Mechanisms of organ dysfunction in critical illness: report from a Round Table Conference held in Brussels

Neuromuscular Disorders Associated With COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has had an enormous impact on practically every aspect of daily life, and those with neuromuscular disorders have certainly not been spared. The effects of COVID-19 infection are far-reaching, going well beyond respiratory symptoms alone. From simple myalgias to debilitating critical illness neuromyopathies, we continue to learn and catalog the diverse pathologies presented by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as it relates to the neuromuscular system. Complications have been documented both as a direct result of primary infection but also in those with pre-existing neuromuscular disorders from myasthenia gravis to devastating critical illness neuromyopathies. In this review, we will discuss the relationship between COVID-19 infection and critical illness neuromyopathy, peripheral nerve palsies, myalgias, positional compressive neuropathy, myasthenia gravis, and Guillain-Barré syndrome.

Roles of neutrophil reactive oxygen species (ROS) generation in organ function impairment in sepsis

Sepsis is a condition of severe organ failure caused by the maladaptive response of the host to an infection. It is a severe complication affecting critically ill patients, which can progress to severe sepsis, septic shock, and ultimately death. As a vital part of the human innate immune system, neutrophils are essential in resisting pathogen invasion, infection, and immune surveillance. Neutrophil-produced reactive oxygen species (ROS) play a pivotal role in organ dysfunction related to sepsis. In recent years, ROS have received a lot of attention as a major cause of sepsis, which can progress to severe sepsis and septic shock. This paper reviews the existing knowledge on the production mechanism of neutrophil ROS in human organ function impairment because of sepsis.

Increased intestinal permeability exacerbates sepsis through reduced hepatic SCD-1 activity and dysregulated iron recycling

Inflammatory bowel disease is associated with changes in the mucosal barrier, increased intestinal permeability, and increased risk of infections and sepsis, but the underlying mechanisms are incompletely understood. Here, we show how continuous translocation of gut microbial components affects iron homeostasis and facilitates susceptibility to inflammation-associated sepsis. A sub-lethal dose of lipopolysaccharide results in higher mortality in Mucin 2 deficient (Muc2^-/-) mice, and is associated with elevated circulatory iron load and increased bacterial translocation. Translocation of gut microbial components attenuates hepatic stearoyl CoA desaturase-1 activity, a key enzyme in hepatic de novo lipogenesis. The resulting reduction of hepatic saturated and unsaturated fatty acid levels compromises plasma membrane fluidity of red blood cells, thereby significantly reducing their life span. Inflammation in Muc2^-/- mice alters erythrophagocytosis efficiency of splenic macrophages, resulting in an iron-rich milieu that promotes bacterial growth. Our study thus shows that increased intestinal permeability triggers a cascade of events resulting in increased bacterial growth and risk of sepsis.

Pathophysiology of Acute Illness and Injury

The pathophysiology of acute illness and injury recognizes three main effectors: infection, trauma, and ischemia-reperfusion injury. Each of them can act by itself or in combination with the other two in developing a systemic inflammatory reaction syndrome (SIRS) that is a generalized reaction to the morbid event. The time course of SIRS is variable and influenced by the number and severity of subsequent insults (e.g., reparative surgery, acquired hospital infections). It occurs simultaneously with a complex of counter-regulatory mechanisms (compensatory anti-inflammatory response syndrome, CARS) that limit the aggressive effects of SIRS. In adjunct, a progressive dysfunction of the acquired (lymphocytes) immune system develops with increased risk for immunoparalysis and associated infectious complications. Both humoral and cellular effectors participate to the development of SIRS and CARS. The most important humoral mediators are pro-inflammatory (IL-1β, IL-6, IL-8, IL-12) and anti-inflammatory (IL-4, IL-10) cytokines and chemokines, complement, leukotrienes, and PAF. Effector cells include neutrophils, monocytes, macrophages, lymphocytes, and endothelial cells. The endothelium is a key factor for production of remote organ damage as it exerts potent chemo-attracting effects on inflammatory cells, allows for leukocyte trafficking into tissues and organs, and promotes further inflammation by cytokines release. Moreover, the loss of vasoregulatory properties and the increased permeability contribute to the development of hypotension and tissue edema. Finally, the disseminated activation of the coagulation cascade causes the widespread deposition of microthrombi with resulting maldistribution of capillary blood flow and ultimately hypoxic cellular damage. This mechanism together with increased vascular permeability and vasodilation is responsible for the development of the multiple organ dysfunction syndrome (MODS).

Intensive Care Management of the Neuromuscular Patient

Neuromuscular emergencies are a distinct group of acute neurological diseases with distinct characteristic presentations. Patients who suffer from this group of diseases are at immediate risk of losing protection of their native airway as well as aspirating orogastric contents. This is secondary to weakness of the muscles of the oropharynx and respiratory muscles. Although some neuromuscular emergencies such as myasthenia gravis or Guillain-Barré syndrome are well understood, others such as critical illness myopathy and neuropathy are less well characterized. In this chapter, we have discussed the pathophysiology, diagnostic evaluation, and management options in patients who are admitted to the intensive care unit. We have also emphasized the importance of a thorough understanding of the use of pharmacological anesthetic agents in this patient population.

Exploring Epidemiological Aspects, Distribution of WHO Maternal Near Miss Criteria, and Organ Dysfunction Defined by SOFA in Cases of Severe Maternal Outcome Admitted to Obstetric ICU: A Cross-Sectional Study

Objective

To explore the epidemiological aspects, to describe the frequency and distribution of WHO maternal near miss (MNM) criteria and the presence of organ dysfunction and failure measured by the maximum SOFA (Sequential Organ Failure Assessment) score (SOFA max) in cases of severe maternal outcome (SMO).

Methods

In an observational cross-sectional study performed between January 2013 and December 2015, 279 pregnant or postpartum women were admitted to an obstetric ICU (intensive care unit) in Brazil. MNM, maternal death (grouped as SMO), and potentially life-threatening conditions (PLTC) were defined according to WHO criteria. For categorical variables, a descriptive analysis was carried out. Frequency and distribution of WHO criteria, organ dysfunction, or failure defined by SOFA max were performed.

Results

WHO criteria identified 65 SMO and 214 PLTC. Management criteria were present in 58/65 (89.2%) while 61/65 (93.8%) of SMO cases had dysfunction or failure by SOFA.

Conclusions

The systematic evaluation of the organic function by SOFA max score identified the presence of organic dysfunction or failure in almost all SMO cases. Management criteria were present in all MD cases. Our results indicate the need for new studies evaluating the parameterization of the WHO laboratory criteria for values compatible with the definition of organic dysfunction by the SOFA to identify MNM.

Review of Critical Illness Myopathy and Neuropathy

Critical illness myopathy (CIM) and neuropathy are underdiagnosed conditions within the intensive care setting and contribute to prolonged mechanical ventilation and ventilator wean failure and ultimately lead to significant morbidity and mortality. These conditions are often further subdivided into CIM, critical illness polyneuropathy (CIP), or the combination-critical illness polyneuromyopathy (CIPNM). In this review, we discuss the epidemiology and pathophysiology of CIM, CIP, and CIPNM, along with diagnostic considerations such as detailed clinical examination, electrophysiological studies, and histopathological review of muscle biopsy specimens. We also review current available treatments and prognosis. Increased awareness and early recognition of CIM, CIP, and CIPNM in the intensive care unit setting may lead to earlier treatments and rehabilitation, improving patient outcomes.

Pain perception in healthy volunteers: effect of repeated exposure to experimental systemic inflammation

We aimed to study the relationship between pain perception and cytokine release during systemic inflammation. We present a randomized crossover trial in healthy volunteers (n = 17) in 37 individual trials. Systemic inflammation was induced by an i.v. bolus of Escherichia coli LPS (2 ng/kg) on two separate trial days, with or without a nicotine patch applied 10 h previously. Pain perception at baseline, and 2 and 6 h after LPS was assessed by pressure algometry and tonic heat stimulation at an increasing temperature (45-48℃) during both trials. Compared with baseline, pain pressure threshold was reduced 2 and 6 h after LPS, while heat pain perception was accentuated at all testing temperatures after 2 but not 6 h. The magnitude of changes in pain perception did not correlate to cytokine release. No effect of transdermal nicotine or training status was observed. In conclusion, LPS administration in healthy human volunteers leads to reduction in pain pressure threshold and an increase in pain perception to heat stimuli, supporting a relationship between acute systemic inflammation and pain perception.

Paradoxical Roles of the Neutrophil in Sepsis: Protective and Deleterious

Sepsis, an overwhelming inflammatory response syndrome secondary to infection, is one of the costliest and deadliest medical conditions worldwide. Neutrophils are classically considered to be essential players in the host defense against invading pathogens. However, several investigations have shown that impairment of neutrophil migration to the site of infection, also referred to as neutrophil paralysis, occurs during severe sepsis, resulting in an inability of the host to contain and eliminate the infection. On the other hand, the neutrophil antibacterial arsenal contributes to tissue damage and the development of organ dysfunction during sepsis. In this review, we provide an overview of the main events in which neutrophils play a beneficial or deleterious role in the outcome of sepsis.

[Cerebral dysfunction as a component of multiple organ failure in surgical patients (lecture)]

Development of delirium in critically ill patients is considered complication of basic disease which increases patients' hospital stay, mortality rate and the cost of treatment. Despite wide prevalence delirium often remains undiagnosed by physicians in ICU. Routine use of screening scales permits to diagnose delirium timely. Multicomponent preventive strategy with intermittent sedation and dexmedetomidine improves the results of treatment.

Nociceptin system as a target in sepsis?

The nociceptin system comprises the nociceptin receptor (NOP) and the ligand nociceptin/orphanin FQ (N/OFQ) that binds to the receptor. The archetypal role of the system is in pain processing but the NOP receptor is also expressed on immune cells. Activation of the NOP receptor is known to modulate inflammatory responses, such as mast-cell degranulation, neutrophil rolling, vasodilation, increased vascular permeability, adhesion molecule regulation and leucocyte recruitment. As there is a loss of regulation of inflammatory responses during sepsis, the nociceptin system could be a target for therapies aimed at modulating sepsis. This review details the known effects of NOP activation on leucocytes and the vascular endothelium and discusses the most recent human and animal data on the role of the nociceptin system in sepsis.

Relationship between acid-base status and inflammation in the critically ill

Introduction

There is a complex interplay between changes in acid–base components and inflammation. This manuscript aims to explore associations between plasma cytokines and chemokines and acid–base status on admission to intensive care.

Methods

We conducted a prospective cohort study in a 13-bed ICU in a tertiary-care center in Brazil. 87 unselected patients admitted to the ICU during a 2-year period were included. We measured multiple inflammatory mediators in plasma using multiplex assays and evaluated the association between mediator concentrations and acid–base variables using a variety of statistical modeling approaches, including generalized linear models, multiadaptive regression splines and principal component analysis.

Results

We found a positive association between strong ion gap (SIG) and plasma concentrations of interleukin (IL)6, 8, 10 and tumor necrosis factor (TNF); whereas albumin was negatively associated with IL6, IL7, IL8, IL10, TNF and interferon (IFN)α. Apparent strong ion difference (SID_a) was negatively associated with IL10 and IL17. A principal component analysis including SAPS 3 indicated that the association between acid–base components and inflammatory status was largely independent of illness severity, with both increased SIG and decreased SID_a (both drivers of acidosis) associated with increased inflammation.

Conclusion

Acid–base variables (especially increased SIG, decreased albumin and decreased SID_a) on admission to ICU are associated with immunological activation. These findings should encourage new research into the effects of acid–base status on inflammation.

Immunoinflammatory response in critically ill patients: severe sepsis and/or trauma

Immunoinflammatory response in critically ill patients is very complex. This review explores some of the new elements of immunoinflammatory response in severe sepsis, tumor necrosis factor-alpha in severe acute pancreatitis as a clinical example of immune response in sepsis, immune response in severe trauma with or without secondary sepsis, and genetic aspects of host immuno-inflammatory response to various insults in critically ill patients.

Immune response in severe infection: could life-saving drugs be potentially harmful?

Critically ill patients suffer a high rate of nosocomial infection with secondary sepsis being a common cause of death. Usage of antibiotics and catecholamines is often necessary, but it can compromise complex immune response to infection. This review explores influence of these life-saving drugs on host immune response to severe infection.

Immunosuppression in sepsis: a novel understanding of the disorder and a new therapeutic approach

Failures of highly touted trials have caused experts to call for re-evaluation of the current approach toward sepsis. New research has revealed key pathogenic mechanisms; autopsy results have shown that most patients admitted to intensive care units for treatment of sepsis had unresolved septic foci at post mortem, suggesting that patients were unable to eradicate invading pathogens and were more susceptible to nosocomial organisms, or both. These results suggest that therapies that improve host immunity might increase survival. Additional work showed that cytokine production by splenocytes taken post mortem from patients who died of sepsis is profoundly suppressed, possibly because of so-called T-cell exhaustion-a newly recognised immunosuppressive mechanism that occurs with chronic antigenic stimulation. Results from two clinical trials of biomarker-guided therapeutic drugs that boosted immunity showed promising findings in sepsis. Collectively, these studies emphasise the degree of immunosuppression that occurs in sepsis, and explain why many previous sepsis trials which were directed at blocking inflammatory mediators or pathogen recognition signalling pathways failed. Finally, highly encouraging results from use of the new immunomodulatory molecules interleukin 7 and anti-programmed cell death 1 in infectious disease point the way for possible use in sepsis. We hypothesise that immunoadjuvant therapy represents the next major advance in sepsis.

Insufficient autophagy contributes to mitochondrial dysfunction, organ failure, and adverse outcome in an animal model of critical illness

OBJECTIVE

Increasing evidence implicates mitochondrial dysfunction as an early, important event in the pathogenesis of critical illness-induced multiple organ failure. We previously demonstrated that prevention of hyperglycemia limits damage to mitochondria in vital organs, thereby reducing morbidity and mortality. We now hypothesize that inadequate activation of mitochondrial repair processes (clearance of damaged mitochondria by autophagy, mitochondrial fusion/fission, and biogenesis) may contribute to accumulation of mitochondrial damage, persistence of organ failure, and adverse outcome of critical illness.

DESIGN

Prospective, randomized studies in a critically ill rabbit model.

SETTING

University laboratory.

SUBJECTS

Three-month-old male rabbits.

INTERVENTIONS

We studied whether vital organ mitochondrial repair pathways are differentially affected in surviving and nonsurviving hyperglycemic critically ill animals in relation to mitochondrial and organ damage. Next, we investigated the impact of preventing hyperglycemia over time and of administering rapamycin as an autophagy activator.

MEASUREMENTS AND MAIN RESULTS

In both liver and kidney of hyperglycemic critically ill rabbits, we observed signs of insufficient autophagy, including accumulation of p62 and a concomitant decrease in the microtubule-associated protein light-chain-3-II/microtubule-associated protein light-chain-3-I ratio. The phenotype of insufficient autophagy was more pronounced in nonsurviving than in surviving animals. Molecular markers of insufficient autophagy correlated with impaired mitochondrial function and more severe organ damage. In contrast, key players in mitochondrial fusion/fission or biogenesis were not significantly different regarding survival status. Therefore, we focused on autophagy to study the impact of preventing hyperglycemia. Both after 3 and 7 days of illness, autophagy was better preserved in normoglycemic than in hyperglycemic rabbits, which correlated with improved mitochondrial function and less organ damage. Stimulation of autophagy in kidney with rapamycin correlated with protection of renal function.

CONCLUSIONS

Our findings put forward insufficient autophagy as a potentially important contributor to mitochondrial and organ damage in critical illness and open perspectives for therapies that activate autophagy during critical illness.

Altered serum stress neuropeptide levels in critically ill individuals and associations with lymphocyte populations

OBJECTIVE

Potential physiological correlates of stress and the role of stress neuropeptides, other than those of the hypothalamic-pituitary-adrenal axis, in critical illness have not been addressed. We investigated: (a) serum levels of stress neuropeptides (ACTH, substance P (SP), neuropeptide Y (NPY), cortisol, prolactin) in critically ill individuals compared to matched controls, (b) associations with lymphocyte counts, (c) associations among stress neuropeptide levels, and (d) associations with perceived intensity of stress, critical illness severity and survival.

METHODS

Correlational design with repeated measures. Thirty-six critically ill patients were followed up for 14 days compared to 36 healthy matched controls. Stress was assessed by the ICUESS scale. Correlations, cross-sectional comparisons and multiple regression models were pursued.

RESULTS

For the first time, we report lower SP (Difference of means (DM) = 2928-3286 ng/ml, p < 0.001) and NPY (DM = 0.77-0.83 ng/ml, p < 0.0001) levels in critically ill individuals compared to controls. Cortisol levels were higher (DM = 140-173 ng/ml, p<0.0001) and lymphocyte population counts (p < 0.002) were lower in patients throughout the study. NPY levels associated with lymphocyte (r = 0.411-0.664, p < 0.04), T-lymphocyte (r = 0.403-0.781, p< 0.05), T-helper (r = 0.492-0.690, p < 0.03) and T-cytotoxic cell populations (r = 0.39-0.740, p < 0.03). On day 1, cortisol levels exhibited associations with lymphocyte (r = -0.452, p = 0.01), T-cell (r = -0.446, p = 0.02), T-helper (r = -0.428, p = 0.026) and T-cytotoxic cells ( r = -0.426, p = 0.027). ACTH levels associated with NK cell counts (r = 0.326-0.441, p < 0.05). Associations among stress neuropeptides levels were observed throughout (p < 0.05). ACTH levels associated with disease severity (r = 0.340-0.387, p < 0.005). A trend for an association between ACTH levels and intensity of stress was noted (r = 0.340, p = 0.057).

CONCLUSION

The significantly lowered NPY and SP levels and the associations with cortisol, ACTH and lymphocytes suggest that the role of these peptides in critical illness merit further investigation. Future studies need to address associations between these neuropeptides and functional immune cell responses and inflammatory markers in critical illness.

Mechanisms of cardiac and renal dysfunction in patients dying of sepsis

RATIONALE

The mechanistic basis for cardiac and renal dysfunction in sepsis is unknown. In particular, the degree and type of cell death is undefined.

OBJECTIVES

To evaluate the degree of sepsis-induced cardiomyocyte and renal tubular cell injury and death.

METHODS

Light and electron microscopy and immunohistochemical staining for markers of cellular injury and stress, including connexin-43 and kidney-injury-molecule-1 (Kim-1), were used in this study.

MEASUREMENTS AND MAIN RESULTS

Rapid postmortem cardiac and renal harvest was performed in 44 septic patients. Control hearts were obtained from 12 transplant and 13 brain-dead patients. Control kidneys were obtained from 20 trauma patients and eight patients with cancer. Immunohistochemistry demonstrated low levels of apoptotic cardiomyocytes (<1-2 cells per thousand) in septic and control subjects and revealed redistribution of connexin-43 to lateral membranes in sepsis (P < 0.020). Electron microscopy showed hydropic mitochondria only in septic specimens, whereas mitochondrial membrane injury and autophagolysosomes were present equally in control and septic specimens. Control kidneys appeared relatively normal by light microscopy; 3 of 20 specimens showed focal injury in approximately 1% of renal cortical tubules. Conversely, focal acute tubular injury was present in 78% of septic kidneys, occurring in 10.3 ± 9.5% and 32.3 ± 17.8% of corticomedullary-junction tubules by conventional light microscopy and Kim-1 immunostains, respectively (P < 0.01). Electron microscopy revealed increased tubular injury in sepsis, including hydropic mitochondria and increased autophagosomes.

CONCLUSIONS

Cell death is rare in sepsis-induced cardiac dysfunction, but cardiomyocyte injury occurs. Renal tubular injury is common in sepsis but presents focally; most renal tubular cells appear normal. The degree of cell injury and death does not account for severity of sepsis-induced organ dysfunction.

Interpersonal touch: physiological effects in critical care

INTRODUCTION

Nurses use several forms of touch in patient encounters. Interpersonal touch elicits specific physiological and psychological responses, including neuroendocrine effects and reduction of stress. Critical illness is a state of excessive physiological and psychological stress.

AIMS

To critically review evidence on the effect of touch on physiological outcomes in critically ill individuals. Results of intervention studies in adult critical care settings were reviewed along with supportive evidence from studies in other populations.

METHODS

Critical literature review based on studies published in MEDLINE, PubMed, Cinahl, Embase, and Cochrane databases.

RESULTS

Eleven studies were reviewed. Significant effects of interpersonal touch included lower systolic and diastolic blood pressure and respiratory rate, improved sleep, and decreased pain. Almost no results were replicated owing to discrepancies among studies. Although the effect of touch on cardiovascular autonomic status appears considerable, several confounders must be considered. In noncritically ill populations, replicable findings included increased urinary dopamine and serotonin, natural killer cytotoxic activity, and salivary chromogranin. Effects on plasma cortisol and immune cells were variable. Effects appear to vary according to amount of pressure, body site, duration, and timing: Moderate pressure touch may elicit a parasympathetic response in contrast to light touch, which may elicit a sympathetic response. Moreover, touch effects may be mediated by the density of autonomic innervation received by the body areas involved and repetition of sessions.

CONCLUSION

The physiological pathway mediating the effects of touch is unclear. Although no concrete conclusions can be drawn, research evidence suggests that touch interventions may benefit critically ill individuals.

Systems biology of antioxidants

Understanding the role of oxidative injury will allow for therapy with agents that scavenge ROS (reactive oxygen species) and antioxidants in the management of several diseases related to free radical damage. The majority of free radicals are generated by mitochondria as a consequence of the mitochondrial cycle, whereas free radical accumulation is limited by the action of a variety of antioxidant processes that reside in every cell. In the present review, we provide an overview of the mitochondrial generation of ROS and discuss the role of ROS in the regulation of endothelial and adipocyte function. Moreover, we also discuss recent findings on the role of ROS in sepsis, cerebral ataxia and stroke. These results provide avenues for the therapeutic potential of antioxidants in a variety of diseases.

Delirium: an emerging frontier in the management of critically ill children

Delirium is a syndrome of acute brain dysfunction that commonly occurs in critically ill adults and most certainly is prevalent in critically ill children all over the world. The dearth of information about the incidence, prevalence, and severity of pediatric delirium stems from the simple fact that there have not been well-validated instruments for routine delirium diagnosis at the bedside. This article reviewed the emerging solutions to this problem, including description of a new pediatric tool called the pCAM-ICU. In adults, delirium is responsible for significant increases in both morbidity and mortality in critically ill patients. The advent of new tools for use in critically ill children will allow the epidemiology of this form of acute brain dysfunction to be studied adequately, will allow clinical management algorithms to be developed and implemented following testing, and will present the necessary incorporation of delirium as an outcome measure for future clinical trials in pediatric critical care medicine.

Critical illness polyneuropathy and myopathy: a major cause of muscle weakness and paralysis

Critical illness polyneuropathy (CIP) and myopathy (CIM) are complications of critical illness that present with muscle weakness and failure to wean from the ventilator. In addition to prolonging mechanical ventilation and hospitalisation, CIP and CIM increase hospital mortality in patients who are critically ill and cause chronic disability in survivors of critical illness. Structural changes associated with CIP and CIM include axonal nerve degeneration, muscle myosin loss, and muscle necrosis. Functional changes can cause electrical inexcitability of nerves and muscles with reversible muscle weakness. Microvascular changes and cytopathic hypoxia might disrupt energy supply and use. An acquired sodium channelopathy causing reduced muscle membrane and nerve excitability is a possible unifying mechanism underlying CIP and CIM. The diagnosis of CIP, CIM, or combined CIP and CIM relies on clinical, electrophysiological, and muscle biopsy investigations. Control of hyperglycaemia might reduce the severity of these complications of critical illness, and early rehabilitation in the intensive care unit might improve the functional recovery and independence of patients.

Procalcitonin and C-reactive protein levels at admission as predictors of duration of acute brain dysfunction in critically ill patients

INTRODUCTION

Non-intensive care unit (ICU) cohorts have shown an association between inflammatory disturbances and delirium, though these relationships have not been studied in critically ill patients. This study sought to investigate the relationship between two inflammatory biomarkers, procalcitonin and C-reactive protein (CRP), and duration of acute brain dysfunction in ventilated patients.

METHODS

Patients enrolled in the Maximizing Efficacy of Targeted Sedation and Reducing Neurological Dysfunction (MENDS) trial were assessed daily for delirium using the Confusion Assessment Method-ICU. Plasma levels of procalcitonin and CRP were obtained within 24 hours of enrollment. Proportional odds logistic regression was used to examine the association between procalcitonin and CRP separately with delirium/coma-free days, adjusting for age, acute physiology score (APS) of the Acute Physiology And Chronic Health Evaluation (APACHE) II, sedation group (dexmedetomidine vs. lorazepam), and sepsis. Secondary analyses examined the association of these markers with other organ dysfunctions and 28-day survival.

RESULTS

Eighty-seven patients were included in this analysis. The median age of the patients was 60 years with APACHE II scores of 28; 68% had sepsis within 48 hours of admission. Higher levels of procalcitonin were associated with fewer delirium/coma-free days [odds ratio (OR), 0.5; 95% confidence interval (CI), 0.3 to 1.0; P = 0.04], whereas higher CRP levels showed trends towards fewer delirium/coma-free days (OR, 0.6; 95% CI, 0.3 to 1.1; P = 0.08). Similar relationships were found regardless of the presence of sepsis. No associations were found between procalcitonin or CRP with 28-day survival (P = 0.40 and 0.16, respectively).

CONCLUSIONS

In our pilot study, high baseline inflammatory biomarkers predicted prolonged periods of acute brain dysfunction, implicating inflammation as an important mechanism in the pathophysiology of delirium and coma during critical illness, irrespective of whether patients had sepsis or not.

Anesthesia aggravates lung damage and precipitates hypotension in endotoxemic sheep

Beneficial anti-inflammatory properties have been ascribed to volatile anesthetics in septic conditions, but no studies have compared anesthesia to the conscious state in a large-animal model. The aim of this study was to investigate the effect of isoflurane anesthesia on cardiovascular and respiratory function, leukocyte activation, and lung damage in a model of endotoxemia in sheep. Conscious (n = 6) and anesthetized (n = 6) sheep were made endotoxemic by continuous infusion of LPS for 48 h. Central hemodynamics were monitored continuously, and blood samples were collected regularly. Activation of leukocytes was assessed by surface expression of CD11b and plasma myeloperoxidase concentration. Lung damage was determined by electron microscopy, cell count in bronchoalveolar lavage fluid, and analysis of lung vascular permeability. Four additional animals (two conscious and two anesthetized) went through the same protocol but did not receive LPS. LPS infusion induced a hyperdynamic sepsis. The drop in total peripheral resistance was compensated by an increase in heart rate and cardiac output in the conscious group, whereas anesthetized sheep failed to compensate in this way. Endotoxemic isoflurane-anesthetized sheep also showed signs of aggravated lung edema formation and tissue damage together with enhanced neutrophil activation and lung tissue accumulation. Our data suggest that isoflurane in conjunction with mechanical ventilation blunts cardiovascular compensatory mechanisms in sepsis and enhances leukocyte activation, which may contribute to lung edema formation and tissue damage.

Formyl peptide receptor ligands promote wound closure in lung epithelial cells

Mitochondrial antigens released from damaged cells act as "danger signals" capable of promoting innate immune cell migration and activation via formyl peptide receptors (FPRs). Lung epithelial cells are equipped to migrate and mount innate immune responses in the context of acute lung injury. The goal of this study was to determine whether lung epithelial cells express FPRs, which are capable of responding to mitochondrial antigens to promote wound closure and inflammation. Using human Beas2B lung epithelial cells grown to confluency and subjected to linear scratch injury, it was found that mitochondrial antigens enhanced epithelial wound closure, and this phenomenon was inhibited by cyclosporin H, a selective inhibitor of FPR. Although mitochondrial antigens also promoted IL-8 release, this release was not FPR dependent and was unrelated to FPR-induced lung epithelial cell wound closure. The expression of functional FPR was confirmed in Beas2B and primary human tracheobronchial epithelial cells, particularly in lamellipodia at the leading edge of the closing wound. The expression of FPR was increased in response to TNF-α, LPS, scratch injury, and mitochondrial antigen treatment. Considered together, these data confirm that human lung epithelial cells express functional FPRs, which are capable of responding to endogenous mitochondrial danger signals, to promote wound closure.

Delirium: an emerging frontier in the management of critically ill children

The objectives of this article are (1) to introduce pediatric delirium and provide understanding of acute brain dysfunction with its classification and clinical presentations (2) to understand how delirium is diagnosed and discuss current modes of delirium diagnosis in the critically ill adult population and translation to pediatrics (3) to understand the prevalence and prognostic significance of delirium in the adult and pediatric critically ill population (4) to discuss the pathophysiology of delirium as currently understood, and (5) to provide general management guidelines for delirium.

Sepsis induces brain mitochondrial dysfunction

OBJECTIVE

Mitochondrial dysfunctions have been associated with the pathogenesis of sepsis. A systematic survey of mitochondrial function in brain tissues during sepsis is lacking. In the present work, we investigate brain mitochondrial function in a septic mouse model.

DESIGN

Prospective animal study.

SETTING

University research laboratory.

SUBJECTS

Male Swiss mice, aged 6-8 wks.

INTERVENTIONS

Mice were subjected to cecal ligation and perforation (sepsis group) with saline resuscitation or to sham operation (control group).

MEASUREMENTS AND MAIN RESULTS

Oxygen consumption was measured polarographically in an oximeter. Brain homogenates from septic animals presented higher oxygen consumption in the absence of adenosine 5'-diphosphate (state 4) compared with control animals. The increase in state 4 respiration in animals in the cecal ligation and perforation group resulted in a drastic decrease in both respiratory control and adenosine 5'-diphosphate/oxygen ratios, indicating a reduction in the oxidative phosphorylation efficiency. Septic animals presented a significant increase in the recovery time of mitochondrial membrane potential on adenosine 5'-diphosphate addition compared with control animals, suggesting a proton leak through the inner mitochondrial membrane. The septic group presented a general reduction in the content of cytochromes. Moreover, the activity of cytochrome c oxidase was specifically and significantly decreased in the brain during sepsis. Hydrogen peroxide generation by brain mitochondria from septic mice did not respond to substrates of electron transport chain or to adenosine 5'-diphosphate, showing that mitochondrial function may be compromised in a critical level in the brain during sepsis.

CONCLUSIONS

The mitochondrial dysfunctions demonstrated here indicate that uncoupling of oxidative phosphorylation takes place in the brain of septic mice, compromising tissue bioenergetic efficiency.

Delirium in the intensive care unit

Delirium, an acute and fluctuating disturbance of consciousness and cognition, is a common manifestation of acute brain dysfunction in critically ill patients, occurring in up to 80% of the sickest intensive care unit (ICU) populations. Critically ill patients are subject to numerous risk factors for delirium. Some of these, such as exposure to sedative and analgesic medications, may be modified to reduce risk. Although dysfunction of other organ systems continues to receive more clinical attention, delirium is now recognized to be a significant contributor to morbidity and mortality in the ICU, and it is recommended that all ICU patients be monitored using a validated delirium assessment instrument. Patients with delirium have longer hospital stays and lower 6-month survival than do patients without delirium, and preliminary research suggests that delirium may be associated with cognitive impairment that persists months to years after discharge. Little evidence exists regarding the prevention and treatment of delirium in the ICU, but multicomponent interventions reduce the incidence of delirium in non-ICU studies. Strategies for the prevention and treatment of ICU delirium are the subjects of multiple ongoing investigations.

Assessing neurocognitive outcomes after critical illness: are delirium and long-term cognitive impairments related?

PURPOSE OF REVIEW

Critically ill patients have a high risk of developing neurologic dysfunction including delirium and long-term cognitive impairment. In this paper we examine possible relationships between delirium and long-term cognitive impairments and explore this in the context of critical illness.

RECENT FINDINGS

Critical illness and its treatment can lead to neurologic morbidity including neuropathological abnormalities, delirium, and cognitive impairments. The association between delirium and long-term cognitive impairments has been shown in a number of populations. Among intensive care unit cohorts, delirium appears to be one of many possible causes of cognitive impairments and may be a leading modifiable cause. The mechanisms of both delirium and intensive care unit related cognitive impairment remain unclear, although a variety of common mechanisms have been proposed.

SUMMARY

Potential neurologic consequences of critical illness include delirium and long-term cognitive impairments. Defining the extent of their association in intensive care unit cohorts is an important research priority due to the high prevalence of delirium and persistent cognitive impairments in critically ill patients. Future research should focus on strategies for the early identification of delirium and cognitive impairments, elucidating mechanisms of brain injury, and the development and implementation of therapeutic modalities designed to prevent or decrease delirium and cognitive morbidity.

Neutrophils in development of multiple organ failure in sepsis

Multiple organ failure is a major threat to the survival of patients with sepsis and systemic inflammation. In the UK and in the USA, mortality rates are currently comparable with and projected to exceed those from myocardial infarction. The immune system combats microbial infections but, in severe sepsis, its untoward activity seems to contribute to organ dysfunction. In this Review we propose that an inappropriate activation and positioning of neutrophils within the microvasculature contributes to the pathological manifestations of multiple organ failure. We further suggest that targeting neutrophils and their interactions with blood vessel walls could be a worthwhile therapeutic strategy for sepsis.

Sedative and Analgesic Medications: Risk Factors for Delirium and Sleep Disturbances in the Critically Ill

Sedatives and analgesics are routinely used in critically ill patients, although they have the potential for side effects, such as delirium and sleep architecture disruption. Although it should be emphasized that these medications are extremely important in providing patient comfort, health care professionals must also strive to achieve the right balance of sedative and analgesic administration through greater focus on reducing unnecessary or overzealous use. Ongoing clinical trials should help us to understand whether altering the delivery strategy, via daily sedation interruption, or protocolized target-based sedation or changing sedation paradigms to target different central nervous system receptors can affect cognitive outcomes and sleep preservation in our critically ill patients.

Organ dysfunction during sepsis

BACKGROUND

Multiple organ dysfunction syndrome is the commonest reason for sepsis-associated mortality.

DISCUSSION

In the 40 years since it was first described understanding of its pathophysiology has improved, and novel methodologies for monitoring and severity of illness scoring have emerged. These, together with the development of systematic strategies for managing organ dysfunction in sepsis, and potentially effective new therapeutic interventions, should assist in reducing sepsis-associated mortality.

CONCLUSION

These historical developments are discussed, and the reader is directed to these references for further guidance.

Delirium: acute cognitive dysfunction in the critically ill

PURPOSE OF REVIEW

The management of sepsis and the multiple organ dysfunction syndrome has traditionally been centered on dysfunction of organs other than the brain (e.g., heart, lungs, or kidneys), although the brain is one of the most prevalent organs involved. Recent studies indicate that nonpulmonary acute organ dysfunction may contribute significantly to mortality and other important clinical outcomes. Acute confusional states (delirium) occur in 10 to 60% of the older hospitalized population and in 60 to 80% of patients in the intensive care unit, yet go unrecognized by the managing physicians and nurses in 32 to 66% of cases. Delirium is an important independent prognostic determinant of hospital outcomes, including duration of mechanical ventilation, nursing home placement, functional decline, and death. Recently, new monitoring instruments have been validated for monitoring of delirium in noncommunicative patients receiving mechanical ventilation. Hence, critical care physicians and nurses should routinely assess their patients for delirium and develop strategies for its prevention and treatment.

RECENT FINDINGS

This state-of-the-art review discusses in depth the delirium monitoring instruments, the pathophysiology and risk factors of delirium, its prognostic implications, and strategies (including ongoing clinical trials) to prevent and treat delirium.

SUMMARY

Delirium is extremely common and has significant prognostic implications in critically ill patients. Routine monitoring and a multimodal approach to prevent or reduce the prevalence of delirium are of paramount importance.

Critical illness myopathy and neuropathy

PURPOSE OF REVIEW

To present the major pathophysiological and diagnostic features of critical illness myopathy (CIM) and polyneuropathy (CIP), and to discuss problems concerning the risk factors for CIM and CIP.

RECENT FINDINGS

The pathophysiology of critical illness myopathy and critical illness polyneuropathy is complex, involving metabolic, inflammatory, and bioenergetic alterations. This review cites new evidence supporting several pathogenetic mechanisms. These include microvascular changes in peripheral nerves (with increased endothelial expression of E-selectin), the possible role for an altered lipid serum profile in promoting organ dysfunction (including nerve dysfunction), the damage or inhibition of complex I of the respiratory chain as a cause of muscle ATP depletion and bioenergetic failure, and the activation of specific intracellular proteolytic systems causing myofilament loss and apoptosis in CIM. The diagnostic role of direct muscle stimulation and the rapid quantification of myosin/actin ratio based on electrophoresis are also presented.

SUMMARY

Basic and clinical research is unraveling the pathophysiological mechanisms of critical illness myopathy and polyneuropathy, and methods for rapid diagnosis are actively investigated. Future studies should better define the population at risk of developing CIM and CIP. In fact, although sepsis, multi-organ failure and steroids are often cited as risk factors, uncertainty remains due to the poor methodological quality of studies, or because of inferences that are exclusively based on animal studies. New simplified diagnostic techniques and machines for electrophysiological investigations of peripheral nerves and muscles in the intensive-care unit (ICU) patient would also be welcome.

Protection of hepatocyte mitochondrial ultrastructure and function by strict blood glucose control with insulin in critically ill patients

BACKGROUND

Maintenance of normoglycaemia by use of insulin reduces morbidity and mortality of patients in surgical intensive care. Studies on mitochondrial function in critical illness or diabetes suggest that effects of intensive insulin therapy on mitochondrial integrity contribute to the clinical benefits.

METHODS

Enzyme activities of the respiratory-chain complexes and oxidative-stress-sensitive glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were measured by spectrophotometry in 36 snap-frozen samples of liver and skeletal muscle obtained after death from patients who had been randomly assigned intensive (normoglycaemia) or conventional (hyperglycaemia) insulin therapy and who were similar in terms of admission diagnoses and causes of death. Mitochondrial ultrastructure was examined by electron microscopy in a random subgroup (n=20).

FINDINGS

In the liver, hypertrophic mitochondria with an increased number of abnormal and irregular cristae and reduced matrix electron density were observed in seven of nine conventionally treated patients. Only one of 11 patients given intensive insulin treatment had these morphological abnormalities (p=0.005). The effect on ultrastructure was associated with higher activities of respiratory-chain complex I (median 1.53 [IQR 1.14-3.01] vs 0.81 [0.54-1.43] U/g liver; p=0.008) and complex IV (1.69 [1.40-1.97] vs 1.16 [0.97-1.40] U/g; p=0.008) in the intensive group than in the conventional group. There was no detectable difference in GAPDH activity. In skeletal muscle, mitochondrial ultrastructure and function were not affected by intensive insulin therapy.

INTERPRETATION

Strict glycaemic control with intensive insulin therapy prevented or reversed ultrastructural and functional abnormalities of hepatocyte mitochondria. The lack of effect on skeletal-muscle mitochondria suggests a direct effect of glucose toxicity and glucose control, rather than of insulin, as the likely explanation.

RELEVANCE TO PRACTICE

Maintenance or restoration of mitochondrial function and cellular energetics is another therapeutic target, in addition to optimisation of cardiac output, systemic oxygen delivery, and regional blood flow, that might improve outcome for critically ill patients. Our findings could help to explain the mechanism underlying the reduction in mortality found when normoglycaemia was maintained with insulin, and further support use of intensive insulin therapy in this setting.

How does blood glucose control with insulin save lives in intensive care?

Patients requiring prolonged intensive care are at high risk for multiple organ failure and death. Insulin resistance and hyperglycemia accompany critical illness, and the severity of this "diabetes of stress" reflects the risk of death. Recently it was shown that preventing hyperglycemia with insulin substantially improves outcome of critical illness. This article examines some potential mechanisms underlying prevention of glucose toxicity as well as the effects of insulin independent of glucose control. Unraveling the molecular mechanisms will provide new insights into the pathogenesis of multiple organ failure and open avenues for novel therapeutic strategies.

How does blood glucose control with insulin save lives in intensive care?

Patients requiring prolonged intensive care are at high risk for multiple organ failure and death. Insulin resistance and hyperglycemia accompany critical illness, and the severity of this "diabetes of stress" reflects the risk of death. Recently it was shown that preventing hyperglycemia with insulin substantially improves outcome of critical illness. This article examines some potential mechanisms underlying prevention of glucose toxicity as well as the effects of insulin independent of glucose control. Unraveling the molecular mechanisms will provide new insights into the pathogenesis of multiple organ failure and open avenues for novel therapeutic strategies.

The pathophysiology of propofol infusion syndrome: a simple name for a complex syndrome

Propofol infusion syndrome (PRIS) is a rare and often fatal syndrome described in critically ill children undergoing long-term propofol infusion at high doses. Recently several cases have been reported in adults, too. The main features of the syndrome consist of cardiac failure, rhabdomyolysis, severe metabolic acidosis and renal failure. To date 21 paediatric cases and 14 adult cases have been described. These latter were mostly patients with acute neurological illnesses or acute inflammatory diseases complicated by severe infections or even sepsis, and receiving catecholamines and/or steroids in addition to propofol. Central nervous system activation with production of catecholamines and glucocorticoids, and systemic inflammation with cytokine production are priming factors for cardiac and peripheral muscle dysfunction. High-dose propofol, but also supportive treatments with catecholamines and corticosteroids, act as triggering factors. At the subcellular level, propofol impairs free fatty acid utilisation and mitochondrial activity. Imbalance between energy demand and utilisation is a key pathogenetic mechanism, which may lead to cardiac and peripheral muscle necrosis. Propofol infusion syndrome is multifactorial, and propofol, particularly when combined with catecholamines and/or steroids, acts as a triggering factor. The syndrome can be lethal and we suggest caution when using prolonged (>48 h) propofol sedation at doses higher than 5 mg/kg per h, particularly in patients with acute neurological or inflammatory illnesses. In these cases, alternative sedative agents should be considered. If unsuitable, strict monitoring of signs of myocytolysis is advisable.

Sepsis: a frequent, life-threatening syndrome

Innovative treatments have enhanced the understanding of the pathophysiology of sepsis. An understanding of the underlying nature of the disorder is necessary to develop new therapies and determine their roles in treating patients with sepsis. By studying and determining the interactions among the inflammatory, coagulation, and fibrinolytic pathways, investigators have discovered exciting new areas of research into the mechanisms of tissue injury in sepsis.