Organ crosstalk during acute lung injury, acute respiratory distress syndrome, and mechanical ventilation

Organ crosstalk and dysfunction in sepsis

Sepsis is a dysregulated immune response to an infection that leads to organ dysfunction. Sepsis-associated organ dysfunction involves multiple inflammatory mechanisms and complex metabolic reprogramming of cellular function. These mechanisms cooperate through multiple organs and systems according to a complex set of long-distance communications mediated by cellular pathways, solutes, and neurohormonal actions. In sepsis, the concept of organ crosstalk involves the dysregulation of one system, which triggers compensatory mechanisms in other systems that can induce further damage. Despite the abundance of studies published on ​​organ crosstalk in the last decade, there is a need to formulate a more comprehensive framework involving all organs to create a more detailed picture of sepsis. In this paper, we review the literature published on organ crosstalk in the last 10 years and explore how these relationships affect the progression of organ failure in patients with septic shock. We explored these relationships in terms of the heart-kidney-lung, gut-microbiome-liver-brain, and adipose tissue-muscle-bone crosstalk in sepsis patients. A deep connection exists among these organs based on crosstalk. We also review how multiple therapeutic interventions administered in intensive care units, such as mechanical ventilation, antibiotics, anesthesia, nutrition, and proton pump inhibitors, affect these systems and must be carefully considered when managing septic patients. The progression to multiple organ dysfunction syndrome in sepsis patients is still one of the most frequent causes of death in critically ill patients. A better understanding and monitoring of the mechanics of organ crosstalk will enable the anticipation of organ damage and the development of individualized therapeutic strategies.

Extracerebral multiple organ dysfunction and interactions with brain injury after cardiac arrest

Cardiac arrest and successful resuscitation cause whole-body ischemia and reperfusion, leading to brain injury and extracerebral multiple organ dysfunction. Brain injury is the leading cause of death and long-term disability in resuscitated survivors, and was conceptualized and treated as an isolated injury, which has neglected the brain-visceral organ crosstalk. Extracerebral organ dysfunction is common and is significantly associated with mortality and poor neurological prognosis after resuscitation. However, detailed description of the characteristics of post-resuscitation multiple organ dysfunction is lacking, and the bidirectional interactions between brain and visceral organs need to be elucidated to explore new treatment for neuroprotection. This review aims to describe current concepts of post-cardiac arrest brain injury and specific characteristics of post-resuscitation dysfunction in cardiovascular, respiratory, renal, hepatic, adrenal, gastrointestinal, and neurohumoral systems. Additionally, we discuss the crosstalk between brain and extracerebral organs, especially focusing on how visceral organ dysfunction and other factors affect brain injury progression. We think that clarifying these interactions is of profound significance on how we treat patients for neural/systemic protection to improve outcome.

Down-regulating lncRNA KCNQ1OT1 relieves type II alveolar epithelial cell apoptosis during one-lung ventilation via modulating miR-129-5p/HMGB1 axis induced pulmonary endothelial glycocalyx

OBJECTIVE

Endothelial glycocalyx (EG) maintains vascular homeostasis and is destroyed after one-lung ventilation (OLV)-induced lung injury. Long noncoding RNAs (lncRNAs) are critically involved in various lung injuries. This study aimed to investigate the role and regulatory mechanism of KCNQ1 overlapping transcript 1 (KCNQ1OT1) in OLV-induced lung injury and LPS-induced type II alveolar epithelial cell (AECII) apoptosis.

METHODS

The rat OLV model was established, and the effects of KCNQ1OT1 on OLV-induced ALI in vivo were explored. Bax and Caspase-3 expression in rat lung tissues was measured by immunochemistry (IHC). AECIIs were isolated from rat lungs and treated with LPS or normal saline (control) for in vitro analysis. The expression of KCNQ1OT1, miR-129-5p, and HMGB1 was measured by quantitative real-time PCR (qRT-PCR) or Western blot (WB). Cell proliferation and apoptosis were examined by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT) and flow cytometry. The downstream targets of KCNQ1OT1 were predicted by bioinformatics, and the binding relationship between KCNQ1OT1 and miR-129-3p was verified by dual-luciferase reporter assays. The potential target of miR-129-5p was further explored on the Targetscan website and revealed to target HMGB1. Enzyme-linked immunosorbent assay (ELISA) or WB was adopted to determine the levels of IL-1β, TNF-α, MDA, SOD, heparanase (HPA), matrix metalloproteinase 9 (MMP9), heparan sulfate (HS) and syndecan-1 (SDC-1).

RESULTS

KCNQ1OT1 and HMGB1 were up-regulated during OLV-induced lung injury, and their expression was positively correlated. KCNQ1OT1 knockdown reduced OLV-induced pulmonary edema and lung epithelial cell apoptosis, increased vascular permeability, reduced IL-1β, TNF-α, MDA, and SOD levels and glycocalyx markers by targeting miR-129-5p or upregulating HMGB1. Overexpressing KCNQ1OT1 promoted cell apoptosis, reduced cell proliferation, aggravated inflammation and oxidative stress, and up-regulated HMGB1, HPA and MMP9 in LPS-treated AECIIs, while the HMGB1 silencing showed the opposite effects. MiR-129-5p mimics partially eliminated the KCNQ1OT1-induced effects, while recombinant HMGB1 restored the effects of miR-129-5p overexpression on AECIIs. Additionally, KCNQ1OT1 was demonstrated to promote the activation of the p38 MAPK/Akt/ERK signaling pathways in AECIIs via HMGB1.

CONCLUSION

KCNQ1OT1 knockdown alleviated AECII apoptosis and EG damage during OLV by targeting miR-129-5p/HMGB1 to inactivate the p38 MAPK/Akt/ERK signaling. The findings of our study might deepen our understanding of the molecular basis in OLV-induced lung injury and provide clues for the targeted disease management.

Alveolar cytokines and interferon autoantibodies in COVID-19 ARDS

Background

Type I interferon (IFN-I) and IFN autoantibodies play a crucial role in controlling SARS-CoV-2 infection. The levels of these mediators have only rarely been studied in the alveolar compartment in patients with COVID-19 acute respiratory distress syndrome (CARDS) but have not been compared across different ARDS etiologies, and the potential effect of dexamethasone (DXM) on these mediators is not known.

Methods

We assessed the integrity of the alveolo-capillary membrane, interleukins, type I, II, and III IFNs, and IFN autoantibodies by studying the epithelial lining fluid (ELF) volumes, alveolar concentration of protein, and ELF-corrected concentrations of cytokines in two patient subgroups and controls.

Results

A total of 16 patients with CARDS (four without and 12 with DXM treatment), eight with non-CARDS, and 15 healthy controls were included. The highest ELF volumes and protein levels were observed in CARDS. Systemic and ELF-corrected alveolar concentrations of interleukin (IL)-6 appeared to be particularly low in patients with CARDS receiving DXM, whereas alveolar levels of IL-8 were high regardless of DXM treatment. Alveolar levels of IFNs were similar between CARDS and non-CARDS patients, and IFNα and IFNω autoantibody levels were higher in patients with CARDS and non-CARDS than in healthy controls.

Conclusions

Patients with CARDS exhibited greater alveolo-capillary barrier disruption with compartmentalization of IL-8, regardless of DXM treatment, whereas systemic and alveolar levels of IL-6 were lower in the DXM-treated subgroup. IFN-I autoantibodies were higher in the BALF of CARDS patients, independent of DXM, whereas IFN autoantibodies in plasma were similar to those in controls.

A prospective observational study to correlate lung ultrasound with clinical severity and prognosis score in patients with primary pulmonary pathology on invasive ventilatory support

Background

Lung ultrasound (LUS) is a known imaging modality employed for monitoring patients in an intensive care unit. This study evaluates, LUS in assessing disease severity and prognosis, by correlating its score with the three commonly used clinical severity scoring systems (CSSS), namely, sequential organ failure assessment (SOFA) score, acute physiology and chronic health evaluation (APACHE) II score, and simplified acute physiology score (SAPS) II.

Methods

This single-center prospective observational study included 54 adult patients of primary lung disease-induced acute respiratory distress syndrome (ARDS), on invasive ventilation. The primary objective was to correlate LUS score with SOFA score. Secondary objectives were to correlate LUS score with APACHE II and SAPS II scores. LUS score was also correlated with the estimated mortality derived from the above-mentioned scores. A subgroup analysis on COVID-19-positive cases was also carried out. All scores were calculated on the initiation of mechanical ventilation, daily for 7 days or mortality, whichever was earlier.

Results

A significant positive correlation (P < 0.001) was found between LUS and all three severity scores, as well as their corresponding estimated mortality percentages, for all days of the study period, in both non-COVID-19 ARDS patients and in COVID-19 patients. The merit of all four scores in differentiating between the survivor and mortality group for the duration of study also showed significant (P < 0.05) to very significant (P < 0.001) results.

Conclusion

Point-of-care LUS in conjunction with CSSS is a reliable tool for assessing the severity and progression of primary lung disease.

Effects of airway pressure release ventilation on multi-organ injuries in severe acute respiratory distress syndrome pig models

BACKGROUND

Extra-pulmonary multi-organ failure in patients with severe acute respiratory distress syndrome (ARDS) is a major cause of high mortality. Our purpose is to assess whether airway pressure release ventilation (APRV) causes more multi-organ damage than low tidal volume ventilation (LTV).

METHODS

Twenty one pigs were randomized into control group (n = 3), ARDS group (n = 3), LTV group (n = 8) and APRV group (n = 7). Severe ARDS model was induced by repeated bronchial saline lavages. Pigs were ventilated and monitored continuously for 48 h. Respiratory data, hemodynamic data, serum inflammatory cytokines were collected throughout the study. Histological injury and apoptosis were assessed by two pathologists.

RESULTS

After severe ARDS modeling, pigs in ARDS, LTV and APRV groups experienced significant hypoxemia and reduced lung static compliance (C_stat). Oxygenation recovered progressively after 16 h mechanical ventilation (MV) in LTV and APRV group. The results of the repeated measures ANOVA showed no statistical difference in the PaO₂/FiO₂ ratio between the APRV and LTV groups (p = 0.54). The C_stat showed a considerable improvement in APRV group with statistical significance (p < 0.01), which was significantly higher than in the LTV group since 16 h (p = 0.04). Histological injury scores showed a significantly lower injury score in the middle and lower lobes of the right lung in the APRV group compared to LTV (p_middle = 0.04, p_lower = 0.01), and no significant increase in injury scores for extra-pulmonary organs, including kidney (p = 0.10), small intestine (p = 1.0), liver (p = 0.14, p = 0.13) and heart (p = 0.20). There were no significant differences in serum inflammatory cytokines between the two groups.

CONCLUSION

In conclusion, in the experimental pig models of severe ARDS induced by repetitive saline lavage, APRV improved lung compliance with reduced lung injury of middle and lower lobes, and did not demonstrate more extra-pulmonary organ injuries as compared with LTV.

Association between proteinuria trajectories and outcomes in critically ill patients with sepsis or shock

Background

Proteinuria results from kidney damage and can be a predictor of illness severity and mortality in the intensive care unit (ICU). However, the optimal timing of proteinuria measurements and the reference values remain undetermined. Our objective was to identify the patterns of proteinuria change associated with mortality in ICU patients with sepsis or shock.

Methods

This monocentric retrospective cohort study performed from April 2010 to April 2018 involved all ICU patients with sepsis or shock and at least two measurements of proteinuria from a 24h-urine collection during the first 10 days of ICU stay, the first of which was made within 48h after ICU admission. We identified proteinuria trajectories by a semi-parametric mixture model and analysed the association between the trajectories and the mortality at day 28 by Cox proportional-hazards model.

Results

A total of 3,344 measurements of proteinuria from 659 patients were analysed. Four proteinuria trajectories were identified. Trajectories 1, 2, 3 and 4 comprised 127, 421, 60 and 51 patients, and were characterized by a first proteinuria of 1.14 [0.66–1.55], 0.52 [0.26–0.91], 2.92 [2.38–3.84] and 2.58 [1.75–3.32] g/24h (p<0.001) and a mortality of 24.4%, 38%, 20% and 43% (p = 0.002), respectively. Trajectories 3 and 4 had a high first proteinuria (>2g/24h). Only, the proteinuria of trajectory 4 increased within 3 days following the first measurement and was associated with increased mortality at day 28 (hazard ratio: 2.36 95%CI [1.07–5.19], p = 0.03), regardless of acute renal failure. The factors associated with trajectory 4 were cancer (relative risk: 8.91 95%CI [2.09–38.02], p = 0.003) and use of inotropic drugs (relative risk: 0.17 95%CI [0.04–0.69], p = 0.01).

Conclusion

This exploratory study of ICU patients with sepsis or shock identified four proteinuria trajectories with distinct patterns of proteinuria change over time and mortality rates. These results provide novel insights into renal pathophysiology and may be helpful to investigate subphenotypes of kidney injury among ICU patients in future studies.

Reduction of NETosis by targeting CXCR1/2 reduces thrombosis, lung injury, and mortality in experimental human and murine sepsis

BACKGROUND

Neutrophil extracellular traps (NETs) facilitate bacterial clearance but also promote thrombosis and organ injury in sepsis. We quantified ex vivo NET induction in septic humans and murine models of sepsis to identify signalling pathways that may be modulated to improve outcome in human sepsis.

METHODS

NET formation in human donor neutrophils was quantified after incubation with plasma obtained from patients with sepsis or systemic inflammation (double-blinded assessment of extracellular DNA using immunofluorescence microscopy). NET formation (% neutrophils forming NETs) was correlated with plasma cytokine levels (MultiPlex assay). Experimental sepsis (caecal ligation and puncture or intraperitoneal injection of Escherichia coli) was assessed in C57/BL6 male mice. The effect of pharmacological inhibition of CXCR1/2 signalling (reparixin) on NET formation, organ injury (hepatic, renal, and cardiac biomarkers), and survival in septic mice was examined.

RESULTS

NET formation was higher after incubation with plasma from septic patients (median NETs=25% [10.5-46.5%]), compared with plasma obtained from patients with systemic inflammation (14% [4.0-23.3%]; P=0.02). Similar results were observed after incubation of plasma from mice with neutrophils from septic non-septic mice. Circulating CXCR1/2 ligands correlated with NETosis in patients (interleukin-8; r=0.643) and mice (macrophage inflammatory protein-2; r=0.902). In experimental sepsis, NETs were primarily observed in the lungs, correlating with fibrin deposition (r=0.702) and lung injury (r=0.692). Inhibition of CXCR1/2 using reparixin in septic mice reduced NET formation, multi-organ injury, and mortality, without impairing bacterial clearance.

CONCLUSION

CXCR1/2 signalling-induced NET formation is a therapeutic target in sepsis, which may be guided by ex vivo NET assays.

Apiaceous vegetables protect against acrolein-induced pulmonary injuries through modulating hepatic detoxification and inflammation in C57BL/6 male mice

Acrolein (Acr) is a reactive aldehyde in the environment. Acr causes oxidative stress and a cascade of catalytic events and has, thereby, been associated with increased risk of pulmonary diseases. Whether apiaceous vegetables (API) consumption can prevent Acr-induced pulmonary toxicity has not yet been explored hence, we investigated the effects of API on Acr-induced pulmonary damages in C57BL/6J mice. The mice were assigned into either negative control [NEG group; American Institute of Nutrition (AIN)-93G diet only], positive control (POS group; AIN-93G+Acr) or API intervention group (API group; AIN-93G+21% API+Acr). After 1 week of dietary intervention, the POS and API mice were exposed to Acr (10 µmol/kg body weight/day) for 5 days. During the exposure period, assigned diets remained the same. Prominent indicators lung of toxicity of POS mice were found, including mucus accumulation, macrophage infiltration, and hemorrhage, all of which were ameliorated by the API. Serum and lung inflammation markers, such as a tumor necrosis factor alpha were also increased by Acr while reduced by API. In the liver, API upregulated expression of glutathione S-transferases, which enhanced the metabolism of Acr into water-soluble 3-hydroxypropyl mercapturic acid for excretion. This is consistent with observed reductions in serum Acr-protein adducts. Taken together, our results suggest that API may provide protection against Acr-induced pulmonary damages and inflammation via enhancement of the hepatic detoxification of Acr.

Aggressive alveolar recruitment in ARDS: More shadows than lights

Alveolar recruitment in acute respiratory distress syndrome (ARDS) is defined as the penetration of gas into previously unventilated areas or poorly ventilated areas. Alveolar recruitment during recruitment maneuvering (RM) depends on the duration of the maneuver, the recruitable lung tissue, and the balance between the recruitment of collapsed areas and over-insufflation of the ventilated areas. Alveolar recruitment is estimated using computed tomography of the lung and, at the patient bedside, through assessment of the recruited volume using pressure-volume curves and assessing lung morphology with pulmonary ultrasound and/or impedance tomography. The scientific evidence on RM in patients with ARDS remains subject to controversy. Randomized studies on ARDS have shown no benefit or have even reflected an increase in mortality. The routine use of RM is therefore not recommended.

Ferroptosis and Necroptosis in the Kidney

In the last decade, the role of apoptosis in the pathophysiology of acute kidney injury (AKI) and AKI to chronic kidney disease (CKD) progression has been revisited as our understanding of ferroptosis and necroptosis has emerged. A growing body of evidence, reviewed here, ascribes a central pathophysiological role for ferroptosis and necroptosis to AKI, nephron loss, and acute tubular necrosis. We will introduce concepts to the non-cell-autonomous manner of kidney tubular injury during ferroptosis, a phenomenon that we refer to as a "wave of death." We hypothesize that necroptosis might initiate cell death propagation through ferroptosis. The remaining necrotic debris requires effective removal processes to prevent a secondary inflammatory response, referred to as necroinflammation. Open questions include the differences in the immunogenicity of ferroptosis and necroptosis, and the specificity of necrostatins and ferrostatins to therapeutically target these processes to prevent AKI-to-CKD progression and end-stage renal disease.

Crosstalk Between Lung and Extrapulmonary Organs in Infection and Inflammation

Acute and chronic lung inflammation is a risk factor for various diseases involving lungs and extrapulmonary organs. Intercellular and interorgan networks, including crosstalk between lung and brain, intestine, heart, liver, and kidney, coordinate host immunity against infection, protect tissue, and maintain homeostasis. However, this interaction may be counterproductive and cause acute or chronic comorbidities due to dysregulated inflammation in the lung. In this chapter, we review the relationship of the lung with other key organs during normal cell processes and disease development. We focus on how pneumonia may lead to a systemic pathophysiological response to acute lung injury and chronic lung disease through organ interactions, which can facilitate the development of undesirable and even deleterious extrapulmonary sequelae.

Extracorporeal Membrane Oxygenation for Severe Respiratory Failure During Respiratory Epidemics and Pandemics: A Narrative Review

Introduction: Epidemics and pandemics from zoonotic respiratory viruses, such as the 2019 novel coronavirus, can lead to significant global intensive care burden as patients progress to acute respiratory distress syndrome (ARDS). A subset of these patients develops refractory hypoxaemia despite maximal conventional mechanical ventilation and require extracorporeal membrane oxygenation (ECMO). This review focuses on considerations for ventilatory strategies, infection control and patient selection related to ECMO for ARDS in a pandemic. We also summarise the experiences with ECMO in previous respiratory pandemics. Materials and Methods: A review of pertinent studies was conducted via a search using MEDLINE, EMBASE and Google Scholar. References of articles were also examined to identify other relevant publications. Results: Since the H1N1 Influenza pandemic in 2009, the use of ECMO for ARDS continues to grow despite limitations in evidence for survival benefit. There is emerging evidence to suggest that lung protective ventilation for ARDS can be further optimised while receiving ECMO so as to minimise ventilator-induced lung injury and subsequent contributions to multi-organ failure. Efforts to improve outcomes should also encompass appropriate infection control measures to reduce co-infections and prevent nosocomial transmission of novel respiratory viruses. Patient selection for ECMO in a pandemic can be challenging. We discuss important ethical considerations and predictive scoring systems that may assist clinical decision-making to optimise resource allocation. Conclusion: The role of ECMO in managing ARDS during respiratory pandemics continues to grow. This is supported by efforts to redefine optimal ventilatory strategies, reinforce infection control measures and enhance patient selection. Ann Acad Med Singapore 2020;49:199–214 Key words: Acute Respiratory Distress Syndrome, Coronavirus disease 2019, ECMO, Infection control, Mechanical ventilation

The relationship between obstructive sleep apnea syndrome and obesity: A new perspective on the pathogenesis in terms of organ crosstalk

INTRODUCTION

Obstructive sleep apnea syndrome (OSAS) is a common disorder that has a major impact on public health. The connection between OSAS and obesity is very complex and likely represents an interaction between biological and lifestyle factors. Oxidative stress, inflammation and metabolic dysregulation are both actors involved in the pathogenesis of OSAS and obesity. Also, the current evidence suggests that gut microbiota plays a significant role in the emergence and progression of some metabolic disorders. When the relationship between OSAS and obesity is evaluated extensively, it is understood that they show mutual causality with each other, and that metabolic challenges such as impaired microbiota affect this bidirectional organ interaction, and by ensuing organ injury.

OBJECTIVES

The aim of this study is to investigate the association between OSAS and obesity, and the effect of "organ crosstalk" on the pathogenesis of the relationship and to contribute to the diagnosis and treatment options in the light of current data.

DATA SOURCE

We performed an electronic database search including PubMed, EMBASE and Web of Science. We used the following search terms: OSAS, obesity, inflammation, metabolic dysregulation and gut microbiota.

CONCLUSION

Obesity and OSAS adversely affect many organs and systems. Besides the factors affecting the diagnosis of the OSAS-obesity relationship, mutual organ interactions among the respiratory system, adipose tissue and intestines should not be ignored for prevention and treatment of OSAS and obesity. Comprehensive clinical trials addressing the efficacy and efficiency of current or potential treatments on therapeutic applications in the OSAS-obesity relationship are needed.

Intracranial pressure responsiveness to positive end-expiratory pressure in different respiratory mechanics: a preliminary experimental study in pigs

Background

Respiratory mechanics affects the effect of positive end-expiratory pressure (PEEP) on intracranial pressure (ICP). Respiratory mechanics of the lung and the chest wall was not differentiated in previous studies. In the present study, we investigated the influence of the following possible determinants of ICP responsiveness to PEEP: chest wall elastance (E_CW), lung elastance (E_L), and baseline ICP.

Methods

Eight healthy Bama miniature pigs were studied. The increase of E_L was induced by instillation of hydrochloride, and the increase of E_CW was induced by strapping the animals’ chest wall and abdomen. A balloon-tipped catheter was placed intracranially for inducing intracranial hypertension. Six experimental conditions were investigated in sequence: 1) Normal; 2) Stiff Chest Wall; 3) Lung Injury; 4) Lung Injury + Stiff Chest Wall; 5) Lung Injury + Stiff Chest Wall + Intracranial Hypertension and 6) Lung Injury + Intracranial Hypertension. PEEP was gradually increased in a 5 cm H₂O interval from 5 to 25 cm H₂O in each condition. Blood pressure, central venous pressure, ICP, airway pressure and esophageal pressure were measured.

Results

Hydrochloride instillation significantly increased E_L in conditions with lung injury. E_CW significantly increased in the conditions with chest wall and abdomen strapping (all p <  0.05). ICP significantly increased with increments of PEEP in all non-intracranial hypertension conditions (p <  0.001). The greatest cumulative increase in ICP was observed in the Stiff Chest Wall condition (6 [5.3, 6.8] mm Hg), while the lowest cumulative increase in ICP was observed in the Lung Injury condition (2 [1.3, 3.8] mm Hg). ICP significantly decreased when PEEP was increased in the intracranial hypertension conditions (p <  0.001). There was no significant difference in cumulative ICP change between the two intracranial hypertension conditions (p = 0.924).

Conclusions

Different respiratory mechanics models can be established via hydrochloride induced lung injury and chest wall and abdominal strapping. The effect of PEEP on ICP is determined by respiratory mechanics in pigs with normal ICP. However, the responsiveness of ICP to PEEP is independent of respiratory mechanics when there is intracranial hypertension.

The clinical relevance of necroinflammation-highlighting the importance of acute kidney injury and the adrenal glands

Necroinflammation is defined as the inflammatory response to necrotic cell death. Different necrotic cell death pathways exhibit different immune reponses, despite a comparable level of intracellular content release (referred to as damage associated molecular patterns or DAMPs). In addition to DAMP release, which is inevitably associated with necrotic cell death, the active production of pro/anti-inflammatory cytokines characterizes certain necrotic pathways. Necroptosis, ferroptosis and pyroptosis, therefore, are immunogenic to a different extent. In this review, we discuss the clinical relevance of necroinflammation highlighting potential human serum markers. We focus on the role of the adrenal glands and the lungs as central organs affected by systemic and/or local DAMP release and underline their role in intensive care medicine. In addition, data from models of acute kidney injury (AKI) and kidney transplantation have significantly shaped the field of necroinflammation and may be helpful for the understanding of the potential role of dialysis and plasma exchange to treat ongoing necroinflammation upon intensive care unit (ICU) conditions. In conclusion, we are only beginning to understand the importance of necroinflammation in diseases and transplantation, including xenotransplantation. However, given the existing efforts to develop inhibitors of necrotic cell death (ferrostatins, necrostatins, etc), we consider it likely that interference with necroinflammation reaches clinical routine in the near future.

Prolonged Mechanical Ventilation Assistance Interacts Synergistically with Carbapenem for Clostridium difficile Infection in Critically Ill Patients

Objectives: Interactions between mechanical ventilation (MV) and carbapenem interventions were investigated for the risk of Clostridium difficile infection (CDI) in critically ill patients undergoing concurrent carbapenem therapy. Methods: Taiwan’s National Intensive Care Unit Database (NICUD) was used in this analytical, observational, and retrospective study. We analyzed 267,871 intubated patients in subgroups based on the duration of MV support: 7–14 days (n = 97,525), 15–21 days (n = 52,068), 22–28 days (n = 35,264), and 29–60 days (n = 70,021). The primary outcome was CDI. Results: Age (>75 years old), prolonged MV assistance (>21 days), carbapenem therapy (>15 days), and high comorbidity scores were identified as independent risk factors for developing CDI. CDI risk increased with longer MV support. The highest rate of CDI was in the MV 29–60 days subgroup (adjusted hazard ratio (AHR) = 2.85; 95% confidence interval (CI) = 1.46–5.58; p < 0.02). Moreover, higher CDI rates correlated with the interaction between MV and carbapenem interventions; these CDI risks were increased in the MV 15–21 days (AHR = 2.58; 95% CI = 1.12–5.91) and MV 29–60 days (AHR = 4.63; 95% CI = 1.14–10.03) subgroups than in the non-MV and non-carbapenem subgroups. Conclusions: Both MV support and carbapenem interventions significantly increase the risk that critically ill patients will develop CDI. Moreover, prolonged MV support and carbapenem therapy synergistically induce CDI. These findings provide new insights into the role of MV support in the development of CDI.

Mechanisms involved in brain dysfunction in mechanically ventilated critically ill patients: implications and therapeutics

Critical illness may lead to significant long-term neurological morbidity and patients frequently develop neuropsychological disturbances including acute delirium or memory impairment after intensive care unit (ICU) discharge. Mechanical ventilation (MV) is a risk factor to the development of adverse neurocognitive outcomes. Patients undergoing MV for long periods present neurologic impairment with memory and cognitive alteration. Delirium is considered an acute form of brain dysfunction and its prevalence rises in mechanically ventilated patients. Delirium duration is an independent predictor of mortality, ventilation time, ICU length of stay and short- and long-term cognitive impairment in the ICU survivors. Although, neurocognitive sequelae tend to improve after hospital discharge, residual deficits persist even 6 years after ICU stay. ICU-related neurocognitive impairments occurred in many cognitive domains and are particularly pronounced with regard to memory, executive functions, attentional functions, and processing speed. These sequelae have an important impact on patients' lives and ICU survivors often require institutionalization and hospitalization. Experimental studies have served to explore the possible mechanisms or pathways involved in this lung to brain interaction. This communication can be mediated via a complex web of signaling events involving neural, inflammatory, immunologic and neuroendocrine pathways. MV can affect respiratory networks and the application of protective ventilation strategies is mandatory in order to prevent adverse effects. Therefore, strategies focused to minimize lung stretch may improve outcomes, avoiding failure of distal organ, including the brain. Long-term neurocognitive impairments experienced by critically ill survivors may be mitigated by early interventions, combining cognitive and physical therapies. Inpatient rehabilitation interventions in ICU promise to improve outcomes in critically ill patients. The cross-talk between lung and brain, involving specific pathways during critical illness deserves further efforts to evaluate, prevent and improve cognitive alterations after ICU admission, and highlights the crucial importance of tailoring MV to prevent adverse outcomes.

Erythropoietin mediates brain-vascular-kidney crosstalk and may be a treatment target for pulmonary and resistant essential hypertension

Organ crosstalk pathways represent the next frontier for target-mining in molecular medicine for existing syndromes. Pulmonary hypertension and resistant essential hypertension are syndromes that have been proven elusive in etiology, and frequently refractory to first-line management. Underlying crosstalk mechanisms, not yet considered in these treatments, may hinder outcomes or unlock novel treatments. This review focuses systematically on erythropoietin, a synthesizable molecule, as a mediator of brain-kidney crosstalk. Insights gained from this review will be applied to cardiovascular diseases in a clinician-directed fashion.

The Effect of Mechanical Ventilation on TASK-1 Expression in the Brain in a Rat Model

Background and Objective

TWIK-related acid-sensitive potassium channel 1 (TASK-1) is closely related to respiratory central control and neuronal injury. We investigated the effect of MV on TASK-1's functions and explored the mechanism using a rat model.

Methods

Male Sprague-Dawley rats were randomized to three groups: (1) high tidal volume (HVt): MV for four hours with Vt at 10 mL/kg; (2) low Vt (LVt): MV for four hours with Vt at 5 mL/kg; (3) basal (BAS): anesthetized and unventilated animals. We measured lung histology and plasma and brain levels of proteins (IL-6, TNF-α, and S-100B) and determined TASK-1 levels in rat brainstems as a marker of respiratory centre activity.

Results

The LISs (lung injury scores) were significantly higher in the HVt group. Brain inflammatory cytokines levels were different to those in serum. TASK-1 levels were significantly lower in the MV groups (P = 0.002) and the HVt group tended to have a lower level of TASK-1 than the LVt group.

Conclusion

MV causes not only lung injury, but also brain injury. MV affects the regulation of the respiratory centre, perhaps causing damage to it. Inflammation is probably not the main mechanism of ventilator-related brain injury.

Glycogen synthase kinase‑3β inhibitor reduces LPS‑induced acute lung injury in mice

The aim of the present study was to examine the role of Wnt signaling in lipopolysaccharide (LPS)‑induced acute respiratory distress syndrome (ARDS). ARDS was induced by LPS and compared in mice treated with either glycogen synthase kinase‑3β inhibitor (GSKI) or PBS. The protein expression levels of interleukin (IL)‑6, IL‑8, tumor necrosis factor (TNF)‑α, IL‑17, IL‑18 and IL‑1β in the bronchoalveolar lavage fluid (BALF) were examined using murine cytokine‑specific enzyme‑linked immunosorbent assays. The accumulation of neutrophils and macrophages in the BALF were detected using flow cytometry. The extent of pathological lesions was evaluated using an immunohistochemical assay. The differentiation of mesenchymal stem cells (MSCs) into type II alveolar (ATII) epithelial cells was analyzed using immunofluorescence staining. Treatment with GSKI led to maintained body weights and survival in mice with LPS‑induced ARDS. Treatment with GSKI effectively reduced the levels of total protein, albumin, IgM and keratinocyte growth factor in the BALF. Smith scores showed that GSKI significantly alleviated LPS‑induced lung injury. GSKI also functioned to reduce inflammatory cell accumulation and pro‑inflammatory cytokine secretion. Finally, it was found that GSKI promoted the differentiation of MSCs into ATII epithelial cells in vivo. Taken together, the GSKI‑treated mice exhibited reduced acute lung injury through inhibited intra‑fluid inflammatory cell infiltration and decreased expression of pro‑inflammatory cytokines, and GSKI increased the differentiation of MSCs into ATII epithelial cells.

Feasibility and safety of virtual-reality-based early neurocognitive stimulation in critically ill patients

Background

Growing evidence suggests that critical illness often results in significant long-term neurocognitive impairments in one-third of survivors. Although these neurocognitive impairments are long-lasting and devastating for survivors, rehabilitation rarely occurs during or after critical illness. Our aim is to describe an early neurocognitive stimulation intervention based on virtual reality for patients who are critically ill and to present the results of a proof-of-concept study testing the feasibility, safety, and suitability of this intervention.

Methods

Twenty critically ill adult patients undergoing or having undergone mechanical ventilation for ≥24 h received daily 20-min neurocognitive stimulation sessions when awake and alert during their ICU stay. The difficulty of the exercises included in the sessions progressively increased over successive sessions. Physiological data were recorded before, during, and after each session. Safety was assessed through heart rate, peripheral oxygen saturation, and respiratory rate. Heart rate variability analysis, an indirect measure of autonomic activity sensitive to cognitive demands, was used to assess the efficacy of the exercises in stimulating attention and working memory.

Results

Patients successfully completed the sessions on most days. No sessions were stopped early for safety concerns, and no adverse events occurred. Heart rate variability analysis showed that the exercises stimulated attention and working memory. Critically ill patients considered the sessions enjoyable and relaxing without being overly fatiguing.

Conclusions

The results in this proof-of-concept study suggest that a virtual-reality-based neurocognitive intervention is feasible, safe, and tolerable, stimulating cognitive functions and satisfying critically ill patients. Future studies will evaluate the impact of interventions on neurocognitive outcomes.

Trial registration Clinical trials.gov identifier: NCT02078206

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0303-4) contains supplementary material, which is available to authorized users.

Cyclic PaO2 oscillations assessed in the renal microcirculation: correlation with tidal volume in a porcine model of lung lavage

Background

Oscillations of the arterial partial pressure of oxygen induced by varying shunt fractions occur during cyclic alveolar recruitment within the injured lung. Recently, these were proposed as a pathomechanism that may be relevant for remote organ injury following acute respiratory distress syndrome. This study examines the transmission of oxygen oscillations to the renal tissue and their tidal volume dependency.

Methods

Lung injury was induced by repetitive bronchoalveolar lavage in eight anaesthetized pigs. Cyclic alveolar recruitment was provoked by high tidal volume ventilation. Oscillations of the arterial partial pressure of oxygen were measured in real-time in the macrocirculation by multi-frequency phase fluorimetry and in the renal microcirculation by combined white-light spectrometry and laser-Doppler flowmetry during tidal volume down-titration.

Results

Significant respiratory-dependent oxygen oscillations were detected in the macrocirculation and transmitted to the renal microcirculation in a substantial extent. The amplitudes of these oscillations significantly correlate to the applied tidal volume and are minimized during down-titration.

Conclusions

In a porcine model oscillations of the arterial partial pressure of oxygen are induced by cyclic alveolar recruitment and transmitted to the renal microcirculation in a tidal volume-dependent fashion. They might play a role in organ crosstalk and remote organ damage following lung injury.

Neuropulmonology

Neuropulmonology refers to the complex interconnection between the central nervous system and the respiratory system. Neurologic injury includes traumatic brain injury, hemorrhage, stroke, and seizures, and in each there are far-reaching effects that can result in pulmonary dysfunction. Systemic changes can induce impairment of pulmonary function due to changes in the core structure and function of the lung. The conditions and disorders that often occur in these patients include aspiration pneumonia, neurogenic pulmonary edema, and acute respiratory distress syndrome, but also several abnormal respiratory patterns and sleep-disordered breathing. Lung infections, pulmonary edema - neurogenic or cardiogenic - and pulmonary embolus all are a serious barrier to recovery and can have significant effects on outcomes such as hospital course, prognosis, and mortality. This review presents the spectrum of pulmonary abnormalities seen in neurocritical care.

Effects of increased positive end-expiratory pressure on intracranial pressure in acute respiratory distress syndrome: a protocol of a prospective physiological study

INTRODUCTION

There are concerns that the use of positive end-expiratory pressure (PEEP) in patients with brain injury may potentially elevate intracranial pressure (ICP). However, the transmission of PEEP into the thoracic cavity depends on the properties of the lungs and the chest wall. When chest wall elastance is high, PEEP can significantly increase pleural pressure. In the present study, we investigate the different effects of PEEP on the pleural pressure and ICP in different respiratory mechanics.

METHODS AND ANALYSIS

This study is a prospective, single-centre, physiological study in patients with severe brain injury. Patients with acute respiratory distress syndrome with ventricular drainage will be enrolled. An oesophageal balloon catheter will be inserted to measure oesophageal pressure. Patients will be sedated and paralysed; airway pressure and oesophageal pressure will be measured during end-inspiratory occlusion and end-expiratory occlusion. Elastance of the chest wall, the lungs and the respiratory system will be calculated at PEEP levels of 5, 10 and 15 cm H₂O. We will classify each patient based on the maximal ΔICP/ΔPEEP being above or below the median for the study population. 2 groups will thus be compared.

ETHICS AND DISSEMINATION

The study protocol and consent forms were approved by the Institutional Review Board of Fujian Provincial Hospital. Study findings will be disseminated through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

NCT02670733; pre-results.

Moderate Peep After Tracheal Lipopolysaccharide Instillation Prevents Inflammation and Modifies the Pattern of Brain Neuronal Activation

Background:

Ventilatory strategy and specifically positive end-expiratory pressure (PEEP) can modulate the inflammatory response and pulmonary-to-systemic translocation of lipopolysaccharide (LPS). Both inflammation and ventilatory pattern may modify brain activation, possibly worsening the patient's outcome and resulting in cognitive sequelae.

Methods:

We prospectively studied Sprague–Dawley rats randomly assigned to undergo 3 h mechanical ventilation with 7 mL/kg tidal ventilation and either 2 cmH₂O or 7 cmH₂O PEEP after intratracheal instillation of LPS or saline. Healthy nonventilated rats served as baseline. We analyzed lung mechanics, gas exchange, lung and plasma cytokine levels, lung apoptotic cells, and lung neutrophil infiltration. To evaluate brain neuronal activation, we counted c-Fos immunopositive cells in the retrosplenial cortex (RS), thalamus, supraoptic nucleus (SON), nucleus of the solitary tract (NTS), paraventricular nucleus (PVN), and central amygdala (CeA).

Results:

LPS increased lung neutrophilic infiltration, lung and systemic MCP-1 levels, and neuronal activation in the CeA and NTS. LPS-instilled rats receiving 7 cmH₂O PEEP had less lung and systemic inflammation and more c-Fos-immunopositive cells in the RS, SON, and thalamus than those receiving 2 cmH₂O PEEP. Applying 7 cmH₂O PEEP increased neuronal activation in the CeA and NTS in saline-instilled rats, but not in LPS-instilled rats.

Conclusions:

Moderate PEEP prevented lung and systemic inflammation secondary to intratracheal LPS instillation. PEEP also modified the neuronal activation pattern in the RS, SON, and thalamus. The relevance of these differential brain c-Fos expression patterns in neurocognitive outcomes should be explored.

Systemic PaO2 Oscillations Cause Mild Brain Injury in a Pig Model

OBJECTIVE

Systemic PaO2 oscillations occur during cyclic recruitment and derecruitment of atelectasis in acute respiratory failure and might harm brain tissue integrity.

DESIGN

Controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Adult anesthetized pigs.

INTERVENTIONS

Pigs were randomized to a control group (anesthesia and extracorporeal circulation for 20 hr with constant PaO2, n = 10) or an oscillation group (anesthesia and extracorporeal circulation for 20 hr with artificial PaO2 oscillations [3 cycles min⁻¹], n = 10). Five additional animals served as native group (n = 5).

MEASUREMENTS AND MAIN RESULTS

Outcome following exposure to artificial PaO2 oscillations compared with constant PaO2 levels was measured using 1) immunohistochemistry, 2) real-time polymerase chain reaction for inflammatory markers, 3) receptor autoradiography, and 4) transcriptome analysis in the hippocampus. Our study shows that PaO2 oscillations are transmitted to brain tissue as detected by novel ultrarapid oxygen sensing technology. PaO2 oscillations cause significant decrease in NISSL-stained neurons (p < 0.05) and induce inflammation (p < 0.05) in the hippocampus and a shift of the balance of hippocampal neurotransmitter receptor densities toward inhibition (p < 0.05). A pathway analysis suggests that cerebral immune and acute-phase response may play a role in mediating PaO2 oscillation-induced brain injury.

CONCLUSIONS

Artificial PaO2 oscillations cause mild brain injury mediated by inflammatory pathways. Although artificial PaO2 oscillations and endogenous PaO2 oscillations in lung-diseased patients have different origins, it is likely that they share the same noxious effect on the brain. Therefore, PaO2 oscillations might represent a newly detected pathway potentially contributing to the crosstalk between acute lung and remote brain injury.

Ventilation strategies for preventing oxidative stress-induced injury in preterm infants with respiratory disease: an update

Reactive oxygen and nitrogen species are produced by several inflammatory and structural cells of the airways. The lungs of preterm newborns are susceptible to oxidative injury induced by both reactive oxygen and nitrogen species. Increased oxidative stress and imbalance in antioxidant enzymes may play a role in the pathogenesis of inflammatory pulmonary diseases. Preterm infants are frequently exposed to high oxygen concentrations, infections or inflammation; they have reduced antioxidant defense and high free iron levels which enhance toxic radical generation. Multiple ventilation strategies have been studied to reduce injury and improve outcomes in preterm infants. Using lung protective strategies, there is the need to reach a compromise between satisfaction of gas exchange and potential toxicities related to over-distension, derecruitment of lung units and high oxygen concentrations. In this review, the authors summarize scientific evidence concerning oxidative stress as it relates to resuscitation in the delivery room and to the strategies of ventilation.

Brain injury requires lung protection

The paper entitled "The high-mobility group protein B1-Receptor for advanced glycation endproducts (HMGB1-RAGE) axis mediates traumatic brain injury (TBI)-induced pulmonary dysfunction in lung transplantation" published recently in Science Translational Medicine links lung failure after transplantation with alterations in the axis HMGB1-RAGE after TBI, opening a new field for exploring indicators for the early detection of patients at risk of developing acute lung injury (ALI). The lung is one of the organs most vulnerable to the inflammatory cascade triggered by TBI. HMGB1 is an alarm in that can be released from activated immune cells in response to tissue injury. Increased systemic HMGB1 concentration correlates with poor lung function before and after lung transplant, confirming its role in acute ALI after TBI. HMGB1 exerts its influence by interacting with several receptors, including the RAGE receptor. RAGE also plays an important role in the onset of innate immune inflammatory responses, and systemic levels of RAGE are strongly associated with ALI and clinical outcomes in ventilator-induced lung injury. RAGE ligation to HMGB1 triggers the amplification of the inflammatory cascade involving nuclear factor-κB (NF-κB) activation. Identifying early biomarkers that mediate pulmonary dysfunction will improve outcomes not only in lung transplantation, but also in other scenarios. These novel findings show that upregulation of the HMGB1-RAGE axis plays an important role in brain-lung crosstalk.

[Ventilation as a trigger for organ dysfunction and sepsis]

Both in the intensive care setting and during surgery, mechanical ventilation plays an important role in the treatment of critically ill patients with lung injury, but also in lung healthy patients. Mechanical ventilation is noncurative and is accompanied by various severe side effects. It is hypothesized that multiorgan failure can be induced by mechanical ventilation. Furthermore, there is evidence to suggest cross-talk between lungs and other organs. In particular, the activation of specific cells and cell programs in peripheral organs is an important step on the way to multiorgan failure. In addition to bidirectional connection between the lung and brain, nonprotective ventilation leads to cell apoptosis in the kidney and intestine and leads to an increase of biomarkers for organ dysfunction. It is believed that both inflammation mediators and pro-apoptotic factors are responsible for organ dysfunction.

Prolonged mechanical ventilation-induced neuroinflammation affects postoperative memory dysfunction in surgical mice

INTRODUCTION

Patients undergoing surgery frequently develop neuropsychological disturbances, including cognitive decline or memory impairment, and routine clinical procedures such as mechanical ventilation (MV) may affect acute-phase brain outcome. We aimed to investigate the effect of the prolonged MV on postoperative memory dysfunction in surgical mice.

METHODS

Male C57BL/6 mice were randomly divided into the following three groups: (1) The control group (group C) comprised anesthetized, unventilated animals; (2) the surgery group (subgroups S1h, S3h and S6h) was unventilated animals that underwent surgery under general anesthesia; and (3) the MV group (subgroups MV1h, MV3h and MV6h) was made up of animals under MV for 1 hour, 3 hours or 6 hours after surgery. Separate cohorts of animals were tested for memory function with fear conditioning tests or were killed at 6 hours, 1 day or 3 days postsurgery or post-MV to examine levels systemic and hippocampal interleukin (IL)-1β, IL-6 and tumor necrosis factor α (TNFα), and assessed synaptic structure and microglial activation. Nuclear factor κB (NF-κB) p65, cytochrome c, cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase (PARP) activation were analyzed by Western blotting.

RESULTS

The MV6h group showed increased CD11b-immunopositive cells, synapse degeneration, cytochrome c release, cleaved caspase-3 and cleaved PARP-1 activation after surgery, as well as a decrease in freezing time after surgery. At 6 hours and 1 day post-MV, MV6h increased NF-κB activation and levels of systemic and hippocampal IL-1β, IL-6 and TNFα after surgery.

CONCLUSIONS

Prolonged MV after surgery further aggravates cognitive decline that may stem from upregulation of hippocampal IL-1β, IL-6 and TNFα, partially via activation of gliocytes in the surgical mouse hippocampus.

Venovenous extracorporeal life support for posttraumatic respiratory distress syndrome in adults: the risk of major hemorrhages

Background

The aim of this retrospective study is to investigate the therapeutic benefits and the bleeding risks of venovenous extracorporeal life support (VV-ECLS) when used for adult posttraumatic respiratory distress syndrome (posttraumatic ARDS).

Materials and methods

Twenty adult trauma patients (median age: 38 years, median injury severity score: 35) treated with VV-ECLS in a level I trauma center between January 2004 and June 2013 were enrolled in this study. The indication of VV-ECLS for posttraumatic ARDS was refractory hypoxemia (P_aO₂/F_iO₂ ratio ≤ 70 mmHg) under advanced mechanical ventilation. To minimize potential complications, a protocol-guided VV-ECLS was adopted.

Results

Sixteen patients were weaned off VV-ECLS, and of these patients fourteen survived. Medians of the trauma-to-ECLS time, the pre-ECLS mechanical ventilation, and the ECLS duration in all patients were 64, 45, and 144 hours respectively. The median P_aO₂/F_iO₂ ratio was improved significantly soon after VV-ECLS, from 56 to 106 mmHg (p < 0.001). However, seven major hemorrhages occurred during VV-ECLS, of which three were lethal. The multivariate analysis revealed that the occurrence of major hemorrhages during VV-ECLS was independently related to the trauma-to-ECLS time < 24 hours (OR: 20; p = 0.02; 95% CI: 2–239; c-index: 0.81).

Conclusions

Despite an effective respiratory support, VV-ECLS should be cautiously administered to patients who develop advanced ARDS soon after major trauma.

Electronic supplementary material

The online version of this article (doi:10.1186/s13049-014-0056-0) contains supplementary material, which is available to authorized users.

Endotoxin-induced lung alveolar cell injury causes brain cell damage

Sepsis is the most common cause of acute respiratory distress syndrome, a severe lung inflammatory disorder with an elevated morbidity and mortality. Sepsis and acute respiratory distress syndrome involve the release of inflammatory mediators to the systemic circulation, propagating the cellular and molecular response and affecting distal organs, including the brain. Since it has been reported that sepsis and acute respiratory distress syndrome contribute to brain dysfunction, we investigated the brain-lung crosstalk using a combined experimental in vitro airway epithelial and brain cell injury model. Conditioned medium collected from an in vitro lipopolysaccharide-induced airway epithelial cell injury model using human A549 alveolar cells was subsequently added at increasing concentrations (no conditioned, 2%, 5%, 10%, 15%, 25%, and 50%) to a rat mixed brain cell culture containing both astrocytes and neurons. Samples from culture media and cells from mixed brain cultures were collected before treatment, and at 6 and 24 h for analysis. Conditioned medium at 15% significantly increased apoptosis in brain cell cultures 24 h after treatment, whereas 25% and 50% significantly increased both necrosis and apoptosis. Levels of brain damage markers S100 calcium binding protein B and neuron-specific enolase, interleukin-6, macrophage inflammatory protein-2, as well as matrix metalloproteinase-9 increased significantly after treating brain cells with ≥2% conditioned medium. Our findings demonstrated that human epithelial pulmonary cells stimulated with bacterial lipopolysaccharide release inflammatory mediators that are able to induce a translational clinically relevant and harmful response in brain cells. These results support a brain-lung crosstalk during sepsis and sepsis-induced acute respiratory distress syndrome.

Transcompartmental inflammatory responses in humans: IV versus endobronchial administration of endotoxin*

OBJECTIVES

Transcompartmental signaling during early inflammation may lead to propagation of disease to other organs. The time course and the mechanisms involved are still poorly understood. We aimed at comparing acute transcompartmental inflammatory responses in humans following lipopolysaccharide-induced pulmonary and systemic inflammation.

DESIGN

Randomized, double-blind, placebo-controlled, crossover study.

SETTING ICU SUBJECTS

Healthy male volunteers.

INTERVENTIONS

Fifteen volunteers (mean age, 23; SD, 2 yr) received Escherichia coli endotoxin (lipopolysaccharide, 4 ng/kg) IV or endobronchially on two different study days. Groups were evaluated by bronchoalveolar lavage at baseline (0 hr) and 2, 4, 6, 8, or 24 hours postchallenge. Cardiorespiratory variables were continuously recorded throughout the study day, and plasma and bronchoalveolar lavage fluid markers of inflammation were measured.

MEASUREMENTS AND MAIN RESULTS

IV endotoxin elicited a systemic inflammatory response with a time-dependent increase and peak in tumor necrosis factor-α, interleukin-6, and leukocyte counts (all p < 0.001). Furthermore, a delayed (6-8 hr) increase in bronchoalveolar lavage fluid interleukin-6 concentration (p < 0.001) and alveolar leukocyte count (p = 0.03) and a minor increase in bronchoalveolar lavage fluid tumor necrosis factor-α were observed (p = 0.06). Endobronchial endotoxin was followed by progressive alveolar neutrocytosis and increased bronchoalveolar lavage fluid tumor necrosis factor-α, interleukin-6, and albumin (all p < 0.001); a systemic inflammatory response was observed after 2-4 hours, with no change in plasma tumor necrosis factor-α.

CONCLUSIONS

Acute lung or systemic inflammation in humans is followed by a transcompartmental proinflammatory response, the degree and differential kinetics of which suggests that the propagation of inflammation may depend on the primary site of injury.

Respiratory support for premature neonates in the delivery room: effects on cardiovascular function and the development of brain injury

The transition to newborn life in preterm infants is complicated by immature cardiovascular and respiratory systems. Consequently, preterm infants often require respiratory support immediately after birth. Although aeration of the lung underpins the circulatory transition at birth, positive pressure ventilation can adversely affect cardiorespiratory function during this vulnerable period, reducing pulmonary blood flow and left ventricular output. Furthermore, pulmonary volutrauma is known to initiate pulmonary inflammatory responses, resulting in remote systemic involvement. This review focuses on the downstream consequences of positive pressure ventilation, in particular, interactions between cardiovascular output and the initiation of a systemic inflammatory cascade, on the immature brain. Recent studies have highlighted that positive pressure ventilation strategies are precursors of cerebral injury, probably mediated through cerebral blood flow instability. The presence of, or initiation of, an inflammatory cascade accentuates adverse cerebral blood flow, in addition to being a direct source of brain injury. Importantly, the degree of brain injury is dependent on the nature of the initial ventilation strategy used.

Pulmonary retention of primed neutrophils: a novel protective host response, which is impaired in the acute respiratory distress syndrome

Rationale

Acute respiratory distress syndrome (ARDS) affects over 200 000 people annually in the USA. Despite causing severe, and often refractory, hypoxaemia, the high mortality and long-term morbidity of ARDS results mainly from extra-pulmonary organ failure; however the mechanism for this organ crosstalk has not been determined.

Methods

Using autologous radiolabelled neutrophils we investigated the pulmonary transit of primed and unprimed neutrophils in humans. Flow cytometry of whole blood samples was used to assess transpulmonary neutrophil priming gradients in patients with ARDS, sepsis and perioperative controls.

Main results

Unprimed neutrophils passed through the lungs with a transit time of 14.2 s, only 2.3 s slower than erythrocytes, and with <5% first-pass retention. Over 97% of neutrophils primed ex vivo with granulocyte macrophage colony-stimulating factor were retained on first pass, with 48% still remaining in the lungs at 40 min. Neutrophils exposed to platelet-activating factor were initially retained but subsequently released such that only 14% remained in the lungs at 40 min. Significant transpulmonary gradients of neutrophil CD62L cell surface expression were observed in ARDS compared with perioperative controls and patients with sepsis.

Conclusions

We demonstrated minimal delay and retention of unprimed neutrophils transiting the healthy human pulmonary vasculature, but marked retention of primed neutrophils; these latter cells then ‘deprime’ and are re-released into the systemic circulation. Further, we show that this physiological depriming mechanism may fail in patients with ARDS, resulting in increased numbers of primed neutrophils within the systemic circulation. This identifies a potential mechanism for the remote organ damage observed in patients with ARDS.

Brain-heart crosstalk: the many faces of stress-related cardiomyopathy syndromes in anaesthesia and intensive care

Neurogenic stress cardiomyopathy (NSC) is a well-known syndrome complicating the early phase after an acute brain injury, potentially affecting outcomes. This article is a review of recent data on the putative role of localization and lateralization of brain lesions in NSC, cardiac innervation abnormalities, and new polymorphisms and other genetic causes of the sympathetic nervous system over-activity. Concerns regarding the management of stress-related cardiomyopathy syndromes during the perioperative period are also discussed. Future clinical research should explore whether specific factors explain different patient susceptibilities to the disease and should be directed towards early identification and stratification of patients at risk, so that such patients can be more carefully monitored and appropriately managed in critical care and during the perioperative period.

Prophylactic erythropoietin exacerbates ventilation-induced lung inflammation and injury in preterm lambs

Ventilation-induced lung injury (VILI) of preterm neonates probably contributes to the pathogenesis of bronchopulmonary dysplasia (BPD). Erythropoietin (EPO) has been suggested as a therapy for BPD. The aim of this study was to determine whether prophylactic administration of EPO reduces VILI in preterm newborn lambs. Lambs at 126 days of gestation (term is 147 days) were delivered and ventilated with a high tidal volume strategy for 15 min to cause lung injury, then received gentle ventilation until 2 h of age. Lambs were randomized to receive intravenous EPO (5000 IU kg(-1): Vent+EPO; n = 6) or phosphate-buffered saline (Vent; n = 7) soon after birth: unventilated controls (UVC; n = 8) did not receive ventilation or any treatment. Physiological parameters were recorded throughout the experimental procedure. Samples of lung were collected for histological and molecular assessment of inflammation and injury. Samples of liver were collected to assess the systemic acute phase response. Vent+EPO lambs received higher F IO 2, P aO 2 and oxygenation during the first 10 min than Vent lambs. There were no differences in physiological indices beyond this time. Total lung injury score, airway wall thickness, inflammation and haemorrhage were higher in Vent+EPO lambs than in Vent lambs. Lung inflammation and early markers of lung and systemic injury were elevated in ventilated lambs relative to unventilated lambs; EPO administration further increased lung inflammation and markers of lung and systemic injury. Prophylactic EPO exacerbates VILI, which may increase the incidence and severity of long-term respiratory disease. More studies are required before EPO can be used for lung protection in preterm infants.

Lung protective ventilation induces immunotolerance and nitric oxide metabolites in porcine experimental postoperative sepsis

Low tidal volume ventilation is beneficial in patients with severe pulmonary dysfunction and would, in theory, reduce postoperative complications if implemented during routine surgery. The study aimed to investigate whether low tidal volume ventilation and high positive end-expiratory pressure (PEEP) in a large animal model of postoperative sepsis would attenuate the systemic inflammatory response and organ dysfunction. Thirty healthy pigs were randomized to three groups: Group Prot-7h, i.e. protective ventilation for 7 h, was ventilated with a tidal volume of 6 mL x kg^-1 for 7 h; group Prot-5h, i.e. protective ventilation for 5 h, was ventilated with a tidal volume of 10 mL x kg^-1 for 2 h, after which the group was ventilated with a tidal volume of 6 mL x kg^-1; and a control group that was ventilated with a tidal volume of 10 mL x kg^-1 for 7 h. In groups Prot-7h and Prot-5h PEEP was 5 cmH₂O for 2 h and 10 cmH₂O for 5 h. In the control group PEEP was 5 cmH₂O for the entire experiment. After surgery for 2 h, postoperative sepsis was simulated with an endotoxin infusion for 5 h. Low tidal volume ventilation combined with higher PEEP led to lower levels of interleukin 6 and 10 in plasma, higher PaO₂/FiO2, better preserved functional residual capacity and lower plasma troponin I as compared with animals ventilated with a medium high tidal volume and lower PEEP. The beneficial effects of protective ventilation were seen despite greater reductions in cardiac index and oxygen delivery index. In the immediate postoperative phase low V_T ventilation with higher PEEP was associated with reduced ex vivo plasma capacity to produce TNF-α upon endotoxin stimulation and higher nitrite levels in urine. These findings might represent mechanistic explanations for the attenuation of systemic inflammation and inflammatory-induced organ dysfunction.

Interrelationship among common medical complications after acute stroke: pneumonia plays an important role

BACKGROUND AND PURPOSE

Medical complications are common among patients with stroke. However, little is known about the potential interrelationship among them. In the present study, we aimed to investigate the association between common in-hospital medical complications after acute ischemic stroke (AIS) and spontaneous intracerebral hemorrhage (ICH).

METHODS

We analyzed patients enrolled in the China National Stroke Registry from 2007 to 2008. The occurrence of 11 common stroke-associated medical complications during acute hospitalization was prospectively registered. Multivariable analysis using generalized estimation equation was performed to assess association between medical complications in AIS and ICH cohort, respectively.

RESULTS

A total of 14 702 patients with AIS and 5221 patients with ICH were enrolled. The median age was 65 years (interquartile range, 55-74 years), and 38.1% were female. The median length of hospital stay was 14 days (interquartile range, 10-20 days) for AIS and 18 days (interquartile range, 11-26 days) for ICH. Pneumonia was the most common medical complication after AIS (11.4%) and ICH (16.8%). In the AIS cohort, after adjusting for potential confounders, pneumonia was significantly associated with development of gastrointestinal bleeding (adjusted odds ratio [OR], 8.35; 95% confidence interval [CI], 6.27-11.1; P<0.001), decubitus ulcer (adjusted OR, 5.31; 95% CI, 3.39-8.31; P<0.001), deep vein thrombosis (adjusted OR, 4.27; 95% CI, 2.41-7.59; P<0.001), epileptic seizure (adjusted OR, 3.96; 95% CI, 2.67-5.88; P<0.001), urinary tract infection (adjusted OR, 3.34; 95% CI, 2.73-4.10; P<0.001), atrial fibrillation/flutter (adjusted OR, 3.17; 95% CI, 2.58-3.90; P<0.001), and recurrent stroke (adjusted OR, 2.65; 95% CI, 2.07-3.40; P<0.001). Similar significant association between pneumonia and development of several nonpneumonia medical complications was verified in ICH cohort as well.

CONCLUSIONS

Pneumonia is closely associated with the development of several nonpneumonia medical complications after AIS and ICH.

[Lung-brain interaction in the mechanically ventilated patient]

Patients with acute lung injury or acute respiratory distress syndrome (ARDS) admitted to the ICU present neuropsychological alterations, which in most cases extend beyond the acute phase and have an important adverse effect upon quality of life. The aim of this review is to deepen in the analysis of the complex interaction between lung and brain in critically ill patients subjected to mechanical ventilation. This update first describes the neuropsychological alterations occurring both during the acute phase of ICU stay and at discharge, followed by an analysis of lung-brain interactions during mechanical ventilation, and finally explores the etiology and mechanisms leading to the neurological disorders observed in these patients. The management of critical patients requires an integral approach focused on minimizing the deleterious effects over the short, middle or long term.

[Lung-brain interaction in the mechanically ventilated patient]

Patients with acute lung injury or acute respiratory distress syndrome (ARDS) admitted to the ICU present neuropsychological alterations, which in most cases extend beyond the acute phase and have an important adverse effect upon quality of life. The aim of this review is to deepen in the analysis of the complex interaction between lung and brain in critically ill patients subjected to mechanical ventilation. This update first describes the neuropsychological alterations occurring both during the acute phase of ICU stay and at discharge, followed by an analysis of lung-brain interactions during mechanical ventilation, and finally explores the etiology and mechanisms leading to the neurological disorders observed in these patients. The management of critical patients requires an integral approach focused on minimizing the deleterious effects over the short, middle or long term.