NEW YORK (Reuters Health) – Ventilator-associated pneumonia is less likely to be fatal when patients are intubated with a silver-coated endotracheal tube, according to a post hoc analysis of a randomized trial.

But in patients who don’t develop ventilator-associated pneumonia, mortality is higher with the silver-coated tube, the researchers report in an article prepublished online in Chest on December 28.

Lead author Dr. Bekele Afessa, from the Mayo Clinic in Rochester, Minnesota, and colleagues explain that the original study involved 1509 patients intubated for at least 24 hours with either the silver-coated tube or a standard tube.

In the primary analysis, the silver-coated tube reduced the incidence of ventilator-associated pneumonia and delayed the onset compared with an uncoated endotracheal tube, but it had no impact on survival. Specifically, microbiologically confirmed ventilator-associated pneumonia developed in 37 of 766 patients (4.8%) in the study group and in 56 of 743 (7.5%) controls.

But in the secondary analysis, when the researchers looked only at patients who did develop pneumonia, the rate of death during hospitalization was 14% with the silver tube versus 36% with the standard tube (p = 0.03).

Furthermore, among pneumonia patients whose initial antibiotic therapy met professional guidelines, the in-hospital mortality rate was 6% in the silver group and 34% in controls (p = 0.005).

When pneumonia developed, treatment group was a predictor of mortality, with an odds ratio on multivariate analysis of 0.28 for the silver tube versus the standard tube.

However, among patients who did not develop pneumonia, hospital mortality was significantly higher in the study group than in controls (31% versus 26%; p = 0.03).

Although their analyses cannot prove cause-and-effect relationships, Dr. Afessa and associates theorize that the lower mortality rate in patients with ventilator-associated pneumonia may be related to the antimicrobial effect of silver.

The investigators note that their subgroup analyses are exploratory and conclude that more studies are needed to confirm their results.

This study was supported by a grant from C.R. Bard, Inc., which developed the silver-coated endotracheal tube and markets it as the Agento I.C. Endotracheal Tube.

Reference:
Chest 2009.