Nebulized heparin reduces levels of pulmonary coagulation activation in acute lung injury

The Efficacy of Daily Administration of Nebulized Heparin on the Prevention of Endotracheal Tube Blockage in Patients With Pneumonia

OBJECTIVE

Nosocomial infections pose a significant public health concern, impacting over 100 million people worldwide annually. Within this research, we investigated heparin nebulization through the endotracheal tube and its effect on preventing blockage due to clots and mucus plugs compared to normal saline.

METHODS

A double-blind clinical experiment was done on a cohort of 40 pneumonia patients who were intubated and hospitalized in the intensive care unit (ICU) at Imam Khomeini Hospital in Ahvaz, Iran. The individuals were randomly assigned to two groups of 20 patients using a random allocation technique. The initial cohort was administered 5000 IU of heparin diluted in 4 ccs of 0.9% normal saline every eight hours via a nebulizer through a tracheal tube. In contrast, the second cohort was given 5 ccs of normal saline as a nebulizer through a tracheal tube. The study compared the incidence of tracheal tube obstruction caused by mucus plug or clot, the occurrence of patient hypoxia resulting in emergency tracheal tube replacement, and the frequency of emergency tracheal tube suction due to partial obstruction caused by mucus plug in both the heparin and saline groups.

RESULTS

According to our data, the number of patients in the heparin group who could avoid the need for emergency tracheal tube replacement owing to blockage was more significant than in the ordinary saline group (P=0.013). Heparin was significantly correlated with the number of times emergency suction was required to remove a tracheal tube occlusion (P=0.01). Heparin had no significant effect on coagulation factors (international normalized ratio [INR], platelet [PLT], and partial thromboplastin time [PTT]), Acute Physiology and Chronic Health Evaluation (APACHE) score, pneumonia severity index (PSI), saturation of patients, or tracheal tube secretions. There was no statistically significant difference in total time spent in the intensive care unit (P=0.91).

CONCLUSIONS

Further studies are suggested to determine the effect of heparin nebulization on preventing endotracheal tube obstruction due to clots and mucus plugs in intubated ICU patients.

The effect of nebulized heparin on clinical outcomes in mechanically ventilated patients: a meta-analysis and review of the literature

OBJECTIVE

To determine the relationship between use of nebulized heparin and clinical outcomes in mechanically ventilated patients.

METHODS

The Medline, Embase, Web of Science, Cochrane Library, and PubMed databases were searched for relevant randomized controlled trials (RCTs), published between database inception and May 2022. Primary outcomes were intensive care unit (ICU) length of stay and in-hospital mortality; secondary outcomes included duration of mechanical ventilation, ventilator-free days (VFDs) in 28 days, and length of hospitalization. The study protocol was registered on PROSPERO (registration No: CRD42022345533).

RESULTS

A total of eight RCTs (651 patients) were included. Nebulized heparin was associated with reduced ICU length of stay (six studies; mean difference [MD] -1.10, 95% confidence interval [CI] -1.87, -0.33, I2 = 76%), reduced duration of mechanical ventilation (two studies; MD -2.63, 95% CI -3.68, -1.58, I2 = 92%) and increased VFDs in 28 days (two studies; MD 4.22, 95% CI 1.10, 7.35, I2 = 18%), without increased incidence of adverse events, such as bleeding; but was not associated with a reduction in length of hospitalization (three studies; MD -1.00, 95% CI -2.90, -0.90, I2 = 0%) or in-hospital mortality (five studies; odds ratio 1.10, 95% CI 0.69, 1.77, I2 = 0%).

CONCLUSION

Nebulized heparin reduces ICU length of stay and duration of mechanical ventilation in mechanically ventilated patients, but has no effect on length of hospitalization or mortality.

Role of Nebulized Heparin in Clinical Outcome of COVID-19 Patients with Respiratory Symptoms: A Systematic Review

Coronavirus disease-2019 (COVID-19) is an extremely contagious illness caused by the SARS-CoV-2 virus and has been declared a pandemic by the World Health Organization (WHO). There are currently no particular treatments, however, nebulized heparin has been offered as a viable therapy. The purpose of this systematic review is to assess the efficacy of nebulized heparin in COVID-19 patients with respiratory symptoms.

Methods

Relevant studies were identified through a systematic search of the PubMed, Medline, Embase, Cochrane Library and Web of Science, and Scopus databases. The search terms included "nebulized heparin," "COVID-19," and "SARS-CoV-2." Studies that evaluated the use of nebulized heparin in COVID-19 patients with respiratory symptoms were included. The rest of the studies along with those that were not published in English were excluded. The systematic review was registered under PROSPERO-CRD42023413927.

Observations

Five studies have been included in this systematic review. Case reports, case series, observational studies, and randomized controlled trial (RCT) comprised the studies. The patient sample sizes ranged from 2 to 98. The studies assessed the efficacy of nebulized heparin in COVID-19 patients with variable disease severity. The evaluated outcomes included mortality, hospital stay duration, oxygen requirements, and laboratory parameters.

Conclusion

Based on the clinical studies included in this systematic review, nebulized heparin may be useful in the management of COVID-19. Oxygen saturation was greater, inflammatory indicators were lower, and hospital stays were shorter in these patients. However, the studies had limitations, including inconsistent sample sizes, varying dosages of nebulized heparin, and no control groups. Nebulized heparin in patients with COVID-19 needs to be studied further to determine its safety and effectiveness.

How to cite this article

Gupta B, Ahluwalia P, Gupta N, Gupta A. Role of Nebulized Heparin in Clinical Outcome of COVID-19 Patients with Respiratory Symptoms: A Systematic Review. Indian J Crit Care Med 2023;27(8):572-579.

Heparin, Low Molecular Weight Heparin, and Non-Anticoagulant Derivatives for the Treatment of Inflammatory Lung Disease

Unfractionated heparin has multiple pharmacological activities beyond anticoagulation. These anti-inflammatory, anti-microbial, and mucoactive activities are shared in part by low molecular weight and non-anticoagulant heparin derivatives. Anti-inflammatory activities include inhibition of chemokine activity and cytokine synthesis, inhibitory effects on the mechanisms of adhesion and diapedesis involved in neutrophil recruitment, inhibition of heparanase activity, inhibition of the proteases of the coagulation and complement cascades, inhibition of neutrophil elastase activity, neutralisation of toxic basic histones, and inhibition of HMGB1 activity. This review considers the potential for heparin and its derivatives to treat inflammatory lung disease, including COVID-19, ALI, ARDS, cystic fibrosis, asthma, and COPD via the inhaled route.

Inhaled nebulised unfractionated heparin (UFH) for the treatment of hospitalised patients with COVID-19: A randomised controlled pilot study

There is a strong scientific rationale to use nebulised unfractionated heparin (UFH) in treating patients with COVID-19. This pilot study investigated whether nebulised UFH was safe and had any impact on mortality, length of hospitalisation and clinical progression, in the treatment of hospitalised patients with COVID-19. This parallel group, open label, randomised trial included adult patients with confirmed SARS-CoV-2 infection admitted to two hospitals in Brazil. One hundred patients were planned to be randomised to either "standard of care" (SOC) or SOC plus nebulized UFH. The trial was stopped after randomisation of 75 patients due to falling COVID-19 hospitalisation rates. Significance tests were 1-sided test (10% significance level). The key analysis populations were intention to treat (ITT) and modified ITT (mITT) which excluded (from both arms) subjects admitted to ITU or who died within 24 h of randomisation. In the ITT population (n = 75), mortality was numerically lower for nebulised UFH (6 out of 38 patients; 15.8%) versus SOC (10 out of 37 patients; 27.0%), but not statistically significant; odds ratio (OR) 0.51, p = 0.24. However, in the mITT population, nebulised UFH reduced mortality (OR 0.2, p = 0.035). Length of hospital stay was similar between groups, but at day 29, there was a greater improvement in ordinal score following treatment with UFH in the ITT and mITT populations (p = 0.076 and p = 0.012 respectively), while mechanical ventilation rates were lower with UFH in the mITT population (OR 0.31; p = 0.08). Nebulised UFH did not cause any significant adverse events. In conclusion, nebulised UFH added to SOC in hospitalised patients with COVID-19 was well tolerated and showed clinical benefit, particularly in patients who received at least 6 doses of heparin. This trial was funded by The J.R. Moulton Charity Trust and registered under REBEC RBR-8r9hy8f (UTN code: U1111-1263-3136).

Protective Effect of Nebulized Heparin in the Animal Models of Smoke Inhalation Injury: A Meta-analysis and Systematic Review of Experimental Studies

The pathophysiological mechanism of abnormal coagulation can result from smoke inhalation injury (SII). Heparin nebulization is a common treatment for lung disorders. This study aimed to use meta-analysis in animal models to examine the effectiveness of atomized heparin on SII. For our online searches, we used the Cochrane Central Register of Controlled Trials, PubMed, Web of Science, Chinese National Knowledge Infrastructure, Chinese BioMedical Literature Database, and Wanfang Database up to January 2022. Data for SII were retrieved and compared to control animals. The studies' findings were determined by combining standardized mean difference (SMD) analysis with 95% confidence intervals (CIs). The findings showed that as compared to the control group, the heparin-treated group had a lower death rate (relative risk 0.42; 95% CI 0.22, 0.80; p < .05). The meta-analysis demonstrated favorable changes in lung physiology, including PaO2/FiO2 (SMD 1.04; 95% CI 0.65, 1.44; p < .001), lung wet-to-dry weight ratio (SMD -1.83; 95% CI -2.47, -1.18; p < .001), and pulmonary shunt Qs/Qt (SMD -0.69; 95% CI -1.29, -0.08; p < .05) after heparin nebulization for lung injury. The present data indicated that pulmonary artery mean pressure in the heparin therapy group was significantly lowered after 24 and 48 hours of therapy, suggesting that the cardiovascular system could recover following heparin treatment. As a result, heparin nebulization appeared to be more effective against SII and improved cardiopulmonary function compared to the control group. Graphical Abstract.

Anticoagulant Treatment in Severe ARDS COVID-19 Patients

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

Can nebulised HepArin Reduce morTality and time to Extubation in Patients with COVID-19 Requiring invasive ventilation Meta-Trial (CHARTER-MT): Protocol and Statistical Analysis Plan for an investigator-initiated international meta-trial of prospective randomised clinical studies

There is significant interest in the potential for nebulised unfractionated heparin (UFH) as a novel therapy for patients with COVID-19 induced acute hypoxaemic respiratory failure requiring invasive ventilation. The scientific and biological rationale for nebulised heparin stems from the evidence for extensive activation of coagulation resulting in pulmonary microvascular thrombosis in COVID-19 pneumonia. Nebulised delivery of heparin to the lung may limit alveolar fibrin deposition and thereby limit progression of lung injury. Importantly, laboratory studies show that heparin can directly inactivate the SARS-CoV-2 virus, thereby prevent its entry into and infection of mammalian cells. UFH has additional anti-inflammatory and mucolytic properties that may be useful in this context. METHODS AND INTERVENTION: The Can nebulised HepArin Reduce morTality and time to Extubation in Patients with COVID-19 Requiring invasive ventilation Meta-Trial (CHARTER-MT) is a collaborative prospective individual patient data analysis of on-going randomised controlled clinical trials across several countries in 5 continents, examining the effects of inhaled heparin in patients with COVID-19 requiring invasive ventilation on various endpoints. Each constituent study will randomise patients with COVID-19 induced respiratory failure requiring invasive ventilation. Patients are randomised to receive nebulised heparin or standard care (open label studies) or placebo (blinded placebo-controlled studies) while under invasive ventilation. Each participating study collect a pre-defined minimum dataset. The primary outcome for the meta-trial is the number of ventilator-free days up to day 28 day, defined as days alive and free from invasive ventilation. ETHICS AND DISSEMINATION: The meta-trial is registered at ClinicalTrials.gov ID NCT04545541. Each contributing study is individually registered and has received approval of the relevant ethics committee or institutional review board. Results of this study will be shared with the WHO, published in scientific journals, and presented at scientific meetings.

Inhaled nebulised unfractionated heparin for the treatment of hospitalised patients with COVID-19: A multicentre case series of 98 patients

OBJECTIVE

To determine the safety and efficacy-potential of inhaled nebulised unfractionated heparin (UFH) in the treatment of hospitalised patients with COVID-19.

METHODS

Retrospective, uncontrolled multicentre single-arm case series of hospitalised patients with laboratory-confirmed COVID-19, treated with inhaled nebulised UFH (5000IU 8-hourly, 10000IU 4-hourly, or 25000IU 6-hourly) for 6±3 (mean±SD) days. Outcomes were APTT before treatment (baseline) and highest-level during treatment (peak), and adverse events including bleeding. Exploratory efficacy outcomes were oxygenation, assessed by SpO2 to FiO2 (S/F) ratio and FiO2, and the WHO modified ordinal clinical scale (MOCS).

RESULTS

98 patients were included. In patients on stable prophylactic or therapeutic systemic anticoagulant therapy but not receiving therapeutic UFH infusion, APTT levels increased from baseline of 34±10 seconds to a peak of 38±11 seconds (p<0.0001). In 3 patients on therapeutic UFH infusion, APTT levels did not significantly increase from baseline of 72±20 to a peak of 84±28 seconds (p=0.17). Two patients had serious adverse events: bleeding gastric ulcer requiring transfusion; thigh haematoma; both were on therapeutic anticoagulation. Minor bleeding occurred in 16 patients, 13 of which were on therapeutic anticoagulation. The S/F ratio and the FiO2 worsened before and improved after commencement of inhaled UFH (change in slope, p<0.001).

CONCLUSION

Inhaled nebulised UFH in hospitalised patients with COVID-19 was safe. Although statistically significant, inhaled nebulised UFH did not produce a clinically relevant increase in APTT (peak values in the normal range). Urgent randomised evaluation of nebulised UFH in patients with COVID-19 is warranted and several studies are currently underway.

Nebulized enriched heparin to treat no critical patients with Sars-Cov-2: Triple-blind clinical trial

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a viral respiratory disease that spreads rapidly, reaching pandemic status, causing the collapse of numerous health systems, and a strong economic and social impact. The treatment so far has not been well established and there are several clinical trials testing known drugs that have antiviral activity, due to the urgency that the global situation imposes. Drugs with specific mechanisms of action can take years to be discovered, while vaccines may also take a long time to be widely distributed while new virus variants emerge. Thus, drug repositioning has been shown to be a good strategy for defining new therapeutic approaches. Studies of the effect of enriched heparin in the replication of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) in vitro assays justify the advance for clinical tests.

METHODS AND ANALYSIS

A phase I/II triple-blind parallel clinical trial will be conducted. Fifty participants with radiological diagnosis of grade IIA pneumonia will be selected, which will be allocated in 2 arms. Participants allocated in Group 1 (placebo) will receive nebulized 0.9% saline. Participants allocated in Group 2 (intervention) will receive nebulized enriched heparin (2.5 mg/mL 0.9% saline). Both groups will receive the respective solutions on a 4/4 hour basis, for 7 days. The main outcomes of interest will be safety (absence of serious adverse events) and efficacy (measured by the viral load).Protocols will be filled on a daily basis, ranging from day 0 (diagnosis) until day 8.

Effect of Nebulized Heparin on Weaning off Intubated Patients with Acute Respiratory Distress Syndrome (ARDS) Admitted to Intensive Care Unit (ICU): A Randomized Clinical Trial

Background: Acute respiratory distress syndrome (ARDS) treatment is based on supportive care such as mechanical ventilation, prophylaxis of stress ulcer, prophylaxis of deep vein thrombosis (DVT), nutritional support, and treatment of underlying disease. Objectives: We aimed to investigate the effects of nebulized heparin on weaning off intubated ARDS patients admitted to the intensive care unit (ICU). Methods: In this double-blind clinical trial study, 60 patients with ARDS receiving routine care according to the ARDS protocol were randomly assigned into two groups: intervention group (receiving nebulized heparin 5000 u/BD for one week) and control group (receiving nebulized sterile water 2 cc/BD for one week). The respiratory index (PaO2/FiO2), pulmonary shunt percentage (measured by ABG), tidal volume, minute ventilation, admission duration in the ICU, and days of mechanical ventilation required were recorded for each patient for one week. Results: There was no significant difference in demographic data between the two groups. Inhaled heparin in patients with ARDS could significantly increase the respiratory index (PaO2/FiO2) and decrease pulmonary shunt percentage, minute ventilation, and tidal volume. It also significantly reduced the number of admission days in the ICU and the need for mechanical ventilation. Conclusions: The result of the present study showed that inhaled heparin in intubated ARDS patients admitted to the ICU improved respiratory and pulmonary status and reduced the need for mechanical ventilation and admission days in the ICU. Nebulizing heparin, as an anti-inflammatory and anti-coagulant agent, is an effective and safe medication for ARDS patients on mechanical ventilation.

Early Effects of Low Molecular Weight Heparin Therapy with Soft-Mist Inhaler for COVID-19-Induced Hypoxemia: A Phase IIb Trial

In COVID-19-induced acute respiratory distress syndrome, the lungs are incapable of filling with sufficient air, leading to hypoxemia that results in high mortality among hospitalized patients. In clinical trials, low-molecular-weight heparin was administered via a specially designed soft-mist inhaler device in an investigator initiated, single-center, open-label, phase-IIb clinical trial. Patients with evidently worse clinical presentations were classed as the “Device Group”; 40 patients were given low-molecular-weight heparin via a soft mist inhaler at a dose of 4000 IU per administration, twice a day. The Control Group, also made up of 40 patients, received the standard therapy. The predetermined severity of hypoxemia and the peripheral oxygen saturation of patients were measured on the 1st and 10th days of treatment. The improvement was particularly striking in cases of severe hypoxemia. In the 10-day treatment, low-molecular-weight heparin was shown to significantly improve breathing capability when delivered via a soft-mist inhaler.

Inhalation Injury is Associated with Endotheliopathy and Abnormal Fibrinolytic Phenotypes in Burn Patients: A Cohort Study

Burn injury is associated with endothelial dysfunction and coagulopathy and concomitant inhalation injury increases morbidity and mortality. The aim of this work is to identify associations between inhalation injury (IHI), coagulation homeostasis, vascular endothelium, and clinical outcomes in burn patients. One-hundred and twelve patients presenting to a regional burn center were included in this retrospective cohort study. Whole blood was collected at set intervals from admission through 24 hours and underwent viscoelastic assay with rapid TEG (rTEG). Syndecan-1 (SDC-1) on admission was quantified by ELISA. Patients were grouped by the presence (n=28) or absence (n=84) of concomitant IHI and rTEG parameters, fibrinolytic phenotypes, SDC-1, and clinical outcomes were compared. Of the 112 thermally injured patients, 28 (25%) had IHI. Most patients were male (68.8%) with a median age of 40 (IQR, 29-57) years. Patients with IHI had higher overall mortality (42.68% vs. 8.3%; p<0.0001). rTEG LY30 was lower in patients with IHI at hours 4 and 12 (p<0.05). There was a pattern of increased abnormal fibrinolytic phenotypes among IHI patients. There was a greater proportion of IHI patients with endotheliopathy (SDC-1 > 34 ng/mL) (64.7% vs. 26.4%; p=0.008). There was a pattern of increased mortality among patients with inhalation injury and endotheliopathy (0% vs. 72.7%; p=0.004). Significant differences between patients with and without IHI were found in measures assessing fibrinolytic potential and endotheliopathy. Mortality was associated with abnormal fibrinolysis, endotheliopathy, and inhalation injury. However, the extent to which IHI associated dysfunction is independent of TBSA burn size remains to be elucidated.

Pharmacological and clinical application of heparin progress: An essential drug for modern medicine

Heparin is the earliest and most widely used anticoagulant and antithrombotic drug that is still used in a variety of clinical indications. Since it was discovered in 1916, after more than a century of repeated exploration, heparin has not been replaced by other drugs, but a great progress has been made in its basic research and clinical application. Besides anticoagulant and antithrombotic effects, heparin also has antitumor, anti-inflammatory, antiviral, and other pharmacological activities. It is widely used clinically in cardiovascular and cerebrovascular diseases, lung diseases, kidney diseases, cancer, etc., as the first anticoagulant medicine in COVID-19 exerts anticoagulant, anti-inflammatory and antiviral effects. At the same time, however, it also leads to a lot of adverse reactions, such as bleeding, thrombocytopenia, elevated transaminase, allergic reactions, and others. This article comprehensively reviews the modern research progress of heparin compounds; discusses the structure, preparation, and adverse reactions of heparin; emphasizes the pharmacological activity and clinical application of heparin; reveals the possible mechanism of the therapeutic effect of heparin in related clinical applications; provides evidence support for the clinical application of heparin; and hints on the significance of exploring the wider application fields of heparin.

Nebulised heparin for patients with or at risk of acute respiratory distress syndrome: a multicentre, randomised, double-blind, placebo-controlled phase 3 trial

Background

Mechanical ventilation in intensive care for 48 h or longer is associated with the acute respiratory distress syndrome (ARDS), which might be present at the time ventilatory support is instituted or develop afterwards, predominantly during the first 5 days. Survivors of prolonged mechanical ventilation and ARDS are at risk of considerably impaired physical function that can persist for years. An early pathogenic mechanism of lung injury in mechanically ventilated, critically ill patients is inflammation-induced pulmonary fibrin deposition, leading to thrombosis of the microvasculature and hyaline membrane formation in the air sacs. The main aim of this study was to determine if nebulised heparin, which targets fibrin deposition, would limit lung injury and thereby accelerate recovery of physical function in patients with or at risk of ARDS.

Methods

The Can Heparin Administration Reduce Lung Injury (CHARLI) study was an investigator-initiated, multicentre, double-blind, randomised phase 3 trial across nine hospitals in Australia. Adult intensive care patients on invasive ventilation, with impaired oxygenation defined by a PaO₂/FiO₂ ratio of less than 300, and with the expectation of invasive ventilation beyond the next calendar day were recruited. Key exclusion criteria were heparin allergy, pulmonary bleeding, and platelet count less than 50 X 10⁹/L. Patients were randomly assigned 1:1, with stratification by site and using blocks of variable size and random seed, via a web-based system, to either unfractionated heparin sodium 25 000 IU in 5 mL or identical placebo (sodium chloride 0·9% 5 mL), administered using a vibrating mesh membrane nebuliser every 6 h to day 10 while invasively ventilated. Patients, clinicians, and investigators were masked to treatment allocation. The primary outcome was the Short Form 36 Health Survey Physical Function Score (out of 100) of survivors at day 60. Prespecified secondary outcomes, which are exploratory, included development of ARDS to day 5 among at-risk patients, deterioration of the Murray Lung Injury Score (MLIS) to day 5, mortality at day 60, residence of survivors at day 60, and serious adverse events. Analyses followed the intention-to-treat principle. There was no imputation of missing data. The trial is registered with the Australian and New Zealand Clinical Trials Register, number ACTRN12612000418875 .

Findings

Between Sept 4, 2012, and Aug 23, 2018, 256 patients were randomised. Final follow-up was on Feb 25, 2019. We excluded three patients who revoked consent and one ineligible participant who received no intervention. Of 252 patients included in data analysis, the mean age was 58 years (SD 15), 157 (62%) were men, and 118 (47%) had ARDS. 128 (51%) patients were assigned to the heparin group and 124 (49%) to the placebo group, all of whom received their assigned intervention. Survivors in the heparin group (n=97) had similar SF-36 Physical Function Scores at day 60 compared to the placebo group (n=94; mean 53·6 [SD 31·6] vs 48·7 [35·7]; difference 4·9 [95% CI −4·8 to 14·5]; p=0·32). Compared with the placebo group, the heparin group had fewer cases of ARDS develop to day 5 among the at-risk patients (nine [15%] of 62 patients vs 21 [30%] of 71 patients; hazard ratio 0·46 [95% CI 0·22 to 0·98]; p=0·0431), less deterioration of the MLIS to day 5 (difference −0·14 [–0·26 to −0·02]; p=0·0215), similar day 60 mortality (23 [18%] of 127 patients vs 18 [15%] of 123 patients; odds ratio [OR] 1·29 [95% CI 0·66 to 2·53]; p=0·46), and more day 60 survivors at home (86 [87%] of 99 patients vs 73 [73%] of 100 patients; OR 2·45 [1·18 to 5·08]; p=0·0165). A similar number of serious adverse events occurred in each group (seven [5%] of 128 patients in the heparin group vs three [2%] of 124 patients in the placebo group; OR 2·33 [0·59 to 9·24]; p=0·23), which were a transient increase in airway pressure during nebulisation (n=3 in the heparin group), major non-pulmonary bleeding (n=2 in each group), haemoptysis (n=1 in the heparin group), tracheotomy site bleeding (n=1 in the heparin group), and hypoxaemia during nebulisation (n=1 in the placebo group).

Interpretation

In patients with or at risk of ARDS, nebulised heparin did not improve self-reported performance of daily physical activities, but was well tolerated and exploratory outcomes suggest less progression of lung injury and earlier return home. Further research is justified to establish if nebulised heparin accelerates recovery in those who have or are at risk of ARDS.

Funding

Rowe Family Foundation, TR and RB Ditchfield Medical Research Endowment Fund, Patricia Madigan Charitable Trust, and The J and R McGauran Trust Fund.

INHALEd nebulised unfractionated HEParin for the treatment of hospitalised patients with COVID-19 (INHALE-HEP): Protocol and statistical analysis plan for an investigator-initiated international metatrial of randomised studies

AIMS

Inhaled nebulised unfractionated heparin (UFH) has a strong scientific and biological rationale that warrants urgent investigation of its therapeutic potential in patients with COVID-19. UFH has antiviral effects and prevents the SARS-CoV-2 virus' entry into mammalian cells. In addition, UFH has significant anti-inflammatory and anticoagulant properties, which limit progression of lung injury and vascular pulmonary thrombosis.

METHODS

The INHALEd nebulised unfractionated HEParin for the treatment of hospitalised patients with COVID-19 (INHALE-HEP) metatrial is a prospective individual patient data analysis of on-going randomised controlled trials and early phase studies. Individual studies are being conducted in multiple countries. Participating studies randomise adult patients admitted to the hospital with confirmed SARS-CoV-2 infection, who do not require immediate mechanical ventilation, to inhaled nebulised UFH or standard care. All studies collect a minimum core dataset. The primary outcome for the metatrial is intubation (or death, for patients who died before intubation) at day 28. The secondary outcomes are oxygenation, clinical worsening and mortality, assessed in time-to-event analyses. Individual studies may have additional outcomes.

ANALYSIS

We use a Bayesian approach to monitoring, followed by analysing individual patient data, outcomes and adverse events. All analyses will follow the intention-to-treat principle, considering all participants in the treatment group to which they were assigned, except for cases lost to follow-up or withdrawn.

TRIAL REGISTRATION, ETHICS AND DISSEMINATION

The metatrial is registered at ClinicalTrials.gov ID NCT04635241. Each contributing study is individually registered and has received approval of the relevant ethics committee or institutional review board. Results of this study will be shared with the World Health Organisation, published in scientific journals and presented at scientific meetings.

The Association of Low Molecular Weight Heparin Use and In-hospital Mortality Among Patients Hospitalized with COVID-19

Purpose

To determine the association between low molecular weight heparin (LMWH) use and mortality in hospitalized COVID-19 patients.

Methods

We conducted a retrospective study of patients consecutively enrolled from two major academic hospitals exclusively for COVID-19 in Wuhan, China, from January 26, 2020, to March 26, 2020. The primary outcome was adjusted in-hospital mortality in the LMWH group compared with the non-LMWH group using the propensity score.

Results

Overall, 525 patients with COVID-19 enrolled with a median age of 64 years (IQR 19), and 49.33% men. Among these, 120 (22.86%) were treated with LMWH. Compared with the non-LMWH group, the LMWH group was more likely to be older and male; had a history of hypertension, diabetes, coronary heart disease (CHD), or stroke; and had more severe COVID-19 parameters such as higher inflammatory cytokines or D-dimer. Compared with non-LMWH group, LMWH group had a higher unadjusted in-hospital mortality rate (21.70% vs. 11.10%; p = 0.004), but a lower adjusted mortality risk (adjusted odds ratio [OR], 0.20; 95% CI, 0.09–0.46). A propensity score-weighting analysis demonstrated similar findings (adjusted OR, 0.18; 95% CI, 0.10–0.30). Subgroup analysis showed a significant survival benefit among those who were severely (adjusted OR, 0.07; 95% CI, 0.02–0.23) and critically ill (adjusted OR, 0.32; 95% CI, 0.15–0.65), as well as among the elderly patients’ age > 65, IL-6 > 10 times upper limit level, and D-dimer > 5 times upper limit level.

Conclusions

Among hospitalized COVID-19 patients, LMWH use was associated with lower all-cause in-hospital mortality than non-LMWH users. The survival benefit was particularly significant among more severely ill patients.

Animal models of mechanisms of SARS-CoV-2 infection and COVID-19 pathology

The coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 infections has led to a substantial unmet need for treatments, many of which will require testing in appropriate animal models of this disease. Vaccine trials are already underway, but there remains an urgent need to find other therapeutic approaches to either target SARS-CoV-2 or the complications arising from viral infection, particularly the dysregulated immune response and systemic complications which have been associated with progression to severe COVID-19. At the time of writing, in vivo studies of SARS-CoV-2 infection have been described using macaques, cats, ferrets, hamsters, and transgenic mice expressing human angiotensin I converting enzyme 2 (ACE2). These infection models have already been useful for studies of transmission and immunity, but to date only partly model the mechanisms involved in human severe COVID-19. There is therefore an urgent need for development of animal models for improved evaluation of efficacy of drugs identified as having potential in the treatment of severe COVID-19. These models need to reproduce the key mechanisms of COVID-19 severe acute respiratory distress syndrome and the immunopathology and systemic sequelae associated with this disease. Here, we review the current models of SARS-CoV-2 infection and COVID-19-related disease mechanisms and suggest ways in which animal models can be adapted to increase their usefulness in research into COVID-19 pathogenesis and for assessing potential treatments. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

The hypercoagulable state in COVID-19: Incidence, pathophysiology, and management

The 2019 coronavirus disease (COVID-19) presents with a large variety of clinical manifestations ranging from asymptomatic carrier state to severe respiratory distress, multiple organ dysfunction and death. While it was initially considered primarily a respiratory illness, rapidly accumulating data suggests that COVID-19 results in a unique, profoundly prothrombotic milieu leading to both arterial and venous thrombosis. Consistently, elevated D-dimer level has emerged as an independent risk factor for poor outcomes, including death. Several other laboratory markers and blood counts have also been associated with poor prognosis, possibly due to their connection to thrombosis. At present, the pathophysiology underlying the hypercoagulable state is poorly understood. However, a growing body of data suggests that the initial events occur in the lung. A severe inflammatory response, originating in the alveoli, triggers a dysfunctional cascade of inflammatory thrombosis in the pulmonary vasculature, leading to a state of local coagulopathy. This is followed, in patients with more severe disease, by a generalized hypercoagulable state that results in macro- and microvascular thrombosis. Of concern, is the observation that anticoagulation may be inadequate in many circumstances, highlighting the need for alternative or additional therapies. Numerous ongoing studies investigating the pathophysiology of the COVID-19 associated coagulopathy may provide mechanistic insights that can direct appropriate interventional strategies.

Thromboinflammation in COVID-19 acute lung injury

Since the initial description in 2019, the novel coronavirus SARS-Cov-2 infection (COVID-19) pandemic has swept the globe. The most severe form of the disease presents with fever and shortness of breath, which rapidly deteriorates to respiratory failure and acute lung injury (ALI). COVID-19 also presents with a severe coagulopathy with a high rate of venous thromboembiolism. In addition, autopsy studies have revealed co-localized thrombosis and inflammation, which is the signature of thromboinflammation, within the pulmonary capillary vasculature. While the majority of published data is on adult patients, there are parallels to pediatric patients. In our experience as a COVID-19 epicenter, children and young adults do develop both the coagulopathy and the ALI of COVID-19. This review will discuss COVID-19 ALI from a hematological perspective with discussion of the distinct aspects of coagulation that are apparent in COVID-19. Current and potential interventions targeting the multiple thromboinflammatory mechanisms will be discussed.

Nebulised heparin as a treatment for COVID-19: scientific rationale and a call for randomised evidence

Nebulised unfractionated heparin (UFH) has a strong scientific and biological rationale and warrants urgent investigation of its therapeutic potential, for COVID-19-induced acute respiratory distress syndrome (ARDS). COVID-19 ARDS displays the typical features of diffuse alveolar damage with extensive pulmonary coagulation activation resulting in fibrin deposition in the microvasculature and formation of hyaline membranes in the air sacs. Patients infected with SARS-CoV-2 who manifest severe disease have high levels of inflammatory cytokines in plasma and bronchoalveolar lavage fluid and significant coagulopathy. There is a strong association between the extent of the coagulopathy and poor clinical outcomes.The anti-coagulant actions of nebulised UFH limit fibrin deposition and microvascular thrombosis. Trials in patients with acute lung injury and related conditions found inhaled UFH reduced pulmonary dead space, coagulation activation, microvascular thrombosis and clinical deterioration, resulting in increased time free of ventilatory support. In addition, UFH has anti-inflammatory, mucolytic and anti-viral properties and, specifically, has been shown to inactivate the SARS-CoV-2 virus and prevent its entry into mammalian cells, thereby inhibiting pulmonary infection by SARS-CoV-2. Furthermore, clinical studies have shown that inhaled UFH safely improves outcomes in other inflammatory respiratory diseases and also acts as an effective mucolytic in sputum-producing respiratory patients. UFH is widely available and inexpensive, which may make this treatment also accessible for low- and middle-income countries.These potentially important therapeutic properties of nebulised UFH underline the need for expedited large-scale clinical trials to test its potential to reduce mortality in COVID-19 patients.

Nebulized heparin and salbutamol versus salbutamol alone in acute exacerbations of chronic obstructive pulmonary disease requiring mechanical ventilation: a double-blind randomized controlled trial

Background

Nebulized heparin has been effectively used in the management of many pulmonary diseases. However, its effect on mechanically ventilated patients with acute exacerbation chronic obstructive pulmonary disease (AECOPD) has never been studied. This study aimed to assess the efficacy of nebulized heparin and salbutamol to increase ventilator-free days (VFD) in mechanically ventilated AECOPD patients and the effect of nebulized heparin on respiratory and coagulation functions.

Methods

In this double-blind controlled study, 60 mechanically ventilated adult patients with AECOPD were randomly allocated into two groups; heparin and salbutamol (HS) group and salbutamol only (S) group. In the HS group, patients received nebulized heparin (25,000 IU) and salbutamol (5 mg) every 6 hours. Patients in the S group received nebulized salbutamol only (5 mg). The treatment was continued while patients remained ventilated for a maximum of 14 days. The primary outcome was VFDs at day 14. PaCO2, PaO2/FiO2 ratio, number of nebulizations withheld, C-reactive protein (CRP) titer and activated partial thromboplastin time (APTT) were secondary outcomes.

Results

Patients in the Group HS had significantly more VFDs 4.7 ± 3.3 compared with those in the Group S 2.4 ± 2.6, P = 0.007. PaCO2 levels, PaO2/FiO2, the decrease in the CRP level and the increase in the APTT from the baseline showed no evidence of difference in both groups.

Conclusions

The co-administration of nebulized heparin and salbutamol, compared with salbutamol alone, significantly increased (VFDs) among mechanically ventilated AECOPD patients without increasing bleeding risks.

Anticoagulant therapy in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) presents a complex pathophysiology characterized by pulmonary activated coagulation and reduced fibrinolysis. Despite advances in supportive care of this syndrome, morbidity and mortality remains high, leading to the need of novel therapies to combat this disease. Focus these therapies in the inhibition of ARDS development pathophysiology is essential. Beneficial effects of anticoagulants in ARDS have been proved in preclinical and clinical trials, thanks to its anticoagulant and anti-inflammatory properties. Moreover, local administration by nebulization in the alveolar compartment increases local efficacy and does not produce systemic bleeding. In this review the coagulation and fibrinolytic pathway and its pharmacological targets to treat ARDS are summarized.

Nebulized Heparin Attenuates Pulmonary Coagulopathy and Inflammation through Alveolar Macrophages in a Rat Model of Acute Lung Injury

Objective  Alveolar macrophages play a key role in the development and resolution of acute respiratory distress syndrome (ARDS), modulating the inflammatory response and the coagulation cascade in lungs. Anti-coagulants may be helpful in the treatment of ARDS. This study investigated the effects of nebulized heparin on the role of alveolar macrophages in limiting lung coagulation and inflammatory response in an animal model of acute lung injury (ALI).

Methods  Rats were randomized to four experimental groups. In three groups, ALI was induced by intratracheal instillation of lipopolysaccharide (LPS) and heparin was nebulized at constant oxygen flow: the LPS/Hep group received nebulized heparin 4 and 8 hours after injury; the Hep/LPS/Hep group received nebulized heparin 30 minutes before and 4 and 8 hours after LPS-induced injury; the LPS/Sal group received nebulized saline 4 and 8 hours after injury. The control group received only saline. Animals were exsanguinated 24 hours after LPS instillation. Lung tissue, bronchoalveolar lavage fluid (BALF) and alveolar macrophages isolated from BALF were analysed.

Results  LPS increased protein concentration, oedema and neutrophils in BALF as well as procoagulant and proinflammatory mediators in lung tissue and alveolar macrophages. In lung tissue, nebulized heparin attenuated ALI through decreasing procoagulant (tissue factor, thrombin–anti-thrombin complexes, fibrin degradation products) and proinflammatory (interleukin 6, tumour necrosis factor alpha) pathways. In alveolar macrophages, nebulized heparin reduced expression of procoagulant genes and the effectors of transforming growth factor beta (Smad 2, Smad 3) and nuclear factor kappa B (p-selectin, CCL-2). Pre-treatment resulted in more pronounced attenuation.

Conclusion  Nebulized heparin reduced pulmonary coagulopathy and inflammation without producing systemic bleeding, partly by modulating alveolar macrophages.

Nebulized anticoagulants in lung injury in critically ill patients-an updated systematic review of preclinical and clinical studies

Pneumonia, inhalation trauma and acute respiratory distress syndrome (ARDS), typical causes of lung injury in critically ill patients, are all three characterized by dysregulated inflammation and coagulation in the lungs. Nebulized anticoagulants are thought to have beneficial effects as they could attenuate pulmonary coagulopathy and maybe even affect pulmonary inflammation. A systematic search of the medical literature was performed using terms referring to aspects of the condition ('pneumonia', 'inhalation trauma' and 'ARDS'), the intervention ('nebulized', 'vaporized', and 'aerosolized') and anticoagulants limited to agents that are commercially available and frequently given or tested in critically ill patients ['heparin', 'danaparoid', 'activated protein C' (APC), 'antithrombin' (AT) and 'tissue factor pathway inhibitor' (TFPI)]. The systematic search identified 16 articles reporting on preclinical studies and 11 articles reporting on human trials. All nebulized anticoagulants attenuate pulmonary coagulopathy in preclinical studies using various models for lung injury, but the effects on inflammation are less consistent. Nebulized heparin, danaparoid and TFPI, but not APC and AT also reduced systemic coagulation. Nebulized heparin in lung injury patients shows contradictory results, and there is concern over systemic side effects of this strategy. Future studies need to focus on the way to nebulize anticoagulants, as well as on efficient but safe dosages, and other side effects.

Role of heparin in pulmonary cell populations in an in-vitro model of acute lung injury

Background

In the early stages of acute respiratory distress syndrome (ARDS), pro-inflammatory mediators inhibit natural anticoagulant factors and initiate an increase in procoagulant activity. Previous studies proved the beneficial effects of heparin in pulmonary coagulopathy, which derive from its anticoagulant and anti-inflammatory activities, although it is uncertain whether heparin works. Understanding the specific effect of unfractioned heparin on cell lung populations would be of interest to increase our knowledge about heparin pathways and to treat ARDS.

Methods

In the current study, the effect of heparin was assessed in primary human alveolar macrophages (hAM), alveolar type II cells (hATII), and fibroblasts (hF) that had been injured with LPS.

Results

Heparin did not produce any changes in the Smad/TGFß pathway, in any of the cell types evaluated. Heparin reduced the expression of pro-inflammatory markers (TNF-α and IL-6) in hAM and deactivated the NF-kß pathway in hATII, diminishing the expression of IRAK1 and MyD88 and their effectors, IL-6, MCP-1 and IL-8.

Conclusions

The current study demonstrated that heparin significantly ameliorated the cells lung injury induced by LPS through the inhibition of pro-inflammatory cytokine expression in macrophages and the NF-kß pathway in alveolar cells. Our results suggested that a local pulmonary administration of heparin through nebulization may be able to reduce inflammation in the lung; however, further studies are needed to confirm this hypothesis.

A Pilot Study of Nebulized Heparin for Prevention of Ventilator Induced Lung Injury: Comparative Effects with an Inhaled Corticosteroid

Background:

Ventilator-induced lung injury (VILI) is a side effect of mechanical ventilation. Lung inflammation and pulmonary activation of coagulation are induced by mechanical stress. Clinical and preclinical studies show that heparin possesses anti-inflammatory properties. Therefore, we assessed the effects of nebulized heparin in VILI.

Methods:

Sixty critically ill adult patients who require mechanical ventilation for more than 48 h were included in this prospective, nonrandomized controlled study. Patients received nebulized heparin (10,000 U every 6 h) for 5 days. The matched control group received nebulized budesonide as routine practice in our center. This study assessed changes in partial pressure of oxygen to inspired fraction of oxygen ratio (PaO₂/FiO₂) and rapid shallow breathing index (RSBI) during the study as primary endpoints.

Results:

The average daily PaO₂/FiO₂ ratio was not statistically significant between both groups (187 ± 11.6 vs. 171 ± 11.6, P = 0.35). The RSBI also did not differ between groups (P = 0.58). Heparin administration was associated with a higher number of ventilator-free days among survivors but not significantly (7.7 ± 10.6 vs. 5.1 ± 8, 95% confidence interval − 2.2–7.5, P = 0.28). Successful weaning from mechanical ventilation was higher in the heparin group (P = 0.42). We did not observe any serious or increased adverse effects from nebulized heparin.

Conclusion:

The results of this study show that the overall effectiveness of nebulized heparin is at least as comparable with a potent corticosteroid (budesonide). Heparin could be a safe and effective modality for patients who at risk of VILI.

pRotective vEntilation with veno-venouS lung assisT in respiratory failure: A protocol for a multicentre randomised controlled trial of extracorporeal carbon dioxide removal in patients with acute hypoxaemic respiratory failure

One of the few interventions to demonstrate improved outcomes for acute hypoxaemic respiratory failure is reducing tidal volumes when using mechanical ventilation, often termed lung protective ventilation. Veno-venous extracorporeal carbon dioxide removal (vv-ECCO₂R) can facilitate reducing tidal volumes. pRotective vEntilation with veno-venouS lung assisT (REST) is a randomised, allocation concealed, controlled, open, multicentre pragmatic trial to determine the clinical and cost-effectiveness of lower tidal volume mechanical ventilation facilitated by vv-ECCO₂R in patients with acute hypoxaemic respiratory failure. Patients requiring intubation and mechanical ventilation for acute hypoxaemic respiratory failure will be randomly allocated to receive either vv-ECCO₂R and lower tidal volume mechanical ventilation or standard care with stratification by recruitment centre. There is a need for a large randomised controlled trial to establish whether vv-ECCO₂R in acute hypoxaemic respiratory failure can allow the use of a more protective lung ventilation strategy and is associated with improved patient outcomes.

Nebulized Recombinant Human Tissue Factor Pathway Inhibitor Attenuates Coagulation and Exerts Modest Anti-inflammatory Effects in Rat Models of Lung Injury

BACKGROUND

Critically ill patients are at a constant risk of direct (e.g., by pneumonia) or indirect lung injury (e.g., by sepsis). Excessive alveolar fibrin deposition is a prominent feature of lung injury, undermining pulmonary integrity and function.

METHODS

We examined the effect of local administration of recombinant human tissue factor pathway inhibitor (rh-TFPI), a natural anticoagulant, in two well-established models of lung injury in rats. Rats received intratracheal instillation of Pseudomonas aeruginosa, causing direct lung injury, or they received an intravenous injection of Escherichia coli lipopolysaccharide (LPS), causing indirect lung injury. Rats were randomized to local treatment with rh-TFPI or placebo through repeated nebulization.

RESULTS

Challenge with P. aeruginosa or LPS was associated with increased coagulation and decreased fibrinolysis in bronchoalveolar lavage fluid (BALF) and plasma. Rh-TFPI levels in BALF increased after nebulization, whereas plasma rh-TFPI levels remained low and systemic TFPI activity was not affected. Nebulization of rh-TFPI attenuated pulmonary and systemic coagulation in both models, without affecting fibrinolysis. Nebulization of rh-TFPI modestly reduced the inflammatory response and bacterial growth of P. aeruginosa in the alveolar compartment.

CONCLUSIONS

Local treatment with rh-TFPI does not alter systemic TFPI activity; however, it attenuates both pulmonary and systemic coagulopathy. Furthermore, nebulized rh-TFPI modestly reduces the pulmonary inflammatory response and allows increased bacterial clearance in rats with direct lung injury caused by P. aeruginosa.

Nebulized heparin for patients under mechanical ventilation: an individual patient data meta-analysis

Pulmonary coagulopathy is a characteristic feature of lung injury including ventilator-induced lung injury. The aim of this individual patient data meta-analysis is to assess the effects of nebulized anticoagulants on outcome of ventilated intensive care unit (ICU) patients. A systematic search of PubMed (1966-2014), Scopus, EMBASE, and Web of Science was conducted to identify relevant publications. Studies evaluating nebulization of anticoagulants in ventilated patients were screened for inclusion, and corresponding authors of included studies were contacted to provide individual patient data. The primary endpoint was the number of ventilator-free days and alive at day 28. Secondary endpoints included hospital mortality, ICU- and hospital-free days at day 28, and lung injury scores at day seven. We constructed a propensity score-matched cohort for comparisons between patients treated with nebulized anticoagulants and controls. Data from five studies (one randomized controlled trial, one open label study, and three studies using historical controls) were included in the meta-analysis, compassing 286 patients. In all studies unfractionated heparin was used as anticoagulant. The number of ventilator-free days and alive at day 28 was higher in patients treated with nebulized heparin compared to patients in the control group (14 [IQR 0-23] vs. 6 [IQR 0-22]), though the difference did not reach statistical significance (P = 0.459). The number of ICU-free days and alive at day 28 was significantly higher, and the lung injury scores at day seven were significantly lower in patients treated with nebulized heparin. In the propensity score-matched analysis, there were no differences in any of the endpoints. This individual patient data meta-analysis provides no convincing evidence for benefit of heparin nebulization in intubated and ventilated ICU patients. The small patient numbers and methodological shortcomings of included studies underline the need for high-quality well-powered randomized controlled trials.

A trial of nebulised heparin to limit lung injury following cardiac surgery

Cardiac surgery with cardiopulmonary bypass triggers an acute inflammatory response in the lungs. This response gives rise to fibrin deposition in the microvasculature and alveoli of the lungs. Fibrin deposition in the microvasculature increases alveolar dead space, while fibrin deposition in alveoli causes shunting. We investigated whether prophylactic nebulised heparin could limit this form of lung injury. We undertook a single-centre double-blind randomised trial. Forty patients undergoing elective cardiac surgery with cardiopulmonary bypass were randomised to prophylactic nebulised heparin (50,000 U) or placebo. The primary endpoint was the change in arterial oxygen levels over the operative period. Secondary endpoints included end-tidal CO₂, the alveolar dead space fraction and bleeding complications. We found nebulised heparin did not improve arterial oxygen levels. Nebulised heparin was, however, associated with a lower alveolar dead space fraction (P <0.05) and lower tidal volumes at the end of surgery (P <0.01). Nebulised heparin was not associated with bleeding complications. In conclusion, prophylactic nebulised heparin did not improve oxygenation, but was associated with evidence of better alveolar perfusion and CO₂elimination at the end of surgery.

The Acute Respiratory Distress Syndrome: Mechanisms and Perspective Therapeutic Approaches

Acute Respiratory Distress Syndrome (ARDS) is a severe lung inflammatory disorder with a 30-50% mortality. Sepsis and pneumonia are the leading causes of ARDS. On the cellular level there is pulmonary capillary endothelial cell permeability and fluid leakage into the pulmonary parenchyma, followed by neutrophils, cytokines and an acute inflammatory response. When fluid increases in the interstitium then the outward movement continues and protein rich fluid floods the alveolar spaces through the tight junctions of the epithelial cells. Neutrophils play an important role in the development of pulmonary edema associated with acute lung injury or ARDS. Animal studies have shown that endothelial injury appears within minutes to hours after Acute Lung Injury (ALI) initiation with resulting intercellular gaps of the endothelial cells. The Endothelial Cell (EC) gaps allow for permeability of fluid, neutrophils and cytokines into the pulmonary parenchymal space. The neutrophils that infiltrate the lungs and migrate into the airways express pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and contribute to both the endothelial and epithelial integrity disruption of the barriers. Pharmacological treatments have been ineffective. The ARDS Network trial identified low tidal volume mechanical ventilation, positive end expiratory pressure and fluid management guidelines that have improved outcomes for patients with ARDS. Extracorporeal membrane oxygenation is used in specialized centers for severe cases. Prone positioning has recently proven to have significantly decreased ventilator days and days in the intensive care unit. Current investigation includes administration of mesenchymal stem cell therapy, partial fluid ventilation, TIP peptide nebulized administration and the continued examination of pharmacologic drugs.

Feasibility and Safety of Local Treatment with Recombinant Human Tissue Factor Pathway Inhibitor in a Rat Model of Streptococcus pneumoniae Pneumonia

Pulmonary coagulopathy is intrinsic to pulmonary injury including pneumonia. Anticoagulant strategies could benefit patients with pneumonia, but systemic administration of anticoagulant agents may lead to suboptimal local levels and may cause systemic hemorrhage. We hypothesized nebulization to provide a safer and more effective route for local administration of anticoagulants. Therefore, we aimed to examine feasibility and safety of nebulization of recombinant human tissue factor pathway inhibitor (rh-TFPI) in a well-established rat model of Streptococcus (S.) pneumoniae pneumonia. Thirty minutes before and every 6 hours after intratracheal instillation of S. pneumonia causing pneumonia, rats were subjected to local treatment with rh-TFPI or placebo, and sacrificed after 42 hours. Pneumonia was associated with local as well as systemic activation of coagulation. Nebulization of rh-TFPI resulted in high levels of rh-TFPI in bronchoalveolar lavage fluid, which was accompanied by an attenuation of pulmonary coagulation. Systemic rh-TFPI levels remained undetectable, and systemic TFPI activity and systemic coagulation were not affected. Histopathology revealed no bleeding in the lungs. We conclude that nebulization of rh-TFPI seems feasible and safe; local anticoagulant treatment with rh-TFPI attenuates pulmonary coagulation, while not affecting systemic coagulation in a rat model of S. pneumoniae pneumonia.

Nebulized anticoagulants for acute lung injury - a systematic review of preclinical and clinical investigations

Background

Data from interventional trials of systemic anticoagulation for sepsis inconsistently suggest beneficial effects in case of acute lung injury (ALI). Severe systemic bleeding due to anticoagulation may have offset the possible positive effects. Nebulization of anticoagulants may allow for improved local biological availability and as such may improve efficacy in the lungs and lower the risk of systemic bleeding complications.

Method

We performed a systematic review of preclinical studies and clinical trials investigating the efficacy and safety of nebulized anticoagulants in the setting of lung injury in animals and ALI in humans.

Results

The efficacy of nebulized activated protein C, antithrombin, heparin and danaparoid has been tested in diverse animal models of direct (for example, pneumonia-, intra-pulmonary lipopolysaccharide (LPS)-, and smoke inhalation-induced lung injury) and indirect lung injury (for example, intravenous LPS- and trauma-induced lung injury). Nebulized anticoagulants were found to have the potential to attenuate pulmonary coagulopathy and frequently also inflammation. Notably, nebulized danaparoid and heparin but not activated protein C and antithrombin, were found to have an effect on systemic coagulation. Clinical trials of nebulized anticoagulants are very limited. Nebulized heparin was found to improve survival of patients with smoke inhalation-induced ALI. In a trial of critically ill patients who needed mechanical ventilation for longer than two days, nebulized heparin was associated with a higher number of ventilator-free days. In line with results from preclinical studies, nebulization of heparin was found to have an effect on systemic coagulation, but without causing systemic bleedings.

Conclusion

Local anticoagulant therapy through nebulization of anticoagulants attenuates pulmonary coagulopathy and frequently also inflammation in preclinical studies of lung injury. Recent human trials suggest nebulized heparin for ALI to be beneficial and safe, but data are very limited.

Early intravenous unfractionated heparin and outcome in acute lung injury and acute respiratory distress syndrome: a retrospective propensity matched cohort study

Background

Acute lung injury (ALI) is characterized by a pro-coagulant state. Heparin is an anticoagulant with anti-inflammatory properties. Unfractionated heparin has been found to be protective in experimental models of ALI. We hypothesized that an intravenous therapeutic dose of unfractionated heparin would favorably influence outcome of critically ill patients diagnosed with ALI.

Methods

Patients admitted to the Intensive Care Unit (ICU) of a tertiary referral center in the Netherlands between November 2004 and October 2007 were screened. Patients who developed ALI (consensus definition) were included. In this cohort, the impact of heparin use on mortality was assessed by logistic regression analysis in a propensity matched case–control design.

Results

Of 5,561 admitted patients, 2,138 patients had a length of stay > 48 hours, of whom 723 were diagnosed with ALI (34%), of whom 164 received intravenous heparin. In a propensity score adjusted logistic regression analysis, heparin use did not influence 28-day mortality (odds ratio 1.23 [confidence interval 95% 0.80–1.89], nor did it affect ICU length of stay.

Conclusions

Administration of therapeutic doses of intravenous unfractionated heparin was not associated with reduced mortality in critically ill patients diagnosed with ALI. Heparin treatment did not increase transfusion requirements. These results may help in the design of prospective trials evaluating the use of heparin as adjunctive treatment for ALI.

Tissue plasminogen activator attenuates ventilator-induced lung injury in rats

AIM

To test the hypothesis that the tissue plasminogen activator (tPA) may counteract the inhibitory effect of plasminogen activator inhibitors (PAI) and attenuate lung injury in a rat model of ventilator-induced lung injury (VILI).

METHODS

Adult male Sprague-Dawley rats were ventilated with a HVZP (high-volume zero PEEP) protocol for 2 h at a tidal volume of 30 mL/kg, a respiratory rate of 25 breaths/min, and an inspired oxygen fraction of 21%. The rats were divided into 3 groups (n=7 for each): HVZP+tPA group receiving tPA (1.25 mg/kg, iv) 15 min before ventilation, HVZP group receiving HVZP+vehicle injection, and a control group receiving no ventilation. After 2 h of ventilation, the rats were killed; blood and lungs were collected for biochemical and histological analyses.

RESULTS

HVZP ventilation significantly increased total protein content and the concentration of macrophage inflammatory protein-2 (MIP-2) in the bronchoalveolar lavage fluid (BALF) as well as the lung injury score. Rats that received HVZP ventilation had significantly higher lung PAI-1 mRNA expression, plasma PAI-1 and plasma D-dimer levels than the control animals. tPA treatment significantly reduced the BALF total protein and the lung injury score as compared to the HVZP group. tPA treatment also significantly decreased the plasma D-dimer levels and the HVZP ventilation-induced lung vascular fibrin thrombi. tPA treatment showed no effect on MIP-2 level in BALF.

CONCLUSION

These results demonstrate that VILI increases lung PAI-1 mRNA expression, plasma levels of PAI-1 and D-dimers, lung injury score and vascular fibrin deposition. tPA can attenuate VILI by decreasing capillary-alveolar protein leakage as well as local and systemic coagulation as shown by decreased lung vascular fibrin deposition and plasma D-dimers.

Nebulized heparin is associated with fewer days of mechanical ventilation in critically ill patients: a randomized controlled trial

Introduction

Prolonged mechanical ventilation has the potential to aggravate or initiate pulmonary inflammation and cause lung damage through fibrin deposition. Heparin may reduce pulmonary inflammation and fibrin deposition. We therefore assessed whether nebulized heparin improved lung function in patients expected to require prolonged mechanical ventilation.

Methods

Fifty patients expected to require mechanical ventilation for more than 48 hours were enrolled in a double-blind randomized placebo-controlled trial of nebulized heparin (25,000 U) or placebo (normal saline) 4 or 6 hourly, depending on patient height. The study drug was continued while the patient remained ventilated to a maximum of 14 days from randomization.

Results

Nebulized heparin was not associated with a significant improvement in the primary end-point, the average daily partial pressure of oxygen to inspired fraction of oxygen ratio while mechanically ventilated, but was associated with improvement in the secondary end-point, ventilator-free days amongst survivors at day 28 (22.6 ± 4.0 versus 18.0 ± 7.1, treatment difference 4.6 days, 95% CI 0.9 to 8.3, P = 0.02). Heparin administration was not associated with any increase in adverse events.

Conclusions

Nebulized heparin was associated with fewer days of mechanical ventilation in critically ill patients expected to require prolonged mechanical ventilation. Further trials are required to confirm these findings.

Trial registration

The Australian Clinical Trials Registry (ACTR-12608000121369).