Low-Molecular-Weight Heparin Resistance and Its Viscoelastic Assessment in Critically Ill COVID-19 Patients

Critically ill COVID-19 patients present an inflammatory and procoagulant status with a high rate of relevant macro- and microvascular thrombosis. Furthermore, high rates of heparin resistance have been described; yet, individualized anticoagulation by drug monitoring has not been sufficiently researched. We analyzed data from critically ill COVID-19 patients treated at Innsbruck Medical University Hospital with routinely adapted low-molecular-weight heparin (LMWH) doses according to anti-Xa peak levels, and regularly performed ClotPro analyses (a viscoelastic hemostatic whole blood test). A total of 509 anti-Xa peak measurements in 91 patients were categorized as below (<0.008 IU/mL/mg), within (0.008-0-012 IU/mL/mg) or above (> 0.012 IU/mL/mg) expected ranges with respect to the administered LMWH doses. Besides intergroup comparisons, correlations between anti-Xa levels and ClotPro clotting times (CTs) were performed (226 time points in 84 patients). Anti-Xa peak levels remained below the expected range in the majority of performed measurements (63.7%). Corresponding patients presented with higher C-reactive protein and D-dimer but lower antithrombin levels when compared with patients achieving or exceeding the expected range. Consequently, higher enoxaparin doses were applied in the sub-expected anti-Xa range group. Importantly, 47 (51.6%) patients switched between groups during their intensive care unit (ICU) stay. Anti-Xa levels correlated weakly with IN test CT and moderately with Russell's viper venom (RVV) test CT. Critically ill COVID-19 patients present with a high rate of LMWH resistance but with a variable LMWH response during their ICU stay. Therefore, LMWH-anti-Xa monitoring seems inevitable to achieve adequate target ranges. Furthermore, we propose the use of ClotPro's RVV test to assess the coagulation status during LMWH administration, as it correlates well with anti-Xa levels but more holistically reflects the coagulation cascade than anti-Xa activity alone.

First-Line Administration of Fibrinogen Concentrate in the Bleeding Trauma Patient: Searching for Effective Dosages and Optimal Post-Treatment Levels Limiting Massive Transfusion-Further Results of the RETIC Study

Fibrinogen supplementation is recommended for treatment of severe trauma hemorrhage. However, required dosages and aimed for post-treatment fibrinogen levels remain a matter of discussion. Within the published RETIC study, adult patients suffering trauma-induced coagulopathy were randomly assigned to receive fibrinogen concentrate (FC) as first-line (n = 50) or crossover rescue (n = 20) therapy. Depending on bodyweight, a single dose of 3, 4, 5, or 6 g FC was administered and repeated if necessary (FibA10 < 9 mm). The dose-dependent response (changes in plasma fibrinogen and FibA10) was analyzed. Receiver operating characteristics (ROC) analysis regarding the need for massive transfusion and correlation analyses regarding fibrinogen concentrations and polymerization were performed. Median FC single doses amounted to 62.5 (57 to 66.66) mg·kg⁻¹. One FC single-dose sufficiently corrected fibrinogen and FibA10 (median fibrinogen 213 mg·dL⁻¹, median FibA10 11 mm) only in patients with baseline fibrinogen above 100 mg·dL⁻¹ and FibA10 above 5 mm, repeated dosing was required in patients with lower baseline fibrinogen/FibA10. Fibrinogen increased by 83 or 107 mg·dL⁻¹ and FibA10 by 4 or 4.5 mm after single or double dose of FC, respectively. ROC curve analysis revealed post-treatment fibrinogen levels under 204.5 mg·dL⁻¹ to predict the need for massive transfusion (AUC 0.652; specificity: 0.667; sensitivity: 0.688). Baseline fibrinogen/FibA10 levels should be considered for FC dosing as only sufficiently corrected post-treatment levels limit transfusion requirements.

Efficacy of prehospital administration of fibrinogen concentrate in trauma patients bleeding or presumed to bleed (FIinTIC): A multicentre, double-blind, placebo-controlled, randomised pilot study

BACKGROUND

Trauma-induced coagulopathy (TIC) substantially contributes to mortality in bleeding trauma patients.

OBJECTIVE

The aim of the study was to administer fibrinogen concentrate in the prehospital setting to improve blood clot stability in trauma patients bleeding or presumed to bleed.

DESIGN

A prospective, randomised, placebo-controlled, double-blinded, international clinical trial.

SETTING

This emergency care trial was conducted in 12 Helicopter Emergency Medical Services (HEMS) and Emergency Doctors' vehicles (NEF or NAW) and four trauma centres in Austria, Germany and Czech Republic between 2011 and 2015.

PATIENTS

A total of 53 evaluable trauma patients aged at least 18 years with major bleeding and in need of volume therapy were included, of whom 28 received fibrinogen concentrate and 25 received placebo.

INTERVENTIONS

Patients were allocated to receive either fibrinogen concentrate or placebo prehospital at the scene or during transportation to the study centre.

MAIN OUTCOME MEASURES

Primary outcome was the assessment of clot stability as reflected by maximum clot firmness in the FIBTEM assay (FIBTEM MCF) before and after administration of the study drug.

RESULTS

Median FIBTEM MCF decreased in the placebo group between baseline (before administration of study treatment) and admission to the Emergency Department, from a median of 12.5 [IQR 10.5 to 14] mm to 11 [9.5 to 13] mm (P = 0.0226), but increased in the FC Group from 13 [11 to 15] mm to 15 [13.5 to 17] mm (P = 0.0062). The median between-group difference in the change in FIBTEM MCF was 5 [3 to 7] mm (P < 0.0001). Median fibrinogen plasma concentrations in the fibrinogen concentrate Group were kept above the recommended critical threshold of 2.0 g l-1 throughout the observation period.

CONCLUSION

Early fibrinogen concentrate administration is feasible in the complex and time-sensitive environment of prehospital trauma care. It protects against early fibrinogen depletion, and promotes rapid blood clot initiation and clot stability.

TRIAL REGISTRY NUMBERS

EudraCT: 2010-022923-31 and ClinicalTrials.gov: NCT01475344.

A Prospective Pilot Trial to Assess the Efficacy of Argatroban (Argatra®) in Critically Ill Patients with Heparin Resistance

The current study aims to evaluate whether prophylactic anticoagulation using argatroban or an increased dose of unfractionated heparin (UFH) is effective in achieving the targeted activated partial thromboplastin time (aPTT) of more than 45 s in critically ill heparin-resistant (HR) patients. Patients were randomized either to continue receiving an increased dose of UFH, or to be treated with argatroban. The endpoints were defined as achieving an aPTT target of more than 45 s at 7 h and 24 h. This clinical trial was registered on clinicaltrials.gov (NCT01734252) and on EudraCT (2012-000487-23). A total of 42 patients, 20 patients in the heparin and 22 in the argatroban group, were included. Of the patients with continued heparin treatment 55% achieved the target aPTT at 7 h, while only 40% of this group maintained the target aPTT after 24 h. Of the argatroban group 59% reached the target aPTT at 7 h, while at 24 h 86% of these patients maintained the targeted aPTT. Treatment success at 7 h did not differ between the groups (p = 0.1000), whereas at 24 h argatroban showed significantly greater efficacy (p = 0.0021) than did heparin. Argatroban also worked better in maintaining adequate anticoagulation in the further course of the study. There was no significant difference in the occurrence of bleeding or thromboembolic complications between the treatment groups. In the case of heparin-resistant critically ill patients, argatroban showed greater efficacy than did an increased dose of heparin in achieving adequate anticoagulation at 24 h and in maintaining the targeted aPTT goal throughout the treatment phase.

Fibrinogen supplementation ex vivo increasesclot firmness comparable to platelet transfusion in thrombocytopenia

BACKGROUND

Fibrinogen concentrate can improve clot firmness and offers a better safety profile than platelet concentrates. Reduction or avoidance of blood transfusions represents a strategy to reduce associated risks. We investigated whether supplementation of fibrinogen concentrate ex vivo can compensate for clot strength as compared with platelet transfusion in vivo METHODS: One hundred patients in need of platelet transfusion (PT) were enrolled. Blood samples were collected immediately before PT and at 1 h and 24 h after PT. Fibrinogen concentrate was added to these citrated whole blood samples at concentrations of 50, 100, 200 and 400 mg kg^-1 and the maximum clot firmness (MCF) was analysed using ROTEM thromboelastometry.

RESULTS

Fibrinogen supplementation increased MCF significantly and dose-dependently before and after PT. The effect of fibrinogen concentrate (equivalent to doses of 100 and 200 mg kg^-1) ex vivo was comparable to that of PT in vivo, whereas 400 mg kg^-1 fibrinogen significantly improved MCF compared with PT (P < 0.001).

CONCLUSIONS

Fibrinogen concentrate can match the effect of PT on MCF in thrombocytopenia. This potential alternative haemostatic intervention should be evaluated in clinical trials.

Fibrinogen levels in trauma patients during the first seven days after fibrinogen concentrate therapy: a retrospective study

Background

Fibrinogen concentrate (FC) is increasingly used as first line therapy in bleeding trauma patients. It remains unproven whether FC application increases post-traumatic plasma fibrinogen concentration (FIB) in injured patients, possibly constituting a prothrombotic risk. Thus, we investigated the evolution of FIB following trauma in patients with or without FC therapy.

Methods

At the AUVA Trauma Centre, Salzburg, we performed a retrospective study of patients admitted to the emergency room and whose FIB levels were documented thereafter up to day 7 post-trauma. Patients were categorized into those with (treatment group) or without (control group) FC therapy during the first 24 h after hospital admission. A subgroup analysis was carried out to investigate the influence of the amount of FC given.

Results

The study enrolled 435 patients: treatment group, n = 242 (56 %); control group, n = 193 (44 %), with median Injury Severity Score of 34 vs. 22 (P < 0.001) and massive transfusion rate of 18.4 % vs. 0.2 % (P < 0.001). In the treatment group (median FC dose 6 g), FIB was lower on admission and up to day 2 compared with the control group. In patients receiving high (≥10 g) doses of FC, FIB was lower up to day 5 as compared to controls. At other timepoints, FIB did not differ significantly between the groups. In the treatment vs. the control group, other coagulation parameters such as prothrombin time index and platelet count were consistently lower, while activated partial thromboplastin time was consistently prolonged at most timepoints. Inflammatory parameters such as C-reactive protein, interleukin-6 and procalcitonin were generally lower in controls.

Discussion

The rise of FIB levels from day 2 onwards in our study can be attributed to an upregulated fibrinogen synthesis in the liver, occurring in both study groups as part of the acute phase response after tissue injury.

Conclusions

The treatment of severe trauma patients with FC during bleeding management in the first 24 h after hospital admission does not lead to higher FIB levels post-trauma beyond that occurring naturally due to the acute phase response.

Efficacy of argatroban in critically ill patients with heparin resistance: a retrospective analysis

The patients who do not respond even to very high dosages of heparin are assumed to suffer from heparin resistance. The aim of this study was to investigate whether critically ill patients suffering from heparin resistance generally have low antithrombin III (AT) levels, and if the direct thrombin inhibitor argatroban in that case can be an effective option to achieve prophylactic anticoagulation. The study was conducted at the Department for General and Surgical Intensive Care Medicine at the University Hospital Innsbruck. We retrospectively included all patients between 2008 and 2012, who received argatroban because of poor response to high-dosage heparin prophylaxis. The period under observation lasted in total for 9 days, 2 days of anticoagulation with unfractionated heparin (UFH) and 7 days with argatroban. The primary objective was to investigate if after 7 (± 1) hours of switching to argatroban the activated partial thromboplastin time (aPTT) levels were in a prophylactic range of 45 to 55 seconds. Further objectives were to assess the AT level, side effects such as bleeding or thromboembolism, platelet count, correlation between organ function and argatroban dose as well as any need for allogeneic blood products. The study population, consisting of 5 women and 15 men with a mean (± standard deviation, SD) age of 54.6 ± 16.3 years, differed in many clinical aspects. A median (interquartile range) heparin dose of 1,000, 819 to 1,125 IU/h was administered for 2 days and failed in providing a prophylactic anticoagulation measured by the aPTT. The mean aPTT level with heparin treatment was 38.5 seconds (± 4.7) its change within that period was not significant. After switching to argatroban, the mean increase of the aPTT levels in all study patients amounted from 38.5 to 48.3 seconds (p < 0.001). The rise in aPTT clearly reaches sufficient prophylactic anticoagulant levels. The maintenance of prophylactic aPTT levels was achieved over the period of 1 week. There was neither a correlation found between low-AT levels and occurrence of heparin resistance, nor between the simplified acute physiology score II and the administered argatroban dose (r = -0.224, p = 0.342). The results of the present study indicate that argatroban is an effective alternative therapy, especially in critically ill patients, to achieve prophylactic anticoagulation when heparin resistance occurs.