Silver-coated endotracheal tubes (ETTs) for prevention of ventilator-associated pneumonia in critically ill people

Review question

We reviewed the evidence of whether silver-coated endotracheal tubes (ETTs) are effective in reducing the risk of ventilator-associated pneumonia (VAP) and hospital mortality in comparison with standard non-coated ETTs in people who require mechanical ventilation for 24 hours or longer.

Background

Mechanical ventilation is used to help people breathe when they are very ill and find it difficult to breath on their own. An endotracheal tube is a disposable tube that is inserted into the person's windpipe to allow mechanical ventilation. In mechanical ventilation a machine is used to replace the natural spontaneous breathing and allows air in and out of the lungs. When used for a long period, mechanical ventilation can cause problems for the patient. Mechanical ventilation is associated with complications. Silver is an antimicrobial agent (an agent that kills bacteria) that has been used for many centuries to treat and prevent infections. Silver coating around the ETTs could prevent VAP because of its antimicrobial activity.

Study characteristics

We found three randomized controlled trials involving 2081 participants. No outcome data were available for one included study. The design of the other two RCTs was generally good, although there were some weaknesses. The majority of participants were included in centres around North America. The evidence is current to October 2014. Both RCTs were funded but stated that the sponsors contributed only to the study design and did not participate in the conduct of the study.

Key results

We found that silver-coated ETT reduced the risk for developing VAP from 6.7% to 3.5% within 10 days of intubation compared with non-coated ETT in people who required mechanical ventilation for 24 hours of longer, although the quality of evidence for this outcome was low. One study showed that an initial VAP occurrence appeared much later in time in people who had a silver-coated ETT compared with a non-coated ETT, although again the evidence was low quality. We could not draw conclusions about hospital mortality, device-related complications, duration of intubation, and length of hospital and intensive care unit stay owing to uncertainty of the effects. We found no clinical studies evaluating the cost-effectiveness of silver-coated ETTs.

Quality of the evidence

The overall quality of evidence was low for all interested outcomes mentioned.

Conclusion

Limited evidence suggests that silver-coated ETT seems to be an effective device in reducing the risk of VAP, although data for our other key outcome of hospital mortality were inconclusive. Larger studies with more participants who are at risk for VAP and who require mechanical ventilation for a longer period of time are needed.

Authors' conclusions: 

This review provides limited evidence that silver-coated ETT reduces the risk of VAP, especially during the first 10 days of mechanical ventilation.

Read the full abstract...
Background: 

Ventilator-associated pneumonia (VAP) is one of the most common nosocomial infections in intubated and mechanically ventilated patients. Endotracheal tubes (ETTs) appear to be an independent risk factor for VAP. Silver-coated ETTs slowly release silver cations. It is these silver ions that appear to have a strong antimicrobial effect. Because of this antimicrobial effect of silver, silver-coated ETTs could be an effective intervention to prevent VAP in people who require mechanical ventilation for 24 hours or longer.

Objectives: 

Our primary objective was to investigate whether silver-coated ETTs are effective in reducing the risk of VAP and hospital mortality in comparison with standard non-coated ETTs in people who require mechanical ventilation for 24 hours or longer. Our secondary objective was to ascertain whether silver-coated ETTs are effective in reducing the following clinical outcomes: device-related adverse events, duration of intubation, length of hospital and intensive care unit (ICU) stay, costs, and time to VAP onset.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014 Issue 10, MEDLINE, EMBASE, EBSCO CINAHL, and reference lists of trials. We contacted corresponding authors for additional information and unpublished studies. We did not impose any restrictions on the basis of date of publication or language. The date of the last search was October 2014.

Selection criteria: 

We included all randomized controlled trials (RCTs) and quasi-randomized trials that evaluated the effects of silver-coated ETTs or a combination of silver with any antimicrobial-coated ETTs with standard non-coated ETTs or with other antimicrobial-coated ETTs in critically ill people who required mechanical ventilation for 24 hours or longer. We also included studies that evaluated the cost-effectiveness of silver-coated ETTs or a combination of silver with any antimicrobial-coated ETTs.

Data collection and analysis: 

Two review authors (GT, HV) independently extracted the data and summarized study details from all included studies using the specially designed data extraction form. We used standard methodological procedures expected by The Cochrane Collaboration. We performed meta-analysis for outcomes when possible.

Main results: 

We found three eligible randomized controlled trials, with a total of 2081 participants. One of the three included studies did not mention the amount of participants and presented no outcome data. The 'Risk of bias' assessment indicated that there was a high risk of detection bias owing to lack of blinding of outcomes assessors, but we assessed all other domains to be at low risk of bias. Trial design and conduct were generally adequate, with the most common areas of weakness in blinding. The majority of participants were included in centres across North America. The mean age of participants ranged from 61 to 64 years, and the mean duration of intubation was between 3.2 and 7.7 days. One trial comparing silver-coated ETTs versus non-coated ETTs showed a statistically significant decrease in VAP in favour of the silver-coated ETT (1 RCT, 1509 participants; 4.8% versus 7.5%, risk ratio (RR) 0.64, 95% confidence interval (CI) 0.43 to 0.96; number needed to treat for an additional beneficial outcome (NNTB) = 37; low-quality evidence). The risk of VAP within 10 days of intubation was significantly lower with the silver-coated ETTs compared with non-coated ETTs (1 RCT, 1509 participants; 3.5% versus 6.7%, RR 0.51, 95% CI 0.31 to 0.82; NNTB = 32; low-quality evidence). Silver-coated ETT was associated with delayed time to VAP occurrence compared with non-coated ETT (1 RCT, 1509 participants; hazard ratio 0.55, 95% CI 0.37 to 0.84). The confidence intervals for the results of the following outcomes did not exclude potentially important differences with either treatment. There were no statistically significant differences between groups in hospital mortality (1 RCT, 1509 participants; 30.4% versus 26.6%, RR 1.09, 95% CI 0.93 to 1.29; low-quality evidence); device-related adverse events (2 RCTs, 2081 participants; RR 0.65, 95% CI 0.37 to 1.16; low-quality evidence); duration of intubation; and length of hospital and ICU stay. We found no clinical studies evaluating the cost-effectiveness of silver-coated ETTs.

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