Bivalirudin for Pediatric Procedural Anticoagulation

Bivalirudin anticoagulation for cardiopulmonary bypass during cardiac surgery

INTRODUCTION

Heparin is the primary anticoagulant for cardiopulmonary bypass (CPB) support during cardiac surgery. While widely used, ∼2% of cardiac surgery patients develop heparin-induced thrombocytopenia (HIT) and 4-26% develop heparin resistance. Bivalirudin is an alternative anticoagulant mainly used for percutaneous coronary interventions. Given the challenges associated with heparin anticoagulation, we conducted a review to explore the use of bivalirudin for CPB surgery.

METHODS

PubMed and Embase scoping review included 2 randomized controlled trials, a retrospective comparison study, 3 pilot studies, and 30 case reports. To provide a contemporary series, we searched for articles published from 2010 to 2023. Our review included studies from both adult and pediatric populations.

RESULTS

While data is limited, bivalirudin seems to supply similar effectiveness and safety as heparin for CPB anticoagulation. Across the three comparative studies, the heparin cohorts had a 0-9% mortality rate and 0-27% rate of major bleeding/reoperation compared to a 0-3% mortality and 0-6% major bleeding/reoperation rate for the bivalirudin cohorts. Bivalirudin was successfully used as an anticoagulant in a wide range of CPB surgeries (e.g., heart transplants, ventricular assisted device placements, and valve repairs). Successful patient outcomes were reported with bivalirudin infusion of ∼2 mg/kg/hour, activated clotting time monitoring (target >400 s or 2.5× baseline), use of cardiotomy suctions, minimization of stagnant blood, and post-bypass modified ultrafiltration.

CONCLUSION

Bivalirudin is a safe and effective anticoagulant for CPB, especially for patients with HIT or heparin resistance. Further comparative research is called for to optimize bivalirudin utilization for CPB during cardiac surgery.

Bivalirudin as an anticoagulation strategy for acute hemodialysis in children: Two cases with a summary of recent literature

Unfractionated heparin is the most used anticoagulative agent for extracorporeal settings in children, including acute hemodialysis modalities. In certain situations, such as heparin-induced thrombocytopenia, alternatives must be applied. The direct thrombin inhibitor bivalirudin has come forth as an attractive substitute. Bivalirudin is currently only approved for adult use in specific percutaneous coronary intervention settings. However, it has a growing off-label popularity in different contexts for both adult and pediatric patients. Experience with bivalirudin in children is mainly limited to extracorporeal membrane oxygenation, ventricular assist devices and during cardiopulmonary bypass surgery. Literature about its use as anticoagulation strategy for pediatric hemodialysis is very scarce. Here, we present two pediatric cases where bivalirudin was used during acute hemodialysis, followed by a short summary of recent literature.

Bivalirudin Monitoring in Pediatric Ventricular Assist Device and Extracorporeal Membrane Oxygenation: Analysis of Single-Center Retrospective Cohort Data 2018-2022

OBJECTIVES

The activated partial thromboplastin time (aPTT) is the most frequently used monitoring assay for bivalirudin in children and young adults on mechanical circulatory support including ventricular assist devices (VADs) and extracorporeal membrane oxygenation (ECMO). However, intrinsic variability of the aPTT complicates management and risks bleeding or thrombotic complications. We evaluated the utility and reliability of a bivalirudin-calibrated dilute thrombin time (Bival dTT) assay for bivalirudin monitoring in this population.

DESIGN

Retrospective analysis of clinical data (including aPTT, dilute thrombin time [dTT]) and results of residual plasma samples from VAD patients were assessed in two drug-calibrated experimental assays. One assay (Bival dTT) was validated for clinical use in VAD patients, and subsequently used by clinicians in ECMO patients. Pearson correlation and simple linear regression were used to determine R2 correlation coefficients between the different laboratory parameters using Statistical Package for Social Sciences (Armonk, NY).

SETTING

ICUs at Cincinnati Children's Hospital Medical Center.

SUBJECTS

Children on VAD or ECMO support anticoagulated with bivalirudin.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred fifteen plasma samples from 11 VAD patients were analyzed. Both drug-calibrated experimental assays (anti-IIa and Bival dTT) showed excellent correlation with each other ( R2 = 0.94) and with the dTT ( R2 = 0.87), but poor correlation with aPTT ( R2 = 0.1). Bival dTT was selected for validation in VAD patients. Subsequently, clinically ordered results (105) from 11 ECMO patients demonstrated excellent correlation between the Bival dTT and the standard dTT ( R2 = 0.86) but very poor correlation with aPTT ( R2 = 0.004).

CONCLUSIONS

APTT is unreliable and correlates poorly with bivalirudin's anticoagulant effect in ECMO and VAD patients. A drug-calibrated Bival dTT offers superior reliability and opportunity to standardize results across institutions. Additional studies are needed to determine an appropriate therapeutic range and correlation with clinical outcomes.

Effect of bivalirudin on coagulation in neonatal (cord) and adult human blood in vitro

INTRODUCTION

Bivalirudin is recommended as an alternative to heparin in cardiac surgery with cardiopulmonary bypass. Although it has been used in infants and children for this indication, there is a paucity of data on the pharmacologic effects of bivalirudin in neonates. Given the immaturity of the hemostatic system in neonates, we hypothesized that coagulation responses to bivalirudin in this population would be different than in adults.

METHODS

Blood samples were drawn from placenta-cord units and from healthy adult donors. The study was carried out in two steps. First, bivalirudin was added to cord and adult blood samples at concentrations of 0, 5, 10, 15, and 20 μg/mL. Activated clotting time and thromboelastographic variables were recorded. Next, we used a Chandler loop system to assess the efficacy of bivalirudin in a simple model of cardiopulmonary bypass. The loops were primed with cord or adult blood and were run until thrombus was detected. Plasma bivalirudin concentrations were measured at 1, 15, 30, 45, 60, and 75 min after initiating rotation of the loops using liquid chromatography/mass spectrometry.

RESULTS

Bivalirudin elicited a dose-dependent prolongation inhibition of coagulation in both cord and adult blood samples with greater potency in cord blood in comparison to adult blood (activated clotting time: 627 ± 50 vs. 452 ± 22 s at 15 μg/mL bivalirudin, p < .0001). This relative potency was also demonstrated in the Chandler loop system, but interestingly, cord blood appeared to inactivate bivalirudin more rapidly than adult blood with earlier clotting in loops containing cord blood.

CONCLUSIONS

This study demonstrates that bivalirudin has greater potency in cord blood in vitro than in adult blood. Plasma degradation appears to proceed more rapidly in cord blood than in adults. Both of these findings should be considered when planning dosing regimens in neonatal patients.

Impact of inflammation and steroids on anti-coagulation in children supported on a ventricular assist device

Critically ill pediatric patients supported on ventricular assist devices (VADs) are increasingly being anticoagulated on bivalirudin, but with difficulty monitoring anticoagulation. Activated partial thromboplastin time (aPTT) has recently been shown to poorly correlate with bivalirudin plasma concentrations, while dTT had excellent correlation. However, aPTT is the more common monitoring test and dTT testing is rarely used. In addition, effects of frequent clinical VAD scenarios (such as inflammation) on the accuracy of aPTT and dTT testing remains uncertain. We reviewed the effects of clinical scenarios (infection/inflammation, chylothorax, and steroids administration) on anticoagulation monitoring in 10 pediatric VAD patients less than 3 years at Cincinnati Children's Hospital Medical Center from 10/27/2020 to 5/6/2022 using bivalirudin for anticoagulation. There were 16 inflammation/infection, 3 chylothorax, and 6 steroids events. Correlation between dTT and aPTT was significantly lower after infection/inflammation, with dTT increasing prior to inflammation/infection while aPTT remained unchanged. In addition, steroids are administered to VAD patients to reduce inflammation and thus additionally stabilize anticoagulation. However, this anticoagulation stabilization effect was reflected more accurately by dTT compared to aPTT. In children requiring VAD support utilizing bivalirudin anticoagulation, inflammation/infection is a common occurrence resulting in anticoagulation changes that may be more accurately reflected by dTT as opposed to aPTT.

Hirudin in the Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) is a common public health concern. The global burden of CKD is increasing due to the high morbidity and mortality associated with it, indicating the shortcomings of therapeutic drugs at present. Renal fibrosis is the common pathology of CKD, which is characterized by glomerulosclerosis, renal tubular atrophy, and renal interstitial fibrosis. Natural hirudin is an active ingredient extracted from Hirudo medicinalis, which has been found to be the strongest natural specific inhibitor of thrombin. Evidence based on pharmacological data has shown that hirudin has important protective effects in CKD against diabetic nephrology, nephrotic syndrome, and renal interstitial fibrosis. The mechanisms of hirudin in treating CKD are mainly related to inhibiting the inflammatory response, preventing apoptosis of intrinsic renal cells, and inhibiting the interactions between thrombin and protease-activated receptors. In this review, we summarize the function and beneficial properties of hirudin for the treatment of CKD, and its underlying mechanisms.

Bivalirudin exerts antiviral activity against respiratory syncytial virus-induced lung infections in neonatal mice

Respiratory syncytial virus (RSV) is the most common cause of small airways inflammation in the lungs (bronchiolitis) in neonates and immunocompromised adults. The deregulation of cellular and plasma components leads to increased morbidity and mortality. The activation of the clotting cascade plays a key role in the progression of disease severity during viral infection. The current investigation studied the effect of bivalirudin (BR) on the progression and cellular effects of RSV-induced infection in the neonatal mice model. Mice (5-7 days old) were inoculated intranasally with RSV with or without BR administration (2 mg kg^-1 day^-1, i.v.) for 2 weeks. Tissue histopathology, inflammatory signalling genes such as TLR, and cytokines were analyzed. The results showed pneumocytes exhibiting nuclear pyknosis, cellular infiltration in lung tissue and increased lung titers in RSV-infected mice compared to the control. Furthermore, RSV-infected mice demonstrated altered clotting parameters such as D-dimer, soluble thrombomodulin, and increased inflammatory cytokines IL-5, 6, IFN-γ, IL-13, and CXCL1. Additionally, the mRNA expression analysis displayed increased levels of IL-33, TLR3, and TLR7 genes in RSV-infected lung tissue. Further, to delineate the role of micro RNAs, the qRT-PCR analysis was done, and the results displayed an increase in miR-136, miR-30b, and let-7i. At the same time, the down-regulated expression of miR-221 in RSV-infected mice compared to the control. BR treatment reduced the cellular infiltration with reduced inflammatory cytokines and normalized clotting indices. Thus, the study shows that RSV infection induces specific changes in lung tissue and the clotting related signalling mechanism. Additionally, BR treatment significantly reduces bronchiolitis and prevents the severity of the infections suggesting that BR can possibly be used to reduce the viral-mediated infections in neonates.

Thrombosis Prevention and Anticoagulation Management in the Pediatric Patient with Congenital Heart Disease

Thrombosis is one of the most frequent complications affecting children with congenital heart disease (CHD). Palliative and reparative cardiac surgeries are some of the main players contributing to the thrombosis risk in this patient population. Additional risk factors related to the CHD itself (e.g., cardiac dysfunction, arrhythmias, and polycythemia in cyanotic cardiac disorders) can contribute to thrombogenicity alone or combined with other factors. Thrombotic complications have been recognized as a significant cause of morbidity and mortality in this patient population. Here, we provide an overview of the pathophysiology and risk factors for thrombosis as well as the indications for and use of different anticoagulation, antiplatelet, and thrombolytic agents. In addition, we describe some of most common thrombotic complications and their management in the pediatric CHD population.

Dose estimation for bivalirudin during pediatric cardiopulmonary bypass

AIM

A typical adult-based bivalirudin regimen during cardiopulmonary bypass uses a loading dose of 1 mg kg^-1 and a circuit prime (volume L × 13 mg) with a subsequent intravenous infusion 2.5 mg h^-1  kg^-1 . Dose in children remains unknown. We wished to determine a practical bivalirudin dosing schedule for children undergoing surgery with cardiopulmonary bypass.

METHODS

Published pharmacokinetic parameters in children who were anticoagulated for cardiac catheterization using bivalirudin were compared to adult by scaling for size using allometry. An infusion regimen suitable for children was determined using a bivalirudin target concentration (13 mg L^-1 ) common in adults for effect during cardiopulmonary bypass. Predicted bivalirudin infusion rates in children were compared to regimens published as case reports.

RESULTS

Current pediatric bivalirudin infusion rates are based on those used in adults with titration during cardiopulmonary bypass to achieve activated clotting times longer than 400 s. Bivalirudin clearance (mL min^-1  kg^-1 ) can be estimated in children by scaling adult parameters using allometry. Clearance decreases through childhood and higher infusion rates in children would achieve target concentration rapidly without the need to titrate initial infusion rate. An infusion rate of 4.5 mg h^-1  kg^-1 in a 10 kg infant, 4 mg h^-1  kg^-1 in a 20 kg child and 3.5 mg h^-1  kg^-1 in a child 30-40 kg will target an activated clotting time slower than 400 s. Adult regimens could be used in those children heavier than 50 kg.

CONCLUSION

Bivalirudin infusion in children should be started after loading dose at rates greater than those used in adults. Dose in neonates remains uncertain because neither pharmacokinetics nor coagulation pharmacodynamics have been adequately characterized.

Extracorporeal Life Support Organization (ELSO): Guidelines for Pediatric Cardiac Failure

These guidelines are applicable to neonates and children with cardiac failure as indication for extracorporeal life support. These guidelines address patient selection, management during extracorporeal membrane oxygenation, and pathways for weaning support or bridging to other therapies. Equally important issues, such as personnel, training, credentialing, resources, follow-up, reporting, and quality assurance, are addressed in other Extracorporeal Life Support Organization documents or are center-specific.

Hemostatic Challenges in Pediatric Critical Care Medicine-Hemostatic Balance in VAD

Ventricular assist devices (VAD) are used more in children. Safe and effective anticoagulation is required for successful management of children supported with ventricular assist devices. Developmental hemostasis, device hemocompatibility, plastic to body ratio, surgical variable techniques, lack of knowledge on pharmacokinetics of anticoagulants, and wide variability in anticoagulation protocols have all contributed to increased incidence of bleeding and thromboembolic complications. New collaborative learning networks, such as the ACTION network, provide opportunities to define best practices, optimize, and reduce anticoagulation related adverse events. ACTION was established Dec 2017. It consists of expert clinicians in heart failure, as well as researchers, parents, and patients, with goals to improve outcomes, share data, improve education and standard practice for children with heart failure (, n.d). Changes in pediatric VAD anticoagulation strategy from using mainly heparin to DTI such as bivalirudin have helped reduce bleeding and clotting complications.

The Use of Bivalirudin in Pediatric Cardiac Surgery and in the Interventional Cardiology Suite

Anticoagulation is an essential component for patients undergoing cardiopulmonary bypass or extracorporeal membrane oxygenation and for those with ventricular assist devices. However, thrombosis and bleeding are common complications. Heparin continues to be the agent of choice for most patients, likely owing to practitioners' comfort and experience and the ease with which the drug's effects can be reversed. However, especially in pediatric cardiac surgery, there is increasing interest in using bivalirudin as the primary anticoagulant. This drug circumvents certain problems with heparin administration, such as heparin resistance and heparin-induced thrombocytopenia, but it comes with additional challenges. In this manuscript, the authors review the literature on the emerging role of bivalirudin in pediatric cardiac surgery, including its use with cardiopulmonary bypass surgery, extracorporeal membrane oxygenation, ventricular assist devices, and interventional cardiology. Moreover, they provide an overview of bivalirudin's pharmacodynamics and monitoring methods.

Updates in Pediatric Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation is an increasingly used mode of life support for patients with cardiac and/or respiratory failure refractory to conventional therapy. This review provides a synopsis of the evolution of extracorporeal life support in neonates, infants, and children and offers a framework for areas in need of research. Specific aspects addressed are the changing epidemiology; technologic advancements in extracorporeal membrane oxygenation circuitry; the current status and future direction of anticoagulation management; sedative and analgesic strategies; and outcomes, with special attention to the lessons learned from neonatal survivors.

Use of bivalirudin as a primary anticoagulant in a child during Berlin Heart EXCOR ventricular assist device support

We describe our experience of bivalirudin use, a newer direct thrombin inhibitor, in an infant who was supported with Berlin Heart EXCOR VAD (Berlin VAD) as bridge to transplant for 122 days without complications and without need for pump exchange. An 11-month-old girl with dilated cardiomyopathy with acute heart failure was awaiting cardiac transplant. Lack of improvement despite maximizing medical therapy and anticipating a prolonged waitlist time, she was supported with Berlin LVAD as a bridge to transplant. Anticoagulation with bivalirudin was started and titrated with a goal partial thromboplastin time of 60-90 seconds. Therapeutic anticoagulation was achieved with bivalirudin for 50% of the days (61/122 days) on a dose of 2.1 mg/kg/hour and in a narrow dose range of 1.9 to 2.3 mg/kg/hour for 80% of the days (98/122 days). Antiplatelet regimen was started initially with aspirin and clopidogrel added later. She was supported for 122 days on a single pump without any evidence of thrombus or need for pump change. Berlin VAD explant and orthotopic heart transplant with biatrial anastomosis were performed uneventfully. Explanted Berlin VAD had no evidence of clot/fibrin or thrombus formation. The child was discharged to home uneventfully 15 days after cardiac transplant.