The Use of Cangrelor and Heparin for Anticoagulation in a Patient Requiring Pulmonary Thromboendarterectomy Surgery with Suspected Heparin-Induced Thrombocytopenia

Cangrelor for cardiopulmonary bypass in patients with heparin-induced thrombocytopenia: it is not so easy

Anticoagulation management for cardiopulmonary bypass (CPB) is challenging in patients with acute heparin-induced thrombocytopenia (HIT). The strategy of combining cangrelor intraoperatively with heparin for CPB anticoagulation is of increasing interest but exposes to specific unresolved problems. We report the case of a patient requiring surgical pulmonary embolectomy for pulmonary embolism at the very acute phase of HIT, with a high titre of anti-PF4/heparin antibodies and severe thrombocytopenia. For CPB management, cangrelor was administered in combination with heparin prescribed and monitored as usual. Surgery was successfully performed, but postoperatively, the patient developed a new thrombotic event. We discussed the specific problems associated with such strategy, including the dose of cangrelor and its monitoring, the management of the cell-saver, the risk of heparin rebound and the risk of platelet transfusion. These issues must be addressed before considering the combination of cangrelor and unfractionated heparin as a standard of care for CBP.

How to Solve the Conundrum of Heparin-Induced Thrombocytopenia during Cardiopulmonary Bypass

Heparin-induced thrombocytopenia (HIT) is a major issue in cardiac surgery requiring cardiopulmonary bypass (CPB). HIT represents a severe adverse drug reaction after heparin administration. It consists of immune-mediated thrombocytopenia paradoxically leading to thrombotic events. Detection of antibodies against platelets factor 4/heparin (anti-PF4/H) and aggregation of platelets in the presence of heparin in functional in vitro tests confirm the diagnosis. Patients suffering from HIT and requiring cardiac surgery are at high risk of lethal complications and present specific challenges. Four distinct phases are described in the usual HIT timeline, and the anticoagulation strategy chosen for CPB depends on the phase in which the patient is categorized. In this sense, we developed an institutional protocol covering each phase. It consisted of the use of a non-heparin anticoagulant such as bivalirudin, or the association of unfractionated heparin (UFH) with a potent antiplatelet drug such as tirofiban or cangrelor. Temporary reduction of anti-PF4 with intravenous immunoglobulins (IvIg) has recently been described as a complementary strategy. In this article, we briefly described the pathophysiology of HIT and focused on the various strategies that can be applied to safely manage CPB in these patients.

GTH 2021 State of the Art-Cardiac Surgery: The Perioperative Management of Heparin-Induced Thrombocytopenia in Cardiac Surgery

Heparin-induced thrombocytopenia (HIT) is a severe, immune-mediated, adverse drug reaction that paradoxically induces a prothrombotic state. Particularly in the setting of cardiac surgery, where full anticoagulation is required during cardiopulmonary bypass, the management of HIT can be highly challenging, and requires a multidisciplinary approach. In this short review, the different perioperative strategies to run cardiopulmonary bypass will be summarized.

Potential and Limitations of the New P2Y12 Inhibitor, Cangrelor, in Preventing Heparin-Induced Platelet Aggregation During Cardiac Surgery: An In Vitro Study

BACKGROUND

Heparin-induced thrombocytopenia (HIT) can put cardiac surgery patients at a high risk of lethal complications. If anti-PF4/heparin antibodies (anti-PF4/Hep Abs) are present, 2 strategies exist to prevent intraoperative aggregation during bypass surgery: first, using an alternative anticoagulant, and second, using heparin combined with an antiaggregant. The new P2Y12 inhibitor, cangrelor, could be an attractive candidate for the latter strategy; several authors have reported its successful use. The present in vitro study evaluated cangrelor's ability to inhibit heparin-induced platelet aggregation in the presence of anti-PF4/Hep Abs.

METHODS

Platelet-poor plasma (PPP) from 30 patients with functional anti-PF4/Hep Abs was mixed with platelet-rich plasma (PRP) from 5 healthy donors.Light transmission aggregometry was used to measure platelet aggregation after adding 0.5 IU·mL of heparin (HIT) to the plasma, and this was compared with samples spiked with normal saline (control) and samples spiked with cangrelor 500 ng·mL and heparin 0.5 IU·mL (treatment). Friedman test with post hoc Dunn-Bonferroni test was used for between-group comparisons.

RESULTS

Heparin 0.5 IU·mL triggered aggregation in 22 of 44 PPP-PRP mixtures, with a median aggregation of 86% (interquartile range [IQR], 69-91). The median aggregation of these 22 positive samples' respective control tests was 22% (IQR, 16-30) (P < .001). Median aggregation in the cangrelor-treated samples was 29% (IQR, 19-54) and significantly lower than the HIT samples (P < .001). Cangrelor inhibited heparin-induced aggregation by a median of 91% (IQR, 52-100). Cangrelor only reduced heparin-induced aggregation by >95% in 10 of the 22 positive samples (45%). Cangrelor inhibited heparin-induced aggregation by <50% in 5 of the 22 positive samples (22%) and by <10% in 3 samples (14%).

CONCLUSIONS

This in vitro study found that cangrelor was an unreliable inhibitor of heparin-induced aggregation in the presence of anti-PF4/Hep Abs. We conclude that cangrelor should not be used as a standard antiaggregant for cardiac patients affected by HIT during surgery. Unless cangrelor's efficacy in a particular patient has been confirmed in a presurgery aggregation test, other strategies should be chosen.

Heparin-Induced Thrombocytopenia in Patients Undergoing Valvular and Aortic Surgery: A Modern Assessment of Risk

Objective

The incidence and outcomes of patients with heparin-induced thrombocytopenia (HIT) are well defined for general cardiac surgical populations. The purpose of this study was to define the outcomes of patients with HIT in a population excluding patients who underwent coronary artery bypass grafting (CABG).

Methods

The local Society of Thoracic Surgeons cardiac surgical database was queried between January 2008 and May 2017 for patients who underwent either open valvular surgery or aortic surgery. Patients who underwent either isolated or combined CABG procedures were excluded. Cohorts were formed based on the presence or absence of postoperative HIT. Logistic regression models were built to determine the association between postoperative HIT and outcomes, adjusted for both preoperative and intraoperative variables.

Results

Of the total cohort (8,107 patients), 176 patients (2.2%) developed HIT after surgery. HIT patients experienced an increased incidence of morbidities postoperatively, including reoperation for bleeding, reoperation for cardiac and noncardiac etiologies, postoperative stroke, perioperative myocardial infarction, postoperative sternal infection, postoperative arrhythmia, new-onset renal failure, and dialysis (all with P < 0.01). The unadjusted 30-day mortality was 14.8% in HIT patients vs 4.9% in those without HIT ( P < 0.01). After risk adjustment, reoperation for noncardiac events, renal failure, new dialysis, postoperative stroke, arrhythmia, and sternal wound infection remained significantly elevated in patients who developed postoperative HIT.

Conclusions

Patients who developed HIT after non-CABG cardiac surgery experienced increased postoperative rates of morbidity and mortality. Early diagnosis and treatment remained mainstays of therapy. Early identification of patients at highest risk should prompt careful risk stratification when possible.

Cangrelor alleviates bleomycin-induced pulmonary fibrosis by inhibiting platelet activation in mice

Pulmonary fibrosis is a progressive chronic inflammatory lung disease whose pathogenesis is complicated. Platelets and neutrophils play important roles in the progression of pulmonary inflammation. We have reported that cangrelor, a non-sepesific GPR17 antagonist, alleviates pulmonary fibrosis partly by inhibiting macrophage inflammation in mice. Cangrelor is also a well-known anti-platelet agent. To test whether cangrelor mitigated pulmonary fibrosis partly through the inhibition of platelets, bleomycin (BLM) was used to induce pulmonary fibrosis in C57BL/6 J mice. We found that cangrelor (10 mg/kg) not only significantly decreased BLM-induced release of inflammatory cytokines (PF4, CD40 L and MPO), but also decreased the increment of platelets, neutrophils and platelet-neutrophil aggregates in the fibrotic lung and in the peripheral blood of BLM-treated mice. In addition, cangrelor decreased the number of CD40 and MPO double positive neutrophils and the expression level of CD40 in BLM-treated mouse lungs. Based on these results we conclude that cangrelor alleviates BLM-induced lung inflammation and pulmonary fibrosis in mice, partly through inhibition of platelet activation, therefore reducing the infiltration of neutrophils due to the adhesion of platelets and neutrophils mediated by CD40 - CD40 L interaction. Cangrelor could be a potential therapeutic medicine for pulmonary fibrosis.

Novel Use of Cangrelor With Heparin During Cardiopulmonary Bypass in Patients With Heparin-Induced Thrombocytopenia Who Require Cardiovascular Surgery: A Case Series

Optimal anticoagulation strategy during cardiopulmonary bypass (CPB) remains uncertain in patients with heparin-induced thrombocytopenia (HIT) who require urgent/emergent cardiac surgery. We describe our strategy and experience with utilizing cangrelor in combination with heparin for anticoagulation during CPB in patients with different phases of HIT undergoing a wide range of urgent/emergent cardiovascular surgery. Cangrelor is an intravenous direct-acting P2Y12 platelet receptor antagonist that achieves therapeutic effect and eliminates rapidly. Its antiplatelet activity is unaffected by stagnation of blood, nor is it influenced by patient's sex, age, renal status, or hepatic function. Our institutional alternative intraoperative anticoagulation strategy for HIT patients is to administer cangrelor with a loading dose of 30 μg/kg, followed by continuous infusion of 4 μg/kg/min throughout CPB via a dedicated intravenous access. VerifyNow P2Y12 reaction unit point-of-care assay is utilized to monitor platelet inhibition throughout surgery. Cangrelor infusion is discontinued 10 minutes prior to heparin reversal with protamine. Ten urgent/emergent cardiovascular surgeries were performed at our institution using cangrelor with heparin for anticoagulation during CPB, and the majority were pulmonary thromboendarterectomy (60%). HIT was confirmed in 3 cases and was suspected in 4 which was found to be negative after the operation. One case of subacute B HIT and 2 cases of remote HIT were included in this series. This novel alternative intraoperative anticoagulation strategy was well tolerated by all patients. There was neither serious postoperative thrombotic event nor major postoperative bleeding complication that required reoperation. One death occurred in a patient with advanced intracardiac malignancy, whose life support was ultimately withdrawn postoperatively. Median postoperative intensive care unit stay was 7.2 ± 5.5 days, while median postoperative hospital stay was 16.3 ± 10.8 days. In patients with various phases of HIT who require urgent/emergent on-pump cardiovascular surgery, the use of cangrelor with heparin may be a convenient, safe, and effective alternative intraoperative anticoagulation strategy providing acceptable outcomes.

Cardiac Surgery Successfully Managed With Cangrelor in a Patient With Persistent Anti-PF4/Heparin Antibodies 8 Years After Heparin-Induced Thrombocytopenia

A 66-YEAR-OLD female requiring cardiac surgery had persisting anti-platelet factor 4 (PF4)/heparin antibodies (HIT-abs) 8 years after heparin-induced thrombocytopenia (HIT). In 2010, she developed thrombotic thrombocytopenic purpura (TTP) (ADAMTS-13 <5%, inhibitor at 1.0 BU/mL), which was treated successfully with corticotherapy, plasmapheresis, and intravenous heparin. While taking heparin, she developed HIT, as evidenced by a positive functional test. Her platelet count fully resolved without thrombotic complications with danaparoid treatment. In 2018, the preoperative titer of HIT-abs was still 0.38 U/mL by chemoluminescent immunoassay (CLIA), and positive by particle-gel agglutination immunoassay (PaGIA) with a titer of 2 and was strongly positive on an enzyme-linked immunosorbent assay (ELISA). The authors of the case report chose to use cangrelor combined with heparin during cardiopulmonary bypass (CPB). Cangrelor was used without increased postoperative bleeding or thrombotic complications. Postoperatively she exhibited a huge rise in HIT-abs (14.22 U/mL on postoperative day 11) with a positive functional assay. There was no recurrence of HIT, however. This case illustrates the importance of excluding the presence of persisting HIT-abs before CPB and ensuring close medical follow-up after even a single exposure to heparin.