Brain-lung crosstalk: Implications for neurocritical care patients

Identifying the Influence of Lung-Related Injuries and Other Factors on Delirium in Traumatic Brain Injury Patients: A National Analysis

Traumatic brain injury (TBI) is a known risk factor for delirium, a condition associated with prolonged hospitalization and cognitive deterioration. Although the relationship between TBI and delirium is established, the influence of traumatic lung injuries on delirium development is less understood. Respiratory disorders can significantly influence the central nervous system, with sequelae such as hypoxia and hypercapnia causing neurologic dysfunction. Therefore, we hypothesized that TBI patients suffering lung-associated conditions, stemming either from traumatic lung injury (TLI) or subsequent pulmonary surgery will be associated with an increased risk of developing delirium.

METHODS

The 2021 Trauma Quality Improvement Program database was queried for patients with TBI, excluding those with pre-existing dementia. TBI patients developing delirium were compared to those without delirium. A multivariable logistic regression analysis was performed to determine pulmonary and neurogenic-associated risk factors for delirium.

RESULTS

Among 155,252 TBI patients, 3244 (2.1%) developed delirium. Delirium-afflicted patients showed elevated rates of TLI (25.0% vs 13.3%, p < .001), severe head trauma (51.4% vs 37.8%, p < .001), sepsis (3.1% vs 0.5%, p < .001) and more commonly underwent pulmonary operations (21.8% vs 6.6%, p < .001). The strongest associated risk factors for delirium included unplanned intubation (OR 2.79, CI 2.47-3.16, p < .001), pulmonary surgery (OR 1.47, CI 1.32-1.63, p < .001), COPD (OR 1.52, CI 1.34-1.72, p < .001), TLI (OR 1.25, CI 1.14-1.38, p < .001), and severe head injury (OR 1.12, CI 1.04-1.22, p = .003).

CONCLUSION

Delirium affects approximately 2% of the national TBI population. Our study reveals an influence of lung-related conditions for delirium onset. These results emphasize the intimate relationship of the brain and pulmonary system. Future prospective studies are needed to validate these findings as they may impact TBI management and outcomes.

Potentially modifiable ventilation factors associated with outcome in neurocritical care vs. non-neurocritical care patients: Rational and protocol for a patient-level analysis of PRoVENT, PRoVENT-iMiC and ENIO (PRIME)

INTRODUCTION

Ventilator settings and ventilation variables and parameters vary between neurocritical care and non-neurocritical care patients. We aim to compare ventilation management in neurocritical care patients versus non-neurocritical care patients under invasive mechanical ventilation support, and to determine which factors related to ventilatory management have an independent association with outcome in neurocritical patients.

METHODS AND ANALYSIS

We meta-analyze harmonized individual patient data from three observational studies ('PRactice of VENTilation in critically ill patients without ARDS' [PRoVENT], 'PRactice of VENTilation in critically ill patients in Middle-income Countries' [PRoVENT-iMiC] and 'Extubation strategies and in neuro-intensive care unit patients and associations with outcomes' [ENIO]), pooled into a database named 'PRIME'. The primary endpoint is all cause ICU mortality. Secondary endpoints are key ventilator settings and ventilation variables and parameters. To identify potentially modifiable and non-modifiable factors contributing to ICU mortality, a multivariable model will be built using demographic factors, comorbidities, illness severities, and respiratory and laboratorial variables. In analyses examining the impact of ventilatory variables on outcome, we will estimate the relative risk of ICU mortality for neurocritical and non-neurocritical care patients by dividing the study population based on key ventilator variables and parameters.

ETHICS AND DISSEMINATION

This meta-analysis will address a clinically significant research question by comparing neurocritical care with non-neurocritical care patients. As this is a meta-analysis, additional ethical committee approval is not required. Findings will be disseminated to the scientific community through abstracts and original articles in peer-reviewed journals. Furthermore, the PRIME database will be made accessible for further post-hoc analyses.

REGISTRATION

PROVENT, PROVENT-iMiC and ENIO, and the pooled database PRIME are registered at clinicaltrials.gov (NCT01868321 for PRoVENT, NCT03188770 for PRoVENT-iMiC, and NCT03400904 for ENIO, and for PRIME is pending).

Treatment of intractable paradoxical herniation by invasive mechanical ventilation with increased positive end-expiratory pressure: a case report

OBJECTIVE

Paradoxical herniation (PH) is a rare but potentially life-threatening complication after decompressive craniectomy. The core treatment strategy for PH focuses on increasing intracranial pressure. Here, we present the treatment course of intractable PH in a 59-year-old patient with a traumatic acute subdural hematoma.

METHODS

The patient underwent two operations to evacuate intracranial hematomas followed by decompressive craniectomy within 48 h. Intractable PH was induced by persistent cerebrospinal fluid leakage due to multiple lumbar punctures. The condition was managed with conventional interventions, such as a supine position, intravenous fluid infusion, and multiple intrathecal saline injections, which have been proven to be inefficient. Owing to his unconsciousness and concurrent severe pneumonia, the patient underwent invasive mechanical ventilation with increased positive end-expiratory pressure (PEEP) to optimize oxygen delivery. PEEP was set at 10 cmH2O with the intention of facilitating alveolar recruitment.

RESULTS

Increased PEEP unexpectedly played a role in elevating intracranial pressure and, as a result, led to the complete resolution of PH. The patient gradually recovered and resumed his daily activities.

CONCLUSIONS

Applying invasive mechanical ventilation with increased PEEP for treating intractable PH can yield a favorable outcome. It represents a novel approach to dealing with such a rare complication.

Pulmonary consequences of experimentally induced stroke: differences between global and focal cerebral ischemia

Introduction

Cerebral ischemia leads to multiple organ dysfunctions, with the lungs among the most severely affected. Although adverse pulmonary consequences contribute significantly to reduced life expectancy after stroke, the impact of global or focal cerebral ischemia on respiratory mechanical parameters remains poorly understood.

Methods

Rats were randomly assigned to undergo surgery to induce permanent global cerebral ischemia (2VO) or focal cerebral ischemia (MCAO), or to receive a sham operation (SHAM). Three days later, end-expiratory lung volume, airway and respiratory tissue mechanics were measured at positive end-expiratory pressure (PEEP) levels of 0, 3 and 6 cmH2O. Bronchial responsiveness to methacholine, lung cytokine levels, wet-to-dry ratio, blood gas parameters and cerebral stroke markers were also evaluated.

Results

Global and focal cerebral ischemia had no significant effect on end-expiratory lung volume, bronchial responsiveness, and arterial blood gas levels. No change in respiratory mechanics and inflammatory response was evident after 2VO. Conversely, MCAO decreased airway resistance at PEEP 0, deteriorated respiratory tissue damping and elastance at all PEEP levels, and elevated Hct and Hgb. MCAO also caused lung edema and augmented IL-1β and TNF-α in the lung tissue without affecting IL-6 and IL-8 levels.

Discussion

Our findings suggest that global cerebral ischemia has no major pulmonary consequences. However, deteriorations in the respiratory tissue mechanics develop after permanent focal ischemia due to pulmonary edema formation, hemoconcentration and cytokine production. This respiratory mechanical defect can compromise lung distension at all PEEP levels, which warrants consideration in optimizing mechanical ventilation.

The influence of sex on neuroimmune communication, pain, and physiology

With the National Institutes of Health's mandate to consider sex as a biological variable (SABV), there has been a significant increase of studies utilizing both sexes. Historically, we have known that biological sex and hormones influence immunological processes and now studies focusing on interactions between the immune, endocrine, and nervous systems are revealing sex differences that influence pain behavior and various molecular and biochemical processes. Neuroendocrine-immune interactions represent a key integrative discipline that will reveal critical processes in each field as it pertains to novel mechanisms in sex differences and necessary therapeutics. Here we appraise preclinical and clinical literature to discuss these interactions and key pathways that drive cell- and sex-specific differences in immunity, pain, and physiology.

Advancements in understanding the mechanisms of lung-kidney crosstalk

This narrative review delves into the intricate interplay between the lungs and the kidneys, with a focus on elucidating the pathogenesis of diseases influenced by immunological factors, acid-base regulation, and blood gas disturbances, as well as assessing the effects of various therapeutic modalities on these interactions. Key disorders, such as anti-glomerular basement membrane (anti-GBM) disease, the syndrome of inappropriate antidiuretic hormone secretion (SIADH), and Anti-neutrophil Cytoplasmic Antibodies (ANCA) associated vasculitis (AAV), are also examined to shed light on their underlying mechanisms. This review also explores the relationship between acute respiratory distress syndrome (ARDS) and acute kidney injury (AKI), emphasizing how inflammatory mediators can lead to systemic damage and impact multiple organs. In ARDS, fluid overload exacerbates pulmonary edema, while imbalances in blood volume, such as hypovolemia or hypervolemia, can precipitate renal dysfunction. The review highlights how mechanical ventilation strategies can compromise renal blood flow, trigger systemic inflammation, and induce hemodynamic and neurohormonal alterations, all contributing to lung and kidney damage. The impact of extracorporeal membrane oxygenation (ECMO) on lung-kidney interactions is evaluated, highlighting its role in severe respiratory failure and its renal implications. Emerging therapies, such as mesenchymal stem cells and extracellular vesicles, are discussed as promising avenues to mitigate organ damage and enhance outcomes in critically ill patients. Overall, this review offers a nuanced exploration of lung-kidney dynamics, bridging historical insights with contemporary perspectives. It underscores the clinical significance of these interactions in critically ill patients and advocates for integrated management approaches to optimize patient outcomes.

Focus on brain-lung crosstalk: Preventing or treating the pathological vicious circle between the brain and the lung

Recently, there has been increasing attention to bidirectional information exchange between the brain and lungs. Typical physiological data is communicated by channels like the circulation and sympathetic nervous system. However, communication between the brain and lungs can also occur in pathological conditions. Studies have shown that severe traumatic brain injury (TBI), cerebral hemorrhage, subarachnoid hemorrhage (SAH), and other brain diseases can lead to lung damage. Conversely, severe lung diseases such as acute respiratory distress syndrome (ARDS), pneumonia, and respiratory failure can exacerbate neuroinflammatory responses, aggravate brain damage, deteriorate neurological function, and result in poor prognosis. A brain or lung injury can have adverse effects on another organ through various pathways, including inflammation, immunity, oxidative stress, neurosecretory factors, microbiome and oxygen. Researchers have increasingly concentrated on possible links between the brain and lungs. However, there has been little attention given to how the interaction between the brain and lungs affects the development of brain or lung disorders, which can lead to clinical states that are susceptible to alterations and can directly affect treatment results. This review described the relationships between the brain and lung in both physiological and pathological conditions, detailing the various pathways of communication such as neurological, inflammatory, immunological, endocrine, and microbiological pathways. Meanwhile, this review provides a comprehensive summary of both pharmacological and non-pharmacological interventions for diseases related to the brain and lungs. It aims to support clinical endeavors in preventing and treating such ailments and serve as a reference for the development of relevant medications.

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.

Development and validation of a predictive model for pulmonary infection risk in patients with traumatic brain injury in the ICU: a retrospective cohort study based on MIMIC-IV

OBJECTIVE

To develop a nomogram for predicting occurrence of secondary pulmonary infection in patients with critically traumatic brain injury (TBI) during their stay in the intensive care unit, to further optimise personalised treatment for patients and support the development of effective, evidence-based prevention and intervention strategies.

DATA SOURCE

This study used patient data from the publicly available MIMIC-IV (Medical Information Mart for Intensive Care IV) database.

DESIGN

A population-based retrospective cohort study.

METHODS

In this retrospective cohort study, 1780 patients with TBI were included and randomly divided into a training set (n=1246) and a development set (n=534). The impact of pulmonary infection on survival was analysed using Kaplan-Meier curves. A univariate logistic regression model was built in training set to identify potential factors for pulmonary infection, and independent risk factors were determined in a multivariate logistic regression model to build nomogram model. Nomogram performance was assessed with receiver operating characteristic (ROC) curves, calibration curves and Hosmer-Lemeshow test, and predictive value was assessed by decision curve analysis (DCA).

RESULT

This study included a total of 1780 patients with TBI, of which 186 patients (approximately 10%) developed secondary lung infections, and 21 patients died during hospitalisation. Among the 1594 patients who did not develop lung infections, only 85 patients died (accounting for 5.3%). The survival curves indicated a significant survival disadvantage for patients with TBI with pulmonary infection at 7 and 14 days after intensive care unit admission (p<0.001). Both univariate and multivariate logistic regression analyses showed that factors such as race other than white or black, respiratory rate, temperature, mechanical ventilation, antibiotics and congestive heart failure were independent risk factors for pulmonary infection in patients with TBI (OR>1, p<0.05). Based on these factors, along with Glasgow Coma Scale and international normalised ratio variables, a training set model was constructed to predict the risk of pulmonary infection in patients with TBI, with an area under the ROC curve of 0.800 in the training set and 0.768 in the validation set. The calibration curve demonstrated the model's good calibration and consistency with actual observations, while DCA indicated the practical utility of the predictive model in clinical practice.

CONCLUSION

This study established a predictive model for pulmonary infections in patients with TBI, which may help clinical doctors identify high-risk patients early and prevent occurrence of pulmonary infections.

Acute Respiratory Failure in Severe Acute Brain Injury

Acute respiratory failure is commonly encountered in severe acute brain injury due to a multitude of factors related to the sequelae of the primary injury. The interaction between pulmonary and neurologic systems in this population is complex, often with competing priorities. Many treatment modalities for acute respiratory failure can result in deleterious effects on cerebral physiology, and secondary brain injury due to elevations in intracranial pressure or impaired cerebral perfusion. High-quality literature is lacking to guide clinical decision-making in this population, and deliberate considerations of individual patient factors must be considered to optimize each patient's care.

Pathophysiology of acute lung injury in patients with acute brain injury: the triple-hit hypothesis

It has been convincingly demonstrated in recent years that isolated acute brain injury (ABI) may cause severe dysfunction of peripheral extracranial organs and systems. Of all potential target organs and systems, the lung appears to be the most vulnerable to damage after ABI. The pathophysiology of the bidirectional brain-lung interactions is multifactorial and involves inflammatory cascades, immune suppression, and dysfunction of the autonomic system. Indeed, the systemic effects of inflammatory mediators in patients with ABI create a systemic inflammatory environment ("first hit") that makes extracranial organs vulnerable to secondary procedures that enhance inflammation, such as mechanical ventilation (MV), surgery, and infections ("second hit"). Moreover, accumulating evidence supports the knowledge that gut microbiota constitutes a critical superorganism and an organ on its own, potentially modifying various physiological functions of the host. Furthermore, experimental and clinical data suggest the existence of a communication network among the brain, gastrointestinal tract, and its microbiome, which appears to regulate immune responses, gastrointestinal function, brain function, behavior, and stress responses, also named the "gut-microbiome-brain axis." Additionally, recent research evidence has highlighted a crucial interplay between the intestinal microbiota and the lungs, referred to as the "gut-lung axis," in which alterations during critical illness could result in bacterial translocation, sustained inflammation, lung injury, and pulmonary fibrosis. In the present work, we aimed to further elucidate the pathophysiology of acute lung injury (ALI) in patients with ABI by attempting to develop the "double-hit" theory, proposing the "triple-hit" hypothesis, focused on the influence of the gut-lung axis on the lung. Particularly, we propose, in addition to sympathetic hyperactivity, blast theory, and double-hit theory, that dysbiosis and intestinal dysfunction in the context of ABI alter the gut-lung axis, resulting in the development or further aggravation of existing ALI, which constitutes the "third hit."

Effect of a physician-nurse integrated lung protection care model in neurocritical patients

Background

Lung injury resulting from diffuse pulmonary interstitial and other lung-related complications is a significant contributor to poor prognosis and mortality in patients with critical neurological diseases. To enhance patient outcomes, it is essential to investigate a lung protection model that involves the collaboration of doctors, nurses, and other medical professionals.

Methods

Patients receiving different care styles were divided into two groups: routine care (RC) and lung function protection care (LFPC). The LFPC group included airway and posture management, sedation and analgesia management, positive end-expiratory pressure titration in ventilation management, and fluid volume management, among others. Statistical analysis methods, such as chi-square, were used to compare the incidence of acute lung injury (ALI), neurogenic pulmonary edema (NPE), ventilator-associated pneumonia (VAP), acute respiratory distress syndrome (ARDS), and length of stay between the RC and LFPC groups.

Results

The RC group included 68 patients (33 males; 34-74 years of age). The LFPC group included 60 patients (29 males; 37-73 years of age). Compared with the RC group, the LFPC group had lower occurrence rates of ALI (20.0 % vs. 38.2 %, P = 0.024), NPE (8.3 % vs. 23.5 %, P = 0.021), VAP (8.3 % vs. 25.0 %, P = 0.013), and ARDS (1.7 % vs. 16.2 %, P = 0.015). The length of hospital stay was shorter in the LFPC group than in the RC group (11.3 ± 3.5 vs. 14.3 ± 4.4 days, P = 0.0001).

Conclusion

The physician-nurse integrated lung protection care model proved to be effective in improving outcomes, reducing complications, and shortening the hospital stay length for neurocritical patients.

Incidence and Outcomes of Acute Respiratory Distress Syndrome in Brain-Injured Patients Receiving Invasive Ventilation: A Secondary Analysis of the ENIO Study

Background: Acute respiratory distress syndrome (ARDS) is an important pulmonary complication in brain-injured patients receiving invasive mechanical ventilation (IMV). We aimed to evaluate the incidence and association between ARDS and clinical outcomes in patients with different forms of acute brain injury requiring IMV in the intensive care unit (ICU). Methods: This was a preplanned secondary analysis of a prospective, multicenter, international cohort study (NCT03400904). We included brain-injured patients receiving IMV for ≥ 24 h. ARDS was the main exposure of interest and was identified during index ICU admission using the Berlin definition. We examined the incidence and adjusted association of ARDS with ICU mortality, ICU length of stay, duration of IMV, and extubation failure. Outcomes were evaluated using mixed-effect logistic regression and cause-specific Cox proportional hazards models. Results: 1492 patients from 67 hospitals and 16 countries were included in the analysis, of whom 137 individuals developed ARDS (9.2% of overall cohort). Across countries, the median ARDS incidence was 5.1% (interquartile range [IQR] 0-10; range 0-27.3). ARDS was associated with increased ICU mortality (adjusted odds ratio (OR) 2.66; 95% confidence interval [CI], 1.29-5.48), longer ICU length of stay (adjusted hazard ratio [HR] 0.59; 95% CI, 0.48-0.73), and longer duration of IMV (adjusted HR 0.54; 95% CI, 0.44-0.67). The association between ARDS and extubation failure approached statistical significance (adjusted HR 1.48; 95% CI 0.99-2.21). Higher ARDS severity was associated with incrementally longer ICU length of stay and longer cumulative duration of IMV. Findings remained robust in a sensitivity analysis evaluating the magnitude of unmeasured confounding. Conclusions: In this cohort of acutely brain-injured patients, the incidence of ARDS was similar to that reported in other mixed cohorts of critically ill patients. Development of ARDS was associated with worse outcomes.

Respiratory challenges and ventilatory management in different types of acute brain-injured patients

Acute brain injury (ABI) covers various clinical entities that may require invasive mechanical ventilation (MV) in the intensive care unit (ICU). The goal of MV, which is to protect the lung and the brain from further injury, may be difficult to achieve in the most severe forms of lung or brain injury. This narrative review aims to address the respiratory issues and ventilator management, specific to ABI patients in the ICU.

Factors associated with acute respiratory distress syndrome in brain-injured patients: A systematic review and meta-analysis

PURPOSE

Acute respiratory distress syndrome (ARDS) is common in patients with acute brain injury admitted to the ICU. We aimed to identify factors associated with ARDS in this population.

METHODS

We searched MEDLINE, Embase, Cochrane Central, Scopus, and Web of Science from inception to January 14, 2022. Three reviewers independently screened articles and selected English-language studies reporting risk factors for ARDS in brain-injured adult patients. Data were extracted on ARDS incidence, adjusted and unadjusted risk factors, and clinical outcomes. Risk of bias was reported using the Quality in Prognostic Studies tool. Certainty of evidence was assessed using GRADE.

RESULTS

We selected 23 studies involving 6,961,284 patients with acute brain injury. The pooled cumulative incidence of ARDS after brain injury was 17.0% (95%CI 10.7-25.8). In adjusted analysis, factors associated with ARDS included sepsis (odds ratio (OR) 4.38, 95%CI 2.37-8.10; high certainty), history of hypertension (OR 3.11, 95%CI 2.31-4.19; high certainty), pneumonia (OR 2.69, 95%CI 2.35-3.10; high certainty), acute kidney injury (OR 1.44, 95%CI 1.30-1.59; moderate certainty), admission hypoxemia (OR 1.67, 95%CI 1.29-2.17; moderate certainty), male sex (OR 1.30, 95%CI 1.06-1.58; moderate certainty), and chronic obstructive pulmonary disease (OR 1.27, 95%CI 1.13-1.44; moderate certainty). Development of ARDS was independently associated with increased odds of in-hospital mortality (OR 3.12, 95% CI 1.39-7.00).

CONCLUSIONS

Multiple risk factors are associated with ARDS in brain-injured patients. These findings could be used to develop prognostic models for ARDS or as prognostic enrichment strategies for patient enrolment in future clinical trials.

Brain-lung crosstalk: how should we manage the breathing brain?

Recent studies have drawn increasing attention to brain-lung crosstalk in critically ill patients. However, further research is needed to investigate the pathophysiological interactions between the brain and lungs, establish neuroprotective ventilatory strategies for brain-injured patients, provide guidance on potentially conflicting treatment priorities in patients with concomitant brain and lung injury, and enhance prognostic models to inform extubation and tracheostomy decisions. To bring together such research, BMC Pulmonary Medicine welcomes submissions to its new Collection on 'Brain-lung crosstalk'.

Utilization of mechanical power and associations with clinical outcomes in brain injured patients: a secondary analysis of the extubation strategies in neuro-intensive care unit patients and associations with outcome (ENIO) trial

BACKGROUND

There is insufficient evidence to guide ventilatory targets in acute brain injury (ABI). Recent studies have shown associations between mechanical power (MP) and mortality in critical care populations. We aimed to describe MP in ventilated patients with ABI, and evaluate associations between MP and clinical outcomes.

METHODS

In this preplanned, secondary analysis of a prospective, multi-center, observational cohort study (ENIO, NCT03400904), we included adult patients with ABI (Glasgow Coma Scale ≤ 12 before intubation) who required mechanical ventilation (MV) ≥ 24 h. Using multivariable log binomial regressions, we separately assessed associations between MP on hospital day (HD)1, HD3, HD7 and clinical outcomes: hospital mortality, need for reintubation, tracheostomy placement, and development of acute respiratory distress syndrome (ARDS).

RESULTS

We included 1217 patients (mean age 51.2 years [SD 18.1], 66% male, mean body mass index [BMI] 26.3 [SD 5.18]) hospitalized at 62 intensive care units in 18 countries. Hospital mortality was 11% (n = 139), 44% (n = 536) were extubated by HD7 of which 20% (107/536) required reintubation, 28% (n = 340) underwent tracheostomy placement, and 9% (n = 114) developed ARDS. The median MP on HD1, HD3, and HD7 was 11.9 J/min [IQR 9.2-15.1], 13 J/min [IQR 10-17], and 14 J/min [IQR 11-20], respectively. MP was overall higher in patients with ARDS, especially those with higher ARDS severity. After controlling for same-day pressure of arterial oxygen/fraction of inspired oxygen (P/F ratio), BMI, and neurological severity, MP at HD1, HD3, and HD7 was independently associated with hospital mortality, reintubation and tracheostomy placement. The adjusted relative risk (aRR) was greater at higher MP, and strongest for: mortality on HD1 (compared to the HD1 median MP 11.9 J/min, aRR at 17 J/min was 1.22, 95% CI 1.14-1.30) and HD3 (1.38, 95% CI 1.23-1.53), reintubation on HD1 (1.64; 95% CI 1.57-1.72), and tracheostomy on HD7 (1.53; 95%CI 1.18-1.99). MP was associated with the development of moderate-severe ARDS on HD1 (2.07; 95% CI 1.56-2.78) and HD3 (1.76; 95% CI 1.41-2.22).

CONCLUSIONS

Exposure to high MP during the first week of MV is associated with poor clinical outcomes in ABI, independent of P/F ratio and neurological severity. Potential benefits of optimizing ventilator settings to limit MP warrant further investigation.

Cardiac dysfunction in patients affected by subarachnoid haemorrhage affects in-hospital mortality: A systematic review and metanalysis

BACKGROUND

Subarachnoid haemorrhage (SAH) is a life-threatening condition with associated brain damage. Moreover, SAH is associated with a massive release of catecholamines, which may promote cardiac injury and dysfunction, possibly leading to haemodynamic instability, which in turn may influence a patient's outcome.

OBJECTIVES

To study the prevalence of cardiac dysfunction (as assessed by echocardiography) in patients with SAH and its effect on clinical outcomes.

DESIGN

Systematic review of observational studies.

DATA SOURCES

We performed a systematic search over the last 20 years on MEDLINE and EMBASE databases.

ELIGIBILITY CRITERIA

Studies reporting echocardiography findings in adult patients with SAH admitted to intensive care. Primary outcomes were in-hospital mortality and poor neurological outcome according to the presence or absence of cardiac dysfunction.

RESULTS

We included a total of 23 studies (4 retrospective) enrolling 3511 patients. The cumulative frequency of cardiac dysfunction was 21% (725 patients), reported as regional wall motion abnormality in the vast majority of studies (63%). Due to the heterogeneity of clinical outcome data reporting, a quantitative analysis was carried out only for in-hospital mortality. Cardiac dysfunction was associated with a higher in-hospital mortality [odds ratio 2.69 (1.64 to 4.41); P < 0.001; I2 = 63%]. The GRADE of evidence assessment resulted in very low certainty of evidence.

CONCLUSION

About one in five patients with SAH develops cardiac dysfunction, which seems to be associated with higher in-hospital mortality. The consistency of cardiac and neurological data reporting is lacking, reducing the comparability of the studies in this field.

Lung Injury Risk in Traumatic Brain Injury Managed With Optimal Cerebral Perfusion Pressure Guided-Therapy

Introduction

Management of traumatic brain injury (TBI) has to counterbalance prevention of secondary brain injury without systemic complications, namely lung injury. The potential risk of developing acute respiratory distress syndrome (ARDS) leads to therapeutic decisions such as fluid balance restriction, high PEEP and other lung protective measures, that may conflict with neurologic outcome. In fact, low cerebral perfusion pressure (CPP) may induce secondary ischemic injury and mortality, but disproportionate high CPP may also increase morbidity and worse lung compliance and hypoxia with the risk of developing ARDS and fatal outcome. The evaluation of cerebral autoregulation at bedside and individualized (optimal CPP) CPPopt-guided therapy, may not only be a relevant measure to protect the brain, but also a safe measure to avoid systemic complications.

Aim of the study

We aimed to study the safety of CPPopt-guided-therapy and the risk of secondary lung injury association with bad outcome.

Methods and results

Single-center retrospective analysis of 92 severe TBI patients admitted to the Neurocritical Care Unit managed with CPPopt-guided-therapy by PRx (pressure reactivity index). During the first 10 days, we collected data from blood gas, ventilation and brain variables. Evolution along time was analyzed using linear mixed-effects regression models. 86% were male with mean age 53±21 years. 49% presented multiple trauma and 21% thoracic trauma. At hospital admission, median GCS was 7 and after 3-months GOS was 3. Monitoring data was CPP 86±7mmHg, CPP-CPPopt -2.8±10.2mmHg and PRx 0.03±0.19. The average PFratio (PaO2/FiO2) was 305±88 and driving pressure 15.9±3.5cmH2O. PFratio exhibited a significant quadratic dependence across time and PRx and driving pressure presented significant negative association with PFRatio. CPP and CPPopt did not present significant effect on PFratio (p=0.533; p=0.556). A significant positive association between outcome and the difference CPP-CPPopt was found.

Conclusion

Management of TBI using CPPopt-guided-therapy was associated with better outcome and seems to be safe regarding the development of secondary lung injury.

Ventilatory targets following brain injury

PURPOSE OF REVIEW

Recent studies have focused on identifying optimal targets and strategies of mechanical ventilation in patients with acute brain injury (ABI). The present review will summarize these findings and provide practical guidance to titrate ventilatory settings at the bedside, with a focus on managing potential brain-lung conflicts.

RECENT FINDINGS

Physiologic studies have elucidated the impact of low tidal volume ventilation and varying levels of positive end expiratory pressure on intracranial pressure and cerebral perfusion. Epidemiologic studies have reported the association of different thresholds of tidal volume, plateau pressure, driving pressure, mechanical power, and arterial oxygen and carbon dioxide concentrations with mortality and neurologic outcomes in patients with ABI. The data collectively make clear that injurious ventilation in this population is associated with worse outcomes; however, optimal ventilatory targets remain poorly defined.

SUMMARY

Although direct data to guide mechanical ventilation in brain-injured patients is accumulating, the current evidence base remains limited. Ventilatory considerations in this population should be extrapolated from high-quality evidence in patients without brain injury - keeping in mind relevant effects on intracranial pressure and cerebral perfusion in patients with ABI and individualizing the chosen strategy to manage brain-lung conflicts where necessary.

Targeting NRF2 to promote epithelial repair

The transcription factor NRF2 is well known as a master regulator of the cellular stress response. As such, activation of NRF2 has gained widespread attention for its potential to prevent tissue injury, but also as a possible therapeutic approach to promote repair processes. While NRF2 activation affects most or even all cell types, its effect on epithelial cells during repair processes has been particularly well studied. In response to tissue injury, these cells proliferate, migrate and/or spread to effectively repair the damage. In this review, we discuss how NRF2 governs repair of epithelial tissues, and we highlight the increasing number of NRF2 targets with diverse roles in regulating epithelial repair.

MILD TRAUMATIC BRAIN INJURY ATTENUATES PNEUMONIA-INDUCED LUNG INJURY BY MODULATIONS OF ALVEOLAR MACROPHAGE BACTERICIDAL ACTIVITY AND M1 POLARIZATION

ABSTRACT

Traumatic brain injury is one of the main causes of death and disability worldwide, and results in multisystem complications. However, the mechanism of mild traumatic brain injury (MTBI) on lung injury remains unclear. In this study, we used a murine model of MTBI and pneumonia ( Pseudomonas aeruginosa ;) to explore the relationship between these conditions and the underlying mechanism. Methods: Mice (n = 104) were divided into control, MTBI, pneumonia, and MTBI + pneumonia groups. MTBI was induced by the weight-drop method. Pneumonia was induced by intratracheal injection with P. aeruginosa Xen5 strain. Animals were killed 24 h after bacterial challenging. Histological, cellular, and molecular indices of brain and lung injury were assessed using various methods. Results: Mice in both the MTBI and pneumonia groups had more Fluoro-Jade C-positive neurons than did the controls ( P < 0.01), but mice in the MTBI + pneumonia group had fewer Fluoro-Jade C-positive cells than did the pneumonia group ( P < 0.01). The MTBI + pneumonia mice showed decreased bacterial load ( P < 0.05), reduced lung injury score and pulmonary permeability ( P < 0.01), less inflammatory cells, and lower levels of proinflammatory cytokines (TNF-α and IL-1β; P < 0.01) when compared with the pneumonia group. Molecular analysis indicated lower levels of phosphorylated nuclear factor-κB in the lung of MTBI + pneumonia mice compared with the pneumonia group ( P < 0.01). Furthermore, alveolar macrophages from MTBI mice exhibited enhanced bactericidal capacity compared with those from controls ( P < 0.01). Moreover, MTBI + pneumonia mice exhibited less CD86-positive M1 macrophages compared with the pneumonia group ( P < 0.01). Conclusions: MTBI attenuates pneumonia-induced acute lung injury through the modulation of alveolar macrophage bactericidal capacity and M1 polarization in bacterial pneumonia model.

Plants and their Bioactive Compounds as a Possible Treatment for Traumatic Brain Injury-Induced Multi-Organ Dysfunction Syndrome

BACKGROUND & OBJECTIVE

Traumatic brain injury is an outcome of the physical or mechanical impact of external forces on the brain. Thus, the silent epidemic has complex pathophysiology affecting the brain along with extracranial or systemic complications in more than one organ system, including the heart, lungs, liver, kidney, gastrointestinal and endocrine system. which is referred to as Multi-Organ Dysfunction Syndrome. It is driven by three interconnected mechanisms such as systemic hyperinflammation, paroxysmal sympathetic hyperactivity, and immunosuppression-induced sepsis. These multifaceted pathologies accelerate the risk of mortality in clinical settings by interfering with the functions of distant organs through hypertension, cardiac arrhythmias, acute lung injury, neurogenic pulmonary edema, reduced gastrointestinal motility, Cushing ulcers, acute liver failure, acute kidney injury, coagulopathy, endocrine dysfunction, and many other impairments. The pharmaceutical treatment approach for this is highly specific in its mode of action and linked to a variety of side effects, including hallucinations, seizures, anaphylaxis, teeth, bone staining, etc. Therefore, alternative natural medicine treatments are widely accepted due to their broad complementary or synergistic effects on the physiological system with minor side effects.

CONCLUSION

This review is a compilation of the possible mechanisms behind the occurrence of multiorgan dysfunction and reported medicinal plants with organoprotective activity that have not been yet explored against traumatic brain injury and thereby, highlighting the marked possibilities of their effectiveness in the management of multiorgan dysfunction. As a result, we attempted to respond to the hypothesis against the usage of medicinal plants to treat neurodegenerative diseases.

Brain-Lung Crosstalk: Management of Concomitant Severe Acute Brain Injury and Acute Respiratory Distress Syndrome

Purpose of Review

To summarize pathophysiology, key conflicts, and therapeutic approaches in managing concomitant severe acute brain injury (SABI) and acute respiratory distress syndrome (ARDS).

Recent Findings

ARDS is common in SABI and independently associated with worse outcomes in all SABI subtypes. Most landmark ARDS trials excluded patients with SABI, and evidence to guide decisions is limited in this population. Potential areas of conflict in the management of patients with both SABI and ARDS are (1) risk of intracranial pressure (ICP) elevation with high levels of positive end-expiratory pressure (PEEP), permissive hypercapnia due to lung protective ventilation (LPV), or prone ventilation; (2) balancing a conservative fluid management strategy with ensuring adequate cerebral perfusion, particularly in patients with symptomatic vasospasm or impaired cerebrovascular blood flow; and (3) uncertainty about the benefit and harm of corticosteroids in this population, with a mortality benefit in ARDS, increased mortality shown in TBI, and conflicting data in other SABI subtypes. Also, the widely adapted partial pressure of oxygen (PaO2) target of > 55 mmHg for ARDS may exacerbate secondary brain injury, and recent guidelines recommend higher goals of 80-120 mmHg in SABI. Distinct pathophysiology and trajectories among different SABI subtypes need to be considered.

Summary

The management of SABI with ARDS is highly complex, and conventional ARDS management strategies may result in increased ICP and decreased cerebral perfusion. A crucial aspect of concurrent management is to recognize the risk of secondary brain injury in the individual patient, monitor with vigilance, and adjust management during critical time windows. The care of these patients requires meticulous attention to oxygenation and ventilation, hemodynamics, temperature management, and the neurological exam. LPV and prone ventilation should be utilized, and supplemented with invasive ICP monitoring if there is concern for cerebral edema and increased ICP. PEEP titration should be deliberate, involving measures of hemodynamic, pulmonary, and brain physiology. Serial volume status assessments should be performed in SABI and ARDS, and fluid management should be individualized based on measures of brain perfusion, the neurological exam, and cardiopulmonary status. More research is needed to define risks and benefits in corticosteroids in this population.

Evaluation and Characterization of Post-Stroke Lung Damage in a Murine Model of Cerebral Ischemia

After stroke and other brain injuries, there is a high incidence of respiratory complications such as pneumonia or acute lung injury. The molecular mechanisms that drive the brain-lung interaction post-stroke have not yet been elucidated. We performed transient middle cerebral artery occlusion (MCAO) and sham surgery on C57BL/6J mice and collected bronchoalveolar lavage fluid (BALF), serum, brain, and lung homogenate samples 24 h after surgery. A 92 proteins-panel developed by Olink Proteomics® was used to analyze the content in BALF and lung homogenates. MCAO animals had higher protein concentration levels in BALF than sham-controls, but these levels did not correlate with the infarct volume. No alteration in alveolar-capillary barrier permeability was observed. A total of 12 and 14 proteins were differentially expressed between the groups (FDR < 0.1) in BALF and lung tissue homogenates, respectively. Of those, HGF, TGF-α, and CCL2 were identified as the most relevant to this study. Their protein expression patterns were verified by ELISA. This study confirmed that post-stroke lung damage was not associated with increased lung permeability or cerebral ischemia severity. Furthermore, the dysregulation of HGF, TGF-α, and CCL2 in BALF and lung tissue after ischemia could play an important role in the molecular mechanisms underlying stroke-induced lung damage.

The Connection Between Selected Caspases Levels in Bronchoalveolar Lavage Fluid and Severity After Brain Injury

Objective

The interaction between the brain and lungs has been the subject of many clinical reports, while the exact impact of brain injury on the physiology of the respiratory system is still subject to numerous experimental studies. The purpose of this study was to investigate the activation of selected caspases levels in bronchoalveolar lavage fluid (mini BALF) of patients after isolated brain injury and their correlation with the severity of the injury.

Methods

The analysis was performed on patients who were admitted to the intensive care unit (ICU) for severe isolated brain injury from March 2018 to April 2020. All patients were intubated and mechanically ventilated. Mini BALF was collected within the first 6–8 h after trauma and on days 3 and 7 after admission. The concentrations of selected caspases were determined and correlated with the severity of brain injury evaluated by the Rotterdam CT Score, Glasgow Coma Score, and 28-day mortality.

Results

Our results showed significantly elevated levels of selected caspases on days 3 and 7 after brain injury, and revealed apoptosis activation during the first 7 days after brain trauma. We found a significant different correlation between the elevation of selected caspases 3, 6, 8, and 9, and the Glasgow Coma Score, Rotterdam CT scale, and 28-day mortality.

Conclusions

The increased levels of selected caspases in the mini BALF in our patients indicate an intensified activation of apoptosis in the lungs, which is related to brain injury itself via various apoptotic pathways and correlates with the severity of brain injury.

Pulmonary complications and respiratory management in neurocritical care: a narrative review

ABSTRACT

Neurocritical care (NCC) is not only generally guided by principles of general intensive care, but also directed by specific goals and methods. This review summarizes the common pulmonary diseases and pathophysiology affecting NCC patients and the progress made in strategies of respiratory support in NCC. This review highlights the possible interactions and pathways that have been revealed between neurological injuries and respiratory diseases, including the catecholamine pathway, systemic inflammatory reactions, adrenergic hypersensitivity, and dopaminergic signaling. Pulmonary complications of neurocritical patients include pneumonia, neurological pulmonary edema, and respiratory distress. Specific aspects of respiratory management include prioritizing the protection of the brain, and the goal of respiratory management is to avoid inappropriate blood gas composition levels and intracranial hypertension. Compared with the traditional mode of protective mechanical ventilation with low tidal volume (Vt), high positive end-expiratory pressure (PEEP), and recruitment maneuvers, low PEEP might yield a potential benefit in closing and protecting the lung tissue. Multimodal neuromonitoring can ensure the safety of respiratory maneuvers in clinical and scientific practice. Future studies are required to develop guidelines for respiratory management in NCC.

Lung-brain 'cross-talk': systemic propagation of cytokines in the ARDS via the bloodstream using a blood transfusion model does not influence cerebral inflammatory response in pigs

Background

Interorgan cross-talk describes the phenomenon in which a primarily injured organ causes secondary damage to a distant organ. This cross-talk is well known between the lung and brain. One theory suggests that the release and systemic distribution of cytokines via the bloodstream from the primarily affected organ sets in motion proinflammatory cascades in distant organs. In this study, we analysed the role of the systemic distribution of cytokines via the bloodstream in a porcine ARDS model for organ cross-talk and possible inflammatory changes in the brain.

Methods

After approval of the State and Institutional Animal Care Committee, acute respiratory distress syndrome (ARDS) induction with oleic acid injection was performed in seven animals. Eight hours after ARDS induction, blood (35-40 ml kg^-1) was taken from these seven 'ARDS donor' pigs. The collected 'ARDS donor' blood was transfused into seven healthy 'ARDS-recipient' pigs. Three animals served as a control group, and blood from these animals was transfused into three healthy pigs after an appropriate ventilation period. All animals were monitored for 8 h using advanced cardiorespiratory monitoring. Postmortem assessment included cerebral (hippocampal and cortex) mediators of early inflammatory response (IL-6, TNF-alpha, iNOS, sLCN-2), wet-to-dry ratio and lung histology. TNF-alpha serum concentration was measured in all groups.

Results

ARDS was successfully induced in the 'ARDS donor' group, and serum TNF-alpha levels were elevated compared with the 'ARDS-recipient' group. In the 'ARDS-recipient' group, neither significant ARDS alterations nor upregulation of inflammatory mediators in the brain tissue were detected after high-volume random allogenic 'ARDS-blood' transfusion. The role of the systemic distribution of inflammatory cytokines from one affected organ to another could not be confirmed in this study.

Efficacy analysis of the lung recruitment maneuver in correcting pulmonary atelectasis in neurological intensive care unit-a retrospective study

Background

Atelectasis after supratentorial craniotomy is common. It can lead to the decrease of arterial partial pressure of oxygen (PaO₂) in patients with neurosurgical intensive care units (NICU), and the recovery of neurological function is more and more difficult. However, due to the particularity of maintaining the stability of intracranial pressure (ICP), there are few reports on effective ways to alleviate atelectasis and improve oxygenation in patients with NICU effectively.

Methods

A retrospective analysis was conducted to analyze the clinical data of patients with atelectasis who received lung recruitment maneuver in the NICU. This study collected data on 33 patients. Of these, 17 patients had traumatic brain injury and 16 patients had spontaneous intracranial hemorrhage. PaO₂, oxygenation index (OI), tidal volume, positive end-expiratory pressure (PEEP), respiratory system compliance, plateau pressure, respiratory rate, minute ventilation and chest computed tomography (CT) or portable chest X-ray images were compared before and after recruitment. As for safety evaluation indicators, we reviewed the invasive arterial blood pressure, heart rate, heart rhythm, and subcutaneous emphysema in all patients. Before and after lung recruitment, the data were compared using the paired t-test and the Wilcoxon test.

Results

Compared with tidal volume 8.1 [6.85-10.05] mL/kg, minute ventilation volume (9.3±1.3 L/min), respiratory system compliance 60 [39-80] mL/cmH₂O, respiratory rate 17 [16-21.5] breaths/min, PEEP 4 [4-6] cmH₂O, plateau pressure 19 [17-23] cmH₂O, PaO₂ (104.2±33.17 mmHg) and OI (250.6±87.65 mmHg) before lung recruitment, tidal volume 9 [8.05-10.65] mL/kg, minute ventilation (9.7±1.1 L/min), respiratory system compliance 69 [50-82.5] mL/cmH₂O, respiratory rate 17 [14-18.5] breaths/min, PEEP 4 [4-5] cmH₂O, plateau pressure 18 [16-19.5] cmH₂O, PaO₂ (127.3±34.95 mmHg) and OI (306.9±96.52 mmHg) of patients were significantly improved after recruitment after recruitment (all P<0.05). In all patients, chest CT showed a decrease in atelectasis area and bilateral pulmonary exudates in 25 patients after lung recruitment maneuver. X-ray after recruitment in 2 patients showed increased lung tissue transparency and decreased ground-glass shadowing, while improvements were not obvious in 6 patients.

Conclusions

For patients diagnosed with atelectasis in the NICU, lung recruitment maneuver can improve atelectasis, increase PaO₂, and improve oxygenation.

Brain-lung interaction: a vicious cycle in traumatic brain injury

The brain-lung interaction can seriously affect patients with traumatic brain injury, triggering a vicious cycle that worsens patient prognosis. Although the mechanisms of the interaction are not fully elucidated, several hypotheses, notably the "blast injury" theory or "double hit" model, have been proposed and constitute the basis of its development and progression. The brain and lungs strongly interact via complex pathways from the brain to the lungs but also from the lungs to the brain. The main pulmonary disorders that occur after brain injuries are neurogenic pulmonary edema, acute respiratory distress syndrome, and ventilator-associated pneumonia, and the principal brain disorders after lung injuries include brain hypoxia and intracranial hypertension. All of these conditions are key considerations for management therapies after traumatic brain injury and need exceptional case-by-case monitoring to avoid neurological or pulmonary complications. This review aims to describe the history, pathophysiology, risk factors, characteristics, and complications of brain-lung and lung-brain interactions and the impact of different old and recent modalities of treatment in the context of traumatic brain injury.

Sepsis-Exacerbated Brain Dysfunction After Intracerebral Hemorrhage

Sepsis susceptibility is significantly increased in patients with intracerebral hemorrhage (ICH), owing to immunosuppression and intestinal microbiota dysbiosis. To date, ICH with sepsis occurrence is still difficult for clinicians to deal with, and the mortality, as well as long-term cognitive disability, is still increasing. Actually, intracerebral hemorrhage and sepsis are mutually exacerbated via similar pathophysiological mechanisms, mainly consisting of systemic inflammation and circulatory dysfunction. The main consequence of these two processes is neural dysfunction and multiple organ damages, notably, via oxidative stress and neurotoxic mediation under the mediation of central nervous system activation and blood-brain barrier disruption. Besides, the comorbidity-induced multiple organ damages will produce numerous damage-associated molecular patterns and consequently exacerbate the severity of the disease. At present, the prospective views are about operating artificial restriction for the peripheral immune system and achieving cross-tolerance among organs via altering immune cell composition to reduce inflammatory damage.

Molecular hydrogen alleviates lung injury after traumatic brain injury: Pyroptosis and apoptosis

BACKGROUND

Traumatic brain injury (TBI)-induced acute lung injury (ALI) is a critical condition, and inflammation and apoptosis play essential roles. Molecular hydrogen (H₂) exerts anti-inflammatory and anti-apoptotic effects. Our previous work has shown that 42% H₂ can improve TBI. In the current study, we tested the hypothesis that inhalation of hydrogen (42% H₂, 21% O₂, balanced nitrogen) for 1 h per day can improve TBI-induced ALI.

METHODS

Sprague-Dawley male rats were randomly divided into 3 groups. Except for the sham group (group S), rats were subjected to a fluid percussion injury (FPI) and the H₂ treatment group were given inhaled hydrogen for 1 h per day. We evaluated the lung function, pyroptosis and apoptosis at 24 h, 48 h and 72 h.

RESULTS

Compared with group S, the rats in the TBI group (group T) showed obvious pulmonary edema after a TBI. Inhalation of high-concentration hydrogen significantly improved the rats. During this process, rats had some tendency to heal on their own, and H₂ also accelerated the self-healing process. Lung injury scores, oxygenation index and pulmonary edema were consistent. Compared with group S, the pyroptosis-related proteins Caspase-1, apoptosis-associated speck-like protein containing CARD (ASC) and Gasdermin-D (GSDM-D) in the lung tissues of the rats in group T were significantly increased after a TBI. In the H₂ treatment group (group H), these proteins were significantly decreased. The levels of IL-1β and IL-18 were significantly increased after TBI while in group H were significantly decreased. At the same time, cleaved caspase-3 and BCL-2/Bax were also changed after H₂ treatment. These demonstrates the powerful ameliorating effect of H₂ on pyroptosis, apoptosis and systemic inflammation. However, rats also had tendency to heal on their own, and H₂ also accelerated the self-healing process at the same time.

CONCLUSIONS

H₂ improves TBI-ALI, and the mechanism may be due to the decrease of both pyroptosis and apoptosis and the alleviation of inflammation. These findings provide a reference and evidence for the use of H₂ in TBI-ALI patients in the intensive care unit (ICU).

Focused Management of Patients With Severe Acute Brain Injury and ARDS

Considering the COVID-19 pandemic where concomitant occurrence of ARDS and severe acute brain injury (sABI) has increasingly coemerged, we synthesize existing data regarding the simultaneous management of both conditions. Our aim is to provide readers with fundamental principles and concepts for the management of sABI and ARDS, and highlight challenges and conflicts encountered while managing concurrent disease. Up to 40% of patients with sABI can develop ARDS. Although there are trials and guidelines to support the mainstays of treatment for ARDS and sABI independently, guidance on concomitant management is limited. Treatment strategies aimed at managing severe ARDS may at times conflict with the management of sABI. In this narrative review, we discuss the physiological basis and risks involved during simultaneous management of ARDS and sABI, summarize evidence for treatment decisions, and demonstrate these principles using hypothetical case scenarios. Use of invasive or noninvasive monitoring to assess brain and lung physiology may facilitate goal-directed treatment strategies with the potential to improve outcome. Understanding the pathophysiology and key treatment concepts for comanagement of these conditions is critical to optimizing care in this high-acuity patient population.

Noninvasive and invasive mechanical ventilation for neurologic disorders

Patients with acute neurologic injuries frequently require mechanical ventilation due to diminished airway protective reflexes, cardiopulmonary failure secondary to neurologic insults, or to facilitate gas exchange to precise targets. Mechanical ventilation enables tight control of oxygenation and carbon dioxide levels, enabling clinicians to modulate cerebral hemodynamics and intracranial pressure with the goal of minimizing secondary brain injury. In patients with acute spinal cord injuries, neuromuscular conditions, or diseases of the peripheral nerve, mechanical ventilation enables respiratory support under conditions of impending or established respiratory failure. Noninvasive ventilatory approaches may be carefully considered for certain disease conditions, including myasthenia gravis and amyotrophic lateral sclerosis, but may be inappropriate in patients with Guillain-Barré syndrome or when relevant contra-indications exist. With regard to discontinuing mechanical ventilation, considerable uncertainty persists about the best approach to wean patients, how to identify patients ready for extubation, and when to consider primary tracheostomy. Recent consensus guidelines highlight these and other knowledge gaps that are the focus of active research efforts. This chapter outlines important general principles to consider when initiating, titrating, and discontinuing mechanical ventilation in patients with acute neurologic injuries. Important disease-specific considerations are also reviewed where appropriate.

Comparative effects of dexmedetomidine and propofol on brain and lung damage in experimental acute ischemic stroke

Acute ischemic stroke is associated with pulmonary complications, and often dexmedetomidine and propofol are used to decrease cerebral metabolic rate. However, it is unknown the immunomodulatory actions of dexmedetomidine and propofol on brain and lungs during acute ischemic stroke. The effects of dexmedetomidine and propofol were compared on perilesional brain tissue and lung damage after acute ischemic stroke in rats. Further, the mean amount of both sedatives was directly evaluated on alveolar macrophages and lung endothelial cells primarily extracted 24-h after acute ischemic stroke. In twenty-five Wistar rats, ischemic stroke was induced and after 24-h treated with sodium thiopental (STROKE), dexmedetomidine and propofol. Dexmedetomidine, compared to STROKE, reduced diffuse alveolar damage score [median(interquartile range); 12(7.8–15.3) vs. 19.5(18–24), p = 0.007)], bronchoconstriction index [2.28(2.08–2.36) vs. 2.64(2.53–2.77), p = 0.006], and TNF-α expression (p = 0.0003), while propofol increased VCAM-1 expression compared to STROKE (p = 0.0004). In perilesional brain tissue, dexmedetomidine, compared to STROKE, decreased TNF-α (p = 0.010), while propofol increased VCAM-1 compared to STROKE (p = 0.024). In alveolar macrophages and endothelial cells, dexmedetomidine decreased IL-6 and IL-1β compared to STROKE (p = 0.002, and p = 0.040, respectively), and reduced IL-1β compared to propofol (p = 0.014). Dexmedetomidine, but not propofol, induced brain and lung protection in experimental acute ischemic stroke.

Pulmonary injury as a predictor of cerebral hypoxia in traumatic brain injury: from physiology to physiopathology

Traumatic brain injury is caused by mechanical forces impacting the skull and its internal structures and constitutes one of the main causes of morbidity and mortality in the world. Clinically, severe traumatic brain injury is associated with the development of acute lung injury and so far, few studies have evaluated the cellular, molecular and immunological mechanisms involved in this pathophysiological process. Knowing and investigating these mechanisms allows us to correlate pulmonary injury as a predictor of cerebral hypoxia in traumatic brain injury and to use this finding in decision making during clinical practice. This review aims to provide evidence on the importance of the pathophysiology of traumatic brain injury-acute lung injury, and thus confirm its role as a predictor of cerebral hypoxia, helping to establish an appropriate therapeutic strategy to improve functional outcomes and reduce mortality.

Brain-lung interactions and mechanical ventilation in patients with isolated brain injury

During the last decade, experimental and clinical studies have demonstrated that isolated acute brain injury (ABI) may cause severe dysfunction of peripheral extracranial organs and systems. Of all potential target organs and systems, the lung appears to be the most vulnerable to damage after brain injury (BI). The pathophysiology of these brain–lung interactions are complex and involve neurogenic pulmonary oedema, inflammation, neurodegeneration, neurotransmitters, immune suppression and dysfunction of the autonomic system. The systemic effects of inflammatory mediators in patients with BI create a systemic inflammatory environment that makes extracranial organs vulnerable to secondary procedures that enhance inflammation, such as mechanical ventilation (MV), surgery and infections. Indeed, previous studies have shown that in the presence of a systemic inflammatory environment, specific neurointensive care interventions—such as MV—may significantly contribute to the development of lung injury, regardless of the underlying mechanisms. Although current knowledge supports protective ventilation in patients with BI, it must be born in mind that ABI-related lung injury has distinct mechanisms that involve complex interactions between the brain and lungs. In this context, the role of extracerebral pathophysiology, especially in the lungs, has often been overlooked, as most physicians focus on intracranial injury and cerebral dysfunction. The present review aims to fill this gap by describing the pathophysiology of complications due to lung injuries in patients with a single ABI, and discusses the possible impact of MV in neurocritical care patients with normal lungs.

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.

Stroke-induced immunosuppression: implications for the prevention and prediction of post-stroke infections

Stroke produces a powerful inflammatory cascade in the brain, but also a suppression of the peripheral immune system, which is also called stroke-induced immunosuppression (SIIS). The main processes that lead to SIIS are a shift from a lymphocyte phenotype T-helper (Th) 1 to a Th2 phenotype, a decrease of the lymphocyte counts and NK cells in the blood and spleen, and an impairment of the defense mechanisms of neutrophils and monocytes. The direct clinical consequence of SIIS in stroke patients is an increased susceptibility to stroke-associated infections, which is enhanced by clinical factors like dysphagia. Among these infections, stroke-associated pneumonia (SAP) is the one that accounts for the highest impact on stroke outcome, so research is focused on its early diagnosis and prevention. Biomarkers indicating modifications in SIIS pathways could have an important role in the early prediction of SAP, but currently, there are no individual biomarkers or panels of biomarkers that are accurate enough to be translated to clinical practice. Similarly, there is still no efficient therapy to prevent the onset of SAP, and clinical trials testing prophylactic antibiotic treatment and β-blockers have failed. However, local immunomodulation could open up a new research opportunity to find a preventive therapy for SAP. Recent studies have focused on the pulmonary immune changes that could be caused by stroke similarly to other acquired brain injuries. Some of the traits observed in animal models of stroke include lung edema and inflammation, as well as inflammation of the bronchoalveolar lavage fluid.

Therapeutic Effect and Mechanisms of Essential Oils in Mood Disorders: Interaction between the Nervous and Respiratory Systems

Essential oils (EOs) are extracted from plants and contain active components with therapeutic effects. Evidence shows that various types of EOs have a wide range of health benefits. In our previous studies, the potential of lavender EO for prevention and even treatment of depression and anxiety symptoms was demonstrated. The favourable outcomes may be due to multiple mechanisms, including the regulation of monoamine level, the induction of neurotrophic factor expression, the regulation of the endocrine system and the promotion of neurogenesis. The molecules of EOs may reach the brain and exert an effect through two distinctive pathways, namely, the olfactory system and the respiratory system. After inhalation, the molecules of the EOs would either act directly on the olfactory mucosa or pass into the respiratory tract. These two delivery pathways suggest different underlying mechanisms of action. Different sets of responses would be triggered, such as increased neurogenesis, regulation of hormonal levels, activation of different brain regions, and alteration in blood biochemistry, which would ultimately affect both mood and emotion. In this review, we will discuss the clinical effects of EOs on mood regulation and emotional disturbances as well as the cellular and molecular mechanisms of action. Emphasis will be put on the interaction between the respiratory and central nervous system and the involved potential mechanisms. Further evidence is needed to support the use of EOs in the clinical treatment of mood disturbances. Exploration of the underlying mechanisms may provide insight into the future therapeutic use of EO components treatment of psychiatric and physical symptoms.

The effects of arterial CO2 on the injured brain: Two faces of the same coin

Serum levels of carbon dioxide (CO₂) closely regulate cerebral blood flow (CBF) and actively participate in different aspects of brain physiology such as hemodynamics, oxygenation, and metabolism. Fluctuations in the partial pressure of arterial CO₂ (PaCO₂) modify the aforementioned variables, and at the same time influence physiologic parameters in organs such as the lungs, heart, kidneys, and the gastrointestinal tract. In general, during acute brain injury (ABI), maintaining normal PaCO₂ is the target to be achieved. Both hypercapnia and hypocapnia may comprise secondary insults and should be avoided during ABI. The risks of hypocapnia mostly outweigh the potential benefits. Therefore, its therapeutic applicability is limited to transient and second-stage control of intracranial hypertension. On the other hand, inducing hypercapnia could be beneficial when certain specific situations require increasing CBF. The evidence supporting this claim is very weak. This review attempts providing an update on the physiology of CO₂, its risks, benefits, and potential utility in the neurocritical care setting.

The Perioperative Management of Subarachnoid Hemorrhage During the Coronavirus Disease 2019 Pandemic in China

Background

For most of the international community outside the epicenter, coronavirus disease 2019 (COVID-19) containment is normalizing, and daily medical practice runs parallel to preventing and treating COVID-19. This experience of simultaneously conducting emergent surgery and infection control for COVID-19 disease is useful outside the epicenter during the pandemic.

Case Description

In this single-center retrospective observational study, we enrolled patients with subarachnoid hemorrhage (SAH) who were emergently admitted from January 23 to April 8, 2020. Based on the COVID-19 triage, patients with SAH were divided into 3 categories: positive, negative, and under investigation. During 77 days, 90 patients with SAH were admitted at the center. The median age was 55 years (range, 18–80 years) and 40 patients (44.4%) were male. None was positive, 42 patients were negative, and 48 patients were under investigation for COVID-19 before surgery. During the same period, 9 patients were diagnosed with COVID-19 without nosocomial infection.

Conclusions

Rescuing patients with SAH and containment of COVID-19 benefit from joint prevention and control, a centralized system of equipment distribution and personnel assignment, and quick workflow establishment.

Neurogenic pulmonary edema following acute stroke: The progress and perspective

Neurogenic pulmonary edema (NPE) following acute stroke is an acute respiratory distress syndrome (ARDS) with clinical characteristics that include acute onset, apparent pulmonary interstitial fluid infiltration and rapid resolution. The pathological process of NPE centers on sympathetic stimulation and fulminant release of catecholamines, which cause contraction of resistance vessels. Elevated systemic resistance forces fluid into pulmonary circulation, while pulmonary circulation overload induces pulmonary capillary pressure that elevates, and in turn damages the alveolar capillary barrier. Damage to the alveolar capillary barrier leads to pulmonary ventilation disorder, blood perfusion disorder and oxygenation disorder. Eventually, NPE will cause post-stroke patients' prognosis to further deteriorate. At present, we lack specific biological diagnostic indicators and a meticulously unified diagnostic criterion, and this results in a situation in which many patients are not recognized quickly and/or diagnosed accurately. There are no drugs that are effective against NPE. Therefore, understanding how to diagnose NPE early by identifying the risk factors and how to apply appropriate treatment to avoid a deteriorating prognosis are important scientific goals. We will elaborate the progress of NPE after acute stroke in terms of its pathophysiological mechanisms, etiology, epidemiology, clinical diagnosis and early prediction, comprehensive treatment strategies, and novel drug development. We also propose our own thinking and prospects regarding NPE.

Neural-respiratory inflammasome axis in traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality. Approximately 20-25% of TBI subjects develop Acute Lung Injury (ALI), but the pathomechanisms of TBI-induced ALI remain poorly defined. Currently, mechanical ventilation is the only therapeutic intervention for TBI-induced lung injury. Our recent studies have shown that the inflammasome plays an important role in the systemic inflammatory response leading to lung injury-post TBI. Here, we outline the role of the extracellular vesicle (EV)-mediated inflammasome signaling in the etiology of TBI-induced ALI. Furthermore, we evaluate the efficacy of a low molecular weight heparin (Enoxaparin, a blocker of EV uptake) and a monoclonal antibody against apoptosis speck-like staining protein containing a caspase recruitment domain (anti-ASC) as therapeutics for TBI-induced lung injury. We demonstate that activation of an EV-mediated Neural-Respiratory Inflammasome Axis plays an essential role in TBI-induced lung injury and disruption of this axis has therapeutic potential as a treatment strategy.

Long-Term Cognitive Outcome and Brain Imaging in Adults After Extracorporeal Membrane Oxygenation

OBJECTIVES

To investigate the presence of cognitive dysfunction and brain lesions in long-term survivors after treatment with extracorporeal membrane oxygenation for severe respiratory failure, and to see whether patients with prolonged hypoxemia were at increased risk.

DESIGN

A single-center retrospective cohort study.

SETTING

Tertiary referral center for extracorporeal membrane oxygenation in Sweden.

PATIENTS

Long-term survivors treated between 1995 and July 2009. Seven patients from a previously published study investigated with a similar protocol were included.

INTERVENTIONS

Brain imaging, neurocognitive testing, interview.

MEASUREMENTS AND MAIN RESULTS

Thirty-eight patients (i.e., n = 31 + 7) were enrolled and investigated in median 9.0 years after discharge. Only memory tests were performed in 10 patients, mainly due to a lack of formal education necessary for the test results to be reliable. Median full-scale intelligence quotient, memory index, and executive index were 97, 101, and 104, respectively (normal, 100 ± 15). Cognitive function was not reduced in the group with prolonged hypoxemia. Brain imaging showed cerebrovascular lesions in 14 of 38 patients (37%), most commonly in the group treated with venoarterial extracorporeal membrane oxygenation (7/11, 64%). In this group, memory function and executive function were significantly reduced.

CONCLUSIONS

Patients treated with extracorporeal membrane oxygenation for respiratory failure may have normal cognitive function years after treatment, if not affected by cerebrovascular lesions. Permissive hypoxemia was not correlated with long-term cognitive dysfunction in the present study. Further prospective studies with minimal loss to follow-up are direly needed to confirm our findings.

Random allogeneic blood transfusion in pigs: characterisation of a novel experimental model

Background

Organ cross-talk describes interactions between a primary affected organ and a secondarily injured remote organ, particularly in lung-brain interactions. A common theory is the systemic distribution of inflammatory mediators that are released by the affected organ and transferred through the bloodstream. The present study characterises the baseline immunogenic effects of a novel experimental model of random allogeneic blood transfusion in pigs designed to analyse the role of the bloodstream in organ cross-talk.

Methods

After approval of the State and Institutional Animal Care Committee, 20 anesthetized pig were randomized in a donor and an acceptor (each n = 8): the acceptor animals each received high-volume whole blood transfusion from the donor (35–40 ml kg⁻¹). Four animals received balanced electrolyte solution instead of blood transfusion (control group; n = 4). Afterwards the animals underwent extended cardiorespiratory monitoring for eight hours. Post mortem assessment included pulmonary, cerebral and systemic mediators of early inflammatory response (IL-6, TNF-alpha, iNOS), wet to dry ratio, and lung histology.

Results

No adverse events or incompatibilities occurred during the blood transfusion procedures. Systemic cytokine levels and pulmonary function were unaffected. Lung histopathology scoring did not display relevant intergroup differences. Neither within the lung nor within the brain an up-regulation of inflammatory mediators was detected. High volume random allogeneic blood transfusion in pigs neither impaired pulmonary integrity nor induced systemic, lung, or brain inflammatory response.

Conclusion

This approach can represent a novel experimental model to characterize the blood-bound transmission in remote organ injury.

Association between neurodegenerative diseases and pneumonia: a retrospective population-based study

PURPOSE

The association between pneumonia and neurodegenerative diseases (NDs) has never been reported in detail. We address this relationship with reference to the general population.

METHODS

Using Taiwan's National Health Insurance Research Database to identify a pneumonia cohort (including the typical and atypical), we established an ND cohort of 19,062 patients and a non-ND cohort of 76,227 people. In both cohorts, the risk of pneumonia was measured using multivariable Cox proportional hazards models.

RESULTS

The adjusted hazard ratio (aHR) (95% confidence interval [CI]) for the pneumonia cohort was 2.10 (1.96-2.24), regardless of age, sex, comorbidities or drug use in the ND cohort. The aHR (95% CI) for adults aged 20-49 years was 2.08 (1.58-2.75), men 2.20 (2.01-2.40). However, older subjects were at greatest risk of pneumonia, (3.41 [2.99-3.88]) if the 20-49 years age group is used as the reference. For the ND and non-ND cohorts, those with comorbidities (with the exception of hyperlipidemia) had higher risk; aHR (95% CI) 2.35 (2.30-2.52). The aHR (95% CI) for those without comorbidities is 3.28 (2.52-4.26). No significant difference was observed in incidence of pneumonia between those who were and were not using statin medications; the aHR (95% CI) was 1.03 (0.93-1.14).

CONCLUSION

The ND cohort had a higher risk of pneumonia, regardless of age, sex, comorbidities or statin use. The risk of pneumonia was higher in elderly and male patients in the ND cohort.

Human Lung Cell Pyroptosis Following Traumatic Brain Injury

Approximately 30% of traumatic brain injured patients suffer from acute lung injury or acute respiratory distress syndrome. Our previous work revealed that extracellular vesicle (EV)-mediated inflammasome signaling plays a crucial role in the pathophysiology of traumatic brain injury (TBI)-induced lung injury. Here, serum-derived EVs from severe TBI patients were analyzed for particle size, concentration, origin, and levels of the inflammasome component, an apoptosis-associated speck-like protein containing a caspase-recruiting domain (ASC). Serum ASC levels were analyzed from EV obtained from patients that presented lung injury after TBI and compared them to EV obtained from patients that did not show any signs of lung injury. EVs were co-cultured with lung human microvascular endothelial cells (HMVEC-L) to evaluate inflammasome activation and endothelial cell pyroptosis. TBI patients had a significant increase in the number of serum-derived EVs and levels of ASC. Severe TBI patients with lung injury had a significantly higher level of ASC in serum and serum-derived EVs compared to individuals without lung injury. Only EVs isolated from head trauma patients with gunshot wounds were of neural origin. Delivery of serum-derived EVs to HMVEC-L activated the inflammasome and resulted in endothelial cell pyroptosis. Thus, serum-derived EVs and inflammasome proteins play a critical role in the pathogenesis of TBI-induced lung injury, supporting activation of an EV-mediated neural-respiratory inflammasome axis in TBI-induced lung injury.