Neutrophil-mediated Inflammatory Plasminogen Degradation, Rather Than High Plasminogen-Activator Inhibitor-1, May Underly Failures and Inefficiencies of Intrapleural Fibrinolysis.

BACKGROUND: Complex pleural space infections often require treatment with multiple doses of intrapleural tissue plasminogen activator (tPA) and deoxyribonuclease, with treatment failure frequently necessitating surgery. Pleural infections are rich in neutrophils, and neutrophil elastase degrades plasminogen, the target substrate of tPA, that is required to generate fibrinolysis. We hypothesized that pleural fluid from patients with pleural space infection would show high elastase activity, evidence of inflammatory plasminogen degradation, and low fibrinolytic potential in response to tPA that could be rescued with plasminogen supplementation. RESEARCH QUESTION: Does neutrophil elastase degradation of plasminogen contribute to intrapleural fibrinolytic failure? STUDY DESIGN AND METHODS: We obtained infected pleural fluid and circulating plasma from hospitalized adults (n = 10) with institutional review board approval from a randomized trial evaluating intrapleural fibrinolytics vs surgery for initial management of pleural space infection. Samples were collected before the intervention and on days 1, 2, and 3 after the intervention. Activity assays, enzyme-linked immunosorbent assays, and Western blot analysis were performed, and turbidimetric measurements of fibrinolysis were obtained from pleural fluid with and without exogenous plasminogen supplementation. Results are reported as median (interquartile range) or number (percentage) as appropriate, with an α value of .05. RESULTS: Pleural fluid elastase activity was more than fourfold higher (P = .02) and plasminogen antigen levels were more than threefold lower (P = .04) than their corresponding plasma values. Pleural fluid Western blot analysis demonstrated abundant plasminogen degradation fragments consistent with elastase degradation patterns. We found that plasminogen activator inhibitor 1 (PAI-1), the native tPA inhibitor, showed high antigen levels before the intervention, but the overwhelming majority of this PAI-1 (82%) was not active (P = .003), and all PAI-1 activity was lost by day 2 after the intervention in patients receiving intrapleural tPA and deoxyribonuclease. Finally, using turbidity clot lysis assays, we found that the pleural fluid of 9 of 10 patients was unable to generate a significant fibrinolytic response when challenged with tPA and that plasminogen supplementation rescued fibrinolysis in all patients. INTERPRETATION: Our findings suggest that inflammatory plasminogen deficiency, not high PAI-1 activity, is a significant contributor to intrapleural fibrinolytic failure. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT03583931; URL: www. CLINICALTRIALS: gov.

Combination of aspirin and rosuvastatin for reduction of venous thromboembolism in severely injured patients: a double-blind, placebo-controlled, pragmatic randomized phase II clinical trial (The STAT Trial).

INTRODUCTION: Venous thromboembolism (VTE) remains a significant source of postinjury morbidity and mortality. Beta-hydroxy beta-methylglutaryl-CoA (HMG-CoA) reductase inhibitors (rosuvastatin) significantly reduced pathologic clotting events in healthy populations in a prior trial. Furthermore, acetylsalicylic acid (ASA) has been shown to be noninferior to prophylactic heparinoids for VTE prevention following orthopedic surgery. We hypothesized that a combination of rosuvastatin/ASA, in addition to standard VTE chemoprophylaxis, would reduce VTE in critically ill trauma patients. METHODS: This was a double-blind, placebo-controlled, randomized trial, evaluating VTE rates in two groups: ASA + statin (Experimental) and identical placebos (Control). Injured adults, 18-65 years old, admitted to the surgical intensive care unit without contraindications for VTE prophylaxis were eligible. Upon initiation of routine VTE chemoprophylaxis (i.e. heparin/heparin-derivatives), they were randomized to the Experimental or Control group. VTE was the primary outcome. RESULTS: Of 112 potentially eligible patients, 33% (n = 37, median new injury severity scale = 27) were successfully randomized, of whom 11% had VTEs. The Experimental group had no VTEs, while the Control group had 6 VTEs (4 PEs and 2 DVTs) in 4 (22%) patients (P = 0.046). The Experimental treatment was not associated with any serious adverse events. Due to the COVID-19 pandemic, the study was interrupted at the second interim analysis at <10% of the planned enrollment, with significance declared at P < 0.012 at that stage. DISCUSSION: The combination of ASA and rosuvastatin with standard VTE prophylaxis showed a favorable trend toward reducing VTEs with no serious adverse events. An appropriately powered phase III multicenter trial is needed to further investigate this therapeutic approach. LEVEL OF EVIDENCE: Level II, Therapeutic.

Proteomics of Coagulopathy Following Injury Reveals Limitations of Using Laboratory Assessment to Define Trauma-Induced Coagulopathy to Predict Massive Transfusion.

Objective: Trauma-induced coagulopathy (TIC) is provoked by multiple mechanisms and is perceived to be one driver of massive transfusions (MT). Single laboratory values using prothrombin time (INR) or thrombelastography (TEG) are used to clinically define this complex process. We used a proteomics approach to test whether current definitions of TIC (INR, TEG, or clinical judgement) are sufficient to capture the majority of protein changes associated with MT. Methods: Eight level-I trauma centers contributed blood samples from patients available early after injury. TIC was defined as INR >1.5 (INR-TIC), TEG maximum amplitude <50mm (TEG-TIC), or clinical judgement (Clin-TIC) by the trauma surgeon. MT was defined as > 10 units of red blood cells in 24 hours or > 4 units RBC/hour during the first 4 hr. SomaLogic proteomic analysis of 1,305 proteins was performed. Pathways associated with proteins dysregulated in patients with each TIC definition and MT were identified. Results: Patients (n=211) had a mean injury severity score of 24, with a MT and mortality rate of 22% and 12%, respectively. We identified 578 SOMAscan analytes dysregulated among MT patients, of which INR-TIC, TEG-TIC, and Clin-TIC patients showed dysregulation only in 25%, 3%, and 4% of these, respectively. TIC definitions jointly failed to show changes in 73% of the protein levels associated with MT, and failed to identify 26% of patients that received a massive transfusion. INR-TIC and TEG-TIC patients showed dysregulation of proteins significantly associated with complement activity. Proteins dysregulated in Clin-TIC or massive transfusion patients were not significantly associated with any pathway. Conclusion: These data indicate there are unexplored opportunities to identify patients at risk for massive bleeding. Only a small subset of proteins that are dysregulated in patients receiving MT are statistically significantly dysregulated among patients whose TIC is defined based solely on laboratory measurements or clinical assessment.

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.

An Integrated Pharmacological, Structural, and Genetic Analysis of Extracellular Versus Intracellular ROS Production in Neutrophils.

The neutrophil NADPH oxidase produces both intracellular and extracellular reactive oxygen species (ROS). Although oxidase activity is essential for microbial killing, and ROS can act as signaling molecules in the inflammatory process, excessive extracellular ROS directly contributes to inflammatory tissue damage, as well as to cancer progression and immune dysregulation in the tumor microenvironment. How specific signaling pathways contribute to ROS localization is unclear. Here we used a systems pharmacology approach to identify the specific Class I PI3-K isoform p110ß, and PLD1, but not PLD2, as critical regulators of extracellular, but not intracellular ROS production in primary neutrophils. Combined crystallographic and molecular dynamics analysis of the PX domain of the oxidase component p47phox, which binds the lipid products of PI 3-K and PLD, was used to clarify the membrane-binding mechanism and guide the design of mutant mice whose p47phox is unable to bind 3-phosphorylated inositol phospholipids. Neutrophils from these K43A mutant animals were specifically deficient in extracellular, but not intracellular, ROS production, and showed increased dependency on signaling through the remaining PLD1 arm. These findings identify the PX domain of p47phox as a critical integrator of PLD1 and p110ß signaling for extracellular ROS production, and as a potential therapeutic target for modulating tissue damage and extracellular signaling during inflammation.

Plasmin thrombelastography rapidly identifies trauma patients at risk for massive transfusion, mortality, and hyperfibrinolysis: A diagnostic tool to resolve an international debate on tranexamic acid?

BACKGROUND: Trauma patients with hyperfibrinolysis and depletion of fibrinolytic inhibitors (DFIs) measured by thrombelastography (TEG) gain clot strength with TXA, but TEG results take nearly an hour. We aimed to develop an assay, plasmin TEG (P-TEG), to more expeditiously stratify risk for massive transfusion (MT), mortality, and hyperfibrinolysis. METHODS: Trauma patients (N = 148) were assessed using TEG assays without exogenous additives (rapid/native), with exogenous plasmin (P-TEG) or tissue plasminogen activator (tPA TEG). The plasmin dose used does not effect healthy-control clot lysis 30 minutes after maximum amplitude (LY30) but causes shortened reaction time (R time) relative to native TEG (P-TEG R time < native TEG R time considered P-TEG negative). If P-TEG R time is greater than or equal to native TEG R time, the patient was considered P-TEG positive. Each assay's ability to predict MT, mortality, and (risk for) hyperfibrinolysis was determined. χ and Mann-Whitney U tests were used to compare categorical and continuous variables, respectively. Results were reported as median ± interquartile range or n (%). RESULTS: Plasmin TEG provided results faster than all other assays (4.7 ± 2.5-9.1 minutes), approximately 11-fold faster than rapid-TEG (rTEG) LY30 (54.2 ± 51.1-58.1 minutes; p < 0.001). Plasmin TEG-positive patients had greater than fourfold higher MT rate (30% vs. 7%; p = 0.0015) with an area under the receiver operating characteristic curve of 0.686 (p = 0.028), greater than fourfold higher 24-hour mortality (33.3% vs. 7.8%; p = 0.0177), greater than twofold higher 30-day mortality (35% vs. 16.4%; p = 0.0483), higher rates of DFI (55% vs. 18%; p < 0.001), and a trend toward elevated D-dimer (19.9 vs. 3.3 µg/mL; p = 0.14). Plasmin TEG was associated with hyperfibrinolysis on rTEG LY30 at the 7.6% threshold (p = 0.04) but not the 3% threshold (p = 0.40). Plasmin TEG performed best in relation to DFI, with a positive predictive value of 58% and negative predictive value of 81%. When combined with tPA TEG time to maximum amplitude, P-TEG outperformed rTEG LY30 for predicting MT (area under the receiver operating characteristic curve, 0.811 vs. 0.708). CONCLUSION: Within 5 minutes, P-TEG can stratify patients at highest risk for MT, mortality, and risk for hyperfibrinolysis. In composite with tPA TEG time to maximum amplitude, P-TEG outperforms rTEG LY30 for predicting MT and does so four times faster (12.7 vs. 54.1 minutes). The rapid results of P-TEG may be useful for those who practice selective TXA administration to maximize TXA's time-dependent efficacy. LEVEL OF EVIDENCE: Diagnostic test, level V.

Outcomes in Patients With Cardiac Amyloidosis Undergoing Heart Transplantation.

OBJECTIVES: The purpose of this study is to report outcomes after heart transplantation in patients with cardiac amyloidosis based on a large single-center experience. BACKGROUND: Cardiac amyloidosis causes significant morbidity and mortality, often leading to restrictive cardiomyopathy, progressive heart failure, and death. Historically, heart transplantation outcomes have been worse in patients with cardiac amyloidosis compared with other heart failure populations, in part due to the systemic nature of the disease. However, several case series have suggested that transplantation outcomes may be better in the contemporary era, likely in part due to the availability of more effective light chain suppressive therapies for light chain amyloidosis. METHODS: This study examined all patients seen between 2004 and 2017, either at the Stanford University Medical Center or the Kaiser Permanente Santa Clara Medical Center, who were diagnosed with cardiac amyloidosis and ultimately underwent heart transplantation. This study examined pre-transplantation characteristics and post-transplantation outcomes in this group compared with the overall transplantation population at our center. RESULTS: During the study period, 31 patients (13 with light chain amyloidosis and 18 with transthyretin [ATTR] amyloidosis) underwent heart transplantation. Patients with ATTR amyloidosis were older, were more likely to be male, had worse baseline renal function, and had longer waitlist times compared with both patients with light chain amyloidosis and the overall transplantation population. Post-transplantation, there were no differences in post-operative bleeding, renal failure, infection, rejection, or malignancy. There was no significant difference in mortality between patients who underwent heart transplantation for amyloid cardiomyopathy and patients who underwent heart transplantation for all other indications. CONCLUSIONS: In carefully selected patients with cardiac amyloidosis, heart transplantation can be an effective therapeutic option with outcomes similar to those transplanted for other causes of heart failure.

Rescue therapy for severe COVID-19-associated acute respiratory distress syndrome with tissue plasminogen activator: A case series.

The coronavirus disease 2019 (COVID-19) pandemic has led to unprecedented stresses on modern medical systems, overwhelming the resource infrastructure in numerous countries while presenting a unique series of pathophysiologic clinical findings. Thrombotic coagulopathy is common in critically ill patients suffering from COVID-19, with associated high rates of respiratory failure requiring prolonged periods of mechanical ventilation. Here, we report a case series of five patients suffering from profound, medically refractory COVID-19-associated respiratory failure who were treated with fibrinolytic therapy using tissue plasminogen activator (tPA; alteplase). All five patients appeared to have an improved respiratory status following tPA administration: one patient had an initial marked improvement that partially regressed after several hours, one patient had transient improvements that were not sustained, and three patients had sustained clinical improvements following tPA administration. LEVEL OF EVIDENCE: Therapeutic, Level V.

Salvage use of tissue plasminogen activator (tPA) in the setting of acute respiratory distress syndrome (ARDS) due to COVID-19 in the USA: a Markov decision analysis.

BACKGROUND: COVID-19 threatens to quickly overwhelm our existing critical care infrastructure in the USA. Systemic tissue plasminogen activator (tPA) has been previously demonstrated to improve PaO2/FiO2 (mmHg) when given to critically ill patients with acute respiratory distress syndrome (ARDS). It is unclear to what extent tPA may impact population-based survival during the current US COVID-19 pandemic. METHODS: A decision analytic Markov state transition model was created to simulate the life critically ill COVID-19 patients as they transitioned to either recovery or death. Two patient groups were simulated (50,000 patients in each group); (1) Patients received tPA immediately upon diagnosis of ARDS and (2) patients received standard therapy for ARDS. Base case critically ill COVID-19 patients were defined as having a refractory PaO2/FiO2 of < 60 mmHg (salvage use criteria). Transition from severe to moderate to mild ARDS, recovery, and death were estimated. Markov model parameters were extracted from existing ARDS/COVID-19 literature. RESULTS: The use of tPA was associated with reduced mortality (47.6% [tTPA] vs. 71.0% [no tPA]) for base case patients. When extrapolated to the projected COVID-19 eligible for salvage use tPA in the USA, peak mortality (deaths/100,000 patients) was reduced for both optimal social distancing (70.5 [tPA] vs. 75.0 [no tPA]) and no social distancing (158.7 [tPA] vs. 168.8 [no tPA]) scenarios. CONCLUSIONS: Salvage use of tPA may improve recovery of ARDS patients, thereby reducing COVID-19-related mortality and ensuring sufficient resources to manage this pandemic.

Red Blood Cell Fragmentation Syndrome After Placement of MitraClip.

An 87-year-old woman with a history of trastuzumab-induced left ventricular dysfunction underwent the MitraClip (Abbott Vascular, Santa Clara, California) procedure for myxomatous mitral regurgitation. She presented a month later with severe intravascular hemolytic anemia, attributed to the MitraClip. She underwent surgical mitral valve replacement and had resolution of hemolysis. (Level of Difficulty: Advanced.).

A Changing Landscape of Mortality for Systemic Light Chain Amyloidosis.

OBJECTIVES: The purpose of this study was to address the overall trends in mortality since the adoption of modern therapies for treatment of systemic amyloidosis, and to reconsider the prognostic significance of individual components of the current staging system. BACKGROUND: Systemic light chain (AL) amyloidosis involves deposition of immunoglobulin light chains in organs throughout the body and is known to have the highest mortality when significant cardiac involvement is present. Survival has historically been poor but may be improving as systemic therapies continue to advance. This study assesses whether recent advancements in light chain directed therapy have led to improved survival in patients with systemic AL amyloidosis. METHODS: We reviewed all cases of patients who were evaluated for a new diagnosis of AL amyloidosis at the Stanford Amyloid Center between 2009 and 2016. Patients' stage at diagnosis was determined according to the most commonly used staging system. Clinical data, overall survival from diagnosis, and the independent influence of each component of the staging system were analyzed. RESULTS: At total of 194 patients were identified with a new diagnosis of systemic AL amyloidosis. Median overall survival was 59 months and 6 months for stage 3 and 4 patients, respectively. Median overall survival was not reached in stage 1 and 2 groups, as survival was >50% by the end of the study. Mean overall survival was 118 months, 76 months, 64 months, and 27 months in Stages 1, 2, 3, and 4 patients, respectively. Although N-terminal pro-B-type natriuretic peptide and troponin I concentrations had large effects on prognosis, differences in serum free light chains (dFLC) on initial staging laboratory results ≥18 mg/dl, part of the current staging system, did not contribute significantly to prognosis for values ≥5 mg/dl. CONCLUSIONS: Survival for patients with systemic AL amyloidosis has improved for patients at all stages of disease in the present era of rapid advancements in light chain-reducing therapies. Cardiac biomarkers at diagnosis, but not baseline dFLC ≥18 mg/dl, continue to provide important prognostic information.

Clot activators do not expedite the time to predict massive transfusion in trauma patients analyzed with tissue plasminogen activator thrombelastography.

BACKGROUND: Trauma patients with hypersensitivity to tissue plasminogen activator mediated fibrinolysis quantified by tissue plasminogen activator thromboelastography are at increased risk of massive transfusion. The tissue plasminogen activator thromboelastography assay has been tested in trauma patients using native thromboelastography with no exogenous activator. We hypothesize that adding an activator will expedite the time to results. METHODS: Healthy whole blood was assayed with and without exogenous plasmin, which acts to deplete inhibitors of fibrinolysis, mimicking trauma blood. Samples were assessed using native, kaolin, and rapid thromboelastography with and without tissue plasminogen activator. The tissue plasminogen activator thromboelastography indices of time to maximum amplitude and lysis at 30 minutes were contrasted between healthy blood with and without plasmin using the three different activators. The activators were then used with a tissue plasminogen activator thromboelastography in 100 trauma patients to assess performance in predicting massive transfusion. RESULTS: In healthy blood, regardless of activator, lysis at 30 minutes did not increase with plasmin alone, but did increase with tissue plasminogen activator (P = .012). Adding tissue plasminogen activator and plasmin increased lysis at 30 minutes (P = .036). Time to maximum amplitude was reduced with tissue plasminogen activator and plasmin compared with tissue plasminogen activator alone (P = .012). Activated thromboelastographies had increased lysis at 30 minutes (P = .002), but no difference in time to maximum amplitude compared with native thromboelastographies. In trauma patients, native tissue plasminogen activator thromboelastography had greater performance in predicting massive transfusion than activated tissue plasminogen activator thromboelastographies with no difference in time to maximum amplitude. CONCLUSION: Adding an activator to tissue plasminogen activator thromboelastography does not expedite time to maximum amplitude in healthy blood depleted of fibrinolysis inhibitors. Activated tissue plasminogen activator thromboelastographies are inferior to native tissue plasminogen activator thromboelastography for predicting massive transfusion and do not reduce the time to results.

Tranexamic acid mediates proinflammatory and anti-inflammatory signaling via complement C5a regulation in a plasminogen activator-dependent manner.

BACKGROUND: Both tissue plasminogen activator (tPA) in the circulation and urokinase (uPA) in tissues cleave plasminogen (PLG) to plasmin to promote clot lysis. Tranexamic acid (TXA) blocks both the tPA-dependent generation of plasmin on blood clots as well as active plasmin binding to polymerized fibrin, and is commonly administered for bleeding in trauma to limit fibrinolysis. In addition to lysing clots, however, active plasmin also cleaves complement proteins, potentially enhancing inflammation. Because TXA does not block uPA-dependent plasmin generation from PLG and instead augments it, we hypothesized that administration of TXA could enhance or inhibit proinflammatory C5a formation in a PLG activator-dependent manner. METHODS: Citrate platelet-poor plasma (PPP) and PPP depleted of complement protein C3 or PLG were obtained from healthy donors and commercial sources. Platelet-poor plasma was treated ex vivo with or without TXA and either with or without tPA or with or without uPA. Clotting was then induced by calcium and thrombin in clotted PPP experiments, while unclotted PPP experiments were treated with vehicle controls. C5a levels were measured via enzyme-linked immunosorbent assay. Data were expressed as mean ± SEM. RESULTS: Plasmin-mediated fibrinolysis by tPA in clotted PPP led to an approximately threefold increase in C5a production (p < 0.0001), which was significantly inhibited by TXA (p < 0.001). Paradoxically, when fibrinolysis was induced by uPA, TXA treatment led to further increases in C5a production beyond uPA alone (p < 0.0001). Furthermore, clotting was not required for C5a generation from uPA + TXA. C3 depletion had no effect on C5a production, while depletion of PLG eliminated it. CONCLUSIONS: Tranexamic acid administration can have proinflammatory or anti-inflammatory effects through regulating C5a generation by plasmin, depending on the predominating PLG activator. Tranexamic acid may cause significant inflammatory C5a elevations in injured tissues by augmenting uPA-mediated plasmin generation in a fibrin-independent manner. In contrast, TXA reduces C5a generation during tPA-mediated fibrinolysis that may reduce inflammatory responses. In vivo validation of these novel ex vivo findings is warranted and may have important clinical consequences.

Human neutrophil elastase mediates fibrinolysis shutdown through competitive degradation of plasminogen and generation of angiostatin.

BACKGROUND: A subset of trauma patients undergo fibrinolysis shutdown rather than pathologic hyperfibrinolysis, contributing to organ failure. The molecular basis for fibrinolysis shutdown in trauma is incompletely understood. Elastase released from primed/activated human neutrophils (HNE) has historically been described as fibrin(ogen)olytic. However, HNE can also degrade plasminogen (PLG) to angiostatin (ANG), retaining the kringle domains but not the proteolytic function, and could thereby compete for generation of active plasmin by tissue plasminogen activator (tPA). We hypothesized that HNE can drive fibrinolysis shutdown rather than fibrinolysis. METHODS: Turbidometry was performed using light scatter (λ = 620 nm) in a purified fibrinogen + PLG system and in healthy citrate plasma clotted with Ca/thrombin ± tPA, ±HNE, and ±ANG to evaluate HNE effects on fibrinolysis, quantified by time to transition midpoint (Tm). ΔTm from control is reported as percent of control ±95% CI. Purified HNE coincubated with PLG or tPA was analyzed by western blot to identify cleavage products. Exogenous HNE was mixed ex vivo with healthy volunteer blood (n = 7) and used in TEG ± tPA to evaluate effects on fibrinolysis. RESULTS: HNE did not cause measurable fibrinolysis on fibrin clots, clotted plasma, or whole blood as assessed by turbidometry or TEG in the absence of tPA. Upon tPA treatment, all three methods of evaluating fibrinolysis showed delays and decreases in fibrinolysis caused by HNE relative to control: fibrin clot turbidometry ΔTm = 110.7% (CI 105.0-116.5%), clotted citrate plasma (n = 6 healthy volunteers) ΔTm = 126.1% (CI 110.4-141.8%), and whole blood native TEG (n = 7 healthy volunteers) with ΔLY30 = 28% (p = 0.043). Western blot analysis of HNE-PLG co-incubation confirmed that HNE generates angiostatin K1-3, and plasma turbidity assays treated with angiostatin K1-3 delayed fibrinolysis. CONCLUSION: HNE degrades PLG and generates angiostatin K1-3, which predominates over HNE cleavage of fibrin(ogen). These findings suggest that neutrophil release of elastase may underlie trauma-induced fibrinolytic shutdown.

Surgical wound assessment by sonography in the prediction of surgical wound infections.

BACKGROUND: Surgical site infections (SSIs) are important sources of morbidity, prolonged hospital stays, and readmissions, so they have become a major economic burden. We hypothesized that surgical wound assessment by sonography (SWATS) used at the bedside would detect wound fluid collections and that the presence of such collections would predict SSI better than standard clinical examination. If so, SWATS might be used to indicate early intervention that could prevent SSI morbidity. METHODS: A prospective, single-institution observational study was conducted on adult inpatients following open abdominal surgery for trauma, gastrointestinal pathology, or biliary pathology at high risk (>5%) for SSI using traditional wound classifications. After informed consent was obtained, SWATS was performed using a smartphone-based ultrasound system on postoperative Day 2 to 4 and again before discharge or at postoperative Day 30, whichever came first. Primary treating physicians delivered standard wound care and were blinded to SWATS. SSI was diagnosed if treatment was implemented for suspected or documented wound infection by the treating physician. Results were analyzed by χ test and two-sample pooled variance t test where appropriate, with significance set at p < 0.05. RESULTS: Forty-nine patients were studied. Nineteen patients had peri-incisional fluid collections found by SWATS. Eight of these patients went on to develop an SSI. SSI was significantly associated with the presence of fluid collections on SWATS (p = 0.009). SWATS had a sensitivity of 72.7% (0.43-0.92), a specificity of 71.1% (0.62-0.77), a positive predictive value of 42.1% (0.25-0.53), and a negative predictive value of 90.0% (0.79-0.97). CONCLUSION: SWATS has a high negative predictive value that may allow it be an effective screening tool for developing SSI in high-risk surgical wounds. SWATS has the potential to be a useful and cost-effective adjunct to the clinician by objectively suggesting need for early therapy. Further study with larger sample sizes and randomized, SWATS-based interventions are required to validate this small study and determine its place in clinical care. LEVEL OF EVIDENCE: Diagnostic study, level IV.

Kinetics and Role of Plasma Matrix Metalloproteinase-9 Expression in Acute Lung Injury and the Acute Respiratory Distress Syndrome.

Primed neutrophils that are capable of releasing matrix metalloproteinases (MMPs) into the circulation are thought to play a significant role in the pathophysiology of acute respiratory distress syndrome (ARDS). We hypothesized that direct measurement of plasma MMP-9 activity may be a predictor of incipient tissue damage and subsequent lung injury, which was investigated in both an animal model of ARDS and a small cohort of 38 critically ill human patients. In a mouse model of ARDS involving instillation of intratracheal lipopolysaccharide (LPS) to induce lung inflammation, we measured neutrophil-mediated inflammation, along with MMP-9 activity in the airways and lung tissue and MMP-9 expression in the plasma. Neutrophil recruitment, inflammation, and MMP-9 activity in the airways and lung tissue increased throughout the 72 h after LPS instillation, whereas plasma MMP-9 expression was greatest at 12 to 24 h after LPS instillation. The results suggest that the peak in plasma MMP-9 activity may precede the peak of neutrophil inflammation in the airways and lung tissue in the setting of ARDS. Based on this animal study, a retrospective observational cohort study involving 38 patients admitted to a surgical intensive care unit at a tertiary care university hospital with acute respiratory failure requiring intubation and mechanical ventilation was conducted. Plasma samples were collected daily, and MMP-9 activity was compared with lung function as determined by the PaO2/FiO2 ratio. In patients who developed ARDS, a notable increase in plasma MMP-9 activity on a particular day correlated with a decrease in the PaO2/FiO2 ratio on the following day (r = -0.503, P < 0.006). Taken together, these results suggest that plasma MMP-9 activity changes, as a surrogate for primed neutrophils may have predictive value for the development of ARDS in a selected subset of critically ill patients.