Bronchoalveolar Activation of Coagulation and Inhibition of Fibrinolysis during Ventilator-Associated Lung Injury

Lung-borne systemic inflammation in mechanically ventilated infant rats due to high PEEP, oxygen, and hypocapnia

BACKGROUND

Intensive care practice calls for ventilator adjustments due to fast-changing clinical conditions in ventilated critically ill children. These adaptations include positive end-expiratory pressure (PEEP), fraction of inspired oxygen (FiO₂), and respiratory rate (RR). It is unclear which alterations in ventilator settings trigger a significant systemic inflammatory response.

METHODS

Fourteen-day old Wistar rat pups were randomized to the following groups: (a) "control" with tidal volume ~8 mL/kg, PEEP 5 cmH₂O, FiO₂ 0.4, RR 90 min^-1, (b) "PEEP 1", (c) "PEEP 9" (d) "FiO₂ 0.21", (e) "FiO₂ 1.0", (f) "hypocapnia" with RR of 180 min^-1, and (g) "hypercapnia" with RR of 60 min^-1. Following 120 min of mechanical ventilation, plasma for inflammatory biomarker analyses was obtained by direct cardiac puncture at the end of the experiment.

RESULTS

Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were driven by FiO₂ 0.4 and 1.0 (P=0.02, P<0.01, respectively), tissue plasminogen activator inhibitor type-1 (tPAI-1) was increased by high PEEP (9 cmH₂O, P<0.05) and hypocapnia (P<0.05), and TNF-α was significantly lower in hypercapnia (P<0.01). Tissue inhibitor of metalloproteinase-1 (TIMP-1), cytokine-induced neutrophil chemoattractant 1 (CINC-1), connective tissue growth factor (CTGF), and monocyte chemoattractant protein-1 (MCP-1) remained unaffected.

CONCLUSION

Alterations of PEEP, FiO₂, and respiratory frequency induced a significant systemic inflammatory response in plasma of infant rats. These findings underscore the importance of lung-protective ventilation strategies. However, future studies are needed to clarify whether ventilation induced systemic inflammation in animal models is pathophysiologically relevant to human infants.

Association between inflammatory biomarkers and acute respiratory distress syndrome or acute lung injury risk : A systematic review and meta-analysis

Background

The relationship between acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) and levels of certain inflammatory factors remains controversial. The purpose of this meta-analysis was to summarize the available studies evaluating the association between levels of inflammatory factors and ARDS/ALI incidence.

Methods

We searched the PubMed, EmBase, and Cochrane databases for studies published up to July 2017. For each inflammatory factor, a random effects model was employed to pool results from different studies.

Results

We identified 63 studies that included 6243 patients in our meta-analysis. Overall, the results indicated that the levels of angiopoietin (ANG)-2 (standard mean difference, SMD: 1.34; P < 0.001), interleukin (IL)-1β (SMD: 0.92; P = 0.012), IL‑6 (SMD: 0.66; P = 0.005), and tumor necrosis factor (TNF)-α (SMD: 0.98; P = 0.001) were significantly higher in patients with ARDS/ALI than in unaffected individuals. No significant differences were observed between patients with ARDS/ALI and unaffected individuals in terms of the levels of IL‑8 (SMD: 0.61; P = 0.159), IL-10 (SMD: 1.10; P = 0.231), and plasminogen activator inhibitor (PAI)-1 (SMD: 0.70; P = 0.060).

Conclusions

ARDS/ALI is associated with a significantly elevated levels of ANG‑2, IL-1β, IL‑6, and TNF‑α, but not with IL‑8, IL-10, and PAI‑1 levels.

Supplementary Information

The online version of this article (10.1007/s00508-021-01971-3) contains supplementary material, which is available to authorized users.

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.

HEPBURN - investigating the efficacy and safety of nebulized heparin versus placebo in burn patients with inhalation trauma: study protocol for a multi-center randomized controlled trial

BACKGROUND

Pulmonary coagulopathy is a hallmark of lung injury following inhalation trauma. Locally applied heparin attenuates lung injury in animal models of smoke inhalation. Whether local treatment with heparin benefits patients with inhalation trauma is uncertain. The present trial aims at comparing a strategy using frequent nebulizations of heparin with standard care in intubated and ventilated burn patients with bronchoscopically confirmed inhalation trauma.

METHODS

The Randomized Controlled Trial Investigating the Efficacy and Safety of Nebulized HEParin versus Placebo in BURN Patients with Inhalation Trauma (HEPBURN) is an international multi-center, double-blind, placebo-controlled, two-arm study. One hundred and sixteen intubated and ventilated burn patients with confirmed inhalation trauma are randomized to nebulizations of heparin (the nebulized heparin strategy) or nebulizations of normal saline (the control strategy) every four hours for 14 days or until extubation, whichever comes first. The primary endpoint is the number of ventilator-free days, defined as days alive and breathing without assistance during the first 28 days, if the period of unassisted breathing lasts for at least 24 consecutive hours.

DISCUSSION

As far as the authors know, HEPBURN is the first randomized, placebo-controlled trial, powered to investigate whether local treatment with heparin shortens duration of ventilation of intubated and ventilated burn patients with inhalation trauma.

TRIAL REGISTRATION

NCT01773083 (http://www.clinicaltrials.gov), registered on 16 January 2013.Recruiting. Randomisation commenced on 1 January 2014.

Contribution of damage-associated molecular patterns to transfusion-related acute lung injury in cardiac surgery

BACKGROUND

The incidence of transfusion-related acute lung injury (TRALI) in cardiac surgery patients is high and this condition contributes to an adverse outcome. Damage-associated molecular pattern (DAMP) molecules, HMGB1 and S100A12, are thought to mediate inflammatory changes in acute respiratory distress syndrome. We aimed to determine whether DAMP are involved in the pathogenesis of TRALI in cardiac surgery patients.

MATERIALS AND METHODS

This was a secondary analysis of a prospective observational trial in cardiac surgery patients admitted to the Intensive Care Unit of a university hospital in the Netherlands. Fourteen TRALI cases were randomly matched with 32 transfused and non-transfused controls. Pulmonary levels of HMGB1, S100A12 and inflammatory cytokines (interleukins-1β, -6, and -8 and tumour necrosis factor-α) were determined when TRALI evolved. In addition, systemic and pulmonary levels of soluble receptor for advanced glycation end products (sRAGE) were determined.

RESULTS

HMGB1 expression and levels of sRAGE in TRALI patients did not differ from those in controls. There was a trend towards higher S100A12 levels in TRALI patients compared to the controls. Furthermore, S100A12 levels were associated with increased levels of markers of pulmonary inflammation, prolonged cardiopulmonary bypass, hypoxemia and duration of mechanical ventilation.

CONCLUSION

No evidence was found that HMGB1 and sRAGE contribute to the development of TRALI. S100A12 is associated with duration of cardiopulmonary bypass, pulmonary inflammation, hypoxia and prolonged mechanical ventilation and may contribute to acute lung injury in cardiac surgery patients.

Effects of Natural versus Synthetic Surfactant with SP-B and SP-C Analogs in a Porcine Model of Meconium Aspiration Syndrome

BACKGROUND

Meconium displaces surfactant from the alveolar surface and inhibits its function. The development of active synthetic surfactants is complicated, especially to synthesize the hydrophobic surfactant proteins SP-B and SP-C. A synthetic surfactant, CHF5633 containing SP-B and SP-C analogs, has been designed to act similarly to the natural surfactant poractant alfa.

OBJECTIVE

To test the resistance to meconium inactivation of CHF5633 compared to poractant alfa. Secondary outcome measurements were respiratory and inflammatory parameters.

METHODS

Twenty-six newborn pigs, bodyweight 1.4-2.0 kg were randomized to receive either poractant alfa or CHF5633. After anesthesia, surgery and final stabilization, meconium was instilled endotracheally followed by surfactant. Bronchial lavage fluid was obtained before intervention and every second hour. Respiratory parameters were registered and blood samples drawn before intervention and every hour.

RESULTS

Surfactant was inactivated in both groups 6 h after meconium instillation, but CHF5633 was more resistant than poractant alfa in terms of lipid peroxidation. Respiratory parameters were similar in both groups. Inflammatory and hemostatic parameters differed between groups, suggesting that the surfactants may play different roles in the meconium-induced inflammatory process. Due to the differential effects and complex pattern observed, the data do not indicate that one of the surfactants was superior with respect to inflammatory and hemostatic responses.

CONCLUSION

This study indicates that CHF5633 is as efficient as poractant alfa in experimental meconium aspiration syndrome.