Lung Injury Prevention with Aspirin (LIPS-A): a protocol for a multicentre randomised clinical trial in medical patients at high risk of acute lung injury

Role of Platelets in Acute Lung Injury After Extracorporeal Circulation in Cardiac Surgery Patients: A Systemic Review

In vitro circulation (cardiopulmonary bypass, CPB) has been widely used in heart surgery. In the past, it was believed that the reduction of platelet count and impaired platelet function during cardiac surgery were the main causes of acute lung injury (ALI). ALI is a life-threatening clinical syndrome in critically ill patients due to an uncontrolled systemic inflammatory response resulting from direct injury to the lung or indirect injury in the setting of a systemic process. Platelets have an emerging and incompletely understood role in a myriad of ALI after extracorporeal circulation in cardiac surgery patients. An electronic literature search was performed using Pubmed, Scopus and Cinahl investigating ALI, pathogenesis, and role of platelets, treatment and management for ALI patients. Many studies have shown that in vitro circulation is a nonphysiological process that can lead to a decrease in the number of platelets and impaired platelet function, as well as varying degrees of lung damage. The relationship between the effects of in vitro circulation on platelets and acute lung injury is still controversial. This review article discusses the role of platelets in lung injury after cardiopulmonary bypass and resent development in the management of ALI.

Pre-hospital Aspirin Use and Patient Outcomes in COVID-19: Results from the International Viral Infection and Respiratory Illness Universal Study (VIRUS)

Introduction

The goal of this investigation is to assess the association between prehospital use of aspirin (ASA) and patient-centered outcomes in a large global cohort of hospitalized COVID-19 patients.

Methods

This study utilizes data from the Society of Critical Care Medicine Discovery Viral Infection and Respiratory Illness Universal Study (VIRUS) Registry. Adult patients hospitalized from February 15th, 2020, to September 30th, 2021, were included. Multivariable regression analyses were utilized to assess the association between pre-hospital use of ASA and the primary outcome of overall hospital mortality.

Results

21,579 patients were included from 185 hospitals (predominantly US-based, 71.3%), with 4691 (21.7%) receiving pre-hospital ASA. Patients receiving ASA, compared to those without pre-admission ASA use, were generally older (median 70 vs. 59 years), more likely to be male (58.7 vs. 56.0%), caucasian (57.4 vs. 51.6%), and more commonly had higher rates of medical comorbidities. In multivariable analyses, patients receiving pre-hospital ASA had lower mortality (HR: 0.89, 95% CI 0.82–0.97, p = 0.01) and reduced hazard for progression to severe disease or death (HR: 0.91, 95% CI 0.84–0.99, p = 0.02) and more hospital free days (1.00 days, 95% CI 0.66–1.35, p = 0.01) compared to those without pre-hospital ASA use. The overall direction and significance of the results remained the same in sensitivity analysis, after adjusting the multivariable model for time since pandemic.

Conclusions

In this large international cohort, pre-hospital use of ASA was associated with a lower hazard for death in hospitalized patients with COVID-19. Randomized controlled trials may be warranted to assess the utility of pre-hospital use of ASA.

Disease Mechanisms of Perioperative Organ Injury

Despite substantial advances in anesthesia safety within the past decades, perioperative mortality remains a prevalent problem and can be considered among the top causes of death worldwide. Acute organ failure is a major risk factor of morbidity and mortality in surgical patients and develops primarily as a consequence of a dysregulated inflammatory response and insufficient tissue perfusion. Neurological dysfunction, myocardial ischemia, acute kidney injury, respiratory failure, intestinal dysfunction, and hepatic impairment are among the most serious complications impacting patient outcome and recovery. Pre-, intra-, and postoperative arrangements, such as enhanced recovery after surgery programs, can contribute to lowering the occurrence of organ dysfunction, and mortality rates have improved with the advent of specialized intensive care units and advances in procedures relating to extracorporeal organ support. However, no specific pharmacological therapies have proven effective in the prevention or reversal of perioperative organ injury. Therefore, understanding the underlying mechanisms of organ dysfunction is essential to identify novel treatment strategies to improve perioperative care and outcomes for surgical patients. This review focuses on recent knowledge of pathophysiological and molecular pathways leading to perioperative organ injury. Additionally, we highlight potential therapeutic targets relevant to the network of events that occur in clinical settings with organ failure.

Pretreatment with atorvastatin ameliorates cobra venom factor-induced acute lung inflammation in mice

Background

The complement system plays a critical role as the pathogenic factor in the models of acute lung injury due to various causes. Cobra venom factor (CVF) is a commonly used complement research tool. The CVF can cause acute inflammation in the lung by producing complement activation components. Atorvastatin (ATR) is a 3-hydroxy-3-methylglutaryl coenzyme A inhibitor approved for control of plasma cholesterol levels. This inhibitor can reduce the acute pulmonary inflammatory response. However, the ability of ATR in treating acute lung inflammation caused by complement activation is still unknown. Therefore, we investigated the effect of ATR on lung inflammation in mice induced by activation of the complement alternative pathway in this study.

Methods

ATR (10 mg/kg/day via oral gavage) was administered for 7 days before tail vein injection of CVF (25 μg/kg). On the seventh day, all mice were sacrificed 1 h after injection. The lung lobe, bronchoalveolar lavage fluid (BALF), and blood samples were collected. The myeloperoxidase (MPO) activity of the lung homogenate, the leukocyte cell count, and the protein content of BALF were measured. The levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), P-selectin, and Intercellular cell adhesion molecule-1 (ICAM-1) in BALF and serum were determined by enzyme-linked immunosorbent assay. The pathological change of the lung tissue was observed by hematoxylin and eosin staining. The deposition of C5b-9 in the lung tissue was detected by immunohistochemistry. The phosphorylation of NF-κB p65 in the lung tissues was examined by immunohistochemistry and western blotting.

Results

The lung inflammation levels were determined by measuring the leukocyte cell numbers and protein content of BALF, the lung MPO activity, and expression and staining of the inflammatory mediators (IL-6 and TNF-α), and adhesion molecules (P-selectin and ICAM-1) for lung lesion. A significant reduction in the lung inflammation levels was observed after 7 days in ATR pre-treated mice with a CVF-induced lung disease. Deposition of C5b-9 was significantly alleviated by ATR pretreatment. Early intervention with ATR significantly reduced the development of acute lung inflammation on the basis of phosphorylation of NF-κB p65 in the lung.

Conclusion

These findings suggest the identification of ATR treatment for the lung inflammation induced by activating the complement system on the basis of its anti-inflammatory response. Together with the model replicating the complement activating characteristics of acute lung injury, the results may be translatable to the overactivated complement relevant diseases.

The Association between Prehospital Vulnerability, ARDS Development, and Mortality among At-Risk Adults. Results from the LIPS-A Clinical Trial

Rationale: No previous studies have examined the role of prehospital vulnerability in acute respiratory distress syndrome (ARDS) development and mortality in an acutely ill adult population.Objectives: To describe the association between prehospital vulnerability and 1) the development of ARDS, 2) 28-day mortality, and 3) 1-year mortality.Methods: This was a longitudinal prospective cohort study nested within the multicenter LIPS-A (Lung Injury Prevention Study-Aspirin) trial. We analyzed 301 participants who completed Vulnerable Elders Survey (VES) at baseline. Multivariable logistic regression and Cox regression analyses were used to describe the association between vulnerability and short-term outcomes (ARDS and 28-day mortality) and long-term outcomes (1-year mortality), respectively.Results: The VES score ranged from 0 to 10 (median [interquartile range], 2.0 [0-6]); 143 (47.5%) fit criteria for prehospital vulnerability (VES ≥ 3). Vulnerability was not significantly associated with ARDS development (10 [7.0%] vulnerable patients developed ARDS as per LIPS-A study criteria vs. 20 [12.7%] without vulnerability; P = 0.10; adjusted odds ratio [95% confidence interval (CI)], 0.54 [0.24-1.24]; P = 0.15). Nor was vulnerability associated with 28-day mortality (15 [10.5%] vulnerable patients were dead by Day 28 vs. 11 [7.0%] nonvulnerable patients; P = 0.28; adjusted odds ratio [95% CI], 0.95 [0.39-2.26]; P = 0.90). Vulnerability was significantly associated with 1-year mortality in hospital survivors (35 [26.9%] vs. 13 [9.3%]; adjusted hazard ratio [95% CI], 2.20 [1.10-4.37]; P = 0.02).Conclusions: In a population of adults recruited for their high risk of ARDS, prehospital vulnerability, measured by VES, was highly prevalent and strongly associated with 1-year mortality.

Antiplatelet Therapy for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a common and devastating syndrome that contributes to serious morbidities and mortality in critically ill patients. No known pharmacologic therapy is beneficial in the treatment of ARDS, and the only effective management is through a protective lung strategy. Platelets play a crucial role in the pathogenesis of ARDS, and antiplatelet therapy may be a potential medication for ARDS. In this review, we introduce the overall pathogenesis of ARDS, and then focus on platelet-related mechanisms underlying the development of ARDS, including platelet adhesion to the injured vessel wall, platelet-leukocyte-endothelium interactions, platelet-related lipid mediators, and neutrophil extracellular traps. We further summarize antiplatelet therapy, including aspirin, glycoprotein IIb/IIIa receptor antagonists, and P2Y12 inhibitors for ARDS in experimental and clinical studies and a meta-analysis. Novel aspirin-derived agents, aspirin-triggered lipoxin, and aspirin-triggered resolvin D1 are also described here. In this narrative review, we summarize the current knowledge of the role of platelets in the pathogenesis of ARDS, and the potential benefits of antiplatelet therapy for the prevention and treatment of ARDS.

What factors predispose patients to acute respiratory distress syndrome?

Sepsis, pneumonia, and shock are the most common conditions predisposing to acute respiratory distress syndrome (ARDS) and certain host genetic variants have been associated with the development of ARDS. Risk modifiers include abuse of alcohol and tobacco, malnutrition, and obesity. The Lung Injury Prediction Score (LIPS) and the simplified Early Acute Lung Injury Score predict ARDS based on clinical and investigational criteria. Hospital-acquired ARDS may result from a medley factors of which high tidal volume ventilation, high oxygen concentration, and plasma transfusion are most commonly implicated. The Checklist for Lung Injury Prevention (CLIP) has been developed to ensure compliance with evidence-based practice that may affect ARDS occurrence. To date, no pharmacologic intervention has been shown to prevent ARDS

Platelet biology of the rapidly failing lung

Acute respiratory distress syndrome (ARDS) is characterized by a rapid-onset respiratory failure with a mortality rate of approximately 40%. This physiologic inflammatory process is mediated by disruption of the alveolar-vascular interface, leading to pulmonary oedema and impaired oxygen exchange, which often warrants mechanical ventilation to increase survival in the acute setting. One of the least understood aspects of ARDS is the role of the platelets in this process. Platelets, which protect vascular integrity, play a pivotal role in the progression and resolution of ARDS. The recent substantiation of the age-old theory that megakaryocytes are found in the lungs has rejuvenated interest in and raised new questions about the importance of platelets for pulmonary function. In addition to primary haemostasis, platelets provide a myriad of inflammatory functions that are poised to aid the innate immune system. This review focuses on the evidence for regulatory roles of platelets in pulmonary inflammation, with an emphasis on two receptors, CLEC-2 and TLT-1. Studies of these receptors identify novel pathways through which platelets may regulate vascular integrity and inflammation in the lungs, thereby influencing the development of ARDS.

Amicus or Adversary Revisited: Platelets in Acute Lung Injury and Acute Respiratory Distress Syndrome

Platelets are essential cellular effectors of hemostasis and contribute to disease as circulating effectors of pathologic thrombosis. These are their most widely known biologic activities. Nevertheless, recent observations demonstrate that platelets have a much more intricate repertoire beyond these traditional functions and that they are specialized for contributions to vascular barrier integrity, organ repair, antimicrobial host defense, inflammation, and activities across the immune continuum. Paradoxically, on the basis of clinical investigations and animal models of disease, some of these newly discovered activities of platelets appear to contribute to tissue injury. Studies in the last decade indicate unique interactions of platelets and their precursor, the megakaryocyte, in the lung and implicate platelets as essential effectors in experimental acute lung injury and clinical acute respiratory distress syndrome. Additional discoveries derived from evolving work will be required to precisely define the contributions of platelets to complex subphenotypes of acute lung injury and to determine if these remarkable and versatile blood cells are therapeutic targets in acute respiratory distress syndrome.

Early Intravascular Events Are Associated with Development of Acute Respiratory Distress Syndrome. A Substudy of the LIPS-A Clinical Trial

RATIONALE

Acute respiratory distress syndrome (ARDS) is a devastating illness with limited therapeutic options. A better understanding of early biochemical and immunological events in ARDS could inform the development of new preventive and treatment strategies.

OBJECTIVES

To determine select peripheral blood lipid mediator and leukocyte responses in patients at risk for ARDS.

METHODS

Patients at risk for ARDS were randomized as part of a multicenter, double-blind clinical trial of aspirin versus placebo (the LIPS-A [Lung Injury Prevention Study with Aspirin] trial; NCT01504867). Plasma thromboxane B2 (TXB2), aspirin-triggered lipoxin A4 (15-epi-LXA4, ATL), and peripheral blood leukocyte number and activation were determined on enrollment and after treatment with either aspirin or placebo.

MEASUREMENTS AND MAIN RESULTS

Thirty-three of 367 subjects (9.0%) developed ARDS after randomization. Baseline ATL levels, total monocyte counts, intermediate monocyte counts, and monocyte-platelet aggregates were associated with the development of ARDS. Peripheral blood neutrophil count and monocyte-platelet aggregates significantly decreased over time. Of note, nine subjects developed ARDS after randomization yet before study drug initiation, including seven subjects assigned to aspirin treatment. Subjects without ARDS at the time of first dose demonstrated a lower incidence of ARDS with aspirin treatment. Compared with placebo, aspirin significantly decreased TXB2 and increased the ATL/TXB2 ratio.

CONCLUSIONS

Biomarkers of intravascular monocyte activation in at-risk patients were associated with development of ARDS. The potential clinical benefit of early aspirin for prevention of ARDS remains uncertain. Together, results of the biochemical and immunological analyses provide a window into the early pathogenesis of human ARDS and represent potential vascular biomarkers of ARDS risk. Clinical trial registered with www.clinicaltrials.gov (NCT01504867).

Creation of the Prevention of Organ Failure Checklist. A Multidisciplinary Approach Using the Modified Delphi Technique

RATIONALE

Respiratory failure represents a major risk for morbidity and mortality. Although generally managed in the intensive care unit (ICU), respiratory failure often begins elsewhere. Checklists of care processes to minimize the duration of mechanical ventilation and adverse events are routinely used in the ICU, but are uncommonly used outside the ICU.

OBJECTIVES

To develop consensus among a multidisciplinary expert panel on care practices to include in a checklist of best practices for critically ill patients with respiratory failure before and after ICU admission.

METHODS

A multidisciplinary expert panel was assembled. The panel was tasked with creating a checklist of care processes aimed at decreasing progression to respiratory failure, duration of mechanical ventilation, mortality in mechanical ventilation, and adverse events. Over the course of multiple teleconferences and e-mail communications, the Prevention of Organ Failure Checklist list was reviewed, refined, and voted upon. Items that received greater than 75% of the vote were included in the final checklist.

MEASUREMENTS AND MAIN RESULTS

Using a modified Delphi process, the expert panel was able to compile Prevention of Organ Failure Checklist into 20 items that aimed to decrease mechanical ventilation by assessing the causes of acute respiratory failure, ventilation strategies, sedation, and general critical care processes, as well as to avoid unwanted or nonbeneficial interventions.

CONCLUSIONS

The modified Delphi process identified readily available preventative interventions suitable for checklist implementation in patients with or progressing to respiratory failure even before ICU admission.

Favorable Neurocognitive Outcome with Low Tidal Volume Ventilation after Cardiac Arrest

RATIONALE

Neurocognitive outcome after out-of-hospital cardiac arrest (OHCA) is often poor, even when initial resuscitation succeeds. Lower tidal volumes (Vts) attenuate extrapulmonary organ injury in other disease states and are neuroprotective in preclinical models of critical illness.

OBJECTIVE

To evaluate the association between Vt and neurocognitive outcome after OHCA.

METHODS

We performed a propensity-adjusted analysis of a two-center retrospective cohort of patients experiencing OHCA who received mechanical ventilation for at least the first 48 hours of hospitalization. Vt was calculated as the time-weighted average over the first 48 hours, in milliliters per kilogram of predicted body weight (PBW). The primary endpoint was favorable neurocognitive outcome (cerebral performance category of 1 or 2) at discharge.

MEASUREMENTS AND MAIN RESULTS

Of 256 included patients, 38% received time-weighted average Vt greater than 8 ml/kg PBW during the first 48 hours. Lower Vt was independently associated with favorable neurocognitive outcome in propensity-adjusted analysis (odds ratio, 1.61; 95% confidence interval [CI], 1.13-2.28 per 1-ml/kg PBW decrease in Vt; P = 0.008). This finding was robust to several sensitivity analyses. Lower Vt also was associated with more ventilator-free days (β = 1.78; 95% CI, 0.39-3.16 per 1-ml/kg PBW decrease; P = 0.012) and shock-free days (β = 1.31; 95% CI, 0.10-2.51; P = 0.034). Vt was not associated with hypercapnia (P = 1.00). Although the propensity score incorporated several biologically relevant covariates, only height, weight, and admitting hospital were independent predictors of Vt less than or equal to 8 ml/kg PBW.

CONCLUSIONS

Lower Vt after OHCA is independently associated with favorable neurocognitive outcome, more ventilator-free days, and more shock-free days. These findings suggest a role for low-Vt ventilation after cardiac arrest.

Lung Injury Prediction Score in Hospitalized Patients at Risk of Acute Respiratory Distress Syndrome

OBJECTIVE

The Lung Injury Prediction Score identifies patients at risk for acute respiratory distress syndrome in the emergency department, but it has not been validated in non-emergency department hospitalized patients. We aimed to evaluate whether Lung Injury Prediction Score identifies non-emergency department hospitalized patients at risk of developing acute respiratory distress syndrome at the time of critical care contact.

DESIGN

Retrospective study.

SETTING

Five academic medical centers.

PATIENTS

Nine hundred consecutive patients (≥ 18 yr old) with at least one acute respiratory distress syndrome risk factor at the time of critical care contact.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Lung Injury Prediction Score was calculated using the worst values within the 12 hours before initial critical care contact. Patients with acute respiratory distress syndrome at the time of initial contact were excluded. Acute respiratory distress syndrome developed in 124 patients (13.7%) a median of 2 days (interquartile range, 2-3) after critical care contact. Hospital mortality was 22% and was significantly higher in acute respiratory distress syndrome than non-acute respiratory distress syndrome patients (48% vs 18%; p < 0.001). Increasing Lung Injury Prediction Score was significantly associated with development of acute respiratory distress syndrome (odds ratio, 1.31; 95% CI, 1.21-1.42) and the composite outcome of acute respiratory distress syndrome or death (odds ratio, 1.26; 95% CI, 1.18-1.34). A Lung Injury Prediction Score greater than or equal to 4 was associated with the development of acute respiratory distress syndrome (odds ratio, 4.17; 95% CI, 2.26-7.72), composite outcome of acute respiratory distress syndrome or death (odds ratio, 2.43; 95% CI, 1.68-3.49), and acute respiratory distress syndrome after accounting for the competing risk of death (hazard ratio, 3.71; 95% CI, 2.05-6.72). For acute respiratory distress syndrome development, the Lung Injury Prediction Score has an area under the receiver operating characteristic curve of 0.70 and a Lung Injury Prediction Score greater than or equal to 4 has 90% sensitivity (misses only 10% of acute respiratory distress syndrome cases), 31% specificity, 17% positive predictive value, and 95% negative predictive value.

CONCLUSIONS

In a cohort of non-emergency department hospitalized patients, the Lung Injury Prediction Score and Lung Injury Prediction Score greater than or equal to 4 can identify patients at increased risk of acute respiratory distress syndrome and/or death at the time of critical care contact but it does not perform as well as in the original emergency department cohort.

Prevention or Treatment of Ards With Aspirin: A Review of Preclinical Models and Meta-Analysis of Clinical Studies

BACKGROUND

The acute respiratory distress syndrome (ARDS) is a life-threating disorder that contributes significantly to critical illness. No specific pharmacological interventions directed at lung injury itself have proven effective in improving outcome of patients with ARDS. Platelet activation was identified as a key component in ARDS pathophysiology and may provide an opportunity for preventive and therapeutic strategies. We hypothesize that use of acetyl salicylic acid (ASA) may prevent and/or attenuate lung injury.

METHODS

We conducted a systematic review of preclinical studies and meta-analysis of clinical studies investigating the efficacy of ASA in the setting of lung injury. Medline, embase, and cochrane databases were searched.

RESULTS

The literature search yielded 1,314 unique articles. Fifteen preclinical studies and eight clinical studies fulfilled the in- and exclusion criteria. In the animal studies, the overall effect of ASA was positive, e.g., ASA improved survival and attenuated inflammation and pulmonary edema. Mechanisms of actions involved, among others, are interference with the neutrophil-platelets interaction, reduction of leukotrienes, neutrophil extracellular traps, and prostaglandins. High-dose ASA may be the drug of choice. A meta-analysis of three clinical studies showed an association between ASA use and a reduced incidence of ARDS (OR 0.59, 95% CI 0.36-0.98), albeit with substantial between-study heterogeneity. All studies had their own shortcomings in methodological quality.

CONCLUSION

This systematic review of preclinical studies and meta-analysis of clinical studies suggests a beneficial role for ASA in ARDS prevention and treatment. However, the currently available data is insufficient to justify an indication for ASA in ARDS. The body of literature does support further studies in humans. We suggest clinical trials in which the mechanisms of action of ASA in lung injury models are being evaluated to guide optimal timing and dose, before prospective randomized trials.

Platelets in Pulmonary Immune Responses and Inflammatory Lung Diseases

Platelets are essential for physiological hemostasis and are central in pathological thrombosis. These are their traditional and best known activities in health and disease. In addition, however, platelets have specializations that broaden their functional repertoire considerably. These functional capabilities, some of which are recently discovered, include the ability to sense and respond to infectious and immune signals and to act as inflammatory effector cells. Human platelets and platelets from mice and other experimental animals can link the innate and adaptive limbs of the immune system and act across the immune continuum, often also linking immune and hemostatic functions. Traditional and newly recognized facets of the biology of platelets are relevant to defensive, physiological immune responses of the lungs and to inflammatory lung diseases. The emerging view of platelets as blood cells that are much more diverse and versatile than previously thought further predicts that additional features of the biology of platelets and of megakaryocytes, the precursors of platelets, will be discovered and that some of these will also influence pulmonary immune defenses and inflammatory injury.

Effect of Aspirin on Development of ARDS in At-Risk Patients Presenting to the Emergency Department: The LIPS-A Randomized Clinical Trial

IMPORTANCE

Management of acute respiratory distress syndrome (ARDS) remains largely supportive. Whether early intervention can prevent development of ARDS remains unclear.

OBJECTIVE

To evaluate the efficacy and safety of early aspirin administration for the prevention of ARDS.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter, double-blind, placebo-controlled, randomized clinical trial conducted at 16 US academic hospitals. Between January 2, 2012, and November 17, 2014, 7673 patients at risk for ARDS (Lung Injury Prediction Score ≥4) in the emergency department were screened and 400 were randomized. Ten patients were excluded, leaving 390 in the final modified intention-to-treat analysis cohort.

INTERVENTIONS

Administration of aspirin, 325-mg loading dose followed by 81 mg/d (n = 195) or placebo (n = 195) within 24 hours of emergency department presentation and continued to hospital day 7, discharge, or death.

MAIN OUTCOMES AND MEASURES

The primary outcome was the development of ARDS by study day 7. Secondary measures included ventilator-free days, hospital and intensive care unit length of stay, 28-day and 1-year survival, and change in serum biomarkers associated with ARDS. A final α level of .0737 (α = .10 overall) was required for statistical significance of the primary outcome.

RESULTS

Among 390 analyzed patients (median age, 57 years; 187 [48%] women), the median (IQR) hospital length of stay was 6 3-10) days. Administration of aspirin, compared with placebo, did not significantly reduce the incidence of ARDS at 7 days (10.3% vs 8.7%, respectively; odds ratio, 1.24 [92.6% CI, 0.67 to 2.31], P = .53). No significant differences were seen in secondary outcomes: ventilator-free to day 28, mean (SD), 24.9 (7.4) days vs 25.2 (7.0) days (mean [90% CI] difference, -0.26 [-1.46 to 0.94] days; P = .72); ICU length of stay, mean (SD), 5.2 (7.0) days vs 5.4 (7.0) days (mean [90% CI] difference, -0.16 [-1.75 to 1.43] days; P = .87); hospital length of stay, mean (SD), 8.8 (10.3) days vs 9.0 (9.9) days (mean [90% CI] difference, -0.27 [-1.96 to 1.42] days; P = .79); or 28-day survival, 90% vs 90% (hazard ratio [90% CI], 1.03 [0.60 to 1.79]; P = .92) or 1-year survival, 73% vs 75% (hazard ratio [90% CI], 1.06 [0.75 to 1.50]; P = .79). Bleeding-related adverse events were infrequent in both groups (aspirin vs placebo, 5.6% vs 2.6%; odds ratio [90% CI], 2.27 [0.92 to 5.61]; P = .13).

RESULTS

Among 390 analyzed patients (median age, 57 years; 187 [48%] women), median (IQR) hospital length of stay was 6 (3-10) days. Administration of aspirin, compared with placebo, did not significantly reduce the incidence of ARDS at 7 days (OR, 1.24; 92.6%CI, 0.67-2.31). No significant differences were seen in secondary outcomes or adverse events. [table: see text]

CONCLUSIONS AND RELEVANCE

Among at-risk patients presenting to the ED, the use of aspirin compared with placebo did not reduce the risk of ARDS at 7 days. The findings of this phase 2b trial do not support continuation to a larger phase 3 trial.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01504867.

Effect of Antiplatelet Therapy on Acute Respiratory Distress Syndrome and Mortality in Critically Ill Patients: A Meta-Analysis

BACKGROUND

Antiplatelet agents are commonly used for cardiovascular diseases, but their pleiotropic effects in critically ill patients are controversial. We therefore performed a meta-analysis of cohort studies to investigate the effect of antiplatelet therapy in the critically ill.

METHODS

Nine cohort studies, retrieved from PubMed and Embase before November 2015, involving 14,612 critically ill patients and 4765 cases of antiplatelet users, were meta-analysed. The main outcome was hospital or 30-day mortality. Secondary outcome was acute respiratory distress syndrome (ARDS) or acute lung injury (ALI). Random- or fixed-effect models were taken for quantitative synthesis of the data.

RESULTS

Antiplatelet therapy was associated with decreased mortality (odds ratio (OR) 0.61; 95% confidence interval (CI), 0.52-0.71; I2 = 0%; P <0. 001) and ARDS/ALI (OR 0.64; 95% CI, 0.50-0.82; I2 = 0%; P <0. 001). In every stratum of subgroups, similar findings on mortality reduction were consistently observed in critically ill patients.

CONCLUSIONS

Antiplatelet therapy is associated with reduced mortality and lower incidence of ARDS/ALI in critically ill patients, particularly those with predisposing conditions such as high-risk surgery, trauma, pneumonia, and sepsis. However, it remains unclear whether similar findings can be observed in the unselected and broad population with critical illness.

Trauma indices for prediction of acute respiratory distress syndrome

BACKGROUND

A myriad of trauma indices has been validated to predict probability of trauma survival. We aimed to compare the performance of commonly used indices for the development of the acute respiratory distress syndrome (ARDS).

MATERIALS AND METHODS

Historic, observational cohort study of 27,385 consecutive patients admitted to a statewide referral trauma center between July 11, 2003 and October 31, 2011. A validated algorithm was adapted to identify patients with ARDS. Each trauma index was evaluated in logistic regression using the area under the receiver operating characteristic curve.

RESULTS

The case rate for ARDS development was 5.8% (1594). The receiver operating characteristics for injury severity score (ISS) had the best discrimination and had an area under the curve of 0.88 (95% confidence interval [CI] = 0.87-0.89). Glasgow coma score (0.71, 95% CI = 0.70-0.73), A Severity Characterization of Trauma (0.86, 95% CI = 0.85-0.87), Revised Trauma Score (0.71, 95% CI = 0.70-0.72) and thorax Abbreviated Injury Score (0.73, 95% CI = 0.72-0.74) performed worse (P < 0.001) and Trauma and Injury Severity Score (0.88, 95% CI = 0.87-0.88) performed equivocally (P = 0.51) in comparison to ISS. Using a cutoff point ISS ≥16, sensitivity and specificity were 84.9% (95% CI = 83.0%-86.6%) and 75.6% (95% CI = 75.1%-76.2%), respectively.

CONCLUSIONS

Among commonly used trauma indices, ISS has superior or equivocal discriminative ability for development of ARDS. A cutoff point of ISS ≥16 provided good sensitivity and specificity. The use of ISS ≥16 is a simple method to evaluate ARDS in trauma epidemiology and outcomes research.

Platelets in the pathogenesis of acute respiratory distress syndrome

Platelets have an emerging and incompletely understood role in a myriad of host immune responses, extending their role well beyond regulating thrombosis. Acute respiratory distress syndrome is a complex disease process characterized by a range of pathophysiologic processes including oxidative stress, lung deformation, inflammation, and intravascular coagulation. The objective of this review is to summarize existing knowledge on platelets and their putative role in the development and resolution of lung injury.

Aspirin as a potential treatment in sepsis or acute respiratory distress syndrome

Sepsis is a common condition that is associated with significant morbidity, mortality and health-care cost. Pulmonary and non-pulmonary sepsis are common causes of the acute respiratory distress syndrome (ARDS). The mortality from ARDS remains high despite protective lung ventilation, and currently there are no specific pharmacotherapies to treat sepsis or ARDS. Sepsis and ARDS are characterised by activation of the inflammatory cascade. Although there is much focus on the study of the dysregulated inflammation and its suppression, the associated activation of the haemostatic system has been largely ignored until recently. There has been extensive interest in the role that platelet activation can have in the inflammatory response through induction, aggregation and activation of leucocytes and other platelets. Aspirin can modulate multiple pathogenic mechanisms implicated in the development of multiple organ dysfunction in sepsis and ARDS. This review will discuss the role of the platelet, the mechanisms of action of aspirin in sepsis and ARDS, and aspirin as a potential therapy in treating sepsis and ARDS.

Preoperative Aspirin Use and Lung Injury After Aortic Valve Replacement Surgery: A Retrospective Cohort Study

BACKGROUND

Acute respiratory distress syndrome (ARDS) occurs uncommonly after cardiac surgery but has a mortality rate as high as 80%. Aspirin may prevent lung injury in at-risk patients by reducing platelet-neutrophil aggregates in the lung. We hypothesized that preoperative aspirin use would be associated with a decreased risk of ARDS after aortic valve replacement surgery.

METHODS

We performed a retrospective single-center cohort study that included all adult patients who had aortic valve replacement surgery during a 5-year period. The primary outcome variable was postoperative ARDS. The secondary outcome variable was nadir PaO2/FIO2 ratio during the first 72 hours after surgery. Both crude and propensity score-adjusted logistic regression analyses were performed to estimate the odds ratio for developing ARDS in aspirin users. Subgroups were analyzed to determine whether preoperative aspirin use might be associated with improved oxygenation in patients with specific risk factors for lung injury.

RESULTS

Of the 375 patients who had aortic valve replacement surgery during the study period, 181 patients took aspirin preoperatively (48.3%) with most taking a dose of 81 mg (72.0%). There were 22 cases of ARDS in the cohort (5.5%). There was no significant difference in the rate of ARDS between aspirin users and nonusers (5.0% vs 6.7%, P = 0.52). There was also no significant difference in the nadir PaO2/FIO2 ratio between aspirin users and nonusers (P = 0.12). The crude odds ratio for ARDS in aspirin users was 0.725 (99% confidence interval, 0.229-2.289; P = 0.47), and the propensity score-adjusted odds ratio was 0.457 (99% confidence interval, 0.120-1.730; P = 0.13).

CONCLUSIONS

Within the constraints of this analysis that included only 22 affected patients, preoperative aspirin use was not associated with a decreased incidence of ARDS after aortic valve replacement surgery or improved oxygenation.

Prevention of acute respiratory distress syndrome

PURPOSE OF REVIEW

The paucity of effective therapeutic interventions in patients with the acute respiratory distress syndrome (ARDS) combined with overwhelming evidence on the importance of timely implementation of effective therapies to critically ill patients has resulted in a recent shift in ARDS research. Increasingly, efforts are being directed toward early identification of patients at risk with a goal of prevention and early treatment, prior to development of the fully established syndrome. The focus of the present review is on the prevention of ARDS in patients without this condition at the time of their healthcare encounter.

RECENT FINDINGS

The primary thematic categories presented in the present review article include early identification of patients at risk of developing ARDS, optimization of care delivery and its impact on the incidence of ARDS, pharmacological prevention of ARDS, prevention of postoperative ARDS, and challenges and opportunities with ARDS prevention studies.

SUMMARY

Recent improvements in clinical care delivery have been associated with a decrease in the incidence of hospital-acquired ARDS. Despite the initial challenges, research in ARDS prevention has become increasingly feasible with several randomized controlled trials on ARDS prevention completed or on the way.

Emerging therapies for the prevention of acute respiratory distress syndrome

The development of acute respiratory distress syndrome (ARDS) carries significant risk of morbidity and mortality. To date, pharmacological therapy has been largely ineffective for patients with ARDS. We present our personal review aimed at outlining current and future directions for the pharmacological prevention of ARDS. Several available risk-stratification or prediction score strategies for identification of patients at risk of ARDS have been reported. Although not ready for clinical everyday use, they are and will be instrumental in the ongoing and future trials of pharmacoprevention of ARDS.Several systemic medications established the potential role in ARDS prevention based on the preclinical studies and observational data. Due to potential for systemic adverse effects to neutralize any pharmacological benefits of systemic therapy, inhaled medications appear particularly attractive candidates for ARDS prevention. This is because of their direct delivery to the site of proposed action (lungs), while the pulmonary epithelial surface is still functional.We postulate that overall morbidity and mortality rates from ARDS in the future will be contingent upon decreasing the overall incidence of ARDS through effective identification of those at risk and early application of proven supportive care and pharmacological interventions.

Prehospital aspirin use is associated with reduced risk of acute respiratory distress syndrome in critically ill patients: a propensity-adjusted analysis

OBJECTIVES

Platelet activation plays an active role in the pathogenesis of acute respiratory distress syndrome. In our prior study of 575 patients at high risk for acute respiratory distress syndrome, concurrent statin and aspirin use was associated with reduced acute respiratory distress syndrome. However, the largest study (n = 3,855) to date found no significant benefit of prehospital aspirin in a lower-risk population when adjusted for the propensity for aspirin use. We aimed to determine whether prehospital aspirin use is associated with decreased acute respiratory distress syndrome in patients at high risk for acute respiratory distress syndrome after adjusting for the propensity to receive aspirin.

DESIGN

Secondary analysis of patients enrolled prospectively in the Validating Acute Lung Injury Markers for Diagnosis study.

PATIENTS

A total of 1,149 critically ill patients (≥40 years old) admitted to the medical or surgical ICUs of an academic tertiary care hospital including 575 previously reported patients as well as additional patients who were enrolled after completion of the prior statin and aspirin study.

INTERVENTION

None.

MEASUREMENTS AND RESULTS

Of 1,149 patients, 368 (32%) developed acute respiratory distress syndrome during the first 4 ICU days and 287 (25%) patients had prehospital aspirin use. Patients with prehospital aspirin had significantly lower prevalence of acute respiratory distress syndrome (27% vs 34%; p=0.034). In a multivariable, propensity-adjusted analysis including age, gender, race, sepsis, and Acute Physiology and Chronic Health Evaluation score II, prehospital aspirin use was associated with a decreased risk of acute respiratory distress syndrome (odds ratio, 0.66; 95% CI, 0.46-0.94) in the entire cohort and in a subgroup of 725 patients with sepsis (odds ratio, 0.60; 95% CI, 0.41-0.90).

CONCLUSIONS

In this selected cohort of critically ill patients, prehospital aspirin use was independently associated with a decreased risk of acute respiratory distress syndrome even after adjusting for the propensity of prehospital aspirin use. These findings support the need for prospective clinical trials to determine whether aspirin may be beneficial for the prevention of clinical acute respiratory distress syndrome.

Who cares about preventing acute respiratory distress syndrome?

Acute respiratory distress syndrome (ARDS) is a common, lethal, and morbid respiratory complication primarily seen in the setting of major trauma and infection. Despite advances in mechanical ventilation for ARDS, many interventions have not been successful in reducing mortality. Recent grant announcements and ongoing clinical trials indicate an interest in preventing ARDS. This Perspective challenges some of the basic assumptions of ARDS prevention and preventive care in the intensive care unit. ARDS is an organ function surrogate outcome. Studies of surrogate outcomes in medicine have repeatedly failed to show an association with patient-centered outcomes that might include mortality, quality of life, patient satisfaction, and cost. Organ failure surrogate outcomes in critical care, including oxygenation, cardiac output, and blood pressure, have similarly failed to show a consistent association with patient-centered benefit. Trials designed to demonstrate an effect on surrogate outcomes will rarely be able to demonstrate small, but important, harms so that the net benefit of prevention can be calculated. This will leave clinicians with insufficient information to balance the unknown benefits of ARDS prevention with imprecisely estimated costs or risks of prevention. Because ARDS diagnosis relies on oxygenation and the chest radiograph that might be directly influenced by the prophylactic intervention, studies must be designed to insure that the prevention is not merely cosmetic. Strategies that prevent ARDS need to be tested in trials sufficiently powered to demonstrate their patient-centered costs, benefits and harms before widespread adoption.

Aspirin therapy in patients with acute respiratory distress syndrome (ARDS) is associated with reduced intensive care unit mortality: a prospective analysis

Introduction

Acute respiratory distress syndrome (ARDS) is a common clinical syndrome with high mortality and long-term morbidity. To date there is no effective pharmacological therapy. Aspirin therapy has recently been shown to reduce the risk of developing ARDS, but the effect of aspirin on established ARDS is unknown.

Methods

In a single large regional medical and surgical ICU between December 2010 and July 2012, all patients with ARDS were prospectively identified and demographic, clinical, and laboratory variables were recorded retrospectively. Aspirin usage, both pre-hospital and during intensive care unit (ICU) stay, was included. The primary outcome was ICU mortality. We used univariate and multivariate logistic regression analyses to assess the impact of these variables on ICU mortality.

Results

In total, 202 patients with ARDS were included; 56 (28%) of these received aspirin either pre-hospital, in the ICU, or both. Using multivariate logistic regression analysis, aspirin therapy, given either before or during hospital stay, was associated with a reduction in ICU mortality (odds ratio (OR) 0.38 (0.15 to 0.96) P = 0.04). Additional factors that predicted ICU mortality for patients with ARDS were vasopressor use (OR 2.09 (1.05 to 4.18) P = 0.04) and APACHE II score (OR 1.07 (1.02 to 1.13) P = 0.01). There was no effect upon ICU length of stay or hospital mortality.

Conclusion

Aspirin therapy was associated with a reduced risk of ICU mortality. These data are the first to demonstrate a potential protective role for aspirin in patients with ARDS. Clinical trials to evaluate the role of aspirin as a pharmacological intervention for ARDS are needed.

Preventing ARDS: progress, promise, and pitfalls

Advances in critical care practice have led to a substantial decline in the incidence of ARDS over the past several years. Low tidal volume ventilation, timely resuscitation and antimicrobial administration, restrictive transfusion practices, and primary prevention of aspiration and nosocomial pneumonia have likely contributed to this reduction. Despite decades of research, there is no proven pharmacologic treatment of ARDS, and mortality from ARDS remains high. Consequently, recent initiatives have broadened the scope of lung injury research to include targeted prevention of ARDS. Prediction scores have been developed to identify patients at risk for ARDS, and clinical trials testing aspirin and inhaled budesonide/formoterol for ARDS prevention are ongoing. Future trials aimed at preventing ARDS face several key challenges. ARDS has not been validated as an end point for pivotal clinical trials, and caution is needed when testing toxic therapies that may prevent ARDS yet potentially increase mortality.

Approach to the patient with the acute respiratory distress syndrome

Given the high incidence and mortality of acute respiratory distress syndrome (ARDS) in critically ill patients, every practitioner needs a bedside approach both for early identification of patients at risk for ARDS and for the appropriate evaluation of patients who meet the diagnostic criteria of ARDS. Recent advances such as the Lung Injury Prediction score, the Early Acute Lung Injury score, and validation of the SpO(2)/Fio(2) ratio for assessing the degree of hypoxemia are all practical tools to aid the practitioner in caring for patients at risk of ARDS.

Is there a need for emerging drugs for the acute respiratory distress syndrome?

The acute respiratory distress syndrome (ARDS) is a common and devastating syndrome of acute respiratory failure for which little effective pharmacotherapy exists. The authors describe some interventions that show promise as potential therapies for this condition, with particular reference to clinically relevant human models of ARDS. Aspirin, mesenchymal stromal (stem) cells, keratinocyte growth factor, IFN-β and oncostatin M inhibition are discussed.

Predicting risk of postoperative lung injury in high-risk surgical patients: a multicenter cohort study

BACKGROUND

Acute respiratory distress syndrome (ARDS) remains a serious postoperative complication. Although ARDS prevention is a priority, the inability to identify patients at risk for ARDS remains a barrier to progress. The authors tested and refined the previously reported surgical lung injury prediction (SLIP) model in a multicenter cohort of at-risk surgical patients.

METHODS

This is a secondary analysis of a multicenter, prospective cohort investigation evaluating high-risk patients undergoing surgery. Preoperative ARDS risk factors and risk modifiers were evaluated for inclusion in a parsimonious risk-prediction model. Multiple imputation and domain analysis were used to facilitate development of a refined model, designated SLIP-2. Area under the receiver operating characteristic curve and the Hosmer-Lemeshow goodness-of-fit test were used to assess model performance.

RESULTS

Among 1,562 at-risk patients, ARDS developed in 117 (7.5%). Nine independent predictors of ARDS were identified: sepsis, high-risk aortic vascular surgery, high-risk cardiac surgery, emergency surgery, cirrhosis, admission location other than home, increased respiratory rate (20 to 29 and ≥30 breaths/min), FIO2 greater than 35%, and SpO2 less than 95%. The original SLIP score performed poorly in this heterogeneous cohort with baseline risk factors for ARDS (area under the receiver operating characteristic curve [95% CI], 0.56 [0.50 to 0.62]). In contrast, SLIP-2 score performed well (area under the receiver operating characteristic curve [95% CI], 0.84 [0.81 to 0.88]). Internal validation indicated similar discrimination, with an area under the receiver operating characteristic curve of 0.84.

CONCLUSIONS

In this multicenter cohort of patients at risk for ARDS, the SLIP-2 score outperformed the original SLIP score. If validated in an independent sample, this tool may help identify surgical patients at high risk for ARDS.

Reducing the burden of acute respiratory distress syndrome: the case for early intervention and the potential role of the emergency department

The mortality for acute respiratory distress syndrome (ARDS) remains unacceptably high. Success in clinical trials has been limited, resulting in a lack of effective therapies to treat the syndrome. The projected increase in mechanically ventilated patients and global need for critical care services suggests that the clinical and research landscape in ARDS can no longer be confined to the intensive care unit. A demonstrable minority of patients present to the emergency department (ED) with ARDS, and ARDS onset typically occurs shortly after intensive care unit admission. Furthermore, the ED is an entry point for many of the highest-risk patients for ARDS development and progression. These facts, combined with prolonged lengths of stay in the ED, suggest that the ED could represent a window of opportunity for treatment and preventive strategies, as well as clinical trial enrollment. This review aims to discuss some of the potential strategies that may prevent or alter the trajectory of ARDS, with a focus on the potential role the ED could play in reducing the burden of this syndrome.

Alterations in platelet function during aging: clinical correlations with thromboinflammatory disease in older adults

Platelets have a dynamic functional repertoire that mediates hemostatic and inflammatory responses. Many of these functions are altered in older adults, promoting a prothrombotic, proinflammatory milieu and contributing to risk of adverse clinical events. Drawing primarily from human studies, this review summarizes important aspects of aging-related changes in platelets. The relationship between altered platelet functions and thrombotic and inflammatory disorders in older adults is highlighted. Established and developing antiplatelet therapies for the treatment of thrombotic and inflammatory disorders are also discussed in light of these data.

SpO2/FiO2 ratio on hospital admission is an indicator of early acute respiratory distress syndrome development among patients at risk

PURPOSE

Oxygen saturation to fraction of inspired oxygen ratio (SpO(2)/FiO(2)) has been validated as a surrogate marker for partial pressure of oxygen to fraction of inspired oxygen ratio among mechanically ventilated patients with acute respiratory distress syndrome (ARDS). The validity of SpO(2)/FiO(2) measurements in predicting ARDS has not been studied. Recently, a Lung Injury Prediction Score (LIPS) has been developed to help identify patients at risk of developing ARDS.

METHODS

This was a secondary analysis of the LIPS-1 cohort. A multivariate logistic regression included all established variables for LIPS, Acute Physiology and Chronic Health Evaluation 2, age, and comorbid conditions that could affect SpO(2)/FiO(2). The primary outcome was development of ARDS in the hospital. The secondary outcomes included hospital mortality, hospital day of ARDS development, and hospital day of death.

RESULTS

Of the 5584 patients, we evaluated all 4646 with recorded SpO(2)/FiO(2) values. Median SpO(2)/FiO(2) in those who did and did not develop ARDS was 254 (100, 438) and 452 (329, 467), respectively. There was a significant association between SpO(2)/FiO(2) and ARDS (P ≤ .001). The SpO(2)/FiO(2) was found to be an independent predictor of ARDS in a "dose-dependent" manner; for SpO(2)/FiO(2) < 100--odds ratios (OR) 2.49 (1.69-3.64, P < .001), for SpO(2)/FiO(2) 100 < 200--OR 1.75 (1.16-2.58, P = .007), and for SpO(2)/FiO(2) 200 < 300--OR 1.62 (1.06-2.42, P = .025). The discriminatory characteristics of the multivariable model and SpO2/FiO2 as a single variable demonstrated area under the curve (AUC) of 0.81 and AUC of 0.74, respectively.

CONCLUSIONS

The SpO2/FiO2, measured within the first 6 hours after hospital admission, is an independent indicator of ARDS development among patients at risk.

Inflammation and thrombosis in cardiovascular disease

PURPOSE OF REVIEW

This article will summarize recent observations that provide mechanistic insight into the molecular and cellular links between inflammation and thrombosis in the context of cardiovascular and other thromboinflammatory disease states.

RECENT FINDINGS

Several disease conditions are characterized by a thromboinflammatory state in which interactions of blood cells and components with the vascular wall perpetuate both thrombotic and inflammatory pathways. Targeting these pathways may be of benefit in inflammatory conditions and cardiovascular disease.

SUMMARY

Ongoing clinical trials should provide additional insight into the hypothesis that the thromboinflammatory state contributes to adverse clinical outcomes.