The present thesis describes the incidence and risk factors for pneumonia and especially
ventilator-associated pneumonia (VAP) among Intensive Care Unit (ICU) patients.
Bacteria in samples from the lower respiratory tract of patients receiving mechanical
ventilation are reported, including the duration of treatment prior to the first occurrence
of different pathogens. The frequency of VAP using Swedish criteria (Swedish
Intensive Registry, SIR) was compared with the VAP rate measured with international
criteria (US Centre for Disease Control, CDC).
Data were extracted from a local infection surveillance database (paper I-IV) and a
trauma registry (paper II). In Paper I the incidence and risk factors for pneumonia and
associated death over a two-year period was studied in 221 patients on mechanical
ventilation. In paper II pre-hospital and hospital parameters associated with pneumonia
within 10 days of ICU admission were evaluated in 322 ICU-treated trauma patients.
Paper III focus on 443 bacterial isolates from the lower respiratory tract of 346
mechanically ventilated ICU patients. The occurrence of different pathogens was
correlated with duration of hospital stay and time on mechanical ventilation at the time
of sampling. In paper IV patients with (n=112) and without (n=224) a new lung
infiltrate after ≥48 hours of mechanical ventilation were studied to evaluate the
proportion of patients meeting different criteria used to define VAP according to CDC
and SIR, respectively. Paper I shows that 15% of patients developed VAP,
corresponding to a rate of 29 VAP/1000 ventilator days. Risk factors were aspiration,
recent surgery and trauma. The 28-day mortality in patients with VAP was 33% as
compared to 16% in those without ICU-acquired pneumonia. In Paper II risk factors for
pneumonia were intubation at the site of injury, shock, an initial Glasgow Coma Scale
(GCS) of ≤8, major surgery within 24 h of admission to hospital, massive transfusion
of blood and ISS > 24. Enterobacteriacae and Stafylocoocus aureus were the most
common pathogens. Paper III shows that duration of hospital care and mechanical
ventilation prior to sampling was ≤2 days for Streptococcus pneumoniae, betastreptococci
and Haemophilus influenzae. With the exception of Stenotrophomonas
maltophilia and Pseudomonas aeruginosa, the median duration of time on mechanical
ventilation was short and similar for most bacteria. In samples taken on the first day of
mechanical ventilation, the rate of pathogens expected to be resistant to cefotaxime was
23%. In Paper IV the SIR and CDC criteria for VAP was met in 84% and 93%,
respectively, in 112 situations with a new infiltrate when applying a ± 48 hours time
frame for the other criteria in relation to the occurrence of the lung infiltrate.
It is concluded that VAP is a common complication in the ICU, especially among
trauma patients. The most important risk factor for VAP in a general ICU patient is
aspiration and for a trauma patient an initial GCS of <8. Staphylococcus aureus and
Enterobacteriacae are the most common bacteria in samples from the lower respiratory
tract in both general ICU patients and in a trauma population. Occurrence of pathogens
resistant to common antibiotics increases with the duration of hospital care and
mechanical ventilation. The diagnosis of VAP should rely on presence of lung infiltrate
and microbiological samples from the lower respiratory tract; clinical criteria add little
value
