Selective decontamination of digestive tract in intensive care.

Abstract

Evert de Jonge and colleagues (Sept 27, p 1011)1de Jonge E Schultz MJ Spanjaard L et al.Effects of selective decontamination of digestive tract on mortality and acquisition of resistant bacteria in intensive care: a randomised controlled trial.Lancet. 2003; 362: 1011-1116Summary Full Text Full Text PDF PubMed Scopus (492) Google Scholar believe they have proven that selective decontamination of the digestive tract (SDD) of patients in intensive care units (ICUs) significantly improves hospital survival, and lowers the rate of acquisition of resistant gram-negative aerobic bacteria. Unfortunately, the design and execution of the study do not allow such conclusions to be drawn. By contrast with their statement, the study was neither randomised nor well controlled. They essentially compared the performance (ie, the rates of hospital mortality and resistance acquisition) of two separate ICUs—in one of which, SDD was introduced for 2.3 years, whereas in the other it was not. Since de Jonge and colleagues elected not to switch the SDD regimen from one ICU to the other somewhere through their observation period, it is very difficult to ascribe differences in outcomes to the use of the SDD regimen alone. The ICU unit applying SDD already had a 10% lower rate of hospital mortality than the control ICU in the 2 years preceding the start of the study. The 95% CI of this 10% difference in mortality was 0.7–1.1. During the study, de Jonge and colleagues observed a 24% lower hospital mortality rate in the SDD-using ICU than in the other—a difference that clearly falls within this CI, indicating that the true a-priori performance of the ICU unit applying SDD might already have been much better. The similarity in baseline characteristics between the two cohorts of patients treated does not correct for the performance bias built into the design of the study. Infection and mortality rates differ greatly between various ICUs within and between hospitals– differences that cannot solely be explained by differences in the average severity of illness of patients at the time of admission.2Richards MJ Edwards JR Culver DH Gaynes RP Nosocomial infections in combined medical-surgical intensive care units in the United States.Infect Control Hosp Epidemiol. 2000; 21: 510-515Crossref PubMed Scopus (792) Google Scholar Intensive care is critically dependent on the skills of and care delivered by a heterogeneous, multidisciplinary team of experts in medicine, surgery, supporting specialties, and by specially trained nursing staff. de Jonge and colleagues do not control for the crucial influence of the ICU team on patients' outcome. Indeed, by its design, the study has added to the a-priori performance difference between the two ICUs since patients in the unit applying SDD were better observed and cared for as a consequence of the need to apply the SDD medication. Finally, de Jonge and colleagues did not properly examine the risk of the emergence of antibiotic resistance due to SDD. They took samples for systematic culture only during patients' stay in the ICU. Since application of large quantities of antimicrobial agents to mucosal surfaces will eradicate much of the aerobic microbial flora, and might well mask the selection or acquisition of resistance clones as long as SDD is given, the true risk of fostering resistance emergence should have been assessed by using special, SDD-neutralising media for culture while patients were on SDD, and by monitoring the recolonisation of the patients' digestive tracts after they were discharged from the ICU and the hospital. Although de Jonge and colleagues do not exclude the possibility that the performance differences seen between the ICUs were due to differences in care, they believe that this cannot account for the differences in outcomes. I believe it can, and would rather not have to believe one way or the other, but know for sure. Selective decontamination of digestive tract in intensive careAuthors' reply Full-Text PDF