Epidemiology, pathophysiology and clinical presentation of gram-negative sepsis

The Management of Sepsis: A Practical Review

The incidence of the sepsis syndrome has increased dramatically in the last few decades. During this time we have gained new insights into the pathophysiologic mechanisms leading to organ dysfunction in sepsis and the importance of the host-bacterial interactions in mediating many of these processes. This knowledge has led to new therapeutic approaches and the investigation of a number of novel agents. An assessment of these approaches is presented to aid clinicians in the management of patients with severe sepsis. Criteria used to select studies included their relevance to the management of sepsis and their pertinence to clinicians. Appropriate antibiotic selection and volume resuscitation remain the cornerstone of treatment of septic patients. Hydroxyethyl starch solutions have theoretical advantages over crystalloids; there is, however, no data that the type of resuscitation fluid alters outcome. Vasoactive agents are required in patients who remain hemodynamically unstable or have evidence of tissue hypoxia after adequate volume resuscitation. Although dopamine is widely used, dobutamine and norepinephrine are our vasoactive agents of choice. Dopamine has no proven role in oliguric patients, with early dialysis recommended in patients with acute renal failure. The preferred method of renal replacement therapy remains to be determined. Blood products should be used cautiously in patients with disseminated intravascular coagulation. Therapeutic strategies that interfere with the immune system have not been proven to improve the outcome in unselected groups of patients. However, immunomodulation may prove to have a role in select subgroups of patients. Antibiotic therapy and intensive physiological support continues to be the main approach to the management of patients with severe sepsis. Despite the development of numerous novel therapeutic agents, these drugs have not been demonstrated to improve patient outcome.

Secular trends in mortality associated with new therapeutic strategies in surgical critical illness

BACKGROUND

Since 1999 randomized controlled trials have shown that new therapeutic strategies, such as strict glycemic control, increased use of noninvasive ventilation and of lung-protective ventilation, and early goal-oriented shock therapy, may reduce mortality in selected groups of critically ill patients. Whether these benefits can be translated to a surgical clinical setting is unclear. We wanted to evaluate longitudinally the successive routine implementation of new therapeutic measures and its effect on postsurgical patients admitted to the intensive care unit.

METHODS

We performed a retrospective analysis on data collected prospectively from March 1, 1993 through February 28, 2005.

RESULTS

A cohort of 1,802 consecutive cases requiring intensive care therapy for more than 4 days was analyzed. A significant decrease in mortality was observed in the last years of the study. With adjustment for relevant covariates, treatment after the implementation of new therapeutic strategies was identified as an independent factor linked with a reduced risk of death (odds ratio [OR] .518; 95% confidence interval [CI] .337-.796), whereas older age (OR 1.030; 95% CI 1.015-1.045), a high severity score on admission (OR 1.155; 95% CI 1.113-1.198) or during intensive care unit stay (OR 1.187; 95% CI 1.145-1.231), a high number of failing organs (OR 1.918; 95% CI 1.635-2.250), and peritonitis (OR 3.277; 95% CI 2.046-5.246) were independently associated with death.

CONCLUSIONS

Implementing of a variety of new therapeutic measures into routine care of critically ill surgical patients was associated with improved survival after 2001.

Red cell transfusion: an essential factor for patient prognosis in surgical critical illness?

In contrast to randomized studies, previous cohort studies identified red cell transfusion as an independent predictor of mortality in critically ill patients. However, these cohort studies did not adjust for disease severity during intensive care unit (ICU) stay. We performed a retrospective, observational cohort study using prospectively collected data from March 1, 1993, through February 28, 2005. A cohort of 3037 consecutive surgical cases requiring intensive care therapy for more than one day was analyzed. We used two different sets of potentially confounding covariables (admission variables only or in combination with variables reflecting number and extent of organ dysfunction during ICU stay). We found that the total number of red cell units which a case had received during ICU stay, and the maximum number of units given on a single day, were independently associated with an increase in ICU mortality when only admission variables were considered for the analysis. After controlling for the additional effect of variables reflecting organ dysfunction during ICU stay, we found that red cell transfusion was no longer an independent risk factor for death. However, there was a significant effect of red cell transfusion on ICU LOS in survivors irrespective of the covariable sets used. We conclude that red cell transfusion during ICU stay may be only a surrogate marker for disease severity and is not causally related to ICU mortality. Relevant side effects of red cell transfusion are presumably small and may be only recognizable in surviving cases.

[Trends in surgical intensive care. Experience in one centre over 12 years]

BACKGROUND

For critically ill medical patients until the year 2000, increases in patient age and severity of disease but also acute prognosis have been described. Since then, further improvement appears possible. Several controlled studies have recently demonstrated that acute mortality may be further lowered by new adjuvant therapies such as aggressive glycemic control. However, it is still unknown whether demographic changes and progress in intensive care can be reproduced in surgical critically ill patients outside of a controlled trial setting.

METHODS

We performed a retrospective, observational cohort study using data prospectively collected from the surgical intensive care unit (ICU) of the LMU Department of Surgery in Munich, Germany, Grosshadern Campus, from March 1 1993 through February 28 2005. Since 1999 we have successively introduced a variety of new therapies to daily routine. A cohort of 5,495 patients was analysed.

RESULTS

We identified reduced ICU mortality during the observation period, although age rose simultaneously and disease severity remained constant. Results from multivariate analysis suggest that improvements in prognosis essentially result from the implementation of new therapies after 2001. After adjusting for more than 20 covariables, treatment received after 2001 was identified as an independent factor linked with reduced risk of death.

CONCLUSIONS

General demographic trends and progress in intensive care can be demonstrated also in unselected surgical cohorts. Furthermore, the results here confirm the efficacy of new therapeutic modifications in routine therapy.

Lipopolysaccharide Transiently Activates THP-1 Cell Adhesion

Lipopolysaccharide stimulation of adherent THP-1 cells induces morphological changes that are associated with the reorganization of the actin cytoskeleton. We hypothesized that LPS would also increase THP-1 cell adhesion and sought to determine the signaling mechanisms regulating this response. We show that LPS significantly increases THP-1 cell attachment after 1 h, supporting the idea that LPS can stimulate integrin function. By 4 h however, the number of adherent cells returned to control levels. Importantly, detached cells were determined to be viable by propidium iodide staining, indicating that the increase in cell adhesion was transient. LPS-induced adhesion to fibrinogen- but not fibronectin-coated wells was also transient, suggesting that adhesion reflected beta2 integrin activation. This idea was supported by the fact that LPS-induced adhesion could be blocked by a function-blocking anti-beta2 integrin antibody. Interestingly, the protein tyrosine phosphatase (PTP) inhibitor, phenylarsine oxide, prevented cell detachment. Taken together, these data suggest that LPS-mediated integrin activation is transient and can be regulated by PTP-mediated signaling events.

Association between skin diseases and severe bacterial infections in children: case-control study

Background

Sepsis or bacteraemia, however rare, is a significant cause of high mortality and serious complications in children. In previous studies skin disease or skin infections were reported as risk factor. We hypothesize that children with sepsis or bacteraemia more often presented with skin diseases to the general practitioner (GP) than other children. If our hypothesis is true the GP could reduce the risk of sepsis or bacteraemia by managing skin diseases appropriately.

Methods

We performed a case-control study using data of children aged 0–17 years of the second Dutch national survey of general practice (2001) and the National Medical Registration of all hospital admissions in the Netherlands. Cases were defined as children who were hospitalized for sepsis or bacteraemia. We selected two control groups by matching each case with six controls. The first control group was randomly selected from the GP patient lists irrespective of hospital admission and GP consultation. The second control group was randomly sampled from those children who were hospitalized for other reasons than sepsis or bacteraemia. We calculated odds ratios and 95% confidence intervals (CI). A two-sided p-value less than 0.05 was considered significant in all tests.

Results

We found odds ratios for skin related GP consultations of 3.4 (95% CI: [1.1–10.8], p = 0.03) in cases versus GP controls and 1.4 (95% CI: [0.5–3.9], p = 0.44) in cases versus hospital controls. Children younger than three months had an odds ratio (cases/GP controls) of 9.2 (95% CI: [0.81–106.1], p = 0.07) and 4.0 (95% CI: [0.67–23.9], p = 0.12) among cases versus hospital controls. Although cases consulted the GP more often with skin diseases than their controls, the probability of a GP consultation for skin disease was only 5% among cases.

Conclusion

There is evidence that children who were admitted due to sepsis or bacteraemia consulted the GP more often for skin diseases than other children, but the differences are not clinically relevant indicating that there is little opportunity for GPs to reduce the risk of sepsis and/or bacteraemia considerably by managing skin diseases appropriately.

Identification and management of delirium in the critically ill patient with cancer

Rather than a specific entity, delirium is at the midpoint on a spectrum of potential mental status changes that ranges from full consciousness to deep coma. The extremes are relatively easy to recognize, but other points along the spectrum may go unrecognized or be misdiagnosed. If recognized and treated expeditiously, delirium may be reversed in some patients. It is imperative that those caring for critically ill patients with cancer have the knowledge and tools necessary to identify and manage delirium appropriately. Although all critically ill patients are at risk for delirium, cancer presents additional assaults to the central nervous system via direct tumor invasion or iatrogenic provocations. This article describes delirium in cancer, and addresses diagnostic and management issues across the course of the disease.

Multicenter evaluation of a human monoclonal antibody to Enterobacteriaceae common antigen in patients with Gram-negative sepsis

OBJECTIVE

To evaluate in Gram-negative sepsis patients the human monoclonal immunoglobulin M antibody (MAB-T88) directed at the enterobacterial common antigen which is a specific surface antigen closely linked to lipopolysaccharide and shared by all members of the Enterobacteriaceae family of Gram-negative bacteria.

DESIGN

Prospective, randomized, double-blinded, placebo-controlled, multicenter trial.

SETTING

Thirty-three academic medical centers in the United States.

PATIENTS

Patients were entered with a clinical diagnosis of sepsis, the presence of either shock or multiple organ dysfunction, and presumptive evidence for Gram-negative infection.

INTERVENTIONS

Patients received a single intravenous infusion, over 30 mins, of either 300 mg of MAB-T88 formulated in albumin, or placebo (albumin).

MEASUREMENTS AND MAIN RESULTS

The primary analysis group was prospectively identified as those patients with documented evidence of an infection with bacteria of the family Enterobacteriaceae at any site. The primary end point was survival within the first 28 days. A total of 826 patients were enrolled with 55% (n = 455) in the primary analysis group. There were no significant differences between the intervention and control primary analysis group study groups for sites of infection, severity of illness, underlying medical conditions, adequacy of antibiotic or surgical treatment, or other baseline variables except for a higher frequency of chronic renal failure in the MAB-T88 group (4.4% vs. 1.3%, p=.051). The average Acute Physiology and Chronic Health Evaluation II scores were 26.8 +/- 8.6 (mean +/- sd) in the MAB-T88-treated group and 26.5 +/- 8.3 in the placebo-treated group (p =.72). There was no significant difference between MAB-T88- and placebo-treated groups during the first 28-day all-cause mortality in the primary analysis group (34.2% vs. 30.8%, p=.44) or in all 826 patients enrolled (37.0% vs. 34.0%, p=.36). On subset analysis, the use of MAB-T88 was not associated with significant mortality trends. More adverse events were seen with the use of MAB-T88 in the bacteremic enterobacterial common antigen group (p <.05).

CONCLUSIONS

Use of the human monoclonal antibody, MAB-T88, did not improve the mortality in patients with presumed Gram-negative sepsis or in those patients with proven enterobacterial common antigen infections. No subset trends were identified that would support further investigation of this agent in sepsis.

Clinical implications of inducible beta-lactamase activity in Gram-negative bacteremia in children

BACKGROUND

Organisms of the spp., indole-positive spp., spp. and (ESCaPPM) group are a common cause of hospital-acquired bacteremia and share the potential to develop beta-lactam resistance during therapy. The emergence of such resistance may have adverse consequences, but the frequency with which this occurs has not been studied in children. It has been suggested that such organisms should be treated with combination antimicrobials or carbapenems, but the optimal regimen is uncertain. AIM To determine the frequency with which beta-lactam resistance develops during ESCaPPM sepsis in children and the optimal treatment of such sepsis.

METHODS

A review of the case notes and microbiologic records of all cases of ESCaPPM bacteremia and meningitis managed at a tertiary children's hospital during a 6-year period.

RESULTS

Fifty-eight cases were identified, and in three (5%) cases beta-lactam resistance emerged during treatment, with adverse clinical consequences in two cases. Clinical and microbiologic outcome was similar in those treated with carbapenems and in those treated with a beta-lactam and aminoglycoside combination. Cefotaxime resistance was found in 57, 30, 24 and 7% of children who had received carbapenems, cephalosporins, penicillins or no/other antimicrobials in the month before ESCaPPM sepsis, respectively.

CONCLUSIONS

The emergence of beta-lactam resistance during treatment of ESCaPPM sepsis is uncommon in our hospital but can have adverse consequences. Where isolates are reported as susceptible to both classes of drugs, an extended spectrum penicillin in combination with an aminoglycoside may be preferable first line treatment of ESCaPPM sepsis to a carbapenem or quinolone.

Physiopathological studies in septic rats and the use of fructose 1,6-bisphosphate as cellular protection

OBJECTIVE

The aim of this research project was to test the ability of fructose 1,6-bisphosphate (FBP), which has anti-inflammatory effects and maintains cellular energy levels, to inhibit the septic process in an experimental model in rats.

DESIGN

Prospective, controlled animal trial.

SETTING

Research laboratory.

SUBJECTS

Fed male Wistar rats.

INTERVENTIONS

Three experimental groups were formed for the test: control group, untreated septic group, and septic group treated with FBP (500 mg/kg).

MEASUREMENTS AND MAIN RESULTS

In the control group, there were no deaths; in the untreated septic group, the mortality rate was 100% within 15 hrs; in the septic group treated with FBP, the mortality rate reached 20% within 15 hrs. The blood cell tests revealed that concentrations of hematocrit, leukocytes, monocytes, and immature cells increased significantly in the untreated septic group compared with both the FBP-treated septic group and the control group. The histologic lesions verified in the heart, lungs, liver, and kidneys of septic animals were smaller and even absent in those treated with FBP.

CONCLUSION

FBP reduced the mortality rate provoked by experimental sepsis and ameliorated hematologic and histologic alterations.

Systemic inflammatory response syndrome

Despite advances in perinatal care in the past decade, sepsis and its complications continue to present problems for the neonate, remaining a major cause of neonatal morbidity and mortality. Sepsis research is focusing on how the neonate (host) responds to bacteria. The newborn may develop a systemic reaction to bacteria that induces the release of substances known as inflammatory mediators. Termed the systemic inflammatory response syndrome (SIRS), this reaction is believed to be responsible for the signs and symptoms of sepsis. This article introduces the neonatal nurse to SIRS, providing an overview of various inflammatory mediators and cytokines, their clinical consequences, and potential new therapies in the management of SIRS.

The effect of aging on circulating levels of proinflammatory cytokines during septic shock. Norasept II Study Investigators

BACKGROUND

As the proportion of the population that is older continues to rise, infection in older people has become an important healthcare problem. Although aging is associated with multiple abnormalities in immune function, the effect of aging on the production of proinflammatory cytokines has not been well studied under conditions of clinical stress.

OBJECTIVES

The aim of this study was to examine the effect of aging on circulating levels of the proinflammatory cytokines in a large cohort of septic shock patients. We hypothesized that aging would be associated with a diminished proinflammatory cytokine response to sepsis.

DESIGN

Patients with septic shock who were enrolled in the placebo limb of the North American Sepsis Trial (NORASEPT II) study were analyzed.

SETTING

The intensive care units of 105 hospitals in the United States and Canada.

PARTICIPANTS

Nine hundred and thirty patients presenting to hospital within 12 hours of the onset of septic shock.

MEASUREMENTS

Interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), soluble tumor necrosis factor-receptor-55 (sTNF-R55), and soluble tumor necrosis factor-receptor-75 (sTNF-R75) concentrations were measured at enrollment. The study population was broken down into five age groups as follows: less than 50 years (group one), 50 to 64 years (group two), 65 to 74 years (group three), 75 to 84 years (group four), and 85 or older (group five). Clinical, demographic, and cytokine data were extracted to describe each age group.

RESULTS

Data were available for 930 patients. The patients' mean age (+/- SD) was 59 +/- 17 years (range, 18 to 102). There were 280 patients in group one, 242 in group two, 210 in group three, 150 in group four, and 48 in group five. The primary diagnoses; clinical characteristics; and IL-6, sTNF-R55, and sTNF-R75 levels were similar among the five age groups. The TNF-alpha levels were significantly higher, however, in the oldest group of patients (group five). The 28-day survival was 49% in patients over the age of 75 and 58% in those under 75 years (P = .03). There was no gender difference in survival or cytokine levels.

CONCLUSIONS

Contrary to our expectations, we found that aging was not associated with a decline in the circulating levels of proinflammatory cytokines.

Anti-CD14 mAb treatment provides therapeutic benefit after in vivo exposure to endotoxin

The presence of endotoxin from Gram-negative bacteria signals the innate immune system to up-regulate bacterial clearance and/or killing mechanisms. Paradoxically, such responses also contribute to septic shock, a clinical problem occurring with high frequency in Gram-negative septicemia. CD14 is a receptor for endotoxin (lipopolysaccharide, LPS) and is thought to have an essential role in innate immune responses to infection and thereby in the development of septic shock. Using a novel rabbit model of endotoxic shock produced by multiple exposures to endotoxin, we show that anti-rabbit CD14 mAb, which blocks LPS-CD14 binding, protects against organ injury and death even when the antibody is administered after initial exposures to LPS. In contrast, anti-rabbit tumor necrosis factor mAb treatment fails to protect when administered after LPS injections. These results support the concept that anti-CD14 treatment provides a new therapeutic window for the prevention of pathophysiologic changes that result from cumulative exposures to LPS during septic shock in man.

The hemodynamic derangements in sepsis: implications for treatment strategies

The incidence of the sepsis syndrome has increased dramatically in the last few decades. During this time, we have gained new insights into the pathophysiologic mechanisms leading to organ dysfunction in this syndrome. Yet, despite this increased knowledge and the use of novel therapeutic approaches, the mortality associated with the sepsis syndrome has remained between 30% and 40%. Appropriate antibiotic selection and hemodynamic support remain the cornerstone of treatment of patients with sepsis. Recent studies have failed to demonstrate a global oxygen debt in patients with sepsis. Furthermore, therapy aimed at increasing systemic oxygen delivery has failed to consistently improve patient outcome. The primary aim of the initial phase of resuscitation is to restore an adequate tissue perfusion pressure. Aggressive volume resuscitation is considered the best initial therapy for the cardiovascular instability of sepsis. Vasoactive agents are required in patients who remain hemodynamically unstable or have evidence of tissue hypoxia after adequate volume resuscitation.

A rapid assay of endotoxin in whole blood using autologous neutrophil dependent chemiluminescence

A rapid (30 min) whole blood assay for the detection of lipopolysaccharide (LPS) is described. This chemiluminescent (CL) assay utilizes the CR1 and CR3 receptor-induced oxidant production of polymorphonuclear leucocytes as a detection platform. The differential priming of neutrophils in whole blood by LPS-antibody complexes allows the specificity of the assay to be achieved. Oxidant released in response to complement opsonized zymosan results in luminol oxidation and subsequent light emission. This is dependent on heat labile putative complement proteins in the plasma. The assay consists of a control which measures baseline whole blood neutrophil oxidant production. The test assay contains murine monoclonal IgM antibody against the Lipid A epitope of LPS and measures the enhanced chemiluminescent response of the neutrophils in the presence of LPS-antibody complexes. Maximal sensitivity of the CL assay is dependent upon optimal antigen-antibody equivalence and duration of pre-incubation with the whole blood sample. The quantification of LPS is possible by inclusion of a positive control containing a maximally reactive LPS dose (800 pg/ml Escherichia coli 055:B5 LPS at an antibody concentration of 0.8 microg/assay). The CL assay is insensitive to variations in patient neutrophil concentration over a minimum range of 0.5 to 20 x 10(9) cells/l. The CL assay is widely reactive with the LPS of many strains of gram negative bacteria but not with the cell wall products of gram positive bacteria or Candida and Aspergillus. In comparison to acid extraction chromogenic LAL, the CL assay demonstrates superior recovery precision and accuracy in in vitro studies. This was reproducible over a wide range of LPS concentrations (0.017-1.6 EU/ml or 20-2000 pg/ml). This assay may be a clinically useful tool for the diagnosis of infection or endotoxin in patients.

Fever and hypothermia: two adaptive thermoregulatory responses to systemic inflammation

Entering both the old dispute (whether fever is adaptive or maladaptive) and its more recent modification (whether hypothermia is protective or detrimental in systemic inflammation), we suggest a new solution. We hypothesize that fever and hypothermia represent two different strategies of fighting systemic inflammation, each developed as an adaptive response to certain conditions, and each beneficial under these conditions. The antimicrobial and immunostimulating benefits of a high body temperature could be easily offset by its high energy cost. Fever, therefore, is protective only when there is no immediate threat of a substantial energy deficit. Hypothermia, on the other hand, constitutes a response aimed at energy conservation and, as such, is beneficial exactly under the conditions of a substantial energy deficit. The two thermoregulatory responses represent two complementary strategies of survival in systemic inflammation: fever ensures the active attack against the pathogen; hypothermia secures the defense of the host's vital systems. The importance of each response's contribution to the whole campaign depends on the severity of the pathogenic insult, premorbid pathology, and current conditions (stress, nutrition, ambient temperature, etc.).

Acute mental status changes

Acute changes in mental status can occur in any hospital setting. Clinicians are often at a loss to define accurately the course of a change in mental status, because of poor differentiation in the terminology surrounding this difficult diagnosis. A clear understanding of the differences among several levels of altered mental status is needed to evaluate, accurately diagnose, and treat those patients with altered mental states. The differential diagnosis of altered mental status is diffuse and includes supratentorial mass lesions, infratentorial mass lesions, and metabolic disorders. Development of an individualized differential diagnosis and diagnostic approach for cases of altered mental status represents a challenge to all levels of clinicians.

Nitric oxide synthase inhibition versus norepinephrine for the treatment of hyperdynamic sepsis in sheep

OBJECTIVES

To investigate the effects of Nomega-mono-methyl-L-arginine (L-NMMA), an inhibitor of nitric oxide synthesis, on hemodynamics, oxygen transport, and regional blood flow in an ovine model of hyperdynamic sepsis and to compare these effects with the responses to norepinephrine.

DESIGN

Prospective, nonrandomized, controlled experimental study with repeated measures.

SETTING

Investigational intensive care unit at a university medical center.

SUBJECTS

Twenty-five female, healthy, adult sheep of the Merino breed, divided into three groups: nine control sheep; eight sheep treated with L-NMMA; and eight sheep treated with norepinephrine.

INTERVENTIONS

All sheep were chronically instrumented. After a 5-day recovery period, a continuous infusion of live Pseudomonas aeruginosa (2.5 x 10(6) colony-forming units/min) was started and maintained for the remainder of the experiment. After 24 hrs of sepsis, eight sheep received L-NMMA (7 mg/kg/hr), eight sheep received norepinephrine, and nine sheep received the vehicle alone (0.9% saline). The norepinephrine dosage was continuously and individually adjusted to achieve the same increase in blood pressure as was observed in a matched sheep of the L-NMMA group.

MEASUREMENTS AND MAIN RESULTS

After 24 hrs of sepsis, all sheep developed a hyperdynamic circulatory state with increased cardiac indices and reduced arterial pressures, and systemic vascular resistances. L-NMMA reversed the hyperdynamic circulation, causing an increase in arterial pressure by peripheral vasoconstriction. Norepinephrine led to an increase in blood pressure by augmenting cardiac indices, leaving the systemic vascular resistance unaffected. The norepinephrine dose needed to keep the blood pressure high had to be continuously increased, reflecting the reduced vascular responsiveness to catecholamines during sepsis. Renal blood flow remained unaffected by all treatment forms. Norepinephrine and L-NMMA led to a dramatic increase in urine production. Blocking the nitric oxide synthase with L-NMMA did not interfere with the host's pulmonary ability to clear bacteria, nor did treatment with norepinephrine.

CONCLUSIONS

Blocking nitric oxide synthase had a marked vasoconstrictive effect. Both norepinephrine and L-NMMA increased arterial pressure without reducing renal blood flow, leading to an improved renal function.