Intraabdominal infections

CS, a 55-year-old woman, is admitted to the hospital with an intraabdominal infection. During the patient interview, CS states that she is allergic to aspirin, codeine, sulfa drugs, penicillin, levofloxacin, and vancomycin. The reactions are described as follows ... 

Define and differentiate between primary and secondary intraabdominal infections. 

Describe the role of culture and susceptibility information for diagnosis and treatment of intraabdominal infections. 

Recommend the most appropriate drug and nondrug measures to treat intraabdominal infections. 

O Most intraabdominal infections are secondary infections that are caused by a defect in the gastrointestinal tract that must be treated by surgical drainage, resection, and/or repair. 

Secondary intraabdominal infections usually are caused by a mixture of enteric gram-negative bacilli and anaerobes. This mix of organisms enhances the pathogenic potential of the bacteria. 

Cultures of secondary intraabdominal infection sites generally are not useful for directing antimicrobial therapy. Treatment generally is initiated on a presumptive or empirical basis. 

Antimicrobial regimens for secondary intraabdominal infections should include coverage for enteric gram-negative bacilli and anaerobes. Antimicrobial agents that may be used... 

The duration of antimicrobial treatment should be for a total of 5 to 7 days for most intraabdominal infections. 

O Primary peritonitis develops in up to 25% of patients with alcoholic cirrhosis.3 Patients undergoing continuous ambulatory peritoneal dialysis (CAPD) average one episode of peritonitis every 2 years.4 Secondary peritonitis may be caused by perforation of a peptic ulcer traumatic perforation of the stomach, small or large bowel, uterus, or urinary bladder appendicitis pancreatitis diverticulitis bowel infarction inflammatory bowel disease cholecystitis operative contamination of the peritoneum or diseases of the female genital tract such as septic abortion, postoperative uterine infection, endometritis, or salpingitis. Appendicitis is one of the most common causes of intraabdominal infection. In 1998, 278,000 appendectomies were performed in the United States for suspected appendicitis.5... 

Many of the manifestations of intraabdominal infections, particularly peritonitis, result from cytokine activity. Inflammatory cytokines are produced by macrophages and neutrophils in... 

Bacteria such as E. coli appear responsible for the early mortality from peritonitis, whereas anaerobic bacteria are major pathogens in abscesses, with B. fragilis predominating.15 Enterococcus can be isolated from many intraabdominal infections in humans, but its role as a pathogen is not clear.16... 

Intraabdominal infections have a wide spectrum of clinical features. Peritonitis usually is easily recognized, but intraabdominal abscess often may continue for long periods of time. Patients with primary and secondary peritonitis present quite differently. 

Because of the diverse bacteria present in the GI tract, secondary intraabdominal infections are often polymicrobial.12 The mean number of different bacterial species isolated from infected intraabdominal sites ranged from 2.9 to 3.7, including an average of 1.3 to 1.6 aerobes and 1.7 to 2.1 anaerobes.13 14... 

The treatment of intraabdominal infection most often requires the coordinated use of three major modalities (1) prompt drainage, (2) support of vital functions, and (3) appropriate antimicrobial therapy to treat infection not eradicated by surgery. Antimicrobials are an important adjunct to drainage procedures in the treatment of secondary intraabdominal infections however, the use of antimicrobial agents without surgical intervention usually is inadequate. For most cases of primary peritonitis, drainage procedures may not be required, and antimicrobial agents become the mainstay of therapy. 

In the early phase of serious intraabdominal infections, attention should be given to preserving major organ system function. With generalized peritonitis, large volumes of intravenous (IV) fluids are required to maintain intravascular volume, to improve cardiovascular function, and to ensure adequate tissue perfusion and oxygenation. Adequate urine output should be maintained to ensure appropriate fluid resuscitation and to preserve renal function. A common cause of early death is hypovolemic shock caused by inadequate intravascular volume expansion and tissue perfusion. 

An additional important component of therapy is nutrition. Intraabdominal infections often involve the GI tract directly or disrupt its function (paralytic ileus). The return of GI motility may take days, weeks, and occasionally, months. In the interim, enteral or parenteral nutrition as indicated facilitates improved immune function and wound healing to ensure recovery. 

Many studies have been conducted evaluating or comparing the effectiveness of antimicrobials for treatment of intraabdominal infections. Substantial differences in patient outcomes from treatment with a variety of agents generally have not been demonstrated. 

Important findings from the last 20 years of clinical trials regarding selection of antimicrobials for intraabdominal infections are... 

Five to seven days of antimicrobial treatment are sufficient for most intraabdominal infections of mild to moderate severity. 

Intraabdominal infection presents in many different ways and with a wide spectrum of severity. The antibiotic regimen employed and duration of treatment depend on the specific clinical circumstances (i.e., the nature of the underlying disease process and the condition of the patient). 

Table 74—2 presents the recommended agents for treatment of community-acquired and complicated intraabdominal infections from the Infectious Diseases Society of America and the Surgical Infection Society.21-23 These recommendations were formulated using an evidence-based approach. Most community-acquired infections are mild to moderate, whereas health care-associated infections tend to be more severe and difficult to treat. Table 74-3 presents guidelines for treatment and alternative regimens for specific situations. These are general guidelines there are many factors that cannot be incorporated into such a table. 

When used for intraabdominal infection, aminoglycosides should be combined with agents that are effective against the majority of B. fragilis. Clindamycin or metronidazole is the agent of first choice, but others, such as antianaerobic cephalosporins (e.g., cefoxitin, cefotetan, or ceftizoxime), piperacillin, mezlocillin, and combinations of extended-spectrum penicillins... 

TABLE 74-2. Recommended Agents for the Treatment of Community-Acquired Complicated Intraabdominal Infections... 

TABLE 74-3. Guidelines for Initial Antimicrobial Agents for Intraabdominal Infections... 

If symptoms do not improve, the patient should be evaluated for persistent infection. There are many reasons for poor patient outcome with intraabdominal infection improper antimicrobial selection is only one. The patient maybe immunocompromised, which decreases the likelihood of successful outcome with any regimen. It is impossible for antimicrobials to compensate for a nonfunctioning immune system. There may be surgical reasons for poor patient outcome. Failure to identify all intraabdominal foci of infection or leaks from a GI anastomosis may cause continued intraabdominal infection. Even when intraabdominal infection is controlled, accompanying organ system failure, most often renal or respiratory, may lead to patient demise. 

The outcome from intraabdominal infection is not determined solely by what transpires in the abdomen. Unsatisfactory outcomes in patients with intraabdominal infections may result from complications that arise in other organ systems. A complication commonly associated with mortality after intraabdominal infection is pneumonia.26 A high APACHE (Acute Physiology And Chronic Health Evaluation) II score, a low serum albumin, and a high New York Heart Association cardiac function status were significantly and independently associated with increased mortality from intraabdominal infection.27... 

Treatment regimens for intraabdominal infection can be judged as successful if the patient recovers from the infection without recurrent peritonitis or intraabdominal abscess and without the need for additional antimicrobials. A regimen can be considered unsuccessful if a significant adverse drug reaction occurs, reoperation or percutaneous drainage is necessary, or patient improvement is delayed beyond 1 or 2 weeks. 

Burnett RJ, Haverstock DC, Dellinger EP, et al. Definition of the role of enterococcus in intraabdominal infection Analysis of a prospective randomized trial. Surgery 1995 118 721-723. 

Marshall JC, Innes M. Intensive care unit management of intraabdominal infection. Crit Care Med 2003 31 2228-2237. 

Mazuski JE, Sawyer RG, Nathens AB, et al. The Surgical Infection Society guidelines on antimicrobial therapy for intraabdominal infections An executive summary. Surg Infect 2002 3 161-174. 

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