Serial EXTEM, FIBTEM, and tPA Rotational Thromboelastometry Observations in the Maastricht Intensive Care COVID Cohort-Persistence of Hypercoagulability and Hypofibrinolysis Despite Anticoagulation

Background: Coronavirus Disease 2019 (COVID-19) patients often present with thromboembolic events. In COVID-19 patients, routine hemostatic assays cannot correctly identify patients at risk for thromboembolic events. Viscoelastic testing with rotational thromboelastometry (ROTEM) might improve the characterization of COVID-19-associated coagulopathy.

Objective: To unravel underlying coagulopathy and fibrinolysis over time as measured by serial assessment heparin-independent (FIBTEM and EXTEM) and fibrinolysis illustrating (tissue plasminogen activator; tPA) ROTEM assays.

Patients/Methods: Between April 23 and June 12, consecutive adult patients enrolled within the Maastricht Intensive Care COVID (MaastrICCht) cohort were included, and a comprehensive set of clinical, physiological, pharmaceutical, and laboratory variables were collected daily. Twice per week, EXTEM, FIBTEM, and tPA ROTEM were performed. Clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF), lysis onset time (LOT), and lysis time (LT) were determined to assess clot development and breakdown and were compared to routine hemostatic assays.

Results: In 36 patients, 96 EXTEM/FIBTEM and 87 tPA ROTEM tests were performed during a 6-week follow-up. CT prolongation was present in 54% of EXTEM measurements, which were not matched by prothrombin time (PT) in 37%. Respectively, 81 and 99% of all EXTEM and FIBTEM MCF values were above the reference range, and median MCF remained elevated during follow-up. The ROTEM fibrinolysis parameters remained prolonged with median LOT consequently >49 min and unmeasurable LT in 56% of measurements, suggesting a severe hypofibrinolytic phenotype.

Conclusion: ROTEM tests in COVID-19 ICU patients show hypercoagulability and severe hypofibrinolysis persisting over at least 6 weeks.

Harmonizing light transmission aggregometry in the Netherlands by implementation of the SSC-ISTH guideline

Light transmission aggregometry (LTA) is considered the gold standard method for evaluation of platelet function. However, there are a lot of variation in protocols (pre-analytical procedures and agonist concentrations) and results. The aim of our study was to establish a national LTA protocol, to investigate the effect of standardization and to define national reference values for LTA. The SSC guideline was used as base for a national procedure. Almost all recommendations of the SSC were followed e.g. no adjustment of PRP, citrate concentration of 109 mM, 21 needle gauge, fasting, resting time for whole blood and PRP, centrifugation time, speed and agonists concentrations. LTA of healthy volunteers was measured in a total of 16 hospitals with 5 hospitals before and after standardization. Results of more than 120 healthy volunteers (maximum aggregation %) were collected, with participating laboratories using 4 different analyzers with different reagents. Use of low agonist concentrations showed high variation before and after standardization, with the exception of collagen. For most high agonist concentrations (ADP, collagen, ristocetin, epinephrine and arachidonic acid) variability in healthy subjects decreased after standardization. We can conclude that a standardized Dutch protocol for LTA, based on the SSC guideline, does not result in smaller variability in healthy volunteers for all agonist concentrations.

The Influence of Prostaglandin E1 and Use of Inhibitor Percentage on the Correlation between the Multiplate and VerifyNow in Patients on Dual Antiplatelet Therapy

Platelet function tests (PFT), such as the Multiple Electrode Analyzer (Multiplate) and VerifyNow, show little concordance in patients using antiplatelet drugs. A major difference between these tests is the use of prostaglandin E1 (PGE1) to inhibit P2Y1-platelet-receptor activation in VerifyNow and is proposed to be of influence in the discrepancy between these tests. We aimed to investigate whether the presence of PGE1 could provide an explanation for the moderate correlation and concordance between Multiplate and VerifyNow by adding PGE1 to the Multiplate ADP assay, also known as the ADP-high sensitivity (ADP-HS) assay. We also aimed to investigate whether the difference in baseline platelet function as measured by the VerifyNow and Multiplate could (partly) explain the moderate correlation between the tests, by plotting ADP assay results against baseline function as measured by the corresponding device, which is expressed as the 'inhibitor percentage.' Fifty-one patients who underwent percutaneous coronary intervention (PCI) received dual antiplatelet therapy and were considered to have a high risk of ischemic or bleeding complications were included. The addition of 20 µl PGE1 in the Multiplate resulted in a significant reduction in Arbitrary Aggregation Units, but did not improve correlation with the VerifyNow. The correlation between VerifyNow and Multiplate inhibitor percentage was moderate. Based on these results, we concluded that neither PGE1 nor the calculation of the inhibitor percentage greatly influenced the correlation between PFTs.

Detecting clinically relevant rivaroxaban or dabigatran levels by routine coagulation tests or thromboelastography in a cohort of patients with atrial fibrillation

BACKGROUND

Traditional coagulation tests are included in emergency guidelines for management of patients on direct oral anticoagulants (DOACs) who experience acute bleeding or require surgery. We determined the ability of traditional coagulation tests and fast whole blood thromboelastography (ROTEM®) to screen for anticoagulation activity of dabigatran and rivaroxaban as low as 30 ng/mL.

METHODS

One hundred eighty-four citrated blood samples (75 dabigatran, 109 rivaroxaban) were collected from patients with non-valvular atrial fibrillation (NVAF), to perform screening tests from different manufacturers, (diluted, D) PT, aPTT, TT and ROTEM®. The activity of DOACs was quantitatively determined by clot detection assays: Hemoclot DTT and DiXaI test (Biophen), on CS2100 (Siemens). The clotting time (CT) of INTEM and EXTEM ROTEM® (Werfen) were used as test parameters.

RESULTS

Dabigatran, ≥ 30 ng/mL, was accurately detected by five coagulation tests: APTT Actin FSL (93%), PT Neoplastin (93%), APTT Cephascreen, Thromboclotin, and Thrombin (all 100%), but not by PT Innovin (49%). CT-EXTEM (91%) was sufficiently sensitive, but not CT-INTEM (52%). APTT Cephascreen and Thrombin showed good linearity (R2 = 0.71,R2 = 0.72). For the other tests linearity was moderate to poor. Rivaroxaban was accurately detected by PT Neoplastin (98%) and less so by APTT Cephascreen (85%). In addition, rivaroxaban was also accurately detected by CT-INTEM (96%). PT Neoplastin showed good linearity (R2 = 0.81), all other tests had moderate to poor linearity.

CONCLUSION

In patients with NVAF, the ability of routine coagulation tests to detect the presence of significant levels of DOACs is test and reagent dependent. CT-INTEM and CT-EXTEM may be fast whole blood alternatives.

TRIAL REGISTRATION

The Institutional Review Board of the MUMC approved this study (December 2011, project number 114069).

Early platelet recovery following cardiac surgery with cardiopulmonary bypass

Coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) is frequently associated with low platelet count (PC) and disturbed platelet function (PF). While PC is easy to measure, PF is more difficult to assess. Moreover, the time-related platelet dysfunction and recovery after CPB is not fully elucidated. Platelet dysfunction could lead to bleeding but also to coronary graft failure. Laboratory tests could provide more insights into PF after CABG. The aim of the current study was to investigate the time-related PF induced by CPB. Blood samples of 20 patients with a preoperative PC of more than 250 × 10⁹/L were collected before incision, after weaning from CPB, and 24 h postoperative. Platelet contribution to coagulation was quantified by PLTEM (calculated by means of EXTEM and FIBTEM results). PF was assessed by multiple electrode impedance aggregometry (MEIA) in whole blood and by light transmission aggregometry (LTA) in platelet-rich plasma after stimulation with arachidonic acid (AA), adenosine diphosphate, collagen, and thrombin-receptor-activating peptide. LTA and MEIA analysis demonstrated significant platelet dysfunction after CPB, with partial recovery within 24 h after surgery. AA-induced platelet aggregation increased to higher levels within 24 h after surgery compared to baseline values as measured by LTA. PLTEM maximum clot firmness remained unchanged throughout the study. Correlation analyses revealed that MEIA and rotational thromboelastometry (ROTEM), but not LTA, were dependent on PC and hematocrit. No correlations were found between LTA, MEIA, ROTEM, PC, and clinical outcome parameters. Our results demonstrate a reversible platelet dysfunction recovering within 24 h after CPB. Interestingly, AA-induced platelet aggregation increases to higher levels during the first 24 h postoperatively, which might be important for early initiation of antiplatelet therapy after CABG. MEIA as POC test is able to detect platelet dysfunction during cardiac surgery with a PC of ≥150 × 10⁹/L.