Interleukin-18 levels reflect the long-term prognosis of acute lung injury and acute respiratory distress syndrome

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. 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)-alpha were measured by enzyme-linked immunosorbent assays. The ARDS group showed significantly higher serum levels of IL-18, IL-12, and TNF-alpha even at an early stage after disease onset compared with the ALI group. A negative correlation was noted between the PaO2/FIO2 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-alpha were significantly higher in the non-survivors at 60 and 90 days, but not at 30 days, than in the corresponding survivors. 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-alpha levels appear to reflect the > 60-day prognosis in patients with ALI/ARDS.