Study of Alteplase for Respiratory Failure in SARS-CoV-2 COVID-19: A Vanguard Multicenter, Rapidly Adaptive, Pragmatic, Randomized Controlled Trial

Nebulized alteplase in coronavirus disease 2019 pneumonia: a case series

BACKGROUND

Many patients with severe coronavirus disease 2019 pneumonia exhibit signs of microthrombosis. Previous studies discussed intravenous fibrinolytic agents as potential add-on therapy in these patients. Therefore, we propose the inhalative administration of fibrinolytics as a possible safer alternative.

CASE PRESENTATION

This case series describes five white male patients, aged 51-78 years, treated with off-label inhalation of alteplase between November and December 2020. All patients suffered from severe severe acute respiratory syndrome coronavirus 2 infection with respiratory failure. Pulmonary embolism was ruled out by pulmonary angiogram in computed tomography scans, and all patients showed signs of coronavirus disease 2019 pneumonia. Four patients improved clinically, while one patient with advanced chronic diseases died due to multiple organ failure. No directly associated adverse effects were observed following inhalation of alteplase.

CONCLUSION

This case series warrants further attention to investigate inhalative alteplase as an additional treatment in patients with severe coronavirus disease 2019 infection.

Efficacy of COVID-19 Treatments in Intensive Care Unit: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Objectives: Examining the cumulative evidence from randomized controlled trials (RCTs), evaluating the use of pharmacological agents for the treatment of COVID-19 infections in patients with critical illness. Data Sources: Databases Medline, Embase, Web of Science, Scopus, CINAHL, and Cochrane. Study Selection: Inclusion criteria were RCTs that enrolled patients with confirmed or suspected COVID-19 infection who are critically ill. Only RCTs that examined therapeutic agents against one another or no intervention, placebo, or standard of care, were included. Data Extraction: Pairs of reviewers extracted data independently. Outcomes of interest included the overall reported mortality defined as either the ICU mortality, hospital mortality, mortality within 28 days or mortality within 90 days. Data Synthesis: A total of 40 studies (11,613 patients) evaluated 50 therapeutic intervention arms divided into five main therapy categories; steroids, antiviral medications, immunomodulators, plasma therapies [intravenous immunoglobulins (IVIG), convalescent plasma and/or, therapeutic plasma exchange], and therapeutic anticoagulation. Immunomodulators was the only group with possible mortality benefit, risk ratio (RR) 0.83 (95% CI 0.73; 0.95), with nonsignificant heterogeneity (I 2 = 8%, p=0.36). In contrast, the other therapy groups showed no significant impact on mortality, as indicated by their respective pooled RRs: steroids [RR 0.91 (95% CI 0.82; 1.01), I 2 = 31%], antiviral medications [RR 1.11 (95% CI 0.82; 1.49), I 2 = 57%], plasma therapies [RR 0.77 (95% CI 0.58; 1.01), I 2 = 36%], and anticoagulation [RR 1.06 (95% CI 0.95; 1.18), I 2 = 0%]. Conclusions: This meta-analysis highlights both the heterogeneity and a lack of benefit from therapies evaluated during the COVID-19 pandemic. Many of the RCTs were developed based on limited observational data. Future RCTs investigating pharmaceutical interventions in critically ill patients during pandemics need to be designed based on better evidence.

Alteplase in COVID-19 severe hypoxemic respiratory failure: the TRISTARDS multicenter randomized trial

BACKGROUND

Pulmonary intravascular thrombus formation has been widely observed in patients with respiratory failure, for example, in patients with SARS-CoV-2 infection (COVID-19). The aim of this study was to evaluate the efficacy/safety of alteplase thrombolysis in COVID-19 severe hypoxemic respiratory failure. In this multicenter, open-label study, patients were randomized to receive alteplase (low- or high-dose) over 5 days plus standard of care (SOC), or SOC alone. The primary endpoint was time to clinical improvement (≥ 2-point decrease on WHO Clinical Progression Scale, or hospital discharge) up to Day 28. Secondary endpoints included all-cause mortality at Day 28, treatment failure at Day 28 and change in arterial oxygen partial pressure/fractional inspired oxygen (PaO2/FiO2) ratio at Day 6 versus baseline.

RESULTS

Sixty-nine patients were randomized to alteplase (low- or high-dose) and 35 to SOC; 65% were on high-flow oxygen or non-invasive ventilation at baseline. Median time to clinical improvement was 25 days in the alteplase group and > 28 days (median not reached) in the SOC group. All-cause mortality was 8/69 (12%) versus 10/35 (29%) in the alteplase versus SOC groups, respectively (unadjusted risk difference [RD], - 17% [95% confidence interval (CI) - 34 to 0], p = 0.047; adjusted RD, - 16% [95% CI - 31 to 1], p = 0.058). The PaO2/FiO2 ratio (mean [standard deviation]) increased by + 30 (84) mmHg in the alteplase group and decreased by - 12 (59) mmHg in the SOC group (adjusted mean difference vs. SOC, p = 0.052). Differences were greater in patients receiving high-dose alteplase, and in those not receiving invasive ventilation. Eighteen patients (26.1%) in the alteplase group discontinued treatment due to adverse events. Major bleeding was more frequent with alteplase than with SOC (9 vs. 0 patients); no bleeding was fatal. The study closed early due to insufficient patient recruitment.

CONCLUSION

Alteplase was not associated with faster clinical recovery from COVID-19 severe hypoxemic respiratory failure. A numerical difference in survival and PaO2/FiO2 ratio was observed, particularly in patients not receiving invasive ventilation. These exploratory findings merit further investigation in larger patient cohorts that are adequately powered to confirm the hypotheses generated in this study regarding the impact of alteplase on treatment outcomes. Trial registration ClinicalTrials.gov: NCT04640194 (November 23, 2020); https://clinicaltrials.gov/study/NCT04640194 (early discontinuation due to insufficient patient recruitment).

Anticoagulant therapy in adult with COVID-19: a systematic review and meta-analysis of randomized controlled trial

Background

Blood coagulation dysfunction is a risk factor for adverse outcomes in patients with coronavirus disease 2019 (COVID-19), especially in severe cases. The evidence for the effects of anticoagulation therapy on prognosis of COVID-19 patients and its risk of causing bleeding events is accumulating. Here we conducted a meta-analysis to assess the efficacy and safety of anticoagulants in COVID-19 patients of different severity.

Methods

We searched PubMed, Embase databases, Cochrane Trials, OVID MEDLINE from December 2019 to April 2023. We included randomized controlled trials (RCTs) involving COVID-19 patients over 18 years of age, which explored the effect of anticoagulant and its dose on outcomes including all-cause mortality, bleeding events or thrombotic events. We calculated the risk ratio (RR) and its 95% confidence interval (CI) for each outcome. We also performed subgroup analyses to assess the impact of disease severity, using a fixed-effect model to test for heterogeneity. The risk of bias, publication bias, and the quality of evidence were also evaluated.

Results

A total of 20 RCTs were included for final analysis. When compared with standard care, anticoagulation treatment reduced all-cause mortality (RR 0.47, 95% CI: 0.29-0.76) and thrombotic events (RR 0.35, 95% CI: 0.15-0.83) in the whole population with COVID-19 (n=2,365), without increase in bleeding events (total: RR 1.47, 95% CI: 0.54-4.00). Most of the studies only enrolled non-severe patients (n=2,329), while the number of severe patients (n=36) was scarce. In RCTs compared therapeutical and prophylactic doses of anticoagulants, no significant difference in on all-cause mortality was found in the whole population and non-severe and severe subgroups (total: RR 1.01, 95% CI: 0.92-1.10; non-severe: RR 1.03, 95% CI: 0.81-1.32; severe: RR 1.00, 95% CI: 0.91-1.11). Therapeutical dose reduced risk of thrombotic events (total: RR 0.59, 95% CI: 0.48-0.73; subtotal of non-severe: RR 0.57, 95% CI: 0.39-0.84; Subtotal of severe: RR 0.61, 95% CI: 0.47-0.78), while risk of bleeding was increased (total: RR 1.98, 95% CI: 1.47-2.66; non-severe: RR 2.38, 95% CI: 1.56-3.62; severe: RR 1.63, 95% CI: 1.07-2.47). Study heterogeneity was found only in the analysis of effects of anticoagulants on risk of thrombotic events.

Conclusions

Anticoagulant therapy reduces all-cause mortality and risk of thrombosis in non-severe COVID-19 patients. Therapeutic dose of anticoagulant therapy can be considered in both non-severe and severe COVID-19 patients to reduce thrombosis, but may be associated with increased bleeding events.

Fibrinolysis Resistance After Injury Is a Risk Factor for a Hospital-Acquired Pneumonia-Like Disease Pattern

Background: Pneumonia is associated with increased morbidity and costs in the intensive care unit (ICU). Its early identification is key for optimal outcomes, but early biomarkers are lacking. Studies suggest that fibrinolysis resistance (FR) after major abdominal surgery is linked to an increased risk of infection. Patients and Methods: Patients in a randomized controlled trial for hemorrhagic shock were evaluated for FR. Fibrinolysis resistance was quantified by thrombelastography with exogenous tissue plasminogen activator (tPA-TEG) at 24- and 48-hours post-injury and measuring LY30 (%). A receiver-operating characteristics (ROC) curve analysis was used to identify a cutoff for increased risk of pneumonia, which was then validated in ICU patients at risk for venous thromboembolism (VTE). Multivariable logistic regression was used to control for confounders. Results: Forty-nine patients in the hemorrhagic shock cohort had tPA-TEGs at 24- and 48-hours (median ISS, 27; 7% pneumonia). A composite tPA-TEG LY30 of less than 4% at 24 and 48 hours was found to be the optimal cutoff for increased risk of pneumonia. This cohort had a seven-fold increased rate of pneumonia (4% vs. 28%; p = 0.048). Eighty-eight patients in the VTE cohort had tPA-TEGs at 24 and 48 hours post-ICU admission (median ISS, 28; 6% pneumonia). The tPA-TEG LY30 of less than 4% was associated with a 10-fold increased rate of pneumonia (19% vs. 1.5%; p = 0.002). In patients with traumatic brain injury, the same association was found (33% vs. 3.2%; p = 0.006). Adjusting for confounders, the tPA-TEG persisted as a substantial risk factor for pneumonia (adjusted odds ratio [OR], 35.7; 95% confidence interval [CI], 1.9-682; p = 0.018). Conclusions: Fibrinolysis resistance quantified by tPA-TEG within 48 hours of ICU admission is associated with an increased risk of pneumonia in patients in hemorrhagic shock and those at risk for VTE. Prospective validation of the tPA-TEG LY30 optimal cutoff for pneumonia and further investigation into whether endogenous FR is a cause of an altered immunity is warranted.

Investigational pharmacological agents for the treatment of ARDS

INTRODUCTION

Acute Respiratory Distress Syndrome (ARDS) is a heterogeneous form of lung injury with severe hypoxemia and bilateral infiltrates after an inciting event that results in diffuse lung inflammation with a high mortality rate. While research in COVID-related ARDS has resulted in several pharmacotherapeutic agents that have undergone successful investigation, non-COVID ARDS studies have not resulted in many widely accepted pharmacotherapeutic agents despite exhaustive research.

AREAS COVERED

The aim of this review is to discuss adjuvant pharmacotherapies targeting non-COVID Acute Lung Injury (ALI)/ARDS and novel therapeutics in COVID associated ALI/ARDS. In ARDS, variable data may support selective use of neuromuscular blocking agents, corticosteroids and neutrophil elastase inhibitors, but are not yet universally used. COVID-ALI/ARDS has data supporting the use of IL-6 monoclonal antibodies, corticosteroids, and JAK inhibitor therapy.

EXPERT OPINION

Although ALI/ARDS modifying pharmacological agents have been identified in COVID-related disease, the data in non-COVID ALI/ARDS has been less compelling. The increased use of more specific molecular phenotyping based on physiologic parameters and biomarkers, will ensure equipoise between groups, and will likely allow more precision in confirming pharmacological agent efficacy in future studies.

Tenecteplase With Concomitant Anticoagulation for Acute Respiratory Failure in Patients With COVID-19: A Randomized Controlled Trial

Background Pulmonary thrombosis and thromboembolism play a significant role in the physiologic derangements seen in COVID-19 acute respiratory failure. The effect of thrombolysis with tenecteplase on patient outcomes is unknown. Methods We conducted a randomized, controlled, double-blind, phase II trial comparing tenecteplase versus placebo in patients with COVID-19 acute respiratory failure (NCT04505592). Patients with COVID-19 acute respiratory failure were randomized to tenecteplase 0.25 mg/kg or placebo in a 2:1 proportion. Both groups received therapeutic heparin for at least 72 hours. Results Thirteen patients were included in the trial. Eight patients were randomized to tenecteplase and five were randomized to placebo. At 28 days, 63% (n = 5) of patients assigned to the treatment group were alive and free from respiratory failure compared to 40% (n = 2) in the placebo arm (p = 0.43). Mortality at 28 days was 25% (n = 2) in the treatment arm and 20% (n = 1) in the control arm (p = 1.0). No patients in the treatment arm developed renal failure by 28 days compared to 60% (n = 3) in the placebo arm (p = 0.07). Major bleeding occurred in 25% (n = 2) of the treatment arm and 20% (n = 1) in the placebo arm; however, no patients in either arm experienced intracranial hemorrhage. Conclusions Tenecteplase with concomitant heparin may improve patient outcomes in patients with COVID-19 respiratory failure. As this study was limited by a small sample size, larger confirmatory studies are needed.

Early predictors of prolonged intensive care utilization following liver transplantation

INTRODUCTION

Creatinine, bilirubin, and fibrinolysis resistance are associated with multi-organ dysfunction and likely risk factors for prolonged intensive care unit (pICU) stay following liver transplantation (LT). We hypothesize postoperative day-1 (POD-1) labs will predict pICU.

METHODS

LT recipients had clinical laboratories and viscoelastic testing with tissue plasminogen activator thrombelastography (tPA TEG) to quantify fibrinolysis resistance (LY30) on POD-1. pICU was defined as one week or longer in the ICU. Logistic regression was used to identify the relationship between POD-1 labs and pICU.

RESULTS

Of 304 patients, 50% went to the ICU, with 15% experiencing pICU. Elevated creatinine (OR 6.6, P ​< ​0.001) and low tPA TEG LY30 (OR 3.7, P ​= ​0.004) were independent predictors of pICU after controlling for other risk factors. A 9-fold increase in the rate of 90-day graft loss (19% vs 2% p ​< ​0.001) was observed patients who had these risk factors for pICU.

CONCLUSION

Elevated creatine and fibrinolysis resistance are associated with pICU and poor outcomes following LT.

Nebulized Recombinant Tissue Plasminogen Activator (rt-PA) for Acute COVID-19-Induced Respiratory Failure: An Exploratory Proof-of-Concept Trial

Acute lung injury in COVID-19 results in diffuse alveolar damage with disruption of the alveolar-capillary barrier, coagulation activation, alveolar fibrin deposition and pulmonary capillary thrombi. Nebulized recombinant tissue plasminogen activator (rt-PA) has the potential to facilitate localized thrombolysis in the alveolar compartment and improve oxygenation. In this proof-of-concept safety study, adults with COVID-19-induced respiratory failure and a <300 mmHg PaO2/FiO2 (P/F) ratio requiring invasive mechanical ventilation (IMV) or non-invasive respiratory support (NIRS) received nebulized rt-PA in two cohorts (C1 and C2), alongside standard of care, between 23 April-30 July 2020 and 21 January-19 February 2021, respectively. Matched historical controls (MHC; n = 18) were used in C1 to explore efficacy. Safety co-primary endpoints were treatment-related bleeds and <1.0-1.5 g/L fibrinogen reduction. A variable dosing strategy with clinical efficacy endpoint and minimal safety concerns was determined in C1 for use in C2; patients were stratified by ventilation type to receive 40-60 mg rt-PA daily for ≤14 days. Nine patients in C1 (IMV, 6/9; NIRS, 3/9) and 26 in C2 (IMV, 12/26; NIRS, 14/26) received nebulized rt-PA for a mean (SD) of 6.7 (4.6) and 9.1(4.6) days, respectively. Four bleeds (one severe, three mild) in three patients were considered treatment related. There were no significant fibrinogen reductions. Greater improvements in mean P/F ratio from baseline to study end were observed in C1 compared with MHC (C1; 154 to 299 vs. MHC; 154 to 212). In C2, there was no difference in the baseline P/F ratio of NIRS and IMV patients. However, a larger improvement in the P/F ratio occurred in NIRS patients (NIRS; 126 to 240 vs. IMV; 120 to 188) and fewer treatment days were required (NIRS; 7.86 vs. IMV; 10.5). Nebulized rt-PA appears to be well-tolerated, with a trend towards improved oxygenation, particularly in the NIRS group. Randomized clinical trials are required to demonstrate the clinical effect significance and magnitude.

Acute respiratory distress syndrome: potential of therapeutic interventions effective in treating progression from COVID-19 to treat progression from other illnesses-a systematic review

BACKGROUND

Acute respiratory distress syndrome (ARDS) is the most severe form of lung injury, rendering gaseous exchange insufficient, leading to respiratory failure. Despite over 50 years of research on the treatment of ARDS when developed from illnesses such as sepsis and pneumonia, mortality remains high, and no robust pharmacological treatments exist. The progression of SARS-CoV-2 infections to ARDS during the recent global pandemic led to a surge in the number of clinical trials on the condition. Understandably, this explosion in new research focused on COVID-19 ARDS (CARDS) rather than ARDS when developed from other illnesses, yet differences in pathology between the two conditions mean that optimal treatment for them may be distinct.

AIM

The aim of the present work is to assess whether new therapeutic interventions that have been developed for the treatment of CARDS may also hold strong potential in the treatment of ARDS when developed from other illnesses. The study objectives are achieved through a systematic review of clinical trials.

RESULTS

The COVID-19 pandemic led to the identification of various therapeutic interventions for CARDS, some but not all of which are optimal for the management of ARDS. Interventions more suited to CARDS pathology include antithrombotics and biologic agents, such as cytokine inhibitors. Cell-based therapies, on the other hand, show promise in the treatment of both conditions, attributed to their broad mechanisms of action and the overlap in the clinical manifestations of the conditions. A shift towards personalised treatments for both CARDS and ARDS, as reflected through the increasing use of biologics, is also evident.

CONCLUSIONS

As ongoing CARDS clinical trials progress, their findings are likely to have important implications that alter the management of ARDS in patients that develop the condition from illnesses other than COVID-19 in the future.

Impact of Alteplase on Mortality in Critically Ill Patients with COVID-19 and Pulmonary Embolism

COVID-19 is an independent risk factor for pulmonary embolism (PE). Little is known about alteplase therapy in this patient group. A retrospective study analyzed 74 patients with PE and acute respiratory distress syndrome (ARDS) due to COVID-19 who were hospitalized in the intensive care unit in 2021. Patients with or without confirmed right heart thrombi (RHT) were treated with unfractionated heparin or alteplase. The mortality rate in patients with RHT treated with heparin was 100% compared to 37.9% and 55.2% in those treated with alteplase without RHT and alteplase with RHT, respectively. The risk of death in the alteplase group increased with delayed thrombolysis (p = 0.009, odds ratio (OR) = 1.73 95% CI (confidence interval) 1.14-2.62), increased D-dimer concentration (p = 0.02, OR = 1.43 95% CI 1.06-1.93), and decreased PaO₂/FiO₂ ratio (p = 0.001, OR = 0.56 95% CI 0.41-0.78). The receiver operating characteristic method determined that a 1-day delay in thrombolytic treatment, D-dimer concentration >5.844 mg/L, and PaO₂/FiO₂ <144 mmHg predicted a fatal outcome. The risk of death in patients with severe COVID-19 with ARDS and PE increases with higher D-dimer levels, decreased PaO₂/FiO₂, and delayed thrombolytic treatment. Thrombolysis seems to be treatment of choice in severe COVID-19 with PE and RHT. It should be carried out as soon as possible after the diagnosis is established.

All tangled up: interactions of the fibrinolytic and innate immune systems

The hemostatic and innate immune system are intertwined processes. Inflammation within the vasculature promotes thrombus development, whilst fibrin forms part of the innate immune response to trap invading pathogens. The awareness of these interlinked process has resulted in the coining of the terms "thromboinflammation" and "immunothrombosis." Once a thrombus is formed it is up to the fibrinolytic system to resolve these clots and remove them from the vasculature. Immune cells contain an arsenal of fibrinolytic regulators and plasmin, the central fibrinolytic enzyme. The fibrinolytic proteins in turn have diverse roles in immunoregulation. Here, the intricate relationship between the fibrinolytic and innate immune system will be discussed.

Fibrinolytic system and COVID-19: From an innovative view of epithelial ion transport

Lifeways of worldwide people have changed dramatically amid the coronavirus disease 2019 (COVID-19) pandemic, and public health is at stake currently. In the early stage of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, fibrinolytic system is mostly inhibited, which is responsible for the development of hypofibrinolysis, promoting disseminated intravascular coagulation, hyaline membrane formation, and pulmonary edema. Whereas the common feature and risk factor at advanced stage is a large amount of fibrin degradation products, including D-dimer, the characteristic of hyperfibrinolysis. Plasmin can cleave both SARS-CoV-2 spike protein and γ subunit of epithelial sodium channel (ENaC), a critical element to edematous fluid clearance. In this review, we aim to sort out the role of fibrinolytic system in the pathogenesis of COVID-19, as well as provide the possible guidance in current treating methods. In addition, the abnormal regulation of ENaC in the occurrence of SARS-CoV-2 mediated hypofibrinolysis and hyperfibrinolysis are summarized, with the view of proposing an innovative view of epithelial ion transport in preventing the dysfunction of fibrinolytic system during the progress of COVID-19.

Therapeutic considerations for prevention and treatment of thrombotic events in COVID-19

Thrombosis is a known complication of SARS-CoV-2 infection, particularly within a severely symptomatic subset of patients with COVID-19 disease, in whom an aggressive host immune response leads to cytokine storm syndrome (CSS). The incidence of thrombotic events coinciding with CSS may contribute to the severe morbidity and mortality observed in association with COVID-19. This review provides an overview of pharmacologic approaches based upon an emerging understanding of the mechanisms responsible for thrombosis across a spectrum of COVID-19 disease involving an interplay between immunologic and pro-thrombotic events, including endothelial injury, platelet activation, altered coagulation pathways, and impaired fibrinolysis.

Point-of-care diagnosis and monitoring of fibrinolysis resistance in the critically ill: results from a feasibility study

BACKGROUND

Fibrinolysisis is essential for vascular blood flow maintenance and is triggered by endothelial and platelet release of tissue plasminogen activator (t-PA). In certain critical conditions, e.g. sepsis, acute respiratory failure (ARF) and trauma, the fibrinolytic response is reduced and may lead to widespread thrombosis and multi-organ failure. The mechanisms underpinning fibrinolysis resistance include reduced t-PA expression and/or release, reduced t-PA and/or plasmin effect due to elevated inhibitor levels, increased consumption and/or clearance. This study in critically ill patients with fibrinolysis resistance aimed to evaluate the ability of t-PA and plasminogen supplementation to restore fibrinolysis with assessment using point-of-care ClotPro viscoelastic testing (VET).

METHODS

In prospective, observational studies, whole-blood ClotPro VET evaluation was carried out in 105 critically ill patients. In 32 of 58 patients identified as fibrinolysis-resistant (clot lysis time > 300 s on the TPA-test: tissue factor activated coagulation with t-PA accelerated fibrinolysis), consecutive experimental whole-blood VET was carried out with repeat TPA-tests spiked with additional t-PA and/or plasminogen and the effect on lysis time determined. In an interventional study in a patient with ARF and fibrinolysis resistance, the impact of a 24 h intravenous low-dose alteplase infusion on coagulation and fibrinolysis was prospectively monitored using standard ClotPro VET.

RESULTS

Distinct response groups emerged in the ex vivo experimental VET, with increased fibrinolysis observed following supplementation with (i) t-PA only or (ii) plasminogen and t-PA. A baseline TPA-test lysis time of > 1000 s was associated with the latter group. In the interventional study, a gradual reduction (25%) in serial TPA-test lysis times was observed during the 24 h low-dose alteplase infusion.

CONCLUSIONS

ClotPro viscoelastic testing, the associated TPA-test and the novel experimental assays may be utilised to (i) investigate the potential mechanisms of fibrinolysis resistance, (ii) guide corrective treatment and (iii) monitor in real-time the treatment effect. Such a precision medicine and personalised treatment approach to the management of fibrinolysis resistance has the potential to increase treatment benefit, while minimising adverse events in critically ill patients.

TRIAL REGISTRATION

VETtiPAT-ARF, a clinical trial evaluating ClotPro-guided t-PA (alteplase) administration in fibrinolysis-resistant patients with ARF, is ongoing (ClinicalTrials.gov NCT05540834 ; retrospectively registered September 15th 2022).

Electrical Impedance Tomography As a Bedside Diagnostic Tool for Pulmonary Embolism

Electrical impedance tomography (EIT) has been shown to be of value in evaluating the distribution of ventilation. In addition, several studies, particularly case reports, have demonstrated the use of EIT in the assessment of lung perfusion. EIT may be a potential diagnostic bedside tool in the diagnosis and follow-up of acute pulmonary embolism.

CASE SUMMARY

We present one case of a patient with COVID-19 who likely had pulmonary thromboembolism where perfusion scans were made before and after thrombolytic therapy. Perfusion scans showed improvement after thrombolytic therapy. This article should therefore be seen as a first step in proving the validity of EIT-derived perfusion scans as a diagnostic for pulmonary embolism.

CONCLUSION

The hypertonic saline bolus EIT method as a diagnostic tool for pulmonary embolism is a promising new technique, which can be particularly meaningful for critically ill patients. Further study is required to evaluate the sensitivity and specificity of this technique and the impact on decision-making and outcomes of critically ill patients.

Fibrinolytic therapy in patients with COVID-19 and ARDS: protocol for a systematic review and meta-analysis

INTRODUCTION

In COVID-19-related acute respiratory distress syndrome (ARDS), the clot play a role in gas exchange abnormalities. Fibrinolytic therapy can improve alveolar ventilation by restoring blood flow. In this systematic review and meta-analysis protocol, we aim to assess the safety and efficacy of fibrinolytic therapy in such a population.

METHODS

We will perform a systematic search in MEDLINE, EMBASE, Cochrane CENTRAL and LILACS databases without language restrictions for relevant randomised controlled trials (RCTs) and quasi-RCTs. Two review authors will independently perform data extraction and quality assessments of data from included studies. In case of divergence, a third author will be contacted. The Cochrane handbook will be used for guidance. If the results are not appropriate for a meta-analysis, a descriptive analysis will be performed.

DISCUSSION

This systematic review and meta-analysis protocol will provide current evidence about the safety and efficacy of fibrinolytic therapy in patients with COVID-19 and ARDS. These findings will provide if fibrinolytic therapy might be an option for a desperate clinical setting, where all medical efforts have been used.

PROSPERO REGISTRATION NUMBER

PROSPERO CRD42020187482.

ETHICS AND DISSEMINATION

Ethics committee approval is not necessary. We intend to update the public registry, report any protocol amendments and publish the results in a widely accessible journal.

The potential impact of nanomedicine on COVID-19-induced thrombosis

Extensive reports of pulmonary embolisms, ischaemic stroke and myocardial infarctions caused by coronavirus disease 2019 (COVID-19), as well as a significantly increased long-term risk of cardiovascular diseases in COVID-19 survivors, have highlighted severe deficiencies in our understanding of thromboinflammation and the need for new therapeutic options. Due to the complexity of the immunothrombosis pathophysiology, the efficacy of treatment with conventional anti-thrombotic medication is questioned. Thrombolytics do appear efficacious, but are hindered by severe bleeding risks, limiting their use. Nanomedicine can have profound impact in this context, protecting delicate (bio)pharmaceuticals from degradation en route and enabling delivery in a targeted and on demand manner. We provide an overview of the most promising nanocarrier systems and design strategies that may be adapted to develop nanomedicine for COVID-19-induced thromboinflammation, including dual-therapeutic approaches with antiviral and immunosuppressants. Resultant targeted and side-effect-free treatment may aid greatly in the fight against the ongoing COVID-19 pandemic.

Plasma biomarkers associated with survival and thrombosis in hospitalized COVID-19 patients

Severe coronavirus disease-19 (COVID-19) has been associated with fibrin-mediated hypercoagulability and thromboembolic complications. To evaluate potential biomarkers of coagulopathy and disease severity in COVID-19, we measured plasma levels of eight biomarkers potentially associated with coagulation, fibrinolysis, and platelet function in 43 controls and 63 COVID-19 patients, including 47 patients admitted to the intensive care unit (ICU) and 16 non-ICU patients. COVID-19 patients showed significantly elevated levels of fibrinogen, tissue plasminogen activator (t-PA), and its inhibitor plasminogen activation inhibitor 1 (PAI-1), as well as ST2 (the receptor for interleukin-33) and von Willebrand factor (vWF) compared to the control group. We found that higher levels of t-PA, ST2, and vWF at the time of admission were associated with lower survival rates, and that thrombotic events were more frequent in patients with initial higher levels of vWF. These results support a predictive role of specific biomarkers such as t-PA and vWF in the pathophysiology of COVID-19. The data provide support for the case that hypercoagulability in COVID-19 is fibrin-mediated, but also highlights the important role that vWF may play in the genesis of thromboses in the pathophysiology of COVID-19. Interventions designed to enhance fibrinolysis might prove to be useful adjuncts in the treatment of coagulopathy in a subset of COVID-19 patients.

Fibrinolysis in COVID-19: Impact on Clot Lysis and Modulation of Inflammation

COVID-19 is a multisystem disease caused by SARS-CoV-2 and is associated with an imbalance between the coagulation and fibrinolytic systems. Overall, hypercoagulation, hypofibrinolysis and fibrin-clot resistance to fibrinolysis predispose patients to thrombotic and thromboembolic events. In the lungs, the virus triggers alveolar and interstitial fibrin deposition, endothelial dysfunction, and pulmonary intravascular coagulation, all events intrinsically associated with the activation of inflammation and organ injury. Adding to the pathogenesis of COVID-19, there is a positive feedback loop by which local fibrin deposition in the lungs can fuel inflammation and consequently dysregulates coagulation, a process known as immunothrombosis. Therefore, fibrinolysis plays a central role in maintaining hemostasis and tissue homeostasis during COVID-19 by cleaning fibrin clots and controlling feed-forward products of coagulation. In addition, components of the fibrinolytic system have important immunomodulatory roles, as evidenced by studies showing the contribution of Plasminogen/Plasmin (Plg/Pla) to the resolution of inflammation. Herein, we review clinical evidence for the dysregulation of the fibrinolytic system and discuss its contribution to thrombosis risk and exacerbated inflammation in severe COVID-19. We also discuss the current concept of an interplay between fibrinolysis and inflammation resolution, mirroring the well-known crosstalk between inflammation and coagulation. Finally, we consider the central role of the Plg/Pla system in resolving thromboinflammation, drawing attention to the overlooked consequences of COVID-19-associated fibrinolytic abnormalities to local and systemic inflammation.

Fibrinogen, Fibrin, and Fibrin Degradation Products in COVID-19

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is the highly pathogenic and highly transmissible human coronavirus that is the causative agent for the worldwide COVID-19 pandemic. COVID-19 manifests predominantly as a respiratory illness with symptoms consistent with viral pneumonia, but other organ systems (e.g., kidney, heart, brain) can also become perturbed in COVID-19 patients. Accumulating data suggest that significant activation of the hemostatic system is a common pathological manifestation of SARS-CoV-2 infection. The clotting protein fibrinogen is one of the most abundant plasma proteins. Following activation of coagulation, the central coagulation protease thrombin converts fibrinogen to fibrin monomers, which selfassemble to form a matrix, the primary structural component of the blood clot. Severe COVID-19 is associated with a profound perturbation of circulating fibrinogen, intra- and extravascular fibrin deposition and persistence, and fibrin degradation. Current findings suggest high levels of fibrinogen and the fibrin degradation product D-dimer are biomarkers of poor prognosis in COVID-19. Moreover, emerging studies with in vitro and animal models indicate fibrin(ogen) as an active player in COVID-19 pathogenesis. Here, we review the current literature regarding fibrin(ogen) and COVID-19, including possible pathogenic mechanisms and treatment strategies centered on clotting and fibrin(ogen) function.

Impaired Fibrinolytic Potential Predicts Oxygen Requirement in COVID-19

Abnormal coagulation and fibrinolysis contributes to the respiratory distress syndrome in COVID-19. We aimed to explore the association of impaired fibrinolytic potential with disease severity and oxygen requirement in hospitalized patients. Adults admitted to hospital with confirmed COVID-19 infection between 1–31 January 2022 were included, corresponding to the first Omicron outbreak in Melbourne, Victoria. The first citrated plasma sample requested within 24 h of the patient’s presentation was obtained and analyzed by the overall hemostatic potential (OHP) assay, a spectrophotometric assay in which fibrin formation (triggered by small amounts of thrombin (OCP)) and fibrinolysis (by the addition of thrombin and tissue plasminogen activator (OHP and OFP%)) were simultaneously measured. There were 266 patients (median 72 years, 52.9% male), of which 49.6% did not require oxygen therapy. COVID-19 severity and requirement for oxygen was significantly associated with higher OCP, OHP, and lower OFP%. Vaccinated individuals compared with non-vaccinated individuals had significantly lower OHP (16.5 vs. 23.1, p = 0.015) and higher OFP (72.0% vs. 65.1%, p = 0.005), as well as significantly lower AST, ferritin, LDH, CRP, and D-dimer. A multivariate model containing OHP was constructed with the outcome of oxygen requirement, with c-statistic of 0.85 (95%CI 0.81–0.90). In this pilot study, we show a significant correlation between OHP results and requirement for oxygen supplementation in hospitalized patients during a period dominated by the Omicron variant. The results were incorporated into a multivariate model that predicted for oxygen requirement, with high discriminative ability.

Understanding COVID-19-associated coagulopathy

COVID-19-associated coagulopathy (CAC) is a life-threatening complication of SARS-CoV-2 infection. However, the underlying cellular and molecular mechanisms driving this condition are unclear. Evidence supports the concept that CAC involves complex interactions between the innate immune response, the coagulation and fibrinolytic pathways, and the vascular endothelium, resulting in a procoagulant condition. Understanding of the pathogenesis of this condition at the genomic, molecular and cellular levels is needed in order to mitigate thrombosis formation in at-risk patients. In this Perspective, we categorize our current understanding of CAC into three main pathological mechanisms: first, vascular endothelial cell dysfunction; second, a hyper-inflammatory immune response; and last, hypercoagulability. Furthermore, we pose key questions and identify research gaps that need to be addressed to better understand CAC, facilitate improved diagnostics and aid in therapeutic development. Finally, we consider the suitability of different animal models to study CAC.

Systemic thrombolytics as rescue therapy for COVID-19 patients with acute respiratory distress syndrome: A retrospective observational study

Background

Coronavirus disease 2019 (COVID-19) pneumonia with severe acute respiratory distress syndrome (ARDS) is often associated with a progressive respiratory failure that is refractory to maximal ventilatory support and other ARDS strategies. Studies show evidence of a hypercoagulable state in COVID-19 patients, including capillary thrombosis and alveolar fibrin deposits which impede normal gas exchange. In this context, thrombolysis is considered as a salvage therapy to rescue critically hypoxemic patients.

Methods

In this retrospective observational study, the efficacy of thrombolysis on outcome of COVID-19 ARDS with respiratory failure was analyzed. Patients with severe ARDS and d-dimer levels of 5 μg/ml or above were initiated on alteplase, as a 25 mg bolus followed by a 25 mg infusion over 22 h. Primary outcome was intensive care unit (ICU) mortality and secondary outcomes were change in PaO2/FiO2 24 h after thrombolysis, avoidance of intubation, ventilator free days (VFD), and ICU and hospital length-of-stay (LOS).

Results

Thirteen out of 34 patients with severe COVID ARDS underwent thrombolysis. They had lower ICU mortality than non-thrombolysed patients (23.1% vs. 71.4%, P = 0.006), greater percentage improvement in PaO2/FiO2 (116% vs. 31.5%, P = 0.002), more VFDs (13 days vs. 0 day, P = 0.004), and lesser requirement for intubation (23.1% vs. 76.2%, P = 0.004). ICU and hospital LOS were similar.

Conclusion

Thrombolysis can be considered as a rescue therapy for nonintubated COVID-19 ARDS patients with severe hypoxemic respiratory failure, who show evidence of a procoagulant state. Larger studies are needed before inclusion into the regular treatment protocol for COVID-19 patients.

Effectiveness and safety of fibrinolytic therapy in critically ill patients with COVID-19 with ARDS: protocol for a prospective meta-analysis

INTRODUCTION

The use of fibrinolytic therapy has been proposed in severe acute respiratory distress syndrome (ARDS). During the COVID-19 pandemic, anticoagulation has received special attention due to the frequent findings of microthrombi and fibrin deposits in the lungs and other organs. Therefore, the use of fibrinolysis has been regarded as a potential rescue therapy in these patients. In this prospective meta-analysis, we plan to synthesise evidence from ongoing clinical trials and thus assess whether fibrinolytic therapy can improve the ventilation/perfusion ratio in patients with severe COVID-19-caused ARDS as compared with standard of care.

METHODS AND ANALYSIS

This protocol was registered in PROSPERO. All randomised controlled trials and prospective observational trials that compare fibrinolytic therapy with standard of care in adult patients with COVID-19 and define their primary or secondary outcome as improvement in oxygenation and/or gas exchange, or mortality will be considered eligible. Safety outcomes will include bleeding event rate and requirement for transfusion. Our search on 25 January 2022 identified five eligible ongoing clinical trials. A formal search of MEDLINE (via PubMed), Embase, CENTRAL will be performed every month to identify published results and to search for further trials that meet our eligibility criteria.

DISSEMINATION

This could be the first qualitative and quantitative synthesis summarising evidence of the efficacy and safety of fibrinolytic therapy in critically ill patients with COVID-19. We plan to publish our results in peer-reviewed journals.

PROSPERO REGISTRATION NUMBER

CRD42021285281.

Advances in the Management of Coagulopathy in Trauma: The Role of Viscoelastic Hemostatic Assays across All Phases of Trauma Care

Uncontrolled bleeding is the leading cause of preventable death following injury. Trauma-induced coagulopathy can manifest as diverse phenotypes ranging from hypocoagulability to hypercoagulability, which can change quickly during the acute phase of trauma care. The major advances in understanding coagulation over the past 25 years have resulted from the cell-based concept, emphasizing the key role of platelets and their interaction with the damaged endothelium. Consequently, conventional plasma-based coagulation testing is not accurate in predicting bleeding and does not provide an assessment of which blood products are indicated. Viscoelastic hemostatic assays (VHA), conducted in whole blood, have emerged as a superior method to guide goal-directed transfusion. The major change in resuscitation has been the shift from unbridled crystalloid loading to judicious balanced blood product administration. Furthermore, the recognition of the rapid changes from hypocoagulability to hypercoagulability has underscored the importance of ongoing surveillance beyond emergent surgery. While the benefits of VHA testing are maximized when used as early as possible, current technology limits use in the pre-hospital setting and the time to results compromises its utility in the emergency department. Thus, most of the reported experience with VHA in trauma is in the operating room and intensive care unit, where there is compelling data to support its value. This overview will address the current and potential role of VHA in the seriously injured patient, throughout the continuum of trauma management.

Case series of nebulizing r-tPA for COVID-19 induced acute respiratory distress syndrome

Fibrin deposition in the alveolar spaces during pulmonary involvement of COVID-19 impairs the O2/CO2 exchange and leads to respiratory symptoms. In this report, Recombinant Tissue Plasminogen Activator (r-tPA) has been nebulized to 3 critically ill COVID-19 patients in order to resolve the deposited fibrin while avoiding the risk of bleeding. Based on these observations, nebulization of r-tPA may be a potential therapeutic approach and new area of research for future studies.

Illustrated State-of-the-Art Capsules of the ISTH 2022 Congress

The ISTH London 2022 Congress is the first held (mostly) face-to-face again since the COVID-19 pandemic took the world by surprise in 2020. For 2 years we met virtually, but this year's in-person format will allow the ever-so-important and quintessential creativity and networking to flow again. What a pleasure and joy to be able to see everyone! Importantly, all conference proceedings are also streamed (and available recorded) online for those unable to travel on this occasion. This ensures no one misses out. The 2022 scientific program highlights new developments in hemophilia and its treatment, acquired and other inherited bleeding disorders, thromboinflammation, platelets and coagulation, clot structure and composition, fibrinolysis, vascular biology, venous thromboembolism, women's health, arterial thrombosis, pediatrics, COVID-related thrombosis, vaccine-induced thrombocytopenia with thrombosis, and omics and diagnostics. These areas are elegantly reviewed in this Illustrated Review article. The Illustrated Review is a highlight of the ISTH Congress. The format lends itself very well to explaining the science, and the collection of beautiful graphical summaries of recent developments in the field are stunning and self-explanatory. This clever and effective way to communicate research is revolutionary and different from traditional formats. We hope you enjoy this article and will be inspired by its content to generate new research ideas.

Cytokines and Lipid Mediators of Inflammation in Lungs of SARS-CoV-2 Infected Mice

Coronavirus disease 19 (COVID-19) is the clinical manifestation of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) infection. A hallmark of COVID-19 is a lung inflammation characterized by an abundant leukocyte infiltrate, elevated levels of cytokines/chemokines, lipid mediators of inflammation (LMI) and microthrombotic events. Animal models are useful for understanding the pathophysiological events leading to COVID-19. One such animal model is the K18-ACE2 transgenic mice. Despite their importance in inflammation, the study of LMI in lung of SARS-CoV-2 infected K18-ACE2 mice has yet to be studied to our knowledge. Using tandem mass spectrometry, the lung lipidome at different time points of infection was analyzed. Significantly increased LMI included N-oleoyl-serine, N-linoleoyl-glycine, N-oleoyl-alanine, 1/2-linoleoyl-glycerol, 1/2-docosahexaenoyl-glycerol and 12-hydroxy-eicosapenatenoic acid. The levels of prostaglandin (PG) E₁, PGF_2α, stearoyl-ethanolamide and linoleoyl-ethanolamide were found to be significantly reduced relative to mock-infected mice. Other LMI were present at similar levels (or undetected) in both uninfected and infected mouse lungs. In parallel to LMI measures, transcriptomic and cytokine/chemokine profiling were performed. Viral replication was robust with maximal lung viral loads detected on days 2-3 post-infection. Lung histology revealed leukocyte infiltration starting on day 3 post-infection, which correlated with the presence of high concentrations of several chemokines/cytokines. At early times post-infection, the plasma of infected mice contained highly elevated concentration of D-dimers suggestive of blood clot formation/dissolution. In support, the presence of blood clots in the lung vasculature was observed during infection. RNA-Seq analysis of lung tissues indicate that SARS-CoV-2 infection results in the progressive modulation of several hundred genes, including several inflammatory mediators and genes related to the interferons. Analysis of the lung lipidome indicated modest, yet significant modulation of a minority of lipids. In summary, our study suggests that SARS-CoV-2 infection in humans and mice share common features, such as elevated levels of chemokines in lungs, leukocyte infiltration and increased levels of circulating D-dimers. However, the K18-ACE2 mouse model highlight major differences in terms of LMI being produced in response to SARS-CoV-2 infection. The potential reasons and impact of these differences on the pathology and therapeutic strategies to be employed to treat severe COVID-19 are discussed.

COVID-19 coagulopathy - what should we treat?

NEW FINDINGS

What is the topic of this review? Overview of the coagulation abnormalities, including elevated D-dimers widely reported with COVID-19, often labelled as COVID coagulopathy. What advances does it highlight? The review highlights the changes in bronchoalveolar haemostasis due to apoptosis of alveolar cells, which contributes to acute lung injury and acute respiratory distress syndrome; the pathophysiological mechanisms, including endothelial dysfunction and damage responsible for thrombosis of pulmonary microcirculation and potential contribution to the hypoxaemia of COVID-19 acute lung injury; and changes in coagulation proteins responsible for the hypercoagulability and increased risk of thrombosis in other venous and arterial beds. The rationale for anticoagulation and fibrinolytic therapies is detailed, and potential confounders that might have led to less than expected improvement in the various randomised controlled trials are considered.

ABSTRACT

Coronavirus disease 19 (COVID-19) causes acute lung injury with diffuse alveolar damage, alveolar-capillary barrier disruption, thrombin generation and alveolar fibrin deposition. Clinically, hypoxaemia is associated with preserved lung compliance early in the disease, suggesting the lack of excessive fluid accumulation typical of other lung injuries. Notably, autopsy studies demonstrate infection of the endothelium with extensive capillary thrombosis distinct from the embolic thrombi in pulmonary arteries. The inflammatory thrombosis in pulmonary vasculature secondary to endothelial infection and dysfunction appears to contribute to hypoxaemia. This is associated with elevated D-dimers and acquired hypercoagulability with an increased risk of deep vein thrombosis. Hypercoagulability is secondary to elevated plasma tissue factor levels, von Willebrand factor, fibrinogen, reduced ADAMTS-13 with platelet activation and inhibition of fibrinolysis. Multi-platform randomised controlled studies of systemic therapeutic anticoagulation with unfractionated and low molecular mass heparins demonstrated a survival benefit over standard care with full-dose anticoagulation in patients with non-severe disease who require supplemental oxygen, but not in severe disease requiring ventilatory support. Late intervention and the heterogeneous nature of enrolled patients can potentially explain the apparent lack of benefit in severe disease. Improvement in oxygenation has been demonstrated with intravenous fibrinolytics in small studies. Inhaled anticoagulants, thrombolytic agents and non-specific proteolytic drugs in clinical trials for decreasing alveolar fibrin deposition might benefit early disease. Essentially, COVID-19 is a multi-system disorder with pulmonary vascular inflammatory thrombosis that requires an interdisciplinary approach to combination therapies addressing both inflammation and intravascular thrombosis or alveolar fibrin deposits to improve outcomes.

Anticoagulant Treatment in Severe ARDS COVID-19 Patients

Patients with COVID-19 may complicate their evolution with thromboembolic events. Incidence of thromboembolic complications are high and also, patients with the critically-ill disease showed evidence of microthrombi and microangiopathy in the lung probably due to endothelial damage by directly and indirectly injured endothelial and epithelial cells. Pulmonary embolism, deep venous thrombosis and arterial embolism were reported in patients with COVID-19, and several analytical abnormal coagulation parameters have been described as well. D-dimer, longer coagulation times and lower platelet counts have been associated with poor outcomes. The use of anticoagulation or high doses of prophylactic heparin is controversial. Despite the use of anticoagulation or high prophylactic dose of heparin have been associated with better outcomes in observational studies, only in patients with non-critically ill disease benefits for anticoagulation was observed. In critically-ill patient, anticoagulation was not associated with better outcomes. Other measures such as antiplatelet therapy, fibrinolytic therapy or nebulized anticoagulants are being studied in ongoing clinical trials.

Immuno-Thrombotic Complications of COVID-19: Implications for Timing of Surgery and Anticoagulation

Early in the coronavirus disease 2019 (COVID-19) pandemic, global governing bodies prioritized transmissibility-based precautions and hospital capacity as the foundation for delay of elective procedures. As elective surgical volumes increased, convalescent COVID-19 patients faced increased postoperative morbidity and mortality and clinicians had limited evidence for stratifying individual risk in this population. Clear evidence now demonstrates that those recovering from COVID-19 have increased postoperative morbidity and mortality. These data-in conjunction with the recent American Society of Anesthesiologists guidelines-offer the evidence necessary to expand the early pandemic guidelines and guide the surgeon's preoperative risk assessment. Here, we argue elective surgeries should still be delayed on a personalized basis to maximize postoperative outcomes. We outline a framework for stratifying the individual COVID-19 patient's fitness for surgery based on the symptoms and severity of acute or convalescent COVID-19 illness, coagulopathy assessment, and acuity of the surgical procedure. Although the most common manifestation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is COVID-19 pneumonitis, every system in the body is potentially afflicted by an endotheliitis. This endothelial derangement most often manifests as a hypercoagulable state on admission with associated occult and symptomatic venous and arterial thromboembolisms. The delicate balance between hyper and hypocoagulable states is defined by the local immune-thrombotic crosstalk that results commonly in a hemostatic derangement known as fibrinolytic shutdown. In tandem, the hemostatic derangements that occur during acute COVID-19 infection affect not only the timing of surgical procedures, but also the incidence of postoperative hemostatic complications related to COVID-19-associated coagulopathy (CAC). Traditional methods of thromboprophylaxis and treatment of thromboses after surgery require a tailored approach guided by an understanding of the pathophysiologic underpinnings of the COVID-19 patient. Likewise, a prolonged period of risk for developing hemostatic complications following hospitalization due to COVID-19 has resulted in guidelines from differing societies that recommend varying periods of delay following SARS-CoV-2 infection. In conclusion, we propose the perioperative, personalized assessment of COVID-19 patients' CAC using viscoelastic hemostatic assays and fluorescent microclot analysis.