Activated Clotting Times Demonstrate Weak Correlation With Heparin Dosing in Adult Extracorporeal Membrane Oxygenation

Anticoagulation and associated complications in veno-arterial extracorporeal membrane oxygenation in adult patients: A systematic review and meta-analysis

Objective

To describe the incidence of bleeding and thrombotic complications in VA-ECMO according to anticoagulation strategy.

Design

This systematic review and meta-analysis included randomised controlled trials (RCTs) and observational studies reporting bleeding and thrombotic complications in VA-ECMO. The incidence of primary outcomes according to anticoagulation drug and monitoring test was described.

Data sources

CENTRAL, MEDLINE, Embase and CINAHL (2010-January 2024).

Review methods

Data was extracted using Covidence. A meta-analysis of proportions was performed using STATA MP v18.1 metaprop.

Results

We included 159 studies with 21,942 patients. No studies were at low risk of bias. The incidence of major bleeding or thrombotic events was similar among heparin-, bivalirudin- and anticoagulation-free cohorts. The pooled incidence of major bleeding and thrombotic complications were 40% (95%CI 36-44, I2 = 97.12) and 17% (95%CI 14-19, I 2  = 92.60%), respectively. The most common bleeding site was thoracic. The most common ischaemic complication was limb ischaemia. The incidences of major bleeding or thrombotic events, intracranial haemorrhage and ischaemic stroke were similar among all monitoring tests. Mechanical unloading was associated with a high incidence of major bleeding events (60%, 95%CI 43-77, I2 = 93.32), and ischaemic strokes (13%, 95%CI 7-19, I2 = 81.80).

Conclusions

Available literature assessing the association between anticoagulation strategies in VA-ECMO, and bleeding and thrombosis is of limited quality. We identified a substantially higher incidence of major bleeding events than a previous meta-analysis. Limited numbers of patients anticoagulated with alternatives to heparin were reported. Patients with additional mechanical LV unloading represent a cohort at particular risk of bleeding and thrombotic complications.

Anticoagulation Monitoring Using Activated Clotting Time in Patients Receiving Extracorporeal Membrane Oxygenation: A Meta-Analysis of Correlation Coefficients

OBJECTIVE

Extracorporeal membrane oxygenation (ECMO) requires systemic anticoagulation to maintain the circuit patency. However, the use of anticoagulation carries a risk of severe hemorrhage, necessitating rigorous monitoring. Activated clotting time (ACT) is a widely used monitoring tool; however, the evidence of its correlation with unfractionated heparin (UFH) infusion dose is limited. Here we aimed to analyze the correlation between ACT and UFH infusion during ECMO.

DESIGN

Systematic literature review and meta-analysis of correlation coefficients (Scopus and PubMed, up to July 13, 2024).

PROSPERO

CRD42023448888 SETTING: All retrospective and prospective studies PARTICIPANTS: Patients receiving ECMO support INTERVENTION: Anticoagulation monitoring during ECMO support MEASUREMENTS AND MAIN RESULTS: Nineteen studies were included in the analysis, and the meta-analysis encompassed 16 studies. The vast majority of studies (n = 15) found a weak correlation, and no study reported a strong correlation between ACT and UFH infusion dose. The meta-analysis (n = 12,625 samples) identified a weak correlation, with a pooled estimate of correlation coefficients of 0.132 (95% confidence interval 0.03-0.23). The most common adverse events were hemorrhage (pooled incidence, 45%) and thrombosis (30%), and 47% of the patients died during their hospital stay.

CONCLUSIONS

Even though ACT is a widely used UFH monitoring tool in ECMO patients, our meta-analysis found a weak correlation between ACT and UFH infusion dose. New trials are needed to investigate the role of emerging tools and to clarify the most appropriate monitoring strategy for patients receiving ECMO support.

Outcomes of heparinized adult veno-arterial extracorporeal membrane oxygenation patients managed with low and high activated partial thromboplastin time targets: A systematic review and meta-analysis

INTRODUCTION

There are no randomized controlled trials comparing low and high activated partial thromboplastin time (aPTT) targets in heparinized adult veno-arterial (VA) extracorporeal membrane oxygenation (ECMO) patients. Our systematic review and meta-analysis summarized complication rates in adult VA ECMO patients treated with low and high aPTT targets.

METHODS

Studies published from January 2000 to May 2022 were identified using Pubmed, Embase, Cochrane Library, and LILACS (Latin American and Caribbean Health Sciences Literature). Studies were included if aPTT was primarily used to guide heparin anticoagulation. For the low aPTT group, we included studies where aPTT goal was ≤60 seconds and for the high aPTT group, we included studies where aPTT goal was ≥60 seconds. Proportional meta-analysis with a random effects model was used to calculate pooled complication rates for patients in the two aPTT groups.

RESULTS

Twelve studies met inclusion criteria (5 in the low aPTT group and 7 in the high aPTT group). The pooled bleeding complication incidence for low aPTT studies was 53.6% (95% CI = 37.4%-69.4%, I2 = 60.8%) and for high aPTT studies was 43.8% (95% CI = 21.7%-67.1%, I2 = 91.8%). No studies in the low aPTT group reported overall thrombosis incidence, while three studies in the high aPTT group reported overall thrombosis incidence. The pooled thrombosis incidence for high aPTT studies was 16.1% (95% CI = 9.0%-24.5%, I2 = 13.1%).

CONCLUSIONS

Adult ECMO patients managed with low and high aPTT goals appeared to have similar bleeding and other complication rates further highlighting the need for a randomized controlled trial.

Optimal Antithrombotic Strategies in Cardiogenic Shock

Cardiogenic shock (CS) represents a critical condition with a high mortality rate. The most common cause of CS is coronary artery disease, and patients typically present with myocardial infarction, necessitating immediate treatment through percutaneous coronary intervention (PCI) and often requiring mechanical circulatory support. CS is associated with a prothrombotic situation, while on the other hand, there is often a significant risk of bleeding. This dual challenge complicates the selection of an optimal antithrombotic strategy. The choice of antithrombotic agents must be personalized, taking into consideration all relevant conditions. Repeated risk assessment, therapeutic monitoring, and adjusting antithrombotic therapy are mandatory in these patients. This review article aims to provide an overview of the current evidence and practical guidance on antithrombotic strategies in the context of CS.

Factors Affecting the Discrepancy Between Coagulation Times on Extracorporeal Circulation Using Unfractionated Heparin in Children and Young Adults

In unfractionated heparin (UFH) monitoring during extracorporeal circulation, the traditional measures of activated clotting time (ACT) or activated partial thromboplastin time (APTT) may diverge, confounding anticoagulant adjustments. We aimed to explore the factors explaining this discrepancy in children and young adults. This retrospective observational study, conducted at an urban regional tertiary hospital, included consecutive pediatric patients who received UFH during extracorporeal circulation (continuous kidney replacement therapy or extracorporeal membrane oxygenation) between April 2017 and March 2021. After patients whose ACT and APTT were not measured simultaneously or who were also taking other anticoagulants were excluded, we analyzed 94 samples from 23 patients. To explain the discrepancy between ACT and APTT, regression equations were created using a generalized linear model (family  =  gamma, link  =  logarithmic) with ACT as the response variable. Other explanatory variables included age, platelet count, and antithrombin. Compared to APTT alone as an explanatory variable, the Akaike information criterion and pseudo-coefficient of determination improved from 855 to 625 and from 0.01 to 0.42, respectively, when these explanatory variables were used. In conclusion, we identified several factors that may explain some of the discrepancy between ACT and APTT in the routinely measured tests. Evaluation of these factors may aid in appropriate adjustments in anticoagulation therapy.

Comparison of anticoagulation monitoring strategies for adults supported on extracorporeal membrane oxygenation: A systematic review

BACKGROUND

Anticoagulation is critical in patients supported on extracorporeal membrane oxygenation (ECMO). The appropriate monitoring strategies for heparin remain unclear.

OBJECTIVES

This systematic review aimed to compare the accuracy and safety of various monitoring strategies for patients supported on ECMO.

METHODS

The PubMed and Web of Science databases were searched for articles in March 2023 without restrictions on publication date. Anticoagulation monitoring strategies for adults supported on ECMO were compared across all included studies. The incidence of bleeding, thrombosis, mortality, blood transfusion, correlation between tests and heparin dose, and the discordance between different tests were discussed in the included studies. The risk of bias was assessed using the Newcastle-Ottawa Scale and Cochrane Collaboration's tool.

RESULTS

Twenty-six studies, including a total of 1,684 patients, met the inclusion criteria. The monitoring of anticoagulation by activated partial thromboplastin time (aPTT) resulted in less blood product transfusion than that by activated clotting time (ACT). Moreover, the monitoring of anticoagulation by anti-factor Xa (Anti-Xa) resulted in a more stable anticoagulation than that by aPTT. Anti-Xa and aPTT correlated with heparin dose better than ACT, and the discordance between different monitoring tests was common. Finally, combined monitoring showed some advantages in reducing mortality and blood product transfusion.

CONCLUSION

Anti-Xa and aPTT are more suitable for anticoagulation monitoring for patients supported on ECMO than ACT. Thromboelastography and combination strategies are less applied. Most of the studies were retrospective, and their sample sizes were relatively small; thus, more appropriate monitoring strategies and higher quality research are needed.

An ex vivo comparison of partial thromboplastin time and activated clotting time for heparin anticoagulation in an ovine model

BACKGROUND

Sheep are a primary model of mechanical circulatory support (MCS) with heparin anticoagulation therapy frequently being monitored by activated clotting time (ACT) due to ease and cost. In patients undergoing long-term heparin therapy, other anticoagulation monitoring strategies, such as activated partial thromboplastin time (aPTT), have proven to be more reliable indicators for the adequacy of anticoagulation, frequently determined by heparin concentration. As there is a paucity of similar studies in sheep, we sought to investigate the correlation between heparin concentration and ACT and aPTT using whole sheep blood in an ex vivo model.

METHODS

Fresh whole blood was serially drawn from an adult female Dorset-hybrid sheep and aliquots were placed into tubes containing heparin saline solutions with concentrations ranging from 0 to 7.81 U heparin per mL of whole blood. ACT and aPTT values were measured on each of the samples. The experiment was performed four times with the same animal. A simple linear regression was performed to determine correlation, and subgroup analysis was performed on low versus high heparin concentrations typically seen in human patients on long-term MCS, such as extracorporeal membrane oxygenation (ECMO), versus cardiopulmonary bypass, respectively.

RESULTS

aPTT measurements versus the heparin concentration had an R²  = 0.7295. ACT measurements versus the heparin concentration had a R²  = 0.4628. aPTT measurements versus the ACT measurements had a R²  = 0.2974. The strength of the correlation between aPTT and heparin concentration increased at low heparin concentrations (R²  = 0.8392).

CONCLUSION

aPTT had a more reliable correlation to heparin concentration and thus anticoagulation level than ACT. This was particularly true at lower heparin concentrations, similar to ranges seen for patients on ECMO. The correlation between aPTT and ACT values was poor. Further in vivo studies should be performed to confirm our results.

SEDAR/SECCE ECMO management consensus document

ECMO is an extracorporeal cardiorespiratory support system whose use has been increased in the last decade. Respiratory failure, postcardiotomy shock, and lung or heart primary graft failure may require the use of cardiorespiratory mechanical assistance. In this scenario perioperative medical and surgical management is crucial. Despite the evolution of technology in the area of extracorporeal support, morbidity and mortality of these patients continues to be high, and therefore the indication as well as the ECMO removal should be established within a multidisciplinary team with expertise in the area. This consensus document aims to unify medical knowledge and provides recommendations based on both the recent bibliography and the main national ECMO implantation centres experience with the goal of improving comprehensive patient care.

Guidance for the Management of Patients with Vascular Disease or Cardiovascular Risk Factors and COVID-19: Position Paper from VAS-European Independent Foundation in Angiology/Vascular Medicine

COVID-19 is also manifested with hypercoagulability, pulmonary intravascular coagulation, microangiopathy, and venous thromboembolism (VTE) or arterial thrombosis. Predisposing risk factors to severe COVID-19 are male sex, underlying cardiovascular disease, or cardiovascular risk factors including noncontrolled diabetes mellitus or arterial hypertension, obesity, and advanced age. The VAS-European Independent Foundation in Angiology/Vascular Medicine draws attention to patients with vascular disease (VD) and presents an integral strategy for the management of patients with VD or cardiovascular risk factors (VD-CVR) and COVID-19. VAS recommends (1) a COVID-19-oriented primary health care network for patients with VD-CVR for identification of patients with VD-CVR in the community and patients' education for disease symptoms, use of eHealth technology, adherence to the antithrombotic and vascular regulating treatments, and (2) close medical follow-up for efficacious control of VD progression and prompt application of physical and social distancing measures in case of new epidemic waves. For patients with VD-CVR who receive home treatment for COVID-19, VAS recommends assessment for (1) disease worsening risk and prioritized hospitalization of those at high risk and (2) VTE risk assessment and thromboprophylaxis with rivaroxaban, betrixaban, or low-molecular-weight heparin (LMWH) for those at high risk. For hospitalized patients with VD-CVR and COVID-19, VAS recommends (1) routine thromboprophylaxis with weight-adjusted intermediate doses of LMWH (unless contraindication); (2) LMWH as the drug of choice over unfractionated heparin or direct oral anticoagulants for the treatment of VTE or hypercoagulability; (3) careful evaluation of the risk for disease worsening and prompt application of targeted antiviral or convalescence treatments; (4) monitoring of D-dimer for optimization of the antithrombotic treatment; and (5) evaluation of the risk of VTE before hospital discharge using the IMPROVE-D-dimer score and prolonged post-discharge thromboprophylaxis with rivaroxaban, betrixaban, or LMWH.