Multiorgan failure is an adaptive, endocrine-mediated, metabolic response to overwhelming systemic inflammation

Temporal changes in tissue cardiorespiratory function during faecal peritonitis

PURPOSE

Sepsis affects both macro- and micro-circulatory transport of oxygen to tissues, causing regional hypoxia. However, this relationship is poorly characterized with respect to inter-organ variability, disease severity and the evolution to organ dysfunction. We hypothesized that an early circulatory insult precedes the development of organ dysfunction, and is more severe in predicted non-survivors. Consequently, we assessed temporal changes in myocardial function and regional tissue oxygenation in peripheral and deep organs in a rat model of faecal peritonitis. We also examined the utility of a dynamic oxygen challenge test to assess the microcirculation.

METHODS

Awake, tethered, fluid-resuscitated male Wistar rats were randomized to receive intraperitoneal injection of faecal slurry, or to act as controls. At either 6 or 24 h post insult, rats were anaesthetized and underwent echocardiography, arterial cannulation and placement of tissue oxygen probes in peripheral (muscle, bladder) and deep (liver and renal cortex) organ beds. Measurements were repeated during fluid loading and an oxygen challenge test (administration of high oxygen concentrations).

RESULTS

Early sepsis (6 h) was characterized by a fall in global oxygen delivery with concurrent decreases in muscle, renal cortical and, especially, liver tissue PO2. By contrast, during established sepsis (24 h), myocardial and circulatory function had largely recovered despite increasing clinical unwellness, hyperlactataemia and biochemical evidence of organ failure. O2 challenge revealed an early depression of response that, by 24 h, had improved in all organ beds bar the kidney.

CONCLUSIONS

This long-term septic model exhibited an early decline in tissue oxygenation, the degree of which related to predicted mortality. Clinical and biochemical deterioration, however, progressed despite cardiovascular recovery. Early circulatory dysfunction may thus be an important trigger for downstream processes that result in multi-organ failure. Furthermore, the utility of tissue PO2 monitoring to highlight the local oxygen supply-demand balance, and dynamic O2 challenge testing to assess microcirculatory function merit further investigation.

Could hydroxyethyl starch be a therapeutic option in management of acute aluminum phosphide toxicity?

Acute aluminum phosphide poisoning is a serious toxicity and results in high mortality rate despite the progress of critical care. After ingestion, phosphine gas is released and absorbed quickly, causing systemic poisoning and cell hypoxia. Excessive thirst, severe hypotension, arrhythmias, tachypnea, and severe metabolic acidosis are the common clinical manifestations. We think acute metabolic response which characteristically occurs in severe injury also happens in aluminum phosphide poisoning. Necropsy examinations indicate congestion in almost all vital organs because of leakage of fluids from intravascular to extravascular space. The most favorable type of fluid for intravascular volume resuscitation persists and is disputed. Colloids remain in the intravascular space rather than crystalloids, and provide more rapid hemodynamic stabilization. Furthermore, hydroxyethyl starch solution may have other benefits e.g. it can reduce the extra vascular leak of albumin and fluids from an endothelial injury site. As refractory hypotension and cardiovascular collapse, because leakage of fluids from intravascular to extravascular space are common cause of death in this toxicity, we propose that hydroxyethyl starch can dominate this refractory hypotension and consequently acute metabolic response.

Stressing the obvious? An allostatic look at critical illness

Stress plays a crucial role in coping with extrinsic insults through modulating the autonomic nervous system, the hypothalamic-pituitary-adrenal axis and the cardiovascular, metabolic, and immune systems. The allostatic model of maintaining "stability through change" allows the body to respond to a challenge by adjusting to a new steady-state and terminating it once the danger has passed. However, unrelenting stress can lead to decompensation with development of pathologic illness. With sufficient activation the response may become more damaging than the stressor itself. Two types of "allostatic overload" are described: type 1 is an essentially protective response triggered by changes in environment, food supply, or physiologic status where energy demand exceeds supply. The response aims to reduce this imbalance by modifying behavior and intrinsic body systems to direct the animal into a survival mode. Type 2 overload occurs when there is sufficient or excess energy consumption; however, this situation does not trigger an escape or survival response. A clear analogy may be made to critical care where excess stress affects metabolic, hormonal, and immunoinflammatory responses and contributes to the development of organ failure. Ongoing stress also compromises recovery so it is incumbent upon caregivers to reduce stress, be it induced by tissue hypoxia, catecholamine infusion, sleep deprivation, pain, anxiety, and/or excess noise.

Detailed fluid resuscitation profiles in patients with severe acute pancreatitis

BACKGROUND AND AIM

Appropriate and timely initial fluid resuscitation in acute pancreatitis (AP) is critical. The aim of this retrospective study was to evaluate fluid therapy on an hour-by-hour basis in relation to standard indices of adequate resuscitation during AP.

METHODS

Emergency room shock charts, fluid balance sheets and intensive care (ICU) charts for all patients with AP admitted to ICU in a large acute hospital were examined. Vital signs, clinical course and fluid administered during the first 72 h after admission were tabulated against urine output, central venous pressure (CVP) and inotrope/vasopressor therapy.

RESULTS

Sixty-three consecutive patients with AP were initially evaluated. Inter-hospital transfers with established organ dysfunction (n= 11) or where records had insufficient detail (n= 22) were excluded. In the remaining 30 patients, in-hospital death occurred in 7. The cumulative volume of crystalloid given was significantly less at 48 h in patients who died in hospital (3331 ± 800 ml vs. survivors, 7287 ± 544 ml; P < 0.001). Non-survivors had a higher CVP, and received more inotropes/vasopressors.

CONCLUSION

  In severe AP-associated organ failure, fluid resuscitation profiles differ between survivors and non-survivors. CVP alone as a crude indicator of adequate resuscitation may be unreliable, potentially leading to the use of inotropes/vasopressors in the inadequately filled patient.

Mutation of mitochondrial ATP8 gene improves hepatic energy status in a murine model of acute endotoxemic liver failure

AIMS

Mitochondria not only generate and modulate bioenergy but also serve as biosensors for oxidative stress, and eventually become effector organelles for cell viability. Therefore, the implications of mitochondrial (dys)function in the development of multiple organ failure are profound. We investigated whether a mutation in the ATPase subunit-8 gene affects the course of endotoxemic acute liver failure.

MAIN METHODS

C57BL/6J (ATP8 wild type) and C57BL/6J-mt(FVB/N) (ATP8 mutant) mice were challenged with d-galactosamine (GalN) and Escherichia coli lipopolysaccharide (LPS) for induction of acute liver failure, and studied 6 h thereafter. Control mice received physiological saline only. Analysis included in vivo fluorescence microscopy of hepatic microcirculation and levels of hepatocellular apoptosis, hepatic adenosine nucleotides and oxidative stress. Additionally, survival rates were assessed.

KEY FINDINGS

Induction of endotoxemic liver failure provoked marked liver damage, which was coexistent with a drop of total adenosine nucleotide levels and increased oxidative stress. Of interest, oxidative stress was higher in the GalN/LPS challenged ATP8 mutants compared to wild types. Concomitantly, adenosine triphosphate (ATP) levels in livers of mice carrying the ATP8 mutation remained higher than those in wild type mice. As net result, ATP8 mutants showed lower transaminase release and a tendency to better survival rate upon GalN/LPS exposure compared to wild types.

SIGNIFICANCE

Our findings demonstrate that mutation in the ATPase subunit-8 partially protects mice against endotoxemic stress, most probably due to better hepatic energy status despite elevated oxidative stress. Thus, modulating mitochondrial function to preserve bioenergetic status may be an effective strategy to protect against sepsis-induced multiorgan dysfunction.

The evolutionary role of nutrition and metabolic support in critical illness

Maintenance of nutritional status is particularly challenging during critical illness. There is a common perception of a race against the clock to adequately feed the patient to prevent or minimize the sometimes catastrophic muscle wasting and general catabolic state that can result in the patient's deterioration. However, the course of critical illness may be separated into 3 phases, each with highly differing metabolic needs. The initial phase, in which the body attempts to fight the acute insult, is generally hypermetabolic. When the body fails to overcome the insult, it enters into a second phase, which is akin to hibernation. This stage is characterized by a functional metabolic shutdown triggered either by a lack of adequate energy supply or perhaps by the direct switching off of metabolism to spare excess use of a dwindling substrate and energy resource. Those strong enough to survive this phase enter into a period of recovery during which appetite returns, anabolism recommences, and organ function is restored. Nutrition should perhaps closely follow these nonlinear requirements, so as to avoid deleterious under- or overnutrition during the appropriate phase. This approach fits a teleologic argument that enabled many sick people to survive well before the advent of modern medicine and explains why catabolism still occurs despite adequate feeding.

A prospective case-control study of the local and systemic cytokine response after laparoscopic versus open colonic surgery

BACKGROUND

There is a sequential, high concentration cytokine response after major abdominal surgery. The magnitude of this response has been directly linked to postoperative metabolic derangement, ileus, adhesions, and oncological outcomes. We aimed to compare the local and systemic cytokine response in laparoscopic and open colonic surgery and relate this to postoperative recovery parameters.

METHODS

Using a prospectively collected patient database, we compared a Study Group (n = 50) of patients undergoing elective laparoscopic colonic resection with a Control Group (n = 25) of patients undergoing equivalent open colonic surgery within an ERAS program. Patients were matched for age, gender, BMI, ASA, Cr Possum, side of resection, diagnosis, and histologic stage. Plasma and peritoneal fluid concentrations of IL-6, IL-8, IL-10, and TNFα were measured at 20-24 h after surgery. The Surgical Recovery Score was determined pre-operatively and at 3, 7, 30, and 60 d postoperatively. All data were prospectively collected, and a priori definitions were used for discharge parameters, complications, and complication severity.

RESULTS

Peritoneal fluid IL-6 concentration was lower after laparoscopic surgery. There were no significant differences in the other cytokines measured, or in any postoperative recovery outcomes. Significant correlations were found between cytokine levels and discharge criteria achievement, day stay, postoperative complications, and the Surgical Recovery Score.

CONCLUSION

With the exception of a lower peritoneal IL-6 level, the systemic and peritoneal cytokine response at 20-24 h is similar after laparoscopic versus open colonic resection within an ERAS program, with corresponding equivalent rates of postoperative recovery.

Critical care: advances and future perspectives

Intensive care offers a standard of monitoring, intervention, and organ support that cannot be readily delivered in a general ward. Its expansion in the past few decades, including the creation of emergency and outreach teams, emphasises that intensive care has an increasingly prominent role within the hospital. Although outcomes are clearly improving, intensive care remains a nascent specialty in which we are still learning how to harness a powerful ability to manipulate physiology, biochemistry, and immunology to achieve best outcomes for the patient. The results of many multicentre studies have not lent support to, or have even confounded, expectations, drawing attention to several issues related to patient heterogeneity, trial design, and elucidation of underlying pathophysiological processes. However, these results have generated constructive introspection and reappraisal of treatments and management strategies that have benefited the patient. In addition to the medical, financial, and logistical challenges in the future, exciting opportunities will arise as new developments in diagnostic tests, therapeutic interventions, and technology are used to exploit an increasing awareness of how critical illness should be managed.

Radiation victim management and the haematologist in the future: time to revisit therapeutic guidelines?

PURPOSE

The use of nuclear/radiation devices against the civilian population is now a realistic scenario. Haematopoietic syndrome is the primary therapeutic challenge in the case of whole body acute exposure over 2 Grays (Gy) whereas burns and combined injuries would be frequently observed in myelo-suppressed patients. Optimisation of scoring and treatments are important goals to achieve.

CONCLUSION

The European Response Category (RC) concept represents an attempt to integratively assess haematological/extrahematological radiation-induced lesions. Based on the frequently observed heterogeneity of bone marrow damage in accidental/intentional irradiations, the stimulation of residual stem cells using granulocyte Colony-stimulating factor remains the therapeutic standard after exposure to less than the lethal dose 50 % (Haematopoietic[H] score 3-H3). Allogeneic stem cell transplantation is indicated in case of medullary eradication (Haematopoietic score 4-H4) whereas extramedullary toxicity may determine the outcome. Especially in case of numerous casualties exhibiting acute radiation syndrome, the administration of survival factor combinations remains questionable, at least as a palliative treatment. In addition pleiotropic cytokines injection such as erythropoietin and keratinocyte growth factor and grafting multipotent mesenchymal stem cells - from underexposed bone marrow areas or fat tissues - could be proposed to prevent multiple organ failure syndrome development. Multi-disciplinary teams should be prepared to manage such patients.

Adrenergic support in septic shock: a critical review

The definition of septic shock includes sepsis-induced hypotension despite adequate fluid resuscitation, along with the presence of organ perfusion abnormalities, and ultimately cell dysfunction. To restore adequate organ perfusion and cell homeostasis, cardiac output should be restored with volume infusion plus vasopressor agents as indicated. Appropriate arterial pressure for each individual patient and proper arterial oxygen content are key elements to restoring perfusion. Tissue perfusion can be monitored by markers of organ and mitochondrial function, namely urine output, level of consciousness, peripheral skin perfusion, central or mixed venous oxygen saturation, and lactate. The hemodynamic effects of the different vasopressor agents depend on the relative affinity to adrenergic receptors. Those with predominant alpha-agonist activity produce more vasoconstriction (inoconstrictors) while those with predominant beta-agonist stimulation increase cardiac performance (inodilators). The debate about whether one vasopressor agent is superior to another is still ongoing. The Surviving Sepsis Campaign guidelines refer to either norepinephrine or dopamine as the first-choice vasopressor agent to correct hypotension in septic shock. However, recent data from observational and controlled trials have challenged these recommendations concerning different adrenergic agents. As a result, our view on the prescription of vasopressors has changed from a probably oversimplified "one-size-fits-all" approach to a multimodal approach in vasopressor selection.

Concepts in hypoxia reborn

The human fetus develops in a profoundly hypoxic environment. Thus, the foundations of our physiology are built in the most hypoxic conditions that we are ever likely to experience: the womb. This magnitude of exposure to hypoxia in utero is rarely experienced in adult life, with few exceptions, including severe pathophysiology in critical illness and environmental hypobaric hypoxia at high altitude. Indeed, the lowest recorded levels of arterial oxygen in adult humans are similar to those of a fetus and were recorded just below the highest attainable elevation on the Earth's surface: the summit of Mount Everest. We propose that the hypoxic intrauterine environment exerts a profound effect on human tolerance to hypoxia. Cellular mechanisms that facilitate fetal well-being may be amenable to manipulation in adults to promote survival advantage in severe hypoxemic stress. Many of these mechanisms act to modify the process of oxygen consumption rather than oxygen delivery in order to maintain adequate tissue oxygenation. The successful activation of such processes may provide a new chapter in the clinical management of hypoxemia. Thus, strategies employed to endure the relative hypoxia in utero may provide insights for the management of severe hypoxemia in adult life and ventures to high altitude may yield clues to the means by which to investigate those strategies.

The humoral response after laparoscopic versus open colorectal surgery: a meta-analysis

BACKGROUND

The local and systemic humoral response after colorectal surgery is thought to affect postoperative recovery. It is commonly claimed that laparoscopic surgery elicits a diminished inflammatory response than equivalent open surgery. Despite these claims, the evidence is conflicting. Therefore, we aimed to systematically review the results from randomized controlled clinical trials comparing the humoral response associated with laparoscopic versus open colorectal surgery.

MATERIALS AND METHODS

A high-sensitivity search was conducted independently by two of the authors with no language restriction. Studies were identified from the Cochrane Central Register of Controlled Trials (CENTRAL/CCTR), Cochrane Library, Medline (January 1966 to January 2009), PubMed (1950 to January 2009), and Embase (1947 to January 2009). Relevant meeting abstracts and reference lists were manually searched. Data analysis was performed using Review Manager ver. 5.0.

RESULTS

Thirteen randomized controlled trials were included. Meta-analysis demonstrated a significantly higher serum IL-6 on d 1 after open colorectal resection for neoplasia (n = 97) compared with laparoscopic resection (n = 76, P = 0.0008) without significant heterogeneity. Data for plasma IL-6 were heterogeneous, with no apparent difference between groups. No other significant differences were identified, and there were not enough data on local peritoneal humoral factors to allow meta-analysis.

CONCLUSION

Open colorectal resection for neoplasia is associated with higher postoperative serum levels of IL-6 on d 1 than equivalent laparoscopic surgery. The aetiology and clinical significance of this finding is uncertain, and further studies are required to elucidate any differences in the local humoral response which may be more clinically relevant in surgery for this indication.

Peritoneal damage: the inflammatory response and clinical implications of the neuro-immuno-humoral axis

BACKGROUND

The peritoneum is a bilayer serous membrane that lines the abdominal cavity. We present a review of peritoneal structure and physiology, with a focus on the peritoneal inflammatory response to surgical injury and its clinical implications.

METHODS

We conducted a nonsystematic clinical review. A search of the Ovid MEDLINE database from 1950 through January 2009 was performed using the following search terms: peritoneum, adhesions, cytokine, inflammation, and surgery.

RESULTS

The peritoneum is a metabolically active organ, responding to insult through a complex array of immunologic and inflammatory cascades. This response increases with the duration and extent of injury and is central to the concept of surgical stress, manifesting via a combination of systemic effects, and local neural pathways via the neuro-immuno-humoral axis. There may be a decreased systemic inflammatory response after minimally invasive surgery; however, it is unclear whether this is due to a reduced local peritoneal reaction.

CONCLUSIONS

Interventions that dampen the peritoneal response and/or block the neuro-immuno-humoral pathway should be further investigated as possible avenues of enhancing recovery after surgery, and reducing postoperative complications.

A review of metabolic staging in severely injured patients

An interpretation of the metabolic response to injury in patients with severe accidental or surgical trauma is made. In the last century, various authors attributed a meaning to the post-traumatic inflammatory response by using teleological arguments. Their interpretations of this response, not only facilitates integrating the knowledge, but also the flow from the bench to the bedside, which is the main objective of modern translational research. The goal of the current review is to correlate the metabolic changes with the three phenotypes -ischemia-reperfusion, leukocytic and angiogenic- that the patients express during the evolution of the systemic inflammatory response. The sequence in the expression of multiple metabolic systems that becomes progressively more elaborate and complex in severe injured patients urges for more detailed knowledge in order to establish the most adequate metabolic support according to the evolutive phase. Thus, clinicians must employ different treatment strategies based on the different metabolic phases when caring for this challenging patient population. Perhaps, the best therapeutic option would be to favor early hypometabolism during the ischemia-reperfusion phase, to boost the antienzymatic metabolism and to reduce hypermetabolism during the leukocytic phase through the early administration of enteral nutrition and the modulation of the acute phase response. Lastly, the early epithelial regeneration of the injured organs and tissues by means of an oxidative metabolism would reduce the fibrotic sequelae in these severely injured patients.

Heme oxygenase 1 protects against hepatic hypoxia and injury from hemorrhage via regulation of cellular respiration

Heme oxygenase 1 (HO-1) is an important regulator of the cellular response to stress and inflammation. These investigations test the hypothesis that HO-1 overexpression protects against hemorrhage-induced hypoxia by regulating cellular respiration and oxygen availability. Male C57BL/6 mice or primary mouse hepatocytes were treated with adenoviral gene transfer of HO-1 (AdHO-1) or beta-galactosidase (AdLacZ). Mice were subjected to hemorrhagic shock and resuscitation or cannulation without hemorrhage. AdHO-1 prevented hemorrhagic shock/resuscitation-induced liver injury. In addition, AdHO-1 prevented hemorrhage-induced liver hypoxia and depletion of adenosine triphosphate. In vitro, HO-1 overexpression resulted in decreased cellular respiration under hypoxic conditions as determined by oxygen consumption and cytochrome c oxidase activity. This resulted in increased intracellular oxygen levels in the setting of low oxygen tensions. In conclusion, HO-1 overexpression protects the liver against hemorrhage-induced injury. This may be secondary to the ability of HO-1 to protect against bioenergetic failure via regulation of cellular respiration.

[The "time" factor. Its impact in pathophysiology and therapy of multiple trauma]

Pathophysiology of multiple trauma is characterized by different trauma-associated repercussions like organ destruction, haemorrhage, immune cell activation by foreign antigen, for example. The length of time while such impairments take hold of the organism substantially impacts the extent of the post trauma secondary injury. Short interruptions in microcirculation can mostly be compensated, whereas elongated ischemic periods definitely cause structural cell damage up to death. The current review highlights the importance of the time duration of posttrauma second hits on the pathophysiology of systemic inflammation and multiple organ failure. The quick termination of such secondary impairments by immediate therapeutic intervention mainly impacts the patients' prognosis.

Low-molecular-weight polyethylene glycol improves survival in experimental sepsis

OBJECTIVE

For several chronic inflammatory disease states, therapy is enhanced by improving the pharmacokinetic properties of anti-inflammatory drugs through conjugation with polyethylene glycol. We hypothesized that part of the beneficial action of PEGylated drugs may be derived from the anti-inflammatory properties of polyethylene glycol (PEG) itself.

DESIGN

Randomized, double-blinded, controlled ex vivo and in vivo laboratory studies.

SETTING

University research laboratories.

SUBJECTS

Human neutrophils and mononuclear cells, macrophage cell line, and adult rats and mice.

INTERVENTIONS

The effect of PEG (either low-molecular-weight [200-400] or high-molecular-weight [>4000]) was assessed on survival after systemic inflammation induced by lipopolysaccharide or zymosan. The effects of PEG on zymosan, lipopolysaccharide, or streptolysin-induced inflammatory and bioenergetic responses of immune cells were also assessed.

MEASUREMENTS AND MAIN RESULTS

Low-molecular-weight PEG reduced inflammatory cytokine expression, pyrexia, and mortality by >50% in both lipopolysaccharide and zymosan models of sepsis. Low-molecular-weight PEG reduced cytokine expression both in vivo and in vitro, and attenuated activation of human neutrophils in response to lipopolysaccharide or zymosan. By contrast, high-molecular-weight PEG conferred less significant survival effects after lipopolysaccharide and zymosan, and it did not exhibit such profound anti-inflammatory effects. Low-molecular-weight PEG attenuated lipopolysaccharide-induced activation of pro-apoptotic pathways (lysophosphatidic acid receptor and caspase-domain signaling) in the livers of endotoxemic rats. Streptolysin-induced necrosis of human neutrophils was reduced by low-molecular-weight PEG, indicating a mechanism that involves coating and/or stabilizing the cellular membrane. Low-molecular-weight PEG preserved human neutrophil responses to septic serum and bioenergetic function in macrophages and neutrophils.

CONCLUSION

PEG is a commonly used, safe, nonimmunogenic molecule possessing hitherto unappreciated anti-inflammatory properties. Low-molecular-weight PEG may potentially play a role in the therapy of systemic inflammation and sepsis.

NETWORKS, BIOLOGY AND SYSTEMS ENGINEERING: A CASE STUDY IN INFLAMMATION

Biological systems can be modeled as networks of interacting components across multiple scales. A central problem in computational systems biology is to identify those critical components and the rules that define their interactions and give rise to the emergent behavior of a host response. In this paper we will discuss two fundamental problems related to the construction of transcription factor networks and the identification of networks of functional modules describing disease progression. We focus on inflammation as a key physiological response of clinical and translational importance.

Applying gases for microcirculatory and cellular oxygenation in sepsis: effects of nitric oxide, carbon monoxide, and hydrogen sulfide

PURPOSE OF REVIEW

Nitric oxide, carbon monoxide, and hydrogen sulfide (H2S) are gases that have received attention as signaling molecules regulating many biological processes. All of them were reported to have beneficial effects in inflammatory states, in particular for microcirculatory perfusion and tissue energy balance. Thus, this review will highlight the most important results with a focus on resuscitated, clinically relevant experimental models and, if available, human studies.

RECENT FINDINGS

There is ample evidence that nitric oxide, carbon monoxide, and H2S may exert cytoprotective effects in shock states due to their vasomotor, antioxidant, and anti-inflammatory properties as well as their potential to induce a hibernation-like metabolic state called 'suspended animation' resulting from inhibition of cytochrome-c-oxidase. It must be emphasized, however, that the three molecules may also be cytotoxic, not only because of their inhibition of cellular respiration but also because of their marked pro-inflammatory effects.

SUMMARY

It is still a matter of debate whether manipulating nitric oxide, carbon monoxide, or H2S tissue concentrations, either by using the inhaled gas itself or by administering donor molecules or inhibitors of their endogenous production, is a useful therapeutic approach to improve microcirculatory blood flow, tissue oxygenation, and cellular respiration. This is mainly due to their 'friend and foe character' documented in various experimental models, but also to the paucity of data from long-term, resuscitated large animal experiments that fulfil the criteria of clinically relevant models.

Does PELOD measure organ dysfunction...and is organ function a valid surrogate for death?

Background

In December 2007, the European Society of Intensive Care Medicine established a Task Force to develop standard operating procedures (SOPs) for operating intensive care units (ICU) during an influenza epidemic or mass disaster.

Purpose

To provide direction for health care professionals in the preparation and management of emergency ICU situations during an influenza epidemic or mass disaster, standardize activities, and promote coordination and communication among the medical teams.

Methods

Based on a literature review and contributions of content experts, a list of essential categories for managing emergency situations in the ICU were identified. Based on three cycles of a modified Delphi process, consensus was achieved regarding the categories. A primary author along with an expert group drafted SOPs for each category.

Results

Based on the Delphi cycles, the following key topics were found to be important for emergency preparedness: triage, infrastructure, essential equipment, manpower, protection of staff and patients, medical procedures, hospital policy, coordination and collaboration with interface units, registration and reporting, administrative policies and education.

Conclusions

The draft SOPs serve as benchmarks for emergency preparedness and response of ICUs to emergencies or outbreak of pandemics.

Unsupervised selection of highly coexpressed and noncoexpressed genes using a consensus clustering approach

In this paper we explore the concept of consensus clustering to identify, within a set of differentially expressed genes, a subset of genes that are either highly coexpressed or highly noncoexpressed based on the hypothesis that this subset would serve as a better starting point for further analyses. A number of core clustering methods form the basis for the assertion of an agreement matrix (AM) characterizing the level of coexpression between any two probesets. In order to overcome the limitations of using a single distance metric, we explore different metrics and examine the sensitivity of the AM as a function of the input number of clusters to find a suggestive number of clusters that best describes a particular dataset. The result of this level of analysis is a systematic framework for eliminating probesets that cannot be clearly characterized as either coexpressed or noncoexpressed with others, thus eliminating a number of probesets from further analysis. Subsequently, an agglomerative hierarchical clustering approach is applied to cluster the selected subset using the agreement metric information as the similarity measure. Thus, the goal of the proposed methodology is twofold: (1) we opt to identify a more "clusterable" subset of the original set; and (2) we aim at further refining the subset in order to identify a core of genes that contains genes that are either coexpressed or noncoexpressed within a certain confidence level. The approach is tested with a number of data sets, both synthetic and real, and it is demonstrated that it is successful in identifying more clusterable, also hypothesized to be more biologically relevant, subsets of genes and expression profiles.

Is MOF an outcome parameter or a transient, adaptive state in critical illness?

PURPOSE OF REVIEW

The term 'multiorgan failure' (MOF) carries the negative connotation of major homeostatic breakdown and severe malfunction. However, this traditional paradigm may not be necessarily accurate. This review will investigate the rationale for no longer considering MOF to be simply a 'failed' pathophysiological state.

RECENT FINDINGS

Multiorgan failure is characterized by a hypometabolic, immunodepressed state with clinical and biochemical evidence of decreased functioning of the body's organ systems. Notwithstanding these findings, evidence for cell death is scarce and organ recovery is frequently the rule in surviving patients without pre-existing organ disease. Decreased mitochondrial activity appears to play a key role in the processes underlying MOF, both as a victim and a player. Reduced ATP production will compromise normal metabolic functioning. To protect itself from dying, the cell may adapt by decreasing its metabolic rate, and this is clinically manifest as organ dysfunction. Mitochondrial modulation may thus represent an important therapeutic target.

SUMMARY

The concept of MOF could be revisited as a transient state of metabolic shutdown analogous to hibernation. Avoiding the detrimental effects of inappropriate and counter-adaptive iatrogenic interventions is an important cornerstone of therapeutic management.

The stressed host response to infection: the disruptive signals and rhythms of systemic inflammation

The cognate signals from sterile or pathogen-induced sources converge on the same recognition or response pathways. In the surgical patient, a systemic response to infection most often occurs in the context of ongoing inflammatory stress. Such an inflammatory response is modulated initially by the magnitude of injury and by patient-specific (endogenous) factors, such as confounding illness, age, and genetic variation. Over an extended period of stress, treatmentrelated (exogenous) factors add unpredictability to host responses to subsequent challenges, such as acquired infection. The host response is discussed in the context of how existing sterile stressors may modify the response to acquired infection in surgical patients.

Innate immune responses to danger signals in systemic inflammatory response syndrome and sepsis

The systemic immune response induced by non-infectious agents is called systemic inflammatory response syndrome (SIRS) and infection-induced systemic immune response is called sepsis. The host inflammatory response in SIRS and sepsis is similar and may lead to multiple organ dysfunction syndrome (MODS) and ultimately death. The mortality and morbidity in SIRS and sepsis (i.e. critical illness) remain high despite advances in diagnostic and organ supporting possibilities in intensive care units. In critical illness, the acute immune response is organized and executed by innate immunity influenced by the neuroendocrine system. This response starts with sensing of danger by pattern-recognition receptors on the immune competent cells and endothelium. The sensed danger signals, through specific signalling pathways, activate nuclear transcription factor kappaB and other transcription factors and gene regulatory systems which up-regulate the expression of pro-inflammatory mediators. The plasma cascades are also activated which together with the produced pro-inflammatory mediators stimulate further the production of inflammatory biomarkers. The acute inflammatory response underlies the pathophysiological mechanisms involved in the development of MODS. The inflammatory mediators directly affect organ function and cause a decline in remote organ function by mediating the production of nitric oxide leading to mitochondrial anergy and cytopathic hypoxia, a condition of cellular inability to use oxygen. Understanding the mechanisms of acute immune responses in critical illness is necessary for the development of urgently needed therapeutics. The aim of this review is to provide a description of the key components and mechanisms involved in the immune response in SIRS and sepsis.

Bench-to-bedside review: Hydrogen sulfide--the third gaseous transmitter: applications for critical care

Hydrogen sulfide (H2S), a gas with the characteristic odor of rotten eggs, is known for its toxicity and as an environmental hazard, inhibition of mitochondrial respiration resulting from blockade of cytochrome c oxidase being the main toxic mechanism. Recently, however, H2S has been recognized as a signaling molecule of the cardiovascular, inflammatory and nervous systems, and therefore, alongside nitric oxide and carbon monoxide, is referred to as the third endogenous gaseous transmitter. Inhalation of gaseous H2S as well as administration of inhibitors of its endogenous production and compounds that donate H2S have been studied in various models of shock. Based on the concept that multiorgan failure secondary to shock, inflammation and sepsis may represent an adaptive hypometabolic response to preserve ATP homoeostasis, particular interest has focused on the induction of a hibernation-like suspended animation with H2S. It must be underscored that currently only a limited number of data are available from clinically relevant large animal models. Moreover, several crucial issues warrant further investigation before the clinical application of this concept. First, the impact of hypothermia for any H2S-related organ protection remains a matter of debate. Second, similar to the friend and foe character of nitric oxide, no definitive conclusions can be made as to whether H2S exerts proinflammatory or anti-inflammatory properties. Finally, in addition to the question of dosing and timing (for example, bolus administration versus continuous intravenous infusion), the preferred route of H2S administration remains to be settled--that is, inhaling gaseous H2S versus intra-venous administration of injectable H2S preparations or H2S donors. To date, therefore, while H2S-induced suspended animation in humans may still be referred to as science fiction, there is ample promising preclinical data that this approach is a fascinating new therapeutic perspective for the management of shock states that merits further investigation.

Reduced production of creatinine limits its use as marker of kidney injury in sepsis

Although diagnosis and staging of acute kidney injury uses serum creatinine, acute changes in creatinine lag behind both renal injury and recovery. The risk for mortality increases when acute kidney injury accompanies sepsis; therefore, we sought to explore the limitations of serum creatinine in this setting. In mice, induction of sepsis by cecal ligation and puncture in bilaterally nephrectomized mice increased markers of nonrenal organ injury and serum TNF-alpha. Serum creatinine, however, was significantly lower in septic animals than in animals subjected to bilateral nephrectomy and sham cecal ligation and puncture. Under these conditions treatment with chloroquine decreased nonrenal organ injury markers but paradoxically increased serum creatinine. Sepsis dramatically decreased production of creatinine in nephrectomized mice, without changes in body weight, hematocrit, or extracellular fluid volume. In conclusion, sepsis reduces production of creatinine, which blunts the increase in serum creatinine after sepsis, potentially limiting the early detection of acute kidney injury. This may partially explain why small absolute increases in serum creatinine levels are associated with poor clinical outcomes. These data support the need for new biomarkers that provide better measures of renal injury, especially in patients with sepsis.

Endotoxin causes functional endoplasmic reticulum failure, possibly mediated by mitochondria

Inflammatory response has recently been shown to induce endoplasmic reticulum (ER) stress and the unfolded protein response (UPR), which either recovers proper ER function or activates apoptosis. Here we show that endotoxin (lipopolysaccharide = LPS) can lead to functional ER failure tentatively via a mitochondrion-dependent pathway in livers of rats. Histological examination did not reveal significant damage to liver in form of necroses. Electron microscopy displayed transparent rings appearing around morphologically unchanged mitochondria, which were identified as dilated ER. The spliced mRNA variant of X-box protein-1 (XBP1) and also the mRNA of 78 kDa glucose-regulated protein (GRP78) were up-regulated, both typical markers of ER stress. However, GRP78 was down-regulated at the protein level. A pro-apoptotic shift in the bax/bcl-XL mRNA ratio was not accompanied by translocation of apoptosis inducing factor (AIF) to the nucleus, suggesting that the cells entered a pre-apoptotic state, but apoptosis was not executed. Monooxygenase activity of p450, representing the detoxification system in ER, was decreased after administration of endotoxin. Biochemical analysis of proteins important for ER function revealed the impairment of protein folding, transport, and detoxification suggesting functional ER failure. We suggest that functional ER failure may be a reason for organ dysfunction upon excessive inflammatory response mediated by endotoxin.