Surgically treated gangrenous or perforated appendicitis. A comparison of aztreonam and clindamycin versus gentamicin and clindamycin

Management of Severe Sepsis of Abdominal Origin

Severe sepsis is a life-threatening condition that may occur as a sequela of intra-abdominal infections (IAIs) of all types. Diagnosis of IAIs is predicated upon the combination of physical examination and imaging techniques. Diffuse peritonitis usually requires urgent surgical intervention. In the absence of diffuse peritonitis, abdominal computed tomography remains the most useful test for the diagnosis of IAIs, and is essential to both guide therapeutic interventions and evaluate suspected treatment failure in the critically ill patient. Parameters most consistently associated with poor outcomes in patients with IAIs include increased illness severity, failed source control, inadequate empiric antimicrobial therapy, and healthcare-acquired, as opposed to community-acquired infection. Whereas community-acquired IAI is characterized predominantly by enteric gram-negative bacilli and anaerobes that are susceptible to narrow-spectrum agents, healthcare-acquired IAI (e.g., anastomotic dehiscence, postoperative organ-space surgical site infection) frequently involves at least one multi-drug resistant pathogen, necessitating broad-spectrum therapy guided by both culture results and local antibiograms. The cornerstone of effective treatment for abdominal sepsis is early and adequate source control, which is supplemented by antibiotic therapy, restoration of a functional gastrointestinal tract (if possible), and support of organ dysfunction. Furthermore, mitigation of deranged immune and coagulation responses via therapy with recombinant human activated protein C may improve survival significantly in severe cases complicated by septic shock and multiple organ dysfunction syndrome.

Intra-abdominal infections

PURPOSE OF REVIEW

The aim of this article is to outline developments in the three cornerstones of treatment of intra-abdominal infections during critical illness: source control; antimicrobial therapy; and mitigation of deranged immune and coagulation responses.

RECENT FINDINGS

Although adequate source control remains the goal of mechanical management of intra-abdominal infections, neither planned re-laparotomy nor open-abdomen management appears to offer a survival benefit as compared with on-demand re-laparotomy. Novel approaches to restoration of a functional gastrointestinal tract have emerged as alternatives to more invasive surgery. A persistent increase in the prevalence of intra-abdominal infections caused by multidrug resistant pathogens has led researchers to investigate shorter-course antimicrobial therapy and other antibiotic administration strategies with encouraging initial results. Therapy with recombinant human activated protein C should now be considered for patients with severe abdominal sepsis associated with a high risk of death.

SUMMARY

Because randomized controlled trials of intra-abdominal infections involve critically ill patients infrequently, only limited evidence-based recommendations regarding the management of these patients may be drawn. Therapy should focus above all else on timely obtainment of adequate source control, in conjunction with judicious use of antimicrobial therapy dictated by individual patient risk factors for infection with multidrug resistant pathogens.

[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.

Antibiotic regimens for secondary peritonitis of gastrointestinal origin in adults

BACKGROUND

Secondary peritonitis is associated with a high mortality rate and if not treated successfully leads to development of abscesses, severe sepsis and multi-organ failure. Source control and adjunctive antibiotics are the mainstay of treatment. However, no conclusive evidence suggest that one antibiotic regimen is better than any other but at the same time have a lower toxicity.

OBJECTIVES

To ascertain the efficacy and adverse effects of different antibiotic regimens in treating intra-abdominal infections in adults. Outcomes were divided into primary (clinical success and effectiveness in reducing mortality) and secondary (microbiological success, preventing wound infection, intra-abdominal abscess, clinical sepsis, remote infection, superinfection, adverse reactions, duration of treatment required, effectiveness in reducing hospitalised stay, and time to defervescence).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library, Issue 4, 2004), MEDLINE (from 1966 to November 2004), EMBASE (from 1980 to November 2004) and Cochrane Colorectal Cancer Group specialised register SR-COLOCA. Bibliographies of identified studies were screened for further relevant trials.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing different antibiotic regimens in the treatment of secondary peritonitis in adults were selected. Trials reporting gynaecological or traumatic peritonitis were excluded from this review. Ambiguity regarding suitability of trials were discussed among the review team.

DATA COLLECTION AND ANALYSIS

Six reviewers independently assessed trial quality and extracted data. Data collection was standardised using data collection form to ensure uniformity among reviewers. Statistical analyses were performed using the random effects model and the results expressed as odds ratio for dichotomous outcomes, or weight mean difference for continuous data with 95% confidence intervals.

MAIN RESULTS

Fourty studies with 5094 patients met the inclusion criteria. Sixteen different comparative antibiotic regimens were reported. All antibiotics showed equivocal comparability in terms of clinical success. Mortality did not differ between the regimens. Despite the potential high toxicity profile of regimens using aminoglycosides, this was not demonstrated in this review. The reason for this could be the inherent bias within clinical trials in the form of patient selection and stringency in monitoring drug levels.

AUTHORS' CONCLUSIONS

No specific recommendations can be made for the first line treatment of secondary peritonitis in adults with antibiotics, as all regimens showed equivocal efficacy. Other factors such as local guidelines and preferences, ease of administration, costs and availability must therefore be taken into consideration in deciding the antibiotic regimen of choice. Future trials should attempt to stratify patients and perform intention-to-treat analysis to allow better external validity.

Aminoglycosides for intra-abdominal infection: equal to the challenge?

BACKGROUND

Aminoglycosides, combined with antianaerobic agents, have been used widely for the treatment of intra-abdominal infection. However, some prospective randomized controlled trials and other data suggested that aminoglycosides were less efficacious than newer comparators for the treatment of these infections. We therefore performed a meta-analysis of all prospective randomized controlled trials utilizing aminoglycosides to reevaluate the efficacy of these agents for the treatment of intra-abdominal infection.

METHODS

Published English-language prospective randomized controlled trials comparing aminoglycosides with other agents for treatment of intra-abdominal infection were identified by MEDLINE search. For each study, data were collected regarding the number of patients enrolled and evaluated, their basic demographic characteristics, the sources of the intra-abdominal infections, the number of failures as determined by the study investigators, quality score, and the use of serum drug concentrations to monitor aminoglycoside therapy. These data were combined to calculate odds ratios for risk of therapeutic failure, which were assessed for significance using Chi-square analysis.

RESULTS

Forty-seven prospective randomized controlled trials comparing aminoglycosides to other agents were identified. These were published between 1981 and 2000, and included a total of 5,182 evaluable patients. Analysis of all studies combined revealed an odds ratio that slightly, but significantly, favored the comparators. After excluding six trials using comparators that lacked accepted antianaerobic efficacy, the odds ratio more strongly favored comparators. Trials published since 1990 also notably favored comparators. Analyzing results by quality score or the use of aminoglycoside monitoring did not alter these findings.

CONCLUSIONS

In this meta-analysis, aminoglycosides were less efficacious than newer comparators for the treatment of intra-abdominal infection. Given the well-known toxicities of these agents, we conclude that they should not be used as first-line therapy for these infections.

Gangrenous and perforated appendicitis: a meta-analytic study of 2532 patients indicates that the incision should be closed primarily

BACKGROUND

Surgical incisions after appendectomy for complicated (gangrenous or perforated) acute appendicitis are often managed with delayed closure (DC) rather than primary closure (PC). This study synthesizes the results of other studies in the surgical literature and supports the routine use of PC.

METHODS

Studies dealing with complicated appendicitis were reviewed to assess the results of PC in comparison with DC. The rate of incision (wound) infection in groups of patients managed by PC and DC were compared with the use of a statistical technique that defined the probability of expected results by incorporating data derived from all of the various study groups.

RESULTS

Of the 2532 patients who had been treated for complicated appendicitis and who were assessed, 1724 patients underwent PC and 808 patients underwent DC. The rate of incision infection was 4.7% and 4.6% in the PC and DC groups, respectively. With a 95% confidence interval, there was no demonstrable difference between the 2 types of operative site management (P < .01).

CONCLUSIONS

PC of the skin and subcutaneous tissue after appendectomy for gangrenous or perforated appendicitis, combined with the use of antibiotic therapy in the perioperative period, is not associated with an increased risk of incision infection when compared with DC.

Carbapenems and monobactams: imipenem, meropenem, and aztreonam

Imipenem and meropenem, members of the carbapenem class of beta-lactam antibiotics, are among the most broadly active antibiotics available for systemic use in humans. They are active against streptococci, methicillin-sensitive staphylococci, Neisseria, Haemophilus, anaerobes, and the common aerobic gram-negative nosocomial pathogens including Pseudomonas. Resistance to imipenem and meropenem may emerge during treatment of P. aeruginosa infections, as has occurred with other beta-lactam agents; Stenotrophomonas maltophilia is typically resistant to both imipenem and meropenem. Like the penicillins, the carbapenems have inhibitory activity against enterococci. In general, the in vitro activity of imipenem against aerobic gram-positive cocci is somewhat greater than that of meropenem, whereas the in vitro activity of meropenem against aerobic gram-negative bacilli is somewhat greater than that of imipenem. Daily dosages may range from 0.5 to 1 g every 6 to 8 hours in patients with normal renal function; the daily dose of meropenem, however, can be safely increased to 6 g. Infusion-related nausea and vomiting, as well as seizures, which have been the main toxic effects of imipenem, occur no more frequently during treatment with meropenem than during treatment with other beta-lactam antibiotics. The carbapenems should be considered for treatment of mixed bacterial infections and aerobic gram-negative bacteria that are not susceptible to other beta-lactam agents. Indiscriminate use of these drugs will promote resistance to them. Aztreonam, the first marketed monobactam, has activity against most aerobic gram-negative bacilli including P. aeruginosa. The drug is not nephrotoxic, is weakly immunogenic, and has not been associated with disorders of coagulation. Aztreonam may be administered intramuscularly or intravenously; the primary route of elimination is urinary excretion. In patients with normal renal function, the recommended dosing interval is every 8 hours. Patients with renal impairment require dosage adjustment. Aztreonam is used primarily as an alternative to aminoglycosides and for the treatment of aerobic gram-negative infections. It is often used in combination therapy for mixed aerobic and anaerobic infections. Approved indications for its use include infections of the urinary tract or lower respiratory tract, intra-abdominal and gynecologic infections, septicemia, and cutaneous infections caused by susceptible organisms. Concurrent initial therapy with other antimicrobial agents is recommended before the causative organism has been determined in patients who are seriously ill or at risk for gram-positive or anaerobic infection.

Ticarcillin/Clavulanate versus Imipenem/Cilistatin for the Treatment of Infections Associated with Gangrenous and Perforated Appendicitis

The objective of this study was to compare ticarcillin/clavulanate given at 3.1 g every 6 hours with imipenem/cilistatin given at 500 mg every 6 hours for the treatment of infections associated with gangrenous or perforated appendicitis. One hundred thirty-seven patients were found to have gangrenous or perforated appendicitis and received the study medication for 3 to 5 days in a double-blinded, randomized manner. Clinical success was similar for the two treatment groups, 96.9 and 95.9 per cent in the ticarcillin/clavulanate and imipenem/cilistatin groups, respectively (P = 0.99; 95% confidence interval for the difference was -5.6% to 7.6%). Bacteriologic success at the end of therapy was similar in the two groups, 100 and 98.4 per cent in the ticarcillin/clavulanate and imipenem/cilistatin groups, respectively (P = 0.99; 95% confidence interval for the difference was -1.8% to 4.7%). The occurrence of adverse events related to treatment was similar for the two groups (P = 0.31) and led to study withdrawal for four patients (one with ticarcillin/clavulanate and three with imipenem/cilistatin). Ticarcillin/clavulanate given at 3.1 g every 6 hours is as effective and as safe as imipenem/cilistatin given at 500 mg every 6 hours for treatment of gangrenous or perforated appendicitis.

Management of perforated appendicitis in children: a decade of aggressive treatment

Perforated appendicitis in children continues to be associated with significant morbidity. In 1976, a treatment algorithm was begun at the authors' institution, which included immediate appendectomy, antibiotic irrigation of the peritoneal cavity, transperitoneal drainage through the wound, and 10-day treatment with intravenous ampicillin, clindamycin, and gentamicin. Initial results with this scheme in 143 patients demonstrated a 7.7% incidence of major complications and no deaths. From 1981 through 1991, the authors continued to use this treatment plan in all patients with perforated appendicitis. Three hundred seventy-three patients with perforated appendicitis were treated, and the rate of major complications was 6.4%. Infectious complications occurred in 18 patients (4.8%) and included intraabdominal abscesses (5 patients, 1.3%), phlegmon treated with an extended course of antibiotics (6 patients, 1.6%), wound infections (5 patients, 1.3%), and enterocutaneous fistula requiring further operations (2 patients, 0.5%). There were six cases of small bowel obstruction (1.6%), which required operative intervention. There were no deaths. The average length of stay for all patients was 11.4 days (range, 8 to 66 days). Utilization of transperitoneal drainage and choice of antibiotic therapy continue to be sources of controversy in the surgical literature. However, the treatment plan used in the present study resulted in the lowest complication rate reported to date, and the authors conclude that this scheme is truly the "gold standard" for treatment of perforated appendicitis. New treatment plans using laparoscopic appendectomy, different or shorter courses of antibiotics, or not using drains should have complication rates that are as low as, or lower than this one to be considered as useful alternatives.

Piperacillin/tazobactam in the treatment of polymicrobial infections

Polymicrobial infections are characterized by the presence of micro-organisms from more than one group of bacteria. Empirical treatment of polymicrobial infections requires an agent active against both anaerobic and aerobic/facultative bacteria. An aminoglycoside used in combination with an anti-anaerobe agent is commonly used to treat polymicrobial infections. However, aminoglycoside nephrotoxicity and treatment failures raise questions about the use of such regimens. Among non-aminoglycoside treatment regimens such as penicillin and cephalosporins, effectiveness has been compromised by bacteria producing extended spectrum beta-lactamases. Cefoxitin shows satisfactory results for treatment of intra-abdominal infections. Other studies have shown good results with imipenem, cefotetan and piperacillin used as single agents. Piperacillin/tazobactam, a new combination broad-spectrum antibiotic and potent beta-lactamase inhibitor, can be used for the treatment of infections caused by piperacillin-sensitive micro-organisms as well as beta-lactamase-producing, piperacillin-resistant organisms. This broad-spectrum activity is appropriate for infections traditionally treated empirically by double or triple antibiotic therapy.

[Antibiotic prophylaxis and appendectomy]

Analysis of clinical studies shows that a single preoperative systematic administration of antibiotics may reduce postoperative sepsis rate after appendicectomy. If the appendix is gangrenous or perforated, this therapy must last for a longer time and is not considered as a prophylaxis. In clinical practice, there are obvious advantages in the use of a single agent efficient against both aerobes and anaerobes. According to the literature, cefotetan or cefoxitin (2 g in adults, 40 mg.kg-1 in children) can be proposed.

Combination antibiotic therapy in the management of intra-abdominal infection

Combination antimicrobial regimens consisting of an agent with activity against gram-negative bacilli (an aminoglycoside) plus an agent with anaerobic activity (usually clindamycin or metronidazole) have traditionally been accepted as the standards for the treatment of intra-abdominal infection. Because of the problems of nephrotoxicity and ototoxicity in patients treated with aminoglycosides, clinical trials have been conducted using alternative combination therapy (e.g., aztreonam plus clindamycin) or single beta-lactam antimicrobial agents. Most clinical trials of intra-abdominal infections have been conducted in relatively small patient populations with a variety of low- and high-risk patients. The newer regimens have demonstrated efficacy equivalent to traditional combination therapy in selected patient populations. When selecting an antimicrobial regimen for treatment of intra-abdominal infection, multiple issues should be considered, including demonstrated efficacy in clinical trials, potential for adverse effects, and cost.

The monobactams

The monobactam antibiotics are synthetic compounds, although monocyclic beta-lactam compounds have been found in nature in various soil bacteria. Although additional orally and parenterally administered monobactams are under investigation, the first marketed monobactam was aztreonam. This agent has an antimicrobial spectrum similar to that of gentamicin and tobramycin, aminoglycoside antibiotics. Aztreonam, however, is not nephrotoxic, is weakly immunogenic, and has not been associated with disorders of coagulation. Aztreonam may be administered intramuscularly or intravenously; absorption after oral administration is poor. The primary route of elimination is the urine. The serum half-life of the drug in patients with normal renal function is 1.5 to 2.1 hours; the recommended dosing interval in patients with normal renal function is every 8 hours. Dosage adjustment is necessary in patients with renal impairment. The strictly gram-negative aerobic spectrum of aztreonam limits its use as a single empiric agent. Approved indications for its use include infections of the urinary tract or lower respiratory tract, intra-abdominal and gynecologic infections, septicemia, and cutaneous infections caused by susceptible organisms. Concurrent initial therapy with other antimicrobial agents is recommended before the causative organism (or organisms) has been determined in patients who are seriously ill and at risk for gram-positive or anaerobic infections.

The bacteriology of gangrenous and perforated appendicitis--revisited

By using optimum sampling, transport, and culture techniques in patients with gangrenous or perforated appendicitis, we recovered than has previously been reported. Thirty patients older than 12 years with histologically documented gangrenous or perforated appendicitis had peritoneal fluid, appendiceal tissue, and abscess contents (if present) cultured. Appendiceal tissue was obtained so as to exclude the lumen. A total of 223 anaerobes and 82 aerobic or faculatative bacteria were recovered, an average of 10.2 different organisms per specimen. Twenty-one different genera and more than 40 species were encountered. Bacteroides fragilis group and Escherichia coli were isolated from almost all specimens. Within the B. fragilis group, eight species were represented. Other frequent isolates included Peptostreptococcus (80%), Pseudomonas (40% [P. aeruginosa, 23.3%, other Pseudomonas spp., 16.7%]), B. splanchnicus (40%), B. intermedius (36.7%), and Lactobacillus (36.7%). Interestingly a previously undescribed fastidious gram-negative anaerobic bacillus was isolated from nearly one half of all patients. This organism was found to have low DNA homology (by dot blot) with the known organisms most closely resembling it.

A comparison of monobactam antibiotics in surgical infections

The introduction of gentamicin almost 20 years ago provided an effective option for the treatment of gram-negative bacillary infections. During the past few years, the availability of aztreonam (a monobactam), imipenem (a carbapenem), and newer cephalosporins within vitro activities comparable with aminoglycosides against many gram-negative bacilli, has stimulated a reassessment of the role of aminoglycosides in treating these infections. When determining the role of new antimicrobials as potential replacements for more established agents, the clinical focus should be on three factors: comparative efficacy, safety, and cost. Consideration of cost is relevant only when efficacy and safety are equivalent. Other factors, such as comparative in vitro antimicrobial activity, pharmacokinetics, and effect on normal flora can also influence the selection of an antimicrobial regimen. A new class of antimicrobials, the monobactams, is the focus of this review. The only member of this class currently in clinical use is aztreonam. A comparison with aminoglycosides is particularly relevant because aztreonam is active against aerobic gram-negative bacilli. This review will discuss the acknowledged concerns with aminoglycoside use and compare the characteristics of aztreonam and currently marketed aminoglycosides.

Preventing wound infection after appendicectomy: a review

An exponential increase in the number of published prospective studies reflects both a continuing interest in, and a lack of consensus on, the optimal prophylaxis of wound sepsis after appendicectomy. Review of the literature over the last 25 years leads us to emphasize both the importance of adequate study size and of stratification of the severity of the sepsis found at operation. For critical comparison of prophylactic regimens the high percentage of wound infections disclosed after discharge from hospital must be taken into account. Antibiotics reduce the frequency of wound sepsis and although low wound sepsis rates have been reported with systemic antibiotics active against only anaerobes, the cumulative evidence favours a spectrum of antibacterial activity against both aerobic and anaerobic organisms. Topical antiseptics have no significant effect but topical antibiotics are beneficial. Wide variations in outcome for similar antibiotic regimens reflect the importance of technical factors in determining the frequency of wound sepsis.

Use of new beta-lactam antibiotics for surgical infections

The availability of beta-lactam antibiotics with extended spectra of activity against organisms commonly seen in surgical infections suggests that aminoglycoside-based therapy is no longer needed for most such community-acquired infections. The primary problems with specific beta-lactams are lack of activity against Bacteroides species and variable activity against Pseudomonas aeruginosa and enterococci. The pharmacokinetic properties of the newer beta-lactams vary considerably. This variation suggests specific settings in which these properties may be taken advantage of to improve clinical outcome.