Estimating the attributable mortality of ventilator-associated pneumonia from randomized prevention studies*

OBJECTIVE: To assess the attributable mortality of ventilator-associated pneumonia using results from randomized controlled trials on ventilator-associated pneumonia prevention. DATA SOURCES: A systematic search was performed in PubMed, Embase, Web of Science, and Cochrane Library from their inception until July 2010. In addition, a reference and related article search was performed. STUDY SELECTION: Randomized ventilator-associated pneumonia prevention studies in which all patients were mechanically ventilated and from which ventilator-associated pneumonia and mortality rates of intervention and control group could be extracted were included. DATA EXTRACTION/SYNTHESIS: Fifty-three papers were identified describing 58 comparisons. Statistical significant reductions in ventilator-associated pneumonia incidences were reported in 20 of the 58 comparisons, whereas none of these trials reported a significant reduction of mortality. Pooled estimates of the relative risk reductions of both ventilator-associated pneumonia and mortality were calculated and the attributable mortality was estimated as the ratio between the relative risk reductions of mortality and ventilator-associated pneumonia. Effects of study quality, diagnostic methods used, and effectiveness of preventing ventilator-associated pneumonia on the mortality rate of ventilator-associated pneumonia were assessed in subgroup analyses. The overall attributable mortality of ventilator-associated pneumonia was estimated as 9%. In subgroup analyses, the attributable mortality varied between 3% and 17%. CONCLUSION: Based on the results of 58 randomized studies on ventilator-associated pneumonia prevention, the attributable mortality rate of ventilator-associated pneumonia was estimated to be 9% and ranged between 3% and 17% in subgroup analyses. Together with the results of other recent studies, there is cumulative evidence that the attributable mortality resulting from ventilator-associated pneumonia is approximately 10%.