BACKGROUND: Although one-lung ventilation (OLV) has become an established procedure during thoracic surgery, sparse data exist about inflammatory alterations in the deflated, reventilated lung. The aim of this study was to prospectively investigate the effect of OLV on the pulmonary inflammatory response and to assess possible immunomodulatory effects of the anesthetics propofol and sevoflurane. METHODS: Fifty-four adults undergoing thoracic surgery with OLV were randomly assigned to receive either anesthesia with intravenously applied propofol or the volatile anesthetic sevoflurane. A bronchoalveolar lavage was performed before and after OLV on the lung side undergoing surgery. Inflammatory mediators (tumor necrosis factor alpha, interleukin 1beta, interleukin 6, interleukin 8, monocyte chemoattractant protein 1) and cells were analyzed in lavage fluid as the primary endpoint. The clinical outcome determined by postoperative adverse events was assessed as the secondary endpoint. RESULTS: The increase of inflammatory mediators on OLV was significantly less pronounced in the sevoflurane group. No difference in neutrophil recruitment was found between the groups. A positive correlation between neutrophils and mediators was demonstrated in the propofol group, whereas this correlation was missing in the sevoflurane group. The number of composite adverse events was significantly lower in the sevoflurane group. CONCLUSIONS: This prospective, randomized clinical study suggests an immunomodulatory role for the volatile anesthetic sevoflurane in patients undergoing OLV for thoracic surgery with significant reduction of inflammatory mediators and a significantly better clinical outcome (defined by postoperative adverse events) during sevoflurane anesthesia.