Platelet Function Disturbance During Veno-Venous ECMO in ARDS Patients Assessed by Multiple Electrode Aggregometry-A Prospective, Observational Cohort Study

Interest in the new thromboelastometry device, Clot Pro®, for predicting thrombocytopenia and hypofibrinogenemia during lung transplantation

INTRODUCTION

Lung transplantation is associated with high proportion of transfusion. Monitoring of coagulopathy using viscoelastic tests could aid in the perioperative management of bleeding. The aim of the study was to assess the predictive cut-off values for thrombocytopenia and hypofibrinogenemia using the new thromboelastography analyzer, ClotPro.

METHODS

We retrospectively enrolled 65 patients who underwent lung transplantation and were sampled for both viscoelastic assays and conventional coagulation assays simultaneously during the procedure. We characterized the correlation between the EX-test (extrinsic pathway) and platelet count as well as between the FIB-test (extrinsic pathway after platelet inhibition) and fibrinogen concentration. Then, we used ROC curve analysis to determine the optimal EX-test and FIB-test values for predicting thrombocytopenia and hypofibrinogenemia.

RESULTS

All the amplitude values of the EX-test (A5, A10, A20, MCF) showed correlation with platelets count (Spearman's rank correlation coefficient ranging from 0.75 to 0.77, all p < 0.0001). We also observed a strong correlation between the amplitude values of the FIB-test (A5, A10, A20 and MCF) and the fibrinogen concentration (Spearman's rank correlation coefficient ranging from 0.68 to 0.71, all p < 0.0001). The AUCs of the EX-test values for thrombocytopenia <100 G/L and <80 G/L ranged from 0.80 to 0.93. Similarly, the AUCs of the FIB-test values for hypofibrinogenemia <1.5 g/L and <2 g/L ranged from 0.74 to 0.83. These results indicate that only the five-minute parameter of thromboelastometry is sufficient for detecting thrombocytopenia and hypofibrinogenemia in patients undergoing lung transplantation. The proposed cut off values for the EX-test to predict thrombocytopenia <80 G/L showed high sensitivity (>86 %), high specificity (>89 %) and high negative predictive value (>95 %). FIB-test cut off values predictive of fibrinogen below 1.5 g/L showed sensitivity (>78 %), specificity (>55 %) and negative predictive value (>88 %).

CONCLUSIONS

Our study provided preliminary results that are useful for developing a ClotPro-based algorithm to guide transfusion in lung transplantation. Future interventional studies will be necessary to validate these cut-off values of ClotPro for guiding transfusion.

Impact of surface coating and systemic anticoagulants on hemostasis and inflammation in a human whole blood model

BACKGROUND

Surface compatibility with blood is critical both for scientific investigations on hemostasis and clinical applications. Regarding in vitro and ex vivo investigations, minimal alteration in physiological hemostasis is of particular importance to draw reliable conclusions on the human coagulation system. At the same time, artificial coagulation activation must be avoided, which is relevant for the patient, for example to prevent stent graft occlusion. The aim was to evaluate the advantages and disadvantages of antithrombotic and antifouling surface coatings in the context of their suitability for ex vivo incubation and the study of coagulation properties.

METHODS

We investigated the impact of different protocols for surface coating of synthetic material and different anticoagulants on hemostasis and platelet activation in ex vivo human whole blood. Blood samples from healthy donors were incubated in coated microtubes on a rotating wheel at 37°C. Two protocols for surface coating were analyzed for hemostatic parameters and metabolic status, a heparin-based coating (CHC, Corline Heparin Conjugate) without further anticoagulation and a passivating coating (MPC, 2-methacryloyloxethyl phosphorylcholine) with added anticoagulants (enoxaparin, ENOX; or fondaparinux, FPX). Employing the MPC-based coating, the anticoagulants enoxaparin and fondaparinux were compared regarding their differential effects on plasmatic coagulation by thrombelastometry and on platelet activation by flowcytometry and platelet function assays.

RESULTS

Using the CHC coating, significant coagulation cascade activation was observed, whereas parameters remained mostly unchanged with MPC-based protocols. Extended incubation caused significantly elevated levels of the soluble membrane attack complex. Neither ENOX nor FPX caused a relevant impairment of platelet function or activation capacity and thrombelastometric parameters remained unchanged with both protocols. For translational purposes, we additionally modeled endotoxemia with the MPC-based protocols by incubating with lipopolysaccharide plus/minus thrombin. While coagulation parameters remained unchanged, elevated Interleukin 8 and Matrix Metalloproteinase 9 demonstrated preserved immune cell responsiveness.

CONCLUSIONS

The MPC-based protocols demonstrated better hemocompatibility compared to CHC, and ENOX and FPX proved useful for additional anticoagulation. Furthermore, this simple-to-use whole blood model may be useful for experimental analyses of the early coagulatory and immunological response without decalcification.

Platelet Phenotype and Function Changes With Increasing Duration of Extracorporeal Membrane Oxygenation

OBJECTIVES

To investigate platelet pathophysiology associated with pediatric extracorporeal membrane oxygenation (ECMO).

DESIGN

Prospective observational study of neonatal and pediatric ECMO patients from September 1, 2016, to December 31, 2019.

SETTING

The PICU in a large tertiary referral pediatric ECMO center.

PATIENTS

Eighty-seven neonates and children (< 18 yr) supported by ECMO.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Arterial blood samples were collected on days 1, 2, and 5 of ECMO and were analyzed by whole blood flow cytometry. Corresponding clinical data for each patient was also recorded. A total of 87 patients were recruited (median age, 65 d; interquartile range [IQR], 7 d to 4 yr). The median duration of ECMO was 5 days (IQR, 3-8 d) with a median length of stay in PICU and hospital of 18 days (IQR, 10-29 d) and 35 days (IQR, 19-75 d), respectively. Forty-two patients (48%) had at least one major bleed according to a priori determined definitions, and 12 patients (14%) had at least one thrombotic event during ECMO. Platelet fibrinogen receptor expression decreased (median fluorescence intensity [MFI], 29,256 vs 26,544; p = 0.0005), while von Willebrand Factor expression increased (MFI: 7,620 vs 8,829; p = 0.0459) from day 2 to day 5 of ECMO. Platelet response to agonist, Thrombin Receptor Activator Peptide 6, also decreased from day 2 to day 5 of ECMO, as measured by binding with anti-P-selectin, PAC-1 (binds activated GPIIb/IIIa), and anti-CD63 monoclonal antibodies (P-selectin area under the curve [AUC]: 63.46 vs 42.82, respectively, p = 0.0022; PAC-1 AUC: 93.75 vs 74.46, p = 0.0191; CD63 AUC: 55.69 vs 41.76, p = 0.0020).

CONCLUSIONS

The loss of platelet response over time may contribute to bleeding during ECMO. These novel insights may be useful in understanding mechanisms of bleeding in pediatric ECMO and monitoring platelet markers clinically could allow for prediction or early detection of bleeding and thrombosis.

Extracorporeal membrane oxygenation seems to induce impairment of primary hemostasis pathology as measured by a Multiplate analyzer: An observational retrospective study

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) support is often associated with bleeding complications caused by secondary or primary hemostasis pathology. However, there are limited data investigating primary hemostasis using Multiplate aggregometry with specific diagnostics tests for vWF (von Willebrand factor) deficiency.

AIMS

The aim of this study was to find out whether short-term ECMO produces the pathology of primary hemostasis that is detected by Multiplate aggregometry and to investigate the pathology of vWF.

METHODS

In this study, blood samples of 20 patients undergoing lung transplantations with short-term perioperative ECMO support were analyzed. The multimeric structure, the levels of von Willebrand factor antigen (vWF), ristocetin cofactor (RCo), collagen-binding protein (CB), and the results of multiple electrode aggregometry RISTO (ristocetin), ADP (adenosine diphosphate), ASPI (Aspirin®; arachidonic acid), and TRAP (thrombin receptor activating peptide) tests were compared to the samples obtained before and after ECMO support.

RESULTS

The Multiplate ADP and RISTO tests showed the presence of significant pathology in primary hemostasis after surgery (p < 0.05), suggesting the presence of acquired platelet dysfunction. Although the RISTO tests suggest the presence of acquired vWF deficiency, laboratory tests for vWF antigen and RCo and CB tests showed an increase in this case. The multimeric structure of vWF did not show clinically significant deterioration.

CONCLUSIONS

Multiple aggregometry ADP, ASPI, and TRAP tests seem to be able to detect primary hemostasis pathology (platelets aggregation and adhesion pathology) that is present during short-term perioperative ECMO support in lung transplantation procedures. Interestingly, RISTO tests seem to be more suitable for the diagnosis of platelet dysfunction than the diagnosis of acquired vWF deficiency in this situation.

Contraindications to the Initiation of Veno-Venous ECMO for Severe Acute Respiratory Failure in Adults: A Systematic Review and Practical Approach Based on the Current Literature

(1) Background: Extracorporeal membrane oxygenation (ECMO) is increasingly used for acute respiratory failure with few absolute but many relative contraindications. The provider in charge often has a difficult time weighing indications and contraindications to anticipate if the patient will benefit from this treatment, a decision that often decides life and death for the patient. To assist in this process in coming to a good evidence-based decision, we reviewed the available literature. (2) Methods: We performed a systematic review through a literature search of the MEDLINE database of former and current absolute and relative contraindications to the initiation of ECMO treatment. (3) Results: The following relative and absolute contraindications were identified in the literature: absolute-refusal of the use of extracorporeal techniques by the patient, advanced stage of cancer, fatal intracerebral hemorrhage/cerebral herniation/intractable intracranial hypertension, irreversible destruction of the lung parenchyma without the possibility of transplantation, and contraindications to lung transplantation; relative-advanced age, immunosuppressed patients/pharmacological immunosuppression, injurious ventilator settings > 7 days, right-heart failure, hematologic malignancies, especially bone marrow transplantation and graft-versus-host disease, SAPS II score ≥ 60 points, SOFA score > 12 points, PRESERVE score ≥ 5 points, RESP score ≤ -2 points, PRESET score ≥ 6 points, and "do not attempt resuscitation" order (DN(A)R status). (4) Conclusions: We provide a simple-to-follow algorithm that incorporates absolute and relative contraindications to the initiation of ECMO treatment. This algorithm attempts to weigh pros and cons regarding the benefit for an individual patient and hopefully assists caregivers to make better, informed decisions.

Systematic review and meta-analysis of the clinical effectiveness of point-of-care testing for anticoagulation management during ECMO

STUDY OBJECTIVE

Viscoelastic point-of-care (POC) tests are commonly used to provide prompt diagnosis of coagulopathy and allow targeted treatments in bleeding patients on ECMO. We evaluated the clinical effectiveness of point-of-care (POC) testing for anticoagulation management in patients on extracorporeal membrane oxygenation (ECMO).

DESIGN

Systematic review and meta-analysis. Eligible studies evaluating the use of thromboelastography- or thromboelastometry-guided algorithms, anti-factor Xa and platelet function testing were selected after screening the literature from July 1975 to January 2020.

SETTING

Patients on ECMO support.

PATIENTS

Anticoagulation management on ECMO patients.

INTERVENTIONS

Rotational thromboelastometry, thromboelastography, alone or combined with platelet function testing. Trials monitoring the anticoagulation effects during ECMO using an anti-factor Xa assay were included in the systematic review.

MEASUREMENTS

The primary outcomes were bleeding events, surgical revisions, thrombosis events and ECMO circuit change/failure. Secondary outcomes were blood-product transfusions, cerebrovascular accidents, mortality on ECMO, ECMO duration, intensive care unit and hospital discharge rates, and in-hospital mortality.

MAIN RESULTS

Thirty-one trials enrolling 1684 participants were included in the systematic review. Four trials enrolling 547 subjects were included in the meta-analysis. The use of a POC testing device resulted in improved detection of surgical bleeding (RR: 0.68, 95% CI 0.49 to 0.94, I² = 0%; χ² test for heterogeneity, P = 0.02). The use of POC-guided algorithms did not affect bleeding (RR:0.78, 95% CI 0.58 to 1.04, I² = 47%; χ² test for heterogeneity, P = 0.09), thrombosis events (RR:1.35, 95% CI 0.86 to 2.12, I² = 37%; χ² test for heterogeneity, P = 0.19), or ECMO circuit/change (RR:0.90, 95% CI 0.48 to 1.71, I² = 28%; χ² test for heterogeneity, P = 0.75).

CONCLUSION

Routine use of POC tests did not improve the main clinical outcomes beyond suggesting a diagnosis of surgical bleeding in ECMO patients.

Factor XIII Activity Might Already Be Impaired before Veno-Venous ECMO in ARDS Patients: A Prospective, Observational Single-Center Cohort Study

Direct complications in patients receiving extracorporeal (veno-venous) membrane oxygenation (vvECMO) are mainly either due to bleeding or thromboembolism. We aimed to evaluate the course of routine coagulation parameters and the activity of different coagulation factors—with special focus on factor XIII (F XIII)—before, during and after vvECMO in acute respiratory distress syndrome (ARDS) patients. The activity of coagulation factors and rotational thrombelastometry were analyzed in 20 ECMO patients before (T-1) and 6 h (T0), one (T1), three (T3) and seven days (T7) after the implantation, as well as one and three days after the termination of ECMO. F XIII activity was already severely decreased to 37% (30/49) before ECMO. F XIII activity was the only coagulation factor continuously declining during vvECMO, being significantly decreased at T3 (31% (26/45) vs. 24% (18/42), p = 0.0079) and T7 (31% (26/45) vs. 23% (17/37), p = 0.0037) compared to T0. Three days after termination of vvECMO, platelet count and fibrinogen nearly doubled and factors II, V, XI and XIII showed spontaneous significant increases. Severe ARDS patients showed a considerably diminished factor XIII activity before vvECMO initiation and its activity continuously declined later on. Thus, incorporation of F XIII monitoring into the regular hemostaseologic routine during vvECMO therapy seems advisable. Due to the potential development of a hypercoagulatory state after the termination of vvECMO, tight hemostasiologic monitoring should persist in the initial phase after ECMO termination.

Platelet Functions During Extracorporeal Membrane Oxygenation. Platelet-Leukocyte Aggregates Analyzed by Flow Cytometry as a Promising Tool to Monitor Platelet Activation

Extracorporeal membrane oxygenation (ECMO) is an extracorporeal circulation used to manage patients with severe circulatory or respiratory failure. It is associated with both high bleeding and thrombosis risks, mainly as a result of biomaterial/blood interface phenomena, high shear stress, and complex inflammatory response involving the activation of coagulation and complement systems, endothelial cells, leukocytes, and platelets. Besides their critical role in hemostasis, platelets are important players in inflammatory reactions, especially due to their ability to bind and activate leukocytes. Hence, we reviewed studies on platelet function of ECMO patients. Moreover, we addressed the issue of platelet–leukocyte aggregates (PLAs), which is a key step in both platelet and leukocyte activation, and deserves to be investigated in these patients. A reduced expression of GPIb and GPVI was found under ECMO therapy, due to the shedding processes. However, defective platelet aggregation is inconsistently reported and is still not clearly defined. Due to the high susceptibility of PLAs to pre-analytical conditions, defining and strictly adhering to a rigorous laboratory methodology is essential for reliable and reproducible results, especially in the setting of complex inflammatory situations like ECMO. We provide results on sample preparation and flow cytometric whole blood evaluation of circulating PLAs.

Changes in Red Blood Cell Properties and Platelet Function during Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is associated with frequent hemorrhagic and thromboembolic complications. The multiple effects of ECMO include inflammatory response on contact with the circuit; hemolysis acquired von Willebrand syndrome likely affects the function of red blood cells (RBC) and platelets. The aim of this prospective observational study was to analyze RBC aggregation and elongation (deformability) and platelet aggregation in the first week of ECMO. Sixteen patients were included. Blood samples were taken prior to initiation of ECMO and on days 1, 2, 3, 5, and 7. RBC aggregation and elongation were analyzed using the laser-assisted optical rotational red cell analyzer (Lorrca). Upstroke, top, and amplitude as indices of aggregation showed significant time effects. RBC elongation was not affected at low shear stress. At high shear stress there was an increase in the elongation index at day 2 (p = 0.004), followed by a decrease. Platelet function was analyzed using multiple electrode aggregometry (Multiplate^®). In pairwise comparison in the days 1–7 to the value prior to ECMO there was no significant difference in platelet aggregation by any of the three agonists (ADP p = 0.61; TRAP p = 0.77; Ristocetin p = 0.25). This implies that the rheology of RBCs seemed to be more affected by ECMO than platelets. Especially the red blood cell deformability continues to decline at higher shear stress.

Acute Respiratory Distress Syndrome (ARDS): Pathophysiological Insights and Lung Imaging

Acute respiratory distress syndrome (ARDS) is in the center of the scientific debate both for its complex pathophysiology and for the discussion about the remedies that could contribute to its healing. The intricate interplay of different body systems that characterizes ARDS is mirrored by two main research threads, one centered on the pathophysiological mechanisms of the disease and the other on the new approaches to lung imaging. In this Special Issue of the Journal of Clinical Medicine are presented studies using imaging technologies based on electrical impedance tomography, synchrotron radiation computed tomography and intravital probe-based confocal laser endomicroscopy. The studies on the pathophysiological mechanisms pertain to the evaluation of the biomarkers of the disease and the platelet disfunction during extracorporeal membrane oxygenation. These contributions witness the intensity of ARDS research as many of the key problems of the disease are only in part resolved.