Purpose: The purpose of this study was to investigate the relationship between the blood levels of interleukin (IL)-18 measured in the early stage of acute respiratory failure and the prognosis for patient survival.
Methods: The study subjects were 38 patients with acute respiratory failure treated at our institution during the 4-year period from April 2004 to March 2008. The underlying clinical condition was defined as acute respiratory distress syndrome (ARDS; n = 12) or acute lung injury (ALI; n = 26). The serum levels of interleukin (IL)-18, IL-12, and tumor necrosis factor (TNF)-α were measured by enzyme-linked immunosorbent assays.
Results: The ARDS group showed significantly higher serum levels of IL-18, IL-12, and TNF-α even at an early stage after disease onset compared with the ALI group. A negative correlation was noted between the PaO(2)/FIO(2) ratio (P/F ratio) and serum IL-18 level. Analysis of all 38 patients with ALI/ARDS revealed a 30-day mortality rate of 7.9 %, 60-day mortality rate of 15.8 %, and 90-day mortality rate of 18.4 %. The early-stage serum levels of IL-18, IL-12, and TNF-α were significantly higher in the non-survivors at 60 and 90 days, but not at 30 days, than in the corresponding survivors.
Conclusion: The present data demonstrate an inverse correlation between serum IL-18 level and the P/F ratio, suggesting the possible involvement of IL-18 in the pathogenesis of respiratory failure in patients with ALI/ARDS. Early-stage serum IL-18, IL-12, and TNF-α levels appear to reflect the >60-day prognosis in patients with ALI/ARDS.