Disaggregating the Benefits of Ventilator Bundle Components

There is a very nice study by Michael Klompas and colleagues in September's JAMA Internal Medicine. The team sought to disentangle the benefits or harms of the individual components of current ventilator bundles including: head-of-bed elevation, sedative infusion interruptions, spontaneous breathing trials, thromboprophylaxis, stress ulcer prophylaxis, and oral care with chlorhexidine.

Prior studies had found potential harm associated with stress ulcer prophylaxis (pneumonia) and oral chlorhexidine (higher mortality). This same group published a meta-analysis that called into question the benefits of routine oral care with chlorhexidine (CHG) in ventilated patients. For this retrospective cohort, they examined the associations between exposure to individual ventilator bundle components on a day-by-day basis and ventilator-associated events (VAEs), duration of mechanical ventilation, ventilator mortality, hospital length of stay, and hospital mortality.

The cohort included 5539 consecutive patients who were exposed to mechanical ventilation for at least 3 days. They measured the association between individual process measures and VAEs using Cox proportional hazards regression models with fixed and time-varying covariates and censored patients on extubation or death, whichever came first. Interestingly, they calculated hazard ratios for each bundle component "as the contrast between 4 days of continually performing the process measure vs 4 days of not doing so", since they wanted to allow for the possibility that process measures might have an immediate or delayed effect on each outcome.

I have included the patient-outcomes table below. The most interesting finding, among many tested associations, was that oral care with chlorhexidine was associated with an increased risk for ventilator mortality (HR, 1.63; 95% CI, 1.15-2.31; P = .006). In another table, they reported that stress ulcer prophylaxis was associated with an increased risk for possible ventilator-associated pneumonia (HR, 7.69; 95% CI, 1.44-41.10; P = .02).

This was a very thoughtfully completed and written study - I encourage you to read it (and the accompanying invited editorial) beyond my quick overview. The authors concluded: "we should revisit the classic ventilator bundle. Possible revisions include... a reappraisal of whether oral care protocols should be revised to exclude chlorhexidine therapy, and the reservation of stress ulcer prophylaxis for patients at marked and immediate risk for upper gastrointestinal tract bleeding rather than prescribing them for all patients undergoing ventilation."  It will be interesting to see how slowly these recommended changes occur...