Chronic Critical Illness and Persistent Inflammation: What can we Learn from the Elderly, Injured, Septic, and Malnourished?

Managing the Chronically Ventilated Critically Ill Population

Advances in intensive care over the past few decades have significantly improved the chances of survival for patients with acute critical illness. However, this progress has also led to a growing population of patients who are dependent on intensive care therapies, including prolonged mechanical ventilation (PMV), after the initial acute period of critical illness. These patients are referred to as the "chronically critically ill" (CCI). CCI is a syndrome characterized by prolonged mechanical ventilation, myoneuropathies, neuroendocrine disorders, nutritional deficiencies, cognitive and psychiatric issues, and increased susceptibility to infections. It is associated with high morbidity and mortality as well as a significant increase in healthcare costs. In this article, we will review disease burden, outcomes, psychiatric effects, nutritional and ventilator weaning strategies as well as the role of palliative care for CCI with a specific focus on those requiring PMV.

The double sides of NLRP3 inflammasome activation in sepsis

Sepsis is defined as a life-threatening organ dysfunction induced by a dysregulated host immune response to infection. Immune response induced by sepsis is complex and dynamic. It is schematically described as an early dysregulated systemic inflammatory response leading to organ failures and early deaths, followed by the development of persistent immune alterations affecting both the innate and adaptive immune responses associated with increased risk of secondary infections, viral reactivations, and late mortality. In this review, we will focus on the role of NACHT, leucin-rich repeat and pyrin-containing protein 3 (NLRP3) inflammasome in the pathophysiology of sepsis. NLRP3 inflammasome is a multiproteic intracellular complex activated by infectious pathogens through a two-step process resulting in the release of the pro-inflammatory cytokines IL-1β and IL-18 and the formation of membrane pores by gasdermin D, inducing a pro-inflammatory form of cell death called pyroptosis. The role of NLRP3 inflammasome in the pathophysiology of sepsis can be ambivalent. Indeed, although it might protect against sepsis when moderately activated after initial infection, excessive NLRP3 inflammasome activation can induce dysregulated inflammation leading to multiple organ failure and death during the acute phase of the disease. Moreover, this activation might become exhausted and contribute to post-septic immunosuppression, driving impaired functions of innate and adaptive immune cells. Targeting the NLRP3 inflammasome could thus be an attractive option in sepsis either through IL-1β and IL-18 antagonists or through inhibition of NLRP3 inflammasome pathway downstream components. Available treatments and results of first clinical trials will be discussed.

Surgical Science and the Evolution of Critical Care Medicine

Surgical science has driven innovation and inquiry across adult and pediatric disciplines that provide critical care regardless of location. Surgically originated but broadly applicable knowledge has been globally shared within the pages Critical Care Medicine over the last 50 years.

Biological signatures and prediction of an immunosuppressive status-persistent critical illness-among orthopedic trauma patients using machine learning techniques

BACKGROUND

Persistent critical illness (PerCI) is an immunosuppressive status. The underlying pathophysiology driving PerCI remains incompletely understood. The objectives of the study were to identify the biological signature of PerCI development, and to construct a reliable prediction model for patients who had suffered orthopedic trauma using machine learning techniques.

METHODS

This study enrolled 1257 patients from the Medical Information Mart for Intensive Care III (MIMIC-III) database. Lymphocytes were tracked from ICU admission to more than 20 days following admission to examine the dynamic changes over time. Over 40 possible variables were gathered for investigation. Patients were split 80:20 at random into a training cohort (n=1035) and an internal validation cohort (n=222). Four machine learning algorithms, including random forest, gradient boosting machine, decision tree, and support vector machine, and a logistic regression technique were utilized to train and optimize models using data from the training cohort. Patients in the internal validation cohort were used to validate models, and the optimal one was chosen. Patients from two large teaching hospitals were used for external validation (n=113). The key metrics that used to assess the prediction performance of models mainly included discrimination, calibration, and clinical usefulness. To encourage clinical application based on the optimal machine learning-based model, a web-based calculator was developed.

RESULTS

16.0% (201/1257) of all patients had PerCI in the MIMIC-III database. The means of lymphocytes (%) were consistently below the normal reference range across the time among PerCI patients (around 10.0%), whereas in patients without PerCI, the number of lymphocytes continued to increase and began to be in normal range on day 10 following ICU admission. Subgroup analysis demonstrated that patients with PerCI were in a more serious health condition at admission since those patients had worse nutritional status, more electrolyte imbalance and infection-related comorbidities, and more severe illness scores. Eight variables, including albumin, serum calcium, red cell volume distributing width (RDW), blood pH, heart rate, respiratory failure, pneumonia, and the Sepsis-related Organ Failure Assessment (SOFA) score, were significantly associated with PerCI, according to the least absolute shrinkage and selection operator (LASSO) logistic regression model combined with the 10-fold cross-validation. These variables were all included in the modelling. In comparison to other algorithms, the random forest had the optimal prediction ability with the highest area under receiver operating characteristic (AUROC) (0.823, 95% CI: 0.757-0.889), highest Youden index (1.571), and lowest Brier score (0.107). The AUROC in the external validation cohort was also up to 0.800 (95% CI: 0.688-0.912). Based on the risk stratification system, patients in the high-risk group had a 10.0-time greater chance of developing PerCI than those in the low-risk group. A web-based calculator was available at https://starxueshu-perci-prediction-main-9k8eof.streamlitapp.com/.

CONCLUSIONS

Patients with PerCI typically remain in an immunosuppressive status, but those without PerCI gradually regain normal immunity. The dynamic changes of lymphocytes can be a reliable biomarker for PerCI. This work developed a reliable model that may be helpful in improving early diagnosis and targeted intervention of PerCI. Beneficial interventions, such as improving nutritional status and immunity, maintaining electrolyte and acid-base balance, curbing infection, and promoting respiratory recovery, are early warranted to prevent the onset of PerCI, especially among patients in the high-risk group and those with a continuously low level of lymphocytes.

Multiple Organ Dysfunction in Older Major Trauma Critical Care Patients: A Multicenter Prospective Observational Study

The objective was to explore the characteristics and outcomes of multiple organ dysfunction syndrome (MODS) in older trauma patients.

Background

Severely injured older people present an increasing challenge for trauma systems. Recovery for those who require critical care may be complicated by MODS. In older trauma patients, MODS may not be predictable based on chronological age alone and factors associated with its development and resolution are unclear.

Methods

Consecutive adult patients (aged ≥16 years) admitted to 4 level 1 major trauma center critical care units were enrolled and reviewed daily until discharge or death. MODS was defined by a daily total sequential organ failure assessment score of >5.

Results

One thousand three hundred sixteen patients were enrolled over 18 months and one-third (434) were aged ≥65 years. Incidence of MODS was high for both age groups (<65 years: 64%, ≥65 years: 70%). There were few differences in severity, patterns, and duration of MODS between cohorts, except for older traumatic brain injury (TBI) patients who experienced a prolonged course of MODS recovery (TBI: 9 days vs no TBI: 5 days, P < 0.01). Frailty rather than chronological age had a strong association with MODS development (odds ratio [OR], 6.9; 95% confidence intervals [CI], 3.0-12.4; P < 0.001) and MODS mortality (OR, 2.1; 95% CI, 1.31-3.38; P = 0.02). Critical care resource utilization was not increased in older patients, but MODS had a substantial impact on mortality (<65 years: 17%; ≥65 years: 28%). The majority of older patients who did not develop MODS survived and had favorable discharge outcomes (home discharge ≥65 years NoMODS: 50% vs MODS: 15%; P < 0.01).

Conclusions

Frailty rather than chronological age appears to drive MODS development, recovery, and outcome in older cohorts. Early identification of frailty after trauma may help to predict MODS and plan care in older trauma.

Improving nutritional therapy of persistent critically ill patients by organisational measures: A before and after study

BACKGROUND & AIMS

Critically ill patients requiring prolonged intensive care (ICU) treatment are at high risk of malnutrition, which latter contributes to worsening outcome. Having observed that despite the presence of a nutrition protocol and dieticians, the patients with persistent critical illness (PCI) had been underfed during their ICU stay and particularly during the first 10 days, the aim was to analyse the impact of the organisational changes that were proposed to prevent the observed malnutrition.

METHODS

Before (Period A) and after (Period B) study enrolling critically ill patients consecutively admitted, requiring >10 days of ICU treatment. The intervention consisted in increasing the early morning interactions between dieticians, nurses, and physicians, while modifying the computer visualisation of the dietician proposals. The primary endpoint was a reduction in the cumulative energy balance in period B. The ICU stay was divided in early ICU stay (first 10 days) and late ICU stay (day 11 to day 30). Other variables: protein, glucose, and prealbumin.

RESULTS

Altogether, 205 patients (150 and 55 in period A and B respectively) were enrolled in the PCI program. Patient characteristics were similar over both periods except for lower SAPSII score in period B. There was no difference in nutritional pattern in the first 10 days between periods. The cumulate energy balance was less negative from day 11-30 in period B than in A (-884 vs -1566 kcal; p = 0.033). There was a one-day reduction in the median duration of fasting in period B (p < 0.0001). Overall compliance with nutrition protocol improved in period B with an earlier first indirect calorimetry (p = 0.003) and prealbumin measurement (p < 0.001), the latter increasing significantly more during ICU stay.

CONCLUSION

Organizational changes that allowed an early identification of patients at nutritional risk, an increased targeted dieticians intervention and a better inter-disciplinary work was associated with a reduction in undue fasting, and significantly improved energy balances.

Damage-Associated Molecular Patterns As Double-Edged Swords in Sepsis

Significance: Sepsis is defined as a life-threatening organ dysfunction caused by dysregulated host response to infection. This leads to an uncontrolled inflammatory response at the onset of infection, followed by immunosuppression. The development of a specific treatment modality for sepsis is still challenging, reflecting our inadequate understanding of its pathophysiology. Understanding the mechanism and transition of the early hyperinflammation to late stage of immunosuppression in sepsis is critical for developing sepsis therapeutics. Recent Advances: Damage-associated molecular patterns (DAMPs) are intracellular molecules and released upon tissue injury and cell death in sepsis. DAMPs are recognized by pattern recognition receptors to initiate inflammatory cascades. DAMPs not only elicit an inflammatory response but also they subsequently induce immunosuppression, both are equally important for exacerbating sepsis. Recent advances on a new DAMP, extracellular cold-inducible RNA-binding protein for fueling inflammation and immunosuppression in sepsis, have added a new avenue into the dual functions of DAMPs in sepsis. Critical Issues: The molecular modification of DAMPs and their binding to pattern recognition receptors transit dynamically by the cellular environment in pathophysiologic conditions. Correlation between the dynamic changes of the impacts of DAMPs and the clinical outcomes in sepsis still lacks adequate understanding. Here, we focus on the impacts of DAMPs that cause inflammation as well as induce immunosuppression in sepsis. We further discuss the therapeutic potential by targeting DAMPs to attenuate inflammation and immunosuppression for mitigating sepsis. Future Directions: Uncovering pathways of the transition from inflammation to immunosuppression of DAMPs is a potential therapeutic avenue for mitigating sepsis.

Impact of Nutritional Assessment on the Clinical Outcomes of Patients with Non-albicans Candidemia: A Multicenter Study

Several studies have demonstrated that malnutrition is a negative prognostic factor for clinical outcomes. However, there is limited evidence for the effect of malnutrition on clinical outcomes in patients with candidemia. We investigated the relationship between malnutrition and all-cause 28-day mortality among patients with non-albicans candidemia. Between July 2011 and June 2014, all adult patients with non-albicans candidemia, including C. tropicalis, C. glabrata, C. parapsilosis and so on, were enrolled. The Malnutrition Universal Screening Tool (MUST) scores were used to determine the patients' nutritional status before the onset of candidemia. A total of 378 patients were enrolled; 43.4% developed septic shock and 57.1% had a high risk of malnutrition (MUST ≥ 2). The all-cause 28-day mortality rate was 40.7%. The Cox proportional hazards model revealed that C. tropicalis (HR, 2.01; 95% CI, 1.24-3.26; p = 0.005), Charlson comorbidity index (HR, 1.10; 95% CI, 1.03-1.18; p = 0.007), Foley catheter use (HR, 1.68; 95% CI, 1.21-1.35; p = 0.002), concomitant bacterial infections (HR, 1.55; 95% CI, 1.11-2.17; p = 0.010), low platelet count (HR, 3.81; 95% CI, 2.45-5.91; p < 0.001), not receiving antifungals initially (HR, 4.73; 95% CI, 3.07-7.29; p < 0.001), and MUST ≥ 2 (HR, 1.54; 95% CI, 1.09-2.17; p = 0.014) were independently associated with all-cause 28-day mortality. A simple screening tool for nutritional assessment should be used for patients with non-albicans candidemia to detect early clinical deterioration, and a tailored nutritional care plan should be established for malnourished individuals, to improve their clinical outcomes.

Immune Intervention in Sepsis

Sepsis is a host immune disorder induced by infection. It can lead to multiple organ dysfunction syndrome (MODS), which has high morbidity and mortality. There has been great progress in the clinical diagnosis and treatment of sepsis, such as improvements in pathogen detection technology, innovations regarding anti-infection drugs, and the development of organ function support. Abnormal immune responses triggered by pathogens, ranging from excessive inflammation to immunosuppression, are recognized to be an important cause of the high mortality rate. However, no drugs have been approved specifically for treating sepsis. Here, we review the recent research progress on immune responses in sepsis to provide a theoretical basis for the treatment of sepsis. Constructing and optimizing a dynamic immune system treatment regimen based on anti-infection treatment, fluid replacement, organ function support, and timely use of immunomodulatory interventions may improve the prognosis of sepsis patients.

Immunological Endotyping of Chronic Critical Illness After Severe Sepsis

Improved management of severe sepsis has been one of the major health care accomplishments of the last two decades. Due to enhanced recognition and improved management of severe sepsis, in-hospital mortality has been reduced by up to 40%. With that good news, a new syndrome has unfortunately replaced in-hospital multi-organ failure and death. This syndrome of chronic critical illness (CCI) includes sepsis patients who survive the early "cytokine or genomic storm," but fail to fully recover, and progress into a persistent state of manageable organ injury requiring prolonged intensive care. These patients are commonly discharged to long-term care facilities where sepsis recidivism is high. As many as 33% of sepsis survivors develop CCI. CCI is the result, at least in part, of a maladaptive host response to chronic pattern-recognition receptor (PRR)-mediated processes. This maladaptive response results in dysregulated myelopoiesis, chronic inflammation, T-cell atrophy, T-cell exhaustion, and the expansion of suppressor cell functions. We have defined this panoply of host responses as a persistent inflammatory, immune suppressive and protein catabolic syndrome (PICS). Why is this important? We propose that PICS in survivors of critical illness is its own common, unique immunological endotype driven by the constant release of organ injury-associated, endogenous alarmins, and microbial products from secondary infections. While this syndrome can develop as a result of a diverse set of pathologies, it represents a shared outcome with a unique underlying pathobiological mechanism. Despite being a common outcome, there are no therapeutic interventions other than supportive therapies for this common disorder. Only through an improved understanding of the immunological endotype of PICS can rational therapeutic interventions be designed.

Severe Traumatic Brain Injury (TBI) Modulates the Kinetic Profile of the Inflammatory Response of Markers for Neuronal Damage

The inflammatory response plays an important role in the pathophysiology of multiple injuries. This study examines the effects of severe trauma and inflammatory response on markers of neuronal damage. A retrospective analysis of prospectively collected data in 445 trauma patients (Injury Severity Score (ISS) ≥ 16) is provided. Levels of neuronal biomarkers (calcium-binding Protein B (S100b), Enolase2 (NSE), glial fibrillary acidic protein (GFAP)) and Interleukins (IL-6, IL-10) in severely injured patients (with polytrauma (PT)) without traumatic brain injury (TBI) or with severe TBI (PT+TBI) and patients with isolated TBI (isTBI) were measured upon arrival until day 5. S100b, NSE, GFAP levels showed a time-dependent decrease in all cohorts. Their expression was higher after multiple injuries (p = 0.038) comparing isTBI. Positive correlation of marker level after concomitant TBI and isTBI (p = 0.001) was noted, while marker expression after PT appears to be independent. Highest levels of IL-6 and -10 were associated to PT und lowest to isTBI (p < 0.001). In all groups pro-inflammatory response (IL-6/-10 ratio) peaked on day 2 and at a lower level on day 4. Severe TBI modulates kinetic profile of inflammatory response by reducing interleukin expression following trauma. Potential markers for neuronal damage have a limited diagnostic value after severe trauma because undifferentiated increase.

Multiple organ dysfunction after trauma

Background

The nature of multiple organ dysfunction syndrome (MODS) after traumatic injury is evolving as resuscitation practices advance and more patients survive their injuries to reach critical care. The aim of this study was to characterize contemporary MODS subtypes in trauma critical care at a population level.

Methods

Adult patients admitted to major trauma centre critical care units were enrolled in this 4‐week point‐prevalence study. MODS was defined by a daily total Sequential Organ Failure Assessment (SOFA) score of more than 5. Hierarchical clustering of SOFA scores over time was used to identify MODS subtypes.

Results

Some 440 patients were enrolled, of whom 245 (55·7 per cent) developed MODS. MODS carried a high mortality rate (22·0 per cent versus 0·5 per cent in those without MODS; P < 0·001) and 24·0 per cent of deaths occurred within the first 48 h after injury. Three patterns of MODS were identified, all present on admission. Cluster 1 MODS resolved early with a median time to recovery of 4 days and a mortality rate of 14·4 per cent. Cluster 2 had a delayed recovery (median 13 days) and a mortality rate of 35 per cent. Cluster 3 had a prolonged recovery (median 25 days) and high associated mortality rate of 46 per cent. Multivariable analysis revealed distinct clinical associations for each form of MODS; 24‐hour crystalloid administration was associated strongly with cluster 1 (P = 0·009), traumatic brain injury with cluster 2 (P = 0·002) and admission shock severity with cluster 3 (P = 0·003).

Conclusion

Contemporary MODS has at least three distinct types based on patterns of severity and recovery. Further characterization of MODS subtypes and their underlying pathophysiology may lead to future opportunities for early stratification and targeted interventions.

Consumptive coagulopathy is associated with organ dysfunction during PICS

Patients who survive the acute phase of sepsis can progress to persistent inflammation, immunosuppression, and catabolism syndrome (PICS). Although sepsis is characterized by early hypercoagulability and delayed hypocoagulability, coagulopathy during chronic critical illness is not fully understood. The objective of this study was to determine whether sepsis-induced PICS is associated with coagulation abnormalities. Using our previously described murine PICS model, outbred mice underwent cecal ligation and puncture, and coagulability was characterized after 8 days. We found that during PICS the spleen became markedly enlarged with increased splenocytes and splenic megakaryocytes without a concomitant increase in circulating platelets. Microscopy revealed a nearly sevenfold increase in pulmonary microvascular thrombi in PICS mice, along with significantly decreased pulmonary tidal volumes and inspiratory times and with significantly increased respiratory rates. Thromboelastometry showed that PICS mice had significantly delayed clot initiation time but increased clot firmness. Finally, PICS mice displayed delayed thrombin production and decreased overall thrombin concentrations. All together, these data demonstrate a general dysregulation of coagulation resulting in microthrombus formation and compromised lung function. On the basis of these findings, we propose that consumptive coagulopathy constitutes another cardinal feature of PICS and may contribute to the ongoing tissue damage and multiple organ failure that can occur in chronic critical illness.

Myeloid-Derived Suppressor Cells in Sepsis

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells characterized by their immunosuppressive functions. MDSCs expand during chronic and acute inflammatory conditions, the best described being cancer. Recent studies uncovered an important role of MDSCs in the pathogenesis of infectious diseases along with sepsis. Here we discuss the mechanisms underlying the expansion and immunosuppressive functions of MDSCs, and the results of preclinical and clinical studies linking MDSCs to sepsis pathogenesis. Strikingly, all clinical studies to date suggest that high proportions of blood MDSCs are associated with clinical worsening, the incidence of nosocomial infections and/or mortality. Hence, MDSCs are attractive biomarkers and therapeutic targets for sepsis, especially because these cells are barely detectable in healthy subjects. Blocking MDSC-mediated immunosuppression and trafficking or depleting MDSCs might all improve sepsis outcome. While some key aspects of MDSCs biology need in depth investigations, exploring these avenues may participate to pave the way toward the implementation of personalized medicine and precision immunotherapy for patients suffering from sepsis.

Spontaneous pneumococcal peritonitis diagnosed by qPCR

Spontaneous bacterial peritonitis is an uncommon manifestation of invasive pneumococcal disease and frequently occurs when an underlying hepatic disease is present. Bacterial identification through culture can be particularly challenging in patients with prior or concurrent antimicrobial use. DNA amplification detects very few copies of target DNA under ideal conditions in CSF or pleural effusion and, therefore, can be useful in selected infections. A culture-negative spontaneous pneumococcal peritonitis without preexisting peritoneal disease diagnosed by qPCR is herein described.

The Lifetime Effects of Injury: Postintensive Care Syndrome and Posttraumatic Stress Disorder

Postintensive care syndrome (PICS) is a heterogeneous syndrome marked by physical, cognitive, and mental health impairments experienced by critical care survivors. It is a syndrome that bears significant human and health care costs. Additional research is needed to identify risk factors and diagnostic, preventative, and treatment strategies for PICS. Trauma intensive care unit patients are particularly vulnerable to posttraumatic stress disorder, which shares some of the adverse long-term consequences of PICS and also requires additional research into effective preventative and management strategies.

Innate Immunity in the Persistent Inflammation, Immunosuppression, and Catabolism Syndrome and Its Implications for Therapy

Clinical and technological advances promoting early hemorrhage control and physiologic resuscitation as well as early diagnosis and optimal treatment of sepsis have significantly decreased in-hospital mortality for many critically ill patient populations. However, a substantial proportion of severe trauma and sepsis survivors will develop protracted organ dysfunction termed chronic critical illness (CCI), defined as ≥14 days requiring intensive care unit (ICU) resources with ongoing organ dysfunction. A subset of CCI patients will develop the persistent inflammation, immunosuppression, and catabolism syndrome (PICS), and these individuals are predisposed to a poor quality of life and indolent death. We propose that CCI and PICS after trauma or sepsis are the result of an inappropriate bone marrow response characterized by the generation of dysfunctional myeloid populations at the expense of lympho- and erythropoiesis. This review describes similarities among CCI/PICS phenotypes in sepsis, cancer, and aging and reviews the role of aberrant myelopoiesis in the pathophysiology of CCI and PICS. In addition, we characterize pathogen recognition, the interface between innate and adaptive immune systems, and therapeutic approaches including immune modulators, gut microbiota support, and nutritional and exercise therapy. Finally, we discuss the future of diagnostic and prognostic approaches guided by machine and deep-learning models trained and validated on big data to identify patients for whom these approaches will yield the greatest benefits. A deeper understanding of the pathophysiology of CCI and PICS and continued investigation into novel therapies harbor the potential to improve the current dismal long-term outcomes for critically ill post-injury and post-infection patients.

Advances in the understanding and treatment of sepsis-induced immunosuppression

Sepsis is defined as a life-threatening organ dysfunction that is caused by a dysregulated host response to infection. Sepsis can induce acute kidney injury and multiple organ failures and represents the most common cause of death in the intensive care unit. Sepsis initiates a complex immune response that varies over time, with the concomitant occurrence of both pro-inflammatory and anti-inflammatory mechanisms. As a result, most patients with sepsis rapidly display signs of profound immunosuppression, which is associated with deleterious consequences. Scientific advances have highlighted the role of metabolic failure, epigenetic reprogramming, myeloid-derived suppressor cells, immature suppressive neutrophils and immune alterations in primary lymphoid organs (the thymus and bone marrow) in sepsis. An improved understanding of the mechanisms underlying this immunosuppression as well as of the similarities between sepsis-induced immunosuppression and immune defects in cancer or immunosenescence has led to novel therapeutic strategies aimed at stimulating immune function in patients with sepsis. Trials assessing the therapeutic benefit of IL-7, granulocyte-macrophage colony-stimulating factor (GM-CSF) and antibodies against programmed cell death protein 1 (PD1) and programmed cell death 1 ligand 1 (PDL1) for the treatment of sepsis are in progress. The reappraisal of sepsis pathophysiology has also resulted in a novel approach to the design of clinical trials evaluating sepsis treatments, based on an evaluation of the immune status and biomarker-based stratification of patients.