Anna Ågren

Thromboembolic safety and efficacy of prothrombin complex concentrates in the emergency reversal of warfarin coagulopathy

BACKGROUND There is uncertainty regarding the efficacy and incidence of thromboembolic events in patients treated with prothrombin complex concentrates (PCC) for the emergency reversal of warfarin effect. METHODS During 2002 to 2010 we prospectively included 160 patients treated with PCC for emergency reversal of warfarin either for bleeding or because of the need of emergency surgery. A possible relationship to PCC was considered if objectively verified thromboembolism occurred within 7days of PCC administration. Efficacy was adjudicated as good if the bleeding was controlled promptly or if the surgeon did not report excessive perioperative bleeding. RESULTS We included 160 patients; 72% received PCC for bleeding. The median international normalized ratio (INR) before and after treatment with PCC was 3.5 (interquartile range [IQR] 2.6-5.4) and 1.4 (IQR 1.2-1.6). The mean dose of PCC was 1800IU (IQR 1200-2000). In addition to PCC, 74% of the patients received vitamin K and 34% received plasma. Six patients (3.8%; 95% confidence interval [CI], 1.4-8.0%) developed thromboembolic events (3 strokes, 1 myocardial infarction, 1 deep vein thrombosis, 1 splenic infarction), possibly related to PCC. The clinical efficacy was good in 146 (91%), moderate in 6 (4%), poor in 4 (2.5%) and non-evaluable in 4 patients. CONCLUSION The administration of PCC for the emergency reversal of warfarin may be associated with a low risk of thromboembolism. The contribution of an unmasked thrombotic process by cessation of anticoagulation or of activation of coagulation by the hemorrhagic event should also be considered.

Evaluation of low PAI-1 activity as a risk factor for hemorrhagic diathesis

Summary.  Background: Prospective studies of the epidemiology and clinical significance of low plasminogen activator inhibitor type 1 (PAI‐1) activity are lacking. Objective: To evaluate the prevalence of low PAI‐1 activity in patients with a bleeding tendency in comparison with a normal population. Methods: In 586 consecutive patients, referred because of bleeding symptoms, we added analyses of PAI‐1 activity and tissue plasminogen activator complex with PAI‐1 (t‐PA–PAI‐1) to the routine investigation, consisting of platelet count, bleeding time, prothrombin time, activated partial thromboplastin time, fibrinogen, factor VIII, von Willebrand factor activity, and antigen. Controls were 100 blood donors and 100 age‐ and sex‐matched healthy individuals. The latter were also evaluated regarding the previous bleeding episodes. The bleeding history was classified as clinically significant or not, and the criteria were fulfilled in 75% of the patients and 18% of the healthy controls. Results: The routine laboratory investigation of the patients was negative in 57%. Low PAI‐1 activity, defined as <1.0 U mL−1, was found in 23% of the patients and in 13% and 10% of the blood donors and healthy controls, respectively (odds ratio and 95% CI, 2.04; 1.11–3.77 and 2.75; 1.39–5.42, respectively). The difference remained statistically significant after the adjustment for body mass index, use of estrogens, sex and age (odds ratio for patients vs. healthy controls 3.23; 95% CI, 1.22–8.56, P = 0.019). The distribution of the 4G/5G genotypes in the patients was not different from that of two control populations. No specific symptom predicted for low PAI‐1, which did not aggravate the clinical picture in association with the other hemostatic defects. Low tPA–PAI‐1 was not associated with the increased bleeding tendency. Conclusion: Low PAI‐1 activity is common in patients with a bleeding diathesis, but it is a risk factor of minor clinical importance and not associated with specific bleeding manifestations.

Detection of elevated INR by thromboelastometry and thromboelastography in warfarin treated patients and healthy controls

INTRODUCTION The diagnostic potential of whole blood viscoelastic tests thromboelastography (TEG®) and thromboelastometry (ROTEM®) to detect warfarin-induced INR elevation remains elusive. METHODS Viscoelastic tests were performed in 107 patients on warfarin and 89 healthy controls. Tests were activated by kaolin for TEG, and ellagic acid (INTEM) or tissue factor (EXTEM) for ROTEM. RESULTS Viscoelastic tests revealed significant differences in clotting profiles between controls and warfarin-treated patients. Compared with healthy controls, patients treated with warfarin had prolonged EXTEM clotting and TEG reaction time (p<0.001), both of which were also increased beyond the reference range. Increased INR values correlated with EXTEM CT (Spearman rho=0.87) and TEG R-time (rho=0.73). EXTEM CT had a sensitivity and specificity of 0.89 and 1.00, respectively, to detect elevated INR above 1.2 units, with a positive and negative predictive values (PPV and NPV) of 1.00 and 0.88, respectively. Similarly, TEG R-time had a sensitivity and specificity of 0.86 and 0.87, respectively, with a PPV of 0.89 and a NPV of 0.83. The corresponding receiver operator characteristic area under the curve was 0.99 (95% confidence interval [CI], 0.99 - 1.00) for EXTEM CT and 0.94 (95% CI, 0.91 - 0.97) for TEG R-time. CONCLUSIONS Tissue factor-activated viscoelastic testing (EXTEM) revealed individuals with warfarin-induced INR elevation accurately, while TEG - activated through the intrinsic pathway - still was of acceptable diagnostic value. Further studies are required to evaluate the diagnostic potential of viscoelastic tests in relation to standard laboratory tests in other mixed patient populations, where the PPV and NPV may be inferior.

Thromboelastography (TEG®) compared to conventional coagulation tests in surgical patients – a laboratory evaluation

Abstract Background. Several methods exist for evaluation of hypocoagulation in patients with perioperative bleeding, e.g. thromboelastography (TEG®) and conventional methods (platelet count, aPTT, INR and fibrinogen). Considering the vast experience of conventional methods it is important to investigate how well the methods correspond. Methods. Sixty surgical patients were included prospectively and blood samples were taken perioperatively. TEG® and conventional parameters were analyzed simultaneously. An assessment of coagulopathy, based on a synthesis of the conventional methods, was done by two experienced coagulation specialists, blinded from the results of TEG® and from the results of each other. Hypocoagulation, defined by TEG® parameters; reaction time (R-time), angle, maximal amplitude (MA) and fibrinolysis, was evaluated according to a commonly used algorithm. Results. To detect a platelet count below 150 × 109 L−1, the sensitivity of TEG was 17% (95% CI, 7–36%) with angle and 25% (95% CI, 11–45%) with MA. The sensitivity to detect fibrinogen below 2 g/L was 11% (95% CI, 3–29%) with angle and 21% with MA (95% CI, 8–43%). To detect aPTT more than 40 s and INR more than 1.2 with R-time, the sensitivity was 19% (95% CI, 8–37%) and 0% (95% CI, 0–69%) respectively. The agreement of the evaluators assessments of hypocoagulation was 100%, but the agreement with the overall TEG® analysis was poor with a sensitivity of 33% and a specificity of 95%. Conclusion. The agreement between conventional laboratory tests and TEG is poor, but it remains uncertain which type of coagulation tests that best reflects the actual bleeding risk.

Studies of microparticles in patients with the antiphospholipid syndrome (APS)

Objectives: To study circulating platelet, monocyte and endothelial microparticles (PMPs, MMPs and EMPs) in patients with antiphospholipid syndrome (APS) in comparison with healthy controls. Material and method: Fifty-two patients with APS and 52 healthy controls were investigated. MPs were measured on a flow cytometer (Beckman Gallios) and defined as particles sized < 1.0 µm, negative to phalloidin, positive to lactadherin and positive to either CD42a (PMPs), CD144 (EMPs) or CD14 (MMPs). Exposure of CD142 (TF) was measured on CD144 positive MPs. Results: Total number of MPs (i.e. lactadherin positive particles) was higher in APS patients versus controls (p < 0.001). An increased number of EMPs (p < 0.001), increased TF-positive EMPs (p < 0.001) and increased MMPs (p < 0.001) were also observed. PMP numbers did not differ between the groups. None of the MP types differed in numbers between obstetric and thrombotic APS patients. Conclusion: We observed a high number of EMPs expressing TF in APS patients. The numbers of MMPs and total EMPs were also higher as compared with healthy controls but in contrast to previous reports, the number of PMPs did not differ between groups.

Management of rivaroxaban or apixaban associated major bleeding with prothrombin complex concentrates: a cohort study

There is uncertainty regarding the effectiveness and occurrence of thromboembolic events in patients treated with prothrombin complex concentrates (PCCs) for the management of major bleeding events (MBEs) on rivaroxaban or apixaban. We investigated the effectiveness of PCCs given for the management of MBEs in patients on rivaroxaban or apixaban. Between 1 January 2014 and 1 October 2016, we prospectively included patients on rivaroxaban or apixaban treated with PCCs for the management of MBEs. The effectiveness of PCCs was assessed by using the International Society of Thrombosis and Hemostasis Scientific and Standardization Subcommittee criteria for the assessment of the effectiveness of major bleeding management. The safety outcomes were thromboembolic events and all-cause mortality within 30 days after treatment with PCCs. A total of 84 patients received PCCs for the reversal of rivaroxaban or apixaban due to a MBE. PCCs were given at a median (interquartile range) dose of 2000 IU (1500-2000 IU). Intracranial hemorrhage (ICH) was the most common site of bleeding requiring reversal (n = 59; 70.2%), followed by gastrointestinal bleeding in 13 (15.5%) patients. Management with PCCs was assessed as effective in 58 (69.1%) patients and ineffective in 26 (30.9%) patients. Most patients with ineffective hemostasis with PCCs had ICH (n = 16; 61.5%). Two patients developed an ischemic stroke, occurring 5 and 10 days after treatment with PCC. Twenty-seven (32%) patients died within 30 days after a MBE. The administration of PCCs for the management of MBEs associated with rivaroxaban or apixaban is effective in most cases and is associated with a low risk of thromboembolism. Our findings are limited by the absence of a control group in the study.

TEG® functional fibrinogen analysis may overestimate fibrinogen levels.

Fibrinogen is of crucial importance in patients with ongoing bleeding. In this study, we compared fibrinogen concentration measured by thrombelastography (TEG®) with fibrinogen plasma concentration determined by Clauss. Sixty-three surgical patients and 38 healthy controls were included. For the whole group (patients and controls, n = 101), TEG® functional fibrinogen was on average 1.0 g/L higher than the plasma fibrinogen concentration (3.5 vs 2.5 g/L, 95% confidence interval for difference 0.8 to 1.2 g/L, P < 0.0001). Similar patterns were observed when patients and healthy controls were analysed separately. The fibrinogen level may be overestimated when assessed using TEG® compared with the fibrinogen plasma concentration measured by the conventional method.

Laboratory evidence of hyperfibrinolysis in association with low plasminogen activator inhibitor type 1 activity.

Low activity of plasminogen activator inhibitor type 1 (PAI-1) has been associated with bleeding complications in surgery. We earlier reported a higher prevalence of low PAI-1 activity among patients with bleeding tendency as compared with normal control individuals. The present study evaluated whether low PAI-1 activity actually is associated with markers of increased fibrinolytic activity in plasma from patients with a history of bleeding. PAI-1 activity, plasmin–antiplasmin complex (PAP) and D-dimer were analyzed in plasma samples from 424 consecutive patients referred to the Coagulation Unit for investigation of bleeding symptoms. The median PAI-1 activity was 4.0 U/ml [interquartile range (IQR), 1–10 U/ml], the median PAP level was 1.59 mg/l (IQR, 1.40–1.91 mg/l) and the median D-dimer level was 71 μg/l (IQR, 46–111 μg/l). The median PAP concentration for patients with PAI-1 less than 1.0 U/ml was 1.73 mg/l (IQR, 1.53–2.30 mg/l), and that for PAI-1 of at least 1.0 U/ml was 1.54 mg/l (IQR, 1.36–1.83 mg/l) (P < 0.0001). There was also a significant difference between the PAP levels in patients with normal PAI-1 (1–15 U/ml) versus elevated PAI-1 (> 15 U/ml) (P = 0.024). The level of D-dimer did not correlate with PAI-1 activity. In conclusion, the activation of plasminogen measured as PAP was higher in patients with bleeding symptoms in combination with PAI-1 activity less than 1.0 U/ml than in those with PAI-1 activity of at least 1.0 U/ml. The coagulation activity under normal conditions, as measured by D-dimer, did not differ between the two patient subsets. The results support our previous definition of low PAI-1 as activity below 1.0 U/ml.

Whole blood coagulation assays ROTEM and T-TAS to monitor dabigatran treatment

BACKGROUND A rapid and reliable assessment of the dabigatran effect is desirable in dabigatran treated patients with uncontrolled bleeding or before acute surgery. OBJECTIVE To evaluate how the viscoelastic point-of-care test Rotational thromboelastometry (ROTEM) and Total Thrombus-formation system (T-TAS), which studies thrombus formation under flowing conditions, correlate with dabigatran concentrations in patients with atrial fibrillation (AF). METHOD ROTEM using the reagents In-tem, Ex-tem, Fib-tem or low tissue factor concentration (TF), and T-TAS with the AR-chip (shear rate 600s-1, representing flow in large arteries) were investigated in whole blood samples. Plasma concentrations were determined by mass spectrometry (LC-MS/MS) at trough and post-dose in 30 patients on dabigatran 150mg BID. RESULTS Median plasma dabigatran concentrations at trough were 86ng/mL (29-150) and post-dose (2.8h after ingestion) 175ng/mL (67-490). The ROTEM clotting time (CT) correlated strongly with dabigatran concentrations when activated with the reagents Ex-tem (r=0.92, p<0.01) and Fib-tem (r=0.93, p<0.01), while with In-tem and low TF the correlation was weaker (r=0.72 and r=0.36, p<0.01). There were significant but weaker correlations also between dabigatran concentrations and T-TAS variables (r-values 0.39-0.41, p<0.01), aPTT (r=0.70, p<0.01) and PT-INR (r=0.43, p<0.01) respectively. CONCLUSIONS ROTEM Ex-tem and Fib-tem CT shows a strong correlation with dabigatran concentrations in real-life AF-patients, and results are obtained within minutes. This could make ROTEM useful in acute situations. T-TAS detect differences in hemostasis caused by dabigatran, but the relationships to plasma concentrations of dabigatran are weaker than for ROTEM CT with the settings used in this study.

In vitro combinations of red blood cell, plasma and platelet components evaluated by thromboelastography

BACKGROUND Thromboelastography is increasingly used to evaluate coagulation in massively bleeding patients. The aim of this study was to investigate how different combinations of blood components affect in vitro whole blood clotting measured by thromboelastography. MATERIALS AND METHODS Packed red blood cells, plasma and platelets from fresh and old blood components were mixed in vitro, in proportions of 4:4:1, 5:5:2, 8:4:1 and 2:1:0, and analysed with thromboelastography. For the ratio 4:4:1 the experiment was done at both 37 °C and 32 °C. RESULTS Thromboelastography curves were within normal reference values for the blood component proportions of 4:4:1 and 5:5:2. For 8:4:1, the angle and maximal amplitude were reduced below normal values, indicating low levels of fibrinogen and/or platelets. For the 2:1:0 proportion, all parameters were affected resulting in severely impaired in vitro clot formation. The reaction-time, reflecting the coagulation factor-dependent, initial clot formation, was slightly increased at a low temperature. Prolonged storage of the components did not affect the curve. DISCUSSION With the introduction of guidelines on the management of massive bleeding it is important to have tools for the assessment of the new protocols. In vitro evaluation of mixtures of packed red blood cells, plasma and platelets by thromboelastography may be relevant in the prediction of in vivo clot formation and haemostasis.