Surgical infections increase mortality, LOS

Synopsis: Surgical patients who became infected during hospitalization had increased in-hospital mortality rates, longer length of stay, and required additional professional care after discharge compared to noninfected patients.

Source: DiPiro JT, et. Al. Infection in surgical patients: Effects on mortality, hospitalization, and post-discharge care. Am J Health-Syst Pharm 1998; 55:777-781.

This study involved 90 nongovernment, nonspeciality, teaching and nonteaching acute care hospitals with more than 100 beds. Over 288,906 patients were available in the database that included patients of all ages hospitalized between July and September 1994. From that database, 12,384 patients who had undergone procedures likely to pose a moderate to high risk of infection were selected.

Of the 12,384 patients studied, 1479 (11.9%) had an infection during hospitalization. Infection rates ranged from 1.9% to 25.4%, depending on the procedure. The in-hospital mortality rate was 14.5% for infected patients vs. 1.8% for noninfected patients. Similarly, length of stay in infected patients (median, 14 days) was substantially greater than in noninfected patients (median, 4 days). About 24% of infected patients required additional professional care after discharge, compared with 7% of noninfected patients.

Comment by Thomas Schleis, MS, RPh, director of pharmacy services, Infections Limited, Tacoma, WA.

Despite advancements in surgical techniques and the use of prophylactic antimicrobials, infections still occur and are responsible for increased complications, length of stay, morbidity, and health care costs.

Not surprisingly, infections are most prevalent in patients undergoing moderate-to-high-risk surgeries. Patients with the highest mortality were those undergoing cholecystectomy, colerectal, upper digestive tract, and laparotomy procedures.

DiPiro and associates also noted that patients with surgical infections were less likely to be discharged home for self-care and more likely to require post-discharge care.

It is evident from this article that, in addition to the procedures implemented to reduce the potential for infection such as infection-control procedures, prophylactic antimicrobials, and sterile surgical techniques, there is still considerable potential for further reductions in surgical infections.

There needs to be a better understanding of the sources of contamination and ways to prevent it or to better deal with it at the time of contamination. Obviously, the high-risk surgeries are inherently "dirty," but once specific circumstances or procedures can be correlated with surgical infection, methods of prevention can be implemented.

It is unfortunate that this article did not look at the prophylactic antimicrobials used to determine if certain antimicrobials were more effective than others in reducing infection. Certainly that is another area that would be worth examining. n

Climo MW, Israel DS, Wong ES, et al. Hospital-wide restriction of Clindamycin: Effect on the incidence of Clostridium difficile-associated diarrhea and cost. Ann Intern Med 1998; 128:989-995.

Hospital formulary restriction of clindamycin can decrease the number of infections due to C. difficile and help restore susceptibility patterns in nosocomial isolates, but anticipated cost savings were somewhat offset by use of other antimicrobials, the authors report.

They found that restricting the use of clindamycin led to increased use of several other antibiotics with anti-anaerobic activity including, impenem, cefotetan, ticarcillin-clavulanate, piperacillin, and metronidazole.

"Although the cost savings realized by our pharmacy after the restriction of clindamycin were offset by the costs associated with the use of other more expensive antibiotics, reduced costs associated with the substantial decrease in the frequency of C. difficile-associated diarrhea probably accounted for an overall savings to the hospital," they conclude.

Citing estimates that each episode of C. difficile-associated diarrhea adds $2000 to $5000 to the costs of health care, the authors projected that the program prevented 57 cases of C. difficile-associated diarrhea and resulted in a hospital savings of least $114 000.

A hospital wide requirement of approval by an infectious disease consultant for clindamycin use was put in place after an outbreak of C. difficile-associated diarrhea. The outbreak had led to increased use of the drug a high level of clindamycin resistance among nosocomial isolates. It continued despite the use of traditional infection control measures, including private rooms, handwashing, barrier devices, educational programs, and weekly environmental disinfection of patient rooms.

"Not until we restricted the use of clindamycin throughout the hospital did the number of cases of C. difficile-associated diarrhea diminish," the authors report.

After the intervention, investigators found a sustained reduction in the mean number of cases of C. difficile-associated diarrhea (11.5 cases/month compared with 3.3 cases/month, and an increase in clindamycin susceptibility among C. difficile isolates (9% compared with 61%). In the hospital environment, widespread clindamycin use may confer a selective advantage for persistence and spread of clindamycin-resistant C. difficile, they note. Conversely, a reduction in the use of clindamycin would decrease that selective advantage.

The findings follow other recent studies indicating that antibiotic restriction can profoundly affect the antimicrobial susceptibilities of nosocomial pathogens. For example, decreased resistant among Enterobacter cloacae and Pseudomonas aeruginosas has also been found after restriction of third-generation cephalosporins and imipenem, they conclude.t

Aberhoff F, Mahoney F, Coleman P, et al. Immunogenicity of hepatitis B vaccines: Implications for persons at occupational risk of hepatitis B virus infection. Am J Prev Med 1998; 15:1-8

Hepatitis B vaccines are highly immunogenic, but have decreased immunogenicity associated with increasing age, obesity, smoking, and male gender; and among older adults, the presence of a chronic disease, the authors found. Hepatitis B vaccines should be administered to persons at occupational risk for HBV infection early in their career, preferably while they are still in their training, they emphasized.

They conducted a randomized clinical trial and decision analysis to assess risk factors for decreased immunogenicity among adults vaccinated with hepatitis B vaccine and to determine the importance of differences in immunogenicity between vaccines among health care workers.

Overall, 88% of health care workers developed immunity. Risk factors associated with failure to develop immunity included increasing age, obesity, smoking, and male gender. Presence of a chronic disease was associated with lack of immunity only among persons greater than or equal to 40 years of age. Among health care workers greater than or equal to 40 years of age, the decision analysis found 44 (0.34/100,000 person-years) excess chronic HBV infections over the working life of the cohort associated with use of the less immunogenic vaccine compared to the other.

Increasing age, a nonmodifiable risk factor, was the most important determinant for non-response to vaccination. The study continues to highlight the problems associated with vaccinating health care workers late in their career, they conclude.

"Not only is there a greater likelihood that an individual will not respond to vaccination, but it has been difficult to get older health care workers vaccinated," they note

The greater occurrence of occupationally acquired HBV infection early in a health care workers career coupled with the lower immunogenicity associated with vaccinating older adults, serve only to reinforce the long-standing recommendations that persons at occupational risk for be immunized early.t

Horn DL, Zabriskie JB, Austrian R, et al. Why have Group A streptococci remained susceptible to penicillin? Report on a symposium. Clin Infect Dis 1998; 26:1,341-1,345.

In spite of 50 years of extensive use of penicillin, Group A streptococci remain exquisitely susceptible to the antibiotic, the authors, note, reminding that this continuing susceptibility has occurred despite the development of resistance to other antimicrobial agents.

Among the most likely explanations for this remarkable state of continued susceptibility to penicillin are that B-lactamase may not be expressed or may be toxic to the organism and/or that low-affinity penicillin-binding proteins either are not expressed or render organisms non-viable, they conclude.

Other potential explanations are that circumstance favorable for the development of resistance have not yet occurred and/or that there are inefficient mechanisms for or barriers to genetic transfer. Recommended future actions include additional laboratory investigations of gene transfer, penicillin-binding proteins, virulence factors, and increased surveillance for the development of penicillin resistance.

"Thus far, the susceptibility of Group A streptococci to penicillin has not been a major clinical or epidemiological problem," the authors conclude. "A similar observation, however, could have been made decades ago about Streptococcus pneumoniae. It is therefore vital for the scientific community to closely examine why penicillin has remained uniformly highly active against group a streptococci in order to maintain this desirable state."

The authors cite reports of significant numbers of erythromycin-resistant Group A streptococci, particularly in Japan and Finland. Resistance has also been seen to sulfadiazine, tetracycline, and clindamycin. In addition, resistance to penicillin occurs in other closely related species of gram-positive organisms.

"Group a streptococci have remained susceptible to penicillin for the first 50 years of the antibiotic era," the authors conclude. "There is no guarantee that they will remain susceptible for the next 50 years. In view of the value of this antibiotic for treating infections due to group a streptococci in a cost-effective manner, the scientific community should continue to examine this issue closely. It has important pathogenetic as well as clinical and public health relevance."n