MIAMI BEACH — The extent of mortality due to ventilator-associated pneumonia remains uncertain, but its impact on increasing morbidity and hospital costs is clear, Dr. Robert C. Hyzy said.
“Pneumonia is bad; pneumonia kills people; so, ventilator-associated pneumonia must be bad, too, right?” Dr. Hyzy said at the annual congress. The unresolved issue is whether patients die with or die from ventilator-associated pneumonia (VAP).
There is little evidence-based medicine to make this determination. Most studies designed to assess VAP mortality are observational cohort trials.
For example, a systematic review of observational studies revealed an overall relative mortality risk of 1.27 for patients with VAP, compared with those without (Crit. Care Med. 2009;37:2709-18). “But a high degree of heterogeneity between studies limits the observation,” said Dr. Hyzy, who is an associate professor of medicine and director of the critical care medicine unit at the University of Michigan, Ann Arbor. “Ultimately, these investigators said they do not know.”
However, there are two subpopulations for which there is enough evidence to clear VAP of attributable mortality, he added.
In a subset of patients—those with acute respiratory distress syndrome (ARDS) or trauma—data were sufficiently robust to demonstrate that mechanically ventilated patients were not at increased risk of death if they developed VAP. “This makes sense—these patients are very sick to begin with,” Dr. Hyzy said.
Regarding morbidity, another study indicated that 27% of 401 patients with microbiologically proven VAP experienced recurrence of pneumonia within 28 days of onset of VAP (Crit. Care Med. 2007;35:146-54).
A 14% relapse rate and a 19% superinfection rate were other findings in that study. Dr. Hyzy noted that recurrence was more likely if patients were infected with methicillin-resistant Staphylococcus aureus (odds ratio, 2.50) or nonfermenting gram-negative bacilli (OR, 2.00).
Interestingly, recurrence did not differ significantly between patients who received 8 days vs. 15 days of antibiotic therapy.
Not surprisingly, superinfection increased length of hospital stay and costs for patients with VAP. Other researchers quantified those effects in a retrospective study of 74 patients (Semin. Respir. Crit. Care Med. 2009;30: 116-23). The researchers in that study found that median length of stay was 48 days for patients who had a superinfection, compared with 28 days for unaffected patients.
“If you stay longer, you may get superinfected, and you can get recurrence. Also, the longer you stay, the more it will cost,” Dr. Hyzy said.
Other researchers calculated that the cost attributable to VAP was $11,897.
They studied 819 mechanically ventilated patients, 127 (16%) of whom developed VAP. Total hospital costs also were significantly higher for VAP patients, $70,568, compared with non-VAP patients, $21,620 (Crit. Care Med. 2003;31:1312-7). Total costs included room, nursing, respiratory therapy, and pharmacy.
In March 2009, a health economist reported costs associated with a range of hospital-acquired infections, including approximately 52,542 VAP infections (www.cdc.gov/NCIDOD/DHQP/pdf/Scott_CostPaper.pdf
Silver-coated endotracheal tubes for mechanical ventilation of critical care patients were associated with lower rates of VAP, 4.8%, compared with traditional tubes, 7.5%, in another study (JAMA 2008;300:805-13). However, their higher cost needs to be considered, said Dr. Hyzy, a collaborator on the study.
Dr. Hyzy disclosed that he is a former consultant to Kimberly-Clark, maker of the silver-coated Microcuff Endotracheal Tube.