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Ventilator-associated pneumonia due to Pseudomonas aeruginosa
S Crouch Brewer1, R G Wunderink, C B Jones
1Department of Medicine, University of Tennessee, Memphis, USA.
Objective:
Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa has been associated with higher case fatality rates than VAP caused by other bacterial etiologies. The causes of this excess mortality are unclear.
Design:
Retrospective review of 38 consecutive ventilated patients with Pseudomonas pneumonia, documented by highly reliable methods. Charts of five additional patients were unavailable for review.
Setting:
Medical ICUs of a university-affiliated Veterans Affairs Medical Center and a university-affiliated municipal hospital.
Measurements:
Prospectively collected hospital admission acute physiologic and chronic health examination (APACHE) II scores and cause of ICU admission. Retrospectively calculated organ failure and APACHE scores, VAP score. Clinical and microbiologic variables. Antibiotic treatment and outcome. Direct cause of death by standard definitions.
Results:
Overall mortality was 69% (26/38), significantly higher than the APACHE II predicted mortality of 42.6% (p=0.037). At least 38% (10/26) of deaths were directly attributable to Pseudomonas VAP. Multivariate analysis of factors associated with death found infectious cause for ICU admission (odds ratio [OR]=8.67; 95% confidence interval [CI], 0.86 to 85.94) and number of organ dysfunctions on the day of diagnosis (OR=1.73, 95% CI, 1.02 to 2.92) were significant. Septic shock from Pseudomonas VAP, septic shock from subsequent infection, and multiple organ dysfunction syndrome were the most common immediate causes of death. Mortality increased linearly with increasing APACHE III score on the day of diagnosis. Of initial antibiotic regimens, 67% (26/36) were considered failures. Persistent pneumonia occurred in 35% of patients while recurrent pneumonia was unusual (1/38).
Conclusions:
Development of Pseudomonas pneumonia results in a mortality rate in excess of that due to the presenting illness. The attributable mortality determined by several means appears to approach 40%. The excess mortality appears to be related to the host defense response to the pneumonia rather than any characteristic of the pneumonia. Even standard antibiotic regimens fail frequently and do not prevent the excess mortality. Since at least 38% of deaths can be directly attributable to the Pseudomonas pneumonia, improvement in therapy is needed.
Insights
Pseudomonas aeruginosa ventilator-associated pneumonia (VAP) leads to significantly higher mortality than predicted, with nearly 40% of deaths directly attributable to the infection. Standard treatments often fail, highlighting the need for improved therapeutic strategies.
Area of Science:
- Infectious Diseases
- Critical Care Medicine
- Pulmonary Medicine
Background:
- Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa is linked to increased mortality.
- The specific reasons for this excess mortality remain unclear.
Purpose of the Study:
- To investigate the causes of excess mortality in patients with Pseudomonas aeruginosa VAP.
- To identify factors associated with death in this patient population.
Main Methods:
- Retrospective review of 38 ventilated patients with documented Pseudomonas pneumonia.
- Collected data included APACHE II scores, organ dysfunction, clinical variables, and treatment outcomes.
- Mortality causes were analyzed using multivariate analysis.
Main Results:
- Overall mortality was 69%, significantly exceeding predicted rates.
- Approximately 38% of deaths were directly attributed to Pseudomonas VAP.
- Infectious ICU admission and increased organ dysfunction were significant predictors of mortality.
- 67% of initial antibiotic regimens failed to treat the infection effectively.
Conclusions:
- Pseudomonas VAP results in mortality beyond that of the primary illness.
- The excess mortality appears linked to the host's immune response, not solely bacterial virulence.
- Current antibiotic regimens are frequently inadequate, necessitating advancements in VAP therapy.