Cytokine levels in pleural effusions of patients under intensive care

Pleural effusions develop for various reasons in patients admitted to intensive care units (ICUs). To understand why this occurs is important, yet cytokine levels in pleural effusions have rarely been measured from a cardiovascular viewpoint.

To understand the characteristics of pleural cytokines in patients admitted to the ICU.

The subjects were 43 patients with pleural effusion who were admitted to the ICU from June 2001 through March 2006. We divided the patients into transudate (n=23) and exudate (n=20) groups. We measured levels of interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-alpha in pleural effusions and peripheral blood and evaluated their relationships with body temperature, C-reactive protein (CRP) level, and the peripheral white blood cell (WBC) count.

Levels of pleural IL-6 were significantly higher and levels of TNF-alpha tended to be higher in pleural effusions from the exudate than in those from the transudate group (3,350+/-3,627 vs. 1,677+/-1,086 pg/m and 6.6+/-3.4 vs. 4.8+/-2.6 pg/mL, respectively). However, in both groups levels of IL-10 in pleural effusions were similar to those in serum and levels of IL-6 were significantly higher in pleural effusion than in serum. Serum IL-6 levels correlated with inflammatory markers (CRP and body temperature), whereas cytokines in pleural effusion did not correlate with any of these markers (body temperature, CRP, and WBC).

Pleural levels of IL-6 were significantly higher in the exudate group than in the transudate group but did not correlate with serum levels of IL-6 or with systemic inflammatory markers. These findings suggest that pleural IL-6 levels correlate with local lung or pleural inflammation in patients admitted to the ICU.