Platelet Count Trends and Prevalence of Heparin-Induced Thrombocytopenia in a Cohort of Extracorporeal Membrane Oxygenator Patients

Incidence and risk factors associated with stroke when utilizing peripheral VA-ECMO

BACKGROUND

Mechanical circulatory support with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) has brought forward a paradigm shift in the management of cardiogenic shock. Neurological complications associated with VA-ECMO represent a significant source of morbidity and mortality and serve as a limiting factor in its application and duration of use.

METHODS

We performed a single-center retrospective case-control study of patients who developed stroke while managed with peripheral VA-ECMO from January 2018 to September 2022 at a quaternary center. We included consecutive patients above the age of 18 who were admitted to the cardiac intensive care unit and were managed with peripheral VA-ECMO. All patients who developed a stroke while on VA-ECMO were included in the case cohort, and compared to those who did not suffer stroke. Multivariable logistic regression was performed to identify risk factors associated with stroke on VA-ECMO. In-hospital outcomes were assessed out to 30 days.

RESULTS

A total 244 patients were included in the final analysis, 36 (14.7 %) of whom developed stroke on VA-ECMO. Ischemic stroke was seen in 20 patients (55.6 %) whereas hemorrhagic stroke was seen in 16 patients (44.4 %). The use of P2Y12 antagonists (aOR 2.70, p = 0.019), limb ischemia (aOR 4.41, p = 0.002), and blood transfusion requirement (aOR 8.55, p = 0.041) were independently associated with development of stroke on VA-ECMO. Female sex trended towards statistical significance (aOR 2.19, p = 0.053) while age was not independently associated with development of stroke on VA-ECMO. There was no significant association between stroke development and outcomes of VA-ECMO duration, hospital length of stay, and all-cause mortality out to 30-days.

CONCLUSIONS

VA-ECMO carried a considerable risk of neurological complications. Mortality and duration of hemodynamic support was not associated with stroke risk. Awareness regarding stroke risk is imperative in facilitating early identification and management of ischemic and hemorrhagic stroke. Research involving clinical trials and multicenter studies are necessary to empower centers in mitigating this source of significant morbidity and mortality in patients on mechanical circulatory support.

The early decline in platelet count is associated with increased adverse outcomes in non heparin-induced thrombocytopenia pediatric patients undergoing VA-ECMO

INTRODUCTION

The impact of non heparin-induced thrombocytopenia on the clinical outcomes for pediatric cardiac surgery patients who required veno-arterial extracorporeal membrane support (VA-ECMO) for failure to wean from cardiopulmonary bypass (CPB) is uncertain. This study aimed to investigate the relationship between thrombocytopenia and prognosis in these patients.

METHODS

This retrospective study enrolled 96 pediatric patients (age < 18) who received VA-ECMO directly transitioned from CPB at Fuwai Hospital from January 2010 to June 2020. The association between relative decrease in platelet count (△PLT) post-ECMO 24 h and clinical outcomes was explored.

RESULTS

There were significant differences in Post-ECMO 24 h platelet counts, platelet count nadir, and duration of platelet decline between the survivors and non-survivors in CPB-ECMO groups. A positive correlation was found between △PLT post-ECMO 24 h and plasma-free hemoglobin (pFHb) (p = .014, r = 0.305), peak serum creatinine (p = .016, r = 0.299), peak AST (p = .014, r = 0.302), duration of platelet transfusion (p = .032, r = 0.270),The △PLT post-ECMO 24 h had predictive value on in-hospital mortality [(p < .001, AUROC = 0.781 (95% CI: 0.670-0.892)], massive bleeding (p = .001, AUROC 95% CI: 0.627-0.870), hemolysis (p = .046, AUROC 95% CI: 0.510-0.780), and nosocomial infection (p = .020, AUROC 95% CI: 0.536-0.801). Multivariate logistic regression showed that △PLT post-ECMO 24 h was associated with in-hospital mortality and hemolysis.

CONCLUSIONS

The relative early decrease in platelet count 24 h following transition to ECMO is associated with increased patient mortality, and is positively associated with adverse outcomes in pediatric cardiac surgery patients transferred from CPB to ECMO. Moreover, this decline rate can predict in-hospital survival, major bleeding, hemolysis, and hospital-acquired infections.

Heparin-Induced Thrombocytopenia in Patients Suffering Cardiogenic Shock

OBJECTIVES

Cardiogenic shock (CS) is associated with high mortality. Patients treated for CS mostly require heparin therapy, which may be associated with complications such as heparin-induced thrombocytopenia (HIT). HIT represents a serious condition associated with platelet decline and increased hypercoagulability and remains a poorly researched field in intensive care medicine. Primary purpose of this study was to: 1) determine HIT prevalence in CS, 2) assess the performance of common diagnostic tests for the workup of HIT, and 3) compare outcomes in CS patients with excluded and confirmed HIT.

DESIGN

Retrospective dual-center study including adult patients 18 years old or older with diagnosed CS and suspected HIT from January 2010 to November 2022.

SETTING

Cardiac ICU at the Ludwig-Maximilians University hospital in Munich and the university hospital of Bonn.

PATIENTS AND INTERVENTIONS

In this retrospective analysis, adult patients with diagnosed CS and suspected HIT were included. Differences in baseline characteristics, mortality, neurologic and safety outcomes between patients with excluded and confirmed HIT were evaluated.

MEASUREMENTS AND MAIN RESULTS

In cases of suspected HIT, positive screening antibodies were detected in 159 of 2808 patients (5.7%). HIT was confirmed via positive functional assay in 57 of 2808 patients, corresponding to a prevalence rate of 2.0%. The positive predictive value for anti-platelet factor 4/heparin screening antibodies was 35.8%. Total in-hospital mortality (58.8% vs. 57.9%; p > 0.999), 1-month mortality (47.1% vs. 43.9%; p = 0.781), and 12-month mortality (58.8% vs. 59.6%; p > 0.999) were similar between patients with excluded and confirmed HIT, respectively. Furthermore, no significant difference in neurologic outcome among survivors was found between groups (Cerebral Performance Category [CPC] score 1: 8.8% vs. 8.8%; p > 0.999 and CPC 2: 7.8% vs. 12.3%; p = 0.485).

CONCLUSIONS

HIT was a rare complication in CS patients treated with unfractionated heparin and was not associated with increased mortality. Also, HIT confirmation was not associated with worse neurologic outcome in survivors. Future studies should aim at developing more precise, standardized, and cost-effective strategies to diagnose HIT and prevent complications.

Heparin-induced thrombocytopenia in extracorporeal membrane oxygenation-supported patients: a systematic review and meta-analysis

BACKGROUND

In recent years, extracorporeal membrane oxygenation (ECMO) has been increasingly used in critically ill patients with respiratory or cardiac failure. Heparin is usually used as anticoagulation therapy during ECMO support. However, heparin-induced thrombocytopenia (HIT) in ECMO-supported patients, which results in considerable morbidity and mortality, has not yet been well described. This meta-analysis and systematic review aimed to thoroughly report the incidence of HIT on ECMO, as well as the characteristics and outcomes of HIT patients.

METHODS

We searched the PubMed, Embase, Cochrane Library, and Scopus databases for studies investigating HIT in adult patients supported by ECMO. All studies conforming to the inclusion criteria were screened from 1975 to August 2023. Nineteen studies from a total of 1,625 abstracts were selected. The primary outcomes were the incidence of HIT and suspected HIT.

RESULTS

The pooled incidence of HIT in ECMO-supported patients was 4.2% (95% CI: 2.7-5.6; 18 studies). A total of 15.9% (95% CI: 9.0-22.8; 12 studies) of patients on ECMO were suspected of having HIT. Enzyme-linked immunosorbent assay (ELISA) is the most commonly used immunoassay. The median optical density (OD) of the ELISA in HIT-confirmed patients ranged from 1.08 to 2.10. In most studies, the serotonin release assay (SRA) was performed as a HIT-confirming test. According to the subgroup analysis, the pooled incidence of HIT in ECMO patients was 2.7% in studies whose diagnostic mode was functional assays, which is significantly lower than the incidence in studies in which the patients were diagnosed by immunoassay (14.5%). Argatroban was most commonly used as an alternative anticoagulation agent after the withdrawal of heparin. Among confirmed HIT patients, 45.5% (95% CI: 28.8-62.6) experienced thrombotic events, while 50.1% (95% CI: 24.9-75.4) experienced bleeding events. Overall, 46.6% (95% CI: 30.4-63.1) of patients on ECMO with HIT died.

CONCLUSION

According to our study, the pooled incidence of HIT in ECMO-supported patients is 4.2%, and it contributes to adverse outcomes. Inappropriate diagnostic methods can easily lead to misdiagnosis of HIT. Further research and development of diagnostic algorithms and laboratory assays are warranted.

Evaluation of Bivalirudin During Adult Extracorporeal Membrane Oxygenation: A Retrospective Characterization of Dosing, Efficacy and Bleeding

Objective: Although heparin is the current standard anticoagulant during venoarterial (VA) and venovenous (VV) extracorporeal membrane oxygenation (ECMO), factors including heparin-induced thrombocytopenia, heparin resistance and drug shortages necessitate alternative anticoagulants such as direct thrombin inhibitors. The aim was to characterize dosing, safety, and efficacy of bivalirudin during ECMO support. Methods: This retrospective single-center study included 24 adults on ECMO support who received ≥6 hours of bivalirudin. The primary endpoint was dose to first therapeutic activated partial thromboplastin time (aPTT). Secondary endpoints included evaluating dosing between ECMO modes, incidence of bleeding and thrombotic events, and time in therapeutic range (TTR). Results: The dose at time of first therapeutic aPTT was bivalirudin 0.05 [0.05-0.1] mg/kg/hour. Bivalirudin dosing requirements were lower in VAECMO compared to VV-ECMO patients and were not impacted by continuous venovenous hemofiltration. Time to therapeutic aPTT was 5.5 [2-13] hours for VA-ECMO and 4.5 [2-8.6] hours for VV-ECMO patients. During any mode of ECMO TTR was 58.3% [39.6-73.1]. Thrombotic events occurred in 3 (13%) patients and major bleeding occurred in 12 (50%) patients. Conclusions: Our findings demonstrated variable bivalirudin dosing requirements based on mode of ECMO and dosing modifications may not be required during CVVH. Factors including mode of ECMO, indication for bivalirudin and concomitant antiplatelet therapy may impact hematologic events. Application of this data can assist with developing a bivalirudin ECMO protocol which provides less variability in initial dosing and TTR.

Stroke and Mechanical Circulatory Support in Adults

PURPOSE OF THE REVIEW

Short-term and durable mechanical circulatory support (MCS) devices represent life-saving interventions for patients with cardiogenic shock and end-stage heart failure. This review will cover the epidemiology, risk factors, and treatment of stroke in this patient population.

RECENT FINDINGS

Short-term devices such as intra-aortic balloon pump, Impella, TandemHeart, and Venoatrial Extracorporal Membrane Oxygenation, as well as durable continuous-flow left ventricular assist devices (LVADs), improve cardiac output and blood flow to the vital organs. However, MCS use is associated with high rates of complications, including ischemic and hemorrhagic strokes which carry a high risk for death and disability. Improvements in MCS technology have reduced but not eliminated the risk of stroke. Mitigation strategies focus on careful management of anti-thrombotic therapies. While data on therapeutic options for stroke are limited, several case series reported favorable outcomes with thrombectomy for ischemic stroke patients with large vessel occlusions, as well as with reversal of anticoagulation for those with hemorrhagic stroke. Stroke in patients treated with MCS is associated with high morbidity and mortality. Preventive strategies are targeted based on the specific form of MCS. Improvements in the design of the newest generation device have reduced the risk of ischemic stroke, though hemorrhagic stroke remains a serious complication.

The interaction of thrombocytopenia, hemorrhage, and platelet transfusion in venoarterial extracorporeal membrane oxygenation: a multicenter observational study

BACKGROUND

Thrombocytopenia, hemorrhage and platelet transfusion are common in patients supported with venoarterial extracorporeal membrane oxygenation (VA ECMO). However, current literature is limited to small single-center experiences with high degrees of heterogeneity. Therefore, we aimed to ascertain in a multicenter study the course and occurrence rate of thrombocytopenia, and to assess the association between thrombocytopenia, hemorrhage and platelet transfusion during VA ECMO.

METHODS

This was a sub-study of a multicenter (N = 16) study on transfusion practices in patients on VA ECMO, in which a retrospective cohort (Jan-2018-Jul-2019) focusing on platelets was selected. The primary outcome was thrombocytopenia during VA ECMO, defined as mild (100-150·109/L), moderate (50-100·109/L) and severe (< 50·109/L). Secondary outcomes included the occurrence rate of platelet transfusion, and the association between thrombocytopenia, hemorrhage and platelet transfusion, assessed through mixed-effect models.

RESULTS

Of the 419 patients included, median platelet count at admission was 179·109/L. During VA ECMO, almost all (N = 398, 95%) patients developed a thrombocytopenia, of which a significant part severe (N = 179, 45%). One or more platelet transfusions were administered in 226 patients (54%), whereas 207 patients (49%) suffered a hemorrhagic event during VA ECMO. In non-bleeding patients, still one in three patients received a platelet transfusion. The strongest association to receive a platelet transfusion was found in the presence of severe thrombocytopenia (adjusted OR 31.8, 95% CI 17.9-56.5). After including an interaction term of hemorrhage and thrombocytopenia, this even increased up to an OR of 110 (95% CI 34-360).

CONCLUSIONS

Thrombocytopenia has a higher occurrence than is currently recognized. Severe thrombocytopenia is strongly associated with platelet transfusion. Future studies should focus on the etiology of severe thrombocytopenia during ECMO, as well as identifying indications and platelet thresholds for transfusion in the absence of bleeding.

TRIAL REGISTRATION

This study was registered at the Netherlands Trial Registry at February 26th, 2020 with number NL8413 and can currently be found at https://trialsearch.who.int/Trial2.aspx?TrialID=NL8413.

Current and future strategies to monitor and manage coagulation in ECMO patients

Extracorporeal membrane oxygenation (ECMO) can provide life-saving support for critically ill patients suffering severe respiratory and/or cardiac failure. However, thrombosis and bleeding remain common and complex problems to manage. Key causes of thrombosis in ECMO patients include blood contact to pro-thrombotic and non-physiological surfaces, as well as high shearing forces in the pump and membrane oxygenator. On the other hand, adverse effects of anticoagulant, thrombocytopenia, platelet dysfunction, acquired von Willebrand syndrome, and hyperfibrinolysis are all established as causes of bleeding. Finding safe and effective anticoagulants that balance thrombosis and bleeding risk remains challenging. This review highlights commonly used anticoagulants in ECMO, including their mechanism of action, monitoring methods, strengths and limitations. It further elaborates on existing anticoagulant monitoring strategies, indicating their target range, benefits and drawbacks. Finally, it introduces several highly novel approaches to real-time anticoagulation monitoring methods including sound, optical, fluorescent, and electrical measurement as well as their working principles and future directions for research.

Heparin-Induced Thrombocytopenia in Patients Undergoing Venoarterial Extracorporeal Membrane Oxygenation

Background: Heparin-induced thrombocytopenia (HIT) is a serious, immune-mediated adverse drug reaction to unfractionated heparin (UFH) affecting also patients undergoing venoarterial extracorporeal membrane oxygenation (VA-ECMO). Although the association between VA-ECMO support and the development of thrombocytopenia has long been known and discussed, HIT as one underlying cause is still insufficiently understood. Therefore, the purpose of this study was to further investigate the epidemiology, mortality, diagnosis, and clinical management of HIT occurring in VA-ECMO patients treated with UFH. Methods: We conducted a retrospective single-center study including adult patients (≥18 years) with VA-ECMO support in the cardiac intensive care unit (ICU) of the University Hospital of Munich (LMU) between January 2013 and May 2022, excluding patients with a known history of HIT upon admission. Differences in baseline characteristics and clinical outcome between excluded HIT (positive anti-platelet factor 4 (PF4)/heparin antibody test but negative functional assay) and confirmed HIT (positive anti-PF4/heparin antibody test and positive functional assay) VA-ECMO patients as well as diagnosis and clinical management of HIT were analysed. Results: Among the 373 patients included, anti-PF4/heparin antibodies were detected in 53/373 (14.2%) patients. Functional HIT testing confirmed HIT in 13 cases (3.5%) and excluded HIT in 40 cases (10.7%), corresponding to a prevalence of confirmed HIT of 13/373 (3.5%) [1.6, 5.3] and a positive predictive value (PPV) of 24.5% for the antibody screening test. The platelet course including platelet recovery following argatroban initiation was similar between all groups. One-month mortality in patients with excluded HIT was 14/40 (35%) and 3-month mortality 17/40 (43%), compared to 5/13 (38%) (p > 0.999), and 6/13 (46%) (p > 0.999) in patients with confirmed HIT. Neurological outcome in both groups measured by the cerebral performance category of survivors on hospital discharge was similar, as well as adverse events during VA-ECMO therapy. Conclusions: With a prevalence of 3.5%, HIT is a non-frequent complication in patients on VA-ECMO and was not associated with a higher mortality rate. HIT was ultimately excluded by functional essay in 75% of VA-ECMO patients with clinical suspicion of HIT and positive anti-PF4/heparin antibody test. Argatroban seems to be an appropriate and safe therapeutic option for confirmed HIT-positive patients on VA-ECMO support.

The potential impact of Covid-19 on the capacity of routine laboratory tests to detect heparin-induced thrombocytopenia

In Covid-19, anticoagulation with heparin is often administered to prevent or treat thromboembolic events. Heparin-induced thrombocytopenia (HIT) is a severe complication of heparin treatment, caused by heparin-dependent, platelet activating anti-platelet factor 4 (PF4)/heparin antibodies. Diagnosis of HIT is based on the combination of clinical parameters, allowing to determine the pretest probability, and laboratory testing for anti-PF4/heparin antibodies and confirmatory functional assays, such as the heparin-induced platelet activation (HIPA) test.

We report the case of a patient with severe Covid-19 pneumonia requiring ECMO treatment, who developed recurrent clotting of the ECMO filter and a drop in platelet count under heparin treatment. He was therefore suspected to have HIT and the anticoagulation was switched to argatroban. Despite high clinical probability and high titres of anti-PF4/heparin antibodies, the functional HIPA test was negative. Nevertheless, argatroban was continued rather than to reinstate anticoagulation with heparin. Reevaluation 7 days later then demonstrated a strongly positive functional HIPA test and confirmed the diagnosis of HIT. Under anticoagulation with argatroban the patient gradually improved and was finally weaned off the ECMO.

In conclusion, this case highlights the critical importance of clinical judgement, exploiting the 4 T score, given that Covid-19 patients may present a different pattern of routine laboratory test results in HIT diagnostics. The possibility of a false negative HIPA test has to be considered, particularly in early phases of presentation. In cases of a discrepancy with high clinical probability of HIT and/or high titre anti-PF4/heparin antibodies despite a negative HIPA test, a reevaluation within 3 to 5 days after the initial test should be considered in order to avoid precipitant reestablishment of unfractionated heparin, with potentially fatal consequences.

Prevalence and outcomes of patients developing heparin-induced thrombocytopenia during extracorporeal membrane oxygenation

Objectives

Unfractionated heparin (UFH) is the commonly used anticoagulant to prevent clotting of the ECMO circuit and thrombosis of the cannulated vessels. A side effect of UFH is heparin-induced thrombocytopenia (HIT). Little is known about HIT during ECMO and the impact of changing anticoagulation in ECMO patients with newly diagnosed HIT. The aim of the study was to determine the prevalence, complications, impact of switching anticoagulation to argatroban and outcomes of patients developing heparin-induced thrombocytopenia (HIT) during either veno-venous (VV) or veno-arterial (VA) ECMO.

Methods

Retrospective observational single centre study of prospectively collected data of consecutive patients receiving VV ECMO therapy for severe respiratory failure and VA ECMO for circulatory failure from January 2006 to December 2016 of the Medical intensive care unit (ICU) of the University Hospital of Regensburg. Treatment of HIT on ECMO was done with argatroban.

Results

507 patients requiring ECMO were included. Further HIT-diagnostic was conducted if HIT-4T-score was ≥4. The HIT-confirmed group had positive HIT-enzyme-linked-immunosorbent-assay (ELISA) and positive heparin-induced-platelet-activation (HIPA) test, the HIT-suspicion group a positive HIT-ELISA and missing HIPA but remained on alternative anticoagulation until discharge and the HIT-excluded group a negative or positive HIT-ELISA, however negative HIPA. These were compared to group ECMO-control without any HIT suspicion. The prevalence of HIT-confirmed was 3.2%, of HIT-suspicion 2.0% and HIT-excluded 10.8%. Confirmed HIT was trendwise more frequent in VV than in VA (3.9 vs. 1.7% p = 0.173). Compared to the ECMO control group, patients with confirmed HIT were longer on ECMO (median 13 vs. 8 days, p = 0.002). Different types of complications were higher in the HIT-confirmed than in the ECMO-control group, but in-hospital mortality was not different (31% vs. 41%, p = 0.804).

Conclusion

HIT is rare on ECMO, should be suspected, if platelets are decreasing, but seems not to increase mortality if treated promptly.

Thrombosis and coagulopathy in COVID-19 patients rceiving ECMO: A narrative review of current literature

Extracorporeal membrane oxygenation (ECMO) is an established part of the treatment algorithm for coronavirus disease 2019 (COVID-19)-related acute respiratory distress syndrome. An intense inflammatory response may cause an imbalance in the coagulation cascade making both thrombosis and bleeding common and notable features of the clinical management of these patients. Large observational and retrospective studies provide a better understanding of the pathophysiology and management of bleeding and thrombosis in COVID-19 patients requiring ECMO. Clinically significant bleeding, including intracerebral hemorrhage, is an independent predictor of mortality, and thrombosis (particularly pulmonary embolism) is associated with mortality, especially if occurring with right ventricular dysfunction. The incidence of heparin-induced thrombocytopenia is higher than the general patient cohort with acute respiratory distress syndrome or other indications for ECMO. The use of laboratory parameters to predict bleeding or thrombosis has a limited role. In this review, the authors discuss the complex pathophysiology of bleeding and thrombosis observed in patients with COVID-19 during ECMO support, and their effects on outcomes.

Evaluation of anticoagulation with bivalirudin for heparin-induced thrombocytopenia during extracorporeal membrane oxygenation

INTRODUCTION

Unfractionated heparin is the most commonly utilized anticoagulant in extracorporeal membrane oxygenation (ECMO) due to clinician familiarity, ease of reversal, and low cost compared to alternative agents. However, heparin's anticoagulant effect can be unpredictable and its use accompanies a risk of heparin induced thrombocytopenia (HIT). Successful use of bivalirudin as an alternative to heparin in non-HIT ECMO patients has previously been described. However, there is a paucity of data regarding its utilization in patients with confirmed HIT on ECMO.

METHODS

This single-center retrospective chart review at Cleveland Clinic Main Campus included 12 ECMO patients who were managed with bivalirudin for a new diagnosis of HIT. Descriptive statistical analyses were performed utilizing median with interquartile range and number with percent as appropriate.

RESULTS

Of the 12 patients included, median ECMO duration was 328.5 (218.8-502.1) h and venoarterial ECMO was the most common configuration. No patients experienced the primary outcome of in-circuit thrombosis while on bivalirudin. One patient developed a deep vein thrombosis 22.5 h after switching from heparin to bivalirudin. Major bleeding occurred during bivalirudin therapy in 8 (66.7%) patients.

CONCLUSIONS

Overall, our study results suggest that bivalirudin is effective for the management of HIT and did not show evidence of in-circuit thrombosis. A high incidence of major bleeding was observed with bivalirudin use within this study. Clinicians should view bivalirudin as an acceptable agent for the treatment of HIT in the ECMO population, but must consider bleeding risk given the lack of effective reversal agents.

Neurologic Complications in Adult Post-cardiotomy Cardiogenic Shock Patients Receiving Venoarterial Extracorporeal Membrane Oxygenation: A Cohort Study

Background: This study aims to describe the prevalence of neurologic complications and hospital outcome in adult post-cardiotomy cardiogenic shock (PCS) patients receiving veno-arterial extracorporeal membrane oxygenation (V-A ECMO) support and factors associated with such adverse events.

Methods: Four hundred and fifteen adult patients underwent cardiac surgery and received V-A ECMO for more than 24 h because of PCS. Patients were divided into two groups: those who developed a neurological complication and those who did not (control group). Multivariable logistic regression was performed to identify factors independently associated with neurologic complications.

Results: Neurologic complications occurred in 87 patients (21.0%), including cerebral infarction in 33 patients (8.0%), brain death in 30 patients (7.2%), seizures in 14 patients (3.4%), and intracranial hemorrhage in 11 (2.7%) patients. In-hospital mortality in patients with neurologic complications was 90.8%, compared to 52.1% in control patients (p < 0.001). In a multivariable model, the lowest systolic blood pressure (SBP) level pre-ECMO (OR, 0.89; 95% CI: 0.86–0.93) and aortic surgery combined with coronary artery bypass grafting (OR, 9.22; 95% CI: 2.10–40.55) were associated with overall neurologic complications. Age (OR, 1.06; 95% CI: 1.01–1.12) and lowest SBP (OR, 0.81; 95% CI: 0.76–0.87) were correlative factors of brain death. Coagulation disorders (OR, 9.75; 95% CI: 1.83–51.89) and atrial fibrillation (OR, 12.19; 95% CI: 1.22–121.61) were shown to be associated independently with intracranial hemorrhage, whereas atrial fibrillation (OR, 8.15; 95% CI: 1.31–50.62) was also associated with cerebral infarction.

Conclusions: Neurologic complications in adult PCS patients undergoing V-A ECMO support are frequent and associated with higher in-hospital mortality. Identified risk factors of neurologic complications might help to improve ECMO management and might reduce their occurrence.

Frequency of Thrombocytopenia and Heparin-Induced Thrombocytopenia in Patients Receiving Extracorporeal Membrane Oxygenation Compared With Cardiopulmonary Bypass and the Limited Sensitivity of Pretest Probability Score

OBJECTIVES

To ascertain: 1) the frequency of thrombocytopenia and heparin-induced thrombocytopenia; 2) positive predictive value of the Pretest Probability Score in identifying heparin-induced thrombocytopenia; and 3) clinical outcome of heparin-induced thrombocytopenia in adult patients receiving venovenous- or venoarterial-extracorporeal membrane oxygenation, compared with cardiopulmonary bypass.

DESIGN

A single-center, retrospective, observational cohort study from January 2016 to April 2018.

SETTING

Tertiary referral center for cardiac and respiratory failure.

PATIENTS

Patients who received extracorporeal membrane oxygenation for more than 48 hours or had cardiopulmonary bypass during specified period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Clinical and laboratory data were collected retrospectively. Pretest Probability Score and heparin-induced thrombocytopenia testing results were collected prospectively. Mean age (± SD) of the extracorporeal membrane oxygenation and cardiopulmonary bypass cohorts was 45.4 (± 15.6) and 64.9 (± 13), respectively (p < 0.00001). Median duration of cardiopulmonary bypass was 4.6 hours (2-16.5 hr) compared with 170.4 hours (70-1,008 hr) on extracorporeal membrane oxygenation. Moderate and severe thrombocytopenia were more common in extracorporeal membrane oxygenation compared with cardiopulmonary bypass throughout (p < 0.0001). Thrombocytopenia increased in cardiopulmonary bypass patients on day 2 but was normal in 83% compared with 42.3% of extracorporeal membrane oxygenation patients at day 10. Patients on extracorporeal membrane oxygenation also followed a similar pattern of platelet recovery following cessation of extracorporeal membrane oxygenation. The frequency of heparin-induced thrombocytopenia in extracorporeal membrane oxygenation and cardiopulmonary bypass were 6.4% (19/298) and 0.6% (18/2,998), respectively (p < 0.0001). There was no difference in prevalence of heparin-induced thrombocytopenia in patients on venovenous-extracorporeal membrane oxygenation (8/156, 5.1%) versus venoarterial-extracorporeal membrane oxygenation (11/142, 7.7%) (p = 0.47). The positive predictive value of the Pretest Probability Score in identifying heparin-induced thrombocytopenia in patients post cardiopulmonary bypass and on extracorporeal membrane oxygenation was 56.25% (18/32) and 25% (15/60), respectively. Mortality was not different with (6/19, 31.6%) or without (89/279, 32.2%) heparin-induced thrombocytopenia in patients on extracorporeal membrane oxygenation (p = 0.79).

CONCLUSIONS

Thrombocytopenia is already common at extracorporeal membrane oxygenation initiation. Heparin-induced thrombocytopenia is more frequent in both venovenous- and venoarterial-extracorporeal membrane oxygenation compared with cardiopulmonary bypass. Positive predictive value of Pretest Probability Score in identifying heparin-induced thrombocytopenia was lower in extracorporeal membrane oxygenation patients. Heparin-induced thrombocytopenia had no effect on mortality.

The complicated relationships of heparin-induced thrombocytopenia and platelet factor 4 antibodies with COVID-19

COVID‐19 (coronavirus disease 2019) represents a prothrombotic disorder, and there have been several reports of platelet factor 4/heparin antibodies being present in COVID‐19‐infected patients. This has thus been identified in some publications as representing a high incidence of heparin‐induced thrombocytopenia (HIT), whereas in others, findings have been tempered by general lack of functional reactivity using confirmation assays of serotonin release assay (SRA) or heparin‐induced platelet aggregation (HIPA). Moreover, in at least two publications, data are provided suggesting that antibodies can arise in heparin naïve patients or that platelet activation may not be heparin‐dependent. From this literature, we would conclude that platelet factor 4/heparin antibodies can be observed in COVID‐19‐infected patients, and they may occur at higher incidence than in historical non‐COVID‐19‐infected cohorts. However, the situation is complex, since not all platelet factor 4/heparin antibodies may lead to platelet activation, and not all identified antibodies are heparin‐dependent, such that they do not necessarily reflect “true” HIT. Most recently, a “HIT‐like” syndrome has reported in patients who have been vaccinated against COVID‐19. Accordingly, much more is yet to be learnt about the insidious disease that COVID‐19 represents, including autoimmune outcomes in affected patients.

Platelet factor-4 concentration in adult veno-arterial ECMO patients

BACKGROUND

Heparin induced thrombocytopenia (HIT) is reported at a variable rate in extracorporeal membrane oxygenation (ECMO) patients. A critical factor impacting platelet factor-4 (PF4)-heparin antibody formation is plasma PF4 concentration. We hypothesized that PF4 concentration would be increased during veno-arterial (VA) ECMO.

METHODS

Plasma PF4 concentration was measured during the first 5 ECMO days in 20 VA ECMO patients and 10 control plasma samples. PF4-heparin ratios were estimated using an assumed heparin concentration of 0.4 IU/mL. This correlates with an activated partial thromboplastin time of 60 to 80 seconds, which is the anticoagulation target in our center.

RESULTS

Twenty VA ECMO patients were enrolled, 10 of which had pulmonary embolism. Median PF4 concentration was 0.03 µg/mL [0.01, 0.13] in control plasma. Median PF4 concentration was 0.21 µg/mL [0.12, 0.34] on ECMO day 1 or 2, 0.16 µg/mL [0.09, 0.25] on ECMO day 3, and 0.12 µg/mL [0.09, 0.22] on ECMO day 5. Estimated median PF4-heparin ratios were 0.04, 0.03, and 0.02 respectively. Two patients (10%) developed HIT that was confirmed by serotonin release assay. PF4 concentration did not differ significantly in these patients compared to non-HIT patients (p = 0.37). No patient had an estimated PF4-heparin ratio between 0.7 and 1.4, which is the reported optimal range for PF4-heparin antibody formation.

CONCLUSION

Our data suggest that PF4 concentration is mildly elevated during VA ECMO compared to control plasma. Estimated PF4-heparin ratios were not optimal for HIT antibody formation. These data support epidemiologic studies where HIT incidence is low during VA ECMO.

Platelet count trends and response to fondaparinux in a cohort of heparin-induced thrombocytopenia suspected patients after pulmonary endarterectomy

A definitive diagnosis of heparin-induced thrombocytopenia (HIT) is difficult to make, especially in patients undergoing cardiac surgery. In this retrospective cohort study, we assessed the platelet count trends and the response to fondaparinux in a population of patients of suspected HIT after pulmonary endarterectomy (PEA). Patients enrolled in this study were over the age of 18 years, and survived longer than 7 days after PEA between January 1, 2011 and December 31, 2015. HIT likelihood was assessed by the 4 T's score and interpreted by our institutional algorithm. 54 patients were operated, and 49 patients met the inclusion criteria. Six patients met the criteria for suspected HIT and were treated with fondaparinux until the platelet recovered. No significant difference was observed of clinical characteristics between intermediate to high HIT likelihood patients (HIT SUSPECTED) and low HIT likelihood patients (NO HIT SUSPECTED). HIT SUSPECTED patients reached platelet count lowest later (about 5.5 days after PEA), while NO HIT SUSPECTED patients is about 4.0 days after PEA. Percentage of platelet counts decrease (> 50%) was larger than NO HIT SUSPECTED patients (< 50%). There was no difference in mortality or residual pulmonary hypertension between HIT SUSPECTED and NO HIT SUSPECTED patients. Two HIT SUSPECTED patients who used heparin after PEA died, the other four survived by replacing heparin or low molecular weight heparin with fondaparinux. Suspected HIT patients should be surveilled carefully. Platelet counts trends may have some hints in the prevention of HIT. Fondaparinux may be effective for patients with suspected HIT.

Complications associated with mechanical circulatory support

There has been a significant increase in the utilisation of mechanical circulatory support (MCS) devices for the management of cardiogenic shock over recent years, with new devices being developed and introduced with the aim of improving outcomes for this group of patients. MCS devices may be used as a bridge to recovery or transplantation or intended as a destination therapy. Although these devices are not without their complications, good outcomes are achieved, but not without risk of significant complications. In this article, the complications of MCS devices have been reviewed, including the intra-aortic balloon pump (IABP), Impella, TandemHeart, extracorporeal membrane oxygenation (ECMO) and ventricular assist devices (VAD)—temporary and durable.

Platelets and extra-corporeal membrane oxygenation in adult patients: a systematic review and meta-analysis

Despite increasing improvement in extracorporeal membrane oxygenation (ECMO) technology and knowledge, thrombocytopenia and impaired platelet function are usual findings in ECMO patients and the underlying mechanisms are only partially elucidated. The purpose of this meta-analysis and systematic review was to thoroughly summarize and discuss the existing knowledge of platelet profile in adult ECMO population. All studies meeting the inclusion criteria (detailed data about platelet count and function) were selected, after screening literature from July 1975 to August 2019. Twenty-one studies from 1.742 abstracts were selected. The pooled prevalence of thrombocytopenia in ECMO patients was 21% (95% CI 12.9-29.0; 14 studies). Thrombocytopenia prevalence was 25.4% (95% CI 10.6-61.4; 4 studies) in veno-venous ECMO, whereas it was 23.2% (95% CI 11.8-34.5; 6 studies) in veno-arterial ECMO. Heparin-induced thrombocytopenia prevalence was 3.7% (95% CI 1.8-5.5; 12 studies). Meta-regression revealed no significant association between ECMO duration and thrombocytopenia. Platelet function impairment was described in 7 studies. Impaired aggregation was shown in 5 studies, whereas loss of platelet receptors was found in one trial, and platelet activation was described in 2 studies. Platelet transfusions were needed in up to 50% of the patients. Red blood cell transfusions were administered from 46 to 100% of the ECMO patients. Bleeding events varied from 16.6 to 50.7%, although the cause and type of haemorrhage was not consistently reported. Thrombocytopenia and platelet dysfunction are common in ECMO patients, regardless the type of ECMO mode. The underlying mechanisms are multifactorial, and understanding and management are still limited. Further research to design appropriate strategies and protocols for its monitoring, management, or prevention should be matter of thorough investigations.

Detection of Platelet-Activating Antibodies Associated with Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a prothrombotic immune drug reaction caused by platelet-activating antibodies that in most instances recognize platelet factor 4 (PF4)/polyanion complexes. Platelet activation assays (i.e., functional assays) are more specific than immunoassays, since they are able to discern clinically relevant heparin-induced antibodies. All functional assays used for HIT diagnosis share the same principle, as they assess the ability of serum/plasma from suspected HIT patients to activate fresh platelets from healthy donors in the presence of several concentrations of heparin. Depending on the assay, donors’ platelets are stimulated either in whole blood (WB), platelet-rich plasma (PRP), or in a buffer medium (washed platelets, WP). In addition, the activation endpoint studied varies from one assay to another: platelet aggregation, membrane expression of markers of platelet activation, release of platelet granules. Tests with WP are more sensitive and serotonin release assay (SRA) is considered to be the current gold standard, but functional assays suffer from certain limitations regarding their sensitivity, specificity, complexity, and/or accessibility. However, the strict adherence to adequate preanalytical conditions, the use of selected platelet donors and the inclusion of positive and negative controls in each run are key points that ensure their performances.

Safety and Efficacy of a Novel Pneumatically Driven Extracorporeal Membrane Oxygenation Device

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is rapidly becoming a mainstream technology for lung or heart/lung support. Current ECMO devices mostly consist of a power-driven centrifugal pump and a dedicated oxygenator. We studied the safety and efficacy of a novel, fully pneumatically driven ECMO device, which could be used in both venovenous or venoarterial mode in an animal model.

METHODS

Six healthy, awake sheep were treated with the Mobybox ECMO device (Hemovent, Aachen, Germany) over a 7-day period in a venovenous mode. Gas exchange, coagulation parameters, and safety were assessed.

RESULTS

Using a blood flow rate of 2 L/min and a low sweep gas flow rate of 0.3 L/min, the PCO₂ ranged from 38 to 44 mm Hg pre oxygenator and dropped to 32 to 36 mm Hg post oxygenator, whereas the PaO₂ post oxygenator increased to 600 mm Hg. Higher levels of sweep gas flow resulted in cessation of spontaneous breathing in some animals, consistent with high-efficiency carbon dioxide removal; thus, the sweep gas flow rate was maintained at a low level. Platelets dropped from 177 ± 53/μL to 107 ± 28/μL on day 2, while returning to baseline by day 7 (180 ± 51/μL). Plasma-free hemoglobin remained low (2-9 mg/dL), whereas fibrinogen slightly increased, and then remained stable throughout the period. Neither the pump nor the oxygenator showed any visible clotting after 7 days.

CONCLUSIONS

The pneumatically driven ECMO device provided excellent safety and physiologic efficacy in a 7-day sheep experiment without visible clotting, hemolysis, or sustained reductions in fibrinogen or platelets.

Extracorporeal membrane oxygenation without therapeutic anticoagulation in adults: A systematic review of the current literature

Extracorporeal membrane oxygenation is essential for the treatment of refractory cardiopulmonary failure. Its use may be complicated by worse haemorrhagic complications exacerbated by extracorporeal membrane oxygenation–related therapeutic anticoagulation. Progressive technological advancements have made extracorporeal membrane oxygenation components less thrombogenic, potentially allowing its application with temporary avoidance of systemic anticoagulants. A systematic review of all the available experiences, reporting the use of extracorporeal membrane oxygenation without systemic anticoagulation in the published literature was performed. Only patient series were included, irrespective of the clinical indication. The survival, extracorporeal membrane oxygenation system–related dysfunction and complications rates, as well as in-hospital outcome, were analysed. Six studies were selected for the analysis. Veno-arterial extracorporeal membrane oxygenation was used in 84% of patients, while veno-venous extracorporeal membrane oxygenation was applied in the remaining cases. Anticoagulation was avoided because of the high risk of bleeding after cardiac surgery (64%), active major bleeding (23%) or presence of severe traumatic injury (9%). Duration of support ranged from 0.3 to 1128 h. Heparin was antagonized by protamine in all the post-cardiotomy cases. Successfully extracorporeal membrane oxygenation weaning was achieved in 74% of the treated cases, with a hospital discharge of 58% of patients. Rates of extracorporeal membrane oxygenation malfunctioning due to clot formation and blood transfusion requirement varied remarkably in the published series. Extracorporeal membrane oxygenation without systemic anticoagulation appears feasible in selected circumstances. Further investigations are warranted to elucidate actual aspects regarding extracorporeal membrane oxygenation system performance, related adverse events and benefits associated with this management.

Complications of Temporary Percutaneous Mechanical Circulatory Support for Cardiogenic Shock: An Appraisal of Contemporary Literature

Cardiogenic shock (CS) is associated with hemodynamic compromise and end-organ hypoperfusion due to a primary cardiac etiology. In addition to vasoactive medications, percutaneous mechanical circulatory support (MCS) devices offer the ability to support the hemodynamics and prevent acute organ failure. Despite the wide array of available MCS devices for CS, there are limited data on the complications from these devices. In this review, we seek to summarize the complications of MCS devices in the contemporary era. Using a systems-based approach, this review covers domains of hematological, neurological, vascular, infectious, mechanical, and miscellaneous complications. These data are intended to provide a balanced narrative and aid in risk-benefit decision-making in this acutely ill population.

Predictive value of scoring tools in determining heparin-induced thrombocytopenia in patients on extracorporeal membrane oxygenation

There are currently no scoring tools validated for use in predicting heparin-induced thrombocytopenia in patients receiving extracorporeal membrane oxygenation. This study aims to determine the predictive value of the Warkentin 4T score, Lilo-Le Louet score, and the heparin-induced thrombocytopenia expert probability score in detecting heparin-induced thrombocytopenia in patients on extracorporeal membrane oxygenation. This was a single center, retrospective, observational cohort study of patients at Rush University Medical Center. Heparin-induced thrombocytopenia–positive patients were defined as those with an optical density greater than or equal to 0.4, consistent with a positive anti-platelet 4 heparin antibody. Out of 39 patients on extracorporeal membrane oxygenation with suspected heparin-induced thrombocytopenia, six (15.4%) were found to be anti-platelet 4–positive. A heparin-induced thrombocytopenia diagnosis was confirmed by serotonin-release assay in two patients (5.1%). The 4T, heparin-induced thrombocytopenia expert probability, and Lilo-Le Louet scoring tools all demonstrated a low positive predictive value (21.4%, 16.7%, and 6.7%, respectively), with the 4T and heparin-induced thrombocytopenia expert probability scores demonstrating the highest specificity (66.7% and 84.8%, respectively) and lowest sensitivity (50% and 16.7%, respectively). The Lilo-Le Louet score had high sensitivity (100%) and low specificity (12.5%) in post-cardiopulmonary bypass patients. Based on the findings of this study, all three scoring tools have limited utility for predicting heparin-induced thrombocytopenia in patients on extracorporeal membrane oxygenation.

Heparin-induced thrombocytopenia complicating extracorporeal membrane oxygenation support: Review of the literature and alternative anticoagulants

Heparin-induced thrombocytopenia (HIT) is a life-threatening prothrombotic, immune-mediated complication of unfractionated heparin and low molecular weight heparin therapy. HIT is characterized by moderate thrombocytopenia 5-10 days after initial heparin exposure, detection of platelet-activating anti-platelet factor 4/heparin antibodies and an increased risk of venous and arterial thrombosis. Extracorporeal membrane oxygenation (ECMO) is a form of mechanical circulatory support used in critically ill patients with respiratory or cardiac failure. Systemic anticoagulation is used to alleviate the thrombotic complications that may occur when blood is exposed to artificial surfaces within the ECMO circuit. Therefore, when HIT complicates patients on ECMO support, it is associated with a high thrombotic morbidity and mortality. The risk for HIT correlates with the accumulative dosage of heparin exposure. In ECMO patients receiving continuous infusion of heparin for circuit patency, the risk for HIT is not neglected and must be thought of in the differential diagnosis of the appropriate clinical and laboratory circumstances. The following article reviews the current knowledge in HIT complicating ECMO patients and the alternative anticoagulation options in the presence of HIT.

Heparin-induced thrombocytopenia in patients on extracorporeal membrane oxygenation and the role of a heparin-bonded circuit

Background:

In patients supported with extracorporeal membrane oxygenation, and who develop heparin-induced thrombocytopenia, there is no clear evidence to support changing to a non-heparin-coated extracorporeal membrane oxygenation circuit. Our goal was to evaluate clinical outcomes of patients who were continued on heparin-bonded circuits despite diagnosed heparin-induced thrombocytopenia.

Methods:

We completed a single-center retrospective study of all patients who underwent extracorporeal membrane oxygenation support from July 2008 to July 2017 and were tested heparin-induced thrombocytopenia positive while on extracorporeal membrane oxygenation support. After diagnosis of heparin-induced thrombocytopenia, mean platelet count (k/µL) was measured on consecutive days for 14 days.

Results:

Out of 455 patients, 14 (3.1%) had a diagnosis of heparin-induced thrombocytopenia by serotonin release assay and systemic heparin treatment was discontinued in every case. In total, 11 of the heparin-induced thrombocytopenia patients (78.6%) survived to discharge. The overall survival of all 455 extracorporeal membrane oxygenation patients was 54.1%. Platelets counts after discontinuation of systemic heparin in the heparin-induced thrombocytopenia patients increased from a mean of 59.8 k/µL at time of heparin-induced thrombocytopenia diagnosis to a mean of 280.2 k/µL at 14 days after discontinuation of heparin despite continuation of the heparin-bonded circuit. Platelet count increased in heparin-induced thrombocytopenia patients on extracorporeal membrane oxygenation support after discontinuation of systemic heparin even if maintained on the heparin-bonded circuit.

Conclusion:

Discontinuation of systemic heparin but continuation of heparin-coated extracorporeal membrane oxygenation circuits appeared to be an appropriate response for our extracorporeal membrane oxygenation–supported patients who developed heparin-induced thrombocytopenia. Survival in this group was not significantly different to those patients on extracorporeal membrane oxygenation without heparin-induced thrombocytopenia. Larger studies should evaluate the safety of heparin-bonded extracorporeal membrane oxygenation systems in heparin-induced thrombocytopenia patients.

Heparin-induced thrombocytopenia during extracorporeal life support: incidence, management and outcomes

Background

Heparin-induced thrombocytopenia (HIT) is a severe antibody-mediated reaction leading to transient prothrombosis. However, its incidence in patients on extracorporeal life support (ECLS) is not well described. The aim of this systematic review was to report the incidence of HIT in patients on ECLS, as well as compare the characteristics and outcomes of HIT in patients undergoing veno-arterial extracorporeal membrane oxygenation (VA-ECMO) and veno-venous ECMO (VV-ECMO).

Methods

An electronic search was performed to identify all studies in the English literature examining outcomes of patients with HIT on ECLS. All identified articles were systematically assessed using specific inclusion and exclusion criteria. Random effects meta-analysis as well as univariate analysis was performed.

Results

Of 309 patients from six retrospective studies undergoing ECLS, 83% were suspected, and 17% were confirmed to have HIT. Due to the sparsity of relevant retrospective data regarding patients with confirmed HIT on ECLS, patient-based data was subsequently collected on 28 patients from case reports and case series. Out of these 28 patients, 53.6% and 46.4% of them underwent VA-ECMO and VV-ECMO, respectively. Patients on VA-ECMO had a lower median platelet count nadir (VA-ECMO: 26.0 vs. VV-ECMO: 45.0 per µL, P=0.012) and were more likely to experience arterial thromboembolism (VA-ECMO: 53.3% vs. VV-ECMO: 0.0%, P=0.007), though there was a trend towards decreased likelihood of experiencing ECLS circuit oxygenator thromboembolism (VA-ECMO: 0.0% vs. VV-ECMO: 30.8%, P=0.075) and thromboembolism necessitating ECLS device or circuit exchange (VA-ECMO: 13.3% vs. VV-ECMO 53.8%, P=0.060). Kaplan-Meier survival plots including time from ECLS initiation reveal no significant differences in survival in patients supported on VA-ECMO as compared to VV-ECMO (P=0.300).

Conclusions

Patients who develop HIT on VA-ECMO are more likely to experience more severe thrombocytopenia and arterial thromboembolism than those on VV-ECMO. Further research in this area and development of standardized protocols for the monitoring, diagnosis and management of HIT in patients on ECLS support are warranted.

Adult cardiac veno-arterial extracorporeal life support (VA-ECMO): prevention and management of acute complications

Background

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) has been shown to be a viable and effective treatment for patients suffering from refractory cardiogenic shock (rCS), which is associated with high mortality rates. Although ECMO therapy used as short-term mechanical circulatory support (MCS) has shown tremendous growth in its application over the past decade, the complication and mortality rates remain high. This retrospective study analyzes complications associated with VA-ECMO support, evaluates the use of defined protocols at a single center, and examines factors that may contribute to patient complication and mortality.

Methods

This retrospective analysis included 184 patients who were supported with ECMO from September 2014 through March 2018 at Integris Baptist Medical Center (IBMC). Descriptive statistics were generated to analyze baseline characteristics, demographics, complications, and outcomes.

Results

Acute myocardial infarct (AMI) was the primary etiology of this cohort (N=40; 22%). The mean age was 55±15 (median 56, range 15-84) years. All patients were inotrope and/or vasopressor dependent prior to ECMO initiation. Mean time on ECMO support was 7.8±7.9 days with median time of 6 days. Total patient days on support were 1,430. Most ECMO cannulations, 97 (52%) were performed within Integris Baptist Medical Center, with 48% done outside the hospital; 38% were performed outside of the hospital by the IBMC ECMO team, and 10.5% were performed by an outside team. Bleeding was noted to be the most common VA ECMO complication [N=41; 22.3%; 0.028 events per patient day (EPPD)].

Conclusions

A dedicated 24/7 ECMO service using a multidisciplinary team (MDT) and defined protocols in a single center is able to effectively reduce complications due to VA-ECMO support in the sickest of the sick VA-ECMO patients.

Heparin-induced thrombocytopenia complicating extracorporeal membrane oxygenation support in pediatric patients: review of the literature and alternative anticoagulants

Heparin-induced thrombocytopenia (HIT) is a prothrombotic, immune-mediated complication of unfractionated heparin (UFH) and low molecular weight heparin therapy. HIT is characterized by moderate thrombocytopenia 5-10 days after initial heparin exposure, detection of platelet-activating anti-platelet factor 4/heparin antibodies and an increased risk of venous and arterial thrombosis. Extracorporeal membrane oxygenation (ECMO) is a form of mechanical circulatory support used in critically ill patients with respiratory or cardiac failure. Systemic anticoagulation is used to alleviate the thrombotic complications that may occur when blood is exposed to artificial surfaces within the ECMO circuit. Therefore, when HIT complicates patients on ECMO support, it is associated with a high thrombotic morbidity and mortality. The following article reviews the current knowledge in pediatric HIT, especially in ECMO patients, and the alternative anticoagulation options in the presence of HIT.

Prevalence and outcome of heparin-induced thrombocytopenia diagnosed under veno-arterial extracorporeal membrane oxygenation: a retrospective nationwide study

PURPOSE

Thrombocytopenia is a frequent and serious adverse event in patients treated with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for refractory cardiogenic shock. Similarly to postcardiac surgery patients, heparin-induced thrombocytopenia (HIT) could represent the causative underlying mechanism. However, the epidemiology as well as related mortality regarding HIT and VA-ECMO remains largely unknown. We aimed to define the prevalence and associated 90-day mortality of HIT diagnosed under VA-ECMO.

METHODS

This retrospective study included patients under VA-ECMO from 20 French centers between 2012 and 2016. Selected patients were hospitalized for more than 3 days with high clinical suspicion of HIT and positive anti-PF4/heparin antibodies. Patients were classified according to results of functional tests as having either Confirmed or Excluded HIT.

RESULTS

A total of 5797 patients under VA-ECMO were screened; 39/5797 met the inclusion criteria, with HIT confirmed in 21/5797 patients (0.36% [95% CI] [0.21-0.52]). Fourteen of 39 patients (35.9% [20.8-50.9]) with suspected HIT were ultimately excluded because of negative functional assays. Drug-induced thrombocytopenia tended to be more frequent in Excluded HIT at the time of HIT suspicion (p = 0.073). The platelet course was similar between Confirmed and Excluded HIT (p = 0.65). Mortality rate was 33.3% [13.2-53.5] in Confirmed and 50% [23.8-76.2] in Excluded HIT (p = 0.48).

CONCLUSIONS

Prevalence of HIT among patients under VA-ECMO is extremely low at 0.36% with an associated mortality rate of 33.3%, which appears to be in the same range as that observed in patients treated with VA-ECMO without HIT. In addition, HIT was ultimately ruled out in one-third of patients with clinical suspicion of HIT and positive anti-PF4/heparin antibodies.