Sepsis and intravascular thrombosis

COVID-19 Infection and Circulating Microparticles-Reviewing Evidence as Microthrombogenic Risk Factor for Cerebral Small Vessel Disease

Severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) due to novel coronavirus disease 2019 (COVID-19) has affected the global society in numerous unprecedented ways, with considerable morbidity and mortality. Both direct and indirect consequences from COVID-19 infection are recognized to give rise to cardio- and cerebrovascular complications. Despite current limited knowledge on COVID-19 pathogenesis, inflammation, endothelial dysfunction, and coagulopathy appear to play critical roles in COVID-19-associated cerebrovascular disease (CVD). One of the major subtypes of CVD is cerebral small vessel disease (CSVD) which represents a spectrum of pathological processes of various etiologies affecting the brain microcirculation that can trigger subsequent neuroinflammation and neurodegeneration. Prevalent with aging, CSVD is a recognized risk factor for stroke, vascular dementia, and Alzheimer's disease. In the background of COVID-19 infection, the heightened cellular activations from inflammations and oxidative stress may result in elevated levels of microthrombogenic extracellular-derived circulating microparticles (MPs). Consequently, MPs could act as pro-coagulant risk factor that may serve as microthrombi for the vulnerable microcirculation in the brain leading to CSVD manifestations. This review aims to appraise the accumulating body of evidence on the plausible impact of COVID-19 infection on the formation of microthrombogenic MPs that could lead to microthrombosis in CSVD manifestations, including occult CSVD which may last well beyond the pandemic era.

Understanding Infection-Induced Thrombosis: Lessons Learned From Animal Models

Thrombosis is a common consequence of infection that is associated with poor patient outcome. Nevertheless, the mechanisms by which infection-associated thrombosis is induced, maintained and resolved are poorly understood, as is the contribution thrombosis makes to host control of infection and pathogen spread. The key difference between infection-associated thrombosis and thrombosis in other circumstances is a stronger inflammation-mediated component caused by the presence of the pathogen and its products. This inflammation triggers the activation of platelets, which may accompany damage to the endothelium, resulting in fibrin deposition and thrombus formation. This process is often referred to as thrombo-inflammation. Strikingly, despite its clinical importance and despite thrombi being induced to many different pathogens, it is still unclear whether the mechanisms underlying this process are conserved and how we can best understand this process. This review summarizes thrombosis in a variety of models, including single antigen models such as LPS, and infection models using viruses and bacteria. We provide a specific focus on Salmonella Typhimurium infection as a useful model to address all stages of thrombosis during infection. We highlight how this model has helped us identify how thrombosis can appear in different organs at different times and thrombi be detected for weeks after infection in one site, yet largely be resolved within 24 h in another. Furthermore, we discuss the observation that thrombi induced to Salmonella Typhimurium are largely devoid of bacteria. Finally, we discuss the value of different therapeutic approaches to target thrombosis, the potential importance of timing in their administration and the necessity to maintain normal hemostasis after treatment. Improvements in our understanding of these processes can be used to better target infection-mediated mechanisms of thrombosis.

Identification of differentially expressed serum proteins in infectious purpura fulminans

Purpura fulminans (PF) is a life-threatening hemorrhagic condition. Because of the rarity and randomness of the disease, no improvement in treatment has been made for a long time. In this study, we assessed the serum proteome response to PF by comparing serum proteins between healthy controls and PF patient. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) approach was used after depleting 6 abundant proteins of serum. In total, 262 proteins were confidently identified with 2 unique peptides, and 38 proteins were identified significantly up- (≥2) or downregulated (≤0.5) based on spectral counting ratios (SpC_PF/N). In the 38 proteins with significant abundance changes, 11 proteins were previously known to be associated with burn or sepsis response, but 27 potentially novel proteins may be specifically associated with PF process. Two differentially expressed proteins, alpha-1-antitrypsin (SERPINA1) and alpha-2 antiplasmin (SERPINF2), were validated by Western blot. This is the first study where PF patient and healthy controls are compared in a proteomic study to elucidate proteins involved in the response to PF. This study provides an initial basis for future studies of PF, and the differentially expressed proteins might provide new therapeutic targets to decrease the mortality of PF.

An open-label study of the role of adjuvant hemostatic support with protein C replacement therapy in purpura fulminans–associated meningococcemia

Activated protein C (APC) is a natural anticoagulant that plays a pivotal role in coagulation homeostasis. Severe inherited or acquired deficiency results in a clinical syndrome called purpura fulminans. In addition, APC also appears to have potent cytokine-modifying properties and is protective in animal models of sepsis. The dual functional properties of APC are particularly relevant to severe meningococcemia, where acquired PC deficiency is accompanied by multiorgan failure and purpura fulminans. The authors conducted an open-label prospective study assessing the efficacy of PC replacement therapy in patients with severe meningococcal septicemia, purpura fulminans, and multiorgan failure. The morbidity and mortality were compared with predicted morbidity using the Glasgow Meningococcal Septicemia Prognostic Score. Thirty-six patients with a mean age of 12 years (range 3 months to 72 years) were enrolled in the study. The mean ± SD for plasma PC was 18 ± 7 IU/mL. PC was significantly lower than antithrombin or protein S and was also significantly lower than PC levels in a cohort of patients who developed meningococcemia without multiorgan failure and purpura fulminans. A total of 3 of 36 (8%) patients died, which compares favorably with predicted mortality of 18 of 36 (50%). Amputations were required in 4 of 33 (12%) survivors and in 2 of 31 (6.5%) patients who received PC within 24 hours of admission into the hospital, in comparison with the predicted amputation rate of 11 of 33 (30%). In conclusion, PC replacement therapy in severe meningococcal septicemia was associated with a reduction in predicted morbidity and mortality. The beneficial effect of PC replacement may reflect both the anticoagulant and anti-inflammatory properties of the PC pathway.

An open-label study of the role of adjuvant hemostatic support with protein C replacement therapy in purpura fulminans–associated meningococcemia

Activated protein C (APC) is a natural anticoagulant that plays a pivotal role in coagulation homeostasis. Severe inherited or acquired deficiency results in a clinical syndrome called purpura fulminans. In addition, APC also appears to have potent cytokine-modifying properties and is protective in animal models of sepsis. The dual functional properties of APC are particularly relevant to severe meningococcemia, where acquired PC deficiency is accompanied by multiorgan failure and purpura fulminans. The authors conducted an open-label prospective study assessing the efficacy of PC replacement therapy in patients with severe meningococcal septicemia, purpura fulminans, and multiorgan failure. The morbidity and mortality were compared with predicted morbidity using the Glasgow Meningococcal Septicemia Prognostic Score. Thirty-six patients with a mean age of 12 years (range 3 months to 72 years) were enrolled in the study. The mean ± SD for plasma PC was 18 ± 7 IU/mL. PC was significantly lower than antithrombin or protein S and was also significantly lower than PC levels in a cohort of patients who developed meningococcemia without multiorgan failure and purpura fulminans. A total of 3 of 36 (8%) patients died, which compares favorably with predicted mortality of 18 of 36 (50%). Amputations were required in 4 of 33 (12%) survivors and in 2 of 31 (6.5%) patients who received PC within 24 hours of admission into the hospital, in comparison with the predicted amputation rate of 11 of 33 (30%). In conclusion, PC replacement therapy in severe meningococcal septicemia was associated with a reduction in predicted morbidity and mortality. The beneficial effect of PC replacement may reflect both the anticoagulant and anti-inflammatory properties of the PC pathway.

A myocardial cytotoxic process is involved in the cardiac dysfunction of meningococcal septic shock

OBJECTIVE

Myocardial dysfunction is a characteristic component of meningococcal septic shock and contributes to the persisting high mortality from the disease. Specific treatment of the myocardial failure has been hampered by the lack of understanding of its pathophysiology. We were interested to determine whether myocardial cell death was occurring in the presence of meningococcal septicemia and whether it correlated with the degree of left ventricular dysfunction and disease severity. We therefore investigated the release of cardiac troponin I (cTnI), a sensitive and specific marker of myocardial cell death, and related this to the severity of disease and cardiac dysfunction.

DESIGN

Prospective study

SETTING

Pediatric intensive care unit

SUBJECTS

Patients admitted to the pediatric intensive care unit with a diagnosis of meningococcal septicemia.

INTERVENTIONS

Serum concentrations of cTnI were determined at admission to intensive care in 101 children with meningococcal septicemia and serially in 37 children. Changes in cTnI were related to disease severity as measured by the Pediatric Risk of Mortality score and two markers of cardiac dysfunction.

MEASUREMENTS AND MAIN RESULTS

Serum concentrations of cTnI were elevated above the range for healthy children in 24% of children with meningococcal septicemia at admission and in 62% of patients within 48 hrs. The peak concentrations occurred between 12 and 36 hrs after admission. There were significant correlations between cTnI levels and disease severity and between cTnI levels and the degree of myocardial depression measured by quantitative transthoracic echocardiography and peak inotrope requirements.

CONCLUSIONS

The elevated serum concentrations of cTnI indicate that myocardial cell death is occurring in meningococcal septicemia. The relationship between cTnI and markers of myocardial function suggest that the cell death may have a role in the pathogenesis of myocardial dysfunction in meningococcal septicemia. Elucidation of the mechanism responsible for myocardial injury may lead to the development of therapeutic interventions to prevent or limit this cardiac damage.

Recognition, treatment and complications of meningococcal disease

Meningococcal disease remains a major cause of death in young children. A decrease in mortality requires recognition and treatment of the disease at a number of stages in the illness. Life-threatening meningococcal disease usually presents as septicaemia rather than meningitis. The cardinal feature of meningococcal septicaemia is the purpuric rash. Many parents recognise the rash and seek medical advice because of it. When primary care physicians recognise the rash, the administration of parenteral penicillin may decrease mortality. However, antibacterials are not given promptly if there is no rash or if the disease presents in an atypical form. In hospital, antibacterial therapy with a third-generation cephalosporin should be given. Disease severity needs to be assessed by a valid method, such as the Glasgow Meningococcal Septicaemia Prognostic Score (GMSPS). This can identify those patients who need intensive care and/or might benefit from new therapies. The 2 life-threatening complications are septic shock and meningoencephalitis with raised intracranial pressure. Despite numerous case reports of success with potential new treatments, none has been proven safe and/or effective by controlled trials. Although it is tempting to focus on new treatments, the early recognition of severe meningococcal disease by parents, primary care physicians and junior hospital doctors is equally, if not more, important as a potential means of decreasing mortality.

Use of protein-C concentrate, heparin, and haemodiafiltration in meningococcus-induced purpura fulminans

BACKGROUND

Inflammatory and coagulation processes are both affected in meningococcaemia. Severe acquired protein-C deficiency in meningococcaemia is usually associated with substantial mortality: in survivors, skin grafts, amputation, and end-organ failure are not uncommon. Protein C is a natural anticoagulant and also has important anti-inflammatory activity. We assessed the effects of early replacement therapy with protein-C concentrate together with continuous veno-venous haemodiafiltration and conventional treatment in meningococcaemia.

METHODS

12 patients aged between 3 months and 27 years with meningococcaemia and severe acquired protein-C deficiency (mean 0.20 IU/mL) were studied. All patients had septic shock, widespread purpura, skin necrosis, and disseminated intravascular coagulopathy. After a test dose of protein-C concentrate, patients received a continuous infusion with the dose adjusted daily to keep the plasma concentration between 0.8 and 1.2 IU/mL. 11 patients were given unfractionated intravenous heparin (10-15 IU kg-1 h-1). Nine patients had haemodiafiltration and one had peritoneal dialysis. The Glasgow meningococcal septicaemia prognostic score and the paediatric risk of mortality score predicted a minimum mortality of 80% and 57%, respectively.

FINDINGS

No patient died. No adverse reactions to the treatment were seen. Two patients had lower-limb amputations, one of whom had a thrombotic cerebrovascular accident; both patients had received the protein-C concentrate and heparin later than the rest of the group (60 h [16.97] vs 12 h [3.13]). One patient developed chronic renal failure despite receiving protein-C infusion 15 h after admission.

INTERPRETATION

The acquired severe deficiency of protein C in meningococcaemia contributes to the pathogenesis of the thrombotic necrotic lesions in the skin and other organs and probably has an important role in the inflammatory response. Protein-C therapy is merely one approach to improve the host response in this syndrome. We suggest that a double-blind, randomised, controlled multicentre trial is needed to confirm our results.

Prediction of neonatal sepsis by thromboelastography

The thromboelastogram (TEG) measures functional defects in coagulation, from fibrin formation through platelet aggregation to fibrinolysis. It is comparable with standard laboratory tests of coagulation; however, it provides additional useful qualitative information. This prospective study documents the TEG findings in 103 neonates: 60 were normal and healthy and provided a reference range; 12 surgical babies had established sepsis, 15 had early sepsis, and 16 were non-septic. TEG abnormalities were detected only in those patients with early and established sepsis. Abnormalities were found in all but 1 of this group of 27 patients (96%), whereas only 16 (59%) had thrombocytopenia, 2 (6%) had leukocytosis, and 6 had leukopenia. The TEG had a sensitivity for sepsis of 96% and a specificity of 96%. This exceeds the values for routine full blood-count parameters and other laboratory indicators of sepsis. It was found to be a simple, quick, and sensitive indicator of early sepsis that enabled the clinicians to manage septic newborns earlier.

Extracorporeal support for intractable cardiorespiratory failure due to meningococcal disease

BACKGROUND

Meningococcal disease is still associated with considerable mortality, despite the use of early antibiotics and management in specialised intensive care units, due principally to early refractory myocardial depression and hypotension as well as severe acute respiratory distress syndrome. Extracorporeal membrane oxygenation (ECMO) is a complex technology that uses a modified "heart-lung" machine to provide temporary cardiac and respiratory support. We reviewed the UK and Australian experience of the use of ECMO in patients with refractory cardiorespiratory failure due to meningococcal disease.

METHODS

The records from all 12 known patients supported with ECMO for meningococcal disease in the UK and Australia since 1989 were reviewed.

FINDINGS

12 patients (aged 4 months to 18 years, median 26 months) with meningococcal disease received ECMO over 8 years. In seven patients, ECMO was required early for cardiac support for intractable shock within 36 h of admission to intensive care. In the other five patients, ECMO was indicated for respiratory failure due to severe adult respiratory distress syndrome, which tended to occur later in the disease. The paediatric risk of mortality score ranged from 13 to 40 (median 29, median predicted risk of mortality 72%). Six of the 12 patients required cardiopulmonary resuscitation before ECMO and the other six were deteriorating despite maximal conventional therapy. Overall, eight of the 12 patients survived, with six leading functionally normal lives at a median of 1 year (range 4 months to 4 years) of follow-up.

INTERPRETATION

ECMO might be considered to support patients with intractable cardiorespiratory failure due to meningococcal disease who are not responding to conventional treatment.

Modulation of the endothelial procoagulant response to lipopolysaccharide and tumour necrosis factor-alpha in-vitro: the effects of dexamethasone, pentoxifylline, iloprost and a polyclonal anti-human IL-1 alpha antibody

Endothelial expression of tissue factor (TF), a potent procoagulant molecule, is increased in response to inflammatory mediators such as lipopolysaccharide (LPS), tumour necrosis factor (TNF) and interleukin-1 (IL-1). We have examined the effects of three antiinflammatory agents and a polyclonal anti-human IL-1 alpha antibody on the human endothelial TF response to E. coli 0111:B4 LPS and recombinant TNF alpha (rTNF alpha) in vitro. In contrast to the expected inhibitory effect, dexamethasone, pentoxyfilline and iloprost failed to block TF expression when administered simultaneously or 30 minutes prior to stimulation with either LPS or rTNF alpha. Inhibition of procoagulant activity was demonstrated with the anti-IL-1 alpha antibody, suggesting that endothelial derived IL-1 alpha is partially responsible for the TF response to the agonists employed. The failure of the antiinflammatory agents to inhibit endothelial TF expression highlights the possibility that therapeutic agents that modulate the circulating monocyte response to LPS and TNF alpha may not ameliorate the endothelial dysfunction that is also induced by these inflammatory mediators.