Update in hematology: heparin-induced thrombocytopenia and bivalirudin

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 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.

Perioperative use of iloprost in cardiac surgery patients diagnosed with heparin-induced thrombocytopenia-reactive antibodies or with true HIT (HIT-reactive antibodies plus thrombocytopenia): An 11-year experience

Thrombocytopenia and thromboembolism(s) may develop in heparin immune-mediated thrombocytopenia (HIT) patients after reexposure to heparin. At the Onassis Cardiac Surgery Center, 530 out of 17,000 patients requiring heart surgery over an 11-year period underwent preoperative HIT assessment by ELISA and a three-point heparin-induced platelet aggregation assay (HIPAG). The screening identified 110 patients with HIT-reactive antibodies, out of which 46 were also thrombocytopenic (true HIT). Cardiac surgery was performed in HIT-positive patients under heparin anticoagulation and iloprost infusion. A control group of 118 HIT-negative patients received heparin but no iloprost during surgery. For the first 20 patients, the dose of iloprost diminishing the HIPAG test to ≤5% was determined prior to surgery by in vitro titration using the patients' own plasma and donor platelets. In parallel, the iloprost "target dose" was also established for each patient intraoperatively, but before heparin administration. Iloprost was infused initially at 3 ng/kg/mL and further adjusted intraoperatively, until ex vivo aggregation reached ≤5%. As a close correlation was observed between the "target dose" identified before surgery and that established intraoperatively, the remaining 90 patients were administered iloprost starting at the presurgery identified "target dose." This process significantly reduced the number of intraoperative HIPAG reassessments needed to determine the iloprost target dose, and reduced surgical time, while maintaining similar primary clinical outcomes to controls. Therefore, infusion of iloprost throughout surgery, under continuous titration, allows cardiac surgery to be undertaken safely using heparin, while avoiding life-threatening iloprost-induced hypotension in patients diagnosed with HIT-reactive antibodies or true HIT.

Development and implementation of a nurse-driven, sliding-scale nomogram for bivalirudin in the management of heparin-induced thrombocytopenia

PURPOSE

A simplified dosing nomogram to assist nurses in adjusting the rate of i.v. bivalirudin administration in cases of heparin-induced thrombocytopenia (HIT) is described.

SUMMARY

To facilitate the availability of bivalirudin [corrected] as an alternative direct thrombin inhibitor (DTI) for patients with HIT at The Ohio State University Wexner Medical Center (OSUWMC), a team of clinical pharmacists developed a nomogram designed to simplify infusion dosage adjustments by nurses. In contrast to bivalirudin nomograms requiring patient-specific, percentage-based dose adjustments, the nomogram developed at OSUWMC specifies fixed adjustments (0.005 or 0.01 mg/kg/hr) according to the current activated partial thromboplastin time (aPTT) value relative to aPTT goals. During pilot testing over three years, the nomogram was used to guide dosage adjustments in 65 adult patients receiving continuous infusions of bivalirudin for suspected or confirmed HIT in intensive care units. Overall, the use of the nomogram resulted in adequate anticoagulation, with 53.7% of all measured aPTT values in the target range; 30.5% of aPTT values were below target, and 15.8% of values were above target. The median time to steady state was 11.0 hours (range, 5.0-31.8 hours), and bleeding rates were consistent with those reported in the literature. Nurse adherence to the nomogram was 100%, and no dosing errors occurred during a total of 487 dosage changes. Based on the pilot study results, the nomogram was refined to improve initial dosing for patients with creatinine clearance values of >30 mL/min; other refinements were made to enhance the safety of bivalirudin therapy for HIT in patients with severe renal impairment.

CONCLUSION

A nurse-driven, sliding-scale nomogram for bivalirudin therapy in patients with HIT provided a simple dosing protocol and resulted in a high rate of adherence by nurses.

Intravenous warfarin and heparin-induced thrombocytopenia: making the diagnosis, management, modern monitoring, and multidisciplinary care

OBJECTIVE

To describe the diagnosis, management, and monitoring of a patient with heparin-induced thrombocytopenia (HIT) with thrombosis and simultaneous bleeding risk treated with argatroban and transitioned to intravenous (IV) warfarin secondary to the inability to administer enteral medications.

CASE SUMMARY

A 71-year-old man was admitted to the surgical intensive care unit (SICU) following aortic valve repair, coronary artery bypass, and ascending aortic aneurysm repair. On postoperative day 9, he was found to have a pulmonary embolism, and therapeutic heparin was started. The following day, his platelet count was found to have dropped precipitously. HIT was diagnosed, heparin was discontinued, and argatroban was initiated. On postoperative day 22, anticoagulation was discontinued because of massive gastrointestinal bleeding. On postoperative day 35, multiple venous thromboses were found, and argatroban was restarted. The patient developed a high-output enterocutaneous fistula, eliminating the option of enteral route of medication administration. The multidisciplinary SICU team transitioned the patient from argatroban to IV warfarin for long-term anticoagulation. The international normalized ratio was monitored and remained therapeutic throughout his admission without further thrombotic complications.

DISCUSSION

HIT occurs when antibodies develop to heparin-platelet factor 4 complexes, causing simultaneous hypercoagulability and thrombocytopenia. It is diagnosed based on both clinical factors and laboratory testing. Treatment includes discontinuation of all forms of heparin; initiation of a nonheparin anticoagulant, such as argatroban; and transition to warfarin.

CONCLUSIONS

IV warfarin is a therapeutic option for patients with malabsorption issues. A multidisciplinary team in an intensive care setting optimizes cost-effective, patient-centered, and safe care.

Progress in platelet blockers: the target is the P2Y12 receptor

The considerable progress in P2Y12-platelet blockers has important perioperative implications due to a family of novel agents beyond clopidogrel. Although prasugrel is more potent than clopidogrel due to more efficient hepatic metabolism, it is limited clinically by its irreversibility and bleeding risks. Ticagrelor, as the first approved direct and reversible oral P2Y12 blocker, still is limited clinically by its novel side-effect profile. Intravenous reversible P2Y12 blockade is possible now with both cangrelor and elinogrel, although both agents are still in clinical development. Furthermore, elinogrel offers the possibility of both oral and parenteral P2Y12 blockade with a single agent. Future trials likely will continue to evaluate and compare the safety and efficacy of these agents in multiple clinical settings, including the perioperative period.

The year in Cardiothoracic and Vascular Anesthesia: selected highlights from 2011

There have been rapid advances in oral anticoagulation. The oral factor Xa inhibitors rivaroxaban and apixaban and the oral direct thrombin inhibitor dabigatran recently have been rigorously evaluated. These novel anticoagulants will usher in a new paradigm for perioperative anticoagulation. Perioperative blood conservation in cardiac surgery recently has been highlighted in the updated guidelines by the Society of Cardiovascular Anesthesiologists and the Society of Thoracic Surgeons. These recommendations reflect a comprehensive evaluation of the recent evidence to optimize transfusion practice. Transcatheter mitral valve repair continues to mature. Transcatheter aortic valve implantation for aortic stenosis has entered the clinical mainstream, with randomized trials showing its superiority over medical management and its equivalency to surgical valve replacement in high-risk patients. This transformational technology represents a major leadership opportunity for the cardiac anesthesiologist. Minimally invasive valve surgery has shown effectiveness in high-risk patients. Radial access is equivalent to femoral access for percutaneous coronary intervention in acute coronary syndromes but significantly reduces the risk of local vascular complications. Recent trials have further clarified the roles of medical therapy, percutaneous coronary intervention, and coronary artery bypass surgery in patients with significant coronary artery disease and left ventricular dysfunction. The past year has witnessed major advances in cardiovascular practice with new drugs, new devices, and new guidelines. The coming year most likely will advance these achievements to enhance the care of patients.

Management of heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a rare but severe prothrombotic adverse effect of heparin treatment. The underlying cause is the formation of highly immunogenic complexes between negatively charged heparin and positively charged platelet factor 4 (PF4). Resulting antibodies against these PF4/heparin complexes can activate platelets via the platelet FcγIIa receptor, leading to thrombin generation and thus to the paradox of a prothrombotic state despite thrombocytopenia and application of heparin. Prompt diagnosis of HIT is important in order to change treatment to prevent severe thromboembolic complications. However, this is often difficult as thrombocytopenia is frequent in hospitalized patients and the commercially available laboratory tests for HIT antibodies have a high negative predictive value but only a poor positive predictive value. This leads to overdiagnosis and overtreatment of HIT, which also bear the risk for adverse outcomes.

AREAS COVERED

This review aims at resuming recent data on HIT, thereby focusing on the role of new anticoagulants and providing a framework for diagnosis and treatment. Furthermore, it provides some insights into the pathogenesis of this peculiar adverse drug reaction and ventures a guess at its future relevance in clinical practice.

EXPERT OPINION

New drugs which are strongly negatively charged should be assessed for their capacity to form complexes with PF4. If they do so, they bear the risk of inducing a HIT-like immune response. The immunology of HIT is still largely unresolved. Understanding HIT might provide insights into other immune and autoimmune response mechanisms.