Incidence of and risk factors for ventilator-associated pneumonia in critically ill patients.
BACKGROUND
Understanding the risk factors for ventilator-associated pneumonia can help to assess prognosis and devise and test preventive strategies.


OBJECTIVE
To examine the baseline and time-dependent risk factors for ventilator-associated pneumonia and to determine the conditional probability and cumulative risk over the duration of stay in the intensive care unit.


METHODS
Prospective cohort study.


METHODS
16 intensive care units in Canada.


METHODS
1014 mechanically ventilated patients.


METHODS
Demographic and time-dependent variables reflecting illness severity, ventilation, nutrition, and drug exposure. Pneumonia was classified by using five methods: adjudication committee, bedside clinician's diagnosis, Centers for Disease Control and Prevention definition, Clinical Pulmonary Infection score, and positive culture from bronchoalveolar lavage or protected specimen brush.


RESULTS
177 of 1014 patients (17.5%) developed ventilator-associated pneumonia 9.0 +/- 5.9 days (median, 7 days [interquartile range, 5 to 10 days]) after admission to the intensive care unit. Although the cumulative risk increased over time, the daily hazard rate decreased after day 5 (3.3% at day 5, 2.3% at day 10, and 1.3% at day 15). Independent predictors of ventilator-associated pneumonia in multivariable analysis were a primary admitting diagnosis of burns (risk ratio, 5.09 [95% CI, 1.52 to 17.03]), trauma (risk ratio, 5.00 [CI, 1.91 to 13.11]), central nervous system disease (risk ratio, 3.40 [CI, 1.31 to 8.81]), respiratory disease (risk ratio, 2.79 [CI, 1.04 to 7.51]), cardiac disease (risk ratio, 2.72 [CI, 1.05 to 7.01]), mechanical ventilation in the previous 24 hours (risk ratio, 2.28 [CI, 1.11 to 4.68]), witnessed aspiration (risk ratio, 3.25 [CI, 1.62 to 6.50]), and paralytic agents (risk ratio, 1.57 [CI, 1.03 to 2.39]). Exposure to antibiotics conferred protection (risk ratio, 0.37 [CI, 0.27 to 0.51]). Independent risk factors were the same regardless of the pneumonia definition used.


CONCLUSIONS
The daily risk for pneumonia decreases with increasing duration of stay in the intensive care unit. Witnessed aspiration and exposure to paralytic agents are potentially modifiable independent risk factors. Exposure to antibiotics was associated with low rates of early ventilator-associated pneumonia, but this effect attenuates over time.
Cook
D J
DJ
McMaster University, Hamilton, Ontario, Canada. debcook@fhs.csu.mcmaster.ca
Walter
S D
SD
Cook
R J
RJ
Griffith
L E
LE
Guyatt
G H
GH
Leasa
D
D
Jaeschke
R Z
RZ
Brun-Buisson
C
C
D000328:Adult; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D016638:Critical Illness / Q000628:therapy*; D003428:Cross Infection / Q000453:epidemiology / Q000209:etiology; D005260:Female; D006801:Humans; D015994:Incidence; D007362:Intensive Care Units; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011014:Pneumonia / Q000453:epidemiology / Q000209:etiology*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000009:adverse effects*; D012307:Risk Factors; D012720:Severity of Illness Index
D000900:Anti-Bacterial Agents