Challenges encountered with argatroban anticoagulation during cardiopulmonary bypass

Utility and safety of nafamostat mesilate for anticoagulation in dogs

BACKGROUND

Surgical interventions are recommended for cases of advanced mitral regurgitation, however, limited facilities are available. The most prominent complication in such procedures is heparin-derived bleeding. An alternative anticoagulant to heparin, nafamostat mesilate (NM), can reduce the occurrence of complications associated with heparin such as bleeding or shock.

OBJECTIVES

This study aimed to evaluate the utility and safety of using NM during anaesthesia in canines.

METHODS

Six healthy adult Beagle dogs were anaesthetised, and NM was administered intravenously as a 10 mg/kg bolus dose over 5 min, followed by a continuous infusion of 10 mg/kg/h over 20 min. Blood tests and blood pressure measurements were performed at 0, 5, 25 and 55 min after NM administration.

RESULTS

Activated thromboplastin times at 0, 25 and 55 min were 13.0 ± 0.7 s, 106.7 ± 13.3 s and 28.2 ± 2.9 s, respectively, with a significant difference between 0 and 25 min (p < 0.01) only. No significant differences were observed in prothrombin time, antithrombin, fibrinogen and fibrin degradation product concentrations between timepoints. Activated clotting times (ACTs) at 0, 5, 25 and 55 min were 119.5 ± 9.6 s, 826.7 ± 78.6 s, 924.8 ± 42.4 s and 165.2 ± 13.5 s, respectively. Significant differences were observed between 0 and 5 min (p < 0.05) and between 0 and 25 min (p < 0.05). Blood pressure changes occurred in four dogs (66.7%). No other serious adverse effects were observed.

CONCLUSIONS

ACT results indicated that NM use in anaesthetised healthy dogs was sufficient to obtain procedural anticoagulation with minimal adverse effects. However, these preliminary data require validation in further studies on cardiopulmonary bypass surgery.

Heparin Insensitivity and Thrombotic Risk Associated With Sequential Uses of Prothrombin Complex Concentrate and Andexanet Alfa for Apixaban Reversal During Acute Type A Aortic Dissection Repair: A Case Report

The management of patients on direct oral anticoagulants (DOACs) who require emergent cardiac surgery is slowly evolving. The introduction of andexanet alfa, a novel antidote for apixaban and rivaroxaban, added a specific reversal agent to our armamentarium, but its safety and efficacy are still being investigated. We report 2 patients on DOAC treatment who required emergency cardiac surgery. Both received perioperative andexanet alfa together with prothrombin complex concentrate (PCC) at some time during 6 hours before operative management. Heparin resistance was noted in each instance, and pump thrombosis developed in 1 case.

Anticoagulation with Argatroban in a Patient with Heparin-Induced Thrombocytopenia and Renal Insufficiency Undergoing Orthotopic Heart Transplantation

Unfractionated heparin is the anticoagulant of choice for cardiac surgery that requires cardiopulmonary bypass. However, it can cause serious side effects like heparin-induced thrombocytopenia (HIT), an immune-mediated process where antibodies are directed against heparin and platelet 4 complexes. In such cases, alternative pharmacologic strategies are implemented to facilitate safe bypass conditions. A woman with severe decompensated heart failure was heparinized for intra-aortic balloon pump and subsequent LVAD placement. On day 6, a fall in platelets from 113,000 to 26,000 was noted. She was diagnosed with HIT. Heparin was discontinued and replaced with an argatroban infusion for the duration of her care until heart transplantation was completed. We review the mechanism, diagnosis, and complications of HIT. We discuss cardiopulmonary bypass and its relation to heparin, HIT, and heparin alternatives. We discuss argatroban's relevant pharmacology, clinical use, advantages, and disadvantages.

High-Dose Dabigatran Is an Effective Anticoagulant for Simulated Cardiopulmonary Bypass Using Human Blood

BACKGROUND

Currently no ideal alternative exists for heparin for cardiopulmonary bypass (CPB). Dabigatran is a direct thrombin inhibitor for which a reversal agent exists. The primary end point of the study was to explore whether Dabigatran was an effective anticoagulant for 120 minutes of simulated CPB.

METHODS

The study was designed in 2 sequential steps. Throughout, human blood from healthy donors was used for each experimental step. Initially, increasing concentrations of Dabigatran were added to aliquots of fresh whole blood, and the anticoagulant effect measured using kaolin/tissue factor-activated thromboelastography (rapidTEG). The dynamics of all thromboelastography (TEG) measurements were studied with repeated measures analysis of variance (ANOVA). Based on these data, aliquots of blood were treated with high-concentration Dabigatran and placed in a Chandler loop as a simple ex vivo bypass model to assess whether Dabigatran had sufficient anticoagulant effects to maintain blood fluidity for 2 hours of continuous contact with the artificial surface of the PVC tubing. Idarucizumab, humanized monoclonal antibody fragment, was used to verify the reversibility of Dabigatran effects. Finally, 3 doses of Dabigatran were tested in a simulated CPB setup using a heart-lung machine and a commercially available bypass circuit with an arteriovenous (A-V) loop. The primary outcome was the successful completion of 120 minutes of simulated CPB with dabigatran anticoagulation, defined as lack of visible thrombus. Thromboelastographic reaction (R) time was measured repeatedly in each bypass simulation, and the circuits were continuously observed for clot. Scanning Electron Microscopy (SEM) was used to visualize fibrin formation in the filters meshes during CPB.

RESULTS

In in vitro blood samples, Dabigatran prolonged R time and reduced the dynamics of clot propagation (as measured by speed of clot formation [Angle], maximum rate of thrombus generation [MRTG], and time to maximum rate of thrombus generation [TMRTG]) in a dose-dependent manner. In the Chandler Loop, high doses of Dabigatran prevented clot formation for 120 minutes, but only at doses higher than expected. Idarucizumab decreased R time and reversed anticoagulation in both in vitro and Chandler Loops settings. In the A-V loop bypass simulation, Dabigatran prevented gross thrombus generation for 120 minutes of simulated CPB.

CONCLUSIONS

Using sequential experimental approaches, we showed that direct thrombin inhibitor Dabigatran in high doses maintained anticoagulation of blood for simulated CPB. Idarucizumab reduced time for clot formation reversing the anticoagulation action of Dabigatran.

Quantitative and Qualitative Platelet Derangements in Cardiac Surgery and Extracorporeal Life Support

Thrombocytopenia and impaired platelet function are known as intrinsic drawbacks of cardiac surgery and extracorporeal life supports (ECLS). A number of different factors influence platelet count and function including the inflammatory response to a cardiopulmonary bypass (CPB) or to ECLS, hemodilution, hypothermia, mechanical damage and preoperative treatment with platelet-inhibiting agents. Moreover, although underestimated, heparin-induced thrombocytopenia is still a hiccup in the perioperative management of cardiac surgical and, above all, ECLS patients. Moreover, recent investigations have highlighted how platelet disorders also affect patients undergoing biological prosthesis implantation. Though many hypotheses have been suggested, the mechanism underlying thrombocytopenia and platelet disorders is still to be cleared. This narrative review aims to offer clinicians a summary of their major causes in the cardiac surgery setting.

Lung transplantation using argatroban in severe heparin-induced thrombocytopenia during extracorporeal membrane oxygenation: a case series

Lung transplantation during heparin-induced thrombocytopenia (HIT) is controversial and often considered a contraindication because of the risk of increased bleeding and thrombosis in the recipient. Although lung transplantation offers the best chance for cure in end-stage lung disease, the outcome after transplantation is still controversial in patients with HIT. In our center, two patients developed HIT type II during venovenous extracorporeal membrane oxygenation (ECMO) support for acute respiratory failure. They underwent successful lung transplantation using argatroban. The subsequent clinical course was uneventful except evacuation of post-operative hematoma in 1 patient, and they were discharged. Argatroban was successfully used during lung transplant surgery in patients who developed HIT type II during ECMO support. Further studies on the feasibility and safety of lung transplantation using a direct thrombin inhibitor in patients with HIT during ECMO are required.

A 24-hour perioperative case study on argatroban use for left ventricle assist device insertion during cardiopulmonary bypass and veno-arterial extracorporeal membrane oxygenation

A 44-year-old male with ongoing chest pain and left ventricular ejection fraction <20% was transferred from a peripheral hospital with intra-aortic balloon pump placement following a non-ST-elevation myocardial infarction (STEMI). The patient underwent emergent multi-vessel coronary artery bypass grafting requiring veno-arterial (VA) extracorporeal membrane oxygenation (ECMO) on post-operative day (POD)#9 secondary to cardiogenic shock with biventricular failure. Due to clot formation, an oxygenator change-out was necessary shortly after initiation. Following a positive heparin-induced thrombocytopenia (HIT) assay, a total circuit exchange was required to eliminate all heparin coating and argatroban was deemed the anticoagulant of choice due to acute kidney injury. On POD#24, the decision was made to implant a left ventricle assist device (LVAD) as a bridge to heart transplantation. There was difficulty achieving an activated clotting time (ACT) >400 s: multiple argatroban bolus doses were required, along with accelerated up-titration of infusion dosing. Despite maintaining an ACT >484 s, clot formation was observed in the cardiotomy reservoir prior to separation. Subsequently, the patient developed severe disseminated intravascular coagulopathy, with both intra-cardiac and intravascular thrombi, requiring massive transfusion and continuous cell saving due to severe hemorrhage post cardiopulmonary bypass (CPB). The patient received a total of 105 units of plasma, 74 units of packed red cells, 19 units of platelets, 13 bottles of 5% albumin, 6 units of cryoprecipitate and 2 doses of factor VIIa intraoperatively over the course of 24 hours. A total of 19.7 L of washed red blood cells were returned to the patient from the cell saver. With the LVAD in place, the patient developed transfusion-related acute lung injury and acute respiratory distress syndrome with right ventricular dysfunction requiring VA ECMO once again. On POD#30, ECMO was discontinued and the patient was discharged from the intensive care unit (ICU) on POD 66. After a very complex post-operative stay with numerous surgeries and extensive rehabilitation, the patient was discharged home with the LVAD on POD#112.

STS/SCA/AmSECT Clinical Practice Guidelines: Anticoagulation during Cardiopulmonary Bypass

Despite more than a half century of "safe" cardiopulmonary bypass (CPB), the evidence base surrounding the conduct of anticoagulation for CPB has not been organized into a succinct guideline. For this and other reasons, there is enormous practice variability relating to the use and dosing of heparin, monitoring heparin anticoagulation, reversal of anticoagulation, and the use of alternative anticoagulants. To address this and other gaps, the Society of Thoracic Surgeons (STS), the Society of Cardiovascular Anesthesiologists (SCA), and the American Society of Extracorporeal Technology (AmSECT) developed an Evidence Based Workgroup. This was a group of interdisciplinary professionals gathered together to summarize the evidence and create practice recommendations for various aspects of CPB. To date, anticoagulation practices in CPB have not been standardized in accordance with the evidence base. This clinical practice guideline was written with the intent to fill the evidence gap and to establish best practices in anticoagulation for CPB using the available evidence. To identify relevant evidence a systematic review was outlined and literature searches were conducted in PubMed® using standardized MeSH terms from the National Library of Medicine list of search terms. Search dates were inclusive of January 2000 to December 2015. The search yielded 833 abstracts which were reviewed by two independent reviewers. Once accepted into the full manuscript review stage, two members of the writing group evaluated each of 286 full papers for inclusion eligibility into the guideline document. Ninety-six manuscripts were included in the final review. In addition, 17 manuscripts published prior to 2000 were included to provide method, context, or additional supporting evidence for the recommendations as these papers were considered sentinel publications. Members of the writing group wrote and developed recommendations based on review of the articles obtained and achieved more than two thirds agreement on each recommendation. The quality of information for a given recommendation allowed assessment of the level of evidence as recommended by the AHA/ACCF Task Force on Practice Guidelines. Recommendations were written in the three following areas 1) Heparin dosing and monitoring for initiation and maintenance of CPB, 2) Heparin contraindications and heparin alternatives, 3) Reversal of anticoagulation during cardiac operations. It is hoped that this guideline will serve as a resource and will stimulate investigators to conduct more research and expand upon the evidence base on the topic of anticoagulation for CPB.

Heparin-induced thrombocytopenia in cardiac surgery and critically ill patients

Thrombocytopenia as well as anti-platelet factor 4/heparin (PF4/H) antibodies are common in cardiac surgery patients and those treated in the intensive care unit. In contrast, heparin-induced thrombocytopenia (HIT) is uncommon in these populations (∼1 % and ∼0.5 %, respectively). A stepwise approach where testing for anti-PF4/H antibodies is performed only in patients with typical clinical symptoms of HIT improves diagnostic specificity of the laboratory assays without losing sensitivity, thereby helping to avoid overdiagnosis and resulting HIT overtreatment. Short-term re-exposure to heparin, especially given intraoperatively for cardiovascular surgery, is a reasonable therapeutic option in patients with a history of HIT who subsequently test negative for HIT antibodies. Organ failure(s), enhanced bleeding risks, and other characteristics require special considerations regarding non-heparin anticoagulation: Argatroban is the alternative anticoagulant with pharmacokinetics independent of renal function, but it has a prolonged half-life in case of impaired liver function. For bivalirudin, protocols during cardiopulmonary bypass surgery are established, and it is suitable for patients with liver insufficiency. A major issue of direct thrombin inhibitors are false high activated partial thromboplastin time values in patients with comorbidities affecting prothrombin, which can result in systematic underdosing of the drugs. This is not the case for danaparoid and fondaparinux, which can be monitored by anti-factor Xa assays, but have long half-lives and no suitable antidote. This review includes also information on management of on- and off-pump cardiac surgery, ventricular assist devices, percutaneous interventions, continuous renal replacement therapy, and extracorporeal membrane oxygenation in patients with HIT.

An Anti-Coagulation Conundrum: Implantation of Total Artificial Heart in a Patient with Heparin-Induced Thrombocytopenia Type II

BACKGROUND Heparin-induced thrombocytopenia (HIT) is a rare but life-threatening complication of heparin administration. It can present a major clinical dilemma for physicians caring for patients requiring life-saving urgent or emergent cardiac surgery. Studies have been published examining the use of alternative anticoagulants for patients undergoing cardiopulmonary bypass (CPB), however, evidence does not clearly support any particular approach. Presently, there are no large-scale, prospective randomized studies examining the impact of alternative anticoagulants on clinical outcomes for HIT-positive patients requiring cardiac surgery. CASE REPORT We present the case of a patient who underwent SynCardia Total Artificial Heart (TAH) implantation following a recent left ventricular assist device (LVAD) placement. The patient was receiving argatroban for type II HIT with anuric renal failure, and developed a thrombus which occluded the inflow cannula of the LVAD. Based on a published study and after establishing consensus with the surgical, anesthesiology, perfusion, and hematology teams, we decided to use tirofiban as an antiplatelet agent to inhibit the platelet aggregation induced by heparin, and ultimately used heparin as the anticoagulant for cardiopulmonary bypass. CONCLUSIONS When selecting anticoagulation for a HIT-positive patient requiring CPB, so that benefits outweigh risks, it is of paramount importance that the decision be based on a multitude of factors. The team caring for the patient should have a shared mental model and be familiar with the pharmacology, devices used, and local practices. These three elements should be integrated with patient-specific comorbidities along with local monitoring capabilities to ensure safe, efficient patient care.

Cardiopulmonary Bypass Without Heparin

Due to familiarity, short half-life, ease of monitoring, and the availability of a reversal agent, heparin remains the anticoagulant of choice for cardiac operations requiring cardiopulmonary bypass (CPB). However, occasionally patients require CPB but should not receive heparin, most often because of acute or subacute heparin-induced thrombocytopenia (HIT). In these cases, if it is not feasible to wait for the disappearance of HIT antibodies, an alternative anticoagulant must be selected. A number of non-heparin anticoagulant options have been explored. However, current recommendations suggest the use of a direct thrombin inhibitor such as bivalirudin. This review describes the use of heparin alternatives for the conduct of CPB with a focus on the direct thrombin inhibitors.

Challenging Argatroban Management of a Child on Extracorporeal Support and Subsequent Heart Transplant

A 6-year-old child developed heparin-induced thrombocytopenia while on extracorporeal life support. Hours after a difficult transition from heparin to argatroban for anticoagulation therapy, the child underwent heart transplantation. Intraoperative management was plagued with circuit thrombus formation while on cardiopulmonary bypass and subsequent massive hemorrhage after bypass. We review the child’s anticoagulation management, clinical challenges encountered, and review current literature related to the use of argatroban in pediatric cardiac surgery.