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Therapeutics

Review: Selective decontamination of the digestive tract reduces respiratory tract infections in intensive care patients

ACP J Club. 1992 Jan-Feb;116:12. doi:10.7326/ACPJC-1992-116-1-012

Related Content in the Archives
• Selective decontamination of the digestive tract. An overview. Heyland DK, Cook DJ, Jaeschke R, et al. Chest. 1994; 105:1221-9.


Source Citation

Vandenbroucke-Grauls CM, Vandenbroucke JP. Effect of selective decontamination of the digestive tract on respiratory tract infections and mortality in the intensive care unit. Lancet. 1991 Oct 5;338:859-62.


Abstract

Objective

To assess the effect of selective decontamination of the digestive tract (SDD) on respiratory tract infections (RTI) and on survival of patients in the intensive care unit (ICU).

Data sources

MEDLINE was searched for the years 1984 through 1990, using keywords critically ill, intensive care unit, selective decontamination, infection, and cross-infection prevention. A relevant doctoral thesis was included.

Study selection

All comparative studies (some using historical controls) of antibiotic prophylactic regimens administered in the ICU to selectively eliminate gram-negative aerobic flora from the gastrointestinal tract were chosen (n = 11).

Data extraction

Information about prophylactic regimens, RTIs, and mortality was extracted. Studies were classified according to design (randomized, controlled trials or historical controls) and to early use of systemic cefotaxime for prevention of infection. Odds ratios (OR) were calculated for each study and then combined (COR) using meta-analysis of similar studies. 1 study was considered as both a randomized trial and as a nonrandomized study because findings were also compared with a historical control group.

Main results

In 6 studies with historical control groups, there were 183 RTIs among 998 patients. Fewer patients receiving decontamination developed RTIs compared with patients in the control groups {weighted experiental group event rate (EER) 3% vs weighted control group event rate (CER) 28%, P < 0.001. This weighted absolute risk reduction (ARR) of 25% means that 5 patients would need to be treated (NNT) with selective decontamination of the digestive tract (rather than the control procedure) to prevent 1 additional patient from developing a RTI; 95% CI 3 to 11; the relative risk reduction (RRR) was 75%, CI 51% to 87%.}* Mortality was not reduced by the decontamination regimen {weighted EER 23% vs weighted CER 26%, weighted ARR 3%, CI -3% to 9%, p = 0.4}.* There was no effect of decontamination on mortality for the 5 studies in which SDD with oral antibiotics was combined with systemic cefotaxime.

In 5 randomized trials and 1 trial with alternate allocation to treatment and control groups (491 patients with 138 RTIs and 116 deaths), RTIs were reduced by selective decontamination {weighted EER 7% vs weighted CER 45%, P < 0.001} {ARR 38%, RRR 79%, CI 65% to 88%, NNT 3, CI 2 to 8}.* There was no effect on mortality {weighted EER 23% vs weighted CER 26%, weighted ARR 3%, CI -10% to 4%, P = 0.4}.* In 3 trials in which cefotaxime was added to the antibiotic regimen (266 patients with 42 deaths) there was no effect of decontamination on mortality.

Conclusions

Selective decontamination of the digestive tract reduces respiratory tract infections in intensive care patients. For mortality, the trend suggesting benefit of active treatment did not reach statistical significance.

Source of funding: Not stated.

Address for article reprint: Dr. C.M. Vandenbroucke-Grauls, Department of Clinical Microbiology and Laboratory of Infectious Diseases, GO4.515, University Hospital, PO Box 85500, 3508 GA Utrecht, The Netherlands.

*Numbers calculated from data in article.

Selective decontamination of the digestive tract. An overview. Heyland DK, Cook DJ, Jaeschke R, et al. Chest. 1994; 105:1221-9.

Commentary

Nosocomial infection is a major problem in the ICU and is associated with an increased incidence of organ failure and death. Evidence suggests that the organisms responsible are those that colonize the gastrointestinal and respiratory tracts of susceptible hosts. Selective decontamination of the digestive tract is a technique designed to influence this colonization, suppressing the growth of potentially pathogenic aerobic gram-negative bacteria while allowing the continued presence of normal anaerobic bacteria in the gut. Although several investigators have reported a decrease in respiratory infections, only 2 have reported a significant decrease in mortality. One explanation for their failure to show a decrease in mortality is a sample size insufficient to detect a difference if it truly exists. Vandenbroucke-Grauls and Vandenbroucke attempted to circumvent this problem using meta-analysis, which increases the power and improves the precision and accuracy of the estimated treatment effect.

This meta-analysis fails to show a difference in mortality, but does show a difference in respiratory infection rates favoring treatment. Thus, the synthesis of the 11 available studies does not differ significantly from conclusions of most of the original studies.

Some issues remain unresolved. Why does a reduction in nosocomial pneumonia not reduce mortality? Is nosocomial pneumonia a sign of critical illness rather than a cause? Is there a larger effect of SDD in subgroups of critically ill patients, which is obscured by the heterogeneous population of patients included in the meta-analysis? Some studies suggest that patients with trauma or reversible immunosuppression may do better with SDD. Are the most appropriate antibiotics being used in the SDD regimen and being administered by the most appropriate route? Clearly, to answer these questions, large, double-blinded, randomized trials that include specific patient populations and have mortality as an end point must be done. Until then, physicians should use their judgment in interpreting the best available summary of evidence, such as that provided in this analysis.

Derek C. Angus, MB, ChB
Michael R. Pinsky, MD
University of PittsburghPittsburgh, Pennsylvania, USA

Derek C. Angus, MB, ChB
University of Pittsburgh
Pittsburgh, Pennsylvania, USA

Michael R. Pinsky, MD
University of Pittsburgh
Pittsburgh, Pennsylvania, USA