The unique characteristics of COVID-19 coagulopathy

Thrombotic complications and coagulopathy frequently occur in COVID-19. However, the characteristics of COVID-19-associated coagulopathy (CAC) are distinct from those seen with bacterial sepsis-induced coagulopathy (SIC) and disseminated intravascular coagulation (DIC), with CAC usually showing increased D-dimer and fibrinogen levels but initially minimal abnormalities in prothrombin time and platelet count. Venous thromboembolism and arterial thrombosis are more frequent in CAC compared to SIC/DIC. Clinical and laboratory features of CAC overlap somewhat with a hemophagocytic syndrome, antiphospholipid syndrome, and thrombotic microangiopathy. We summarize the key characteristics of representative coagulopathies, discussing similarities and differences so as to define the unique character of CAC.

Involving medical students in service improvement: evaluation of a student-led, extracurricular, multidisciplinary quality improvement initiative

BACKGROUND

Quality improvement (QI) is considered a duty of every doctor and, as such, it is fundamental that medical schools nurture QI skills of medical students. At a London medical school, a novel initiative was designed to involve medical students in QI. Such novel aspects include its student leadership, multidisciplinary approach and extra-curricular nature. The aim of this study is to evaluate the effectiveness of the initiative, and thus add to the experiences of existing medical student QI programs, as well as provide guidance to other institutions wishing to involve medical students in QI.

METHODS

The key features of the initiative's design is described. Its effectiveness was evaluated by the collection of retrospective data on the quality of the initiative's QI projects (QIPs), including the proportion which: 1) reached completion; 2) resulted in a significant improvement in their primary outcome; 3) had sustained results at follow-up; 4) achieved publication; and 5) contributed towards a prize or conference presentation.

RESULTS

There were 109 students involved throughout 10 projects from 14 different undergraduate and postgraduate courses from 2015-2019. 50% of the initiative's projects achieved a significant improvement in their primary outcome, and the proportion of projects which sustained these improvements at follow-up was 100%. Furthermore, 20% of projects were published, and 60% contributed towards a prize or conference presentation.

CONCLUSION

The results of this study show that the initiative was effective at involving medical students in QI. As such, other groups establishing medical student QI programs may benefit from replicating positive elements of its design and operation.

Sepsis-Induced Coagulopathy and Disseminated Intravascular Coagulation

Disseminated intravascular coagulation (DIC) has been recognized as a deadly complication in sepsis, and its early recognition followed by appropriate management of the underlying infection are the current management strategies. The activation of coagulation, inflammation, and other pathways are fundamental host responses against infection but also produce injury to the host. Recent advances have helped define the critical roles of thrombus formation in overcoming infection. In addition to activation of coagulation induced by pathogens, other important pathways including damage-associated molecular patterns, neutrophil extracellular traps, extracellular vesicles, and glycocalyx damage are involved in the pathogenesis of sepsis-induced DIC. The hallmark of DIC is thrombosis in the microvasculature; however, sepsis-induced DIC is a laboratory diagnosis based on coagulation test results and clinical setting. Although simplified criteria were recently introduced, DIC should be distinguished from other similar conditions such as thrombotic microangiopathy and heparin-induced thrombocytopenia. In DIC, treating the underlying cause is crucial, and additional adjunct therapies including antithrombin, thrombomodulin, and heparins may have potential benefit, but evidence supporting their use in terms of improvement of clinically relevant outcomes continues to be debated. In this review, we introduce recent findings regarding the pathophysiology, diagnosis, and treatment of sepsis-induced DIC. In addition, we also discuss future potential therapeutic approaches regarding this complex, life-threatening complication.

Strengths and weaknesses of the acute care systems in the United Kingdom and the Netherlands: what can we learn from each other?

Background

The demand on Emergency Departments and acute medical services is increasing internationally, creating pressure on health systems and negatively influencing the quality of delivered care. Visible consequences of the increased demand on acute services is crowding and queuing. This manifests as delays in the Emergency Departments, adverse clinical outcomes and poor patient experience.

Overview

Despite the similarities in the UK’s and Dutch health care systems, such as universal health coverage, there are differences in the number of patients presenting at the Emergency Departments and the burden of crowding between these countries. Given the similarities in funding, this paper explores the similarities and differences in the organisational structure of acute care in the UK and the Netherlands. In the Netherlands, less patients are seen at the ED than in England and the admission rate is higher. GPs and so-called GP-posts serve 24/7 as gatekeepers in acute care, but EDs are heterogeneously organised. In the UK, the acute care system has a number of different access points and the accessibility of GPs seems to be suboptimal. Acute ambulatory care may relieve the pressure from EDs and Acute Medical Units. In both countries the ageing population leads to a changing case mix at the ED with an increased amount of multimorbid patients with polypharmacy, requiring generalistic and multidisciplinary care.

Conclusion

The acute and emergency care in the Netherlands and the UK face similar challenges. We believe that each system has strengths that the other can learn from. The Netherlands may benefit from an acute ambulatory care system and the UK by optimizing the accessibility of GPs 24/7 and improving signposting for urgent care services. In both countries the changing case mix at the ED needs doctors who are superspecialists instead of subspecialists. Finally, to improve the organisation of health care, doctors need to be visible medical leaders and participate in the organisation of care.

Effect of a Recombinant Human Soluble Thrombomodulin on Mortality in Patients With Sepsis-Associated Coagulopathy: The SCARLET Randomized Clinical Trial

IMPORTANCE

Previous research suggested that soluble human recombinant thrombomodulin may reduce mortality among patients with sepsis-associated coagulopathy.

OBJECTIVE

To determine the effect of human recombinant thrombomodulin vs placebo on 28-day all-cause mortality among patients with sepsis-associated coagulopathy.

DESIGN, SETTING, AND PARTICIPANTS

The SCARLET trial was a randomized, double-blind, placebo-controlled, multinational, multicenter phase 3 study conducted in intensive care units at 159 sites in 26 countries. All adult patients admitted to one of the participating intensive care units between October 2012 and March 2018 with sepsis-associated coagulopathy and concomitant cardiovascular and/or respiratory failure, defined as an international normalized ratio greater than 1.40 without other known etiology and a platelet count in the range of 30 to 150 × 109/L or a greater than 30% decrease in platelet count within 24 hours, were considered for inclusion. The final date of follow-up was February 28, 2019.

INTERVENTIONS

Patients with sepsis-associated coagulopathy were randomized and treated with an intravenous bolus or a 15-minute infusion of thrombomodulin (0.06 mg/kg/d [maximum, 6 mg/d]; n = 395) or matching placebo (n = 405) once daily for 6 days.

MAIN OUTCOME AND MEASURES

The primary end point was 28-day all-cause mortality.

RESULTS

Among 816 randomized patients, 800 (mean age, 60.7 years; 437 [54.6%] men) completed the study and were included in the full analysis set. In these patients, the 28-day all-cause mortality rate was not statistically significantly different between the thrombomodulin group and the placebo group (106 of 395 patients [26.8%] vs 119 of 405 patients [29.4%], respectively; P = .32). The absolute risk difference was 2.55% (95% CI, -3.68% to 8.77%). The incidence of serious major bleeding adverse events (defined as any intracranial hemorrhage; life-threatening bleeding; or bleeding event classified as serious by the investigator, with administration of at least 1440 mL [typically 6 units] of packed red blood cells over 2 consecutive days) was 23 of 396 patients (5.8%) in the thrombomodulin group and 16 of 404 (4.0%) in the placebo group.

CONCLUSIONS AND RELEVANCE

Among patients with sepsis-associated coagulopathy, administration of a human recombinant thrombomodulin, compared with placebo, did not significantly reduce 28-day all-cause mortality.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01598831.

Disseminated Intravascular Coagulation in Cancer: An Update

Cancer often leads to the activation of coagulation, manifesting as disseminated intravascular coagulation (DIC) in its most extreme form. DIC is characterized by systemic intravascular coagulation activation (leading to deposition of intravascular platelets and fibrin) and simultaneous consumption of coagulation proteins and thrombocytes (which may cause bleeding complications). The clinical course of DIC in patients with malignancies is typically less intense compared with DIC complicating alternative clinical settings, including systemic inflammatory responses following infection or traumatic injury. A more slowly proceeding, less fulminant, and widespread hemostatic derangement can remain asymptomatic. Eventually, the ongoing consumption may result in low levels of platelets and coagulation factors, and bleeding complications (frequently localized at the site of the tumor or distant metastases) may be the first clinical manifestation of DIC. An alternative clinical scenario is dominated by thrombotic complications, ranging from clinically manifest vascular thrombosis to microvascular platelet plugs. The main principle of DIC management is adequate treatment of the precipitating disorder; however, there are clinical presentations that may require additional supportive strategies specifically aimed at the amelioration of the coagulopathy.

Hereditary angioedema: Linking complement regulation to the coagulation system

Congenital deficiency of C1 inhibitor, the main inhibitor of the classic complement system pathway, leads to paroxysmal angioedema (hereditary angioedema) that can be debilitating or life-threatening for affected patients. In the past few years many new insights on the pathogenesis of angioedema formation in the presence of low levels of C1 inhibitor has been accumulated. There is a central role for bradykinin that is released upon activation of the kallikrein-kinin system that is insufficiently controlled by adequate levels of C1 inhibitor. As C1 inhibitor also possesses a central regulatory role of other plasma systems, including the contact activation system of coagulation and the plasminogen-plasmin system that governs endogenous fibrinolysis, it is interesting to observe the effects of C1 inhibitor deficiency on activation of these systems and relevance for hemostasis in vivo and thrombo-embolic disease. Interestingly, and despite significant activation of these pathways, C1 inhibitor deficiency is not at all associated with a hemorrhagic tendency or prothrombotic state. New therapeutic options for treatment of C1 inhibitor efficiency have become available in recent years, including various forms of C1 inhibitor concentrate. Restoration of C1 inhibitor levels in patients with hereditary angioedema has not resulted in thrombotic complications or any other relevant disorder associated with the hemostatic system.

Pathogenesis and diagnosis of disseminated intravascular coagulation

Several clinical conditions, in particular those associated with a systemic inflammatory response, can cause some degree of activation of coagulation but when the procoagulant stimulus is sufficiently severe and overcomes the natural anticoagulant mechanisms of coagulation, disseminated intravascular coagulation (DIC) may occur. The clinical manifestations of DIC encompass multiorgan dysfunction caused by fibrin-platelet clots in the microcirculation, and bleeding caused by consumption of platelets and coagulation factors. Molecular mechanisms that play a role in inflammation-induced effects on coagulation have been recognized in much detail. Exposure of blood to tissue factor is the most common trigger, whereas the intravascular coagulation is propagated due to loss of function of physiological anticoagulants and impaired fibrinolysis. In patients with DIC, various abnormalities in routine coagulation parameters may be observed, including thrombocytopenia, prolonged global coagulation assays, or high levels of fibrin split products. In addition, more sophisticated tests for activation of individual factors or pathways of coagulation may point to specific involvement of these components in the pathogenesis of the disorder. A combination of readily available tests is usually sufficient in establishing the diagnosis of DIC, and for this purpose, several scoring algorithms have been developed. Some specific clinical situations may elicit coagulation responses that can be distinguished from DIC or may occur in combination with DIC, including dilutional coagulopathy, liver failure-related coagulation derangement, and thrombotic microangiopathies.

Factor XIa Induced Activation of the Intrinsic Cascade In Vivo

Coagulation factor XI is a glycoprotein of the contact factor system. Its deficiency is associated with a highly variable bleeding tendency, thus a role in relation to hemostasis appears to exist. However, the importance of factor XI for stimulating intrinsic coagulation in vivo has not yet been determined. To study the procoagulant effects of human factor Xla in vivo, we infused the purified enzyme into normal chimpanzees (100 Μg) in the absence or presence of the thrombin inhibitor rec-hirudin (1.0 mg/kg loading dose plus 0.3 mg/kg body wt continuous infusion). Factor Xla elicited an immediate activation of factors IX, X, and prothrombin, as measured by their respective activation fragments. However, whereas the activation of factors IX and X was immediate and shortlasting, (peak increments of 6- and 1.4-fold of baseline at 5 minutes after injection), the conversion of prothrombin gradually increased, reaching a summit of 6-fold baseline values after 60 min, and remaining elevated during the course of the experiments. Thrombin-antithrombin complexes also remained elevated during the study period. In the presence of hirudin, the initial activation of factors IX, X, and prothrombin was unchanged, however the further increment in prothrombin fragment FI+2 was markedly inhibited. These results demonstrate that factor Xla is a potential agonist of the intrinsic cascade in vivo, which activity is enhanced in the presence of thrombin.

Variable Effects of Radiological Contrast Media on Thrombus Growth in a Rabbit Jugular Vein Thrombosis Model

We studied the effect of an ionic high osmolar contrast medium (Ioxitalamate), an ionic low osmolar contrast medium (Ioxaglate) and various nonionic low osmolar contrast media (Iopamidol, Iopromide and Iohexol) on thrombus growth in a rabbit jugular vein thrombosis model. Thrombus growth was determined by the accretion of 125I-labeled fibrinogen onto autologous preformed thrombi in rabbit jugular veins at various time-intervals from 15 min up to 10 h after infusion of the study solution.

The ionic low osmolar contrast medium markedly inhibited thrombus growth whereas all nonionic low osmolar contrast media promoted thrombus growth. The ionic high osmolar contrast medium inhibited thrombus growth, but less than the ionic low osmolar contrast medium. Within the group of nonionic contrast media, the Iopamidol associated promotion of thrombus growth was significantly higher than the Iopromide or Iohexol associated effects. The simultaneous administration of the apparently most potent thrombus growth promoting contrast medium (i.e. Iopamidol) and heparin resulted in complete abolishment of the increase in thrombus growth.

These results support the claims of prothrombotic properties of nonionic as compared to ionic contrast media and could explain the clinically encountered thromboembolic complications after the use of nonionic low osmolar contrast media.

Deep Vein Thrombosis and Fibrinolysis

In the present study 57 consecutive patients with a first episode of venographically proven deep vein thrombosis were investigated to evaluate the release of tissue-type plasminogen activator (t-PA) and of urokinase-type plasminogen activator (u-PA) in response to DDAVP stimulation as well as the resting plasminogen activator inhibitor (PAI) concentration, comparing this to the results obtained in 66 similar patients with a clinical suspicion of thrombosis but with a normal venogram. All assays were performed without knowledge of the patient's status.

Four patients in the deep vein thrombosis-group (7%) had an absent u-PA antigen response upon DDAVP infusion, while a normal response was observed in all control subjects. Patients and controls showed similar increases in t-PA antigen level upon DDAVP. High resting PAI antigen levels were encountered in 5 patients in the deep vein thrombosis-group (9%) and in 6 subjects in the control group (9%).

The results from this controlled study indicate that a defective release of u-PA may occur in patients with deep vein thrombosis and may have pathogenetic significance. Furthermore it is concluded that elevation of PAI levels cannot be considered as a specific risk factor for venous thrombosis.

Additive Effect of the Combined Administration of Low Molecular Weight Heparin and Recombinant Hirudin on Thrombus Growth in a Rabbit Jugular Vein Thrombosis Model

Recombinant Hirudin (r-Hirudin) is a new anticoagulant with specific antithrombin activity independently of antithrombin III. Low molecular weight heparins (LMWH) exert predominantly anti-Xa activity. Therefore, we hypothesized that combined administration of r-Hirudin and LMWH would induce a stronger antithrombotic effect as compared to r-Hirudin administered alone or combined with unfractionated heparin. To assess the effect on thrombus growth, we determined the accretion of l25I-labeled fibrinogen onto autologous non-radioactive thrombi preformed in the jugular veins of rabbits. The rabbits received unfractionated heparin (80 anti-factor Xa U), LMWH (80 anti-factor Xa U) or r-Hirudin (0.3, 5.0 and 10.0 mg/kg) either separately or by combined infusion for a 3 h period.

R-Hirudin reduced the thrombus growth in a dose dependent fashion. The combined administration of 80 anti-Xa U LMWH and r-Hirudin at a dose of 0.3 mg/kg resulted in a stronger antithrombotic effect as compared to the combined infusion of unfractionated heparin and r-Hirudin (thrombus growth: 14.3% ± 6.0 vs 28.9% ± 6.5; p = 0.001). This difference in additive antithrombotic effect of 80 anti-Xa ULMWH versus unfractionated heparin on r-Hirudin was also observed when LMWH was combined with 5.0 mg/kg and 10.0 mg/kg r-Hirudin versus unfractionated heparin combined with r-Hirudin (thrombus growth: 16.4% ± 1.6 vs 29.1% ± 3.9; p = 0.01 and 10.1% ± 1.8 vs 20.4% ± 4.5; p = 0.001, respectively).

In conclusion, this study showed an additive antithrombotic effect of LMWH on the thrombus growth reducing effect of r-Hirudin. This may potentially be of clinical interest, i. e. much lower doses of r-Hirudin may be used to achieve a similar effective anticoagulant effect when combined with LMWH.

Additive Effect of dDAVP and Standard Heparin inIncreasing Plasma t-PA

The aim of this study was to evaluate the existence of an additive effect between standard heparin and dDAVP in the enhancement of endogenous fibrinolysis. Eight healthy volunteers were studied in a randomized double blind placebo controlled cross-over trial. The volunteers were treated i. v. with dDAVP, 0.4 μg/kg, over 15 minutes followed by an i. v. bolus dose of either standard heparin, 5,000 I.U., or saline. A 48 hour wash-out period was adopted. The infusion of dDAVP followed by standard heparin resulted in a higher increase in plasma t-PA actiyity, t-PA antigen, circulating t-PA specific activity and FPLA when compared with dDAVP followed by saline. The difference was already statistically significant at 15 minutes after the infusion of dDAVP and lasted for up to 60 minutes after the end of the infusion of dDAVP. Plasma PAI 1 showed a slightly higher decrease after dDAVP plus standard heparin than after dDAVP plus saline but this difference was not statistically significant. No statistically significant changes of fibrinogen and α2-antiplasmin levels were observed. As expected, the infusion of standard heparin resulted in an increase in plasma anti-Xa activity and in a prolongation of aPTT Our results demonstrated an additive effect of dDAVP and standard heparin on the increase in circulating t-PA, the effect of dDAVP being potentiated and prolonged by heparin. This observation could prospect a combined use of dDAVP and standard heparin in the prophylaxis and treatment of thromboembolic diseases.