PLASMA-LEVELS OF TUMOR-NECROSIS-FACTOR IN THE ADULT RESPIRATORY-DISTRESS SYNDROME

The purpose of the study was to evaluate the role of tumor necrosis factor alpha (TNF-alpha) in the pathogenesis of acute lung injury in critically ill patients. An immunoradiometric assay with an upper normal limit of 9 pg/ml was used to measure plasma TNF-alpha levels (pl-TNF-alpha) in 34 patients with adult respiratory distress syndrome (ARDS) and in 16 patients in whom, despite the presence of risk factors, ARDS did not develop. Pl-TNF-alpha was elevated in 76% of the patients with ARDS (71 +/- 104 pg/ml) and in 48% of the at-risk patients (47 +/- 73 pg/ml); the difference between the two groups was not statistically significant. In 13 patients studied serially from the onset (Day 0) to the fifth day of ARDS, the peak pl-TNF-alpha occurred later than Day 0 in seven subjects. Although the highest pl-TNF-alpha levels were found in septic patients, moderately elevated values were also observed in 56% of nonseptic subjects. We conclude that plasma TNF-alpha level is not a marker of ARDS but rather of shock and sepsis. These results do not exclude a pathogenic role of TNF-alpha in acute lung injury since this cytokine could be produced and exert its effects within the lungs. The large incidence of abnormally high plasma TNF-alpha levels raises important questions on the role of this toxic cytokine in other disorders occurring in critically ill patients.