Of interest, rh-aPC treatment lead to a more rapid resolution of respiratory failure [9]. In addition, patients with pneumonia as the source of sepsis benefited most from treatment with U0126 rh-aPC [10]. Consequently, it has been suggested that anticoagulant and anti-inflammatory effects of rh-aPC in the lungs contribute to better outcome [11,12]. In a recent study in patients with acute lung injury (ALI), systemic rh-aPC treatment did not affect ventilator-free days [13]. However, due to the low number of patients the statistical power to detect a difference in the primary endpoint was limited. Lung-protective effects of antithrombin (AT), another natural inhibitor of coagulation have been demonstrated in a relatively limited number of patients with sepsis [14].

AT did not affect mortality in patients with sepsis in a larger phase III clinical trial but no subgroup analysis on patients with pneumonia as the primary source of sepsis was performed [15]. Heparin is a potent activator of AT and has been used in several preclinical studies to prevent fibrin deposition in models of ALI [2-4]. In a recent study, continuous infusion of low-dose unfractionated heparin did not affect mortality in patients with sepsis [16], nor was mortality affected in a subgroup of patients with pneumonia. However, no subgroup analysis was performed on patients with respiratory failure or ALI/acute respiratory distress syndrome (ARDS).We recently demonstrated that systemic anticoagulant treatment attenuates pulmonary coagulopathy in pneumonia caused by Streptococcus pneumoniae in rats [1].

Intravenously administered rh-aPC, plasma-derived AT or heparin attenuated pulmonary coagulopathy. AT, but not rh-aPC and heparin, exerted significant lung-protective effects in this model. Systemically administered rh-aPC, AT and heparin also attenuated systemic coagulation, which can be considered a major drawback because of increased risks of severe bleeding. We hypothesized local treatment to be equally effective as systemic treatment in attenuating pulmonary procoagulant changes while leaving systemic coagulation unaltered. In addition, we hypothesized that there are beneficial anti-bacterial and anti-inflammatory effects of locally administered plasma-derived AT, as was seen with intravenous administration of this anticoagulant in this model.

Materials and methodsThe Institutional Animal Care and Use Committee of the Academic Medical Center approved all experiments. All animals were handled in accordance with the guidelines prescribed by the Dutch legislation and the International Guidelines on protection, care, and handling of laboratory Cilengitide animals.AnimalsPneumonia was induced in male Sprague-Dawley rats (weighing 250 to 300 g; Harlan, Horst, The Netherlands) by intratracheal instillation of 5 �� 106 colony-forming units (CFU) of S. pneumoniae (serotype 3, ATCC 6303) as described previously [1].