Microbial infection and the septic response in critical surgical illness. Sepsis, not infection, determines outcome

Gaps and opportunities in sepsis translational research

Infection initiates sepsis, but the clinical disease arises through the innate immune response of the host. A rapidly evolving understanding of the biology of that response has not been paralleled by the development of successful new treatment. The COVID-19 pandemic has begun to change this revealing the promise of distinct therapeutic approaches and the feasibility of new approaches to evaluate them. We review the history of mediator-targeted therapy for sepsis and explore the conceptual, biological, technological, and organizational challenges that must be addressed to enable the development of effective treatments for a leading cause of global morbidity and mortality.

Canine parvovirus: a predicting canine model for sepsis

BACKGROUND

Sepsis is a severe condition associated with high prevalence and mortality rates. Parvovirus enteritis is a predisposing factor for sepsis, as it promotes intestinal bacterial translocation and severe immunosuppression. This makes dogs infected by parvovirus a suitable study population as far as sepsis is concerned. The main objective of the present study was to evaluate the differences between two sets of SIRS (Systemic Inflammatory Response Syndrome) criteria in outcome prediction: SIRS 1991 and SIRS 2001. The possibility of stratifying and classifying septic dogs was assessed using a proposed animal adapted PIRO (Predisposition, Infection, Response and Organ dysfunction) scoring system.

RESULTS

The 72 dogs enrolled in this study were scored for each of the PIRO elements, except for Infection, as all were considered to have the same infection score, and subjected to two sets of SIRS criteria, in order to measure their correlation with the outcome. Concerning SIRS criteria, it was found that the proposed alterations on SIRS 2001 (capillary refill time or mucous membrane colour alteration) were significantly associated with the outcome (OR = 4.09, p < 0.05), contrasting with the 1991 SIRS criteria (p = 0.352) that did not correlate with the outcome. No significant statistical association was found between Predisposition (p = 1), Response (p = 0.1135), Organ dysfunction (p = 0.1135), total PIRO score (p = 0.093) and outcome. To explore the possibility of using the SIRS criteria as a fast decision-making tool, a Fast-and-Frugal tree (FFT) was created with a sensitivity of 92% and a specificity of 29%.

CONCLUSION

These results suggest that increasing the SIRS criteria specificity may improve their prognostic value and their clinical usefulness. In order to improve the proposed PIRO scoring system outcome prediction ability, more specific criteria should be added, mainly inflammatory and organ dysfunction biomarkers.

Phenotypic heterogeneity by site of infection in surgical sepsis: a prospective longitudinal study

Background

The role of site of infection in sepsis has been poorly characterized. Additionally, sepsis epidemiology has evolved. Early mortality has decreased, but many survivors now progress into chronic critical illness (CCI). This study sought to determine if there were significant differences in the host response and current epidemiology of surgical sepsis categorized by site of infection.

Study design

This is a longitudinal study of surgical sepsis patients characterized by baseline predisposition, insult characteristics, serial biomarkers, hospital outcomes, and long-term outcomes. Patients were categorized into five anatomic sites of infection.

Results

The 316 study patients were predominantly Caucasian; half were male, with a mean age of 62 years, high comorbidity burden, and low 30-day mortality (10%). The primary sites were abdominal (44%), pulmonary (19%), skin/soft tissue (S/ST, 17%), genitourinary (GU, 12%), and vascular (7%). Most abdominal infections were present on admission and required source control. Comparatively, they had more prolonged proinflammation, immunosuppression, and persistent organ dysfunction. Their long-term outcome was poor with 37% CCI (defined as > 14 in ICU with organ dysfunction), 49% poor discharge dispositions, and 30% 1-year mortality. Most pulmonary infections were hospital-acquired pneumonia. They had similar protracted proinflammation and organ dysfunction, but immunosuppression normalized. Long-term outcomes are similarly poor (54% CCI, 47% poor disposition, 32% 1-year mortality). S/ST and GU infections occurred in younger patients with fewer comorbidities, less perturbed immune responses, and faster resolution of organ dysfunction. Comparatively, S/ST had better long-term outcomes (23% CCI, 39% poor disposition, 13% 1-year mortality) and GU had the best (10% CCI, 20% poor disposition, 10% 1-year mortality). Vascular sepsis patients were older males, with more comorbidities. Proinflammation was blunted with baseline immunosuppression and organ dysfunction that persisted. They had the worst long-term outcomes (38% CCI, 67% poor disposition, 57% 1-year mortality).

Conclusion

There are notable differences in baseline predisposition, host responses, and clinical outcomes by site of infection in surgical sepsis. While previous studies have focused on differences in hospital mortality, this study provides unique insights into the host response and long-term outcomes associated with different sites of infection.

Acute-on-chronic liver failure: recent update

Acute on chronic liver failure (ACLF) was first described in 1995 as a clinical syndrome distinct to classic acute decompensation. Characterized by complications of decompensation, ACLF occurs on a background of chronic liver dysfunction and is associated with high rates of organ failure and significant short-term mortality estimated between 45% and 90%. Despite the clinical relevance of the condition, it still remains largely undefined with continued disagreement regarding its precise etiological factors, clinical course, prognostic criteria and management pathways. It is concerning that, despite our relative lack of understanding of the condition, the burden of ACLF among cirrhotic patients remains significant with an estimated prevalence of 30.9%. This paper highlights our current understanding of ACLF, including its etiology, diagnostic and prognostic criteria and pathophysiology. It is evident that further refinement of the ACLF classification system is required in order to detect high-risk patients and improve short-term mortality rates. The field of metabolomics certainly warrants investigation to enhance diagnostic and prognostic parameters, while the use of granulocyte-colony stimulating factor is a promising future therapeutic intervention for patients with ACLF.

Assessment of Severity of Peritonitis Using Mannheim Peritonitis Index

INTRODUCTION

Peritonitis is one of the most common problems in general surgery practice with high mortality rate. One of the reasons for high mortality is that peritonitis affects the general condition and leads to complications causing multiple organ failure, renal failure, sepsis, and postoperative ventilatory support. Early prognostic evaluation of patients with peritonitis is desirable to select high-risk patients for intensive management and also to provide a reliable objective classification of severity and operative risk.

PATIENTS AND METHODS

Fifty cases with diagnosis of peritonitis coming to Government Medical College, Amritsar, were studied. Stratification of these patients was done according to Mannheim peritonitis index (MPI), and their outcome was examined.

RESULTS

Mortality steadily increases with increase in MPI score. For patients with a score <21, the mortality rate was 0%; for score 21-27, it was 27.28%; and for score >27, it was 100% (P < 0.001). For patients with a score <21, the morbidity rate was 13.33%; for score 21-27, it was 65.71%; and for score >27, it was 100% (P < 0.001). Duration of pain >24 h, organ failure on admission, female sex, and feculent exudate were found to be independently significant factors in predicting the mortality among the study population. For a score of 27, the sensitivity was 66.67%, specificity was 100%, and positive predictive value for mortality is 100% at an accuracy of 94%.

CONCLUSION

This study proves that MPI scoring system is a simple and effective tool for assessing the morbidity and mortality in patients with peritonitis.

Reduction of the intestinal endotoxin pool by three different SDD regimens in human volunteers

Aerobic Gram-negative bacilli (AGNB) carried in the gut by healthy individuals generate 1 mg of 'physiological' endotoxin per g of faeces. Successful eradication of AGNB from the gut would be expected to lead to a lowering of the intestinal endotoxin pool. This prompted us to evaluate the reduction of intestinal endotoxin in 6 healthy volunteers who each received 3 different oral antibiotic regimens. Regimen 1 was polymyxin E (600 mg/day), regimen 2 polymyxin E (400 mg/day) combined with tobramycin (320 mg/day) and regimen 3 pefloxacin (800 mg/day). Each regimen was separated by an antibiotic free period of 3 months. A faecal sample (minimally 2 g) was obtained from each volunteer, before treatment began and afterwards 3 times a week on alternating days (Monday, Wednesday, Friday) for 3 weeks. Each volunteer produced 30 samples, 10 each per oral antibiotic. The samples were serially diluted in nutrient broth for the colony count of AGNB, whilst endotoxin was measured using the classical Limulus amoebocyte lysate micro-assay. The base-line value of faecal AGNB was 10 3-4 colony forming units/g of faeces. All samples obtained on day 3 following antibiotic intake were negative for AGNB, and remained negative during antibiotic intake. The AGNB free carrier state was associated with a reduction in gut endotoxin. The reduction was approximately 10 ng (1 log) for polymyxin E and pefloxacin, whilst the combination of polymyxin/tobramycin significantly reduced the intestinal endotoxin concentrations from 1 mg to 100 ng in the gut; a reduction of 104. Although AGNB were killed by the three regimens, the 'free' endotoxin left in the gut was effectively neutralised by the combination polymyxin/tobramycin only. From a clinical point of view, gut-derived endotoxaemia may play a role in the systemic inflammatory response syndrome and hence the outcome, in critically ill intensive care patients. This study supports other work which indicates that mortality is significantly reduced in only those intensive care patients who received oral polymyxin/tobramycin.

Why have clinical trials in sepsis failed?

The systemic inflammatory response is biologically complex, redundant, and activated by both infectious and noninfectious triggers. Its manipulation can cause both benefit and harm. More than 100 randomized clinical trials have tested the hypothesis that modulating the septic response to infection can improve survival. With one short-lived exception, none of these has resulted in new treatments. The current challenge for sepsis research lies in a failure of concept and reluctance to abandon a demonstrably ineffectual research model. Future success will necessitate large studies of clinical and biochemical epidemiology to understand the course of illness, better integration of basic and clinical science, and the creation of stratification systems to target treatment towards those who are most likely to benefit.

The PIRO (predisposition, insult, response, organ dysfunction) model: toward a staging system for acute illness

Multimodal therapy for diseases like cancer has only become practicable following the development of staging systems like the TNM (tumor, nodes, metastases) system. Staging enables the identification of subgroups of patients with a disease who not only have a differing prognosis, but who are also more likely to benefit from a specific therapeutic modality. Critically ill patients represent a highly heterogeneous population for whom multiple therapeutic options are potentially available, each carrying not only the potential for differential benefit, but also the potential for differential harm. The PIRO system (predisposition, insult, response, organ dysfunction) is a template proposal for a staging system for acute illness that incorporates assessment of pre-morbid baseline susceptibility (predisposition), the specific disorder responsible for acute illness (insult), the response of the host to that insult, and the resulting degree of organ dysfunction. However the creation of a valid, robust, and clinically useful system presents significant challenges arising from the complexity of the disease state, the lack of a clear phenotype, the confounding influence of the effects of therapy and of cultural and socio-economic factors, and the relatively low profile of acute illness with clinicians and the general public. This review summarizes the rationale for such a model of illness stratification and the results of preliminary cohort studies testing the concept. It further proposes two strategies for building a staging system, recognizing that this will be a demanding undertaking that will require decades of work.

Involvement of Interleukin-10 in the Anti-Inflammatory Effect of Sanyinjiao (SP6) Acupuncture in a Mouse Model of Peritonitis

In this study, we determined the anti-inflammatory effect of manual acupuncture at the Sanyinjiao or Spleen 6 (SP6) point on carrageenan-induced peritonitis in mice and investigated mechanisms that may underlie this effect. In the first set of experiments, male Swiss mice were allocated into five groups: the control (sterile saline), dexamethasone (DEXA), invasive sham-acupuncture (non-acupoint), SP6 acupuncture and carrageenan-treated groups. Ten minutes after needle retention or 30 min after DEXA treatment, mice received an intraperitoneal injection of carrageenan (750 μg/mouse). After 4 h, total leukocyte and differential cell counts (neutrophils and mononuclear), myeloperoxidase (MPO) activity, vascular permeability and cytokine levels were evaluated. In another set of experiments, adrenalectomized (ADX) mice were used to study the involvement of the adrenal gland on the therapeutic effects of acupuncture. Mice were allocated into two groups: the ADX and sham-operated animals (Sham ADX) that were subdivided into four subgroups each: the control (sterile saline), DEXA, SP6 acupuncture and carrageenan-treated groups. The SP6 and DEXA treatments inhibited the inflammatory cell infiltration, vascular permeability and MPO activity in carrageenan-injected mice. In addition, the SP6 treatment also increased interleukin (IL)-10 levels. In contrast, when the animals were adrenalectomized, the SP6 treatment failed to reduce total leukocyte and the plasma extravasation. In conclusion, this study clearly demonstrates the anti-inflammatory effect of SP6 acupuncture in a model of carrageenan-induced peritonitis. Our results demonstrated that SP6 acupuncture depends of the adrenal glands and increased IL-10 levels to produce its anti-inflammatory action.

Sepsis: rethinking the approach to clinical research

The clinical syndrome of sepsis encompasses a highly heterogeneous group of clinical disorders, varying with respect to the site, bacteriology, and even presence of infection and with the clinical syndrome evolving in the host. Clinical trials of strategies to modulate the host response that mediates sepsis were first initiated 25 years ago. A continuing record of disappointment has characterized subsequent work, and only a single new therapy has been licensed for clinical use. Yet, these commercial disappointments obscure a vibrant body of new knowledge that has clarified the biology of the innate immune response whose deranged expression is responsible for sepsis and that has provided important new insights into the failings of the traditional model of clinical research in sepsis. This review highlights advances in basic biology and underlines insights from clinical research that may point to new and more effective ways of translating an understanding of innate immunity into effective treatments for a leading cause of global morbidity and mortality.

Dynamic regulation of neutrophil survival through tyrosine phosphorylation or dephosphorylation of caspase-8

Efficient expression of innate immunity is critically dependent upon the capacity of the neutrophil to be activated rapidly in the face of an acute threat and to involute once that threat has been eliminated. Here we report a novel mechanism regulating neutrophil survival dynamically through the tyrosine phosphorylation or dephosphorylation of caspase-8. Caspase-8 is tyrosine-phosphorylated in freshly isolated neutrophils but spontaneously dephosphorylates in culture, in association with the progression of constitutive apoptosis. Phosphorylation of caspase-8 on Tyr-310 facilitates its interaction with the Src-homology domain 2 containing tyrosine phosphatase-1 (SHP-1) and enables SHP-1 to dephosphorylate caspase-8, permitting apoptosis to proceed. The non-receptor tyrosine kinase, Lyn, can phosphorylate caspase-8 on Tyr-397 and Tyr-465, rendering it resistant to activational cleavage and inhibiting apoptosis. Exposure to lipopolysaccharide reduces SHP-1 activity and binding to caspase-8, caspase-8 activity, and rates of spontaneous apoptosis. SHP-1 activity is reduced and Lyn increased in neutrophils from patients with sepsis, in association with profoundly delayed apoptosis; inhibition of Lyn can partially reverse this delay. Thus the phosphorylation and dephosphorylation of caspase-8, mediated by Lyn and SHP-1, respectively, represents a novel, dynamic post-translational mechanism for the regulation of neutrophil apoptosis whose dysregulation contributes to persistent neutrophil survival in sepsis.

Making sense of multiple organ dysfunction syndrome

Despite recent advances in critical care medicine, caring for patients with MODS remains one of the most challenging experience a critical care can encounter. New therapies that current exist and continue to be developed contribute to successful outcomes for patients with MODS, but there is no substitute for prevention and early intervention for persons at risk for developing MODS. Early and subtle changes in the patient who is at risk and has endured an initial insult can make a great difference in the patient's outcome and chances of mortality. Goal-directed therapy, supportive management, as well as an understanding of the inflammatory process are key to decreasing the mortality rate among patients with MODS.

Up-regulation of functional CXCR4 expression on human lymphocytes in sepsis

OBJECTIVE

Lymphocyte dysfunction has been documented in sepsis, and evidence suggests that lymphocyte infiltration contributes to tissue injury. The purpose of this study was to examine chemokine receptor expression and function in lymphocytes from septic patients and healthy donors.

DESIGN

Observational study of septic patients and laboratory investigation of normal controls.

SETTING

Tertiary care intensive care unit.

PATIENTS AND SUBJECTS

Nine critically ill patients fulfilling criteria for the systemic inflammatory response syndrome and with a Sepsis Score of >/=3 were included in this study. Lymphocytes were also obtained from healthy volunteers.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The total number of circulating leukocytes in septic patients was markedly increased; however, lymphocyte counts were decreased. Chemokine receptor expression on lymphocytes was examined by flow cytometry. CXCR4 expression on lymphocytes from septic patients was increased whereas CCR5 was decreased and CCR7 was unchanged. Lipopolysaccharide stimulation of normal lymphocytes increased CXCR4 expression but decreased CCR5 and did not change CCR7 expression. This lipopolysaccharide-stimulated CXCR4 expression required 20 hrs of stimulation and was accompanied by increased messenger RNA. Lymphocytes from septic patients or after lipopolysaccharide treatment demonstrated enhanced actin polymerization and migration in response to CXCL12. Taken together, sepsis and lipopolysaccharide up-regulated CXCR4 expression and enhanced lymphocyte activation and migration in response to CXCL12.

CONCLUSIONS

Blocking CXCR4 and CXCL12 function may provide a novel therapeutic method for controlling systemic inflammation and tissue injury in sepsis.

Systemic inflammatory response syndrome (SIRS): molecular pathophysiology and gene therapy

In recent years, extensive basic science research has led to a clear understanding of the molecular mechanisms contributing to the pathophysiology of sepsis. Sepsis is now defined as a systemic inflammatory response syndrome (SIRS) in which there is an identifiable focus of infection. SIRS can be also precipitated by non-infective events such as trauma, pancreatitis, and surgery. As a consequence of an overactive SIRS response, the function of various organ systems may be compromised, resulting in multiple organ dysfunction syndrome (MODS) and death. Production and activation of multiple proinflammatory genes are likely to play a key role in the pathogenesis of MODS development. This review article focuses on the molecular mechanisms and components involved in the pathogenesis of severe sepsis. This includes cellular targets of sepsis-inducing bacterial products and their signaling pathways with a major emphasis on transcription factors and new therapeutic approaches to severe sepsis.

Inclusion Criteria for Clinical Trials in Sepsis

BACKGROUND

Over the last 25 years, a growing number of clinical trials have evaluated novel sepsis therapies. To promote uniformity in inclusion criteria for patient enrollment, the American College of Chest Physicians and Society of Critical Care Medicine first published consensus conference definitions for sepsis in 1992.

STUDY OBJECTIVES

To characterize (1) the utilization of specific criteria for patient enrollment in sepsis clinical trials and (2) the impact that the consensus conference definitions have had on these criteria.

DESIGN

We used MEDLINE to identify clinical trials in sepsis from 1976 to 2001. Clinical trials published after the consensus conference (ACC; from 1993 to 2001) were compared with trials published before the consensus conference (BCC; from 1976 to 1992).

RESULTS

We identified 176 clinical trials (ACC, 119 trials; BCC, 57 trials). Clinical trials published ACC were more likely to utilize or reference a previously published standard for inclusion criteria (65% vs 11%, respectively; p < 0.001). The consensus conference definitions were the standards used in 69% of these trials. The utilization of specified values for WBC count, temperature (T), heart rate (HR), and respiratory rate (RR) was significantly increased in the ACC group compared to the BCC group, as follows: WBC count, 62% vs 26%, respectively (p < 0.001); T, 89% vs 56%, respectively (p < 0.001); HR, 77% vs 26%, respectively (p < 0.001); and RR, respectively 76% vs 28% (p < 0.001). ACC, clinical trials were less likely to require blood culture positivity (4 of 119 trials [3%] vs 9 of 57 trials [16%], respectively; p < 0.006) and were more likely to incorporate markers of acute organ dysfunction (81 of 119 trials [68%] vs 28 of 57 trials [49%], respectively; p < 0.03) in the inclusion criteria.

CONCLUSIONS

(1) Since 1992 there has been a significant increase in the utilization of predefined sepsis criteria for patient enrollment in clinical trials, and this increase can be attributed to the existence of consensus conference definitions. (2) Compared to inclusion criteria BCC, inclusion criteria ACC were less reliant on blood culture positivity and were more likely to incorporate markers of organ dysfunction.

Review of statistical data about severe burn patients treated during 2001 and evidence of septic cases in Albania

The objective of this study is to review the incidence of severe burns and the complications of burns sepsis in Albanians. The data are from clinical records of the patients hospitalised in the intensive care unit (ICU) of the Service of Burns, "Mother Teresa" University Hospital Center (UHC), Tirana, Albania during 2001. For the identification of sepsis in burned patients the classification of the American College of Chest Physicians/Society Critical Care Medicine (ACCP/SCCM) was used. All the cases were evaluated according to the clinical, diagnostic and laboratory data. The study presents some epidemiological data about the causative agent, the extent of burn, the depth of burn and the subjects injured. The study also identifies the pathogens responsible for the development of sepsis among patients. Such data was used to establish compound therapies focused on two or three antibiotics for each subject in order to treat sepsis and its possible complications. As a most important part of the treatment regime it is essential to identify patients at risk of sepsis, and to apply compound therapy with antibiotics in order to resist and treat this sepsis, which is the main cause of high mortality among our severely burned patients.

Pre-B cell colony-enhancing factor inhibits neutrophil apoptosis in experimental inflammation and clinical sepsis

Pre-B cell colony-enhancing factor (PBEF) is a highly conserved 52-kDa protein, originally identified as a growth factor for early stage B cells. We show here that PBEF is also upregulated in neutrophils by IL-1beta and functions as a novel inhibitor of apoptosis in response to a variety of inflammatory stimuli. Induction of PBEF occurs 5-10 hours after LPS exposure. Prevention of PBEF translation with an antisense oligonucleotide completely abrogates the inhibitory effects of LPS, IL-1, GM-CSF, IL-8, and TNF-alpha on neutrophil apoptosis. Immunoreactive PBEF is detectable in culture supernatants from LPS-stimulated neutrophils, and a recombinant PBEF fusion protein inhibits neutrophil apoptosis. PBEF is also expressed in neutrophils from critically ill patients with sepsis in whom rates of apoptosis are profoundly delayed. Expression occurs at higher levels than those seen in experimental inflammation, and a PBEF antisense oligonucleotide significantly restores the normal kinetics of apoptosis in septic polymorphonuclear neutrophils. Inhibition of apoptosis by PBEF is associated with reduced activity of caspases-8 and -3, but not caspase-9. These data identify PBEF as a novel inflammatory cytokine that plays a requisite role in the delayed neutrophil apoptosis of clinical and experimental sepsis.

Treatment failures in patients with ventilator-associated pneumonia

Treatment failures in patients with VAP are a complex issue and form a major challenge for clinicians. The following key elements inherent to a rational approach to treatment failures have been elucidated: (1) the presence of treatment failure must be thoroughly defined and assessed; (2) the many causes behind treatment failures must be realized, particularly the possibility of pneumonia-related and extrapulmonary reasons; (3) the recognition of different patterns of treatment failures as a useful framework for decisions about modalities and intensity of diagnostic reassessment; and (4) the establishment of a protocol for the search of pulmonary and extrapulmonary sites of infection and noninfectious causes of nonresponse. Only such a rational approach precludes the adverse effects of blind empiricism, which always implies a dangerous and costly overtreatment. Many issues related to treatment failures remain unsettled, and efforts will have to be made in the future to improve current clinical attitudes to treatment failures in VAP.

Doppler ultrasonographic evaluation of hepatic blood flow in clinical sepsis

The aim of this study was to determine the hemodynamic response of the liver to sepsis by measuring hepatic blood flow. Thirty patients with sepsis were examined using Doppler ultrasonography and measurements of portal venous blood flow, hepatic arterial blood flow and total hepatic blood flow were recorded. Data were retrospectively reviewed and compared with findings for a control group of 12 healthy subjects. Significantly increased values of hepatic blood flow (p<0.01) and portal venous blood flow (p<0.001) were observed in patients during early sepsis (5 h). In contrast, hepatic arterial blood flow was not significantly different from controls. During late sepsis (24 h), no significant differences were observed between patients and healthy controls. Our results support the concept that hepatic blood flow is significantly increased in patients with early sepsis due to increased portal venous blood flow; however, during late sepsis, hepatic blood flow is similar to that in controls.

Cytokines and inflammatory pathways in the pathogenesis of multiple organ failure following abdominal aortic aneurysm repair

Multiple organ failure is a common mode of death following abdominal aortic aneurysm repair, particularly after rupture. Cytokines are the principal mediators of the inflammatory response to injury and high levels of circulating cytokines have been associated with poor outcome in major trauma and sepsis. Abdominal aortic aneurysm repair results in an ischaemia-reperfusion injury to the tissues distal to the site of aortic clamping. The inflammatory response in these tissues causes the release of cytokines, principally Interleukins 1-beta, 6, and 8, and Tumour Necrosis Factor alpha. If released in large enough concentrations, these cytokines may enter the circulation and gain access to organs distant to the site of initial injury. Circulating cytokines cause dysfunction of the renal, cardiovascular, respiratory, nervous and musculo-skeletal systems. The combination of these individual changes in organ function is the multiple-organ dysfunction syndrome, which may progress to multiple organ failure.

Inflammation, coagulopathy, and the pathogenesis of multiple organ dysfunction syndrome

OBJECTIVE

An improved understanding of the mechanisms through which infecting pathogens harm the host is leading to new formulations of the concept of sepsis. We review the roles of inflammation and coagulation in the pathogenesis of the multiple organ dysfunction syndrome, and explore the potential of new therapies to restore the fine biological balance between procoagulant and anticoagulant mechanisms that are disrupted during the life-threatening processes that lead to organ dysfunction.

DATA SOURCES

Narrative review of published primary sources in the basic and clinical literature.

DATA SUMMARY

Traditional models of host-pathogen interactions ascribe the morbidity of infection to the direct cytotoxic effects of micro-organisms on host tissues. However, abundant experimental and clinical evidence has revealed that it is the response of the host, rather than the trigger that elicited it, that is the more potent determinant of outcome. The elucidation of a complex network of host-derived inflammatory mediators raised the possibility that targeting these individually could improve patient outcomes, and some modest successes with this approach have been achieved. More recently, it is becoming evident that the inflammatory response, in turn, mediates its deleterious effects by inducing tissue hypoxia, and cellular injury, either through tissue necrosis or through the induction of programmed cell death or apoptosis. Thus, treatment strategies that target the downstream consequences of the activation of inflammation, for example, microvascular coagulation or acute adrenal insufficiency, represent the latest, and some of the most promising approaches to attenuation of the septic response to improve survival, and minimize organ dysfunction. The maladaptive sequelae of systemic inflammation, embodied in the concept of the multiple organ dysfunction syndrome, comprise the leading obstacle to survival for patients admitted to a contemporary intensive care unit. Further insights into this intimidatingly complex process will not only provide potent new therapeutic options, but promise to transform critical illness from a biological standoff, during which the clinician merely supports failing organs, to a disease that can be successfully treated.

Pediatric sepsis and multiple organ dysfunction syndrome

Systemic inflammatory response syndrome may be viewed as the systemic expression of cytokine signals that normally function on an autocrine or paracrine level. Sepsis is defined as systemic inflammatory response syndrome caused by an infection. Multiple organ dysfunction syndrome may represent the end stage of severe systemic inflammatory response syndrome or sepsis. Many cells are involved, including endothelial cells and leukocytes and multiple proinflammatory and antiinflammatory mediators (cytokines, oxygen free radicals, coagulation factors, and so forth). Various pathophysiologic mechanisms have been postulated. The most popular theory is that the inflammatory process loses its autoregulatory capacity; however, microcirculatory dysregulation and apoptosis may also be important, and a new paradigm posits a complex nonlinear system. Many new treatments have been studied recently. The usefulness of immune modulating diets remains to be evaluated. Molecular immunomodulation is still of unclear value. The therapy of sepsis and multiple organ dysfunction syndrome remains mainly supportive.

The gut: the 'motor' of multiple organ dysfunction syndrome?

Abnormal colonization, gut-origin infections, and bacterial translocation are all signs of gut dysfunction that may be implicated in the pathogenesis of multiple organ dysfunction syndrome (MODS). This review summarizes and updates relevant experimental and clinical data that have attempted to correlate these phenomena with the development of MODS and to answer whether or not the gut is the 'motor' of MODS. The presented data suggest that, in some patients, gut dysfunction may precede the development of MODS. However, in most patients, this relationship is less obvious. The gut may still be one of the motors of MODS; however, it does not appear that this motor is fueled by the systemic spread of bacteria. Bacteria may play a role on a local gut-associated level in initiating and perpetuating the production of local inflammatory mediators that may produce distant organ injury.

Randomized clinical outcome study of critically ill patients given glutamine-supplemented enteral nutrition

Glutamine is normally an abundant amino acid in the body. It has many important metabolic roles, which may protect or promote tissue integrity and enhance the immune system. Low plasma and tissue levels of glutamine in the critically ill suggest that demand may exceed endogenous supply. A relative deficiency of glutamine could compromise recovery, resulting in prolonged illness and an increase in late mortality, morbidity, and consequently hospital costs. Using a prospective block-randomized, double-blind treatment study design, we tested whether a glutamine-containing enteral feed compared with an isonitrogenous, isoenergetic control feed would influence outcome. The study endpoints were morbidity, mortality, and hospital cost at 6 mo postintervention. In one general intensive care unit (ICU), to ensure consistency of management policies, 78 critically ill adult patients with Acute Physiological and Chronic Health Evaluation (APACHE) II score of 11 and greater and who were considered able to tolerate introduction of enteral nutrition were studied. Fifty patients successfully received enteral nutrition (26 glutamine, 24 control). There was no mortality difference between those patients receiving glutamine-containing enteral feed and the controls. However, there was a significant reduction in the median postintervention ICU and hospital patient costs in the glutamine recipients $23,000 versus $30,900 in the control patients (P = 0.036). For patients given glutamine there was a reduced cost per survivor of 30%. We conclude that in critically ill ICU patients enteral feeds containing glutamine have significant hospital cost benefits.

Intra-abdominal Candida infection during acute necrotizing pancreatitis has a high prevalence and is associated with increased mortality

OBJECTIVES

To analyze the frequency of intra-abdominal Candida infection during acute necrotizing pancreatitis and to compare the outcome to patients without Candida infections.

DESIGN

Retrospective analysis of data from 37 patients with and without Candida infection.

SETTING

Surgical intensive care unit (ICU) in a university hospital.

PATIENTS

Thirty-seven patients with acute necrotizing pancreatitis.

INTERVENTIONS

Patients were subject to necrosectomy and programmed lavage.

MEASUREMENTS AND MAIN RESULTS

Clinical parameters contained in the Acute Physiology and Chronic Health Evaluation (APACHE) II score were monitored, as were microbiological results from the intra-abdominal primary focus and from sites of secondary infections. Body mass index, distribution of underlying diseases, length of ICU stay, number of operations, and outcome were recorded. Multivariate logistic regression analysis for mortality as the dependent variable was performed. Intra-abdominal Candida infection was observed in 13 of 37 cases and was associated with a four-fold greater mortality rate compared with intra-abdominal bacterial infection alone. Multivariate logistic regression analysis demonstrated that Candida infection contributed to mortality significantly (p < .025) and independently from APACHE II (p < .006; mortality odds ratio for the two parameters=12.5). Lack of antimycotic treatment was associated with an increase to 29.2 (p<.001) in the odds ratio.

CONCLUSIONS

Given the impact of Candida infection on mortality to acute necrotizing pancreatitis and the apparent benefit from antimycotic chemotherapy, the data argue for an early fungicide chemotherapeutic intervention.

Does neutrophil-mediated oxidative stress play any significant role in producing hepatocellular dysfunction during early sepsis?

BACKGROUND

Although previous studies have indicated that hepatocellular dysfunction during early sepsis can be prevented by prior neutrophil depletion, it remains unknown whether the changes in hepatic oxidative stress induced by activated neutrophils are responsible for the salutary effect of neutropenia on hepatocellular function.

MATERIALS AND METHODS

Neutropenia was induced in the rat by intravenous injection of immunoglobulins directly against rat neutrophils (anti-neutrophil Ig) at 16 and 2 h prior to the initiation of cecal ligation and puncture (CLP, i.e., an animal model of polymicrobial sepsis) or sham operation. Neutropenia was confirmed by peripheral blood smears. Neutrophil-competent control animals were given nonimmunized Ig prior to the onset of sepsis. Sham animals received anti-neutrophil Ig or control Ig. The levels of reduced glutathione (GSH) and oxidized glutathione (GSSG) in the liver were determined at 5 h after CLP (i.e., the early, hyperdynamic stage of sepsis) or sham operation by high performance liquid chromatography.

RESULTS

Although the levels of hepatic GSH and GSSG decreased significantly at 5 h after CLP, irrespective of neutropenia, the ratio of GSSG/GSH was not significantly altered under such conditions. The decrease in hepatic glutathione concentrations in septic animals may represent the decreased synthesis or increased efflux into the bile or circulation.

CONCLUSION

Since neutrophil depletion did not significantly affect hepatic levels of GSH and GSSG as well as the GSSG/GSH ratio but prevented the occurrence of hepatocellular dysfunction, factors other than oxidative stress are likely to be the mechanism responsible for depressing hepatocellular function during the early, hyperdynamic stage of sepsis.

Increased colonic permeability in patients with ulcerative colitis: an in vitro study

BACKGROUND

Colonic permeability was studied in vitro in patients subjected to colectomy because of ulcerative colitis and in control patients undergoing colonic resections for cancer.

METHODS

The mucosal layer from fresh colonic segments was stripped and mounted in Ussing diffusion chambers containing modified Krebs buffer solution. The mucosa to serosa passage of the marker molecules 14C-mannitol and ovalbumin was measured for 120 min.

RESULTS

Marker passage was significantly increased in colitis patients compared with control patients, irrespective of age, sex, duration of disease, and treatment. Marker passage was further increased in patients with acute colitis. The increased colonic permeability may be explained by inflammation and the resultant loss of mucosal integrity. The increased permeability to ovalbumin implies that permeability to luminal macromolecules, such as bacterial products and other antigenic substances, might be increased in colitis.

CONCLUSIONS

The results suggest a derangement of the colonic barrier, as evidenced by an increased mucosal permeability in both chronic and acute colitis.

Prognostic value of gastric intramucosal pH in critically ill children

OBJECTIVE

To determine the association of tonometrically measured gastric intramucosal pH (pHi) to the occurrence of multiple organ dysfunction syndrome (MODS) and death in critically ill children.

DESIGN

Prospective, observational study.

SETTING

Pediatric intensive care unit (ICU) of a teaching children's hospital.

PATIENTS

Fifty-one critically ill children admitted (median age 5.4+/-5 [SD] yrs; range 1 mo to 16 yrs) with the following diagnoses: post major surgery (n=26), sepsis (n=8), multiple trauma (n=5), acute respiratory distress syndrome (n=4), and "miscellaneous" (n=8).

INTERVENTIONS

Placement of a tonometric catheter.

MEASUREMENTS AND MAIN RESULTS

Pediatric Risk of Mortality (PRISM) score and clinical data were collected on admission and pHi daily during their stay in the pediatric ICU. A sigmoid tonometer was used to determine the pHi. Unconditional logistic regression was used to investigate the prognostic value of pHi. On admission, 26 patients presented with low gastric pHi (< or =7.35) and 17 of them had values of <7.30. The mortality rate in children with pHi <7.30 was 47.1% (95% confidence interval, 26.2 to 69) in contrast with an 11.7% mortality rate (95% confidence interval, 4.6 to 26.6) in children having a pHi of > or =7.30 (p=.015). The pHi and PRISM score on admission were independent predictive factors of death. The risk of mortality is increased when the pHi is low (odds ratio=2.5). However, we did not find the pHi to be a predictor for developing MODS.

CONCLUSIONS

Our results show that pHi is an independent predictor of mortality in patients admitted to a pediatric ICU. Although no relationship was observed between the risk of MODS and gastric pHi, the univariate difference of 21% vs. 41% is highly suggestive. The pHi determination is a minimally invasive procedure and well tolerated in children of all ages.

Proinflammatory mediator activity, endogenous antagonists and the systemic inflammatory response in intra-abdominal sepsis. Scottish Sepsis Intervention Group

BACKGROUND

Severe intra-abdominal sepsis continues to carry a high mortality rate. The physiological response to sepsis in this condition and its relationship with proinflammatory mediators and their endogenous antagonists require further clarification.

METHODS

Fifty-seven patients were stratified by Acute Physiology And Chronic Health Evaluation (APACHE) II score at the time of admission to an intensive care unit (group 1, score of less than 20; group 2, score of 20 or more). Serial measurements of clinical and immunological variables were made.

RESULTS

Non-survivors from group 2 had a raised acute physiology score (P = 0.01), a higher peak serum interleukin (IL) 6 concentration (P = 0.03) and a depressed level of endogenous immunoglobulin (Ig) G class antiendotoxin core antibody (P = 0.005). In group 1, although organ failure score increased progressively in non-survivors, physiology score and peak IL-6 level were similar to those in survivors, and endogenous IgG class antiendotoxin core antibody titre rose (P = 0.02). In both groups IL-1 and tumour necrosis factor alpha were detected infrequently, but their natural antagonists were present in much higher concentrations in both survivors and non-survivors. Levels of C-reactive protein were raised in both but were not significantly different between survivors and non-survivors.

CONCLUSION

During the development of organ failure and death, the pattern of proinflammatory mediators and their endogenous antagonists can vary markedly and may in part be determined by the extent of the initial physiological disturbance.

Antibiotics for the acute abdomen

Antibiotics are only an adjunct to proper surgical therapy for the treatment of the acute abdomen associated with bacterial secondary peritonitis. Upon presentation, all patients require a preoperative dose of antibiotics for prophylaxis against infection of remaining sterile tissues. Patients found intraoperatively to have an established peritoneal infection benefit from an immediate postoperative course of therapeutic antibiotics. A regimen that adequately covers facultative and aerobic gram-negative bacilli and anaerobic organisms is essential. The duration of therapeutic antibiotics is probably best decided on an individual patient basis. The goal of antibiotics is to reduce the concentration of bacteria invading tissues. The pathogens of bacterial peritonitis are influenced by such factors as the patient's pre-existing chronic diseases, state of acute physiologic debilitation, immunocompetence, recent antibiotic use, recent hospitalization, and neutralization of gastric acidity. Intraoperative peritoneal cultures are most useful in patients suspected of having impaired local host defenses. In these patients, all identified organisms, such as Enterococcus or Candida, may be potential pathogens. The common practice of administering empiric and prolonged courses of broad-spectrum antibiotics in patients who manifest persistent signs of inflammation may be more harmful than beneficial. These patients warrant an exhaustive search for extra-abdominal and intraperitoneal sources of new infection. Otherwise, such use of antibiotics may continue to promote the selection of bacteria that are highly resistant to conventional antibiotics and permit the overgrowth of organisms commonly seen with tertiary peritonitis. The best chance of resolving bacterial peritonitis is through early, aggressive surgical management complemented by short courses of potent antibiotics and appropriate physiologic support. Through these efforts, the clinician tries to help the systemic inflammatory response to benefit the host and not become unregulated, result in MOFS, and produce a high mortality.

Infections and the inflammatory response in acute respiratory distress syndrome

STUDY OBJECTIVE

Systemic inflammatory response syndrome (SIRS) and infections are frequently associated with the development and progression of acute respiratory distress syndrome (ARDS) and multiple organ dysfunction syndrome (MODS). We investigated, at onset and during the progression of ARDS, the relationships among (1) clinical variables and biological markers of SIRS, (2) infections defined by strict criteria, and (3) patient outcome. Biological markers of SIRS included serial measurements of inflammatory cytokines (IC)-tumor necrosis factor-alpha (TNF-alpha) and interleukins (IL) 1 beta, 2, 4, 6, and 8-in plasma and BAL fluid.

METHODS

We prospectively studied two groups of ARDS patients: 34 patients treated conventionally (group 1) and nine patients who received glucocorticoid rescue treatment for unresolving ARDS (group 2). Individual SIRS criteria and SIRS composite score were recorded daily for all patients. Plasma IC levels were measured by enzyme-linked immunosorbent assay on days 1, 2, 3, 5, 7, 10, and 12 of ARDS and every third day thereafter while patients received mechanical ventilation. Unless contraindicated, bilateral BAL was performed on day 1, weekly, and when ventilator-associated pneumonia was suspected. Patients were closely monitored for the development of nosocomial infections (NIs).

RESULTS

ICU mortality was similar among patients with and without sepsis on admission (54% vs 40%; p < 0.45). Among patients with sepsis-induced ARDS, mortality was higher in those who subsequently developed NIs (71% vs 18%; p < 0.05). At the onset of ARDS, plasma TNF-alpha, IL-1 beta, IL-6, and IL-8 levels were significantly higher (p < 0.0001) in nonsurvivors (NS) and in those with sepsis (p < 0.0001). The NS group, contrary to survivors (S), had persistently elevated plasma IC levels over time. In 17 patients, 36 definitive NIs (17 in group 1 and 19 in group 2) were diagnosed by strict criteria. No definitive or presumed NIs caused an increase in plasma IC levels above patients' preinfection baseline. Daily SIRS components and SIRS composite scores were similar among S and NS and among patients with and without sepsis-induced ARDS, were unaffected by the development of NI, and did not correlate with plasma IC levels.

CONCLUSIONS

Sepsis as a precipitating cause of ARDS was associated with higher plasma IC levels. However, NIs were not associated with an increase in SIRS composite scores, individual SIRS criteria, or plasma IC levels above patients' preinfection baseline. SIRS composite scores over time were similar in S and NS. SIRS criteria, including fever, were found to be nonspecific for NI. Irrespective of etiology of ARDS, plasma IC levels, but not clinical criteria, correlated with patient outcome. These findings suggest that final outcome in patients with ARDS is related to the magnitude and duration of the host inflammatory response and is independent of the precipitating cause of ARDS or the development of intercurrent NIs.

TNF-alpha and endotoxin serum levels in cancer patients undergoing intraperitoneal hyperthermic perfusion

Intraperitoneal hyperthermic perfusion (IPHP) is performed as one treatment for patients with advanced gastrointestinal cancer complicated by peritoneal dissemination or carcinomatous peritonitis. However, the anticancer mechanism of IPHP and its safety have not yet been fully elucidated. It has been experimentally known that endotoxinemia occurs by high body temperature, and that endotoxin stimulates the macrophage, monocyte and endothelial cell to induce the production of TNF-alpha. TNF-alpha is one of cytokines to be induced at the initial phase as a host immune response and play an important role to initiate the systemic inflammatory response syndrome (SIRS). We have tested whether the serum concentrations of TNF-alpha and endotoxin are elevated following IPHP. Eleven patients with gastro-intestinal cancer underwent surgery combined with IPHP. Mixed venous blood obtained from pulmonary artery (PA-blood) was collected at four sampling points. TNF-alpha and endotoxin levels in the PA-blood were measured by ELISA and a limulus amoebocyte lysate assay respectively. In all patients the serum TNF-alpha levels in PA-blood were temporarily elevated following IPHP from less than 10 pg/ml before IPHP to 42.8 +/- 26.6 pg/ml; endotoxin levels were not altered. This study shows that IPHP has the ability to induce endogenous TNF-alpha not mediated by endotoxin.

Thiol-mediated redox regulation of neutrophil apoptosis

BACKGROUND

Intracellular glutathione, an endogenous antioxidant, protects cellular function against oxidative stress. Because oxidative stress has been implicated in neutrophil apoptosis, we hypothesized that reduced thiol levels may induce apoptosis through an alteration in cellular redox state.

METHODS

Human polymorphonuclear leukocytes (PMNs), were incubated with medium or with increasing concentrations of the reduced glutathione (GSH)-depleting agents diethylmaleate and diamide and buthionine sulfoximine, an inhibitor of GSH synthesis. Apoptosis was assessed by means of flow cytometry with propidium iodide DNA staining and confirmed morphologically. GSH was measured colorimetrically, and tyrosine phosphorylation was assessed by means of immunoblotting.

RESULTS

Diethylmaleate and diamide induced a dose-dependent reduction in GSH and a corresponding increase in PMN apoptosis. This effect could be reversed with N-acetylcysteine, suggesting that diethylmaleate induces apoptosis through the depletion of GSH. The antioxidant pyrolidine dithiocarbamate had no effect. Because oxidants can mediate intracellular signaling via tyrosine phosphorylation, we therefore evaluated the effects of the tyrosine kinase inhibition on diethylmaleate-induced PMN apoptosis. Both genistein and herbimycin A reduced diethylmaleate-induced apoptosis and tyrosine phosphorylation.

CONCLUSIONS

Sulfhydryl oxidation by diethylmaleate alone induces apoptosis, providing evidence of a redox-sensitive, thiol-mediated pathway of apoptosis. Furthermore, tyrosine phosphorylation appears to play an important role in this process. Because apoptosis is a critical mechanism regulating PMN survival in vivo, manipulation of PMN intracellular thiols may represents a novel therapeutic target for the regulation of cellular function.

Management of secondary peritonitis

OBJECTIVE

The authors review current definition, classification, scoring, microbiology, inflammatory response, and goals of management of secondary peritonitis.

SUMMARY BACKGROUND DATA

Despite improved diagnostic modalities, potent antibiotics, modern intensive care, and aggressive surgical treatment, up to one third of patients still die of severe secondary peritonitis. Against the background of current understanding of the local and systemic inflammatory response associated with peritonitis, there is growing controversy concerning the optimal antibiotic and operative therapy, intensified by lack of properly conducted randomized studies. In this overview the authors attempt to outline controversies, suggest a practical clinical approach, and highlight issues necessitating further research.

METHODS

The authors review the literature and report their experience.

RESULTS

The emerging concepts concerning antibiotic treatment suggest that less-in terms of the number of drugs and the duration of treatment-is better. The classical single operation for peritonitis, which obliterates the source of infection and purges the peritoneal cavity, may be inadequate for severe forms of peritonitis; for the latter, more aggressive surgical techniques are necessary to decompress increased intra-abdominal pressure and prevent or treat persistent and recurrent infection. The widespread acceptance of the more aggressive and demanding surgical methods has been hampered by the lack of randomized trials and reportedly high associated morbidity rates.

CONCLUSIONS

Sepsis represents the host's systemic inflammatory response to bacterial peritonitis. To improve results, both the initiator and the biologic consequences of the peritoneal infective-inflammatory process should be addressed. The initiator may be better controlled in severe forms of peritonitis by aggressive surgical methods, whereas the search for methods to abort its systemic consequences is continuing.