Antibiotics for preventing respiratory tract infections in adults receiving intensive care.

BACKGROUND: Pneumonia is an important cause of mortality in intensive care units. The incidence of pneumonia in such patients ranges between 7% and 40%, and the crude mortality from ventilator associated pneumonia may exceed 50%. Although not all deaths in patients with this form of pneumonia are directly attributable to infections, it has been shown to contribute to mortality in intensive care units independently of other factors that are also strongly associated with such deaths.

OBJECTIVES: The objective of this review was to assess the effects of antibiotics for preventing respiratory tract infections and overall mortality in adults receiving intensive care.

SEARCH STRATEGY: We searched Medline, the Cochrane Acute Respiratory Infections Group trials register, proceedings of scientific meetings and reference lists of articles from January 1984 to December 1999. We also contacted investigators in the field.

SELECTION CRITERIA: Randomised trials of antibiotic prophylaxis for respiratory tract infections and deaths among adult intensive care unit patients.

DATA COLLECTION AND ANALYSIS: Investigators were contacted for additional information. At least two reviewers independently extracted data and assessed trial quality.

MAIN RESULTS: Overall 33 trials involving 5727 people were included. There was variation in the antibiotics used, patient characteristics and risk of respiratory tract infections and mortality in the control groups. In 16 trials (involving 3361 patients) that tested a combination of topical and systemic antibiotic, the average rates of respiratory tract infections and deaths in the control group were 36% and 30% respectively. There was a significant reduction of both respiratory tract infections (odds ratio 0.35, 95% confidence interval 0.29 to 0.41) and total mortality (odds ratio 0.80, 95% confidence interval 0.69 to 0.93) in the treated group. On average 5 patients needed to be treated to prevent one infection and 23 patients to prevent one death. In 17 trials (involving 2366 patients) that tested topical antimicrobials the rates of respiratory tract infections and deaths in the control groups were 28% and 26% respectively. There was a significant reduction of respiratory tract infections (odds ratio 0.56, 95% confidence interval 0.46 to 0.68) but not in total mortality (odds ratio 1.01, 95% confidence interval 0.84 to 1.22) in the treated group.

REVIEWER'S CONCLUSIONS: A combination of topical and systemic prophylactic antibiotics can reduce respiratory tract infections and overall mortality in adult patients receiving intensive care. The design of the trials included in this systematic review does not allow to assess whether or not the treatment leads to antimicrobial resistance. Trials with different design are warranted to reliably address this question.