THE SYSTEMIC INFLAMMATORY RESPONSE IN THE DEVELOPMENT OF VENTILATOR-ASSOCIATED PNEUMONIA

Ventilator-associated pneumonia (VAP) is the most frequent occurring i nfection among mechanically ventilated patients. The clinical presenta tion of VAP ranges from relatively benign to a severe illness with sep tic shock. The influence of VAP on patient outcome has not been elucid ated and its effects on the inflammatory response of the host are unkn own. In a case-control study, the systemic inflammatory response was i nvestigated in patients developing VAP as compared with control patien ts matched on duration of mechanical ventilation and underlying diseas es. Patients developing VAP (n = 42) were matched to a single control (without VAP), who was matched on seven variables. VAP was diagnosed w ith bronchoscopic techniques. The inflammatory response, reflected by circulating levels of interleukin-6 (IL-6) and interleukin-8 (IL-8), w as determined on the day of diagnosis (or day of matching for controls ), 4 and 2 d before diagnosis, and 2 d after diagnosis. The developmen t of VAP was not associated with an increase in circulating levels of IL-6 or IL-8. Among patients in which VAP was associated with a clinic al presentation of severe sepsis or septic shock (n = 10), IL-6 and IL -8 levels increased and were higher than in the corresponding controls . Moreover, 60% of cases with severe sepsis or septic shock died as co mpared with 20% of their matched controls (p = 0.06). Mortality rates were similar in patients with uncomplicated VAP and their matched cont rols (25% and 34%, respectively). High circulating levels of IL-6 and IL-8 were associated with higher mortality rates. The clinical picture of VAP can be subdivided into different types, ranging from uncomplic ated to an infection associated with severe sepsis or septic shock, el evated circulating levels of IL-6 and IL-8, and an increased mortality rate.