient population.

Thromboprophylaxis in Extracorporeal Circuits: Current Pharmacological Strategies and Future Directions

The development of extracorporeal devices for organ support has been a part of medical history and progression since the late 1900s. These types of technology are primarily used and developed in the field of critical care medicine. Unfractionated heparin, discovered in 1916, has really been the only consistent form of thromboprophylaxis for attenuating or even preventing the blood-biomaterial reaction that occurs when such technologies are initiated. The advent of regional anticoagulation for procedures such as continuous renal replacement therapy and plasmapheresis have certainly removed the risks of systemic heparinization and heparin effect, but the challenges of the blood-biomaterial reaction and downstream effects remain. In addition, regional anticoagulation cannot realistically be applied in a system such as extracorporeal membrane oxygenation because of the high blood flow rates needed to support the patient. More recently, advances in the technology itself have resulted in smaller, more compact extracorporeal life support (ECLS) systems that can-at certain times and in certain patients-run without any form of anticoagulation. However, the majority of patients on ECLS systems require some type of systemic anticoagulation; therefore, the risks of bleeding and thrombosis persist, the most devastating of which is intracranial hemorrhage. We provide a concise overview of the primary and alternate agents and monitoring used for thromboprophylaxis during use of ECLS. In addition, we explore the potential for further biomaterial and technologic developments and what they could provide when applied in the clinical arena.

Bleeding Complications Associated With Percutaneous Tracheostomy Insertion in Patients Supported With Venovenous Extracorporeal Membrane Oxygen Support: A 10-Year Institutional Experience

OBJECTIVES

To evaluate the bleeding complications associated with percutaneous tracheostomy while a patient is receiving venovenous extracorporeal membrane oxygen (VV ECMO) support.

DESIGN

Retrospective, observational analysis.

SETTING

Single-center, tertiary, academic institution.

PARTICIPANTS

All consecutive patients on VV ECMO over a 10 year-period undergoing percutaneous tracheostomy.

INTERVENTIONS

Percutaneous tracheostomy.

MEASUREMENTS AND MAIN RESULTS

Fifty percutaneous tracheostomies were performed in patients requiring VV ECMO support over the 10-year period. The authors observed a 40% incidence of bleeding, with 32% of these incidences characterized as minor (self-limiting, localized stomal ooze) and 8% characterized as significant (necessitating surgical control and frequent packing or accompanied by a decrease in hemoglobin >20%).

CONCLUSIONS

Bleeding is associated with percutaneous tracheostomy and is self-limiting in the majority of patients.

Anticoagulation Therapy during Extracorporeal Membrane Oxygenator Support in Pediatric Patients

Extracorporeal membrane oxygenation (ECMO) is a salvage therapy for critically ill patients. Although ECMO is becoming more common, hemorrhagic and thromboembolic complications remain the major causes of death in patients undergoing ECMO treatments. These complications commence upon blood contact with artificial surfaces of the circuit, blood pump, and oxygenator system. Therefore, anticoagulation therapy is required in most cases to prevent these problems. Anticoagulation is more complicated in pediatric patients than in adults, and the foreign surface of ECMO only increases the complexity of systemic anticoagulation. In this review, we discuss the pathophysiology of coagulation, anticoagulants, and monitoring tools in pediatric patients receiving ECMO.

Current Limitations of the Assessment of Haemostasis in Adult Extracorporeal Membrane Oxygenation Patients and the Role of Point-of-Care Testing

Haemostatic perturbations are commonly seen in extracorporeal membrane oxygenation (ECMO) patients and remain a clinical challenge, contributing significantly to morbidity and mortality. The approach to anticoagulation monitoring and the management of bleeding varies considerably across ECMO centres. Routine laboratory tests have their limitations in terms of turnaround time and specificity of information provided. Newer point-of-care testing (POCT) for coagulation may overcome these issues, as it provides information about the entire coagulation pathway from clot initiation to lysis. It is also possible to obtain qualitative information on platelet function from these tests. Furthermore, the ability to incorporate these results into a goal-directed algorithm to manage bleeding with targeted transfusion strategies appears particularly attractive and cost effective. Further studies are required to evaluate the utility of POCT to optimise bleeding and anticoagulation management in these complex patients.

Ovine platelet function is unaffected by extracorporeal membrane oxygenation within the first 24 h

This study investigated platelet dysfunction during short-term extracorporeal membrane oxygenation (ECMO) and secondarily to determine if hyperoxaemia contributes to this dysfunction. Healthy sheep were anaesthetized and maintained on ECMO for either 2 or 24 h, with or without induction of smoke inhalation acute lung injury. A specialized animal-operating theatre was used to conduct the experimentation. Forty-three healthy female sheep were randomized into either a test or a control group. Following anaesthesia, test groups received ECMO ± smoke inhalation acute lung injury (SALI), whereas control groups were maintained with ventilation only ± SALI. Physiological, biochemical and coagulation data were obtained throughout via continuous monitoring and blood sampling. Platelet function was quantified through whole blood impedance aggregometry using Multiplate. Ovine platelet activity induced by adenosine diphosphate (ADP) and collagen was unaffected during the first 24 h of ECMO. However, progressive divergence of ADP-induced platelet activity was noted at cessation of the experiment. PaO2 was inversely related to ADP-dependent platelet activity in the ECMO groups--a relationship not identified in the control groups. ADP and collagen-dependent platelet activity are not significantly affected within the first 24 h of ECMO in sheep. However, dysfunction in ADP-dependent platelet activity may have continued to develop if observed beyond 24 h. Hyperoxaemia during ECMO does appear to affect how platelets react to ADP and may contribute to this developing dysfunction. Long-term animal models and investigation in clinical animals are warranted to fully investigate platelet function during ECMO.

The Complex Relationship of Extracorporeal Membrane Oxygenation and Acute Kidney Injury: Causation or Association?

Extracorporeal membrane oxygenation (ECMO) is a modified cardiopulmonary bypass (CPB) circuit capable of providing prolonged cardiorespiratory support. Recent advancement in ECMO technology has resulted in increased utilisation and clinical application. It can be used as a bridge-to-recovery, bridge-to-bridge, bridge-to-transplant, or bridge-to-decision. ECMO can restitute physiology in critically ill patients, which may minimise the risk of progressive multiorgan dysfunction. Alternatively, iatrogenic complications of ECMO clearly contribute to worse outcomes. These factors affect the risk : benefit ratio of ECMO which ultimately influence commencement/timing of ECMO. The complex interplay of pre-ECMO, ECMO, and post-ECMO pathophysiological processes are responsible for the substantial increased incidence of ECMO-associated acute kidney injury (EAKI). The development of EAKI significantly contributes to morbidity and mortality; however, there is a lack of evidence defining a potential benefit or causative link between ECMO and AKI. This area warrants investigation as further research will delineate the mechanisms involved and subsequent strategies to minimise the risk of EAKI. This review summarizes the current literature of ECMO and AKI, considers the possible benefits and risks of ECMO on renal function, outlines the related pathophysiology, highlights relevant investigative tools, and ultimately suggests an approach for future research into this under investigated area of critical care.

Pediatric Extracorporeal Membrane Oxygenation: An Introduction for Emergency Medicine Physicians

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) therapy has supported critically ill pediatric patients in the intensive care unit setting with cardiac and respiratory failure. This therapy is beginning to transition to the emergency department setting.

OBJECTIVE OF REVIEW

This article describes the fundamentals of ECMO and familiarizes the emergency medicine physician with its use in critically ill pediatric patients.

DISCUSSION

ECMO can be utilized as either venoarterial (VA) or venovenous (VV), to support oxygenation and perfusion in respiratory failure, sepsis, cardiac arrest, and environmental hypothermia.

Comparison of Coagulation Parameters, Anticoagulation, and Need for Transfusion in Patients on Interventional Lung Assist or Veno-Venous Extracorporeal Membrane Oxygenation

Clinical data on anticoagulation needs of modern extracorporeal membrane oxygenation (ECMO) and its impact on coagulation are scarce. Therefore, we analyzed coagulation-related parameters, need for transfusion, and management of anticoagulation in adult patients with severe acute respiratory failure during treatment with either pumpless interventional lung assist (iLA) or veno-venous ECMO (vv-ECMO). Sixty-three patients treated with iLA and 192 patients treated with vv-ECMO at Regensburg University Hospital between January 2005 and May 2011 were analyzed. Data related to anticoagulation, transfusion, and coagulation parameters were collected prospectively by the Regensburg ECMO registry. Except for a higher, sequential organ failure assessment (SOFA) score in the ECMO group (12 [9-15] vs. 11 [7-14], P = 0.007), a better oxygenation, and a lower dosage of vasopressors in the iLA patients, both groups had similar baseline characteristics. No difference was noted in terms of outcome and overall transfusion requirements. Factors of the plasmatic coagulation system were only marginally altered over time and did not differ between groups. Platelet counts in ECMO-treated patients, but not in those treated with iLA, dropped significantly during extracorporeal support. A more intense systemic anticoagulation with a mean activated partial thromboplastin time (aPTT) > 53 s led to a higher need for transfusions compared with the group with a mean aPTT < 53 s, whereas the average durability of membrane oxygenators was not affected. Need for red blood cell (RBC) transfusion was highest in patients with extrapulmonary sepsis (257 mL/day), and was significantly lower in primary pulmonary adult respiratory distress syndrome (ARDS) (102 mL/day). Overall, 110 (0-274) mL RBC was transfused in the ECMO group versus 146 (41-227) mL in the iLA group per day on support. The impact of modern iLA and ECMO systems on coagulation allows comparatively safe long-term treatment of adult patients with acute respiratory failure. A moderate systemic anticoagulation seems to be sufficient. Importantly, platelets are more affected by vv-ECMO compared with pumpless iLA.

[Use of ECMO in adult patients with cardiogenic shock: a position paper of the Austrian Society of Cardiology]

The use of ECMO to stabilize critically ill patients with severely depressed cardiac function and hemodynamics increased in the last years due to broader availability, better performance and easier implantation of the devices. The present guidelines of the Austrian Society of Cardiology focus on the use of ECMO in adult non-operated patients with cardiac diseases. Not only indications and contraindications are highlighted, but also the equally important issues of monitoring, complication management, measures during implantation and operation, and weaning of the devices are treated in detail. Thereby the present guidelines aim to optimize the use of ECMO in the individual centers, and aim to help current non-ECMO centers in developing a local ECMO-program or to contact ECMO-centers for discussion of individual patients.

Hemorrhagic complications in pediatric cardiac patients on extracorporeal membrane oxygenation: an analysis of the Extracorporeal Life Support Organization Registry

OBJECTIVES

To determine the prevalence of and risk factors for hemorrhagic complications in children with cardiac disease requiring extracorporeal membrane oxygenation.

DESIGN

Retrospective review of the Extracorporeal Life Support Organization Registry (2002-2013).

SETTING

Participating Extracorporeal Life Support Organization centers.

PATIENTS

Patients less than 18 years old on extracorporeal membrane oxygenation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 21,845 patients requiring extracorporeal membrane oxygenation during the study period, 8,905 (41%) had cardiac disease, and 79% of whom (6,995) had cardiac surgery. Hemorrhagic complications occurred in 8,480 patients (39% of overall cohort), with higher rates in cardiac versus noncardiac patients (49% vs 32%; p < 0.0001) related to cannulation and surgical site bleeding. Cardiac surgical patients had higher rates of hemorrhage compared with cardiac medical patients (57% vs 38%; p < 0.0001), and cardiac patients with hemorrhage had higher extracorporeal membrane oxygenation mortality compared with those without (42% vs 22% in medical patients and 34% vs 20% in surgical patients; both p < 0.0001). In multivariable analysis in both the cardiac medical and surgical groups, hemorrhage risk was higher in children greater than 1 year old and in patients with longer extracorporeal membrane oxygenation duration. Additional independent risk factors for hemorrhage in cardiac surgical patients included pre-extracorporeal membrane oxygenation mediastinal exploration (odds ratio, 3.6; 95% CI, 2.1-6.3), Society of Thoracic Surgeons morbidity category 4-5 (odds ratio, 1.2; 95% CI, 1.03-1.5), cannulation less than 24 hours after surgery (odds ratio, 1.6; 95% CI, 1.3-1.9), and longer cardiopulmonary bypass time (≥ 282 min [upper quartile]; odds ratio, 1.5; 95% CI, 1.3-1.9).

CONCLUSIONS

In this large, multicenter analysis, hemorrhagic complications occurred in nearly half of children with heart disease on extracorporeal membrane oxygenation and were associated with a significant mortality risk. Several factors were associated with hemorrhagic complications in cardiac surgical patients including pre-extracorporeal membrane oxygenation mediastinal exploration, greater surgical complexity, early postoperative cannulation, and longer bypass times. Whether these risks can be mitigated by modifying or delaying systemic anticoagulation requires further investigation.

Extracorporeal membrane oxygenation-hemostatic complications

The use of extracorporeal membrane oxygenation (ECMO) support for cardiac and respiratory failure has increased in recent years. Improvements in ECMO oxygenator and pump technologies have aided this increase in utilization. Additionally, reports of successful outcomes in supporting patients with respiratory failure during the 2009 H1N1 pandemic and reports of ECMO during cardiopulmonary resuscitation have led to increased uptake of ECMO. Patients requiring ECMO are a heterogenous group of critically ill patients with cardiac and respiratory failure. Bleeding and thrombotic complications remain a leading cause of morbidity and mortality in patients on ECMO. In this review, we describe the mechanisms and management of hemostatic, thrombotic and hemolytic complications during ECMO support.

The Influence of Free Hemoglobin and Bilirubin on Heparin Monitoring by Activated Partial Thromboplastin Time and Anti-Xa Assay

Context

Elevated free hemoglobin (Hb) and bilirubinemia complicate extracorporeal membrane oxygenation and could affect unfractionated heparin (UH) therapy monitoring by anti-Xa assay and activated partial thromboplastin time (aPTT).

Objectives

To compare in vitro response of anti-Xa and aPTT assays to UH in samples with artificial hyperbilirubinemia and hyperhemoglobinemia and to estimate if this interference is also observed in vivo in pediatric extracorporeal membrane oxygenation.

Design

Measurement of aPTT and anti-Xa activity in plasma spiked with UH and increased concentration of free Hb and/or conjugated bilirubin. All samples with anti-Xa activity, antithrombin, free Hb, and bilirubin determination and infused dose of UH from inpatients on extracorporeal membrane oxygenation were extracted from the clinical patient database and analyzed.

Results

Each increment of free Hb by 100 mg/dL significantly shortened aPTT, whereas an increment of bilirubin by 6 mg/dL caused significant prolongation of aPTT and stepwise increase of free Hb and/or bilirubin in plasma decreased anti-Xa activity by 0.03 to 0.05 IU/mL. Extracorporeal membrane oxygenation samples with free Hb 50 mg/dL or greater had significantly lower anti-Xa activity compared with normal ones: 0.33 (0.25–0.42) versus 0.4 (0.31–0.48) IU/mL (P = .01), despite the identical UH infusion and similar antithrombin activity. Moderate increase of free Hb by 59 mg/dL was associated with absolute decrease of anti-Xa activity by 0.07 IU/mL.

Conclusions

Activated partial thromboplastin time and anti-Xa assay are affected by elevated level of free Hb and/or bilirubin in the presence of UH, and lower anti-Xa activity is noted in extracorporeal membrane oxygenation patients with elevated free Hb. Severe hemolysis and/or hyperbilirubinemia could compromise UH monitoring based on these assays.

Antithrombin III supplementation on extracorporeal membrane oxygenation: impact on heparin dose and circuit life

Antithrombin III (ATIII) is used during extracorporeal membrane oxygenation (ECMO) based on physiologic rationale and studies during cardiopulmonary bypass. In February 2008, our institution began using ATIII as replacement for low ATIII activity (<70%) in patients supported with ECMO. We hypothesized that ATIII supplementation would reduce heparin infusion rates, increase unfractionated heparin anti-Xa levels, and prolong ECMO circuit life. Data from 40 consecutive patients (45 deployments) requiring ECMO support for >72 hours with venoarterial ECMO from January 1, 2007, through December 31, 2008, were collected. Antithrombin III concentrate was administered for ATIII activity <70% at the discretion of the attending physician. The primary outcome was whether the heparin infusion rate was reduced by 10% or more as a result of ATIII administration. No difference in heparin infusion rate (p = 0.245) as a result of ATIII administration was observed. Anti-Xa levels were lower before ATIII administration (p< 0.001) and were increased after ATIII administration (p < 0.001). There was an increased frequency of circuit failure in ATIII treatment group compared with nontreatment group (p = 0.018). Neither heparin responsiveness nor circuit life was enhanced by daily ATIII supplementation for activity <70%. Future studies are warranted to evaluate the effectiveness of antithrombin replacement.