Risk of infection after penetrating abdominal trauma

Association of transfusion with postoperative bacterial infection

Homologous blood transfusion has been implicated as a modulator of the host immune system in a number of clinical settings. Improved renal allograft survival is observed in patients receiving pretransplant transfusions. Decreased recurrence of active inflammatory bowel disease has been recently reported in transfused patients with Crohn's disease. Conversely, deleterious immunomodulatory effects of transfusion may explain the association between transfusion and increased susceptibility to cancer recurrence and bacterial and viral infection. Clinical studies regarding cancer recurrence and transfusion are retrospective and conflicting. There is epidemiologic evidence for more rapid progression of HIV-1 infection in heavily transfused patients. Studies on transfused surgical patients have shown transfusion to be associated with an increased frequency of postoperative bacterial infections. Some studies have come to different conclusions. These investigators have suggested that transfusion may represent a surrogate marker for other risk factors for infection. Animal models designed to control for confounding factors have supported an association between transfusion and bacterial infection severity in most, but not all, reports. Attempts to define the immunologic alterations associated with transfusion have revealed a generalized impairment of cellular immunity in both humans and animals. Although the preponderance of data supports an association between perioperative transfusion and increased susceptibility to postoperative bacterial infection, it is not certain to what extent this relationship constitutes cause and effect.

In vitro comparison of cefoperazone/sulbactam with selected antimicrobials against 300 bacteroides isolates. Inhibitory activity and time-kill kinetic studies

The susceptibilities of 258 Bacteroides fragilis group isolates and 42 other Bacteroides species isolates against cefoperazone, cefoperazone/sulbactam (2:1 ratio) and selected other antimicrobials were determined by broth microdilution method. All isolates were susceptible to cefoperazone/sulbactam, ampicillin/sulbactam, ticarcillin/clavulanate, metronidazole, and imipenem. Other antibiotics showed variables levels of resistance (5-30%). Killing curves with the cef/sulb against selected B. fragilis group isolates were performed and showed excellent bactericidal activity at two to four times the minimum inhibitory concentration (MIC) after 12 hr incubation, even against the isolates with high cefoperazone MICs (greater than or equal to 64 micrograms ml). There was no regrowth at 24 hr. Cefoperazone/sulbactam is a compound with excellent inhibitory and bactericidal activity against B. fragilis group isolates.

The treatment of intraabdominal infections in surgery

Intraabdominal sepsis is frequently seen following penetrating or blunt abdominal trauma as well as with perforated appendicitis or diverticulitis. The initial leakage of endogenous gastrointestinal microflora into the peritoneal cavity results in peritonitis and secondary septicemia, which often results in a localized intraabdominal abscess. These infections are commonly polymicrobial and correlate directly with the unique endogenous microflora at various levels of the gastrointestinal tract. The successful treatment of intraabdominal sepsis is primarily associated with prompt, appropriate surgical intervention. Parenterally administered antibiotics are also required to decrease the incidence of local bacterial infection or septicemia. The choice of the appropriate agent(s) to be used initially, before obtaining the results of culture and sensitivity tests, depends primarily on both the clinical presentation and on whether the intraabdominal infection occurred in the community or as a result of hospitalization. Clinical and experimental studies of intraabdominal sepsis have primarily emphasized the use of antibiotic agents that have a spectrum of activity effective against aerobic coliforms and the anaerobe Bacteroides fragilis.

Antibiotic prophylaxis in surgery

Scientific studies conducted during the last 10 years have resulted in a great improvement of our approach to the appropriate use of prophylactic antibiotics in the surgical patient. Errors of the past including faulty timing of the initial dosage as well as prolonged duration of prophylaxis have largely been remedied. Present studies are designed to define the patients within the various subsets of diseases or surgical procedures who are at greatest risk of infection. It is these patients who can be expected to benefit most from the efficacious use of prophylactic antibiotics as well as other preventative measures.

Postoperative infection prophylaxis for upper gastrointestinal tract surgery--a prospective and comparative randomized study of cefoxitin and ceftizoxime

A prospective and randomized clinical study was conducted in order to compare cefoxitin (CFX) and ceftizoxime (CZX) as prophylactic antibiotics. Two hundred and three consecutive cases of elective upper gastrointestinal tract surgery, performed at our institute between January, 1983, and March, 1986, were entered in the trial. The patients were assigned randomly, before surgery, to the CFX or to the CZX group. Two grams of the assigned antibiotic was first administered during surgery and then continued at a dose of 1 gram, every 8 hrs for a total of 4 days. One patient was withdrawn from the study due to an allergic reaction. Both groups were comparable in sex, age, underlying disease, diagnosis, operation, and preoperative laboratory data. There were 18 infections related to the operation in the CFX group, while there were only 3 in the CZX group (p less than 0.001). The number of unrelated infections in each group was 6 and 6 respectively (NS). No special differences were found between the two groups regarding the kinds of microorganisms isolated, and no significant differences were seen in the adverse effects of either antibiotic. Our study demonstrated that ceftizoxime was more efficient than cefoxitin in preventing postoperative infection, following upper gastrointestinal tract surgery.

Antibiotics for penetrating abdominal trauma: a prospective comparative trial of single agent cephalosporin therapy versus combination therapy

In this prospective, comparative study, 129 patients who sustained penetrating abdominal trauma were randomized to receive preoperatively, and for 3-5 days postoperatively, one of three antibiotic regimens: Group I--cefotaxime (CTX) (2 Gm Q8H), Group II--cefoxitin (2 Gm Q6H), or Group III--clindamycin (900 mg Q8H) and gentamicin (3-5 mg/kg/day in divided doses Q8H). The three groups were similar in terms of the following: age, sex, severity of injury, number of organs injured, colon injuries, shock, blood transfusions, or positive intraoperative cultures. Septic complications occurred as follows: Group I--6.9%, Group II--2.3%, and Group III--6.9%. The three regimens ranked as follows in terms of therapy costs: CTX less than cefoxitin less than clindamycin and gentamicin. It is concluded that single agent therapy with a cephalosporin is preferable to combination therapy on the basis of equivalent effectiveness, lower toxicity, and lower costs.

Immunosuppressive effects of blood transfusion in anaesthesia and surgery

The immunosuppressive effects of blood transfusion at surgical operations become manifest as enhanced graft survival, increased cancer recurrence and decreased patient survival, and increased susceptibility to postoperative infections. Blood transfusion in transplant recipients no longer offers this advantage when cyclosporine A is used. The deleterious effects of blood transfusion on the prognosis of some cancers found in the statistical analyses of retrospective studies are considered to be of increasing clinical importance. Therefore, unnecessary blood transfusions should be avoided and special attention directed to the use of autologous blood. Leucocyte-free red blood concentrates are the least immunosuppressive homologous blood preparations. Conventional red blood cell concentrates may also be used in cancer patients until ongoing prospective randomized studies confirm that there is a true association between the use of homologous blood and increased recurrence of cancer.

Colorectal trauma

Colorectal injury remains a source of significant morbidity and mortality. Gunshot and stab wounds are the most common etiologic agents. Diagnosis is usually established on clinical grounds. For the purposes of management, the large bowel can be considered as colon and rectum. Minor colon injuries can be repaired primarily; management of major colon injuries or injuries associated with multiple organ involvement, significant blood loss, or massive contamination should be individualized. Diversion or exteriorization remains the gold standard of treatment when there is any doubt. Rectal injury should be repaired when feasible and diverted and the presacral space drained. Distal rectal washout is of proven merit. Antibiotics provide an important adjunct to therapy. They should be initiated early (preoperatively), ended quickly (12 to 72 hours postoperatively), and provide a broad spectrum of coverage. The treatment of established infection should be guided by bacterial culture. Postoperatively, aggressive support is important for a good outcome. The significant incidence of complications even in the face of optimal management demands continued vigilance and aggressive intervention by the operating surgeon.

More is better. Antibiotic management after hemorrhagic shock

Previous reports suggest that standard antibiotic prophylaxis is ineffective in reducing the incidence of wound infection after hemorrhagic shock. This study investigated the use of larger and longer doses of antibiotic in a model of staphylococcal infection after hemorrhagic shock. Sprague-Dawley rats resuscitated from hemorrhagic shock were injected with either 10(6), 10(8) or 10(10) Staphylococcus aureus subcutaneously. Five treatments were investigated: 1) control (no antibiotic), 2) short-course cefazolin (CEF) (SHORT), 30 mg/kg intraperitoneal (IP), 30 minutes before and 4 hours after inoculation, 3) long-course CEF (LONG), 30 mg/kg IP, 30 minutes before and 4 hours after inoculation, and thereafter, every 8 hours for 3 days, 4) mega-CEF (MEGA) 200 mg/kg IP, 30 minutes before and 4 hours after inoculation, and 5) mega-long CEF (MEGA-LONG), 200 mg/kg IP, 30 minutes before and 4 hours after inoculation, and thereafter, every 8 hours for 3 days. Abscess number, weight, and diameter were measured on Day 7. At the 10(6) inoculum, SHORT was effective in both shocked and unshocked animals. In the 10(10) group, all antibiotic regimens decreased the 100% mortality that followed shock without treatment, but they had little effect on abscess formation. In unshocked rats at the 10(8) inoculum, SHORT was effective in reducing abscess number, diameter, and weight (all p less than 0.05 vs. control). After hemorrhagic shock, SHORT did not decrease abscess frequency, but it did diminish abscess diameter. LONG significantly decreased abscess diameter and abscess weight (both p less than 0.05). After shock, both MEGA and MEGA-LONG reduced abscess number (p less than 0.05 vs. control) and MEGA-LONG was superior to all other regimens at the 10(8) inoculum. These experimental data show that increasing both the dose and duration of antibiotic administration is more effective than standard short-course antibiotic prophylaxis in preventing experimental infection after hemorrhagic shock.

Blood transfusion and infectious complications following colorectal cancer surgery

Blood transfusion has been linked to clinical phenomena attributable to immune suppression. We prospectively studied the relationship between perioperative blood transfusion and postoperative infectious complications in 343 consecutive patients undergoing surgery for colorectal cancer. Of the 134 patients who received transfusions 33 (24.6 per cent) developed infectious complications compared with 9 (4.3 per cent) of the 209 patients who did not receive blood (P less than 0.0001). The mean number of units of blood received by patients who developed infectious complications significantly exceeded the number for patients without infectious complications (2.31 versus 0.74, P less than 0.0001). The association of transfusion with infections was highly significant (P less than 0.0001) after controlling for age, sex, blood loss, procedure, tumour differentiation, stage, admission haematocrit, duration of surgery, length of the specimen and tumour size. Blood transfusion appears to be an independent risk factor for postoperative infectious complications.

Interferon-gamma restores immune competence after hemorrhagic shock

Hemorrhagic shock increases the susceptibility to infection in both clinical and laboratory settings. Hemorrhagic shock also is associated with a decreased production of interferon-gamma (IFN-gamma), a potent modulator of immune function. We investigated the effect of IFN-gamma both alone and in addition to antibiotic prophylaxis upon infection following hemorrhagic shock. Sprague-Dawley rats were bled to a mean arterial pressure of 45 mm Hg for 45 min and then were resuscitated with shed blood and normal saline. Abscess formation was induced 1 hr later by subcutaneous injection of 1 X 10(8) Staphylococcus aureus. Four treatments were investigated: (1) control; (2) recombinant rat IFN-gamma, 7500 units, 30 min after inoculation and daily for 3 days; (3) cefamandole (CEF) nafate, 30 mg/kg, 30 min before and 4 hr after inoculation; and (4) IFN-gamma + CEF as in (2) and (3). Abscess size, weight, and quantitative bacterial counts were measured 7 days after inoculation. Hemorrhagic shock increased mean abscess size from 11.7 +/- 2.8 to 14.1 +/- 1.9 mm (P less than 0.05), in untreated rats. IFN-gamma alone resulted in minor changes in abscess formation in both shocked and unshocked animals. Shock rendered CEF ineffective in reducing abscess size. IFN-gamma + CEF significantly reduced abscess size (14.1 +/- 1.9 to 8.1 +/- 1.8 mm) and weight (771 +/- 214 to 252 +/- 132 mg) and decreased bacterial count after shock to 12% of control (all P less than 0.05). These data demonstrate that hemorrhagic shock impairs antibiotic efficacy; however, the addition of IFN-gamma restores the ability of host defenses to combat bacterial infection.

Management of infection following intra-abdominal trauma

Intra-abdominal infections following abdominal trauma often involve the gastrointestinal aerobic and anaerobic bacterial flora. These organisms possess various virulence factors and exhibit potential synergy between them. The intra-abdominal infection is biphasic, with the Enterobacteriaceae as the major pathogens in the peritonitis stage, and the Bacteroides fragilis group predominant in the abscess stage. Experiments with animals and experience in human beings support the need to use single or combined antimicrobial agent therapy that is effective against both Enterobacteriaceae and the B fragilis group.

The gut as source of sepsis after hemorrhagic shock

In a model of severe hemorrhagic shock in rats, blood culture findings became positive within 2 to 4 hours of shock. The organisms cultured were primarily gram-negative. To test the hypothesis that the gut was the source of the bacteria, E. coli labeled with carbon-14 oleic acid were fed to rats undergoing hemorrhagic shock. Their plasma was then assayed for carbon-14 activity. Seven of the 14 shocked animals demonstrated increased plasma carbon-14 activity during or after shock. The mortality rate was 100 percent 80 hours postshock, and all animals had E. coli on subsequent blood culture. The seven rats without increased plasma carbon-14 activity had a survival rate of 83 percent postshock. Sham-shocked animals did not exhibit plasma carbon-14 levels greater than the background levels. These data suggest that bacterial translocation occurs during hemorrhagic shock and that the gut is the source of the bacteremia seen during hemorrhagic shock.

Prophylactic antibiotics in traumatic wounds

There is well-documented evidence justifying, perhaps demanding, the obligatory use of early, anticipatory treatment in open fractures and in penetrating abdominal wounds, and equally convincing evidence that they are not indicated in fractures of the base of the skull with CSF leaks, in thermal injuries, or in simple lacerations. As far as penetrating chest wounds, and bites are concerned, the evidence is perhaps as yet inconclusive, but antibiotics are probably not indicated in these situations.

Relationship of postoperative septic complications and blood transfusions in patients with Crohn's disease

We prospectively studied 169 patients with Crohn's disease to determine if postoperative infectious complications could be related to perioperative blood transfusions. Postoperative septic complications developed in 18 of the 69 patients who received more than 1 unit of blood (26 percent) compared with 8 of the 100 patients (8 percent) who received 1 unit of blood or no blood (p = 0.0014). Previous operation, low body weight, and having an ostomy were also related to septic complications. Patients receiving more than 1 unit of blood were significantly more likely to have low preoperative serum albumin levels, to have undergone abdominoperineal or small bowel resection, and to have an ostomy. Postoperative septic complications were significantly related to perioperative blood transfusions after controlling for these potential confounding factors independently by subgrouping and simultaneously by using multiple logistic regression. Blood transfusion may be a more significant factor in postoperative immune suppression and susceptibility to infection than previously recognized.

Activity of newer beta-lactam agents against clinical isolates of Bacteroides fragilis and other Bacteroides species

The in vitro activities of beta-lactam antibiotics against Bacteroides fragilis and B. fragilis group isolates are presented. Clinical isolates from 1986 were compared with strains from 1979 to 1982. Imipenem, ticarcillin-clavulanic acid, and ceftizoxime were the most active agents. Cefotetan was equivalent to cefoxitin against B. fragilis but less active against B. fragilis group isolates. Enhancement of cefotaxime by its desacetyl metabolite was minimal.

Antimicrobial prophylaxis of gastrointestinal surgical procedures and treatment of intraabdominal infections

Antibiotic prophylaxis and treatment regimens ideally are selected on the basis of efficacy, safety, and cost. This review evaluates current, selected literature on antibiotic prophylaxis for colorectal surgery, presumptive antibiotic administration following penetrating abdominal trauma, and treatment of intraabdominal infections. Single-drug regimens with the newer, broad-spectrum agents are assessed and compared with combination regimens; specific regimens are recommended. Colorectal procedures require an antimicrobial agent with activity against both aerobes and anaerobes. Patients undergoing elective colorectal procedures can be adequately protected with an orally administered three-dose regimen of neomycin/erythromycin. Parenteral antibiotic administration is generally not necessary, but, cefoxitin is recommended for nonelective colorectal surgery. The risk of potential infectious complications following penetrating abdominal trauma without colonic perforation is less than with colonic perforation; however, antibiotic therapy that includes activity against aerobes and anaerobes is recommended for all types of penetrating abdominal trauma. Although cephalothin, cefamandole, or cefoxitin alone may be used in abdominal trauma without perforation of the colon, only cefoxitin is recommended as a single-drug alternative to the standard clindamycin/gentamicin regimen in trauma with colonic perforation. Single-drug therapy with cefoxitin or moxalactam can be used successfully as alternatives to the standard regimens of clindamycin/gentamicin or metronidazole/gentamicin in many patients with intraabdominal sepsis. Single-drug regimens reduce the risk of developing adverse effects and are cost-effective. However, if resistant organisms are suspected, or if the patient has been hospitalized for a prolonged period or has multiple organ failure, it may be necessary to supplement cefoxitin therapy with an antibiotic that will enhance coverage against gram-negative aerobes.

Single agent cephalosporin prophylaxis for penetrating abdominal trauma. Results and comment on the emergence of the enterococcus

Multiple studies have shown that the incidence of infectious complications after penetrating abdominal wounds are decreased by the perioperative administration of antibiotics. In this study of three separate single cephalosporin agents (cefotaxime, cefoxitin, and moxalactam) given for a 48 hour period in patients who sustained perforating gastrointestinal wounds, uncomplicated recoveries occurred in 93 percent of all patients. The rates of uncomplicated recovery were significantly different for the three groups; however, patients with major intraabdominal vascular injuries were more common in the cefoxitin-treated group. One disturbing feature was the presence of enterococci in 57 percent of isolates from wound infections and 60 percent of isolates from intraabdominal abscesses. Enterococci as sole isolates were found in one of two wound infections and three of four intraabdominal abscesses in the moxalactam-treated group.

Cost-effective choice of antimicrobial therapy for serious infections

The authors evaluated the financial and health implications of treatment choices for three serious classes of infection: hospital-acquired pneumonia, intra-abdominal infection, and sepsis of unknown origin. Data were obtained from a systematic review of clinical literature and published data bases, by written questionnaire from a panel of infectious disease authorities, and from actual costs at a tertiary-care hospital. For pneumonia and sepsis, the third-generation cephalosporin evaluated (ceftizoxime) was found to be less expensive than other regimens, when costs of dose preparation and administration, monitoring, and toxicity were added to drug acquisition costs. The lowest-cost regimen for intra-abdominal infection was metronidazole plus gentamicin. Modest differences in efficacy would easily outweigh differences in toxicity, however, and could justify the use of more expensive regimens (e.g., mezlocillin plus gentamicin for hospital-acquired pneumonia, and cefoxitin plus gentamicin for intra-abdominal infection). If all regimens are assumed to be equally efficacious, then the third-generation cephalosporin was both lowest in cost and, owing to its low toxicity, greatest in net health benefit.

Perioperative blood transfusion associated with infectious complications after colorectal cancer operations

We prospectively studied 168 consecutive patients with colorectal cancer to identify perioperative determinants of infectious complications. All patients received preoperative bowel preparation with laxatives, enemas, oral neomycin and erythromycin base, and intravenous cefazolin. Age, sex, admission hematocrit value, operative procedure, specimen length, duration of operation, blood loss, transfusions, tumor size, tumor differentiation, nodal status, and Dukes' stage were evaluated in relation to infectious complications using multivariate analysis. Infectious complications developed in 24 of the 168 patients in the study (14 percent) and these accounted for the four deaths. Blood transfusion (p = 0.0100) and admission hematocrit value (p = 0.0191) were significantly related to postoperative infectious complications. Low admission hematocrit values appeared to protect patients from infectious complications. Patients who had postoperative infectious complications received 2.14 +/- 2.75 units of blood compared with 0.82 +/- 1.37 units in patients without infectious complications (p = 0.0005). Although blood transfusion was associated with high operative blood loss, prolonged procedures, and large specimens (p less than 0.005), none of these factors was significantly associated with infectious complications (p greater than 0.10). Blood transfusion is immunosuppressive in other clinical situations and may be a more significant factor affecting postoperative immune function and susceptibility to infectious complications than previously recognized.

Immunologic effects of blood transfusion upon renal transplantation, tumor operations, and bacterial infections

Blood transfusions appear to exert a suppressive effect on many aspects of the immune system. In transplantation, this has been used to advantage; in other areas, the consequences can be deleterious. It is likely that various components of the immune system are affected by different mechanisms and possibly by different components of transfused blood. Before rational strategies can be evolved for minimizing the deleterious effects of blood transfusions, it is essential that these mechanisms be clearly defined. Studies must take into account any influence the underlying disease state might have on the immune system. In the absence of any satisfactory substitute, blood transfusion remains an essential therapeutic modality in the management of surgical patients. With current evidence, however, it seems reasonable to avoid the administration of small-volume transfusions whenever possible and encourage the use of autodonated blood for elective surgery.

Prevention and management of enterococcal infection: cost implications

Enterococcal infections are becoming increasingly prevalent, in part because of the widespread use of cephalosporins and a greater number of immunosuppressed patients. Most infections where enterococci are isolated are pelvic or intraabdominal. The actual pathogenic role of the enterococcus remains controversial, since many types of organisms are usually cultured as well. Although specific therapy directed at the enterococcus may not always be necessary, reasonable indications for specific therapy include the presence of shock, immunosuppression, or persistent or recurrent infection. Enterococcal bacteremia is associated with a mortality rate in excess of 40 percent. This entity, as well as enterococcal endocarditis and meningitis, should be treated with bactericidal, combination antibiotic therapy, which includes a penicillin and an aminoglycoside. Mixed infections probably can be treated with a penicillin alone. Penicillin-allergic patients should be treated with vancomycin. The costs of nosocomial infection or superinfection are very high; costs incurred as a result of enterococcal infection or superinfection may be prevented by avoiding prolonged prophylactic or broad-spectrum therapeutic regimens (such as cephalosporins) that lack antienterococcal activity. Extended-spectrum penicillins may be effective prophylactic regimens for intraabdominal or pelvic procedures and should serve as adequate therapy for mixed infections in these sites.

Management of intra-abdominal sepsis

Intra-abdominal sepsis most frequently follows penetrating or blunt abdominal trauma or perforated appendicitis or diverticulitis. The initial leakage of the endogenous gastrointestinal microflora into the peritoneal cavity results in peritonitis and secondary septicemia, which is frequently followed by localized intra-abdominal abscess. These infections are most frequently polymicrobial and relate directly to the unique endogenous microflora at the various levels of the gastrointestinal tract. The treatment of intra-abdominal sepsis is primarily centered around prompt, appropriate surgical intervention. Parenterally administered antibiotics are also required to decrease the chance of local bacterial infection or septicemia. The choice of the appropriate agent(s) to be used initially, before the results of culture and sensitivity reports are available, depends primarily on the clinical presentation and also on whether the intra-abdominal infection occurred in the community or within the hospital setting. Clinical and experimental studies of intra-abdominal sepsis have largely stressed the use of antibiotic agents that have a spectrum of activity effective against the aerobic coliforms and anaerobic Bacteroides fragilis.

Selected overview of nongynecologic surgical intra-abdominal infections. Prophylaxis and therapy

True prophylaxis of intra-abdominal nongynecologic infections is limited to elective, nonemergency surgery and is best shown in three clean-contaminated surgical procedures. All of these have an infection rate of approximately 10 to 20 percent and include all colon resection surgery, most gastric surgery, and about one third of the cholecystectomies for chronic calculous cholecystitis. Each of these three surgical procedures has a somewhat different pattern of bacterial pathogens. The most useful comparative studies of early preoperative therapy have been performed in cases of suspected appendicitis (50 percent of which usually show perforation or gangrene at the time of surgery) and penetrating abdominal wounds (80 percent of which usually enter some part of the bowel and theoretically soil the peritoneum). These procedures are usually classified as contaminated, with a 20 to 30 percent infection rate, or dirty, with a more than 30 percent infection rate, depending upon several factors. Comparative investigations of intraoperative and postoperative antibiotic therapy of established intra-abdominal infections are more difficult to obtain because of the heterogeneity of the sites, organisms, and medical and surgical therapy. The initial pathogens causing secondary peritonitis and hepatic, perirectal, diverticular, and most other types of intraperitoneal abscesses are mixed coliforms and anaerobes, with emphasis on the anaerobes. Retroperitoneal abscesses, pancreatic abscesses, and biliary tract infections are predominantly caused by coliforms. The organisms responsible for these early infections are usually community-acquired rather than more antibiotic-resistant hospital-acquired bacteria. Considering the availability of a large number of effective broad-spectrum antibacterial agents and therapeutic combinations, it has become increasingly difficult to assess the rightful place of any new prospective antimicrobial regimen unless it has quite unique characteristics. Most empiric therapy in established intra-abdominal infection studies have compared gentamicin and clindamycin, the most popular regimen in the United States over the past 15 years, with a cephalosporin, broad-spectrum penicillin, or aminoglycoside, either alone or together with clindamycin or metronidazole. Results have usually been considered similar in most studies, although in some studies, agents with limited Bacteroides fragilis activity, such as cefamandole or cefaperazone, have been considered inferior. Most new prophylactic regimens have been compared with the first-generation cephalosporins and, again, similar results have been obtained between the groups with two exceptions. Cepha

Clinical prediction rules. Applications and methodological standards

The objective of clinical prediction rules is to reduce the uncertainty inherent in medical practice by defining how to use clinical findings to make predictions. Clinical prediction rules are derived from systematic clinical observations. They can help physicians identify patients who require diagnostic tests, treatment, or hospitalization. Before adopting a prediction rule, clinicians must evaluate its applicability to their patients. We describe methodological standards that can be used to decide whether a prediction rule is suitable for adoption in a clinician's practice. We applied these standards to 33 reports of prediction rules; 42 per cent of the reports contained an adequate description of the prediction rules, the patients, and the clinical setting. The misclassification rate of the rule was measured in only 34 per cent of reports, and the effects of the rule on patient care were described in only 6 per cent of reports. If the objectives of clinical prediction rules are to be fully achieved, authors and readers need to pay close attention to basic principles of study design.

Acute enteric sepsis: bacteriology and antibiotic cover

Most cases of enteric sepsis are caused by both aerobic and anaerobic organisms which form the normal flora of the mouth and lower gastrointestinal tract. This flora is extremely variable and subject to change due to disease and antimicrobial treatment. Bacteriological investigation of patients with severe enteric sepsis is important and should be undertaken before antibiotic treatment is commenced. The choice of antibiotics depends on the nature of the infection and its location. Initially they should be given in maximum dosage. If polymicrobial infection is suspected both aerobes and anaerobes should be covered to prevent bacteraemic shock and abscess formation. If abscesses have formed or the patient fails to respond to appropriate antibiotics, surgical exploration and drainage remain the treatment of choice. Antibiotics often fail to eradicate organisms from established abscesses and are responsible for some serious complications.

Role of amikacin in the management of intra-abdominal sepsis

Controversy has developed regarding the antibiotic management of intra-abdominal sepsis because of the recent availability of the third-generation cephalosporins and ureidopenicillins as alternatives to traditional combination therapy (aminoglycosides plus clindamycin). Most observers now acknowledge the need to provide anti-anaerobic as well as anti-aerobic gram-negative drug coverage. Although most of the newer agents do provide such broad-spectrum coverage, doubt remains regarding their efficacy because of flaws in comparative study design and the observation that resistance to the newer agents, which may even extend to the aminoglycosides, can emerge in individual patients during single courses of antibiotic therapy. Indeed, such resistance is most likely to occur during the treatment of seriously ill, immunodepressed patients who have undergone multiple reoperation for persistent or recurrent intra-abdominal sepsis--the precise group for which the new drugs were most desired as less toxic alternatives to the aminoglycosides. On the basis of such observations, combination therapy with the aminoglycosides, appears to remain the most logical choice. In the setting of nosocomial sepsis and pathogen resistance to other aminoglycosides, amikacin may be especially effective. Recent surveillance data indicate that the use of amikacin under such circumstances not only may provide effective antibiotic therapy, but also may actually reduce the level of microbial resistance to the other aminoglycosides. Past concern regarding the development of resistance to amikacin has probably been excessive and should not deter the use of this agent under appropriate clinical circumstances.

Adverse effect of splenectomy in experimental peritonitis

Patients undergoing splenectomy have increased operative morbidity and mortality, especially when associated with gastrointestinal surgery or injury. This present study was designed to assess the effect of splenectomy on mortality in a polymicrobial fecal peritonitis model and evaluate therapy with antibiotic (cefoxitin) or immunomodulation (glucan). Human stool-barium (0.15 cc) was placed in the peritoneum of Sprague-Dawley rats at the time of splenectomy or sham surgery. Splenectomy animals were then treated with 5% dextrose, cefoxitin (60 mg im q 6 hr), glucan (7.5 mg ip prior to surgery), or cefoxitin plus glucan. Splenectomy resulted in decreased survival (5% vs 30%, P less than 0.05). Treatment with cefoxitin (90%) or glucan (47%) significantly improved survival. Combined glucan-cefoxitin therapy had no improvement over cefoxitin alone. Peritoneal and blood cultures were performed 12 hr postoperatively. There were no significant differences in growth of bacteria between sham and splenectomy animals. Cefoxitin treatment resulted in lower growth of bacteria from both blood and peritoneum (P less than 0.05). Glucan treatment caused a significant decrease in the number of bloodborne bacteria (P less than 0.05). Intravascular colloidal carbon clearance and leucocyte counts were performed at 12 hr postoperatively. Presence of peritonitis significantly enhanced intravascular clearance, while splenectomy had no effect. Addition of glucan or cefoxitin therapy to splenectomy animals did not enhance intravascular clearance. Leucocyte counts were significantly lower (P less than 0.05) when splenectomy was added to peritonitis animals. Glucan and cefoxitin therapy did not increase leucocyte counts. Based on these studies we conclude that (1) splenectomy increases mortality in fecal peritonitis, (2) antibiotic and immunomodulator afford some protection, and (3) exact mechanism of protection remains unclear.

Evaluation of antibiotic therapy following penetrating abdominal trauma

Postoperative infection accounts for significant morbidity and mortality following penetrating abdominal trauma. During a 2 1/2-year period, December 1980 through June 1983, 257 patients sustaining penetrating abdominal injury were initially treated at Parkland Memorial Hospital in Dallas. Following the patient's written consent, they were prospectively randomized to receive, prior to surgery, intravenous clindamycin 600 mg every 6 hours and tobramycin 1.2 mg/kg every 6 hours (CT), or cefamandole 1 gm every 4 hours (M), or cefoxitin 1 gm every 4 hours (C). The antibiotics were continued for 48 hours. Major organ injuries in the three groups were comparable. The overall infection rate was significantly less in the cefoxitin group (13%), compared to cefamandole at 29%, and was comparable to the combination of clindamycin/tobramycin at 20%. The most significant difference followed colon injury. There were 96 patients who sustained colon injuries and the infection rate was CT 33%, M 62%, and C 19% (p = 0.002). If nonoperative wound infections were excluded from the colon group and only severe infections were evaluated, the infection rate was CT 18%, M 38%, and C 13% (p = 0.021). The infection rate was higher in the shock patients and tended to increase as age increased. Enterococcus, Escherichia coli, and Klebsiella pneumoniae were the most frequent aerobes isolated along with anaerobes. Five of six Bacteroides isolates from major infections occurred in the cefamandole group; two of which were in bacteremic patients. The hospital stay corresponded with infection rates, being 11.4 days (CT), 13.1 days (M), and 9.4 days (C). The results of this study indicate that cefoxitin is comparable to the combination of clindamycin/tobramycin and superior to cefamandole when used before surgery in patients sustaining penetrating abdominal trauma. The study suggests that antibiotic coverage should be against aerobes and anaerobes. Routine administration of an aminoglycoside is unnecessary.