Intensive care unit management of intra-abdominal infection

Critical issues in the clinical management of complicated intra-abdominal infections

Intra-abdominal infections differ from other infections through the broad variety in causes and severity of the infection, the aetiology of which is often polymicrobial, the microbiological results that are difficult to interpret and the essential role of surgical intervention. From a clinical viewpoint, two major types of intra-abdominal infections can be distinguished: uncomplicated and complicated. In uncomplicated intra-abdominal infection, the infectious process only involves a single organ and no anatomical disruption is present. Generally, patients with such infections can be managed with surgical resection alone and no antimicrobial therapy besides perioperative prophylaxis is necessary. In complicated intra-abdominal infections, the infectious process proceeds beyond the organ that is the source of the infection, and causes either localised peritonitis, also referred to as abdominal abscess, or diffuse peritonitis, depending on the ability of the host to contain the process within a part of the abdominal cavity. In particular, complicated intra-abdominal infections are an important cause of morbidity and are more frequently associated with a poor prognosis. However, an early clinical diagnosis, followed by adequate source control to stop ongoing contamination and restore anatomical structures and physiological function, as well as prompt initiation of appropriate empirical therapy, can limit the associated mortality. The biggest challenge with complicated intra-abdominal infections is early recognition of the problem. Antimicrobial management is generally standardised and many regimens, either with monotherapy or combination therapy, have proven their efficacy. Routine coverage against enterococci is not recommended, but can be useful in particular clinical conditions such as the presence of septic shock in patients previously receiving prolonged treatment with cephalosporins, immunosuppressed patients at risk for bacteraemia, the presence of prosthetic heart valves and recurrent intra-abdominal infection accompanied by severe sepsis. In patients with prolonged hospital stay and antibacterial therapy, the likelihood of involvement of antibacterial-resistant pathogens must be taken into account. Antimicrobial coverage of Candida spp. is recommended when there is evidence of candidal involvement or in patients with specific risk factors for invasive candidiasis such as immunodeficiency and prolonged antibacterial exposure. In general, antimicrobial therapy should be continued for 5-7 days. If sepsis is still present after 1 week, a diagnostic work up should be performed, and if necessary a surgical reintervention should be considered.

[Therapeutic management of peritonitis]

Antibiotherapy is a fundamental for the treatment of peritonitis. It may be used before surgery or as a complementary treatment after. Experimental models have demonstrated that infections are both aerobic and anaerobic. During the first stage, septicemic with a high death rate, the infection is due to enterobacteria, mostly Escherichia coli. Between D5 and D7 in surviving animals, there is a second stage with abscesses due to anaerobic bacteria, mostly Bacteroides fragilis. The antibiotic treatment must include these two types of bacteria in its spectrum. The role of Enterococcus faecalis is not clearly defined, but this bacterium must be taken into account in case of organ failure or associated septic shock. Treatment options for secondary peritonitis may be, according to severity, cefoxitin, an Augmentin + gentamycin combination, Tazocillin, or ertapenem. The reference treatment for nosocomial or tertiary peritonitis is the imipenem + amikacin combination. An antifungal treatment (fluconazole) is usually necessary, at least until the results of peritoneal fluid culture are available. The duration of treatment is quite variable, ranging from 48 h in less severe forms to 14 days.

A multicenter trial of the efficacy and safety of tigecycline versus imipenem/cilastatin in patients with complicated intra-abdominal infections [Study ID Numbers: 3074A1-301-WW; ClinicalTrials.gov Identifier: NCT00081744]

BACKGROUND

Complicated intra-abdominal infections (cIAI) remain challenging to treat because of their polymicrobial etiology including multi-drug resistant bacteria. The efficacy and safety of tigecycline, an expanded broad-spectrum glycylcycline antibiotic, was compared with imipenem/cilastatin (IMI/CIS) in patients with cIAI.

METHODS

A prospective, double-blind, multinational trial was conducted in which patients with cIAI randomly received intravenous (IV) tigecycline (100 mg initial dose, then 50 mg every 12 hours [q12h]) or IV IMI/CIS (500/500 mg q6h or adjusted for renal dysfunction) for 5 to14 days. Clinical response at the test-of-cure (TOC) visit (14-35 days after therapy) for microbiologically evaluable (ME) and microbiological modified intent-to-treat (m-mITT) populations were the co-primary efficacy endpoint populations.

RESULTS

A total of 825 patients received >or= 1 dose of study drug. The primary diagnoses for the ME group were complicated appendicitis (59%), and intestinal (8.8%) and gastric/duodenal perforations (4.6%). For the ME group, clinical cure rates at TOC were 80.6% (199/247) for tigecycline versus 82.4% (210/255) for IMI/CIS (95% CI -8.4, 5.1 for non-inferiority tigecycline versus IMI/CIS). Corresponding clinical cure rates within the m-mITT population were 73.5% (227/309) for tigecycline versus 78.2% (244/312) for IMI/CIS (95% CI -11.0, 2.5). Nausea (31.0% tigecycline, 24.8% IMI/CIS [P = 0.052]), vomiting (25.7% tigecycline, 19.4% IMI/CIS [P = 0.037]), and diarrhea (21.3% tigecycline, 18.9% IMI/CIS [P = 0.435]) were the most frequently reported adverse events.

CONCLUSION

This study demonstrates that tigecycline is as efficacious as imipenem/cilastatin in the treatment of patients with cIAI.

Pharmacodynamic Modeling of β-lactam Antibiotics for the Empiric Treatment of Secondary Peritonitis: A Report from the OPTAMA Program

BACKGROUND

In this report of the OPTAMA (Optimizing Pharmacodynamic Target Attainment using the MYSTIC Antibiogram) program, we utilized Monte Carlo simulation to compare the probabilities of achieving bactericidal time above the minimum inhibitory concentration (MIC) (%T > MIC) exposures for imipenem-cilastatin 500 mg q6h and 1000 mg q8h, meropenem 500 mg q6h and 1000 mg q8h and piperacillin/tazobactam 3.375 g q6h and 4.5 g q8h in the empiric treatment of secondary peritonitis.

METHODS

The prevalence of pathogens causing secondary peritonitis was identified from the primary surgical and infectious diseases literature. Data for these pathogens with respect to MIC were obtained from the 2003 MYSTIC surveillance study and weighted by the prevalence of each pathogen. A sensitivity analysis varying the prevalence of P. aeruginosa was performed with two additional models to determine the robustness of the data. Pharmacokinetic parameters, obtained from previously published studies in healthy volunteers were used to simulate the %T > MIC for 10,000 patients receiving imipenem-cilastatin, meropenem, and piperacillin/tazobactam. The likelihood of obtaining bactericidal exposure is reported.

RESULTS

Empiric utilization of imipenem-cilastatin and meropenem 500 mg q6h and 1000 mg q8h regimens achieved 99.6%-99.7% likelihood of bactericidal exposure. Piperacillin/ tazobactam 3.375 g q6h and 4.5 g q8h produced bactericidal target attainments of 92.9% and 85.2%, respectively. Models simulating higher prevalence of P. aeruginosa reduced the likelihood of bactericidal exposure for piperacillin/tazobactam regimens significantly and had little effect on the carbapenems.

CONCLUSION

All of the beta-lactams used in the current analysis were predicted to achieve high target attainment consistently for the empiric treatment of secondary peritonitis. However, imipenem-cilastatin 500 mg q6h and 1000 mg q8h, meropenem 1000 mg q8h and 500 mg q6h, and piperacillin/tazobactam 3.375 g q6h achieved the highest likelihood. These, in particular, would be effective choices for the empiric treatment of secondary peritonitis.

Besonderheiten der abdominellen Sepsis

Abdominal sepsis remains a major cause of perioperative morbidity and mortality in surgical intensive care units. It must be considered a life-threatening condition and requires multidisciplinary coordination of intensive care. Apart from the local abdominal infection (peritonitis), abdominal sepsis is defined by extraperitoneal systemic reactions potentially leading to septic shock and death in the further course. Early and radical focus sanitation as well as aggressive systemic antimicrobial therapy remain the causal therapy strategies of abdominal sepsis.

The international sepsis forum consensus conference on definitions of infection in the intensive care unit

OBJECTIVE

To develop definitions of infection that can be used in clinical trials in patients with sepsis.

CONTEXT

Infection is a key component of the definition of sepsis, yet there is currently no agreement on the definitions that should be used to identify specific infections in patients with sepsis. Agreeing on a set of valid definitions that can be easily implemented as part of a clinical trial protocol would facilitate patient selection, help classify patients into prospectively defined infection categories, and therefore greatly reduce variability between treatment groups.

DESIGN AND METHODS

Experts in infectious diseases, clinical microbiology, and critical care medicine were recruited and allocated specific infection sites. They carried out a systematic literature review and used this, and their own experience, to prepare a draft definition. At a subsequent consensus conference, rapporteurs presented the draft definitions, and these were then refined and improved during discussion. Modifications were circulated electronically and subsequently agreed upon as part of an iterative process until consensus was reached.

RESULT

Consensus definitions of infection were developed for the six most frequent causes of infections in septic patients: pneumonia, bloodstream infections (including infective endocarditis), intravascular catheter-related sepsis, intra-abdominal infections, urosepsis, and surgical wound infections.

CONCLUSIONS

We have described standardized definitions of the common sites of infection associated with sepsis in critically ill patients. Use of these definitions in clinical trials should help improve the quality of clinical research in this field.

Toll-like receptor 4 deficiency and acute pancreatitis act similarly in reducing host defense during murine Escherichia coli peritonitis

OBJECTIVE

Acute pancreatitis is frequently complicated by Gram-negative sepsis. Mammalian cells recognize lipopolysaccharide from Gram-negative bacteria via Toll-like receptor (TLR) 4. The objective of this study was to determine the role of TLR4 in the defense against Gram-negative sepsis in previously healthy mice and in animals with preexisting pancreatitis.

DESIGN

A controlled, in vivo laboratory study.

SETTING

Research laboratory of a health sciences university.

SUBJECTS

Female C3H/HeJ (nonfunctional TLR4 mutant) and C3H/HeN (wild-type) mice.

INTERVENTIONS

Abdominal sepsis was induced by the intraperitoneal injection of Escherichia coli. Pancreatitis was induced by 12 hourly intraperitoneal injections of cerulein.

MEASUREMENTS AND MAIN RESULTS

The following experiments were performed. First, healthy TLR4 mutant mice demonstrated an enhanced bacterial load and dissemination of the infection relative to wild-type mice after intraperitoneal injection with E. coli, associated with a reduced early release of proinflammatory cytokines and an attenuated influx of neutrophils into the peritoneal fluid. Second, wild-type mice in which acute pancreatitis was induced by repeated cerulein injections showed an increased bacterial load and dissemination of E. coli relative to wild-type mice without pancreatitis, which was accompanied by a blunted proinflammatory cytokine response by peritoneal macrophages ex vivo and a diminished early cytokine and neutrophil response in vivo. Third, whereas the severity of cerulein-induced pancreatitis was similar in TLR4 mutant and wild-type mice, the important contribution of TLR4 to an effective host defense against E. coli sepsis observed in previously healthy mice was no longer present in mice with preexisting pancreatitis.

CONCLUSIONS

These data suggest that TLR4 deficiency and acute pancreatitis act similarly in reducing host defense against E. coli peritonitis and that the role of TLR4 in severe Gram-negative infection depends, at least in part, on the presence of preexisting critical illness.