Tamar F. Barlam, M.D.; Dennis L. Kasper, M.D.
AccessMedicine from McGraw-Hill. 2008; ©2008 The McGraw-Hill Companies – Posted 01/12/2009
Ventilator-associated pneumonia (VAP) is a major nosocomial infection that results in significant morbidity, mortality, and health care costs. Most strategies to reduce VAP attempt to decrease rates of colonization of the aerodigestive tract and aspiration of infected secretions. Silver has antimicrobial properties in vitro and may reduce biofilm formation on and bacterial adherence to the endotracheal tube. Kollef and colleagues (2008) conducted a prospective, randomized, multicenter, single-blind, controlled study in patients requiring >24 h of intubation to determine whether silver-coated endotracheal tubes can reduce the incidence of microbiologically confirmed VAP.
Patients recruited from December 2002 to March 2006 at 54 centers in North America were assigned to treatment groups in a 1:1 ratio, using block randomization by site. Each patient was intubated with either the experimental silver-coated tube or a control tube (Hi-Lo endotracheal tube; Mallinckrodt, St. Louis). Apart from the silver coating, the two types of tubes were similar. Bronchoalveolar lavage (BAL) fluid was subjected to quantitative culture if VAP was suspected. The primary outcome was VAP incidence, which was defined as a quantitative BAL fluid culture with ≥104 colony-forming units (CFU)/mL after intubation for ≥24 h. Secondary outcomes were time to occurrence of VAP; duration of endotracheal intubation, intensive care unit (ICU) stay, and hospital stay; and mortality rate.
Of 2003 patients randomized, 968 received the experimental tube and 964 received the control tube; 423 patients were intubated for <24 h. After randomization, a history of chronic obstructive pulmonary disease (COPD) was more common in the control group than in the experimental group (16.4% vs 11.6%; p = .007). The primary outcome of VAP was more common in the control group (7.5%; 95% CI, 5.7-9.7%) than in the silver coated-tube group (4.8%; 95% CI, 3.4-6.6%) (p = .03). The relative risk reduction in VAP incidence was 35.9% (95% CI, 3.6-69%). Of 264 patients with suspected VAP, 220 underwent BAL; >90% of these patients were taking antibiotics at the time of BAL. Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacteriaceae were the most common pathogens. In patients with silver-coated tubes, the relative risk of VAP incidence within 10 days of intubation was reduced and the occurrence of VAP was delayed (p = .005) in comparison with the control group; however, other secondary outcomes—mortality rate and duration of intubation, ICU stay, or hospital stay—did not differ between the two groups. The frequency and severity of adverse events were similar for the two types of endotracheal tubes.
The authors conclude that, compared with the uncoated tube, the silver-coated endotracheal tube is associated with a significant reduction in the incidence of VAP and a delay in VAP occurrence. They note that the silver-coated tube offers a unique approach to VAP prevention because it is user-independent after intubation and requires no further action on the part of the clinician. In an accompanying editorial, Chastre (2008) discusses the limitations of the study and the lack of robustness of the results. Only three more cases of VAP in the coated-tube group would have rendered the study statistically inconclusive. In addition, BAL culture results were probably affected by antibiotic use, which was not further described in the study, and the greater proportion of patients with COPD in the control group could have biased the results. Thus, although the silver-coated endotracheal tube may be appropriate for patients at very high risk of developing early-onset VAP (e.g., trauma patients), its use should not be viewed as definitively beneficial for VAP prevention until further data confirm its efficacy and cost benefit.
* Chastre J: Preventing ventilator-associated pneumonia: Could silver-coated endotracheal tubes be the answer? (editorial) JAMA 300:842, 2008
* Kollef MH et al: Silver-coated endotracheal tubes and incidence of ventilator-associated pneumonia: The NASCENT randomized trial. JAMA 300:805, 2008
Tamar F. Barlam, M.D., Associate Professor of Medicine, Boston University School of Medicine, Boston.
Dennis L. Kasper, M.D., William Ellery Channing Professor of Medicine, Professor of Microbiology and Molecular Genetics, Harvard Medical School; Director, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital, Boston.