Stabilized Infective Endocarditis and Altered Heparin Responsiveness During Cardiopulmonary Bypass

Finding a common definition of heparin resistance in adult cardiac surgery: communication from the ISTH SSC subcommittee on perioperative and critical care thrombosis and hemostasis

Ensuring adequate anticoagulation for patients requiring cardiac surgery and cardiopulmonary bypass (CPB) is important due to the adverse consequences of inadequate anticoagulation with respect to bleeding and thrombosis. When target anticoagulation is not achieved with typical doses, the term heparin resistance is routinely used despite the lack of uniform diagnostic criteria. Prior reports and guidance documents that define heparin resistance in patients requiring CPB and guidance documents remain variable based on the lack of standardized criteria. As a result, we conducted a review of clinical trials and reports to evaluate the various heparin resistance definitions employed in this clinical setting and to identify potential standards for future clinical trials and clinical management. In addition, we also aimed to characterize the differences in the reported incidence of heparin resistance in the adult cardiac surgical literature based on the variability of both target-activated clotting (ACT) values and unfractionated heparin doses. Our findings suggest that the most extensively reported ACT target for CPB is 480 seconds or higher. Although most publications define heparin resistance as a failure to achieve this target after a weight-based dose of either 400 U/kg or 500 U/kg of heparin, a standardized definition would be useful to guide future clinical trials and help improve clinical management. We propose the inability to obtain an ACT target for CPB of 480 seconds or more after 500 U/kg as a standardized definition for heparin resistance in this setting.

Patients with infective endocarditis undergoing cardiac surgery have distinct ROTEM profiles and more bleeding complications compared to patients without infective endocarditis

BACKGROUND

The coagulation system is crucial in the pathogenesis of infective endocarditis and undergoes significant changes during course of the disease. However, little is known about the implications of those changes in the perioperative period. Aim of the present study was to delineate the specific coagulation patterns and their clinical consequence in patients undergoing cardiac surgery due to infective endocarditis.

METHODS

In this single-centre, exploratory, prospective observational study, we investigated the incidence and degree of coagulopathy in patients with (n = 31) and without infective endocarditis (n = 39) undergoing cardiac valve surgery. The primary outcome was the differences between these two groups in rotational thromboelastometry (ROTEM) results before, during and after surgery. The secondary outcomes were the differences between the groups in heparin sensitivity, bleeding complications, and transfusion requirements.

RESULTS

Most ROTEM parameters in EXTEM, INTEM and FIBTEM assays were significantly altered in patients with infective endocarditis. Clotting time in the EXTEM assay was significantly prolonged in the endocarditis group at all time-points, while all clot firmness parameters (A5, A10 and MCF) were significantly increased. The heparin sensitivity index was significantly lower in the endocarditis group (median index 0.99 vs 1.17s. IU-1.kg-1, p = .008), indicating increased heparin resistance. Patients with infective endocarditis had more bleeding complications as assessed by the universal definition of perioperative bleeding score (OR 3.0, p = .018), and more patients with endocarditis underwent early re-exploration (p = .018).

CONCLUSIONS

The findings of this exploratory investigation show significantly altered coagulation profiles in patients with infective endocarditis, with concomitant hyper- and hypocoagulability. Furthermore, the incidence of bleeding complications and transfusion requirements were increased in patients with endocarditis. These results show the potential of ROTEM to detect coagulation abnormalities in patients with infective endocarditis. Existing point-of-care coagulation testing guided algorithms for optimizing perioperative coagulation management possibly need to be adjusted for these high-risk patients undergoing cardiac surgery.

Heparin Resistance During Cardiopulmonary Bypass in Adult Cardiac Surgery

The use of heparin for anticoagulation has changed the face of cardiac surgery by allowing a bloodless and motionless surgical field throughout the introduction of cardiopulmonary bypass (CPB). However, heparin is a drug with complex pharmacologic properties that can cause significant interpatient differences in terms of responsiveness. Heparin resistance during CPB is a weighty issue due to the catastrophic consequences stemming from inadequate anticoagulation, and the treatment of it necessitates a rationalized stepwise approach due to the multifactorial contributions toward this entity. The widespread use of activated clotting time (ACT) as a measurement of anticoagulation during CPB is examined, as it may be a false indicator of heparin resistance. Heparin resistance also has been repeatedly reported in patients infected with COVID-19, which deserves further exploration in this pandemic era. This review aims to examine the variability in heparin potency, underlying mechanisms, and limitations of using ACT for monitoring, as well as provide a framework towards the current management of heparin resistance.

Anesthesia Considerations in Infective Endocarditis

The management of infective endocarditis is complex and inherently requires multidisciplinary cooperation. About half of all patients diagnosed with infective endocarditis will meet the criteria to undergo cardiac surgery, which regularly takes place in urgent or emergency settings. The pathophysiology and clinical presentation of infective endocarditis make it a unique disorder within cardiac surgery that warrants a thorough understanding of specific characteristics in the perioperative period. This includes, among others, echocardiography, coagulation, bleeding management, or treatment of organ dysfunction. In this narrative review article, the authors summarize the current knowledge on infective endocarditis relevant for the clinical anesthesiologist in perioperative management of respective patients. Furthermore, the authors advocate for the anesthesiologist to become a structural member of the endocarditis team.

Infective Endocarditis Is a Risk Factor for Heparin Resistance in Adult Cardiovascular Surgical Procedures: A Retrospective Study

OBJECTIVES

Heparin resistance (HR), defined as a decrease in heparin responsiveness, can result in adverse events with prolonged duration of surgery. Although some clinical risk factors have been suggested, the relationship with the surgical diagnosis is unclear. The aim of present study was to elucidate the clinical predictors of HR including the surgical diagnosis.

DESIGN

This retrospective cohort study determined the incidence of HR (defined as activated clotting time [ACT] <400 seconds after 250-350 IU/kg of heparin administration) and heparin sensitivity index (HSI) was calculated from the rate of change in ACT per heparin dose. Preoperative demographic data, medication history, and laboratory data also were analyzed.

SETTING

Single institution, tertiary care hospital.

PARTICIPANTS

Adult patients who underwent cardiovascular surgery with cardiopulmonary bypass between January 2012 and September 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 287 patients, 88 (30.7%) were classified as HR. In univariate analysis, infective endocarditis (IE), platelet count, and serum fibrinogen and albumin levels were associated with HR. After adjustment for baseline ACT and initial heparin dose, IE (odds ratio 4.57, [95% CI: 1.10-19.1]; p = 0.037) and albumin ≤3.5 g/dL (3.17, [1.46-6.93]; p = 0.004) were associated independently with HR. Patients with IE had significantly lower HSI than those with other diseases. All HR patients were treated with additional heparin, and 17 of them received human antithrombin-III concentrate.

CONCLUSIONS

Infective endocarditis and preoperative hypoalbuminemia were associated independently with HR. The optimal anticoagulation strategy for patients with these risk factors requires further investigations based on the authors' findings.

Surgical Revascularization With Cardiopulmonary Bypass on a Patient With Severe COVID-19

The coronavirus disease 2019 (COVID-19) may lead to an acute respiratory distress syndrome by an inappropriate cytokine response and may predispose to a prothrombotic state through multiple pathways. Both can complicate the management of cardiac surgery with cardiopulmonary bypass, which is known to activate the hemostatic system and to exacerbate systemic inflammatory response. Little is known about the impact of cardiac surgery with cardiopulmonary bypass on viral pneumonia, particularly with the new coronavirus. In this article, we describe the case of a diabetic patient with COVID-19 and a concomitant 3-vessel disease with a formal indication for surgical revascularization, who unexpectedly presented with a high heparin resistance during cardiopulmonary bypass. Emphasis is placed on the importance of multidisciplinary team discussions before surgery, on the thorough preoperative assessment, and on the perioperative management, particularly regarding mechanical ventilation and anticoagulation.

Application of goal-directed therapy for the use of concentrated antithrombin for heparin resistance during cardiac surgery

The maintenance of anticoagulation in adult patients undergoing cardiopulmonary bypass is dependent upon a number of factors, including heparin concentration and adequate antithrombin activity. Inadequate anticoagulation increases the risk of thrombosis and jeopardizes both vascular and extracorporeal circuit integrity. The purpose of this study was to evaluate a goal-directed approach for the use of antithrombin in patients who were resistant to heparin. Following institutional review board approval, data were obtained from quality improvement records. A goal-directed protocol for antithrombin was established based upon heparin dosing (400 IU kg^-1 body weight) and achieving an activated clotting time of ⩾500 seconds prior to cardiopulmonary bypass. Two groups of patients were identified as those receiving antithrombin and those not receiving antithrombin. Outcome measures included activated clotting time values and transfusion rates. Consecutive patients (n = 140) were included in the study with 10 (7.1%) in the antithrombin group. The average antithrombin dose was 1,029.0 ± 164.5 IU and all patients had restoration to the activated clotting time levels. Patients in the antithrombin group were on preoperative heparin therapy (80.0% vs. 24.6%, p = 0.001). Prior to cardiopulmonary bypass the activated clotting time values were lower in the antithrombin group (417.7 ± 56.1 seconds vs. 581.1 ± 169.8 seconds, p = 0.003). Antithrombin patients had a lower heparin sensitivity index (0.55 ± 0.17 vs. 1.05 ± 0.44 seconds heparin^-1 IU kg^-1, p = 0.001), received more total heparin (961.3 ± 158.5 IU kg^-1 vs. 677.5 ± 199.0 IU kg^-1, p = 0.001), more cardiopulmonary bypass heparin (22,500 ± 10,300 IU vs. 12,100 ± 13,200 IU, p = 0.016), and more protamine (5.4 ± 1.2 vs. 4.1 ± 1.1 mg kg^-1, p = 0.003). The intraoperative transfusion rate was higher in the antithrombin group (70.0% vs. 35.4%, p = 0.035), but no differences were seen postoperatively. Utilization of a goal-directed algorithm for the administration of antithrombin for the treatment of heparin resistance is effective in patients undergoing cardiac surgery.

Blood clot formation in reinfusion bag with CATSmart: Two case reports

Autologous blood cell salvage reduces the need for postoperative allogeneic blood transfusion and alleviates immunologic reactions, so the technique is commonly used in cardiac surgery. The continuous autotransfusion system is a type of blood cell salvage device. Although the processing program of continuous autotransfusion system includes filtering of several materials from suctioned blood, such as clots, leukocytes, cytokines, and complement, we identified some unexpected blood clots in the reinfusion bag. Pathologic examination revealed that the clots were composed of fibrin, red blood cell aggregates, and histiocytes. We report two cases of these abnormal findings during the use of CATSmart in cardiac surgery.

Thromboprophylaxis in Extracorporeal Circuits: Current Pharmacological Strategies and Future Directions

The development of extracorporeal devices for organ support has been a part of medical history and progression since the late 1900s. These types of technology are primarily used and developed in the field of critical care medicine. Unfractionated heparin, discovered in 1916, has really been the only consistent form of thromboprophylaxis for attenuating or even preventing the blood-biomaterial reaction that occurs when such technologies are initiated. The advent of regional anticoagulation for procedures such as continuous renal replacement therapy and plasmapheresis have certainly removed the risks of systemic heparinization and heparin effect, but the challenges of the blood-biomaterial reaction and downstream effects remain. In addition, regional anticoagulation cannot realistically be applied in a system such as extracorporeal membrane oxygenation because of the high blood flow rates needed to support the patient. More recently, advances in the technology itself have resulted in smaller, more compact extracorporeal life support (ECLS) systems that can-at certain times and in certain patients-run without any form of anticoagulation. However, the majority of patients on ECLS systems require some type of systemic anticoagulation; therefore, the risks of bleeding and thrombosis persist, the most devastating of which is intracranial hemorrhage. We provide a concise overview of the primary and alternate agents and monitoring used for thromboprophylaxis during use of ECLS. In addition, we explore the potential for further biomaterial and technologic developments and what they could provide when applied in the clinical arena.

Review article: heparin sensitivity and resistance: management during cardiopulmonary bypass

Heparin resistance during cardiac surgery is defined as the inability of an adequate heparin dose to increase the activated clotting time (ACT) to the desired level. Failure to attain the target ACT raises concerns that the patient is not fully anticoagulated and initiating cardiopulmonary bypass may result in excessive activation of the hemostatic system. Although antithrombin deficiency has generally been thought to be the primary mechanism of heparin resistance, the reasons for heparin resistance are both complex and multifactorial. Furthermore, the ACT is not specific to heparin's anticoagulant effect and is affected by multiple variables that are commonly present during cardiac surgery. Due to these many variables, it remains unclear whether decreased heparin responsiveness as measured by the ACT represents inadequate anticoagulation. Nevertheless, many clinicians choose a target ACT to assess anticoagulation, and interventions aimed at achieving the target ACT are routinely performed in the setting of heparin resistance. Treatments for heparin resistance/alterations in heparin responsiveness include additional heparin or antithrombin supplementation. In this review, we discuss the variability of heparin potency, heparin responsiveness as measured by the ACT, and the current management of heparin resistance.

Effect of a single bolus of methylene blue prophylaxis on vasopressor and transfusion requirement in infective endocarditis patients undergoing cardiac surgery

Background

The accentuated nitric oxide (NO) release that is induced by the systemic inflammatory response associated with infective endocarditis (IE) and cardiopulmonary bypass (CPB) may result in catecholamine refractory hypotension (vasoplegia) and increased transfusion requirement due to platelet inhibition. Methylene blue (MB) is an inhibitory drug of inducible NO. We aimed to evaluate the effect of prophylactic MB administration before CPB on vasopressor and transfusion requirements in patients with IE undergoing valvular heart surgery (VHS).

Methods

Forty-two adult patients were randomly assigned to receive 2 mg/kg of MB (MB group, n = 21) or saline (control group, n = 21) for 20 min before the initiation of CPB. The primary end points were comparisons of vasopressor requirements serially assessed after weaning from CPB and hemodynamic parameters serially recorded before and after CPB. The secondary endpoint was the comparison of transfusion requirements.

Results

Two patients in the control group received MB after weaning from CPB due to norepinephrine and vasopressin refractory vasoplegia and were thus excluded. There were no significant differences in vasopressor requirements and hemodynamic parameters between the two groups. The mean number of units of packed erythrocytes transfused per transfused patient was significantly less in the MB group. The numbers of patients transfused with fresh frozen plasma and platelet concentrates were less in the MB group.

Conclusions

In IE patients undergoing VHS, prophylactic MB administration before CPB did not confer significant benefits in terms of vasopressor requirements and hemodynamic parameters, but it was associated with a significant reduction in transfusion requirement.

Heparin responsiveness during off-pump coronary artery bypass graft surgery: predictors and clinical implications

AIM

To evaluate the clinical impact of reduced heparin responsiveness (HR(reduced)) on the incidence of myocardial infarction (MI) following off-pump coronary artery bypass graft surgery (OPCAB), and to identify the predictors of HR(reduced).

METHODS

A total of 199 patients scheduled for elective OPCAB were prospectively enrolled. During anastomosis, 150 U/kg of heparin was injected to achieve an activated clotting time (ACT) of ≥ 300 s, and the heparin sensitivity index (HSI) was calculated. HSIs below 1.0 were considered reduced (HR(reduced)). The relationships between the HSI and postoperative MI, cardiac enzyme levels and preoperative risk factors of HR(reduced) were investigated.

RESULTS

There was no significant relationship between the HSI and cardiac enzyme levels after OPCAB. The incidence of MI after OPCAB was not higher in HR(reduced) patients. HR(reduced) occurred more frequently in patients with low plasma albumin concentrations and high platelet counts.

CONCLUSION

HR(reduced) was not associated with adverse ischemic outcomes during the perioperative period in OPCAB patients, which seemed to be attributable to a tight prospective protocol for obtaining a target ACT regardless of the presence of HR(reduced).